# eXStata DIY Electrostatic Amp for Intermediate DIYers



## runeight

Folks, I believe we have arrived. 
	

	
	
		
		

		
			





 This thread is a continuation of this thread:

A DIY Electrostatic amp

 started by ericj. Ericj was looking for a reasonably priced, easy to build DIY electrostatic amp that is within reach of diyers who have or want to move to electrostatic headphones.

 I did a quick and dirty design on that thread, but this design was only marginal. While we were testing this verion out my consulting practice went haywire for a few months. A good thing as it turned out because while I couldn't work on any electronics for a while this project kept percolating in the back of my mind. The prototype team was remarkably patient during this gap. I want to thank them for their patience.

 When I was able to get back to the project a whole new design had evolved along with a new PS. Both designs were much simpler and were straightforward enough to ensure that properly built boards would work without difficulties. The whole design philosophy was "simple but good."

 Once again the proto team consisting of ericj, pabbi1, sachu, wiatrob, and me started stuffing boards. And now there are five of these amps working and driving headphones.

 We've called it the *eXStatA *and there are two versions: an all SS version and a tube hybrid that uses 6S4s. The tube version is going into prototyping now.

 The same PS will supply either board and the sand and hybrid amp boards (both channels on one board) are the same size with the same mounting holes so you can swap one for the other in a working amp.

 A few particulars for now.

 1. The rail voltage is +/-300. This number was chosen so that you can use easy-to-get, inexpensive transformers. There is a Hammond transformer and a Triad transformer that fits. The Hammond has the heater winding for the tube version.

 2. The PS has two bias supplies: an HV supply that is adjustable from about 340V to about 680V and an LV supply that is adjustable from about 170V to 340V.

 3. The boards are: 150mm x 95mm (two channel amp) and 100mm x 100mm (PS including bias supplies).

 4. The maximum peak to peak voltage is about 700-800V. This is good enough for many, many situations. Remember that this amp is targeted at intermediate builders.

 5. The gain is approximately 1000 give or take some.

 6. Balanced or SE input (Edit)

 7. The amp is fully DC coupled. No capacitor bass rolloff. In fact the amps have no caps at all in them (Edit)

 I think we have met or exceeded the original set of design goals.

 The prototypers have been chomping at the bit to post impressions and pics. But, we have waited until all five amps and PSs were successfully built and listened to.

 We're going to burn these amps for a while longer just to be sure that their are no problems with use. HV is a different animal from the LV amps that most people build.

 I don't have pics because my boards are off with wiatrob getting ready for RMAF. But the other guys should be posting soon.

 Thanks for your patience during the gap. We're back.


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## Pars

Congrats! I'll be interested to see this... hmm, electrostats? Oh wifey.... heh


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## pabbi1

And, chomping at the bit to give impressions... but, first, some eye candy:











 As almost everyone knows, I am a tube guy - just basic coding in my DNA. But, we had to go SS first to proof the design, and that is where we are. 

 My first disclaimer is that I do not have any other stat amps (operational) with which to compare. Perhaps soon. All my impressions to date are with the he60, and limited with the SR-40 electrets.

 First impressions are simple: Plenty of gain (I can't get past about 1 o'clock) even as insensitive as my ears have become. This is a fast amp, which really opend up not only the upper range, but also the soundstage. There is plenty of air, precise imaging, and, oh yeah, bass. 

 Bear in mind the team has at most 100 hours on these units, most with less than half that. Even so, the amp is very stable with 1v offsets all around, and stable (adjustable) bias.

 Ongoing listening and burnin, but, for $325 ish in parts (NOTHING boutique), this amp is a no brainer. I will have both the SS and tube versions in Houston for a meet on Oct 17th, so I'll get additional comments then.

 One thing that is a little different about this amp is that it is, well, FUN - like a brassy blonde, but not obnoxiously so. 

 This is the DIY stat amp for intermediate builders that won't require a serious investment in parts, and is as simple to case as any of Alex's dynamic amps, which really sets this apart from most stat amps.

 Comparative impressions will be fothcoming in a few weeks. For now, just know it exists, it sounds quite nice, and will be available soon.


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## les_garten

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_And, chomping at the bit to give impressions... but, first, some eye candy:








 <<SNIP>>._

 

Putting it in a SUN drive box "classes" it up a few notches! Nice Job. Would love to see it "race" against the conventional big iron out there.

 .


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## sachu

Some quick impressions on the amp...
 Definitely better than the SRM1 Mk-2 that I have. There is a lot more air ..wider soundstage. Truly brings to the fore that my ESP950 is not really "dark".
 I love the bass it has but i would want a little more with the ESP950, the instruments seem to have air around them making it feel forward compared to the SRM1-MK2.

 I am using a PEC carbon pot and vampire like jacks for the inputs .

 The case was chosen to be cost efficient and in keeping with the extreme poormans concept. But I will spruce it up with powdercoating, redo the rear panel for the jacks and add a custom top plate once everything is in its place.

 That means having the tube boards as well in the same chassis and with 3 outputs (one low bias, one pro at 580 and one pro at 650 volts).

 Best compliment I can give it is that since its arrival the EHHA has taken a back seat and hasn't seen use in a week now. 
	

	
	
		
		

		
		
	


	






 Another pic





 Congrats to Alex for answering the call, Ericj for starting this journey out with his challenge. Also kudos to wiatrob for putting together such a fantastic easy to follow BOM.


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## les_garten

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_

_

 

You guys are making me rethink some stuff I have sitting in the Garage. Some of it SUN or SUN clones by the way!


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## pabbi1

Just throwing out some casing ideas... but, here is my tube case version.






 Rosewood front panel, limoncillo back and sides, with walnut feet - just scraps I had laying around the garage.


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## wiatrob

I actually have two amps working on the bench and am feverishly working on casing - they will be at RMAF Saturday and Sunday - I will not be able to attend Friday (stupid day job).

 If all goes well - one of those may be the tube version, fingers crossed...


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## wiatrob

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Just throwing out some casing ideas... but, here is my tube case version.


 Rosewood front panel, limoncillo back and sides, with walnut feet - just scraps I had laying around the garage._

 


 You've been holding out! Wonder how you'll get the board to line up under that tube ring


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## dBel84

nice scraps Pabbi, and well done all round. 

 This may be the final push that sends me flailing into the stat world 
	

	
	
		
		

		
		
	


	




 ..dB


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## ericj

I'd post pictures of my amp, but it's a bit naked as i was the last to complete a build and i haven't gotten it into an enclosure yet. 

 I don't have any other amps to compare it to either - just the SRD-7 transformer box, and i have to say it compares very well. 

 I agree completely that this is a very lively amp - not shy or reserved at all.


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## DoYouRight

this is very sweet. Any bom lists? or more details L)


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## HeadphoneAddict

Cool! I look forward to trying it out at RMAF this weekend.

 If I got one I would want balanced XLR inputs and 6S4 tubes - is that the standard configuration, or is RCA inputs the standard?


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## HeadphoneAddict

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I actually have two amps working on the bench and am feverishly working on casing - they will be at RMAF Saturday and Sunday - I will not be able to attend Friday (stupid day job).

 If all goes well - one of those may be the tube version, fingers crossed..._

 

I'll be there about 5PM Friday evening through Sunday.


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## sachu

XLR inputs would be ideal i suppose but I don't plan on ever going balanced so thus I have SE inputs..

 And yes for now the idea is to stick to 6S4 tubes..though there has been talk of making it possible to swap between EL34 and 6S4 tubes.


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## runeight

The inputs are balanced but can be driven SE for both versions.


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## ericj

Details are coming. 

 One thing I'd like to point out, that $325ish number pabbi1 gave is all-inclusive. 

 You can stuff both the PS and amp boards with Mouser parts, and that Mouser order is under $200 including the iron. 

 All you need aside from that is the boards, suitable hookup wire, a socket compatible with your chosen headphones, and a box to stick it in. And a power cord for the filtered IEC inlet. 

 A determined cheap person could bring it in under $250.


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## sachu

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_Details are coming. 

 One thing I'd like to point out, that $325ish number pabbi1 gave is all-inclusive. 

 You can stuff both the PS and amp boards with Mouser parts, and that Mouser order is under $200 including the iron. 

 All you need aside from that is the boards, suitable hookup wire, a socket compatible with your chosen headphones, and a box to stick it in. And a power cord for the filtered IEC inlet. 

 A determined cheap person could bring it in under $250._

 

Agreed,

 I would actually say this can be put together for about 225-230. Mine totals to about 275 and that includes the 8$ RCA jacks, 10$ shaft extension kit, 14$ knob ,32$ potentiometer and a surplus case that cost me 7$.


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## HeadphoneAddict

That is just amazing!

 This weekend we'll get to try O2 Mk1, Jade, HE60, SR-404LE, and Smegma Pro with wiatrob's. I'm assuming it's Pro bias, or I'll have to grab my SR-Lambda as well for normal bias.


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## les_garten

*@Pabbi1*

 are you getting any hum with this setup?


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## wiatrob

The rigs at RMAF will be fully balanced (one may have a switchable set of SE inputs) - but will use two pots (RK27s) for volume control in keeping with the affordable nature of this amp...


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## HeadphoneAddict

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_The rigs at RMAF will be fully balanced (one may have a switchable set of SE inputs) - but will use two pots (RK27s) for volume control in keeping with the affordable nature of this amp..._

 

Bill, do you want me to bring two balanced DAC's with me to RMAF? Also, how much more costly is one balanced volume pot vs having the two volume pots?


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## dBel84

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_A determined cheap person could bring it in under $250._

 

how about an uber frugal CB 
	

	
	
		
		

		
			





 ..dB


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## ericj

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Bill, do you want me to bring two balanced DAC's with me to RMAF? Also, how much more costly is one balanced volume pot vs having the two volume pots?_

 

four-deck pots are uncommon -- iirc the Alps blue one approaches $50, vs. $13-$17 each for the regular stereo pot.


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## dBel84

you could always use a single shunted deck for balanced operation - there are a few threads that deal with this option ..dB


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## wiatrob

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_That is just amazing!

 This weekend we'll get to try O2 Mk1, Jade, HE60, SR-404LE, and Smegma Pro with wiatrob's. I'm assuming it's Pro bias, or I'll have to grab my SR-Lambda as well for normal bias._

 

That will be a very nice comparo! 
	

	
	
		
		

		
		
	


	




 Both amps will have Pro and Normal bias jacks simultaneously available and we can tweak the high bias for the phones of your choice - provided they plug into a 'standard' Stax Jack or you have an adapter cable.


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## wiatrob

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Bill, do you want me to bring two balanced DAC's with me to RMAF? Also, how much more costly is one balanced volume pot vs having the two volume pots?_

 

Thanks for the DAC offer, I'll have my DACMagic, but we can chat offline about it.

 AFA balanced pots go - you could always add a nice stepped attenuator and double the parts cost of the amp! 
	

	
	
		
		

		
		
	


	




 I have a candidate balanced and affordable pot here, I'll be wiring it up and if it works well it might go into one of the amps.


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## dBel84

That adjustable bias makes me think that those panel led meters will be very handy ..dB


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## smeggy

this is gonna be sweet!

 Can't wait to get one of these up and runing


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## wiatrob

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_That adjustable bias makes me think that those panel led meters will be very handy ..dB




_

 

You mean something like the attached? 
	

	
	
		
		

		
		
	


	




 We've (er, I've) investigated, and while it can be done, there are a few caveats (most of these require additional 12V DC power, and the stat bias supply voltage is easily pulled down...)


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## Currawong

The Sun box is very classy. I have some of those....back in Australia. 
	

	
	
		
		

		
			





 I'll definitely be building this when it's available, as I have to give back my borrowed 007t.


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## runeight

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_*@Pabbi1*

 are you getting any hum with this setup?_

 

Pabbi1 may have missed this post. I can only say that so far he has not reported any hum or noise.


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## les_garten

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Pabbi1 may have missed this post. I can only say that so far he has not reported any hum or noise._

 

Thanx! Just curious with the Transfos kinda close.


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## spritzer

There are some very cheap 4-gang stepped attenuators on ebay which would fit this nicely. They all use the same old, cheap 23 step switch but some use Vishay resistors for about 30$. 

  Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_That adjustable bias makes me think that those panel led meters will be very handy ..dB




_

 

This could work if the meters have a very high input impedance. Otherwise the bias voltage will drop and you won't get an accurate reading.


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## n_maher

Great work guys! I wish this had been around a year ago, might have saved me some serious $$.


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## manaox2

Got the tubes and sockets, have been waiting on the BOM. Thanks so much all for doing this, this is going on my Christmas list.


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## pabbi1

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_*@Pabbi1*

 are you getting any hum with this setup?_

 

Absolutely zero. The Triads are mechanically noisy, and have gromets underneath to isolate this, but absolutely none comes through the amp, at least not that I can hear. But, isolated mounts will be required with the (really cheap) Triads.


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## luvdunhill

Great work! It's sort cool that we have two additions to the uber-high-end and now two additions to the low-end electrostatic amplifier family after such a long time of no new designs


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## manaox2

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Great work! It's sort cool that we have two additions to the uber-high-end and now two additions to the low-end electrostatic amplifier family after such a long time of no new designs 
	

	
	
		
		

		
		
	


	


_

 

T2, SS eXStata, Tube eXStata, whats the second uber high-end DIY design? (Assuming your not talking about the KGSS or BH)


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## wiatrob

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Absolutely zero. The Triads are mechanically noisy, and have gromets underneath to isolate this, but absolutely none comes through the amp, at least not that I can hear. But, isolated mounts will be required with the (really cheap) Triads._

 

X2 - I have used bothe the Triads and Hammond very close to the boards in testing and there's no induced hum. This amp seems very robust when it comes to extraneous noise - I have had quite a bit of spagehtti on the bench and as long as the grounds are correct, silence...


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## Emooze

Congrats all for seeing this through. I think I found my next build, eagerly awaiting a BOM and boards.


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## luvdunhill

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_T2_

 

that would be the improved (working) "ES-1/ES-2" design


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## nattonrice

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_T2, SS eXStata, Tube eXStata, whats the second uber high-end DIY design? (Assuming your not talking about the KGSS or BH)_

 

He means the diy SRX.

 edit: lol had a funny feeling I'd be too slow typing =]


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## les_garten

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Absolutely zero. The Triads are mechanically noisy, and have gromets underneath to isolate this, but absolutely none comes through the amp, at least not that I can hear. But, isolated mounts will be required with the (really cheap) Triads._

 

 Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_X2 - I have used bothe the Triads and Hammond very close to the boards in testing and there's no induced hum. This amp seems very robust when it comes to extraneous noise - I have had quite a bit of spagehtti on the bench and as long as the grounds are correct, silence..._

 


 Awesome, Thanx!


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## runeight

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Great work! It's sort cool that we have two additions to the uber-high-end and now two additions to the low-end electrostatic amplifier family after such a long time of no new designs 
	

	
	
		
		

		
		
	


	


_

 

I wouldn't necessarily compartmentalize this amp this way. It may be inexpensive but it may not at all be low-end. The performance may be much better than the price tag indicates.


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## spritzer

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_that would be the improved (working) "ES-1/ES-2" design_

 

Plus the insane all DHT amp and the equally nutty SS amp.


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## ericj

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Great work! It's sort cool that we have two additions to the uber-high-end and now two additions to the low-end electrostatic amplifier family after such a long time of no new designs 
	

	
	
		
		

		
		
	


	


_

 


 I'm not sure i'd really call it low-end. From my vague memories of headphoneaddict's srm-1, I think the low-end is still held by the cheaper stax amps. 

 You could ask sachu why he sold his SRM-1 recently, too. 

 This is just by far the most accessible DIY option.


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## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I wouldn't necessarily compartmentalize this amp this way. It may be inexpensive but it may not at all be low-end. The performance may be much better than the price tag indicates. 
	

	
	
		
		

		
		
	


	


_

 

Quite right Alex. 

 I don't remember my ESP950 sounding this good even with the SRM-717 but I reserve judgment till I compare head to head.

 The best 'dynamic' amp I have heard to date is the original stacker of Don's and he put it together for less than 100$. 
 Parts cost doesn't necessarily translate into high end or low end and those involved in the DIY scene know this all too well. 

 So lets not play that game.


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## ericj

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Quite right Alex. 

 I don't remember my ESP950 sounding this good even with the SRM-717 but I reserve judgment till I compare head to head._

 

If i can put down the normal-bias lambda for long enough tonight I'll finally wire up an esp950 socket to my eXStatA. 

 But from memory, esp/950 + e/90 > SR-lambda + srd-7, but SR-lambda + eXStatA > esp/950 + e/90.


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## luvdunhill

I suppose I should have chosen my words more carefully 
	

	
	
		
		

		
		
	


	




 Have anyone gotten this on any test equipment yet? I'm assuming Alex at least has some square wave traces lying around somewhere


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## smeggy

heh, that's funny, I thought I was the only one who thought the 950, e90 was actually better than with the SRD-7 and Lambdas or 950. The e90 gets a lot of bad press, largely deserved but it still does a good job for the 950 compared to anything else in the low price range. 

 This amp should do a great job of filling a gap in what's available at reasonable cost, and that's something I never imagined would ever happen as most designs coming out/existing are solidly in the high price area. This is a very welcome addition that will help give us 'less financially fluid' people a real step up.


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## ericj

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_This amp should do a great job of filling a gap in what's available at reasonable cost, and that's something I never imagined would ever happen as most designs coming out/existing are solidly in the high price area. This is a very welcome addition that will help give us 'less financially fluid' people a real step up._

 

Precisely the frustration that led me to post that initial rant bemoaning the nonexistence of this amp. 

 I think runeight did an outstanding job of answering that challenge, and far exceeded my expectations.


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## audionut

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Quite right Alex. 

 I don't remember my ESP950 sounding this good even with the SRM-717 but I reserve judgment till I compare head to head.

 The best 'dynamic' amp I have heard to date is the original stacker of Don's and he put it together for less than 100$. 
 Parts cost doesn't necessarily translate into high end or low end and those involved in the DIY scene know this all too well. 

 So lets not play that game._

 

Sachu, Have u ever heard your ESP950's with a KGSS amp? I built one P2P for my ESP 950's about 6 months ago and it sounds great. Was kinda wondering how this new amp might sound compared to the KGSS. Also, I use my Cavalli Bijou tube amp for a preamp with my KGSS/ESP950 rig, as I feel it gives that tube sound that I love, better, fuller bass, etc. I'm sure I'm going to go ahead and build this amp too (probably the tube version), since I already have the KGSS. Just wanted to know if you'd ever heard the KGSS/ESP950 combo and how it might sound compared to this new stat amp.
 Thanks


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## Keithpgdrb

I am very excited about this project. so.. how "intermediate" is this thing. what intermediate skills should you have before attempting it. I'm fairly new to diy, but building this amp is pretty high on my "want to do" list. maybe this question is better off in the original thread. it can be moved if so.


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## bada bing

Cool project. Color me interested.

 What's a reasonable ETA for boards and a BOM ?

 And I've seen the posts on Stax jacks, but not anything about availability to unwashed masses. Is there a resolution for jacks ?


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## sachu

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Sachu, Have u ever heard your ESP950's with a KGSS amp? I built one P2P for my ESP 950's about 6 months ago and it sounds great. Was kinda wondering how this new amp might sound compared to the KGSS. Also, I use my Cavalli Bijou tube amp for a preamp with my KGSS/ESP950 rig, as I feel it gives that tube sound that I love, better, fuller bass, etc. I'm sure I'm going to go ahead and build this amp too (probably the tube version), since I already have the KGSS. Just wanted to know if you'd ever heard the KGSS/ESP950 combo and how it might sound compared to this new stat amp.
 Thanks_

 

I haven't heard it with the KGSS but would love to. I have been toying with the idea of building one for myself but I would like to listen to it first.

 Going from memory (do take this with a grain of salt), the ESP950 with the BHSE was sounding great in the mids and the highs but the bass left me wanting. Not the case with the O2, just the ESP950. 
 Then agian I would love to listen to my ESP950 with the BHSE again with a higher bias setting (the one i heard was set at 580 volts) and in a more controlled environment. Meet conditions are pathetic to do critical listening.

 All I can say is that this amp does make the ESP950 sound more balanced instead of sounding dark (as is the case wit the Stax amp I have) and brings out details that I didn't notice earlier. I am looking forward to doing a comparision between this amp and the SRM-717 and i think a SRM-006. Also looking forward to listening to the O2 and SR-404 on it.


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## sachu

Quote:


  Originally Posted by *bada bing* /img/forum/go_quote.gif 
_Cool project. Color me interested.

 What's a reasonable ETA for boards and a BOM ?

 And I've seen the posts on Stax jacks, but not anything about availability to unwashed masses. Is there a resolution for jacks ?_

 

Don't really know about ETA for boards, only runeight can answer that. The tube version is not up yet. But, expect one or two tube versions if everything goes well by the end of the week and few more the following week.


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## ericj

Quote:


  Originally Posted by *Keithpgdrb* /img/forum/go_quote.gif 
_I am very excited about this project. so.. how "intermediate" is this thing. what intermediate skills should you have before attempting it. I'm fairly new to diy, but building this amp is pretty high on my "want to do" list. maybe this question is better off in the original thread. it can be moved if so._

 

I wouldn't call this a difficult build at all. 

 But with the voltages involved, it's certainly more dangerous. 

 We're talking about voltages that are potentially fatal if you disrespect them in the wrong way. It's not hard to avoid dying, but we can't stress enough the need for care when working with an amp with 600 volts DC across it. 

 Runeight has done a lot to make it harder to kill yourself with the amp. Most of the transistors turn out to be in all-plastic packages so there can be no chance of electrical potential in the heatsinks (Two transistors do have a metal pad on the back, and using an insulator there is a good idea). The heatsinks are not grounded, so they cannot be used to provide a path to ground through something like a screwdriver or your arm. An insulated trimpot tweaker is included in the BOM and it's both cheap and entirely decent. 

 But we're still talking about a 300-0-300 DC power supply. 

 For anyone who isn't 100% sure if they're ready to build this - I'd have to say, consider what your error rate was on the last 2 amps you built - how many components in the wrong place or the wrong way, how many solder bridges in the wrong place, how many times you damaged the board or a component along the way - and certainly if you ever did something like accidentally drop the bare amp board off the workbench while it was powered or while there may have been juice in the capacitors. 

 Ask yourself, if you concentrate and really get serious about it, could you have brought that error rate down near 0? 

 If you're pretty sure you can, I say you can probably successfully build this amp without killing yourself, injuring your cat, or having to order too many replacement parts. 

 Most of us made at least one mistake while prototyping this amp. I myself misplaced a single diode, and was lucky enough that it's placement didn't damage anything. 

 But if you have recent memories of a ruined, smoking hulk of a low-voltage amp board, you should give it some serious consideration before playing with high voltages.


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## audionut

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_I haven't heard it with the KGSS but would love to. I have been toying with the idea of building one for myself but I would like to listen to it first.

 Going from memory (do take this with a grain of salt), the ESP950 with the BHSE was sounding great in the mids and the highs but the bass left me wanting. Not the case with the O2, just the ESP950. 
 Then agian I would love to listen to my ESP950 with the BHSE again with a higher bias setting (the one i heard was set at 580 volts) and in a more controlled environment. Meet conditions are pathetic to do critical listening.

 All I can say is that this amp does make the ESP950 sound more balanced instead of sounding dark (as is the case wit the Stax amp I have) and brings out details that I didn't notice earlier. I am looking forward to doing a comparision between this amp and the SRM-717 and i think a SRM-006. Also looking forward to listening to the O2 and SR-404 on it._

 

Sachu, You got PM. Let me know if you got it


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## runeight

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_I wouldn't call this a difficult build at all. 

 But with the voltages involved, it's certainly more dangerous. 

 snip... 

 If you're pretty sure you can, I say you can probably successfully build this amp without killing yourself, injuring your cat, or having to order too many replacement parts. 

 Most of us made at least one mistake while prototyping this amp. I myself misplaced a single diode, and was lucky enough that it's placement didn't damage anything. 

 But if you have recent memories of a ruined, smoking hulk of a low-voltage amp board, you should give it some serious consideration before playing with high voltages._

 

Hard to add to this. 
	

	
	
		
		

		
		
	


	




 But a few more thoughts that might help.

 One of the prototypers used 4k7 instead of 470 in two locations in the PS. And though the PS couldn't come to full voltage nothing blew up. Using the correct values fixed the problem with no other issues.

 There were a few other errors in the builds but none of them caused component damage.

 Not to say that this won't happen (it can) with constructions errors, but the build is pretty durable.

 And when built properly it comes up easily. Bias/balance/offset adjustments are simple and, it appears right at this moment, to stablize after an hour or two of runtime.

 But, more time on each amp is needed to be certain there are no unexpected or as yet undetected problems. 

 In the meantime tube version boards are on their way to prototypers. They should be showing up soon.


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_One of the prototypers used 4k7 instead of 470 in two locations in the PS. And though the PS couldn't come to full voltage nothing blew up. Using the correct values fixed the problem with no other issues._

 

hmm wonder who that was?


----------



## Coreyk78

Very interested in this amp, happy to see that its almost ready, although my wallet won't be as happy 
	

	
	
		
		

		
		
	


	




 This will probably be put in line after I finish my Aleph-J and Millet "Engineer's Amp" speaker amps and my Buffalo DAC. 

 If I read Pabbi1's post correctly electret stax are compatible with this amp? Would be good news, I could use my SR-30 for testing purposes then to make sure I have a working amp before I invest in some electrostatics.


----------



## ericj

That is correct. 

 We suspect that Sony electrets may not be compatible due to their crazy-wide stator spacing needing crazy-high gain. But i haven't actually tried it. 

 But the SR-40, SR-30 (which is SR-60 in europe), and SR-80 are all compatible with this amp, as are the Audio-Technica electrets (provided they aren't one of the weird models with a TRS plug - but those can be converted to a 5 pin plug no problem)


----------



## spritzer

I've tried Sony ECR's on a standard Stax solution and they need quite a bit more voltage to work. Opening up the drivers makes this clear as well.


----------



## 00940

To the designers: I'd need an amp with a voltage swing of 250Vp-p, gain of 80 or so and running from a single 300V supply. Frequencies of interest are 1Khz and above.

 Could the ss version be modified for those requirements ? I guess input and output caps will be in order at least.


----------



## spritzer

The small Stax amps are basically what you are describing but with higher gain. Input and output caps would certainly be needed.


----------



## pabbi1

I have to also say this amp really isn't 'low end' at all - how far into the upper tier is yet to be determined, but I have been startled by some of the detail, layering, air and speed. Oh, and PRaT - it just makes listening fun - again.

 Marc, we can always put mine on your scope... 
	

	
	
		
		

		
		
	


	




 Oh, yeah, and about those jacks... the elves might need to get busy, as I see a wee bit of demand. This amp IS worth it.

 Let me further say the amp is NOT the weak point in my chain with the Azur 840c and the he60. It is remarkably up to the task with both of those components.

 Now, we just need comparisons, and honest, unbiased observations from outside the team, which will be coming shortly.


----------



## Emooze

I notice people keep asking for input and output waveforms and it seems very few have the equipment to do so. Do you just need a function generator and scope? My school labs have them and I know they have no qualms about me using them for personal projects. I'd be more than happy to help out once I build an amp.


----------



## mypasswordis

Hats off to runeight for designing the eXStata SS and hybrid amps, and the prototypers for... prototyping. I eagerly await more impressions on the SS versions and of course the inclusion of the hybrid version soon. Cheers.


----------



## wolf18t

Count me in the seriously interested builders crowd. My only problem is that I don't have any stats. Very handy for the final QC test. 
	

	
	
		
		

		
		
	


	



 But that shouldn't be a problem for very long. 
	

	
	
		
		

		
		
	


	




 One thing I would need before getting into the project is find info of what are the bias standard and what are the connectors needed/available for what phones. I'm a total stats newbe.

 As for the high voltage, I agree this is something to take seriously. You always have to take your time and think twice of what you're doing while working around this voltage. Like manipulating the DMM probes with the circuit offline and caps discharged. That reminds me the old days I was repairing computer tube monitors, working around the flyback and the horizontal amplifier...


----------



## ericj

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_One thing I would need before getting into the project is find info of what are the bias standard and what are the connectors needed/available for what phones. I'm a total stats newbe._

 

That's all pretty academic stuff. Stax are generally 230v for old stuff and 580v for new stuff. The koss esp/950 (which is about the best deal going for an electrostatic headphone) is 600v. 

 Staxen use a 6-pin or 5-pin socket available either from Cooper/WPI through Allied Electronics or from various boutique fabricators. The Koss have a unique connector available only from Koss either by gutting the included amp or by chopping the end off a $16 extension cord.


----------



## Lou Erickson

Color me interested, too. I am thrilled to see something like this for the electrostatics! Thank you all so much for working so diligently on this!

 I'll be right there when boards and BOM are ready!


----------



## sergery

Wow, all of the sudden from quiet to loud in the now exStatA camp! Thanks proto team!


----------



## wiatrob

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_I have to also say this amp really isn't 'low end' at all - how far into the upper tier is yet to be determined, but I have been startled by some of the detail, layering, air and speed. Oh, and PRaT - it just makes listening fun - again._

 

I've been building up the first tube board and listening critically to the sand amp for about three hours straight.

 The detail and separation of this amp are outstanding. In fact, If I didn't have a soldering Iron in my hand, I'd be dancing around the workshop. 

 This amp is just plain _fun_! I would agree with Al it performs well above the demands of the initial requirements.

 No bass demands this evening - but FLAC'd Infected Mushroom last week was pounding on both the Lambdas and Lambda Sigs. 

 I have a scope here (guess I could use my PC as a function generator). I say let *YOUR* ears be the judge!


----------



## dBel84

so remind me why i didn't proto this with you lot :? ..dB


----------



## runeight

I think you were just beginning your secret mission and didn't want to be distracted.


----------



## smeggy

NINJA!!!


----------



## mypasswordis

Does that secret mission involve 6S4As?


----------



## sachu

nope..moar like 6CG7s, 12SN7GT and a whole slew of toobs 
	

	
	
		
		

		
		
	


	




 *cough* stack..er *cough*


----------



## sachu

wow..this is such a fun amp...racked up another 6 hours today 
	

	
	
		
		

		
		
	


	




 The details on the amp especially with my newly acquired source (DAC 2.6) is just breathtaking. i can't seem to turn it off and hit the sack..feel like spinning more and more CDs 
	

	
	
		
		

		
		
	


	




 And the bass is just about perfect now thanks to the source. Had been listening with the Denon DVD-5000 till yesterday.


----------



## srserl

If any of the prototypers are coming out to the BAF*...please bring it with you.

 *Burning Amp Festival


----------



## sachu

aaah crap..I am making my way down to SFO next weekend though..


----------



## luvdunhill

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I have a scope here (guess I could use my PC as a function generator). I say let *YOUR* ears be the judge!_

 

heh, I think Alex may not appreciate his beauty being evaluated with square waves from a sound card


----------



## ericj

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_heh, I think Alex may not appreciate his beauty being evaluated with square waves from a sound card 
	

	
	
		
		

		
		
	


	


_

 

Especially as most sound cards can't generate a proper square wave over about 4khz.


----------



## Coreyk78

This the socket you guys used?

Cooper Interconnect - 78-S6S - Allied Electronics


----------



## macm75

Ridiculous, I think the price jumped from $3 range to $5 looks in the past few months. Still, that is the cheapest one I know of and it works perfectly for all Stax.


----------



## n3rdling

Very cool guys! Can't wait to hear this amp someday.


----------



## krmathis

Great work guys! 
	

	
	
		
		

		
		
	


	



 Looks like an amplifier with quite a potential, especially considering the parts cost.


----------



## wiatrob

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_heh, I think Alex may not appreciate his beauty being evaluated with square waves from a sound card 
	

	
	
		
		

		
		
	


	


_

 

I'll just fix them in Photoshop afterwards


----------



## pabbi1

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_This the socket you guys used?

Cooper Interconnect - 78-S6S - Allied Electronics_

 

No, sweetie - I used this one, $25 from Jack Woo:






 But, it deserves THIS one, quite a bit pricier from luvdunhill:


----------



## smeggy

those are the ****!


----------



## ericj

Yeah but how much do they cost?


----------



## smeggy

probably 1/5th of the amp


----------



## les_garten

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_Yeah but how much do they cost?_

 

They do look a might bit pricey!


----------



## Frihed89

I heard the Exstata at RMAF, yesterday. This is a heart-breaker, it sounds so good. Moreover, it is "relaxing" and has a nice "lilt" to it. Dead quiet, by the way.

 I hope it comes to market.

 The "maker" was a very nice guy and I wish him all the luck.

 Yes, I heard it through a bunch of a ELS headphones, but it is the amp not the phones that made the biggest impression on me, personally.


----------



## DoYouRight

very exciting


----------



## HeadphoneAddict

The eXStata is a great amp, but it was so highly detailed that we could hear jitter (grainy griity in the highs) with the Apple TV on Saturday, which at first was more difficult to pick up with the GES until 3 hours into the meet, making us have to change the transport to a Macbook Pro instead (big improvement). I posted about this in the CanJam @ RMAF impressions thread Saturday. 

 Although much better with a new transport, it was still a bit bright with my PS Audio Digital Link III, and more suited to the O2 Mk1. Also we think the PSA was overdriving the XLR inputs which we measured on Sunday at 5v @ 60Hz. So on Sunday (today) Bill started the day with a DIY Opus DAC, and that fixed the sound completely. At that point the amp was very good to my ears with O2 Mk1, Jade, SR-404 LE, HE60, Smegma Pros (woody Gamma pro), SR-404 LE, and SR-Lambda normal bias. 

 Being in a separate rig than the GES on Sunday made it more difficult to compare the amps like we did on Saturday. But on Saturday (with the same source and side by side) we felt the Woo's timbre and tone/Frequency balance was better, but the soundstage and separation was much better with the balanced eXStata (with a little more power too). With the Opus DAC the brightness/thinner sound became more balanced and punchier in the bottom end, and with even more power - enough to tickle your ear drums and make the skin on your face vibrate with O2's. I thought that wiatrob had modded the amp overnight, the improvement was so dramatic!

 Today, at the end of the meet, we tried the CullenCircuits modded PS Audio which was better with the eXStata than the stock PSA, but the Opus DAC seemed to have the best synergy with it to me. I picked my PS Audio DLIII initially because it was what I needed to brighten up the dark sounding O2 Mk1 with the GES (after rolling brighter tubes). What works for the GES isn't always the best for the eXStata. I was very impressed with the eXStata by the time we had sorted out all the jitter/synergy issues with the transport and DAC. *Even if nothing gets changed in the design, this amp will still be a big hit*, and my understanding is there are still a few things that can be done to make it even better. The listener just needs to remember that with this amp whatever you feed it is VERY important, because it will be so resolving that you will hear any issues - for example it was fairly bad with 192k MP3 files on the Cullen modded DAC owner's PC, and we had to switch to a CD transport to evaluate the amp with the Cullen modded PSA DAC.

 It's caused a dilemma for me because I was thinking I would have to sell my GES, WA6, K1000 and RS-1 for a Woo WES, and now maybe all I really need is to add an eXStata (and EHHA for K1000) to what I already own, and just sell the APS V3 RS-1 to cover the cost.


----------



## Emooze

Oh so the eXStata had no issues driving the O2 or some of the more demanding headphones? I remember that that was a point someone brought up when the design was first being tossed around but that's impressive.

 Honestly can't wait for this...


----------



## ericj

Well, during the brainstorming phase i'd said something like we didn't want "drive the O2 to within an inch of it's life" as a design goal because, imho, this is the sort of objective that leads to 'stat amps that have a $2000 BOM. 

 The eXStata performs well beyond expectations.


----------



## wiatrob

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_Oh so the eXStata had no issues driving the O2 or some of the more demanding headphones? I remember that that was a point someone brought up when the design was first being tossed around but that's impressive.

 Honestly can't wait for this..._

 

We listened with almost every set of stats at the meet (save Ray Samuel's HE-90s). 

 I think almost everyone who heard the amp with them would agree it had no trouble driving O2s. Bonus!

 I wish we had a set of 950s there...


----------



## Sherwood

Yeah, I'd have loved to have heard the 950s as well.

 We need to talk about me getting one of these for keeps, Bill. I had a dream about it


----------



## sachu

The eXStatA is a perfect fit for the ESP950.

 Its like they were made for each other.


----------



## les_garten

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_The eXStatA is a perfect fit for the ESP950.

 Its like they were made for each other._

 

Ok, where's the board signup list!!??


----------



## Sherwood

Get in touch with Bill (wiatrob/Spruce Canyon Labs)-- the distribution for this amp might be a little out of the ordinary.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_Oh so the eXStata had no issues driving the O2 or some of the more demanding headphones? I remember that that was a point someone brought up when the design was first being tossed around but that's impressive.

 Honestly can't wait for this..._

 

Like I said before, it had no problem driving the O2 Mk1 at all. Everything else was also a piece of cake (Jade, HE60, SR-404LE, SR-Lambda Signature, SR-Lambda, SR-Gamma Pro with wood cups/O2 Mk1 pads. It could cleanly drive the O2 loud enough with infected mushroom to vibrate the skin around my ears and tickle my ear drums. It was quite sensitive to the sound of the DAC and transport being used - ruthless in fact.

  Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_We listened with almost every set of stats at the meet (save Ray Samuel's HE-90s). 

 I think almost everyone who heard the amp with them would agree it had no trouble driving O2s. Bonus!

 I wish we had a set of 950s there..._

 

950's are as easy to drive as a Lambda Sig, and since it can sound good with my HE60 then the ESP-950 would be a no brainer.

  Quote:


  Originally Posted by *Sherwood* /img/forum/go_quote.gif 
_Get in touch with Bill (wiatrob/Spruce Canyon Labs)-- the distribution for this amp might be a little out of the ordinary._

 

Don't forget I'm already first in line.


----------



## les_garten

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Like I said before, it had no problem driving the O2 Mk1 at all. Everything else was also a piece of cake (Jade, HE60, SR-404LE, SR-Lambda Signature, SR-Lambda, SR-Gamma Pro with wood cups/O2 Mk1 pads. It could cleanly drive the O2 loud enough with infected mushroom to vibrate the skin around my ears and tickle my ear drums. It was quite sensitive to the sound of the DAC and transport being used - ruthless in fact.



 950's are as easy to drive as a Lambda Sig, and since it can sound good with my HE60 then the ESP-950 would be a no brainer.



 Don't forget I'm already first in line. 
	

	
	
		
		

		
			



_

 

So, RE: the OII MK1s, you would prefer this to the GES that you have? Understanding that you've only had limited exposure, you feel it is more capable than the GES?


----------



## ericj

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_So, RE: the OII MK1s, you would prefer this to the GES that you have? Understanding that you've only had limited exposure, you feel it is more capable than the GES?_

 

I find it quite satisfying that our little amp is being compared in this manner to an amp that lists at $1450.


----------



## les_garten

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_I find it quite satisfying that our little amp is being compared in this manner to an amp that lists at $1450._

 

As well you should!


----------



## Sherwood

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_ Don't forget I'm already first in line. 
	

	
	
		
		

		
		
	


	


_

 

Shoot, Larry, I've been in line for two months.


----------



## sachu

Quote:


  Originally Posted by *Sherwood* /img/forum/go_quote.gif 
_Shoot, Larry, I've been in line for two months. 
	

	
	
		
		

		
		
	


	


_

 

Heh..looks like Smeggy beat you both to it..He should be getting his within the next two weeks..or as soon as I can get myself to smelling those solder fumes.


----------



## spritzer

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_I find it quite satisfying that our little amp is being compared in this manner to an amp that lists at $1450._

 

It does make sense though since if the extata would be sold commercially (in the sense how Woo amps are sold, not DIYFS) then it would be in that price range.


----------



## ericj

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_It does make sense though since if the extata would be sold commercially (in the sense how Woo amps are sold, not DIYFS) then it would be in that price range._

 

Dunno, there's so much more STUFF in the GES. Having more parts surely must make it sound better?


----------



## spritzer

They are very different amp designs (AC vs. DC coupled to start off with) but similar complexity. The GES may look more busy because of all the coupling caps but that's not really the case. The GES could certainly be built for 400$ and the same goes for a KGSS, Egmont, Stax SRX etc. It all depends on how frugal the builder is and parts used.


----------



## ericj

Ahh. 

 Sure is a lot more bling on the outside, though.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_So, RE: the OII MK1s, you would prefer this to the GES that you have? Understanding that you've only had limited exposure, you feel it is more capable than the GES?_

 

Let me put it this way, the improved soundstage, separation and power vs the GES is enough to make me want one even if the frequency response wasn't optimal in my rig. However, with the Marantz CD5001 > OPUS DAC > eXStatA I thought it sounded good with all the stats we tried. It sounds more solid state than tubey like my GES, but I still enjoyed it just as much. I liked the WES the most followed by the A-10 for their richer mids, but now it would be a choice between the WES and eXSstata if I was buying my first stat amp and didn't have one for my O2 Mk1. The KGBH SE mids were lacking a bit vs the others. The GES is a bit richer and refined sounding, so the eXSstatA wont be replacing my GES for my Jade, HE60, Smegma Pro, SR-404 LE, SR-Lambda, SR-5 gold edition and SR-003. On the other hand, the WES is good enough to replace my GES, but those cost 2x my maxed GES which has pro/normal bias and loop out.


----------



## runeight

Hello everyone.

 There seems to be some concern that there won't be a diy offering of this amp. 

 So, to settle this concern, there will be. In fact, I've already created the web pages on Cavalli Audio website similar to the other designs there. They just haven't been turned on yet.

 However, since this is a HV amp I want to have more builds working for more than just a few days before making a release. I learned with the Bijou that HV can be problematic for some first time builders. And we want to be sure there are no problems that occur over time that don't happen in the first few hours.

 There is still only one tube version of the amp working (it is working properly), but not enough time with it to make a release to all possible interested builders.

 We may want to put a few more amps in the hands of an additional group of people for testing/listening before there is a general diy release. More hands and ears. So, hang in there while the testing period continues. 

 And look for some reports on the tube version.


----------



## sachu

^^^ thanks for setting the record straight Alex.

 And thanks again for your generosity to the DIY community. This amp is going to debunk some myths (and has done so already) and will bring great electrostats sound to more people at a low cost.


----------



## les_garten

Hey Alex,
 Thanx for the info here! Very nice project you guys have pulled off here. Can't wait for the finished project to be available. Great work and great reviews!


----------



## HeadphoneAddict

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Hello everyone.

 There seems to be some concern that there won't be a diy offering of this amp. 

 So, to settle this concern, there will be. In fact, I've already created the web pages on Cavalli Audio website similar to the other designs there. They just haven't been turned on yet.

 However, since this is a HV amp I want to have more builds working for more than just a few days before making a release. I learned with the Bijou that HV can be problematic for some first time builders. And we want to be sure there are no problems that occur over time that don't happen in the first few hours.

 There is still only one tube version of the amp working (it is working properly), but not enough time with it to make a release to all possible interested builders.

 We may want to put a few more amps in the hands of an additional group of people for testing/listening before there is a general diy release. More hands and ears. So, hang in there while the testing period continues. 

 And look for some reports on the tube version. 
	

	
	
		
		

		
		
	


	


_

 

Alex, Congrats! This is going to be a game changer, because no longer will the SRM-717 be the cheap option for driving the Stax O2. It will also make a lot of people who are trying to sell their lesser vintage Stax amps unhappy.

 I want to upgrade my GES to a WES, but don't think I can afford it - in that case I want to get an eXStata in addition to my GES. I think it will make a nice addition around here to have both. All that remains is to determine whether it's the 6S4 tube version or SS version, and whether power upgrades will be available. I found a really nice guy to build one already.


----------



## DoYouRight

I am dying for this one...


----------



## les_garten

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_
 So, to settle this concern, there will be. In fact, I've already created the web pages on Cavalli Audio website similar to the other designs there. They just haven't been turned on yet.
_

 

Will you be doing as much detail to the Exstata pages as for your other designs? Your page is very AMB like and a real boon to new builders.


----------



## Keithpgdrb

I was a bit confused by the earlier post. I thought the intention of the original amp thread was to make it diy. I must have missed some banter somewhere. Either way, glad to see this will be an available build at some point.


----------



## Currawong

Thanks for the impressions Larry. I just handed back my borrowed 007t today, so I'm very much looking forward to building one.


----------



## spritzer

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_Ahh. 

 Sure is a lot more bling on the outside, though._

 

True but you can find those Woo cases cheap in China if you know where to look. 
	

	
	
		
		

		
			





 Not that I'd use them for a SS amp but a Hifi-2000 Galaxy case would look great for a minimal outlay. 

 I'm all for a cheap and easy ESP amp but it would be wrong to think that the Exstata is the only alternative. With Justin now offering KGSS PCB's for sale (100$ for the set) you could build a KGSS for 600$ with some wise part choices. No 300$ 4-gang DACT's (30$ ebay stepper or a 40$ Alps RK27 balanced pot instead), matched singles instead of the rare 2sk389's, cheaper subs for the PSU sand as just some suggestions which will make the amp a bit cheaper to build but do little to sacrifice its quality. 

 Even cheaper would be to build an amp point-to-point such as the Stax SRX. Just take a metal plate and mount the necessary tube sockets plus some terminal strips and start wiring it up. There are some small tricks such as how to deal with the filament wiring and ground but these are minor obstacles.


----------



## dcpoor

All these new more affordable stat amps have got me excited.


----------



## les_garten

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Let me put it this way, the improved soundstage, separation and power vs the GES is enough to make me want one even if the frequency response wasn't optimal in my rig. However, with the Marantz CD5001 > OPUS DAC > eXStatA I thought it sounded good with all the stats we tried. It sounds more solid state than tubey like my GES, but I still enjoyed it just as much. I liked the WES the most followed by the A-10 for their richer mids, but now it would be a choice between the WES and eXSstata if I was buying my first stat amp and didn't have one for my O2 Mk1. The KGBH SE mids were lacking a bit vs the others. The GES is a bit richer and refined sounding, so the eXSstatA wont be replacing my GES for my Jade, HE60, Smegma Pro, SR-404 LE, SR-Lambda, SR-5 gold edition and SR-003. On the other hand, the WES is good enough to replace my GES, but those cost 2x my maxed GES which has pro/normal bias and loop out._

 

Were the Exstatas at the RMAF of the SS or tube variety or both?


----------



## sachu

SS version


----------



## runeight

Time to start talking more about the amp now that the protos seem to be remaining stable.

 Remember that the design goals were to create a reasonably priced, but good stat amp. Part of the original desire was to not require hard-to-get components and/or expensive iron. Well, it's hard to know when components will become hard to get, so you do the best you can with what there is currently around and what seems like it will be around for a while.

 We also wanted easy-to-build and easy-to-bring-up for a moderately experience builder. 

 The goal became simple-but-good.

 When this particular design concept came to thought I scoured the web for anything that I could find that would be similar or the same. I was not able to find anything using the keywords that made sense to me. But, the web is a big place and there are plenty of good designers in the world so I haven't really got a clue if there is an amp like this somewhere else. And, of course, I am not privvy to the commercial amps, so who knows. I'm sure that you all will not hesitate .... 
	

	
	
		
		

		
		
	


	




 Many of the stat amps that I have seen use three stages. Since stat amps are balanced they use a differential front end, an intermediate gain stage, and then an output stage. Sometimes the output stage is coupled to follower to reduce the Zo of the amp so that it can push more current easily. This also increases the speed in most cases.

 This amp only uses two stages to simplify the topology. Andreas Rauenbuehler, however, has a nice two stage hybrid amp here. His transistor amp is a three stage amp as is the KGSS (although it could be argued that the diff amp and current tunnel are a single unit), for example.

 All of these amps are good stat amps each with different qualities. And since I haven't heard any of them I can't say how they sound, but others can comment on this.

 To make a two stage amp we only have two things to work with: the input stage and the output stage (followers are part of the output stage). So how do we do this?

 Well, we know that the front end will be a diff amp and that the diff amp must translate the signal down to the bottom rail. The bottom rail because HV N-type devices are easier to find than P-types and so the output device will be at the bottom rail. Fortunately for us, we have p-type devices that can make the diff amp so that their collectors/drains point down and not up.

 A classic way to handle high voltage with solid state devices is to use cascoding. Cascoding was first developed in tube topologies to generate high gain, but since tubes are usually HV devices they were not often used for HV protection. In sand circuits, however, cascodes are very handy for using an HV device to protect some LV devices that do the actual work.

 Andreas uses a circuit with pfets and HV bjts. I did not know about this when I suggested the same idea in the previous thread, but really, there is hardly anything new in circuit design. Much of what we do today is assembling basic building blocks in ways that suit our purposes. Nonetheless, pfets with cascoded HV bjts is a no brainer for the front end of a simple-but-good stat amp.

 Now that we have the signal at the bottom rail we have to reflect it back up to the top rail. One way is to provide a high impedance load for the diff amp and then to drive the grid/base of the output device. But this scheme has other drawbacks.

 The most simple way that I can think of to reflect the diff amp off the bottom rail is to use a current mirror. And since we need a cascoding effect we can use a Wilson current mirror. Wilson mirrors have also been around for a long time, we're just coupling one to the front end.

 And, that's about it for the amp topology. Schematic will be in the next post.

*Current Sources*

 There was a great temptation to use current sources in this amp. The first, not-so-good design, used them. But after some thought, it became clear that for simple-but-good, we really don't need current sources.

 In this amp, for example, the tail of the differential amplifer is connected to the positive rail which is sitting at 300V. If the front end runs at a total of 2mA the resistor at the tail can be 150k. And while this is not the 1G dynamic resistance of a current source, it is plenty good enough for the operation of this amplifier.

 Same is true on the output followers. It is tempting to load them with CCSs, but it isn't really necessary to do that to get good performance.

 Not having CCSs really simplifies the amp. Hence, this amp has no CCCs. In fact the amp has no caps either because it does not have huge open loop gain which, when tamed by NFB, leads to possible instability. It is stable without caps while still having a gain around 1000.

 The tradeoff is that at the limits of its excursion it will evidence more distortion than an amp with high NFB and high OL gain. OTOH, high NFB has its own drawbacks to the sound of an amp so, for simple-but-good, this was an easy trade to make.

 Next post, schematic.


----------



## les_garten

Hi,
 Any Glamor shots of the* latest* SS and Tube versions? Just to throw a little chum in the water!


----------



## nsx_23

Damn, I need one of these in my life.

 Not too sure whether I'd go with tube or SS though.


----------



## runeight

Here's the schematic. Values are mostly left off for the moment because there are some tweaks happening. But, this is coming.

 Please see below for further explanation.






 You can see the simple diff amp/Wilson mirror combination.

 The diff amp tail is loaded with resistors and trimpots for adjusting offset/bias.

 The jfets are J271 because the are plentiful and easy to get right now and they have high enough transconductance for this amp.

 The front end from the jfets down to the resistors below the KSA1156 is identical to Andreas front end except for choice of fets and some resistor values. The resistors on the collectors of the transistors serve two purposes: 1) to lower the voltage some on the KSA1156 and 2) more importantly to offer some protection to the source if the transistors should short out. This particular problem was pointed out by KG in the original thread.

 Then, very simply, the HV BJTs feed the Wilson mirror. The primary mirror transistors are ordinary BC550 and you can see that they never see more than about two diode drops on them. The KSC5042 (Fairchild, 900V, 10W, 300mA) is the primary output devices. It does the rail to rail duty.

 The KSC is loaded with a resistor and a follower. The follower is loaded with a resistor.

 The mirror has a 3:1 current gain ration (680/220). This helps to relieve the dynamic current swings in the jfets and, hence, reduces the distortion.

 Those of you who are paying attention will see that the gain of the amp is mostly dependent on the transconductance of the jfets. The balance is dependent on how well they are matched. Thus, it will be necessary to match the jfets to within about 10% for Idss. For the proto builders, with a batch of 20 jfets, it has been possible to get at least one and sometimes two quads of matched devices with Idss higher than 10mA. The higher the better, but nothing less than 10mA

 There is just a tiny bit of NFB to bring the gain down to 1000, but not enough to introduce instability. 

 Now, because of the mirror, this amp is basically a current amp. In effect, the jfets are driving the load resistors at the top rail through a chain of devices that pass (and amplify) the current. With 1mA in each jfet there is, therefore, 3mA in the KSC devices. You can deduce many of the resistor values from there.

 One downside to the location of the offset/bias is that they are adjusting the O/P DC through this long chain of devices, each of which will have thermal drift. This is one of the reasons for the great care in prototyping the design and not releasing immediately - to ensure that the bias stays stable over time after the amp burns in. So far, this seems to be true with the offset/balance staying less than 2V and usually less than 1V.

 We could have used an auto adjust circuit, but then this just makes it more complex and more expensive with more potential problems.

 As you can see, this is a very simple design. Transistors and resistors. And, so far, the listening tests have judged it to be very good. Theoretically, the amp is pretty fast. This would need to be confirmed on the bench. But the listenting tests indicate that it resolves very well and exposes sources in the same way.

 And, it is simple enough for almost anyone to build if you take care. I am certain that this amp will come up properly if all of the right components are in the right places and none of them are defective.

 The tube schematic will come after we're confident of more than one build. As well as other info about the next steps for a broader release.

 I hope this helps everyone.


----------



## insyte

Subscribed 
	

	
	
		
		

		
		
	


	




 Looking forward to impressions of the tube version


----------



## pabbi1

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_Hi,
 Any Glamor shots of the* latest* SS and Tube versions? Just to throw a little chum in the water!_

 

Chum in the water...


----------



## Emooze

I love how I'm taking a class that's essentially on transistor amplifiers and I can come online and start to understand everything.

 The Wilson Mirror was a new one though.

 Edit: I spy a BOM under there....


----------



## les_garten

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Chum in the water...
_

 


 Yum! Thanx!


----------



## wiatrob

Quote:


  Originally Posted by *nsx_23* /img/forum/go_quote.gif 
_Damn, I need one of these in my life.

 Not too sure whether I'd go with tube or SS though._

 


 One of the cool things about the design is that the Sand and Hybrid boards have the same footprint, so you can build both and if you use a trafo with a heater winding, swap the boards in and out of the same enclosure.


----------



## sachu

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_One of the cool things about the design is that the Sand and Hybrid boards have the same footprint, so you can build both and if you use a trafo with a heater winding, swap the boards in and out of the same enclosure._

 

And it only costs like about 50$ excluding board (and tube for tube version) costs to populate a stereo set.


----------



## wiatrob

More chum:


----------



## HeadphoneAddict

Sweet - is that running and making noise now?


----------



## wiatrob

It's running - but it's not making any _noise_...


----------



## les_garten

Both amps are going to be single board footprints?

 What tubes?


----------



## runeight

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_And it only costs like about 50$ excluding board (and tube for tube version) costs to populate a stereo set. 
	

	
	
		
		

		
		
	


	


_

 

I hope you don't really mean $50. The amp should have a reasonable cost to build, but I don't think quite that cheap. Just so folks have the right expectations.


----------



## runeight

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_Both amps are going to be single board footprints?

 What tubes?_

 

Both amps have two channels on one board, but the boards are scored so you can snap them in half.

 Tubes are 6S4.


----------



## les_garten

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Both amps have two channels on one board, but the boards are scored so you can snap them in half.

 Tubes are 6S4._

 

Ahh, now I get it, thanx!

 Any feelings how the amps sound from each other.


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I hope you don't really mean $50. The amp should have a reasonable cost to build, but I don't think quite that cheap. Just so folks have the right expectations. 
	

	
	
		
		

		
		
	


	


_

 

Duly noted...rather than quote a number, it suffices to say that it cheap enough to build both versions 
	

	
	
		
		

		
		
	


	




 I am staring at two red boards in front of me with great anticipation while listening to the sand version and I am thinking..I just wonder how the tube version will sound. Would it sound as good as this one sounds.or would it be moar to my taste..and if so, I will be completely blown away..not that I am not already..


----------



## runeight

wiatrob is the only one who has both amps running. pabbi1 is close and sachu/ericj are working on it.

 I'll probably build a tube version, but not just yet.


----------



## sachu

I will be in SFO this weekend...I can haul the sand version with me along with my Koss ESP950 if someone wants to listen to it.

 Just give me a heads up..if no interest then I won't take the trouble.


----------



## smeggy

can those output doodads with heatsinks be mounted on the bottom so the tubes poke up through a lid? I wanna see toooobzz!

 Nice work Runeight and posse


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_can those output doodads with heatsinks be mounted on the bottom so the tubes poke up through a lid? I wanna see toooobzz!

 Nice work Runeight and posse 
	

	
	
		
		

		
		
	


	


_

 

They sure can be Smegster..am going to be doing that for mine..I suppose you want me to do the same on your board.

 I wil have to make sure none of the vias are shorting with the heatsinks though underneath the board.


----------



## les_garten

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_They sure can be Smegster..am going to be doing that for mine..I suppose you want me to do the same on your board.

 I wil have to make sure none of the vias are shorting with the heatsinks though underneath the board._

 

Doesn't that make the pinout on the board mirrored? I didn't think it was that easy to flip it over?


----------



## smeggy

just mounting the chips 180deg should work when underneath.


----------



## sachu

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_Doesn't that make the pinout on the board mirrored? I didn't think it was that easy to flip it over?_

 

Depending on which side of the heatsink you mount it can be reversed or unchanged. Only a matter of making sure non of the vias are *not* being shorted by doing so.


----------



## wiatrob

There has also been some talk during proto discussion about air mounting - don't recall the outcome. Socket extenders and 90 degree mounted sinks will get them clear of all the other devices on the board.


----------



## sergery

Man, I can't wait to hear some impressions of the tube version. Maybe a little compare/contrast 
	

	
	
		
		

		
			











 Good work team, keep it up!


----------



## smeggy

I probably wont get to hear the ss version, but I think I'll be happy with the tube one 
	

	
	
		
		

		
		
	


	




 It'll certainly be nice having a proper stat amp again. I'll need to find out what bias and wiring the Koss ESP9 needs. I'd like to have that running on it too.


----------



## n_maher

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_I'll need to find out what bias and wiring the Koss ESP9 needs. I'd like to have that running on it too._

 

From the all-powerful Headphone Wiki:

 Bias = 600V (some have tested them up to 620V, do so at your own peril)

 Pinout
http://wiki.faust3d.com/wiki//index....Out_ESP950.jpg


----------



## wiatrob

For simplicity's sake )and becuase of that god-awful par-metal enclosure on my quick-cased proto) I been setting the pro bias to 580 and not tweaking for individual cans.

 Sachu, what you running at?


----------



## manaox2

I have some Sylvania 6S4A tubes on hand, they should be 6S4 equivalent I believe. Any problems worth noting about using these? (I want to build a SS and tube version).


----------



## sachu

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_For simplicity's sake )and becuase of that god-awful par-metal enclosure on my quick-cased proto) I been setting the pro bias to 580 and not tweaking for individual cans.

 Sachu, what you running at?_

 

650 volts


----------



## spritzer

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_From the all-powerful Headphone Wiki:

 Bias = 600V (some have tested them up to 620V, do so at your own peril)

 Pinout
ImageinOut ESP950.jpg - Wikiphonia_

 

I believe Gary's talking about the older ESP9 he got from me. The bias is around 400v but all the junk in the earpieces will have to be bypassed in order for them to work with any other amp then the E/9. Not only is the pinout different but the entire operational concept compared to the Stax standard. 

  Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_I have some Sylvania 6S4A tubes on hand, they should be 6S4 equivalent I believe. Any problems worth noting about using these? (I want to build a SS and tube version)._

 

Same tube but a higher rated version.


----------



## smeggy

yeah, ESP-9

 It's an odd duck for sure, I would like to run it out of the exstata if possible but if the bias is 400V that may be tricky.


----------



## ericj

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_yeah, ESP-9

 It's an odd duck for sure, I would like to run it out of the exstata if possible but if the bias is 400V that may be tricky._

 

You can absolutely get 400v bias from the eXStata power supply board. Both of the bias supplies are adjustable within a wide range. 

 You can even theoretically get more than two bias voltages in the same box, though never more than two at a time. 

 The bigger question is whether the ESP/9 will sound at all good driven stax-style.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_I have some Sylvania 6S4A tubes on hand, they should be 6S4 equivalent I believe. Any problems worth noting about using these? (I want to build a SS and tube version)._

 

I'm pretty sure that's what I have running on my Woo GES with no problem. I could use an extra set if you decide to sell them.


----------



## wiatrob

I'm running 6S4As currently in the tube board...


----------



## spritzer

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_You can absolutely get 400v bias from the eXStata power supply board. Both of the bias supplies are adjustable within a wide range. 

 You can even theoretically get more than two bias voltages in the same box, though never more than two at a time._

 

You can also just setup the HB supply for a given value and then use a high impedance voltage divider to get any voltage you'd like. It's just 3 resistors so very easy.


----------



## ericj

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_You can also just setup the HB supply for a given value and then use a high impedance voltage divider to get any voltage you'd like. It's just 3 resistors so very easy._

 

There are indeed any number of ways to skin that cat, and yeah, tacking on another voltage divider is one of them. 

 In the basic configuration you have one bias voltage under about 360v and another bias voltage over about 360v. 

 So if you just have regular and pro bias stax, set the low one to 230 and the high one to 580 and you're set. 

 If you had low and high bias stax and an esp950, just use 580 for the esp950 too. Or maybe set it for 590. This isn't many volts difference so it's perfectly ok to just be in the ballpark. I doubt many commercial amps are right on the nose of their stated bias voltage anyway. 

 It's the guy who wants to drive his ET1000, normal bias stax, HE90, and pro bias stax _all at their factory specified bias voltages_ who has to get creative.

 Edit: I really should staxify my Stagnavox this weekend and try it out on the eXStata. Those are, what, 200v originally?


----------



## smeggy

I have the normal and pro stax, ESP-9 and 950 and ET1000 so it'll be a juggling act, need one of those relay boards to set output voltages for me.


----------



## ericj

Well, one option is to determine the difference in the trimpot setting between 400v and 580v on the high side, and then calculate the value of the resistor string you'd have to parallel with the trimpot to allow you to switch back and forth between 400v and 580v. 

 Or if you can find a panel-mount volt meter with a high enough impedance that it won't drag down the bias circuit, use a panel-mounted pot instead of the adjustment trimmer and just adjust the bias on the fly for whichever headphone you're listening to. 

 We've had some difficulty finding panel meters with a high enough input impedance for that, though. 

 I suppose you could pull a SinglePower hack and just gut a cheap DMM.


----------



## insyte

Quick question, is the exstata designed to take in single ended or balanced inputs?


----------



## srserl

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_I will be in SFO this weekend...I can haul the sand version with me along with my Koss ESP950 if someone wants to listen to it.

 Just give me a heads up..if no interest then I won't take the trouble._

 

If you are up for it, I would love to meet and listen. It's a bit of a drive, but it might be fun since I didn't get to attend either can jam or the norcal meet. Nor have I ever met you. This will probably be my next hp amp I will build, and maybe you can talk me into building an ehha as well 
	

	
	
		
		

		
			





 Hmmm, I seem to remember someone warning me about this site and my wallet or some such.

 Scott


----------



## HeadphoneAddict

Quote:


  Originally Posted by *insyte* /img/forum/go_quote.gif 
_Quick question, is the exstata designed to take in single ended or balanced inputs?_

 

Wiatrob's will take both, via input switch on the back.


----------



## ericj

Quote:


  Originally Posted by *insyte* /img/forum/go_quote.gif 
_Quick question, is the exstata designed to take in single ended or balanced inputs?_

 

Yes. 

 If you have balanced input, it takes it. If you only have single-ended sources, you ground the negative input on each amp board. 

 The only difference this should make is 3db less gain in the single-ended configuration - which isn't a problem unless you have a really quiet source.


----------



## sachu

Quote:


  Originally Posted by *srserl* /img/forum/go_quote.gif 
_If you are up for it, I would love to meet and listen. It's a bit of a drive, but it might be fun since I didn't get to attend either can jam or the norcal meet. Nor have I ever met you. This will probably be my next hp amp I will build, and maybe you can talk me into building an ehha as well 
	

	
	
		
		

		
		
	


	




 Hmmm, I seem to remember someone warning me about this site and my wallet or some such.

 Scott_

 



 Sounds good..shoot me a PM and we'll take it from there.

 Oh and yeah...build the EHHA first! 
	

	
	
		
		

		
		
	


	




 Hope that is indicative enough of how highly I think of that amp. 
	

	
	
		
		

		
		
	


	




 By then the details of this amp would've been finalised am thinking.

 Edit:

 I'll see if I can haul the EHHA with me as well...


----------



## les_garten

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Sounds good..shoot me a PM and we'll take it from there.

 Oh and yeah...build the EHHA first! 
	

	
	
		
		

		
		
	


	




 Hope that is indicative enough of how highly I think of that amp. 
	

	
	
		
		

		
		
	


	




 By then the details of this amp would've been finalised am thinking._

 

I had not looked at Alex's amps until this came along. So in looking here I went to Cavalli, the web site, and was interested in the EHHA as an alternative to a B22 build. Both look like awesome amps. How would you compare and contrast the EHHA and B22? What will the EHHA II be? Not much on the site about it.


----------



## sachu

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_ How would you compare and contrast the EHHA and B22? What will the EHHA II be? Not much on the site about it._

 


 The B22 and EHHA are both in my opinion reference quality DIY amplifiers.

 The B22 is the best Solid State amplifier I have heard thus far. To my tastes the EHHA sounds better all around.

 The main area where the EHHA trumps the B22 again IMO is that it costs almost half as much to build (a no frills build) while still equaling or eclipsing the B22 in performance, both power and sound quality wise.

 Keep in mind the EHHA has been around for over 2 years..just hasn't had any exposure till early this year.

 I mean if I had my amp cased up completely I wouldn't mind sending it on a loaner program cause this amp deserves to be heard. 

 The EHHA 2..well ;lets not go there....maybe Alex will get on it after the stat amp is up and running full steam..we can pick his brain about the EHHA 2 after that. AFAIK, the design is for the most part reaedy to go into prototyping phase. But it is a speaker amplifier the likes of the B24. Probably not as high powered as the B24.

 I don't want to derail this thread..we can move this over to the EHHA thread from here on.


----------



## les_garten

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_The B22 and EHHA are both in my opinion reference quality DIY amplifiers.

 The B22 is the best Solid State amplifier I have heard thus far. To my tastes the EHHA sounds better all around.

 The main area where the EHHA trumps the B22 again IMO is that it costs almost half as much to build (a no frills build) while still equaling or eclipsing the B22 in performance, both power and sound quality wise.

 Keep in mind the EHHA has been around for over 2 years..just hasn't had any exposure till early this year.

 I mean if I had my amp cased up completely I wouldn't mind sending it on a loaner program cause this amp deserves to be heard. 

 The EHHA 2..well ;lets not go there....maybe Alex will get on it after the stat amp is up and running full steam..we can pick his brain about the EHHA 2 after that. AFAIK, the design is for the most part reaedy to go into prototyping phase. But it is a speaker amplifier the likes of the B24. Probably not as high powered as the B24.

 I don't want to derail this thread..we can move this over to the EHHA thread from here on._

 

Yeah Thanx! Things were a little slow and the EHHA was mentioned so I ust kinda blurted it out.


----------



## awpagan

It has been a while since i've been to Head-Fi.
 I still have my old LV Stax.
 Will have to keep an eye on this thread.


----------



## runeight

Well, nice to have you back. It has been quite a while. Hang on to your stats because we're almost there.


----------



## runeight

It appears the the hybrid proto builders are not moving along as fast as they had hoped. So, why not post the tube schematic while we're waiting.

 The tube version is very nearly identical to the sand version. It fits on the same board size and uses the same PS and will be completely interchangeable with the sand version provding you have the heater supply. And, if you use the Hammond 270AX transformer its heater supply is exactly what you need.

 Schematic. See below:






 In this case the 6S4 does the high voltage duty that was performed by the KSC5042 in the sand version.

 However, trodes are depletion devices not bjts and we can't make a wilson current mirror with them. So we revert to a standard two-device mirror using 150V transistors. The mirror now drives the cathode of the tube while the grid is grounded. Grounded grid circuits have been around since tubes. The Blue Hawaii uses a GG for its EL34s.

 As before the gain of the amp is still in the hands of the jfets at the input. 

 Hopefully some of the slow-poke prototypers will have news soon. 
	

	
	
		
		

		
		
	


	







 Both boards will be available on the first round (assuming there are no problems with the tube version). Still working on the exact plan to ensure that everyone gets a solid build.

 Stay tuned ...


----------



## insyte

Is the exstata going to be made available as kits?


----------



## DoYouRight

I sure hope so! Bundled with a free pair of 007s


----------



## runeight

It will be either boards or kits or both.


----------



## les_garten

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_It will be either boards or kits or both._

 

I think I'm gonna be a one of each kinda guy!


----------



## insyte

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_It will be either boards or kits or both._

 

Best news for today


----------



## smeggy

This is sooo cool. Can't wait until mine's done. I have all my stats at the ready. It's never been an option for me to have a good stat amp because they all cost so much, this is a real game changer. I'll finally be able to dump the adapter boxes 
	

	
	
		
		

		
		
	


	




 I'm wondering if there will be any chance of the eXStata being able to drive my Sony Electrets as well (ECR 500/600) as that would really make my day. They're awesome but need a buttload of power.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_This is sooo cool. Can't wait until mine's done. I have all my stats at the ready. It's never been an option for me to have a good stat amp because they all cost so much, this is a real game changer. I'll finally be able to dump the adapter boxes 
	

	
	
		
		

		
		
	


	




 I'm wondering if there will be any chance of the eXStata being able to drive my Sony Electrets as well (ECR 500/600) as that would really make my day. They're awesome but need a buttload of power._

 

At RMAF, Dinan said this amp sounded about as good with the O2 Mk1 as his $1000 SRM-717. Power is one thing it has enough of.


----------



## smeggy

I dunno, the Sonys are the like the inefficient orthos of the 'stat world.


----------



## ericj

Driving sony 'trets is unlikely. They require utterly insane voltage swing due to their wide stator spacing.


----------



## smeggy

yeah, the voltage is something else on the ECR. I haven't measured it but I can tell you it stings a *lot* more than any stat I've met.


----------



## nsx_23

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_It will be either boards or kits or both._

 

WIN!

 Hmm, better start saving


----------



## krmathis

I really like how this is coming together.
 Especially now when I have decided to keep the O2.


----------



## spritzer

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_yeah, the voltage is something else on the ECR. I haven't measured it but I can tell you it stings a *lot* more than any stat I've met. 
	

	
	
		
		

		
		
	


	


_

 

I believe the ECR's are along the same lines as Jecklin's (1:125 transformers) but I gave my last adapter away so I can't test it. 
	

	
	
		
		

		
		
	


	




 There is also the extra capacitance to worry about as it will bleed most amps dry so a tough load indeed. I'm sure the new SS Gilmore amp can drive them with maxed out +/-900V rails and a huge CCS to match but we'd need to test it. Not a very cost effective solution though...


----------



## smeggy

well it was a pipe dream but I know they are exceptionally difficult to deal with given their design. One can always hope


----------



## sachu

I am here in SFO with the ESP950 and the sand version of the eXStatA.

 I have two membersinterested in checking it out. PM me for details. PLanning to meet up at the place am staying at around 6 Pm tonight.


----------



## smeggy

How's the weather?


----------



## sachu

its nice and sunny...

 going to go out now..check out the hippie district and ****..


----------



## spritzer

If you want it bad enough then you can use a low ratio transformer to step up the voltages. 
	

	
	
		
		

		
			





 A simple/cheap solution would be to build something similar to Frank Cooters amps i.e. a normal speaker amp with a custom made output transformer.


----------



## smeggy

yah, I'll get right on that...


----------



## wiatrob

Enjoy the weather Sachu! And do let us know how it goes...


----------



## srserl

I just got back from meeting Satchu in San Francisco. I was late arriving due to an accident on the free-way, and more traffic than I expected at the Bay Bridge.
 I took my Cal Audio Labs Icon MkII cd player as a source with some Transparent interconnects. Sachu's eXStata was a sand version and he brought the ESP-950s.

 Here are my quick impressions jumping from album to album quickly, not taking time to take notes and not replaying sections to better describe them.

 First up was Mahler Sym. No. 1 by Chicago Symphony Orchestra, Sir George Solti directing. Ho hum...nothing special, but this album has never struck me as great. 
 I quickly changed to Folger Consort, This England and wow! I have never heard this sound so pretty. It was open and clear and the parts just played against one another with plenty of air...it was truly great. 
 Next up, I wanted to see how the ESP-950 handled some bass, and how much impact it had. So, I threw in Bella Fleck and the Flecktones, Flight of the Cosmic Hippo. This sounded pretty good, and the bass had good presence and impact. I wish I had brought some good organ music to try, but I didn't. 
 Next I put in Stuck Mojo (big shift in genre), Rising. Drums have really good impact. There is a sound in the song "Assasination of a Pop Star" that is VERY low, containing some sub-sonics. With a superb speaker system, or at least one with a good sub woofer, this sound makes me a little queazey, and on my Grado HF2 out of the CTH, the sound is very present, but the ESP-950 barely registers this sound. So, they go low, but not LOW.
 Korn, Issues, was up next. I really didn't like this album played on this system; it was just kind of flat and harsh (somehow it managed to be both at the same time).
 Then I put on Joe McGuinness, From These Seeds. The acoustic guitar had great attack with a great plucked string sound and it sounded great until the vocal came in, then it sounded very boxy.
 So, in goes Sublime's self titled album. Starts out great, then when the vocal comes in, it's that boxy sound again. I can hear it a bit on my HF2 as well, but the eXStata and ESP-950 just put a spotlight on it.
 Finally I put in Eric Clapton, Unplugged. This album was absolute magic! It's a good album, but I have never heard it this good. The live ambience on this album just opens up wide and swallows you.

 Conclusion after a short listening session:
 This combo seems merciless with inadequate recordings, but did not have a sound that I would describe as overly analytical. It wasn't that it was hyper detailed, but it would just shine a spotlight on certain parts of the music that were flawed. On Eric Clapton and Folger Consort, it was spectacular. Considering that this system could be put together for about $600 if you pick up the ESP-950 used, it would be a shame NOT to build it. That's pretty cheap for a system that offers up so much wow factor, even if most recordings can't cut it.

 Thank you Sachu for hauling your system all the way from Portland so I could hear it.

 Scott


----------



## pabbi1

Sand and tube variants operational:


----------



## wiatrob

You've got my ghetto wiring beat! Congrats Al!


----------



## pabbi1

I hate how the camera flash exagerates fingerprints, etc. And waffling on powdercoating the top, but details, details.

 Big nod to smeggy for the feet design - as overblown as they are - built in the brick shiitehouse fashion, but also to help isolate from source on vibe and to allow ventilation, not that this runs all that hot.

 Three down, two to go. Raven on the bench.


----------



## les_garten

*@Pabbi1* Is your day job in a lumbar yard?


----------



## Emooze

Do you have any impressions on the differences in sound between the two?


----------



## dBel84

Looking good pabbi , taking this one came up without the fanfare 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## wiatrob

Knowing Al, he will be waiting for burn in before commenting...


----------



## wiatrob

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_Looking good pabbi , taking this one came up without the fanfare 
	

	
	
		
		

		
		
	


	




 ..dB_

 

or Fireworks!


----------



## pabbi1

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_Looking good pabbi , taking this one came up without the fanfare 
	

	
	
		
		

		
		
	


	




 ..dB_

 

Me - have a drama free build? Uh... 

 Nope - ordered runeight extra digitalis. If I would ever learn to follow directions, or somesuch, oh, and not work on HV when I am not well rested. But, everyone else will benefit with better directions from my boneheaded wanderings, and one day, I swear, I will learn V from mV. 
	

	
	
		
		

		
		
	


	




 Most any stupid things a builder can do have already been done. And, amazing how FORGIVING the design is, especially in casing. To wit, I have a tube and heatsink literally touching a pot, with no buzzing and sparks. Will remedy this, but, just a testiment to the design.

 I have a couple of other designs that are, well, less forgiving.

 BTW, my day job is International corporate taxation (more planning than compliance), and I just think it is as easy to work with really nice wood if you are going to bother, since I (over) value my hobby time. Actually I spend a small fraction on wood compared to DIY components. Faceplate is Honduran rosewood, the back and sides are Limoncilla , and the feet black walnut (literally glued scraps), which is about $30 in wood, all told.


----------



## wiatrob

Woodcraft Al? I need to case my hybrid, too...


----------



## pabbi1

Woodcraft for Limoncilla (never seen it anywhere else, and it is being closed out).

 Rosewood from Cook Woods on eBay - scrap from my Raven case, iirc. That is where I get almost all my exotics, except for faceplates, which seem to come from a guy in Buffalo, NY (search on 'thin lumber') especially Bloodwood.

 Walnut from Woodworld in Dallas - we have just an excellent resource in those guys, except they seem to miss out on Mesquite (Woodcraft for that), which is my favorite wood to work with. They do keep me well stocked in Bocote, Cocobolo, and the lesser exotics (mahogany, etc).

 Oh, and Siberian elm for earcups only because I can't find Zelkova - again eBay.


----------



## smeggy

Nice work, looks good. I'm itching to get mine, it's gonna be great


----------



## Sherwood

eXStata is in the house! I'll be playing with it a lot this weekend. Don't expect much in the way of impressions -- I listen to enjoy, and you already know how I feel about this thing.


----------



## runeight

Quote:


  Originally Posted by *srserl* /img/forum/go_quote.gif 
_I just got back from meeting Satchu in San Francisco. I was late arriving due to an accident on the free-way, and more traffic than I expected at the Bay Bridge.
 I took my Cal Audio Labs Icon MkII cd player as a source with some Transparent interconnects. Sachu's eXStata was a sand version and he brought the ESP-950s.

 Here are my quick impressions jumping from album to album quickly, not taking time to take notes and not replaying sections to better describe them.

 Snip..

 Conclusion after a short listening session:
 This combo seems merciless with inadequate recordings, but did not have a sound that I would describe as overly analytical. It wasn't that it was hyper detailed, but it would just shine a spotlight on certain parts of the music that were flawed. On Eric Clapton and Folger Consort, it was spectacular. Considering that this system could be put together for about $600 if you pick up the ESP-950 used, it would be a shame NOT to build it. That's pretty cheap for a system that offers up so much wow factor, even if most recordings can't cut it.

 Thank you Sachu for hauling your system all the way from Portland so I could hear it.

 Scott_

 

srserl, thanks for the review and for making it through traffic to do it!! 
	

	
	
		
		

		
		
	


	




 And sachu, thanks for hauling it to and through SFO.


----------



## smeggy

Damnit!! You got yours before I got mine.. Bah, I tells ya, bah!


----------



## manaox2

Quote:


  Originally Posted by *Sherwood* /img/forum/go_quote.gif 
_eXStata is in the house! I'll be playing with it a lot this weekend. Don't expect much in the way of impressions -- I listen to enjoy, and you already know how I feel about this thing._

 

I H8 ur face.


----------



## wiatrob

No, he got *MINE *- it's the Sand version. Purely a loaner I tell you. Help him make up his mind to take the plunge to build one...


----------



## smeggy

Oh, so that slacker hasn't even committed yet?

 man, what a loser...


----------



## pabbi1

Notice Bill didn't loan him the tube version - I'm not real surprised...


----------



## smeggy

Hmm, that sounds promising


----------



## wiatrob

It's only because I'm still tweaking. Unplug the Electrets yet, Al?


----------



## pabbi1

HE60 has been plugged in for about 5 hours now... really sweet. I have found some of her limits, so she isn't perfect - but only on the most brutal, saturated selections. I knew these passages were well beyond her design spec, but she is still a trooper.

 Let's just say I know what 800Vpp sounds like...


----------



## ericj

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Walnut from Woodworld in Dallas - we have just an excellent resource in those guys, except they seem to miss out on Mesquite (Woodcraft for that), which is my favorite wood to work with. They do keep me well stocked in Bocote, Cocobolo, and the lesser exotics (mahogany, etc).

 Oh, and Siberian elm for earcups only because I can't find Zelkova - again eBay._

 

I remember when mesquite was a weed! They used to pay people to clear it off of grazing land out here in the dry west. Poisonous for the livestock, iirc. 

 One of the guys who used to get paid to drag a chain between two big earth movers and then go back and clean up the resulting mess got smart and started *selling* the stuff. This was only, what, 25 years ago? 

 I still need to case up my sand amp, and my hybrid is almost up! I'll be firing it up and dialing it in come morning - it's too late for high voltages now. 

 My biggest impediment to casework is lack of tooling. One of these days my friend with the tablesaw and drill press and everything will run out of emergencies and be able to actually set up his shop - at which point i may start using wood. 

 For my sand amp i have a recycled aluminum box onto which I think I'll get a length of 1/8" aluminum extrusion from online metals for the face. 

 The hybrid amp is going into something bigger - you all know i don't go for the bottlehead look - and the recycled case i plan to use for that is going to need a new face too. Haven't decided how to tackle that yet.


----------



## smeggy

Sadly my fave case wood is macassar ebony, it's too damn expensive!


----------



## les_garten

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Sadly my fave case wood is macassar ebony, it's too damn expensive!_

 

Agreed, I had a SOTA Star made out of that and it was Beautiful!


----------



## wiatrob

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_
 Let's just say I know what 800Vpp sounds like... 
	

	
	
		
		

		
			



_

 

Oh, I think there might be a way around that (he says cryptically)


----------



## Sherwood

Got it up in the computer rig right now fed balanced by a DACmagic and an E-MU 0404 -- holy hell. This thing is a tone monster. Great instrument placement, great dynamics, great soundstage, great everything. I'm in to build one, without a doubt. This sounds significantly better than my Normals out of a transformer through the Moth EC2a3, which is a great amp.

 FUN!


----------



## ericj

Currently burning in:


----------



## smeggy

Excelent work, eagerly waiting on more tubey impressions when ready


----------



## manaox2

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Excelent work, eagerly waiting on more tubey impressions when ready 
	

	
	
		
		

		
		
	


	


_

 

X2!


----------



## pabbi1

Well, since I am actively working on other amps while listening, I really can't add much, save that we are tweaking as we hear certain things.

 For 98% of what I am aware of, the voltage swing will be more than sufficient. Where we are identifying it is not, work is still being done to add headroom.

 I am going to also defer to others next weekend to offer brutally honest impressions without me guiding any opinions or impressions. Gonna turn them all on, and let others have at it. 

 It is journey.


----------



## ericj

With only about 8 hours of burn-in, this amp sounds great to me. For one thing, even with the crazy rats nest of wiring on the workbench, it's dead quiet. 

 I've got it hooked up single-ended to my EMU 0404 pci card, through the entirely passive tape loop output on the Rotel RA-820bx you see in the picture above. The tape loop and input selection work the same when the rotel is turned off, so it's probably just a resistor divider. 

 I know the 0404 is actually a balanced source, but i don't have the right cables to hook it up that way. I could make those cables, but the 0404 is my _only_ balanced source. I don't foresee ever putting a set of XLRs on the backs of these enclosures, at least not for my own use. Performance with single-ended input is most important for me. 

 By the way, although you see three transformers in the picture above, only the black Hammond is hooked up right now. The two triads are for the sand amp. At present I'm using the PS board i built for the sand amp so that i could get the tube board up and running faster. I've since completed the 2nd PS board and will bring it online tomorrow night. 

 The triads together are about $10 cheaper than the hammond. They have twice the HV current of the hammond we're using for prototyping, but lack the heater winding.


----------



## smeggy

Thanks Eric. 
 I was wondering whether the Hammond 380(?) might be a better transfo for this, it's not much more expensive but supposedly a significantly better transformer. I doubt it's necessary but you never know. Well, I don't anyway


----------



## ericj

bigger iron is being considered for the hybrid amp. The triads offer far more current than the SS amp needs - if people prefer to use a hammond for the SS amp, though, it does work - iirc sachu had one up for a while that way. You waste the heater winding, but that's no big deal. 

 There are probably some good toroids and R-cores that work too - these are just what we're prototyping with. The triads are super-economical, though.


----------



## smeggy

I guess being somewhat of a fashion victim I'd ideally want a transfo that's both powerful and reasonably good looking for top mounting. I'm only getting the tube version and it'll have bottom mounted sinks so the tubes can go out the top as well. I'd like it to look stylin' and those triads, cheap and powerful as they might be, are ugly as all hell.


----------



## sachu

Finished everything except the heatsink mounted transistors. Can't seem to locate the heatsink compound. Will get to it tomorrow.

 Transformers should arrive in a couple of days so I get get the two additional PSUs fired up.

 Edit:

 Smeggy, I have two Hammond 269JX transformers for our builds.

 They have marginally higher voltage secondaries and current than the standard 270AX Hammond. BUt Still very doable. They were about as cheap as the Triads on ebay and were difficult to pass up for the price..


----------



## smeggy

excellent news sachu. On another front, I've figured out a nice way to do the removable baffle. It's part way there and It's a hassle but should work well


----------



## wiatrob

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_I guess being somewhat of a fashion victim I'd ideally want a transfo that's both powerful and reasonably good looking for top mounting. I'm only getting the tube version and it'll have bottom mounted sinks so the tubes can go out the top as well. I'd like it to look stylin' and those triads, cheap and powerful as they might be, are ugly as all hell._

 


 You won't have to worry about it if you go tubed (you get a ugly hammond!) - but the Triads do present an opportunity for cool trafo covers :^)


----------



## ericj

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_You won't have to worry about it if you go tubed (you get a ugly hammond!) - but the Triads do present an opportunity for cool trafo covers :^)_

 

haha. 

 I'm surprised those triads come with case mounting tabs. I've seen that style of transformer in gear before - usually all those tabs sticking out the side are neatly embedded in a circuit board.


----------



## luvdunhill

looking nice guys!

 The best I can tell, there is somewhere around 20 different 6S4A construction variants. Does anyone have any tube preferences yet? 

 I'm looking around for one odd ball to complete a construction matched octet, perhaps someone might be willing to see what they have on hand?


----------



## n_maher

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Thanks Eric. 
 I was wondering whether the Hammond 380(?) might be a better transfo for this, it's not much more expensive but supposedly a significantly better transformer. I doubt it's necessary but you never know. Well, I don't anyway 
	

	
	
		
		

		
			



_

 

For my money I'd definitely run a 300 series Hammond. In my experience they are functionally much better than their similarly spec'd 200 series counterpart and as you said, not that much more $$.


----------



## pabbi1

I have Tung Sol in the eX and Amperex in the Vulcan... 
	

	
	
		
		

		
		
	


	




 Doubt many of us will be rolling tubes any time soon, as other changes will be in the offing first.


----------



## runeight

I know that many of you have been waiting for more information on boards and/or kits.

 We now have at least five sand amps and three tube amps working. So we know that others can build the amp besides me and wiatrob. 
	

	
	
		
		

		
		
	


	




 I have been discussing how to take the next step in releasing these with wiatrob who'll be doing most of the work getting the kits together.

 I'd like to make a limited release right at this moment because I'd like a few more amps in, what we might call, a beta release. I also want to be able to fully support the builders and, despite the fact that this amp is a pretty easy build, the 600V rail to rail voltage is something we need to be deliberate about.

 The other thing I'd like to avoid is a mish-mash of parts that might be cobbled together from parts boxes and surplus stores, etc. At least for this first release. Harder for me to support if this happens.

 So, I'd like to make 10 of each board available along with the PS. That's 10 amp boards (both channels) and 10 tube boards (both channels) each with its PS board.

 I'll make a limited run of PCBs for this. Thus, they will be slightly more expensive than if I had ordered 100 or more.

 I will handle the group buy for the boards. Only one set per person.

 What will be helpful is if the first 20 folks will get to their builds as quickly as possible to provide feedback on this beta run. So if you sign up, we're counting on you. 
	

	
	
		
		

		
		
	


	




 wiatrob will offer kits based on sign ups, probably pre-paid. He will have information on this towards the end of the week.

 It is my preference that you buy these kits for reasons stated above. Just to control the part selection. They will priced to cover costs and shipping.

 In the next week or so I'll post the website and start adding additional information for building and setup.

 Then if this phase works out, we can offer a more general release that I can manage with the time that I have.

 Your ideas are most welcome.

 After you guys have posted comments, assuming that there are any, I'll start soliciting the PMs.


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_We now have at least five sand amps and three tube amps working._

 

Hope to make that 5 out of 5 for the tube amps tonight


----------



## les_garten

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I know that many of you have been waiting for more information on boards and/or kits.

 We now have at least five sand amps and three tube amps working. So we know that others can build the amp besides me and wiatrob. 
	

	
	
		
		

		
		
	


	




 I have been discussing how to take the next step in releasing these with wiatrob who'll be doing most of the work getting the kits together.

 <<SNIP>>_

 

Hi Alex,
 I guess it's reasonable to assume then that these boards are pretty much a final design?


----------



## runeight

Why yes. One of the reasons I've been taking this slowly.

 There may be one resistor tweak, but the board layouts won't change because of it.


----------



## manaox2

You guys are doing a tremendous job. 
	

	
	
		
		

		
		
	


	




 Do I ever wish I had the time to participate right now.


----------



## smeggy

Indeed! It's a great time to be a fairly broke 'stat fan


----------



## HeadphoneAddict

The big question for me is - do I add the eXStata to my GES and have two amps for different flavor electrostatic headphones, or sell the GES and some other stuff for the WES? (see RMAF impressions thread if I didn't put all my eXStata impressions in here).

 Like I said before, I liked the timbre and tone of the GES better, but the power, soundstage and separation of the eXStata a little more. To me the WES combines the best of both in one amp.


----------



## sachu

we have 4 out of 5 tube amps running now 
	

	
	
		
		

		
		
	


	



 Though there is some offset problem which I will check on later, the board seems to be balancing out to 0 nicely.


 Smeggy's tube board is prepped and ready but too lazy to hook up now..and with cold solder joint problems due to the haste in which i put my board to gether I want to cehck and reflow any such bad joints on Smeggy's boards tomorrow before firing it up. 
 Some work left on the two PSU boards and waiting for some zeners due to arrive on wednesday by which time I plan to get some casework done for my tube amp...its all slowly coming together.


----------



## Emooze

What is everyone using for pots? I'm assuming they are wired between the inputs and the boards from what I've seen.


----------



## ericj

I'm using a 10k noble i picked up years ago, spliced in between some lengths of shielded 22awg silver-plated. 

 If you're going for balanced input, you will need two stereo pots or attenuators, or a four-deck pot or attenuator. Or some other magic I'm unfamiliar with.


----------



## sachu

and now we have 5 out of 5 tube amps!! 
	

	
	
		
		

		
		
	


	




 I'll bet Smeggy is itching to get his hands on this, as he should. 

 2 remaining power supplies will be brought up tomorrow or the day after at the latest at which time I will ship one set out to Smeggy.

 Congrats Alex!! Thanks for such a wonderful amplifier.


----------



## smeggy

Actually, that's 'another' wonderful amplifier.


----------



## les_garten

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_









_

 

If I were you, I'd be sportin' a smile as well!


----------



## Sherwood

Shoot, Smeggy, I've had this loaner up all weekend


----------



## runeight

There have been only a few comments since my post about the diy beta build. I assume this is because some of you felt that the process was ok and are ready to go and some of you didn't and decided to not make a fuss over it. 
	

	
	
		
		

		
		
	


	




 So, those of you would like to be part of the beta-builder team please PM me. If there is enough interest we'll go forward.


----------



## srserl

I am willing to build one and have the time right now, unfortunately I don't have any headphones to test it with. So, I guess I will wait for a later time to build one.


----------



## Keithpgdrb

I figured I would get in on the final build, as I am fairly new to diy. I'm unsure if this would make a smart first build. Plus, you asked for people to get the
 beta build done quickly. Don't think I could help on that front. I know I'll be in for this though.


----------



## smeggy

I woulda been on it if sachu hadn't _insisted _on 'saving me' from killing myself by building it for me... for some unknown reason he feels I'm a menace around electricity just because I blow everything up.

 I feel my rep is entirely besmirched by these ridiculously unfounded insinuations..... just because sachu builds amps that work and I don't. 

 Pfft. 

 Oh, has anyone got any matches I can have? these damn wires from falling out of the wall socket.


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_I woulda been on it if sachu hadn't insisted on 'saving me' from killing myself by building it for me... for some unknown reason he feels I'm a menace around electricity just because I blow everything up.

 I feel my rep is entirely besmirched by these ridiculously unfounded insinuations..... just because sachu builds amps that work and I don't. 

 Pfft. 

 Oh, has anyone got any matches I can have? these damn wires from falling out of the wall socket. 




_

 


 haha..lets see..
 1 stacker amplifier blown up - check
 1 beta 22 amplfiier blown up..twice - check
 1 CTH made non functional - check
 1 EHHA blown up - check...

 gee...wonder what made me think you would kill yourself.. 
	

	
	
		
		

		
		
	


	







 and that too before you send me the thunderpants


----------



## smeggy

but the starving student is still going


----------



## sergery

The problem is I can afford an amp right now, but the headphones... not so much :'( Also I gotta finish sorting out this M3. Pity, I would love to build this amp.


----------



## Sherwood

Well, hell, if it's life or death for this baby, I'm on board. Count me in, Alex. This is the most complex thing I've ever attempted, but i have Bill to drive me to the hospital if need be.

 Woo!


----------



## smeggy

Yay, way to go sherwood


----------



## HeadphoneAddict

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_There have been only a few comments since my post about the diy beta build. I assume this is because some of you felt that the process was ok and are ready to go and some of you didn't and decided to not make a fuss over it. 
	

	
	
		
		

		
		
	


	




 So, those of you would like to be part of the beta-builder team please PM me. If there is enough interest we'll go forward._

 

I can't read a schematic so I'd have to persuade Wiatrob to build mine, and I have not heard ANY impressions of the tube version that I am most interested in. So, I'm kinda in an unknown place right now.


----------



## wiatrob

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_I can't read a schematic so I'd have to persuade Wiatrob to build mine, and I have not heard ANY impressions of the tube version that I am most interested in. So, I'm kinda in an unknown place right now._

 


 Impressions of the tube version have been slow coming - Al and I are deferring ours to other ears. I'm sure Sachu and Eric will pipe up when they have had time to compare.

 I'll loan you mine as soon as it's cased, if you'd like...

 -Bill


----------



## pabbi1

I am deferring comment until after others have heard it at the Houston meet this weekend. Then, I will post a full review in the Amp section. It is, after all, and amp, or amp design with two variants, of which I have both.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Impressions of the tube version have been slow coming - Al and I are deferring ours to other ears. I'm sure Sachu and Eric will pipe up when they have had time to compare.

 I'll loan you mine as soon as it's cased, if you'd like...

 -Bill_

 

Cool. I would like that very much. The Stax O2 & SR-404 LE, Jade and HE60 on the SS eXStata beat the K1000 on the EHHA or SAC amp, so I'm not sure yet if I'm keeping my K1000. The eXStata seems to hold my interest more because it will be much cheaper to add an eXStata to my GES than to sell the GES and K1000 to put towards a WES. Decisions Decisions...

 Also, I was hoping to drive up to Denver Sunday to see my father-in-law with my wife to wish him Happy Birthday (was today), and I'd like to return your EHHA to you while I'm up there. PM or call me so we could arrange something.


----------



## bada bing

I've sent in a PM request to be included, hope I make the "cut".
 If there are more Beta tester's than boards, this is still intended for a general release later ?

 I'm wondering about sharing a single PSU between a sand amp and a tube amp, all in the same chassis. What are the downsides ? I have an extra "Nabu" case, which should be an adequate size ?


----------



## sachu

Quote:


  Originally Posted by *bada bing* /img/forum/go_quote.gif 
_I'm wondering about sharing a single PSU between a sand amp and a tube amp, all in the same chassis. What are the downsides ? I have an extra "Nabu" case, which should be an adequate size ?_

 

I had the same thought..but seems the PSU is speced for just one amp board. Having both means having 2 PSU boards. Also you will need a bigger transfromer.


----------



## n3rdling

Well, I've never built an amp before so I was a bit worried about killing myself with this build and ended up buying sachu's SS build. I will try to give you guys impressions on how this amp stacks up with my SRM1mkII/T1/T1S/717 via the SR5/Lambda/Lambda Sig/Sigma/Sigma pro/O2/HE60. I always try to give completely honest impressions, so hopefully they serve some use for both developers and potential builders.


----------



## manaox2

Quote:


  Originally Posted by *n3rdling* /img/forum/go_quote.gif 
_Well, I've never built an amp before so I was a bit worried about killing myself with this build and ended up buying sachu's SS build. I will try to give you guys impressions on how this amp stacks up with my SRM1mkII/T1/T1S/717 via the SR5/Lambda/Lambda Sig/Sigma/Sigma pro/O2/HE60. I always try to give completely honest impressions, so hopefully they serve some use for both developers and potential builders._

 

Thank you! I'm really looking forward to it.


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_There have been only a few comments since my post about the diy beta build. I assume this is because some of you felt that the process was ok and are ready to go and some of you didn't and decided to not make a fuss over it. 
	

	
	
		
		

		
			





 So, those of you would like to be part of the beta-builder team please PM me. If there is enough interest we'll go forward._

 

Runeight, Sent you a PM earlier this morning. Didn't know if you got it? Anyway, I can build one of these and would be interested in participating in the beta build. Would be interested in building the hybrid version, as I just completed building a P2P KGSS a few months back. I have the ESP950's for testing. Let me know if you still need diy beta builders and what details are involved. I can get parts from Mouser in one day here in Texas. Tubes are 3 days away. Thanks, Tommy.


----------



## webbie64

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_
  Quote:


  Originally Posted by *n3rdling* /img/forum/go_quote.gif 
Well, I've never built an amp before so I was a bit worried about killing myself with this build and ended up buying sachu's SS build. I will try to give you guys impressions on how this amp stacks up with my SRM1mkII/T1/T1S/717 via the SR5/Lambda/Lambda Sig/Sigma/Sigma pro/O2/HE60. I always try to give completely honest impressions, so hopefully they serve some use for both developers and potential builders.

 

Thank you! I'm really looking forward to it._

 

Absolutely. X2. Very keen to read your impressions.


----------



## ericj

We do still need a few beta testers, and be clear: This design is essentially complete. Some resistor values and recommended test point readings might get changed.

 We just need to assemble more group experience - for which there will be few enough builders concurrently that runeight can give sufficient personal attention.

 For the hours that we've been able to run our prototypes it's been a very stable and good performing amp. But we only have, what, five of each? And know relatively little about what can go wrong when the builder makes a mistake. 

 I work in software quality - where we break things intentionally. Nobody wants to build an amp wrong on purpose, but sometimes it gets built wrong anyway.

 So far I've personally discovered that reversing the zener that protects the positive power regulator fet doesn't kill anything if it's a brief error.

 Tomorrow i get to figure out if i killed anything by powering up my 2nd ps with the N and P channel fets swapped.

 I didn't intend to do that, but the way the power supply board goes together it made the most sense to me to mount the transistors on their heatsinks finger-tight, get the legs aligned in the board, then torque down the nuts good and tight. Which involved taking them back off the board and then putting them back on to solder them in finally.

 And i guess i wasn't careful enough when i stuck them in the board the last time. Too much confidence from having mostly built the other three boards free of drama.

 There really aren't bugs to be worked out of this design. We're at the tuning phase, and we need to have a better idea of how successfully other people can build them before boards go into full production.


----------



## dracoV

I've been following this since the old thread, really glad to see it come to life. 
	

	
	
		
		

		
		
	


	




 I've been itching to go for an electrostatic for quite a while; the only thing
 that keep me from doing so is IT need a good electro-amp which cost quite a lot. 
	

	
	
		
		

		
		
	


	




 Now there's a reasonable one to build. 
	

	
	
		
		

		
		
	


	




 can't wait to build one.

 It seem runeight's design often catch my interest. Cheers,


----------



## sergery

OK, on board for a beta build. My interest got the best of me. I decided to just scare up some cheap tester stats - I think anyone else in my position might consider this route also. LET'S BUILD SOME AMPS!
	

	
	
		
		

		
		
	


	




 cheers
 serge


----------



## Emooze

I put my name down as well. Was going to buy a DAC before I looked at another amp but this is worth the change of plans.


----------



## DouglasQuaid

If it's for the good of the DIY forum, I could put one together. It'd be nice to put it up against my KGSS once it's done.


----------



## wiatrob

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_We do still need a few beta testers, and be clear: This design is essentially complete. Some resistor values and recommended test point readings might get changed.

SNIP

 There really aren't bugs to be worked out of this design. We're at the tuning phase, and we need to have a better idea of how successfully other people can build them before boards go into full production._

 

Agreed - all good points Eric...

 I think another thing we're looking for are different sets/types of sources than the proto team had. 

 Is anyone who's thinking of building a Beta Build considering balanced or SE inputs, Hig or Mid or Low end sources? (We noticed at RMAF that this amp is particularly revealing of source strengths, weaknesses and quirks...) Different cans? 

 It might be good to compile a list of these, and apply some of that QA matrix testing i bet eric is familiar with. That way, insteaf of guessing how the amp will perform with a particular set of gear, we might have some evidence of performance or indications of problems with any givin setup. 

 AFAIK (and I know you all will be qucik to correct me if I'm wrong 
	

	
	
		
		

		
		
	


	




), this slightly more rigorous testing has yet to be done for head-fi DIY. And I think it could be very valuable...


----------



## Emooze

I have a pair of Lambda Nova Signatures on the way. Looking at SE inputs with a low end source. Like I said, it'll be running out of my laptop, decent but very noisy, until I buy a DAC. The DAC I have my eyes on is the Valab NOS DAC.


----------



## runeight

Folks, I'd like to post the current tally of beta builders to the thread. We don't have quite enough builders yet and, in the meantime, I wanted to ask your review to see if I have the right board allocated for you.

 If any of you who have contacted me with PMs don't wish to be listed please send me another PM.


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Folks, I'd like to post the current tally of beta builders to the thread. We don't have quite enough builders yet and, in the meantime, I wanted to ask your review to see if I have the right board allocated for you.

 If any of you who have contacted me with PMs don't wish to be listed please send me another PM._

 

Runeight, Put me down for the hybrid, which I'm pretty sure you already know. 
	

	
	
		
		

		
		
	


	




 Ready and waiting for the boards/details.

 Thanks, Tommy


----------



## smeggy

has this been bandied about it the stax and koss threads yet? If not, it needs to be.


----------



## awpagan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Folks, I'd like to post the current tally of beta builders to the thread. We don't have quite enough builders yet and, in the meantime, I wanted to ask your review to see if I have the right board allocated for you.

 If any of you who have contacted me with PMs don't wish to be listed please send me another PM._

 

As I've already pm'd to join in on the fun.

 How many builders do we have and how many more do we/you need?


----------



## runeight

I'm getting ready to post the list. Just wanted to be sure if there was anyone who wanted his participation to remain quiet. If I don't get any PMs by later this afternoon, I'll post the list.


----------



## studeb

i volunteered earlier
 SE build please.
 Tube or SS no preferences.
 Sources? multiple
 i can audition it locally (San Diego) when it is completed also.


----------



## runeight

Folks, my apologies for the delay. Thanks for your patience.

 I've waited in order to get a few more pieces of feedback on the amp's performance. As a result, I am thinking that I would like to make a change to the amp. Let me explain.

 To keep within the original target of easy-to-build and modestly priced, I designed the amp to perform well to about 700Vpp. We thought (I thought) that this is a good target for an entry-level stat amp. The amp actually makes somewhere between 700V and 800Vpp.

 However, some of the listening sessions are showing that even "beginning" setups want more output voltage. We can do this with a modest change to the amp.

 In the explanation you'll recall that I talked about not using CCSs for simplicity and to get 700V (even a bit more) we don't really need them. But to allow the amp to get closer to the PS rails we do need CCSs on the emitter followers.

 I think I'd like to add these to the amp boards. Hardly any additional cost and not much additional complexity. Not counting parts that are simply swapped and not added this mod will add four TO92 transistors, four KSC5042 transistors, and four of the smaller heatsinks as used in the PS. The board will grow about 20mm to be 170mm wide.

 With this change the amps will make closer to 1000Vpp before starting to clip. This is added headroom that seems to be needed even for a starter amplifier.

 I am confident enough in that this change will work that I am willing to make a batch of boards for the beta team with the new design. If you get your amp working then you can pay for the board, if the mod doesn't work I'll refund your $$$ for the boards. 

 I will build one of the amps (probably the sand amp) to verify that it works. If it does then I'll ship you boards.

 If you all are comfortable with this let me know. We still don't have enough beta testers to make an economical board run but one or two of you have said that you would be willing to cover the gap if needed. Please let me know if you will still consider doing this.

 This will be a better amp and will allow to drive more difficult-to-drive headphones.


----------



## runeight

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_
 I am confident enough in that this change will work that I am willing to make a batch of boards for the beta team with the new design. If you get your amp working then you can pay for the board, if the mod doesn't work I'll refund your $$$ for the boards. _

 

Not exactly how I wanted to say this. 
	

	
	
		
		

		
			





 What I meant is that if it is the mod that prevents successful build then I'll refund the $$. If you just mess up (after I know that the build works) well then ... you'll have to fix it.


----------



## audionut

Runeight, I'm still on board for the hybrid. Will you be sending each of us a PM to get our shipping addresses for boards? Also, how will final schematics, parts list be provided? Just curious. Thanks, Tommy


----------



## Emooze

Count me down as still interested


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_This will be a better amp and will allow to drive more difficult-to-drive headphones._

 

From a casual observer, all the _really_ hard work is done, so this seems like a pretty reasonable addition to me 
	

	
	
		
		

		
		
	


	




 Out of curiosity, what is the 'final' size of the amp and PSU boards?


----------



## runeight

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Runeight, I'm still on board for the hybrid. Will you be sending each of us a PM to get our shipping addresses for boards? Also, how will final schematics, parts list be provided? Just curious. Thanks, Tommy_

 

Yes, once I place the board order I'll start notifying everyone. But before that, after I get feedback on this latest change, I'll post the list of beta-testers to verify everyone one last time.

 I have created a section on the Cavalli Audion website for this amp. It will have all of the information needed to build, including the parts lists and BoMs. As soon as we settle the beta group I'll start to make this available.

 Thanks emooze. 
	

	
	
		
		

		
		
	


	




 Beefy the amp board is now 170mm x 95mm. The PS is still 110mm x 100mm. PS does not change in this transaction.


----------



## sergery

So you are asking if we mind ~25% more power?
	

	
	
		
		

		
		
	


	










 The way you describe it, it sounds like a good move to me
	

	
	
		
		

		
		
	


	




 how much $$$ will it add to the BOM? Any foreseeable downsides like stability?


----------



## runeight

It won't add very much cost. Four KSC5042s, four BC550C (2N5550 for tube version) and four heatsinks. Less than $10 worth of additional parts because the three resistors in the new CCS are swapped for the three resistors that are there now (probably cheaper too).

 The particular CCS that I have in mind has already been tested in the first version of this amp (and in zillions of other designs). The amp design in the firs thread failed, but the CCSs worked exactly right. This is why I'm fairly confident that there won't be problems.

 But, I will build the first one. If the mod causes a problem you guys are off the hook. If not, then you'll have to get moving on your builds.


----------



## runeight

So you'll know, this is what we will do.






 The CCSs will push a little over 3mA into the followers which is about what the resistors are doing now.


----------



## luvdunhill

Alex:

 What sort of load did you throw at the amp when you were testing it? 

 Everyone was quick to dismiss my request for measurements at the start of this thread, perhaps now it would be useful to post / discuss them?


----------



## smeggy

What kind of price are we looking at for the new boards (not full bom) as even if I don't build one myself I'd like to support the project.


----------



## runeight

I didn't have the amp for very long. Most of the rest of builders tried various headphones. Even so, I knew that the amp would not make more than somewhere between 700V and 800Vpp and I think it is being driven past this during some of the listening. This because there is enough headroom in the PS for the amp to go beyond these limits.

 But, I'm pretty sure that the capacitance load is not the source of the clipping. It is the followers cutting off from lack of current on the larger voltage swings. 

 Nonetheless, I'll have this version for a bit longer this time and can, hopefully, check it out more.


----------



## runeight

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_What kind of price are we looking at for the new boards (not full bom) as even if I don't build one myself I'd like to support the project._

 

I'll have to get a quote, but I THINK I can keep the cost for one amp and one PS to less than $50 for a small run of boards.


----------



## smeggy

I'm in then


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I didn't have the amp for very long. Most of the rest of builders tried various headphones. Even so, I knew that the amp would not make more than somewhere between 700V and 800Vpp and I think it is being driven past this during some of the listening. This because there is enough headroom in the PS for the amp to go beyond these limits.

 But, I'm pretty sure that the capacitance load is not the source of the clipping. It is the followers cutting off from lack of current on the larger voltage swings. 

 Nonetheless, I'll have this version for a bit longer this time and can, hopefully, check it out more. 
	

	
	
		
		

		
		
	


	


_

 

cool Alex 
	

	
	
		
		

		
		
	


	




 I listened to both versions for half and hour each this weekend. The clipping was easily reproducible on the tube version. I wouldn't say I was listening at insane volumes. It seemed to also be frequency dependent to some extent, as the treble was the most obvious offender. If I had to guess a frequency, I'd say around 800Hz (starting at one octave above 440Hz, which is an easy reference for me) was the lowest I heard it and it extended up to the higher soprano ranges... As for the volume level, it was such that I could still hear people talking behind me with the SR-007 on. It was much more obvious on the SR-007 than the HE-60 or the Lambdas.

 If more impressions would help, I'm more than obliged to do what I can


----------



## Coreyk78

Sounds like a good move to me, I'm still in for a beta build 
	

	
	
		
		

		
		
	


	




 I had been trying to resist because this is going to cause me to drop even more money for a real pair of stax instead of my baby electrets, but I couldn't help myself


----------



## Emooze

Am I correct in saying that the new circuit doesn't require close matching?

 Edit: 'require' because I know it's preferred but the whole design is supposed to be cheap so buying 10+ BJT's to match seems to be against the principle


----------



## runeight

Unfortunately, the jfets will still need to be matched. It is a feature of this design.


----------



## HeadphoneAddict

That sounds cool - Bill was saying there were ways to boost the power via 400v PSU and/or some other tricks that he wasn't sharing with me yet. I will be loaning him my O2 Mk1 for a little while, so he can use them with his testing since I don't have an eXStata yet. I'll still have my HE60, Jade, SR-404LE, Smegma Pro and a couple others to keep me busy.


----------



## runeight

I know that you guys are always pushing the envelope 
	

	
	
		
		

		
		
	


	




 however, 400V rails are beyond the scope of this project and getting into really dangerous and unforgiving territory. Maybe later ...


----------



## Beefy

I have seen mention elsewhere that diodes to protect the FETs on power-down might be desirable in this amp. Any thoughts, runeight?


----------



## yossi126

I am looking for a builder, please pm me.


----------



## runeight

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I have seen mention elsewhere that diodes to protect the FETs on power-down might be desirable in this amp. Any thoughts, runeight?_

 

Ah, I see that conversation is going on elsewhere? Can you point me to this suggestion? It is not a bad one at all, although none of the current builds have shown this difficulty.


----------



## Beefy

Not so much a conversation, just a comment from a fairly well known electrostatic amp designer who is much smarter than I am


----------



## runeight

Gents, here's my list so far. Some of you didn't indicate which amp so I've put you down for both knowing that you would make a selection.

 Also, I think one other person signed up only through a post and I can't find it. 
	

	
	
		
		

		
		
	


	




 EDIT: Ah, I see that the table structure has completely failed. I'll fix this in a bit.


 emooze -- both
 awpagan -- hybrid 
 bada bing -- both
 macm75 -- hybrid
 audionut -- hybrid
 studeb -- both
 sergery -- hybrid
 webbie64 -- both
 n_maher -- both
 smeggy -- both

 As you can see we are not quite a liftoff. To make this economical for you all I'll need to buy at least 10 boards of each type of amp. And then 20 PS boards, one for each amp.

 Please let me know if I've missed you. Also, does headfi have UBB table tags? Most forums do, but I haven't tried them here.


----------



## scompton

I can be like smeggy and buy boards, but I'm not ready to build it yet. I need to do a couple of more builds first. If that's an option, you can put me down for both boards.


----------



## smeggy

yeah, mine will be tubey version thanks 
	

	
	
		
		

		
		
	


	




 Shiny!


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I know that you guys are always pushing the envelope 
	

	
	
		
		

		
			





 however, 400V rails are beyond the scope of this project and getting into really dangerous and unforgiving territory. Maybe later ..._

 


 I had mentioned using the old PS wth this design - unfortunately, the bias supplies would die. 'nuff said about that OLD design


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Unfortunately, the jfets will still need to be matched. It is a feature of this design. 
	

	
	
		
		

		
		
	


	


_

 

I happen to have a bunch of JFETS from the proto phase - i may able to match some sets for folk, depends on time constraints. Looks like I will be super busy until the end of the year...


----------



## awpagan

Alex

 in for a dime, in for a dollar
	

	
	
		
		

		
		
	


	




 Put me down for both.


----------



## bada bing

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Gents, here's my list so far. Some of you didn't indicate which amp so I've put you down for both knowing that you would make a selection.

 <snio>
 As you can see we are not quite a liftoff. To make this economical for you all I'll need to buy at least 10 boards of each type of amp. And then 20 PS boards, one for each amp.
_

 

If available, I'll take one board set of each type to help towards minimums. I won't be able to guarantee any timetable to complete the second amp for the beta build though. If holding a set of boards for a few weeks/months isn't proper for this stage of the project, I'll choose just the Hybrid version.


----------



## luvdunhill

Alex:

 I guess we haven't seen the full tube schematic, but I know there are a number of topologies (like 100% degeneration, and various hybrid topologies) that tubes can be used in that really lessen the "tube effect" on the sound. Such topologies make "tube rolling" a moot point and don't even really have any of the sonic characteristics that we associate with tube schematics of yesteryear. Is it possible that the tube and solid state version of your amp will sound more alike than different? Do you expect the distortion spectra to be different between the two, in the typical "solid-state" versus "tube" fashion?


----------



## runeight

Tube schematic is a few pages back. 
	

	
	
		
		

		
		
	


	




 But, I believe you are correct that the amps will sound more similar than different. And this IS because the tube in this case is used solely as a high voltage buffer same as the BJT in the sand version. This means that it won't color the sound as much as it might if it were, say, the primary gain stage.

 Nonetheless, it will have an efffect on the sound to some degree or another.

 In a differential amp, if it's working perfectly, the even harmonics are all canceled out while the odd are left in the signal. This would be true for any stat amp that I know about. Thus, if the tube "sound" is associated with even order harmonics a stat amp will mostly make those go away whether it's tubes or transistors. In a real differential amp, due to component mismatches the common mode rejection will not be perfect and so some even harmonics will leak through, but not anywhere near the odd harmonics if the amp is reasonably balanced.

 Then the question is the odd harmonics and in these two amps the theoretical odd harmonic spectrum is nearly the same. Real life, of course, is never the same as the theory.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Tube schematic is a few pages back. 
	

	
	
		
		

		
		
	


	




 But, I believe you are correct that the amps will sound more similar than different. And this IS because the tube in this case is used solely as a high voltage buffer same as the BJT in the sand version. This means that it won't color the sound as much as it might if it were, say, the primary gain stage.

 Nonetheless, it will have an efffect on the sound to some degree or another.

 In a differential amp, if it's working perfectly, the even harmonics are all canceled out while the odd are left in the signal. This would be true for any stat amp that I know about. Thus, if the tube "sound" is associated with even order harmonics a stat amp will mostly make those go away whether it's tubes or transistors. In a real differential amp, due to component mismatches the common mode rejection will not be perfect and so some even harmonics will leak through, but not anywhere near the odd harmonics if the amp is reasonably balanced.

 Then the question is the odd harmonics and in these two amps the theoretical odd harmonic spectrum is nearly the same. Real life, of course, is never the same as the theory. 
	

	
	
		
		

		
		
	


	


_

 

In this design, is there even some small advantage sonically with going for the tube hybrid? Like speed, warmth, euphonics, power, clipping, etc?


----------



## smeggy

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_In this design, is there even some small advantage sonically with going for the tube hybrid? Like speed, warmth, euphonics, power, clipping, etc?_

 

Pfft, who cares..... shiny tubes !!!


----------



## HeadphoneAddict

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Pfft, who cares..... shiny tubes !!! 
	

	
	
		
		

		
		
	


	


_

 

Heh, I already decided on tubes anyways. Need to find a way to build the amp with tubes sticking out the top! Well, maybe not, because it makes it harder to stack with an EHHA and CDP, etc...


----------



## Sherwood

I suspect it would be easier to match tubes as output devices, since tube testing is common. Am I off the mark here?


----------



## Emooze

Put it in a plexiglass case! 

 Smoked black so when it's off, might as well be opaque. I think I need to do this.

 Edit: transistors are pretty easy to match, usually just need some resistors and a DMM


----------



## Sherwood

It's not the difficulty of matching them, but of single-amp builders acquiring a matched set off the bat. How many BJTs would one need to buy to end up with enough matching? What would an individual building just one amp do with the extra?


----------



## HeadphoneAddict

Quote:


  Originally Posted by *Sherwood* /img/forum/go_quote.gif 
_It's not the difficulty of matching them, but of single-amp builders acquiring a matched set off the bat. How many BJTs would one need to buy to end up with enough matching? What would an individual building just one amp do with the extra?_

 

Bill said at least 25 to find a close match, but it would be nice to ear from the others too.


----------



## Beefy

From what I have read in this thread, it doesn't seem that the BJT's need to be matched. Only the input FETs, which are common across the two builds anyway.

 Further, each tube only replaces two transistors (a BC550C and a KSC5042), so even BJT matching wouldn't seem to be all that different between the two variants.


----------



## Sherwood

Alright, then, there we go. I'll still build the tube, because shiny.


----------



## Beefy

Bugger you all then...... if I can find some cheap Stax to buy, I'm going to build the sand version, just to be different!


----------



## luvdunhill

Thanks Alex, this is what I surmised and thanks for putting it more precisely.

 Given that the BJT and tubes are almost used interchangeably in the circuit as a buffer and the fact we are driving a capacitive load, would the difference in Cob between the BJT and 6S4A, would this parameter make one better than another at driving more complex loads?


----------



## Sherwood

You will only harm yourself, Beefy, you shall not harm us 
	

	
	
		
		

		
		
	


	




 FWIW, I've had a loaner of the sand version (before the recent output changes) up for over a week now runnning day and night, and it really sounds stupendous. I'm a big fan of this whole effort.

 My way of being different is building a tube version that only has a normal output. It makes it harder to sell, which is good for me.


----------



## luvdunhill

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_From what I have read in this thread, it doesn't seem that the BJT's need to be matched. Only the input FETs, which are common across the two builds anyway.

 Further, each tube only replaces two transistors (a BC550C and a KSC5042), so even BJT matching wouldn't seem to be all that different between the two variants._

 

despite the above, matching a device with hfe of 30 is a piece of cake. I bet if you pull 10 out of a bag, 8 will have the same hfe +/- 1.


----------



## luvdunhill

Quote:


  Originally Posted by *Sherwood* /img/forum/go_quote.gif 
_I suspect it would be easier to match tubes as output devices, since tube testing is common. Am I off the mark here?_

 

yeah, yeah, multi-quote fail....

 anyways, don't forget the tube testing would need to be done at the exact parameters as the circuit... most tube testers don't have an eXStata setting 
	

	
	
		
		

		
		
	


	




 Now, converting a eXStata board into a tube tester would be handy, if you were kitting up a bunch of these


----------



## Emooze

Personally, I'm partial to SS designs myself. Semiconducter physics never ceases to amaze me.


----------



## Beefy

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Given that the BJT and tubes are almost used interchangeably in the circuit as a buffer and the fact we are driving a capacitive load, would the difference in Cob between the topologies make one better at driving more complex loads?_

 

..... don't take this the wrong way, but I get the slight impression that you want to share your thoughts/analysis on the design, but are holding back?

  Quote:


  Originally Posted by *Sherwood* /img/forum/go_quote.gif 
_You will only harm yourself, Beefy, you shall not harm us 
	

	
	
		
		

		
		
	


	


_

 

HEH! In my circumstances, the target case probably isn't quite tall enough for the tubes, and I don't want to have tubes poking out because I want it to stack.


----------



## Sherwood

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_ HEH! In my circumstances, the target case probably isn't quite tall enough for the tubes, and I don't want to have tubes poking out because I want it to stack._

 

Well, seeing as how tuberolling is pretty much pointless, you could eschew socketing them straight up and down entirely and just solder them, like in a capitole.

 Of course, you could also forget that and build a sand amp...


----------



## runeight

This is a very interesting discussion. 
	

	
	
		
		

		
		
	


	




 The only transistors that must be matched are the jfets. The rest don't really matter too much, although matching the small signal mirror devices would make the amp a bit more precise.

 Driving loads is really pretty much in the hands of the follower transistors and is not affected by the high voltage device, whether it's the tube or the KSC. And so, as best I can see, both amps have the same ability to drive capacitances. With the followers running at a little over 3mA the 400uA or so that a 150pf load will demand does not eat into the follower current enough to disturb them in the new version of the amp. In the old version, with the resistors, this was a significant factor. I just thought that an entry-level amp like this would not need to have the higher voltage swings and that simpler was better. Just goes to show you what I know. 
	

	
	
		
		

		
		
	


	




 It is not necessary to match tubes so long as they are not terribly far apart in operating points. My guess is that normal, good condition, out-of-the-box pairs will be ok. The current balances in the amp are established by the jfets and the current mirrors so that the HV device doesn't really have much say over this.


----------



## Emooze

Matching 2 FETs for the diff pair is much better than getting the 4 or so additional needed for the previous design. 

 I approve of the change is the main point you should take away from my drivel


----------



## runeight

Ah well ... even in this version it is best to match the quad as it keep the two channels in better balance. I had about 15 jfets on hand and I have pulled two quads from them. I know that mileage will vary depending on the mix of parts and the manuf lots that they came from etc., but I hope that this will not be a serious impediment.


----------



## sergery

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Given that the BJT and tubes are almost used interchangeably in the circuit as a buffer and the fact we are driving a capacitive load, would the difference in Cob between the BJT and 6S4A, would this parameter make one better than another at driving more complex loads?_

 

What is Cob?


  Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_Personally, I'm partial to SS designs myself. *Semiconducter physics never ceases to amaze me.*_

 

amen
	

	
	
		
		

		
		
	


	










 Maybe I will build the sand version down the road,


----------



## Beefy

I _think_ Cob refers to parasitic capacitance of the device.


----------



## luvdunhill

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I think Cob refers to parasitic capacitance of the device._

 

yup output capacitance.. what can make or break a device for 'stat amp.


----------



## wiatrob

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Heh, I already decided on tubes anyways...._

 

The Tube amp performs a little better... can I hear it? Dunno, somebody won't return my sand amp!


----------



## HeadphoneAddict

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_The Tube amp performs a little better... can I hear it? Dunno, somebody won't return my sand amp! 
	

	
	
		
		

		
			



_

 

Should have made Tyler bring it with him to lunch the other day. How's the O2 Mk1 doing?


----------



## luvdunhill

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_The Tube amp performs a little better... can I hear it? Dunno, somebody won't return my sand amp! 
	

	
	
		
		

		
		
	


	


_

 

I hate when that happens 
	

	
	
		
		

		
		
	


	




 How does it perform better?


----------



## runeight

Gents, here's what I have for the current tally. I have made some assumptions from a few of your responses. Please correct if I'm wrong.

 emooze --> SS
 awpagan --> both
 bada bing --> both
 macm75 --> hybrid
 audionut --> hybrid
 studeb --> both
 sergery --> hybrid
 webbie64 --> both
 n_maher --> both
 scompton --> both
 smeggy --> hybrid
 headphoneadict --> hybrid
 sherwood --> hybrid
 beefy -->SS
 runeight --> both

 This makes 9 sand boards and 13 hybrid boards. Studeb and webbie64 I don't think I have a selection from either of you. If you could kindly let us know.

 We are now good on the hybrids and, depending on the last few choices, maybe there on the sand amps.

 Perhaps another day or two to be sure everyone is certain ...


----------



## ericj

My two bits: I think the sand amp is a little more aggressive and to my ears sounds a bit faster. The hybrid is a touch more fluid. 

 But they're both excellent amps and if i had to sell one of them I'd have a heck of a time deciding.


----------



## wiatrob

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Should have made Tyler bring it with him to lunch the other day. How's the O2 Mk1 doing?_

 


 I thought he _was _bringing it to lunch! The O2's are doing excellent. I have a bit of a hotrodded amp, and it's kicking butt. 
	

	
	
		
		

		
		
	


	




 I'm not good with impressions, and I have some other commitments this weekend, but I'll post some early next week.


----------



## wiatrob

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_I hate when that happens 
	

	
	
		
		

		
		
	


	




 How does it perform better?_

 

It's faster. runeight can provide specifics...


----------



## runeight

Theoretically the tube amp is faster for small signals. How this goes on real amps on real boards with stray capacitance everywhere is a different story.


----------



## Sherwood

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Should have made Tyler bring it with him to lunch the other day._

 

 Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I thought he was bringing it to lunch!_

 

He thought he was too 
	

	
	
		
		

		
		
	


	




 It was snowy, and his wife stole the car with the toys.

 Upside is I still have it, though, and while that hurts all of you, it helps me immensely, so I have little motivation.


----------



## wiatrob

Quote:


  Originally Posted by *Sherwood* /img/forum/go_quote.gif 
_He thought he was too 
	

	
	
		
		

		
		
	


	




 It was snowy, and his wife stole the car with the toys.

 Upside is I still have it, though, and while that hurts all of you, it helps me immensely, so I have little motivation._

 

Oh, yeah - there was a _reason _you didn't have it. i will have the hybrid cased up next weekend. Then we can get together and listen to both...


----------



## Sherwood

Ooh, Bill, it's a date


----------



## smeggy

Geez, get a room already...


----------



## HeadphoneAddict

Quote:


  Originally Posted by *Sherwood* /img/forum/go_quote.gif 
_Ooh, Bill, it's a date_

 

 Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Oh, yeah - there was a reason you didn't have it. i will have the hybrid cased up next weekend. Then we can get together and listen to both..._

 

Just to creep out Smeggy we'll have to make it a threesome.


----------



## Sherwood

Creep him out? Good luck. Smeggy's on Expedia right now.


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Theoretically the tube amp is faster for small signals. How this goes on real amps on real boards with stray capacitance everywhere is a different story._

 

ain't that the truth. Maybe someone will post some measurements and we can see for real


----------



## wiatrob

If I had a signal generator. Maybe Santa will bring me one!


----------



## wiatrob

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Just to creep out Smeggy we'll have to make it a threesome._

 


 You're _creeping _me out. But I love you guys anyway. I'll get the Hybrid cased up next week so Larry will actually listen to it.

 Also - there was a call for loaners for meets - I have *Keithpgdrb's anyone else??*


----------



## runeight

Gents, since we are close to 10 each of everything (20 on the PS) I've sent gerbers to the fab for a quote. I should have the answer by today or Monday. When I do I can let you know the price of a board set (1 amp and 1 PS). I'm pretty sure that the two amp boards will cost about the same.

 Those of you who are wanting two amp boards, I have been assuming that you want two PS boards, one for each amp. If you plan to build both amps you'll need one PS board for each amp because the PS is designed to only power a single board. Let me know if this changes your numbers. It's something that we forgot to talk about.


----------



## luvdunhill

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_If I had a signal generator. Maybe Santa will bring me one!_

 

yeah, that would be cool 
	

	
	
		
		

		
			





 Make sure you check out the quoted rise time for square wave and that it's well under whatever you plan on measuring. I haven't seen any quoted numbers in this thread (other than "faster"), so you may be trying to hit a moving target. Something like a Wavetek 188 should be appropriate though.

 Other things to consider is the max voltage your scope can handle, as well as the fact that you really need to make a differential measurement, and this can be tricky to do without a reference, though there are probes than can help in this regard.

 Perhaps Alex can make some suggestions on the proper way to measure a stat amp?


----------



## Beefy

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_My two bits: I think the sand amp is a little more aggressive and to my ears sounds a bit faster._

 

 Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Theoretically the tube amp is faster for small signals._

 

Ooooops!


----------



## luvdunhill

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Ooooops! 
	

	
	
		
		

		
		
	


	


_

 

"Faster" means one thing to a designer and a different thing to a audiophile


----------



## runeight

A small change to the list.

 emooze --> SS
 awpagan --> both
 bada bing --> both
 macm75 --> hybrid
 audionut --> hybrid
 studeb --> sand
 sergery --> hybrid
 webbie64 --> hybrid
 n_maher --> both
 scompton --> both
 smeggy --> hybrid
 headphoneadict --> hybrid
 sherwood --> hybrid
 beefy -->SS
 runeight --> both


----------



## runeight

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_"Faster" means one thing to a designer and a different thing to a audiophile 
	

	
	
		
		

		
		
	


	


_

 

Right.


----------



## Beefy

Whoa, I didn't realise my name had snuck onto the list...... I'm planning a build in about 4-6 months time - not for this prototype stage. I have WAY too much on my plate right now, and I don't even have any electrostatic phones yet.

 Sorry for any confusion


----------



## HeadphoneAddict

Will we paypal you the money for the boards? Can I have it shipped to a different address than my paypal address (to Bill)?


----------



## Coreyk78

Hi runeight, I sent you a couple of pms, maybe you missed them. I want to be put on "the list" for a solid state build.


----------



## runeight

Beefy, sorry about that. I tried to guess from your posts and figured you would let me know.

 Coreyk78, you're on the list.

 Headphoneaddict, no problems on address.

 While we're waiting for quotes, here's a 3D of the sand board:


----------



## luvdunhill

looks nice!

 One thing I'd consider, based entirely on personal experience, is... Running top-side traces and ground planes under heat sinks. I've had problems where solder resist was assumed to be an excellent insulator and it failed those hopes and dreams 
	

	
	
		
		

		
		
	


	




 Also, do you think you will have adequate clearance to screw the devices on the lower two heat sinks, given that the TO-92 devices are right behind them? I'm not a TO-92 squasher, like many I see around here, so that might not effect everyone...


----------



## runeight

Thanks for the experience on the traces. I'm pretty sure that none are under the heatsinks except where there are gaps where the devices go. But, I may be wrong and I will double check against the heatsink drawings.

 Good catch on the TO92s. I'll look at that too as it might be a problem for some builders.

 Aha, I see what you mean ... wait.


----------



## runeight

So, placing a real heatsink on a printout of the board I am slightly under at one corner. Good eye Marc. I'll fix this.

 There is a long ground trace that goes under the heatsinks at the outsides of the board. My reasoning here is thus: The transistors are plastic packages and the heatsinks are not attached to pads. So there shouldn't be any HV possible on the heatsink and so the ground trace underneath is ok providing that none of the topside HV traces are also underneath the aluminum. So fixing the first problem should permit this under-heatsink ground trace.


----------



## runeight

OK. I've modified the traces that were nicking the heatsinks (both boards). I think everything else is ok. See above.

 I checked the TO92 devices and for me there would be plenty of clearance with fairly long leads on the them. I think we're ok here.

 Although I've already sent gerbers to be quoted, when I do the boards I'll send them a new set with these new changes.

 Thanks again Marc.


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_My reasoning here is thus_

 

That makes sense. I would be worried if the device was torqued down on the isolation pad enough to short to the heat sink. If this happened, and the heat sink was to scratch through the solder resist, bad things could happen. Another thing to verify is the voltage rating for the pads used by the output devices. You may consider using aluminum oxide pads, as they are much more rugged... then again, perhaps these are isolated packages? anyways, you get the idea 
	

	
	
		
		

		
			





 Would there be a potential issue with those TO-92 packages being so close to the heat sinks, for either thermal runaway or drift of sorts?


----------



## runeight

Yes, the KSC5042s are all plastic so no risk of their shorting to the heatsink.

 I'm pretty sure that the TO92 are ok where they are. They will get warmed up but most of the convection heat should be above them and the radiative heat from the sinks is, IIRC, very small.


----------



## Emooze

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes, the KSC5042s are all plastic so no risk of their shorting to the heatsink._

 

The KSC5042F is insulated, the regular KSC5042 doesn't seem to be. I did a quick search and Mouser actually shows the non-insulated one as obsolete.


----------



## runeight

Yes, all the KSCs on the protos were the F model. 

 Someone asked about matching the jfets. Here's a diagram. This will be on the website.






 Match the currents to within 10% and you're good. I think 20 devices should give at least one quad. I got two quads from a random selction of 15 jfets. You want the Idss to be over 10mA. There will be some devices less than this. Don't use them.

 There is a good section at AMB Laboratories DIY Audio Site on matching devices. I don't remember where but it might be under the b22.


----------



## runeight

Sorry gents, no quote came yesterday. But they never take more than 24 business hours so I'll have it by Monday and I'll be able to give the board costs.

 So, while we wait, here's the PS board. We haven't talked much about the PS but it is a nice, compact, +/- 300V supply.


----------



## audionut

Looks good! Has the schematic (PS) been posted on another page in this thread, or is it still coming as we get closer to the beta build? Also, thanks for posting the procedure for matching the jfets. That's exactly what I was looking for!


----------



## nattonrice

Is that just how it renders or are you planing on getting a black solder mask?
 Very sexy either way =]


----------



## runeight

Schematic for the PS has not been posted but it will be on the website.

 nattonrice, the mask will be black with white silk. And since the Wima caps are red the PS board will look more or less like it does in the 3D rendering.


----------



## runeight

While we are twiddling our thumbs, tube 3D


----------



## manaox2

Wow, this is going to save a lot of questions come time for trouble shooting. Thanks!


----------



## Lou Erickson

It's looking like a clean and manageable board to build, too. I'm really impressed by the work that's been put in to this!


----------



## runeight

Gents it looks like we have enough for the beta order. I've attached a pdf for you to look at. Please be sure you mean to be on the list again and make sure I've got you marked for the right build.

 Depending on how many boards I order it looks like about $25 per set (hopefully less - I've made a few small mods and need to re-quote). A set is one PS and one Amp board. I ask that if you order more than one amp you get a PS for each. You'll need to have one for each if you plan to build both and this will prevent me from having a pile of PS boards on my workbench. 
	

	
	
		
		

		
		
	


	




 I'm not going to order extras for this run.

 I'll have to add your shipping and packaging to this cost and I will ship overseas if you give me the method.

 A few of you have asked about kits. Initially wiatrob was going to supply kits for the beta build and I had requested that you all use these kits to help me in supporting the amp builds. However, wiatrob is suddenly underwater at work (it happens 
	

	
	
		
		

		
		
	


	




 ) and so won't be able to provide this service. I'm not able to do it myself at the moment, but I will provide the BoMs on the website as soon as I make the board order. 

 If there is anyone of of you who would consider handling the small number of kits for this build I'd be delighted to hear from you. 
	

	
	
		
		

		
		
	


	




 If I don't hear anything further today and tonight I will place the board order tomorrow. Fab time will be about 8 business days plus travel time to you. Fortunately, this will give me time to complete out the website and get the BoMs in order. Once I get boards I will build one PS and probably one Sand board to verify that the build comes up. Then it's boards off to you.


----------



## audionut

Alex, Couple questions. Once you get boards in, how will we pay you for them? Do you do paypal, etc.. or how will this work? Also, when I go to your website, my 4:3 monitor hear at work won't display all of the tabs (Active Designs, Previous Designs etc.). Our 16:9 screen on our laptop at home displays fine. I'm assuming your site is displayed for theate wide screens only?? Anything to set different so site will display properly on older computer monitors? Also, is the Hammond 270AX the xfmr that's being recommended for the PS? I have a Hammond 270EX that has a higher secondary 0-275-0 vs 0-240-0 that the AX has. I don't have a problem using the AX, except there's only a couple out there available, and may be in short supply once everyone's ready to build (2 week lead time). Does the 270EX look like it'll work?


----------



## runeight

Gents I meant to also say that I have not always replied directly to your PMs but have tried to include your request in the list.

 We have one change in the last hour or so. Attached.


----------



## runeight

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Alex, Couple questions. Once you get boards in, how will we pay you for them? Do you do paypal, etc.. or how will this work? Also, when I go to your website, my 4:3 monitor hear at work won't display all of the tabs (Active Designs, Previous Designs etc.). Our 16:9 screen on our laptop at home displays fine. I'm assuming your site is displayed for theate wide screens only?? Anything to set different so site will display properly on older computer monitors? Also, is the Hammond 270AX the xfmr that's being recommended for the PS? I have a Hammond 270EX that has a higher secondary 0-275-0 vs 0-240-0 that the AX has. I don't have a problem using the AX, except there's only a couple out there available, and may be in short supply once everyone's ready to build (2 week lead time). Does the 270EX look like it'll work?_

 

Cross posts. 
	

	
	
		
		

		
		
	


	




 I see what you mean about the screen res. This has never come up before. Amazing that it hasn't. I'll see what I can do about it.

 The 270EX secondary voltage is too high. But the 269JX is also a good fit and, with the latest changes, might actually be a better choice. Are there any of these around??


----------



## runeight

No, wait, I was testing at 800x600. However, it was designed for a minimum res of 1024x768. Do you not have this size screen?


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Cross posts. 
	

	
	
		
		

		
			





 I see what you mean about the screen res. This has never come up before. Amazing that it hasn't. I'll see what I can do about it.

 The 270EX secondary voltage is too high. But the 269JX is also a good fit and, with the latest changes, might actually be a better choice. Are there any of these around??_

 

The 269JX is on order(Mouser), they have one CAX, but it's $20 more. Will keep searching.


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Are there any of these around??_

 

well, stopped looking after I found one, but ...

Hammond Power Transformer 269JX

 what current draw are you looking for? There are some fantastic deals with some of the "Allied" transformers, which are most likely Hammonds anyways. For example:

http://www.alliedelec.com/search/pro...px?SKU=2270113


----------



## Emooze

Looks good, sounds good, can't wait!


----------



## runeight

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_well, stopped looking after I found one, but ...

Hammond Power Transformer 269JX

 what current draw are you looking for? There are some fantastic deals with some of the "Allied" transformers, which are most likely Hammonds anyways. For example:

Allied - 6K88VG - Allied Electronics_

 

In the new design the negative rail will pull about 40mA. With a bridge rectifier this translates to about 64mA at the secondary. The 270AX is only 50mA but might skate by. The 269JX is 69mA and should be more than adequate. For the sand version there is a pair of triads that will work.


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_No, wait, I was testing at 800x600. However, it was designed for a minimum res of 1024x768. Do you not have this size screen?_

 


 My bad. Changed my resolution to 1024x768. Problem solved. Back to the xfmr question. Do you think the 270AX will still work with the changes made to amp? Mouser has 2, and I'd like to go ahead and get one on order before they're gone. Sorry, cross post again.


----------



## Sathimas

I am following this thread with lots of interest, I'm planning to rise to the electrostatic league next year.
 I don't know if there are any other affordable stat-amps out there, but this one definitely meets my budget.

 Great work!

 Now my question - just for interest:
 How high is the power consumption (and dissipation) of this amp?

 The only other DIY-Amp I know yet is the blue hawaii which consumes ~ 200Watts.
 Hope the eXStata won't be that hungry!


----------



## runeight

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_My bad. Changed my resolution to 1024x768. Problem solved. Back to the xfmr question. Do you think the 270AX will still work with the changes made to amp? Mouser has 2, and I'd like to go ahead and get one on order before they're gone. Sorry, cross post again._

 

I don't know yet on the 270 until I try it, but my guess right now is no (edit).

 Sathimas the sand version about 30W. Add 15W for the heaters on the tube version.


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_In the new design the negative rail will pull about 40mA. With a bridge rectifier this translates to about 64mA at the secondary. The 270AX is only 50mA but might skate by. The 269JX is 69mA and should be more than adequate. For the sand version there is a pair of triads that will work._

 

270AX actually listed at 58mA, which is still probably borderline. May go ahead and order JX from Angela, as luvdunhill suggested.


----------



## audionut

What about the 270DAX that I have in my Bijou? It has a 520V C.T. I could use it until I can get a xfmr for the extata.


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_The 270EX secondary voltage is too high. But the 269JX is also a good fit and, with the latest changes, might actually be a better choice. Are there any of these around??_

 

When I was looking, I decided I would probably splash out the extra cash for the 369JX. Pricey, but a much better option that not being able to use my amp back in Australia at 230V mains 
	

	
	
		
		

		
		
	


	




 Perhaps the transformer would be a prime target for a group buy? Nobody ever seems to have more than a couple in stock, and at Mouser the price breaks come up at just 5 or 10 units.

 [EDIT] Hmmm, Newark actually has stock of both the 269JX and 369JX at OK prices.


----------



## studeb

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_A few of you have asked about kits. Initially wiatrob ..., but I will provide the BoMs on the website as soon as I make the board order. 

 If there is anyone of of you who would consider handling the small number of kits for this build I'd be delighted to hear from you. 
	

	
	
		
		

		
		
	


	


_

 

i can help out with some of this. Maybe the sand versions? Anyone else care to join in?


----------



## HeadphoneAddict

That website for the 269JX lists the transformer at 60ma. Is that a typo or just not the particular ma spec that we're talking about here?


----------



## smeggy

Is that allied transfo suitable for the amp because it is a great price.


----------



## bada bing

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_What about the 270DAX that I have in my Bijou? It has a 520V C.T. I could use it until I can get a xfmr for the extata._

 

X2

 I have a 270DAX left over after an upgrade to a Bijou. The output numbers are better all around except the voltage is a little higher. Is the 270/370DAX suitable for the eXStata?


----------



## ericj

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Is that allied transfo suitable for the amp because it is a great price._

 

No. The HV secondary is only rated at 40ma, vs the 69ma rating of the 269jx. It's less well suited than the 270ax, which is itself not quite enough. 

 It was probably made by hammond ('made in canada' is a bit of a giveaway) but it's simply not big enough.


----------



## smeggy

Mmmkay, thanks.


----------



## Coreyk78

Hmm, If a 500vct transformer will work, then this could be a good candidate also.

EDCOR - XPWR001

 or this one

http://www.edcorusa.com/Products/Sho...ct.aspx?ID=648


----------



## spritzer

R80-36 should do the trick.


----------



## smeggy

shipping knocks the price up a lot on that, need to find local stuff


----------



## Coreyk78

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_shipping knocks the price up a lot on that, need to find local stuff_

 

The Edcors are built in New Mexico


----------



## spritzer

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_shipping knocks the price up a lot on that, need to find local stuff_

 

Indeed but those have dual 115v primaries. 
	

	
	
		
		

		
		
	


	




 Edit: and solve one of the most annoying issues with the Hammond EI cores, height.


----------



## audionut

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_That website for the 269JX lists the transformer at 60ma. Is that a typo or just not the particular ma spec that we're talking about here?_

 

The 60 you may be referring to is in the 60hz frequency column. The secondary mA rating is 69mA according to the chart I'm looking at.


----------



## runeight

Gents, I can only ask that you don't stray far from the spec. Originally the spec was:

 240-0-240/>50mA.

 Now, due to changes it is:

 250-0-250/>65mA.

 Depending on the regulation of the transformer, transformers with current ratings that are too high may also not work as their secondary voltages under load will be too high too.

 Heater requirments are 6.3V/2.5A.

 I know that transformers are often very difficult to source around the world, but if we can stay close to the specs it will help ensure that everyone gets up first time/every time.


----------



## runeight

One more beta builder. I see that tubes are more popular than sand. 
	

	
	
		
		

		
		
	


	




 It's ok though. I think we have enough sand builds to make the board buy.


----------



## runeight

Not having heard from anyone to the contrary I will pull the trigger on boards tomorrow morning. Figure around $22.50 per set of one PS and one Amp board.

 Gentlement I have checked these boards every which way and then some. They seem to be solid. Enough trace and pad spacings for the 600V maximim voltage differential that can be seen in various places. Good, but tight part spacings. Good ventilation. Heater traces on the tube boards well away from the signal paths.

 Nothing left to do but go ...


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Not having heard from anyone to the contrary I will pull the trigger on boards tomorrow morning. Figure around $22.50 per set of one PS and one Amp board.

 Gentlement I have checked these boards every which way and then some. They seem to be solid. Enough trace and pad spacings for the 600V maximim voltage differential that can be seen in various places. Good, but tight part spacings. Good ventilation. Heater traces on the tube boards well away from the signal paths.

 Nothing left to do but go ..._

 

Great! Any idea appox how long before the final parts list and values will be posted on your website? Would like to go ahead and start rounding up parts while we're waiting on the boards.


----------



## dBel84

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Cross posts. 
	

	
	
		
		

		
		
	


	




 I see what you mean about the screen res. This has never come up before. Amazing that it hasn't. I'll see what I can do about it._

 

Heh - my notebook has been a pia but i just hide the lower info bar or google directly to the page i want 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## runeight

Funny you should ask that as I've spent the last two hours working on the BoMs. I'm attaching all three of them, but they won't make any sense to you until I get the website going in the next day or two.

 Nonetheless, you can start checking on parts availability.

 And if there is anyone who would be kind enough to create the mouser BoM sheet in each of the spreadsheets I would really appreciate this.

 Now I know that many of you will want to sub like crazy on these lists and start asking can I use this or that instead of this.

 I am asking that you please don't do this or do it as little as possible. If there are too many subs I just simply won't be able to keep up with you and help you if there are problems. Except for one or two instances these parts have been vetted in the proto builds. The only real trouble is the 500V fets, but there are suitable subs in the BoM. Let me know if there is anything else that has gone out of stock at Mouser.


----------



## sergery

what would be an appropriate value for a pot?? I am eying one of the balanced attenuators from either these guys or their competitors these guys. 

 Thanks

*edit:* doh, cross post!!!


----------



## runeight

Now, some of you may be wondering why I'm being so particular about the parts.

 One reason is this. Many diyers don't realize that resistors have voltage ratings too. For example the vishay rn55d resistors are rated at 250V. If they are stressed beyond this they will eventually fail.

 There are many places in this amp where the resistors will see close to 550V on peak swings and some places where they will see a constant 300V.

 To handle this I've done two things. First, I've selected higher voltage resistors where needed. Second I've put resistors in series to achieve the higher voltage rating that is necessary.

 The part numbers in the BoM reflect these voltage requirments and if you swap resistors in without considering this requirement you may have failures that will be hard to identify.

 The other reason is that I've tried to stick to 1% resistors wherever possible. Although one can argue that this is not really necessary, I think it just eliminates one source of imbalance in the amps. It is easy to do and not expensive.

 Etc....


----------



## runeight

Quote:


  Originally Posted by *sergery* /img/forum/go_quote.gif 
_what would be an appropriate value for a pot?? I am eying one of the balanced attenuators from either these guys or their competitors these guys. 

 Thanks

*edit:* doh, cross post!!!_

 

There are probably quite a few choices on good pots, from two dual pots to a single four gang stepped attenuator. This I am happy to leave in your hands as it won't affect the builds.


----------



## runeight

Gents, I've reposted the BoM zip because I forgot that the PS now has an optional power led. You'll see these parts at the bottom of the PS BoM.

 If you've already grabbed the BoM zip, please grab it again.


----------



## runeight

And, one more adjustment to the tube BoM because I forgot the heater biasing resistors. Hopefully I'm done for the night.

 Tomorrow I'll tackle the website.


----------



## sergery

I took a quick peek at the tube BOM and accompanying PS BOM. on the PS BOM three notes: 
 1: 512-1N4757A 51V zener diode is out of stock, consider this as a potential relacement: BZX85C51 (check to make sure we have the right specs, I am not sure if it meets our reqs.)
 2. 651-1729173 should read qty. 1 - this is the 7-position Phoenix terminal.
 3. 546-269JX - Hammond 269JX transformer is out of stock @ Mouser.

 I corrected the PS BOM if that is easier.

 Cheers
	

	
	
		
		

		
		
	


	



 serge


----------



## sergery

A Tube + PS BOM from Mouser, quickie link
 Exact amounts of all parts, missing the 51V diodes as described above, no Transformer.

*edit:* dbl checked, a few parts were not adding correctly, they are added now. led's changed.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *sergery* /img/forum/go_quote.gif 
_A Tube + PS BOM from Mouser, quickie link
 Exact amounts of all parts, missing the 51V diodes as described above, no Transformer._

 

Wow, Thanks!


----------



## sergery

Just noticed while looking over, 71-CPF268K100FKB14 68.1K 2W resistors are backordered. It doesn't look like Mouser carries a suitable alternative. This affects tube and sand main boards.


----------



## runeight

Sergery, really appreciate your vetting the BoMs. I'll fix the 68k somehow.


----------



## runeight

OK. New BoMs with alternates for the missing parts.

 The 68k is 2%. Close enough.


----------



## pabbi1

Angela Instruments Online Catalog - Home is an excellent source for Hammond iron of all sorts, and better priced even including shipping, FWIW.

 I also have a 50+ stockpile of 6s4a tubes available to proto builders for $3 each (tested, plus ship) IFF anyone is interested. Tubedepot is also a good source, but these are plentiful on the ground.


----------



## audionut

Alex, I have the Hammond 270CAX on hold and think I am going to go ahead and get it, as it's in stock. The only difference is the CAX has a higher mA rating of 81 vs the 69mA for the JX. Before I order, just wanted to run this by you to see if you see any problem with the CAX? Thanks.


----------



## runeight

This should be ok.


----------



## audionut

Quote:


  Originally Posted by *sergery* /img/forum/go_quote.gif 
_I took a quick peek at the tube BOM and accompanying PS BOM. on the PS BOM three notes: 
 1: 512-1N4757A 51V zener diode is out of stock, consider this as a potential relacement: BZX85C51 (check to make sure we have the right specs, I am not sure if it meets our reqs.)
 2. 651-1729173 should read qty. 1 - this is the 7-position Phoenix terminal.
 3. 546-269JX - Hammond 269JX transformer is out of stock @ Mouser.

 I corrected the PS BOM if that is easier.

 Cheers
	

	
	
		
		

		
		
	


	



 serge_

 


 There's also a Vishay replacement from Mouser for the 512-1n4757a 51v zener that's out of stock. The Mouser # is 78-1N4757A


----------



## MrMajestic2

Looking at options that are available over here would the 369JX or the 370CAX be ok? Looks like the US versions but with universal primaries.


----------



## les_garten

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Angela Instruments Online Catalog - Home is an excellent source for Hammond iron of all sorts, and better priced even including shipping, FWIW.

 I also have a 50+ stockpile of 6s4a tubes available to proto builders for $3 each (tested, plus ship) IFF anyone is interested. Tubedepot is also a good source, but these are plentiful on the ground._

 

Nice Link! Thanx! Lots of Nice PIX for new builders like myself!


----------



## studeb

Quote:


  Originally Posted by *sergery* /img/forum/go_quote.gif 
_A Tube + PS BOM from Mouser, quickie link
 Exact amounts of all parts, missing the 51V diodes as described above, no Transformer.

*edit:* dbl checked, a few parts were not adding correctly, they are added now. led's changed._

 

This lists 221k resistors, and 47.5 ohm resistors. Where are those on the BOM?


----------



## audionut

Alex, What exactly are the female XLR panel mounts listed in the amp section used for? Sorry, but just a little confused as to what or where they would be used. Thanks


----------



## Emooze

What's the recommended voltage spec on the wire?


----------



## spritzer

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Alex, What exactly are the female XLR panel mounts listed in the amp section used for? Sorry, but just a little confused as to what or where they would be used. Thanks_

 

Balanced audio input for the amp presumably

  Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_What's the recommended voltage spec on the wire?_

 

I'd stick with 600v wire just to be on the safe side.


----------



## audionut

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_Balanced audio input for the amp presumably



 I'd stick with 600v wire just to be on the safe side._

 


 Spritzer, Thanks, that's what I was thinking they were for. Since my source isn't balanced, won't need them. Can anyone supply a good part # for some decent L/R phono input jacks? Thanks.


----------



## Emooze

The really nice Neutrik RCA's are Mouser numbers 568-NF2D-B-2 and 568-NF2D-B-9 for red and white respectably


----------



## n_maher

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Looking at options that are available over here would the 369JX or the 370CAX be ok? Looks like the US versions but with universal primaries._

 

Regardless of where you live it'd be my recommendation to use the Hammond 300 series transformers. That's what I plan to do for my build. While spec'd the same as their 200 series counterpart the 300 series trafos are much better built in my experience and have far fewer instances of mechanical noise.


----------



## audionut

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_The really nice Neutrik RCA's are Mouser numbers 568-NF2D-B-2 and 568-NF2D-B-9 for red and white respectably_

 


 Thanks, Emooze, Just what I was looking for.


----------



## spritzer

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Spritzer, Thanks, that's what I was thinking they were for. Since my source isn't balanced, won't need them. Can anyone supply a good part # for some decent L/R phono input jacks? Thanks._

 

Just remeber to ground the - input of the amp when using it with an RCA input. A simple wire from the input ground next to it is all you need but I usually setup an input switch that switches between the two and also grounds the - when set to RCA.


----------



## ericj

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_What's the recommended voltage spec on the wire?_

 

Military surplus PTFE insulated wire works well and isn't hard to find or expensive on ebay (navships, etc). 

 (Most of this wire is silver plated copper, but the silver is there to protect the hot-extruded teflon from the copper or tin. The military specification for this wire is about the dielectric strength and resistance to water, heat, and abrasion of the insulator. You can't hot extrude PTFE directly on top of copper or tin (the hot PTFE reacts with the metal and creates a gas that puts tiny bubbles in the insulator). There are some new less-hot extrusion methods, so tin plated copper with PTFE insulation is becoming more common.)

 (Oh, and Teflon(r) is a whole line of products that includes lots of fluoropolymers, most of which aren't as good as PTFE.)


----------



## audionut

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_Just remeber to ground the - input of the amp when using it with an RCA input. A simple wire from the input ground next to it is all you need but I usually setup an input switch that switches between the two and also grounds the - when set to RCA._

 

Yes, thanks again. That's what I did on my KGSS, grounded the negative terminal of the RCA input.


----------



## ericj

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Yes, thanks again. That's what I did on my KGSS, grounded the negative terminal of the RCA input._

 

You mean you grounded the negative input on the amp board, right?


----------



## Beefy

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_Military surplus PTFE insulated wire works well and isn't hard to find or expensive on ebay (navships, etc)._

 

I was checking this today. The 'standard' 22AWG 19 strand Thermax wire that John sells with the 0.05" outer diameter seems to only be rated to 150V......

Item # 22-TE-1934-UL/CSA, UL 1212, 1213; CSA 150V Wire- Extruded PTFE Insulation (Low voltage) on Thermax

 [EDIT] Wait, there are other similarly sized products that are rated to 300V


----------



## Emooze

100ft of 600v wire is around $18 from digikey (compared to $30 at Mouser) but I'm gonna keep looking around


----------



## ericj

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I was checking this today. The 'standard' 22AWG 19 strand Thermax wire that John sells with the 0.05" outer diameter seems to only be rated to 150V......

Item # 22-TE-1934-UL/CSA, UL 1212, 1213; CSA 150V Wire- Extruded PTFE Insulation (Low voltage) on Thermax

 [EDIT] Wait, there are other similarly sized products that are rated to 300V_

 


 Most of the ebay PTFE wire doesn't have a known specification or manufacturer, but i haven't had a single problem with the stuff I've used. 

 600v PTFE wire is pretty common from the likes of belden, etc.


----------



## audionut

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_You mean you grounded the negative input on the amp board, right?_

 

Yes, sorry for not clarifying. My KGSS works perfect with my unbalanced Onkyo CD player with negative input on amp board grounded.


----------



## spritzer

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_Most of the ebay PTFE wire doesn't have a known specification or manufacturer, but i haven't had a single problem with the stuff I've used. 

 600v PTFE wire is pretty common from the likes of belden, etc._

 

Unless I know the true voltage handling of the wires then I wouldn't risk using it for the HV in any amp. The navships stuff is fine for LV wiring and input but I use Belden 600v wire for the higher voltages.


----------



## n_maher

Are we sure the 269JX/369JX are acceptable? I know they're noted in the BOM but the same BOM says the required current capacity is > 65mA which to me means "greater than". The JX trafos are rated at 60mA.


----------



## sachu

They are the right ones Nate.


----------



## ericj

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Are we sure the 269JX/369JX are acceptable? I know they're noted in the BOM but the same BOM says the required current capacity is > 65mA which to me means "greater than". The JX trafos are rated at 60mA._

 

The 269jx has been used successfully with the follower mod that preceeded the CCS addition and has similar current load, and the hammond datasheet says 500V C.T. @ 69ma RMS: 

http://www.hammondmfg.com/pdf/5c0026-27.pdf


----------



## macm75

I'd recommend...
ApexJrWire
 Call if you need higher voltage (>600V) rated wire.

  Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_100ft of 600v wire is around $18 from digikey (compared to $30 at Mouser) but I'm gonna keep looking around_


----------



## sachu

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_I'd recommend...
ApexJrWire
 Call if you need higher voltage (>600V) rated wire._

 

Agreed..


----------



## les_garten

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_I'd recommend...
ApexJrWire
 Call if you need higher voltage (>600V) rated wire._

 

I didn't see the voltage rating listed?


----------



## macm75

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_I didn't see the voltage rating listed?_

 

Hmmm. You're right. I ordered from Steve before and I remember going thru the detail of the wire being rated at 600V. He also offered thicker PTFE cased wire rated at (if I remember correctly) 1000V. Anyway, I gave him a call and left a message. If he calls back I'll post.


----------



## les_garten

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_Hmmm. You're right. I ordered from Steve before and I remember going thru the detail of the wire being rated at 600V. He also offered thicker PTFE cased wire rated at (if I remember correctly) 1000V. Anyway, I gave him a call and left a message. If he calls back I'll post._

 

Thanx! I've been loking for 600-1000v wire as well.


----------



## runeight

Gents, I didn't order today. I got some last minute requests. One to be taken off the beta list and a few individuals who want boards but wish to remain anonymous for the moment.

 Here's our public list. Thanks to all of you on it.

 I'll order tomorrow.

 I guess we're ok on the 269JX/369JX???

 Are there other problems with the latest BoMs??


----------



## BoilermakerFan

A day late, but somehow the ortho underground or Stax mafia didn't tip me off to this awesome amp and beta build... 

 Alex, I sent you a PM, but I'd be willing to cover anyone who backs out if the order has already been placed, or I'm in for one of each. 

 I have Kabeer's 950's here for testing.


----------



## macm75

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_Hmmm. You're right. I ordered from Steve before and I remember going thru the detail of the wire being rated at 600V. He also offered thicker PTFE cased wire rated at (if I remember correctly) 1000V. Anyway, I gave him a call and left a message. If he calls back I'll post._

 

Got a message back from Steve at ApexJr. All the wire you see on the PTFE portion of the site is 600V rated. He also confirmed he has the 1000V rated wire - call for availability and pricing.


----------



## macm75

Even though I dropped out of the beta test (sorry guys, I did just finish the Gilmore "All-Triode" amp and although I'd love to perform the comparison, one amp is enough for now) I did do a little research on the power transformers. FYI, I called Heyboer transformers (Michigan, USA) and asked for a quote to match the Hammond 269JX as a reference. It would be $90 a piece or $60 if 10 were purchased. My guess the build quality would beat Hammond but that is high - just thought I'd share the info.
 The other option I wanted to share is the Edcor model XPWR013 - 510VCT at 125mA and 6.3VCT at 4A - $43.50. This transformer is much more beefy and basically the same price as the 269JX. If your house voltage is high like mine (123-125VAC) the Edcors will have a lower measured secondary voltage. Hammond states primary as 115VAC, Edcor states 120VAC which is how they measure their secondaries against (I confirmed this with Edcor but not with Hammond). 
 Enjoy the builds and happy listening.


----------



## runeight

Fortunately, I had a busy day today so order didn't go in first thing. And this allowed two more individuals to join.

 But, order has been placed. Figure about 2 weeks before I have boards in had. I will start collecting parts so that I can build quickly once I have them to verify build.

 I've only really ordered what we need so there won't be any extras except a few sand boards because you guys want mostly the tube version.

 Now to the website.


----------



## macm75

Quote:


  Originally Posted by *sergery* /img/forum/go_quote.gif 
_what would be an appropriate value for a pot?? I am eying one of the balanced attenuators from either these guys or their competitors these guys. 

 Thanks

*edit:* doh, cross post!!!_

 

Even cheaper ChinaAttenuators - all parts included but you have to build yourself. Mine arrive to East Coast USA in 10 days. Check out their store - they also have dual mono versions, all included, at a whopping $11.


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Fortunately, I had a busy day today so order didn't go in first thing. And this allowed two more individuals to join.

 But, order has been placed. Figure about 2 weeks before I have boards in had. I will start collecting parts so that I can build quickly once I have them to verify build.

 I've only really ordered what we need so there won't be any extras except a few sand boards because you guys want mostly the tube version.

 Now to the website. 
	

	
	
		
		

		
		
	


	


_

 

So, did I make the cut coach?


----------



## runeight

Yes.


----------



## Emooze

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_Even cheaper ChinaAttenuators - all parts included but you have to build yourself. Mine arrive to East Coast USA in 10 days. Check out their store - they also have dual mono versions, all included, at a whopping $11._

 

You are quite the deal hunter! I think I just found my volume, even cheaper than an Alps Blue...


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes. 
	

	
	
		
		

		
		
	


	


_

 

Sa-Weet! 

 Thanks Alex! 

 FWIW, my attenuator will be a balanced OptiVol. Two matched OptiVols operated by one ALPS Blue Velvet. I'll have to tweak the Opti's final resistor values to match the channels as close as I can, but at least the potentiometer is removed from the signal path.


----------



## BoilermakerFan

Can you clarify one dimension for me?

 Is the 170mm x 95mm the PCB size for both board while connected or for each board when separated? 

 I have a special enclosure I'd like to use and they should all fit, but I want to make sure.


----------



## macm75

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_You are quite the deal hunter! I think I just found my volume, even cheaper than an Alps Blue..._

 

Also referenced in the auction, this is a must read if you purchage the kit...
Stepped Attenuators are Sooooo Muchhhhhh Funnnnn
 I like the statement about easily swapping out the resistors you use for your favorite settings with your favorites boutique resistors. Keep the cheap stuff in for setting you don't normally use. Put different ones at different settings and see what flavor you like the best. Fun and cheap


----------



## studeb

where does one get Stax jacks these days.
 i have been looking, but..........


----------



## macm75

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_where does one get Stax jacks these days.
 i have been looking, but.........._

 

http://www.head-fi.org/forums/f6/sou...ectors-204916/
 Start at post #12
 Frank was very kind enough to send me a bunch a couple months ago. Mine are in service - perfect. Only issue is they were 6 pin and the middle had no connector - it was an empty hole. Perfect for hi bias (580V) but cannot use for low bias (230V). I got a few 6 pinners from Allied way back - not sure if they are still in stock.


----------



## runeight

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Can you clarify one dimension for me?

 Is the 170mm x 95mm the PCB size for both board while connected or for each board when separated? 

 I have a special enclosure I'd like to use and they should all fit, but I want to make sure._

 

The size is for both channels on a single board. The boards will be scored, however, so you can separate them if you want to.


----------



## ericj

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_You are quite the deal hunter! I think I just found my volume, even cheaper than an Alps Blue..._

 

You have no idea how good of a deal that is. 

 Just buying the resistors from mouser is more than that. 

 I hope the switch quality is good, though.


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_The size is for both channels on a single board. The boards will be scored, however, so you can separate them if you want to._

 

*gobsmack* No way! I had it pegged at one of those boards per channel.


----------



## runeight

Beefy you're just going to have to build one.


----------



## Beefy

HEH! I could actually fit both the tube and sand variants in my intended case at the same time......


----------



## scompton

Is there an alternative to Z3-Z8. It's back ordered at mouser and I haven't been able to find that particular Zener anywhere else.


----------



## runeight

Yes, is in the latest BoM. Attached. If not here let me know and I'll update the zip.


----------



## runeight

Sorry, wrong zip. This one.


----------



## macm75

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_You have no idea how good of a deal that is. 
 Just buying the resistors from mouser is more than that. 
 I hope the switch quality is good, though._

 

Yeah, I hear you. Not sure how it is possible but it is real. No pinching required. Plus they are supplied as stepped 2 x 24 dividers, not the ladder type. Switching mechanism feels extremely solid - zero play - tight. Contacts appear to be silver coated.
 The switches look identical as ones linked a few pages ago only without the installed resistors. 
 Same exact one Dave Slagle uses in conjunction with his autoformer...
intact audio


----------



## Coreyk78

Is the 269JX suitable for the SS amp as well? Or do I need to use the lower voltage triads?


----------



## sachu

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_Is the 269JX suitable for the SS amp as well? Or do I need to use the lower voltage triads?_

 

The triads will do fine.


----------



## Beefy

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_The triads will do fine._

 

I think the question isn't whether the Triads are fine, but whether the extra spent on the 269JX will be acceptable.

 For my money, I'd want a transformer that can do both the SS and tube builds, and I'm pretty sure the Hammond is a good option for this.


----------



## Coreyk78

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_OK. New BoMs with alternates for the missing parts.

 The 68k is 2%. Close enough._

 

The alternate you listed has a 14.2mm body length, but the bom lists a 12mm lead spacing requirement. If there is extra room around it I suppose that a vertically angled installation would be fine, but if its pretty tight around there I don't know. 
 Mouser does have a 5% resistor in stock with a 10mm body, maybe a little too loose on the tolerance though?
PR02000206802JR500


----------



## sachu

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I think the question isn't whether the Triads are fine, but whether the extra spent on the 269JX will be acceptable.

 For my money, I'd want a transformer that can do both the SS and tube builds, and I'm pretty sure the Hammond is a good option for this._

 

I misread that....yeah..I am running my SS exstata with a 270AX


----------



## Coreyk78

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I think the question isn't whether the Triads are fine, but whether the extra spent on the 269JX will be acceptable.

 For my money, I'd want a transformer that can do both the SS and tube builds, and I'm pretty sure the Hammond is a good option for this._

 

That's what I was trying to get at, in a roundabout way. I didn't know if there was an actual need to use the lower voltage triads. Plus, the 269JX is only $10 more than a pair of the Triads. 

 I'm going to go with the Hammond.


----------



## runeight

This resistor is tombstoned so it can be a little longer without presenting any difficulties. 
	

	
	
		
		

		
			





 The 269JX will work for both amps because it has the heater winding too. For the SS you would just not use it.

 I know you guys have looked at the BoM but remember that you will need two of the triads for the SS version. In most cases, even two of them are cheaper than the Hammond.


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Sorry, wrong zip. This one._

 

Alex, scompton asked about the replacement for Z3-Z8. I opened your latest zip, and looks like it's still the one listed that's on back order. In post #434, I had listed a replacement that the Mouser tech found for me 78-1N4757A. Is this the one you wanted to list in your latest BOM for Z3-Z8 and is it ok to use this replacement for the 51V zeners?


----------



## runeight

Yes. Sorry. Too many spreadsheets. 
	

	
	
		
		

		
		
	


	




 Edit: In fact, that's the one that should have been there in the first place.


----------



## runeight

New rev of the BoMs with good 51V zener alternatives.


----------



## runeight

I see that I missed a few posts between questions about the transformer. You guys had already answered the question.


----------



## runeight

Can't get the website far enough along tonight, but you guys probably would like to have the silk layouts. Here they are:

Power Supply

Solid State

Tube


----------



## runeight

With a little extra work tonight I got a portion of the website up. The PS design will be new for all of you. Along with the use of series resistors in the amps.

 And, hopefully, the explanations will be useful too.

Cavalli Audio

 See the eXStatA link under designs in the works.


----------



## runeight

There are at least three of the beta builders from Australia. I have forgotten who you all are. Could you guys PM me so I can connect you in case you want to work together on shipping/parts.

 Thanks.


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_With a little extra work tonight I got a portion of the website up. The PS design will be new for all of you._

 

Love it...... 'Maxxed' by swapping in just two CRD's! 
	

	
	
		
		

		
			





 Also, I'm surprised at how simply the bias voltages are obtained. I know little-to-nothing of electrostatic phones, but I always imagined it would be more complex than that.


----------



## spritzer

Stax used to just grab them off the B+ in the normal bias days, fed through a voltage divider. Makes it very simple to get 500V+ bias on the old amps.


----------



## runeight

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Love it...... 'Maxxed' by swapping in just two CRD's! 
	

	
	
		
		

		
		
	


	




 Also, I'm surprised at how simply the bias voltages are obtained. I know little-to-nothing of electrostatic phones, but I always imagined it would be more complex than that._

 

Seems like everything is "maxed" these days. 
	

	
	
		
		

		
		
	


	




 There are a number of ways to get bias voltages in an HV supply. This was the easiest way I could think of to make simple, variable supplies with two different bias ranges. The other thing that I like to do is to keep the bias supplies (half wave rectified junk) away from the regulated B+ so they don't introduce noise. This is a small thing, but one of my many quirks.


----------



## audionut

Thing I like most about this power supply vs the KGSS I built, is the fact you don't have to build a seperate low voltage supply (+/- 15V) for the input stage. Keeps you from having to get another xfmr and keeps cost down. Can't wait to get boards and put this baby together!!


----------



## runeight

The KGSS is a really nice piece of work. I imagine it sounds pretty good.

 It could easily be modified to eliminate the 15V transformer by removing the top portion of the current tunnel and replacing this with a pair if pfets (like in this amp) that are tied to the + rail. As in this amp I don't think you'd need a tail ccs, just a resistor. Elminate the nfet front end entirely.

 My guess is that its performance would be about the same, but I haven't really looked at this, but it is similar to what Andreas has done in his amps.


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_The KGSS is a really nice piece of work. I imagine it sounds pretty good.

 It could easily be modified to eliminate the 15V transformer by removing the top portion of the current tunnel and replacing this with a pair if pfets (like in this amp) that are tied to the + rail. As in this amp I don't think you'd need a tail ccs, just a resistor. Elminate the nfet front end entirely.

 My guess is that its performance would be about the same, but I haven't really looked at this, but it is similar to what Andreas has done in his amps._

 


 Yes, it does sound really good, but was a bit of a pain to build, as I'm one of the few who are crazy enough to have built mine P2P
	

	
	
		
		

		
		
	


	




 I actually call it my "Frankenstein Amp" cuz it's built with different parts that I decided on myself. For example, the dual +/- 15V supply is the exact same supply from the CK2III. I just built it seperately on a perf board to supply the input stage. Saved a ton of money on main xfrm, as I didn't have to have a custom one built.
 Anyway, like you suggest, it could be modified to eliminate the 15V supply, but I think I'll leave it as is. That way I can do some comparisons when I get my extata hybrid up and running. The KGSS is well worth the effort, even though sourcing parts was somewhat challenging. Like Ericj, I have often wondered why there weren't many, if any, viable choices for stat amps, especially since there's SO many great DIY dynamic phone amps. That's another thing that the exstata should hopefully eliminate, and make a good quality, easily sourced, and not too expensive option for DIY's to build. Thanks again, Alex and to all that have been involved in making this happen
	

	
	
		
		

		
		
	


	




 Oh, and by the way, I believe I had about $400-450 in parts, minus casing, in my KGSS build, just for cost comparison. Tommy.


----------



## Emooze

I think I know what I'm building next then...


----------



## runeight

This schematic by Andreas Rauenbuhler is essentially a KGSS with the front end the way I described it. Except that Andreas uses a CCS on the tail of the diff amp and I don't think you need it.

SS Amp


----------



## audionut

Alex, Looking at the extata power supply, will we actually see +/- 300V when measured with DMM? The 291V zener string is what makes me ask. Just curious.


----------



## runeight

Ah. You're paying attention. 
	

	
	
		
		

		
		
	


	




 The primary zener string will heat up from the internal PD and, as a result, the zener voltages will drift upward. In all of the proto builds the rails wound up only slightly less than 300V or over by less than 7V.

 Once the PSs came to temperature they were stable.


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Ah. You're paying attention. 
	

	
	
		
		

		
		
	


	




 The primary zener string will heat up from the internal PD and, as a result, the zener voltages will drift upward. In all of the proto builds the rails wound up only slightly less than 300V or over by less than 7V.

 Once the PSs came to temperature they were stable._

 

Yes, I like learning different things and your explanations are always great! One other one for you. Will the PS schematic on your website eventually be redrawn to show CRD1, CRD2, as replacing R13, R14? Oh, and now that I think about it, my +/- 350 supplies on my KGSS start out at 349V and end up somewhere around 355-356V.


----------



## runeight

No, the maxxed schematic is on a separate page and it shows the CRDs. They don't have a special place on the board, but go onto the same pads as R13, R14. If you look at the silk drawings you will see that R13, R14 have diode markings on them to show the correct orientation.


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_






 No, the maxxed schematic is on a separate page and it shows the CRDs. They don't have a special place on the board, but go onto the same pads as R13, R14. If you look at the silk drawings you will see that R13, R14 have diode markings on them to show the correct orientation._

 

Duh, Didn't see the maxxed PS tab, hate it when that happens, been a long week!!


----------



## runeight

Gents, I'm working on the website and I realized that I need to make a BoM change. The PS BoM has two 10k/25W load resistors. These are dummy loads for bringing up the PS. However, with the addition of the CCSs, one of these resistors must be changed to 8k2/25W. I will work on this, but I hope that none of you has bought these resistors yet.


----------



## runeight

I have added the INSTRUCTIONS pages and the SETUP page for the power supply only. The amp setups will have to wait a while.

 A few of you have asked about how to pay for boards now. Thanks for this.

 We are going to wait until I have sucessfully built one PS and one SS board so that I know that the CCS additions have not messed up the builds.

 If all is well then I will ask you guys for your shipping info and start the process of shipping boards off to you. Figure about $20 per two board set. $40 for both amps and their associated PSs. Plus the packaging and shipping.

 But, no one pays until I know the changes have not affected the builds. 
	

	
	
		
		

		
		
	


	




 I am working with wiatrob to see if we can at least provide you with matched quads on the jfets. Don't know if this will be possible yet.


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Gents, I'm working on the website and I realized that I need to make a BoM change. The PS BoM has two 10k/25W load resistors. These are dummy loads for bringing up the PS. However, with the addition of the CCSs, one of these resistors must be changed to 8k2/25W. I will work on this, but I hope that none of you has bought these resistors yet._

 


 I bought mine already, but can get the correct ones once you've gotten that info. FYI, when I built the KGSS, KG wasn't real specific on what value resistors for the load when testing the PS. Can't remember what value I used, but think they were 15K 25W. Aparently, the values for the PS load resistors on the extata are more critical?


----------



## runeight

Yes, that's correct. With a series regulator (KGSS) you just need to place a reasonable draw on the PS to ensure that it's working.

 With a shunt reg any current that is not passing through the load goes through the shunt devices. If the PS has no load at all the MJE transistors will burn up very fast. In actual operation they only have 2-3mA in them keeping their power dissipation within spec and the capacity of the heatsinks.

 So we must load the PS (while testing) with resistors that approximate the actual load. In the original design both rails pulled about the same current, hence, two of the same (10K) resistors did the trick. In the new design the negative rail must supply about 6 more mA and so the dummy load has to add this drag on the PS.

 Another way to do this will be to put a 51k/5W resistors in parallel with the 10k that is loading the negative rail. Mouse doesn't seem to have any 8k2/25W in stock or that will be in stock anytime soon.

 I've also noticed that 10k/25W are in short supply except the ohmites. Might need to have them as alternates on the BoM.

 Alas, the challenges of getting a new amp out the door.


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes, that's correct. With a series regulator (KGSS) you just need to place a reasonable draw on the PS to ensure that it's working.

 With a shunt reg any current that is not passing through the load goes through the shunt devices. If the PS has no load at all the MJE transistors will burn up very fast. In actual operation they only have 2-3mA in them keeping their power dissipation within spec and the capacity of the heatsinks.

 So we must load the PS (while testing) with resistors that approximate the actual load. In the original design both rails pulled about the same current, hence, two of the same (10K) resistors did the trick. In the new design the negative rail must supply about 6 more mA and so the dummy load has to add this drag on the PS.

 Another way to do this will be to put a 51k/5W resistors in parallel with the 10k that is loading the negative rail. Mouse doesn't seem to have any 8k2/25W in stock or that will be in stock anytime soon.

 I've also noticed that 10k/25W are in short supply except the ohmites. Might need to have them as alternates on the BoM.

 Alas, the challenges of getting a new amp out the door. 
	

	
	
		
		

		
		
	


	


_

 

No worries! If the 51k/5W's are available, will get them, but will wait for final word from you. I got my 10K25W's from mouser, but didn't notice whether they were in short supply or not. Haven't even looked at them, as all my parts came in yesterday, exept tubes (this Monday).


----------



## runeight

Gents I have added all the setup instructions for the three boards. I think you guys have enough information now on the website to know pretty much what to expect. I'll add more information slowly over the next few weeks.


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Gents I have added all the setup instructions for the three boards. I think you guys have enough information now on the website to know pretty much what to expect. I'll add more information slowly over the next few weeks._

 

Um, Curiosity getting the better of me again! Reading through the HV bias setup, you're saying to measure the bias at the test point and get reading the second lead touches the TP. Looking at the silkscreen, looks like the TP for measuring bias is after R19 4.7M resistor? When building the KGSS, KG had specifically said to measure bias before the the 4.7M, or, like you said, it would load down the bias due to the 10M input that most all DMM's have. On the extata bias supply, could you do the same and measure before the 4.7M to set bias?
 Again, just trying to learn how this bias circuit might differ from the KGSS bias. Thanks.


----------



## runeight

Ah, it may look that way, but it isn't. 
	

	
	
		
		

		
		
	


	




 The testpoints are before the 4M7 resistors just like they should be.


----------



## wiatrob

I happen to have a bunch of J271s. I have been matching them into quads - and am hitting very good numbers so far, Would anyone be interested in these?

 Here's the catch: I don't intend to profit from this, but I need to recoup my parts costs, shipping, rejects... Would it be considered unethical to ask a few dollars for a matched quad? It would cost $4.80 plus shipping from Mouser to get the 10 parts recommended for a match.

 Let me know what you think a fair cost would be, and I'll keep matching quads to see how many sets I can provide, along with how many rejects I have. Then we'll see if this works.

 My thought was to provide these to Runeight to ship out with boardsets if there is a desire to have them...


----------



## scompton

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I happen to have a bunch of J271s. I have been matching them into quads - and am hitting very good numbers so far, Would anyone be interested in these?

 Here's the catch: I don't intend to profit from this, but I need to recoup my parts costs, shipping, rejects... Would it be considered unethical to ask a few dollars for a matched quad? It would cost $4.80 plus shipping from Mouser to get the 25 parts recommended for a match.

 Let me know what you think a fair cost would be, and I'll keep matching quads to see how many sets I can provide, along with how many rejects I have. Then we'll see if this works.

 My thought was to provide these to Runeight to ship out with boardsets if there is a desire to have them..._

 

I'm interested. Whatever you want to charge is fine.


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Ah, it may look that way, but it isn't. 
	

	
	
		
		

		
		
	


	




 The testpoints are before the 4M7 resistors just like they should be._

 

OK, cool, that part's the same then. I just measured the bias on my KGSS before the 4.7M, and like you said, the momentary touch of probe is the most accurate reading before meter starts to load it down. I knew that measuring after the resistor would load it down to about half in a heart beat. Just didn't remember it being quite so critical when measuring before resistor to get the reading as soon as lead makes contact. Mine right now, is reading a hair over 600V, which is fine for the ESP950's. Thanks again for clarifying. I learned a ton when building the KGSS, but am already learning more with this amp.


----------



## Emooze

How many are you buying at a time to get 25 pieces for $4.80? Either way I'd be interested even if the price was over that


----------



## BoilermakerFan

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I happen to have a bunch of J271s. I have been matching them into quads - and am hitting very good numbers so far, Would anyone be interested in these?

 Here's the catch: I don't intend to profit from this, but I need to recoup my parts costs, shipping, rejects... Would it be considered unethical to ask a few dollars for a matched quad? It would cost $4.80 plus shipping from Mouser to get the 25 parts recommended for a match.

 Let me know what you think a fair cost would be, and I'll keep matching quads to see how many sets I can provide, along with how many rejects I have. Then we'll see if this works.

 My thought was to provide these to Runeight to ship out with boardsets if there is a desire to have them..._

 

I'm interested. Your time has a value. It's a hobby, but it still has a value. Determine what that value is and how long it takes to match them, spread it over the quads and the number of builders and I think you have a fair adder for your time. Unless of course you want $150/hr, which I can better spend on a female companion who doesn't care what my real name is... 
	

	
	
		
		

		
		
	


	




 Edit: I'm definitely in Bill, for two sets, one for the SS and one for the hybrid.


----------



## wiatrob

oops - mouser = 10 pcs for 4.80!

 Getting more rejects in this next batch. But one bonus is that i will have a lot of very close and exact matches.


----------



## Emooze

You're providing a service and a guarantee. I really appreciate that and I'd be ok with you taking a profit, hahaha.

 Put me down for one set, SS, please


----------



## HeadphoneAddict

I can't see anyone complaining about your matching the sets and getting paid back for the parts, rejects, shipping, etc. It's highly appreciated!


----------



## pabbi1

I'd like to point out the matching service has GREAT value - my last 10 j271 from Mouser yielded (in mA):

 7.4
 7.7
 8.4
 9.1
 13.2
 14.2
 10.9
 11.1
 12.0
 12.0

 The point is that anything below 10 is unusable for this amp, and I have one not so greatly matched quad (just barely) within 10% in a 10 lot sample. So, you can take your chances with 10, but are HIGHLY unlikely to get a GOOD match, and may not get a match at all, or it may fall below the useable threshold.

 If I were doing this again (and I will), I'd try matching 20 to get something closer together, or just take Bill up on his gracious offer. It will yield a better result than a normal distribution.


----------



## bada bing

Another vote for offering matched sand. Cost isn't really an issue, Charge what you feel is fair and then add a beer onto the tab

 It doesn't make any economic sense at all to not have one source do the matching for a group like this. I'm happy some one wants to step up


----------



## runeight

OK. When you guys agree on price I'm more than happy to include these with your boards.

 I'm already looking forward to their arrival. Hopefully next week. Probably late next week.


----------



## TimJo

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_I'd like to point out the matching service has GREAT value._

 

Agreed. If your up to the task of doing this for us, I'm more than happy to pay whatever you feel covers your time & cost (plus a beer or two as Bada Bing said 
	

	
	
		
		

		
		
	


	




). 

 Like pabbi1 points out, $4.80 in parts doesn't even guarantee you'll end up with a good quad. Thanks for the offer of doing this Bill...


----------



## les_garten

Alex, nice job on the exstata Website! Got a few hours of fun out of it last night!


----------



## TimJo

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Alex, Looking at the extata power supply, will we actually see +/- 300V when measured with DMM? The 291V zener string is what makes me ask. Just curious._

 

 Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Ah. You're paying attention. 
	

	
	
		
		

		
		
	


	




 The primary zener string will heat up from the internal PD and, as a result, the zener voltages will drift upward. In all of the proto builds the rails wound up only slightly less than 300V or over by less than 7V.

 Once the PSs came to temperature they were stable._

 

I was wondering about this as well as I was studying the schematic at lunch yesterday.

 BTW, just curious if we will be using head-fi as the main forum during this beta process, or if your going to move us over to your website like we did for the CTH prototypes?


----------



## runeight

No, we'll do it all here.


----------



## MrMajestic2

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_OK. When you guys agree on price I'm more than happy to include these with your boards.

 I'm already looking forward to their arrival. Hopefully next week. Probably late next week._

 

i'll take match ones


----------



## TimJo

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_No, we'll do it all here._

 

Cool. In that case I'll get bonehead questions out of the way. 
	

	
	
		
		

		
		
	


	




 Am I correct in assuming that RH1 and RH2 are simply tied to star ground at the heater wiring 'distribution block' - similar to what is referred to as "Amphead's mod" on the Bijou?

 Also, I only have SE sources at this point, so all I would need to do is tie the _IG_ and _In-_ terminals together on the amp boards, and use a standard 50k two channel pot. Correct?


----------



## sachu

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Am I correct in assuming that RH1 and RH2 are simply tied to star ground at the heater wiring 'distribution block' - similar to what is referred to as "Amphead's mod" on the Bijou?_

 


 No actually, they are tied to the negative rail.

  Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Also, I only have SE sources at this point, so all I would need to do is tie the IG and In- terminals together on the amp boards, and use a standard 50k two channel pot. Correct?_

 

Yep..that's right.


----------



## runeight

And, I'm sure that everyone knows that the amp only has half the gain when driven SE because only one input is active. This is normal for a diff amp and will be true for any amp with similar topology.

 I think it's also fair to say that you will get good performance in SE mode but the amp shines more when driven balanced.


----------



## runeight

I've modified the BoM to included the needed 51K/5W dummy load resistor. And some alternatives for the 10k/25W resistors. The new BoMs are available from the website.

 I've also changed the PS setup instructions to reflect use of the new resistor. These dummy load resistors are probably the most expensive part of the parts order.


----------



## ericj

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I've modified the BoM to included the needed 51K/5W dummy load resistor. And some alternatives for the 10k/25W resistors. The new BoMs are available from the website.

 I've also changed the PS setup instructions to reflect use of the new resistor. These dummy load resistors are probably the most expensive part of the parts order. 
	

	
	
		
		

		
		
	


	


_

 

It's worth pointing out, if you're building more than one amp, make sure you don't buy more than one set of these resistors. You only need them to test the PS before you get the amp hooked up. Once you're sure the PS is working properly, the amp is all the load it needs. 

 Which, by extension, means that we can avoid some of the nastier effects of a shortage if people share their dummy load when they're done with it, if need be. 

 I've had a series of mini-disasters that have kept me from completing my 2nd PS, but once I'm done with that thing i doubt I'll ever need my 10k resistors again.


----------



## Beefy

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_Which, by extension, means that we can avoid some of the nastier effects of a shortage if people share their dummy load when they're done with it, if need be._

 

Good call. And its not like a resistor costs a lot to ship in a pre-paid padded envelope, or is likely to get damaged easily.


----------



## sachu

I have about 20 J271s..if I find more than one matched quad i'll send that along to someone who can use it free of cost. Will try and get to matching them tonight.


----------



## runeight

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_Alex, nice job on the exstata Website! Got a few hours of fun out of it last night!_

 

Thanks. I consider it to be one of my jobs to provide clean entertainment for diyers.


----------



## TimJo

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_No actually, they are tied to the negative rail._

 

Right, now that I look at the schematic for the amp again, I can see that this makes sense - it's like an elevated heater supply, but in reverse, so we don't exceed the 200 volt heater-cathode voltage limit of the 6S4, right?

 (Forgive my slowness at picking things up - I've a lot to learn yet when it comes to tubes. 
	

	
	
		
		

		
		
	


	




)


----------



## runeight

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Right, now that I look at the schematic for the amp again, I can see that this makes sense - it's like an elevated heater supply, but in reverse, so we don't exceed the 200 volt heater-cathode voltage limit of the 6S4, right?_

 

genau.


----------



## TimJo

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_genau. 
	

	
	
		
		

		
		
	


	


_

 

So I guess this would be referred to as a subterranean heater supply. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I think it's also fair to say that you will get good performance in SE mode but the amp shines more when driven balanced._

 

Yeah, a balanced phono pre amp is on my list of projects for sure, since a phono cartridge produces a balanced signal by design. That was _one_ of the reasons I bought a VPI turntable actually, because they have both SE and balanced outputs, without having to rewire the tonearm assembly.

 Any interest in adding that to your list of designs.


----------



## runeight

Yes. 
	

	
	
		
		

		
		
	


	




 I've been asked quite a bit about a phono preamp but Broskie has done a ton of first class work on phono preamps and there are good ones out there commercially and they have to be built very carefully to prevent oscillation because there is so much gain. I'm not sure that I can add anything to the body of work already done since the first RIAA curve was used oh about a million years ago. But, one never knows ... maybe there will be a compelling reason to do something.


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes. 
	

	
	
		
		

		
		
	


	




 I've been asked quite a bit about a phono preamp SNIP_

 

And if you just recently got _headphones_ - we can probably assume you don't have a turntable to test with


----------



## wiatrob

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_I can't see anyone complaining about your matching the sets and getting paid back for the parts, rejects, shipping, etc. It's highly appreciated!_

 


 I just want to tread carefully here - wouldn't want to be seen as 'cashing in' on the DIY scene. 

 I'll continue matching quads tonight and making myself sick on Halloween candy


----------



## Beefy

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I just want to tread carefully here - wouldn't want to be seen as 'cashing in' on the DIY scene._

 

Lesser people than yourself have got away with far worse


----------



## scompton

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I just want to tread carefully here - wouldn't want to be seen as 'cashing in' on the DIY scene. 

 I'll continue matching quads tonight and making myself sick on Halloween candy 
	

	
	
		
		

		
		
	


	


_

 

Well, I don't see it as cashing in, even if you make a small profit. It saves us from having to order 20 of them just to use 4. Even if 20 aren't expensive, it's still a waste.


----------



## wiatrob

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_ Even if 20 aren't expensive, it's still a waste._

 

Then I can pitch it as* 'GREEN!'*


----------



## scompton

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Then I can pitch it as* 'GREEN!'*



_

 

Exactly


----------



## runeight

OK. Since you guys are interested in the quads, wiatrob has made 22 well-matched sets of them. They will be $4 a quad and I will include them in your board shipments.

 I know that some of you have already said yes, but if we could start again on the thread, tell me how many quads you want (but a max of one set per board) and I'll add this column to the board tally.

 I'll probably place my Mouser order for the sand amp tomorrow. I'll see if everything is still in stock. 
	

	
	
		
		

		
		
	


	




 Edit: Beta list attached.


----------



## HeadphoneAddict

I'll need how ever many quads it takes to build one tube hybrid please. Of course wiatrob probably already knows that.


----------



## MrMajestic2

I'll take a set of quad for a tube amp please.


----------



## scompton

I'm going to build the sand amp first, so a set of quads for that. If you have any left over, I'll take a set for the tube amp.


----------



## Emooze

I'll take a set for the sand amp please.


----------



## runeight

I just placed my Mouser order. There were a few unexpected things out of stock.

 The RN55D 1.0k resistor (egads).

 The 100n/1kV film cap (there is an AVX alternative)

 The Bourns 200R trimpot showed out of stock but when I re-entered it was there.


----------



## TimJo

I'll take a set for a hybrid amp.


----------



## TimJo

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I just placed my Mouser order. There were a few unexpected things out of stock.

 The RN55D 1.0k resistor (egads).

 The 100n/1kV film cap (there is an AVX alternative)

 The Bourns 200R trimpot showed out of stock but when I re-entered it was there._

 

We should be able to use the 71-CCF55-1K I think. It's pretty much the same part.

 That's a bummer about the WIMA cap though. It looks like there's a place in L.A. that has them in stock. It's called TAW Electronics.

 Item: MKP 104K1KV-7
 Description: MKP10 .1/1KV/10 LS22.5 (8) RoHS 
 Quantity Available: 589

 It looks like the right part (but somebody should double check that I'm reading the P/N correctly).

 Their price is $1.43 for 25-99 pieces, so if they'll sell them to me on Monday, I'd do a group buy and maybe we could throw them in with the boards as well.


----------



## runeight

This Mallory part is the only other one that is the right size and is in stock at Mouser.

 539-160104J1000N-F

 For the 1k resistor, we can use the xicon 273 1% series. The part number is probably:

 273-1K-RC.


----------



## studeb

one set of quads per board for me.
 but can match them if you are short quads.


----------



## Coreyk78

I'll take one set of the jfets.

 I saw that the 1k resistor was out of stock, so I subbed a cmf55, the cmf series are basically identical to the rn series except they are blue and don't carry the military certification.
CMF551K0000BHEB


----------



## runeight

Good sub. And it looks like they will fit.

 Current beta list showing requested quads.


----------



## Coreyk78

Oh and maybe this could replace the backordered wima cap, its slightly wider, but has the 22.5mm lead spacing.

WIMA/MKP10-1-1600-10


----------



## runeight

Thanks. I looked at those too, but there isn't enough room on the board for the extra width.


----------



## Coreyk78

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Thanks. I looked at those too, but there isn't enough room on the board for the extra width._

 

Ah, ok. I also just looked at those trimpots, only shows 1 left in stock


----------



## runeight

Yes, we're going to have to make an adjustment for this problem.

 I think you can sub a 50R jobbie in here. You won't get as fine control over the current adjustment in the PS, but it will be good enough.

 Sometimes I don't understand how Mouser updates their inventory. Seems like they should have ordered this part a while ago.


----------



## awpagan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_OK. Since you guys are interested in the quads, wiatrob has made 22 well-matched sets of them. They will be $4 a quad and I will include them in your board shipments.

 I know that some of you have already said yes, but if we could start again on the thread, tell me how many quads you want (but a max of one set per board) and I'll add this column to the board tally.

 I'll probably place my Mouser order for the sand amp tomorrow. I'll see if everything is still in stock. 
	

	
	
		
		

		
			





 Edit: Beta list attached._

 

I'll be in for 2 sets of quads.


----------



## Emooze

Has anyone tried looking at Digikey? I know I have to get the Triads there so they might have the part that Mouser doesn't.


----------



## runeight

Gents, I've been looking over the boards again. It is a habit. 
	

	
	
		
		

		
			





 I see that there is one potential HV problem. This will not affect anything important

 The traces that bring the power LED runs to the terminal block are only about 30mils away from the pads for the bias output. This is a bit close for the 600V bias supply.

 The only significant consequence of this is that we might not be able to use the off-board power LED. I'll find out when I build my new PS. We didn't even have provision for this LED on the original PS. It was a request from one of the prototypers.

 All else looks good after a second look after some time away.


----------



## sergery

I'm in for a quad


----------



## runeight

We're halfway there on the quads. Attached.

 I'm also ordering 20 jfets. Maybe I'll get a couple of quads from them too.


----------



## n_maher

If someone is willing to match parts to help the prototypers I'd be up for buying some.


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_We're halfway there on the quads. Attached.

 I'm also ordering 20 jfets. Maybe I'll get a couple of quads from them too._

 


 I'm in for a quad for each amp...


 And in the spirit of low cost enclosures for the hybrid version, I snagged a unique piece of kit that will be repurposed as my amp chassis. I will spend the time to refinish it, but keep the side panels stock and try to source as many film and lens pieces as I can for the feet, knobs, etc.:

Vintage SYLVANIA 600 Tube TV Filming CAMERA PROJECTOR - eBay (item 370279810048 end time Oct-31-09 13:58:01 PDT)

 The SS version will go into a NABU with my usual customizing, which means I'll do all the sheetmetal work, then have them blasted and sprayed by a local body shop for a black chassis and colored, pinstriped top; all labels installed or painted on before clear coats are applied. The front panel will be a piece of figured wood, to be determined based on what a friend has available.


----------



## sergery

at 12" x 7" x 6" it will be a squeeze. Were you planning to have a separate power supply and amp section?


----------



## BoilermakerFan

Quote:


  Originally Posted by *sergery* /img/forum/go_quote.gif 
_at 12" x 7" x 6" it will be a squeeze. Were you planning to have a separate power supply and amp section?_

 

I'll probably house the transformer separately and divide/shield the PSU from the amp. The 7" is the width, so I should be able to get the amp board at the front and have the PSU over and back shielded off. The depth is the 12" so I have the room if I keep the transformer out. I have my eye on a couple of other vintage chassis/PSUs that I can use and connect the two with a nice fat umbilical cord to minimize voltage drop and I'll upsize my VA a hair too. My only concern is voltage drop on the heater taps so I may handle those as a separate shielded toroid inside the PSU section, but I haven't check the dimensions of the Hammond 380 to see if it would still fit inside the chassis. 

 I'm watching other auctions with snipe bids set too, so if the TV camera doesn't work, I'll have other old vintage chassis to use.


----------



## bada bing

Two sets of JFETs, (sand and hybrid) if available for me.


----------



## runeight

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_If someone is willing to match parts to help the prototypers I'd be up for buying some._

 

Nate, do you mean more than just the jfets?


----------



## runeight

Gents, we have at least two beta builders from Australia, maybe three.

 Would there be anyone on the team who could help these gentlemen with the parts?? Unfortunately, I've got my hands full at the moment, although I can step in if needed.

 Thanks for thinking about it.


----------



## n_maher

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Nate, do you mean more than just the jfets?_

 

The jfets seem to be the part that requires matching by quad, the other stuff looked pretty trivial. At least at first glance. I admit to not being all the way into this project just yet.


----------



## Beefy

Question on the JFETs while everyone is talking about them...... could a case be made to socket them? It seems that matching by IDSS is a good start, but may not guarantee perfect matching.


----------



## runeight

A case could be made, but I don't know that we are ever going to get so far as to match gm on these guys since, so far as I know, it is a dynamic measurement. Unless you know someone who has a scope where this is a built-in function or has already put together the rig for this.


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_A case could be made, but I don't know that we are ever going to get so far as to match gm on these guys since, so far as I know, it is a dynamic measurement. Unless you know someone who has a scope where this is a built-in function or has already put together the rig for this._

 

I don't think I'd bother Alex

JFet matching and measured distortion - Part1 - diyAudio

JFet matching and measured distortion - Part 2: LTP - diyAudio


----------



## luvdunhill

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Question on the JFETs while everyone is talking about them...... could a case be made to socket them? It seems that matching by IDSS is a good start, but may not guarantee perfect matching._

 

I think the exercise is less useful for "matching" and more for "selecting", i.e. choosing the devices with the larger Yfs


----------



## FrankCooter

All those who requested the 5 pin Amphenol "Stax type" jacks and provided a mailing address have been sent a package. If you don't receive yours by the end of the week or there's a mistake in the contents, let me know.


----------



## pabbi1

Plenty of tubes are still available as well, especially two octets of matched construction (same mfg, plate, getter, etc) as well as matched pairs.


----------



## ericj

If nobody else is stepping up to get parts out to australia i guess i can help with that. 

 I would need to know what parts they specifically are going to have trouble acquiring without help in the US, the best way to get stuff out to them, and how they expect to pay. 

 And their shipping addresses, i guess.

 Edit: Oh, regarding the 269jx - i got mine from Angela Instruments on friday, and the sticker on the top does say "60madc" - which would appear to contradict the datasheet. In any case it's the right transformer for the job.


----------



## Beefy

As an ex-Aussie DIY'er...... so long as everything is in stock at Mouser, then people shouldn't have too much trouble going it alone. It only gets difficult and expensive when you have to worry about multiple vendors.


----------



## nattonrice

Yep~ as long as the bom you're working from doesn't span all of the state side suppliers then it is ok =]


----------



## runeight

Beta builders and quads.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Plenty of tubes are still available as well, especially two octets of matched construction (same mfg, plate, getter, etc) as well as matched pairs._

 

Al, if your willing to sell a matched octet, I'm in for one. Just let me know the total in the email.


----------



## sergery

Well, I am not that excited about giving up half of the gain by using a single ended source. I suppose I should build and listen to it first before drawing any conclusions but already I have begun to plot and scheme. My first thought was a pair of 'symmetric cmoy's' with opa1632's, something super simple like the attached photo. Taken from TI's website. Seems like the most expensive part would be the power supply.

 Think is is worth the trouble, or will SE deliver the goods - volume and sq, to a satisfying extent?


----------



## runeight

The only issue might be a compromise in SQ. This is because I think you want the opamp to have unity gain. Which means that there will be, essentially, 100% feedback. Opamps seem benign, but 100% feedback will have an affect on the sound passing through the opamp. How much I don't know.


----------



## n_maher

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Beta builders and quads._

 

I see I'm not marked down for any quads, is that because they are all spoken for? If so, that's ok, I'll plan to match my own.


----------



## ericj

Quote:


  Originally Posted by *sergery* /img/forum/go_quote.gif 
_Well, I am not that excited about giving up half of the gain by using a single ended source. I suppose I should build and listen to it first before drawing any conclusions but already I have begun to plot and scheme. My first thought was a pair of 'symmetric cmoy's' with opa1632's, something super simple like the attached photo. Taken from TI's website. Seems like the most expensive part would be the power supply.

 Think is is worth the trouble, or will SE deliver the goods - volume and sq, to a satisfying extent?_

 

Something like that, or something based on a pair of THAT1646 which are only about $4.50 each from mouser. 

 Addinng a split LV power supply is annoying, though. For me it's not even the cost - i can have a dual regulated +/-15v supply in a few hours out of parts laying around here.


----------



## runeight

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I see I'm not marked down for any quads, is that because they are all spoken for? If so, that's ok, I'll plan to match my own._

 

Only because you haven't indicated interest yet. Do you want one or two quads?


----------



## n_maher

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Only because you haven't indicated interest yet. Do you want one or two quads? 
	

	
	
		
		

		
		
	


	


_

 

Two please.


----------



## runeight

Quad consumption.

 There is only one left from wiatrob's collection. I may get one or two from the 20 jfets that I ordered.


----------



## TimJo

Quote:


  Originally Posted by *sergery* /img/forum/go_quote.gif 
_Well, I am not that excited about giving up half of the gain by using a single ended source. I suppose I should build and listen to it first before drawing any conclusions but already I have begun to plot and scheme.

 (snip)

 Think is is worth the trouble, or will SE deliver the goods - volume and sq, to a satisfying extent?_

 

 Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_The only issue might be a compromise in SQ. This is because I think you want the opamp to have unity gain. Which means that there will be, essentially, 100% feedback. Opamps seem benign, but 100% feedback will have an affect on the sound passing through the opamp. How much I don't know._

 

Not to derail the thread, but this was something I was looking at this weekend...

Aikido Single-Ended-to-Balanced Topology

 Scroll down about a third of the way.


----------



## wiatrob

Or Just pick up an Opus dac, build it into the amp and it becomes a moot point!


----------



## TimJo

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Or Just pick up an Opus dac, build it into the amp and it becomes a moot point!_

 

I know. I wish I listened to more digital stuff. I guess I'm just stuck in an analog daze.


----------



## Beefy

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_I know. I wish I listened to more digital stuff. I guess I'm just stuck in an analog daze. 
	

	
	
		
		

		
		
	


	


_

 

I would have mental unease about using vinyl (mV outputs) with electrostatic phones (kV outputs). The two just don't seem to go together.....


----------



## Lou Erickson

Even with my vintage/budget/lousy setup, vinyl and electrostatics go together nicely.


----------



## ericj

Quote:


  Originally Posted by *Lou Erickson* /img/forum/go_quote.gif 
_Even with my vintage/budget/lousy setup, vinyl and electrostatics go together nicely. 
	

	
	
		
		

		
		
	


	


_

 

Stax even made phono preamps with built in 'stat output.


----------



## sergery

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Not to derail the thread, but this was something I was looking at this weekend...

Aikido Single-Ended-to-Balanced Topology

 Scroll down about a third of the way. 
	

	
	
		
		

		
		
	


	


_

 

Interesting, things start to get complicated though...
  Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Or Just pick up an Opus dac, build it into the amp and it becomes a moot point!_

 

Yeah, I if I had no dac I would consider it a major option. I have a gamma 1 though and it seems cost effective to upgrade to a gamma2 which will be basically a maxed opus for not much $$$. additionally it won't need a power supply .

  Quote:


 The only issue might be a compromise in SQ. This is because I think you want the opamp to have unity gain. Which means that there will be, essentially, 100% feedback. Opamps seem benign, but 100% feedback will have an affect on the sound passing through the opamp. How much I don't know. 
 

Does this mean that all buffers have poor sound quality
	

	
	
		
		

		
		
	


	




 or have I missed your meaning? (seems the case
	

	
	
		
		

		
		
	


	




)

 thanks for the feedback

 sorry for the ot, just trying to get setup for the exstata


----------



## manaox2

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Or Just pick up an Opus dac, build it into the amp and it becomes a moot point!_

 

ooo, your giving me evil ideas here.


----------



## runeight

Quote:


  Originally Posted by *sergery* /img/forum/go_quote.gif 
_
 Does this mean that all buffers have poor sound quality
	

	
	
		
		

		
		
	


	




 or have I missed your meaning? (seems the case
	

	
	
		
		

		
		
	


	




)_

 

It depends on the buffer. Most of the discrete buffers that are used in diy amps are made from followers. Follwers have, inherently, gain of less than 1. If the buffers are designed properly the buffer section should add or detract little from the SQ.

 An opamp, however, is a totally different story. Opamps have open loop gains of 100db to 120db (100,000 to 1,000,000). To turn an opamp into something that has a gain of 1 requires 100db or 120db of negative feedback (100%). There is no way under heaven that this amount of NFB does not affect SQ.

 If you look at opamp specs you often see a measure of whether or not they are "unity gain stable". What this means is that, since huge amounts of NFB are destablizing, can you operate this particular opamp with 100% negative feedback without its going into oscillation. Some can do this and some can't.

 The schematic above applies NFB to both sides of the opamp and gives you a formula for calculating the feedback resistors to set the gain. If you set the gain for 1 (a buffer) then you will apply 100% NFB.

 Not to say, by any means, you shouldn't try it. I just don't know what it will do to the SQ going into the amp.


----------



## sergery

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_It depends on the buffer. Most of the discrete buffers that are used in diy amps are made from followers. Follwers have, inherently, gain of less than 1. If the buffers are designed properly the buffer section should add or detract little from the SQ.

 An opamp, however, is a totally different story. Opamps have open loop gains of 100db to 120db (100,000 to 1,000,000). To turn an opamp into something that has a gain of 1 requires 100db or 120db of negative feedback (100%). There is no way under heaven that this amount of NFB does not affect SQ.

 If you look at opamp specs you often see a measure of whether or not they are "unity gain stable". What this means is that, since huge amounts of NFB are destablizing, can you operate this particular opamp with 100% negative feedback without its going into oscillation. Some can do this and some can't.

 The schematic above applies NFB to both sides of the opamp and gives you a formula for calculating the feedback resistors to set the gain. If you set the gain for 1 (a buffer) then you will apply 100% NFB.

 Not to say, by any means, you shouldn't try it. I just don't know what it will do to the SQ going into the amp. 
	

	
	
		
		

		
		
	


	


_

 

Interesting, this was exactly what I was wondering. In all honesty I was scratching my head over why some opamps could be buffers while others could not. anyway, So I find that opa1632 is rated at:
 Peaking at a Gain of 1 VO = 100mVPP 0.5 dB

 elsewhere I find:
  Quote:


 Although the ADA4817 is unity-gain stable, a high-frequency pole increases its gain-bandwidth product from 410 MHz at high gains to 1 GHz at unity gain. ...
 snip
 ...The result is 1-GHz bandwidth (−3 dB), 250-MHz gain flatness (0.1 dB) and less than 1-dB peaking for a gain equal to 1. 
 

conclusion: opa1632 is unity-gain stable (probably
	

	
	
		
		

		
		
	


	




)

 Sorry again for the ot. Thanks for your input runeight. 
	

	
	
		
		

		
		
	


	




*edit:* on second thought 100mv p-p might sound kinda noisy....


----------



## runeight

On another note, I ordered a 269JX from Angela today. It was the last one that they had in stock. Those of you who are building sand amps can use the Triads without difficulty.

 But for the tube guys, I know there are other sources for the Hammonds. I just haven't looked yet.


----------



## sachu

I have a 269JX brand new that i'd be willing to sell if someone wants..PM me.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Or Just pick up an Opus dac, build it into the amp and it becomes a moot point!_

 

I was quite impressed with the balanced OPUS DAC and eXStatA at RMAF 4 weeks ago. The Opus reminded me a bit of my Apogee mini-DAC, smooth and organic and flowing, almost analog-like.


----------



## audionut

Gentlemen, I am matching my jfets tonight and if I remember right, they needed to be within 10%, correct? I've got a set now that is 13.3, 13.4, 12.2, and 12.3. This should be a good quad, right? Thanks.


----------



## runeight

Close enough.


----------



## sergery

Can you give me an idea of the range of input power/voltages that the exstata can safely handle?? (or a hint how I might calculate it) For instance would a 2Vrms SE signal that is transformer coupled to a balanced signal be strong enough? or would further preamplification be necessary? Also what is the high side considering a route involving an opamp with Gain > 1 to increase stability (over the unity gain case).

 thanks


----------



## runeight

Good question. 
	

	
	
		
		

		
		
	


	




 The amp has a gain of approximately 1000 (give or take depending on the jfets) with a balanced input.

 So, if each side of the differential input has a peak voltage of 300mV the amp will generate 600Vpp at the output. If each side has a peak of 450mV the amp will generate 900Vpp. This is its limit.

 Most everyone's problem will not be insufficient signal but way too much. Most sources these days make around 2Vrms which is 2.8V peak (as yours does).

 So, no pre-amplification is necessary.

 The gain running SE will be 500. Most sources will still generate much more signal than is needed. 
	

	
	
		
		

		
		
	


	




 It's hard for me to choose between a good transformer and an opamp. They both have their drawbacks.

 Maybe we need to devise a phase splitter that uses discrete components. Hmmm ...


----------



## TimJo

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Maybe we need to devise a phase splitter that uses discrete components. Hmmm ..._

 

That's what peaked my interest in reading that tubecad article - but man, that's alot of tubes...


----------



## runeight

Yes, it is waaaaaaay too many components for the job we have here. I don't know if there is a simple way to do this, but there might be. Unfortunately, if there is, not in time for your beta builds.


----------



## Coreyk78

maybe not as "audiophile approved" but if you want a fairly simple way to convert SE to balanced maybe a DRV134 circuit could do the trick? These get used all the time over on diyaudio.com for driving bridge-parallel gainclone amps.

Balanced line driver


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes, it is waaaaaaay too many components for the job we have here. I don't know if there is a simple way to do this, but there might be. Unfortunately, if there is, not in time for your beta builds. 
	

	
	
		
		

		
		
	


	


_

 

maybe I can suggest something discrete. Am I allowed to use out of production parts?


----------



## sergery

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_maybe I can suggest something discrete. Am I allowed to use out of production parts? 
	

	
	
		
		

		
		
	


	


_

 

Certainly, I would be curious to see that - even if purely academic. Or can these out of production parts still be had?


----------



## luvdunhill

Quote:


  Originally Posted by *sergery* /img/forum/go_quote.gif 
_Certainly, I would be curious to see that - even if purely academic. Or can these out of production parts still be had?
	

	
	
		
		

		
		
	


	


_

 

2SJ103, 2SJ74, 2SK170, 2SK246 are used as a cascoded input stage. They can be had relatively easily.


----------



## ericj

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_maybe I can suggest something discrete. Am I allowed to use out of production parts? 
	

	
	
		
		

		
		
	


	


_

 

I think the real trick is doing it without adding additional power supply rails.


----------



## sergery

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_maybe not as "audiophile approved" but if you want a fairly simple way to convert SE to balanced maybe a DRV134 circuit could do the trick? These get used all the time over on diyaudio.com for driving bridge-parallel gainclone amps.

Balanced line driver_

 

Thanks for the link. Nice little board too. 

 It occurs to me now that the gain of any of these opamps is inconsequential as a single output resistor per channel per phase can be chosen strategically to get the voltage to the desired level. So running them at a happy, stable gain should is not an issue. Whether this is a better solution than simply building a balanced source or transformer coupling is up in the air afaik.


----------



## luvdunhill

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_I think the real trick is doing it without adding additional power supply rails._

 

I think a stand alone board with a small EI30 form factor transformer might work as an add-on...


----------



## luvdunhill

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_Balanced line driver_

 

perhaps that link isn't apropos for this thread.

 Here's perhaps a better project link:

sjostromaudio.com - UBC01 Audio Balanced Driver


----------



## TimJo

So does anyone have experience with the DRV134? Looks like a fairly simple solution.


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Good question. 
	

	
	
		
		

		
		
	


	




 The amp has a gain of approximately 1000 (give or take depending on the jfets) with a balanced input.

 So, if each side of the differential input has a peak voltage of 300mV the amp will generate 600Vpp at the output. If each side has a peak of 450mV the amp will generate 900Vpp. This is its limit.

 Most everyone's problem will not be insufficient signal but way too much. Most sources these days make around 2Vrms which is 2.8V peak (as yours does).

 So, no pre-amplification is necessary.

 The gain running SE will be 500. Most sources will still generate much more signal than is needed. 
	

	
	
		
		

		
		
	


	




 It's hard for me to choose between a good transformer and an opamp. They both have their drawbacks.

 Maybe we need to devise a phase splitter that uses discrete components. Hmmm ..._

 

Alex, On my KGSS, KG states "The amp can output 800Vp-p or 1200Vp-p with headroom. At 800Vp-p, THD is less than .008% from 20Hz to 20kHz". Reading through the article again on Headwize, he never says anything about using a balanced source, but I'm assuming he probably is? If so, then the gain on my amp would be around 400-600, correct? I'm using an Onkyo DX-7555 component CD player (SE) as the source for my KGSS, and I can say that if it's at a gain of 400-600 running SE, there's more than enough gain to blow your eardrums. I'm not sure if this adds anything to the discussion about balanced vs se, and sound quality. I personally think most will find the extata to sound fine with se sources, but won't know until some are built and comparisons done between se and balanced. I've never had the pleasure of hearing a balanced setup, so I'm only speculating. Just my random thoughts


----------



## Beefy

The gain of the amp stays the same, you are just feeding it half the signal. I don't know whether this satisfies your musing though......


----------



## jcx

Some wrong and misleading info being tossed around this thread re gain and balanced/single ended here

 The amp is a true differential amp, there is a single gain # applied to Vin difference – it doesn’t matter whether the input is SE or dual polarity/balanced with respect to gnd

 With 500:1 feedback resistor ratio the differential gain would be 1001 (assuming high enough loop gain - which the circuit doesn't have)

 There is also a small common mode gain of ~1x

 With “balanced” input the a,b stator drive signals would be +,-500.5x 

 With SE signal, - input gnded, stator a would see +501x, b –500x

 The trivial gain imbalance w/SE drive is much smaller than component tolerances – you’d need better than 0.1% tolerance feedback R and > 1e6 open loop gain for these errors to become the same order of magnitude – you could buy or match the feedback resistors but you need more active devices to get the open loop gain

 Just to spell it out in small words - - this amp doesn’t need/won’t benefit from balanced vs SE input signal -- worrying about balanced input is completely myopic audiophilia nervosa


----------



## audionut

Quote:


  Originally Posted by *jcx* /img/forum/go_quote.gif 
_Some wrong and misleading info being tossed around this thread re gain and balanced/single ended here

 The amp is a true differential amp, there is a single gain # applied to Vin difference – it doesn’t matter whether the input is SE or dual polarity/balanced with respect to gnd

 With 500:1 feedback resistor ratio the differential gain would be 1001 (assuming high enough loop gain - which the circuit doesn't have)

 There is also a small common mode gain of ~1x

 With “balanced” input the a,b stator drive signals would be +,-500.5x 

 With SE signal, - input gnded, stator a would see +501x, b –500x

 The trivial gain imbalance w/SE drive is much smaller than component tolerances – you’d need better than 0.1% tolerance feedback R and > 1e6 open loop gain for these errors to become the same order of magnitude – you could buy or match the feedback resistors but you need more active devices to get the open loop gain

 Just to spell it out in small words - - this amp doesn’t need/won’t benefit from balanced vs SE input signal -- worrying about balanced input is completely myopic audiophilia nervosa_

 

I would agree with everything jcx has pointed out here, I just wasn't able to say it in technical terms in my post on previous page, #629. I personally can't back up jcx's tech explanation, as I'm not an electronics engineer. I just happen to think that jcx's end quote "worrying about balanced input is completely myopic audiophilia nervosa[/QUOTE] is what I was trying to get across. I just don't think (and I may be wrong) that worrying about balanced vs se input with this amp, will be something that my old ears could hear a difference in. I'm most concerned with SOUND QUALITY, and again, don't think I'd be able to hear a significant difference going balanced (again, I could be wrong). Won't know for sure unless I get to hear a balanced setup. For now, mine will be se input, and have no plans to ever go balanced. To each his own.... I'm sure this thing will sound good either way.


----------



## runeight

Well, gentlemen, let us leave this as it stands. I have long given up on understanding what audiophiles hear or don't hear.

 I got my box of parts today except for the PS trimpots which will come tomorrow. No sign of boards yet.


----------



## FrankCooter

No Head-Fi thread would be complete without the whole "balanced thing" rearing it's ugly head! Alex, I hope you've succeeded in burying this once and for all, but I wouldn't count on it.


----------



## runeight

It's appearance in this thread is entirely my fault.

 It is a small issue compared to getting the next 20 or so amps up and working.


----------



## Currawong

I agree that keeping the momentum on the project is most important but will say that, at least for _me_, balanced input is important as my DAC performs best using its balanced outputs. How that will translate when I get a chance to build this I'd be interested to know, but it's not urgent.


----------



## ericj

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_





 It's appearance in this thread is entirely my fault.

 It is a small issue compared to getting the next 20 or so amps up and working. 
	

	
	
		
		

		
		
	


	


_

 

Well, as of tonight i have two fully functional prototypes. Still going to increase the follower current on the SS version, though, since i have those resistors already. I'll dream about off-board CCS at a later date. 

 The SS amp is even partially cased. 

 Boss gave me today off. Which would sound pretty neat if it weren't because i have to put in 8 hours on saturday.


----------



## Keithpgdrb

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_Well, as of tonight i have two fully functional prototypes. Still going to increase the follower current on the SS version, though, since i have those resistors already. I'll dream about off-board CCS at a later date. 

 The SS amp is even partially cased. 

 Boss gave me today off. Which would sound pretty neat if it weren't because i have to put in 8 hours on saturday._

 

Excellent News!! about the amp, not so much the saturday.


----------



## runeight

Fab says board ship will be Friday. They are on a two-day shipping schedule so I won't have them until Monday or Tue.

 But, I'll have all of the parts by then and the pack of quads from wiatrob.


----------



## TimJo

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Fab says board ship will be Friday. They are on a two-day shipping schedule so I won't have them until Monday or Tue.

 But, I'll have all of the parts by then and the pack of quads from wiatrob._

 

That's great news.

 So, a few days ago I mentioned that there is a distributor in LA that has the out of stock WIMA's. I spoke with them, and they'll sell directly to us, and even gave a nice price break for a group buy.

 I talked to Alex about this, and he's willing to include one with each board, if I have them shipped to him.

 Because they are a distributor for WIMA, I could also look into having them supply all of the WIMA caps for the amp, since they are willing to sell them to us for less than Mouser. If we went this route, I'd have them shipped to me, and then I'd bag up sets, and ship the bags to Alex to include with the boards. (I haven't verified stock for the other caps yet, but my guess is they'll have them.)

 So, here's the deal, is anyone/everyone interested in this?

 I'm not sure how many of you have already ordered parts, or where everyone is at.

 So, can you all let me and Alex know one of the following:


> 1.) not interested, happy with using the Mallory alternative cap
> 2.) interested in the Mouser out of stock cap only
> 3.) interested in getting a set of all the WIMA film caps required for the build


If we are going to do this, I'm gonna say it either has to be #2 _*or*_ #3, as opposed to some folks wanting #2 and some #3. That will reduce the effects of buying in bulk, and it will be more spreadsheet madness for Alex to have to coordinate in order to get everyone their boards.

 Let me know...


----------



## scompton

I'd prefer 3, but 2 is fine with me as well.


----------



## MrMajestic2

3 would be great, but 2 is fine as well.


----------



## audionut

Are we talking about C3,4,5,6, and 7 in PS? If so, I got all mine last week from Mouser. I just checked their stock on these, and all show in stock. Am I missing something here, or has Mouser just gotten some previously out of stock caps back in? Just trying to make sure I'm not missing something that I need that's on the current BOM excel. Thanks.


----------



## TimJo

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Are we talking about C3,4,5,6, and 7 in PS? If so, I got all mine last week from Mouser. I just checked their stock on these, and all show in stock. Am I missing something here, or has Mouser just gotten some previously out of stock caps back in? Just trying to make sure I'm not missing something that I need that's on the current BOM excel. Thanks._

 

Well, last week Alex said they were out of C6.

MKP10-.1/1KV/10P22 WIMA Polypropylene Capacitors

 Looks to me they still are outta stock.


----------



## TimJo

Okay, I spoke with the distributor and they have the others in stock, with one small substitution - they are out of the 10% version of C3, C4, so I subbed the 5% version instead. 
	

	
	
		
		

		
		
	


	




 The quote for 30 sets of C3 through C7 (5 pcs.) with shipping would be about $4.50 per set - less than the cost of one of the big 10% caps alone, but here your getting a better part.

 This seems like a really good deal, and I'm willing to do the legwork if you guys want in...


----------



## Pars

I've bought from TAW Electronics a few times, and yes they do sell to individuals. IIRC, their pricing was better than Mousers on WIMA, and their stock is of course larger and more diverse. In the past I've dealt with a Laura (S??), but can't find my emails right now.


----------



## audionut

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Well, last week Alex said they were out of C6.

MKP10-.1/1KV/10P22 WIMA Polypropylene Capacitors

 Looks to me they still are outta stock._

 


 Yes, the confusion for me has been cleared up. My bad. I ordered all my parts last week, they had C6 in stock and sent the one I ordered. I just now dug through the huge bag of parts and found it to confirm. Today, when I checked on Mouser's site and punched in the C6 #, I didn't look close enough at the 1st part that popped up, which ended in /10P27, and shows 270 in stock. The second one down, the actual # on BOM ending in /10, is on order. Again, my bad. I did, however, call the Mouser tech to see what the difference between the 2 are, and he said the only difference is physical size, with the /10P27 (in stock), being slightly smaller at 8.38MM vs the specified part # ending in /10 being 8.5MM. The tech seemed to think that the difference in size wouldn't matter much as far as fitting the board. Everyone can use their own judgement as to whether this part will work for them in place of the specified one. The Mouser part # for possible C6 sub is 505-M10.1/1000/10P27


----------



## Coreyk78

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Okay, I spoke with the distributor and they have the others in stock, with one small substitution - they are out of the 10% version of C3, C4, so I subbed the 5% version instead. 
	

	
	
		
		

		
			





 The quote for 30 sets of C3 through C7 (5 pcs.) with shipping would be about $4.50 per set - less than the cost of one of the big 10% caps alone, but here your getting a better part.

 This seems like a really good deal, and I'm willing to do the legwork if you guys want in..._

 

I already placed my Mouser order with the mallory cap, but that is a really good deal. At that price I'm in for a set, I can always use the extras for something else 
	

	
	
		
		

		
		
	


	




 Otherwise if we end up just getting the one out of stock cap I'll take one.

 edit- I went ahead and placed an order with digikey for the 2 trimpots also, I needed some other parts from there anyway.


----------



## n_maher

I'd be in for the Wima cap order, either option #2 or #3. Just tell me who to pay and how much.


----------



## TimJo

It looks like this would work for the Bourns trimmer that is outta stock right now at Mouser. (Power Supply - P1, P2)

T93YA200KT20 Vishay/Sfernice Trimmer Resistors - Multi Turn

 It's rated at 1/2 watt with the same footprint. 19 turns instead of 25, but I guess that won't matter much to trim in the rails.

 Feel free to double check the specs to be sure I didn't miss something.


----------



## sachu

I'd be in for two sets of the wima cap order ..option 2 or 3 will work..


----------



## Emooze

Interested in a single set of the wima caps as well. I'd prefer option 3 but 2 will work as well.


----------



## TimJo

So by my count, that's 9 sets so far, with everyone preferring a full set. At this price, it doesn't make sense not to get all of them, unless you've already got your parts, like runeight and audionut - although I guess that didn't dissuade Coreyk78. 
	

	
	
		
		

		
		
	


	




 We need at least 25 sets to get the price that was quoted. 

 The main thing I want to avoid is delaying shipment of the boards, since the caps will be sent up to Seattle, split into sets, and then sent back down to Alex.


----------



## studeb

i'll go option 3

 so then we would be getting boards, jfets and the Wima caps in one lot.
 the rest comes from mouser, except the tube trafo


----------



## TimJo

Okay, so now it looks like Mouser is out of the 68K1 resistor on the amp (R30).

 I can't find any subs at Mouser, so I'm thinking about replacing R29 and R30 with two of these - CPF262K000FKEE6 Vishay/Dale Metal Film Resistors

 The schematic shows the 56k2 and the 68k1 in series, for a total of 124k3 ohms.

 Subbing the two 62k in their place yields 124k ohms, and keeps the voltage drops balanced, so the 2 watt rating should be sufficient.

 Alex?


----------



## TimJo

One other question. What size fuse are you prototyper's using on your amps?

 It looks like the fuse drawer is included on this power entry module, right?


----------



## runeight

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Okay, so now it looks like Mouser is out of the 68K1 resistor on the amp (R30).

 I can't find any subs at Mouser, so I'm thinking about replacing R29 and R30 with two of these - CPF262K000FKEE6 Vishay/Dale Metal Film Resistors

 The schematic shows the 56k2 and the 68k1 in series, for a total of 124k3 ohms.

 Subbing the two 62k in their place yields 124k ohms, and keeps the voltage drops balanced, so the 2 watt rating should be sufficient.

 Alex?_

 

Good.


----------



## HeadphoneAddict

wiatrob says he has most of the parts for my tube version already, so I have to defer to him about what parts we need.


----------



## ericj

We were prototyping with 1A fuses but i've been meaning to ask what the desired value for daily use should be.


----------



## runeight

The tube amp with heaters draws a bit less than 50W. On the line side this would be about 400mA. I would think that 1A would be good here.

 The sand amp draws about 35W (IIRC), or about 300mA from the line. 3/4A I would think should work.

 SB fuses should handle the initial pulses to the filter caps, but I haven't actually tried to calculate this out.


----------



## sergery

I am in for #3, I won't turn down #2 though. In other news I had to search far and wide for stax adapters!!!! 
	

	
	
		
		

		
			







 thanks Frank!


----------



## Emooze

Agreed, Frank really helped us out there. I'll buy you a beer next time you're in the Mass area, hahaha


----------



## smeggy

ok, I'm in for 3 or 2 or whatever


----------



## TimJo

That's true, I got my bag of Stax jacks as well Frank! Thanks...


----------



## sachu

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_That's true, I got my bag of Stax jacks as well Frank! Thanks... 
	

	
	
		
		

		
		
	


	


_

 

X2..many thanks Frank. Most generous of you.


----------



## TimJo

Okay, here's where we stand this morning. 

 So far I have 15 sets on the list - ten more and we hit the 25 part price break. Take a look at the list, and if your not on it, but want to be, reply to this or send me a PM.

 If we hit 25 sets (or more) by 1pm pst, then they will ship today, which means I'll probably see them Monday. I can bag them up and get them down to Alex by mid week.


----------



## scompton

2 sets for me


----------



## TimJo

While we are waiting for others to chime in, could one of you take a look at the p/n's just to be sure I wasn't looking cross-eyed when I wrote this all down. 

 Here's TAW's website - TAW Electronics

 C3, C4 (lead spacing 27.5)

 Mouser p/n ~ 505-M101/400/10 
 WIMA p/n ~ MKP10-1/400/10
 TAW p/n ~ MKP 105K400 (out of stock)
 TAW p/n ~ MKP 105J400 (this is the 5% version of the same cap)

 C5, C6 (lead spacing 15)

 Mouser p/n ~ 505-MKS4.1/630/10
 WIMA p/n ~ MKS4-.1/630/10
 TAW p/n ~ MKS4 104K630-6

 C7 (lead spacing 22)

 Mouser p/n ~ 505-M10.1/1000/10
 WIMA p/n ~ MKP10-.1/1KV/10P22
 TAW p/n ~ MKP 104K1KV-7


----------



## ericj

Speaking of frank's jacks, someone commented that they had some that were lacking the center socket conductor, so they don't work so well for normal bias. 

 I pulled the conductors out of the center hole in two of mine that i'm converting to 5-pin (going to back-fill the hole with silicone or epoxy) so if anyone is in dire need of a pin socket, I can send a couple out.

 Edit: aaand they're spoken for already. But if anyone else wants to do this, basically you just need a pair of needle-nose pliers to squish the little tabs that are bent up to secure the thing and then just push the solder tab back through the plastic. I took mine out because i figured it would make it easier to fill the hole. Giving them to someone who needs them is a bonus.


----------



## bada bing

I'd sign up for a couple sets of caps if available.


----------



## TimJo

Okay, here's an updated list. 

 We are so close to 25 sets, I'm thinking about placing the order this afternoon, figuring that the last two will go somewhere. (boilermakerfan are you out there? 
	

	
	
		
		

		
		
	


	




)


----------



## n_maher

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Okay, here's an updated list. 

 We are so close to 25 sets, I'm thinking about placing the order this afternoon, figuring that the last two will go somewhere. (boilermakerfan are you out there? 
	

	
	
		
		

		
		
	


	




)_

 

[edit]Ooops, you already had me down for 2.


----------



## TimJo

Okay, I just ordered 25 sets so that they'd ship tonight.

 There are still two sets up for grabs... 
	

	
	
		
		

		
		
	


	




 Okay now only one left...


----------



## Emooze

Awesome, I think it will be very easy to find a buyer for that set.

 All this collaboration makes me feel kind of lazy but I don't now how I can contribute. Either way, keep up the great work.


----------



## pabbi1

OK, tubers - I have mailed out everything that has been paid, and Team Aussie will get theirs from Alex, so...

 I have one construction matched triplet, 3 construction matched pairs, then about 18 singles left. That will be all I have for sale, after keeping my own spares.

 That all said, there is no matching requirement, only that the tubes test good. All I ship will measure 100% on my EMC meter.


----------



## runeight

So I am sending four tubes to Oz. Is that right?


----------



## pabbi1

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_So I am sending four tubes to Oz. Is that right?_

 

Errr, 8 so far... 
	

	
	
		
		

		
			





 I'll send them out in the morning, so you'll have them Monday... IFF that is ok with you.


----------



## runeight

No need. I have the four you've already sent me. I'll send those. 
	

	
	
		
		

		
		
	


	




 Man, these guys from Australia. If I ever get to visit there I'm expecting a place to stay and three meals a day.


----------



## pabbi1

Well... minivan wanted 8... hope he is reading along. BUT, it would be a great time for the Ozzies to speak up if they want others.


----------



## runeight

Ah ok. I didn't read carefully enough. I'll send as many as the want and that you wish to provide.

 No shipping notice from the fab today. I was expecting the boards to go out. But now I don't know when they'll be here.


----------



## BoilermakerFan

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Okay, here's an updated list. 

 We are so close to 25 sets, I'm thinking about placing the order this afternoon, figuring that the last two will go somewhere. (boilermakerfan are you out there? 
	

	
	
		
		

		
		
	


	




)_

 

YES! I'm out there and I'm in for the two sets! I was out in Vegas for the SEMA show. Long, long days and $15/day for internet that never managed to work, so long story short, I was in the dark for 5 days...

 EDIT: Damn, saw there was only one set left. That's ok, they'll go in the hybrid and I'll sub the others in the SS. I'll also be order splits between Mouser and Digi-Key, so it's no problem.

 And my TV camera chassis showed up. Have to figure out how to open it so I can see if Hammond 369JX trafos will fit, otherwise I may be ordering the R80-32 Spritzer pointed out... I like the size of those R-cores.


----------



## BoilermakerFan

Luvdunhill

 Have you received the tooling for your STAX jacks?


----------



## nattonrice

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Man, these guys from Australia. If I ever get to visit there I'm expecting a place to stay and three meals a day. 
	

	
	
		
		

		
		
	


	





_

 

For sure


----------



## TimJo

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Damn, saw there was only one set left. That's ok, they'll go in the hybrid_

 

Sorry about that. The last set is yours though. It's not like they can't be had, it's just we were able to get all of them at once, and TAW gave us a really great price. I worked with Margie, and she was very helpful and happy to help out.

 Okay, here is the final list.


----------



## BoilermakerFan

Thanks TimJo.



 I emailed diyGene on eBay about combined shipping on the 100W R-core tranfos Spritzer pointed out. I actually asked for combined shipping on (2) 50W and (4) 100W, but (5) 100W should be nearly the same... Combined shipping was US$116, so about $30 savings, but then I'd have to ship to others so it's a wash or worse if you just need one. 

 I found a couple other US-based companies listing R-Cores, so I'll call them on Monday. Looking at the properties of R-Cores, it looks like they'll be just the ticket for my very tight build to ensure I minimize noise. 

 Their oblong shape also works very well for a couple other projects where I have a little PSU section in my NABU chassis.


----------



## les_garten

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Thanks TimJo.



 I emailed diyGene on eBay about combined shipping on the 100W R-core tranfos Spritzer pointed out. I actually asked for combined shipping on (2) 50W and (4) 100W, but (5) 100W should be nearly the same... Combined shipping was US$116, so about $30 savings, but then I'd have to ship to others so it's a wash or worse if you just need one. 

 I found a couple other US-based companies listing R-Cores, so I'll call them on Monday. Looking at the properties of R-Cores, it looks like they'll be just the ticket for my very tight build to ensure I minimize noise. 

 Their oblong shape also works very well for a couple other projects where I have a little PSU section in my NABU chassis._

 

I think you have a Typo in the ID, I can't find diyGene on ebay. Do you have a link?


----------



## dBel84

DiyGene ..dB


----------



## les_garten

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_DiyGene ..dB_

 

Thanx! DIY-Goods apparantly.


----------



## BoilermakerFan

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_Thanx! DIY-Goods apparantly._

 

Yes, DIY-Goods is their eBay username, but the store is DIY Gene:

eBay Store - DIY Gene: Accessories Parts, GAD-Viva Silver Gold Teflon, GAD-Viva MKP Capacitor


----------



## TimJo

Alex, would it be possible to post the dimensions of the hole pattern on the ps board and the double amp board, in it's 'unbroken' state? I'll be using the hole towards the center of the amp between the tube sockets is an additional standoff location to prevent flexing, so can you include those dimensions as well?

 I am beginning to layout the casework, so I can test it in place, rather than loose on the workbench. I'll feel better working with high voltages when the boards are attached to standoffs on a grounded case. 
	

	
	
		
		

		
		
	


	




 Thanks.


----------



## les_garten

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Yes, DIY-Goods is their eBay username, but the store is DIY Gene:

eBay Store - DIY Gene: Accessories Parts, GAD-Viva Silver Gold Teflon, GAD-Viva MKP Capacitor_

 

He has some interesting stuff there including those R-Core transformers. He says he'll do custom transfos also. My Phoenix has 3 R-Cores in it


----------



## TimJo

Bad news... 
	

	
	
		
		

		
		
	


	




 It looks like Mouser ran out of Q7 & Q8 on the PS board - replacements not here till March.

MJE350STU Fairchild Semiconductor Bipolar Transistors

 Looks like DigiKey has 'em.

TRANSISTOR PNP 300V 500MA TO-126 - MJE350STU

 Should we do a group buy???


----------



## BoilermakerFan

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Bad news... 
	

	
	
		
		

		
		
	


	




 It looks like Mouser ran out of Q7 & Q8 on the PS board - replacements not here till March.

MJE350STU Fairchild Semiconductor Bipolar Transistors_

 

They do not have 200VA or 300VA trafos though. 
	

	
	
		
		

		
		
	


	




 Digi-Key has the MJE350s in stock.


----------



## TimJo

TRANSISTOR PNP 300V 500MA TO-126 - MJE350STU

 I suppose I could order fifty of them from Digi-Key to save on shipping, and include a pair with each bag of caps.

 Do you guys like this idea?


----------



## scompton

Sounds good to me


----------



## ericj

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_TRANSISTOR PNP 300V 500MA TO-126 - MJE350STU

 I suppose I could order fifty of them from Digi-Key to save on shipping, and include a pair with each bag of caps.

 Do you guys like this idea?_

 

Relax. They only ran out of the Fairchild version. 

 The OnSemi version works just as well and cost a penny less: 

http://www.mouser.com/ProductDetail/...6Z%2fP96C2I%3d

 Alex really did do a pretty good job of selecting parts that are easy to acquire. There can be no guarantees because there's constant flux in what's getting manufactured and what's getting replaced, but almost all of the parts on these boards are common commodities available from multiple manufacturers.


----------



## TimJo

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_Relax. They only ran out of the Fairchild version. 

 The OnSemi version works just as well and cost a penny less: 

MJE350G ON Semiconductor Bipolar Transistors

 Alex really did do a pretty good job of selecting parts that are easy to acquire. There can be no guarantees because there's constant flux in what's getting manufactured and what's getting replaced, but almost all of the parts on these boards are common commodities available from multiple manufacturers._

 

Thanks Eric.


----------



## runeight

Yes, go to the website and grab the PDF versions of the silkscreens and you'll have what you need.


----------



## ericj

I should clarify, i haven't used the OnSemi MJE350, but the MJE series is manufactured by several companies and the specs for the OnSemi part are the same as the specs for the Fairchild part. The letters after "MJE350" are just a manufacturer-specific suffix specifying packaging options or something. 

 The NatSemi MJE350 is only 30 cents but has a much lower power dissipation spec for some reason. 

 We've had similar sourcing problems with the MPSA42 but, like the MJE series, the MPSA series is a common commodity and parts from various vendors have been proven in prototyping.


----------



## runeight

There should be good alternative manufacturers for all of the BJTs. 

 TimJo, there are 1:1 scale PDFs of the silkscreen which have the mounting hole positions on the website. Are these ok or do you need dimensions?

 I got an email late last night that the boards shipped. Delivery date is Tue. I got wiatrob's J271's in the mail today. Hopefully TimJo's caps will get here later next week. By then I should have the amp tested and verfied. That means I can probably ship a week from this Monday. Or, if we're lucky, this coming Friday.


----------



## TimJo

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_There should be good alternative manufacturers for all of the BJTs._

 

If using the OnSemi MJE350 for example, then is it best to order their MJE340 as well, or are these so generic that you can mix manufactures?

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_TimJo, there are 1:1 scale PDFs of the silkscreen which have the mounting hole positions on the website. Are these ok or do you need dimensions?_

 

These should work. I'll just measure off the prints. I'm having the bottom half of the case made at a fab shop across from work, so I need to make a drawing for the shop.


----------



## runeight

Oh. The holes are 5mm from the edges and 5mm from the center line.

 The PS transistors don't have to be matched and even different manuf should be close enough.


----------



## TimJo

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_
 OK, tubers - I have mailed out everything that has been paid..._

 

Thanks Al. My box arrived yesterday. 

 That gives me a set of GE's with grey plates and a set of RCA's with black plates (rebranded as Heintz and Kaufman GAMMATRON).


----------



## TimJo

One more question about the heater wiring. I know on the website for the Bijou it says that you shouldn't have the heater wiring under the boards. Does this apply to this amp as well?

 I was thinking about using this style Phoenix connector for the heaters and mounting them on the underside of the amp board. 

 The twisted pairs wouldn't really be routed under the boards per se, it would be more that the connection would be attached from underneath.

 Good idea - bad idea?


----------



## runeight

I wish I could get you guys to read the website. 

 Run the heater wiring from the back edge (output side) of the board. Run along the outside edges and right down the middle from the back. 

 Don't run from the front edge of the board where all of the input circuitry is.

 This is the way to do it whether you run topside or bottomside.


----------



## TimJo

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_
 ...whether you run topside or bottomside._

 

Thanks. That was the part that I wasn't sure about... 
	

	
	
		
		

		
			





 It was from reading the Bijou wiring directions on the website that made me ask this. Maybe I read too much...


----------



## runeight

So I have a big box of parts, solder flux remover, 50 million j271 quads and ... all dressed up with no place to go.

 Latest list attached including TimJo's cap list. This is how I will send things out unless you guys tell me otherwise.


----------



## luvdunhill

Just curious, what voltage are you guys using to measure the Idss of the JFETs?


----------



## audionut

12V is what I used. Alex, when should we send you our shipping address for boards? Thanks.


----------



## runeight

Yes, 12V.

 Let's wait until I verify the builds. Then you guys can send me the info.


----------



## luvdunhill

Wow, these much vary a lot across batches then if you guys are getting that many over 10mA Idss. I had about 20 out of 100 over 10mA. My batch wasn't from Mouser and I was using 12V bench PSU as well.


----------



## audionut

Yes, Out of the 20 from Mouser, I only got 1 decent quad. Readings were all over the board. Almost thought I wasn't going to get a good quad.


----------



## TimJo

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I got an email late last night that the boards shipped. Delivery date is Tue. I got wiatrob's J271's in the mail today. Hopefully TimJo's caps will get here later next week. By then I should have the amp tested and verfied. That means I can probably ship a week from this Monday. Or, if we're lucky, this coming Friday._

 

I spoke with TAW this morning, and UPS is scheduled to deliver Wednesday. I'll get them bagged up after work, and to the post office Thursday morning. 

 The invoice ended up being $112.49 - which works out to $4.50 per set (a third of the cost of Mouser 
	

	
	
		
		

		
		
	


	




).


----------



## sachu

hey Tim,

 Could you please outline what caps are included in the group buy? Things get buried after a while..


----------



## TimJo

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_hey Tim,

 Could you please outline what caps are included in the group buy? Things get buried after a while.. 
	

	
	
		
		

		
		
	


	


_

 

Sure. They are the WIMA film caps for the power supply, C3 thru C7, five pcs. total.

 They are the same parts as in the bom with the one exception that C3 & C4 are the 5% tolerance version, because they were out of the 10% version stocked by Mouser.

 The details are in this post: http://www.head-fi.org/forums/6136124-post668.html


----------



## pabbi1

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Wow, these much vary a lot across batches then if you guys are getting that many over 10mA Idss. I had about 20 out of 100 over 10mA. My batch wasn't from Mouser and I was using 12V bench PSU as well._

 

I was using 9v, which seemed to work fine, but 18v definitely did not. Guess I got really lucky getting 60% over 10 Idss, though only 4 were (just barely) within a 10% match.


----------



## luvdunhill

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_I was using 9v, which seemed to work fine, but 18v definitely did not. Guess I got really lucky getting 60% over 10 Idss, though only 4 were (just barely) within a 10% match._

 

My guess is luck wasn't really involved... just the fact that you used a different matching voltage than the others "helped" a bit


----------



## ericj

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_My guess is luck wasn't really involved... just the fact that you used a different matching voltage than the others "helped" a bit 
	

	
	
		
		

		
		
	


	


_

 

I used a fresh 9v alkaline as well, which is giving about 9.5 volts. I used quads in the range of 13ma in my amps.


----------



## sergery

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_





 So I have a big box of parts, solder flux remover, 50 million j271 quads and ... all dressed up with no place to go.

 Latest list attached including TimJo's cap list. This is how I will send things out unless you guys tell me otherwise._

 

I have tubes on hand courtesy of pabbi1. Thanks!


----------



## runeight

The PS (battery voltage) shouldn't matter to the Idss above about 8V. The output curves are typical for fets which means that they get very flat after turning on. There should only be about 1mA change from 8V to 20V if the curves are accurate for real devices.


----------



## n_maher

Just to make sure I'm staying current, no one has requested payments for anything yet, right?


----------



## runeight

Right. All the parts are coming to me. I'll add their costs into your total and then I'll reimburse wiatrob and TimJo.

 One stop shopping for you guys.


----------



## BoilermakerFan

I've already PM'ed luvdunhill; however, is there anyone else interested in his amazing STAX jacks for these amps? I know others have already sourced theirs, but I wanted to post up in public in case there is a lurker wanting a set.


----------



## n_maher

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Right. All the parts are coming to me. I'll add their costs into your total and then I'll reimburse wiatrob and TimJo.

 One stop shopping for you guys. 
	

	
	
		
		

		
		
	


	


_

 

Thanks for that, just wanted to make sure no one was waiting on me.


----------



## Beefy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I've already PM'ed luvdunhill; however, is there anyone else interested in his amazing STAX jacks for these amps? I know others have already sourced theirs, but I wanted to post up in public in case there is a lurker wanting a set._

 

I would imagine many planning to build this amp would want good jacks - me included. It is probably up to luvdunhill to offer them first though......


----------



## runeight

Well gents, in between clients I cruised by home and there were boxes. 

 Now I know that many people have done black boards, but I gotta tell ya, these are bad looking boards.

 Pix later...


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Well gents, in between clients I cruised by home and there were boxes. 

 Now I know that many people have done black boards, but I gotta tell ya, these are bad looking boards.

 Pix later..._

 

Sweet! I just printed off the scale PDFs at lunch and did the poor man's laminating to them (clear packing tape) so they are a little more durable for chassis layout. Using my big 4" cubed Electro-Print transformers as the space holders for the Hammonds so I know I'll plenty of room.


----------



## bada bing

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I've already PM'ed luvdunhill; however, is there anyone else interested in his amazing STAX jacks for these amps? I know others have already sourced theirs, but I wanted to post up in public in case there is a lurker wanting a set._

 

I'm searching for a couple higher grade jacks - one for the eXsaTa and one for a KGSS build. 

 PM sent.


----------



## luvdunhill

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I've already PM'ed luvdunhill; however, is there anyone else interested in his amazing STAX jacks for these amps? I know others have already sourced theirs, but I wanted to post up in public in case there is a lurker wanting a set._

 

I'm getting there. Have a few things to finish up first. The jacks are made from solid teflon, so they really aren't going to be "cheap". I didn't buy the materials in large quantites, and there was a good amount of trial and error that went on that I'd try and recover. you know, standard prototyping stuff.

 I'll try and at least post some dimensions for you guys..


----------



## BoilermakerFan

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_I'm getting there. Have a few things to finish up first. The jacks are made from solid teflon, so they really aren't going to be "cheap". I didn't buy the materials in large quantites, and there was a good amount of trial and error that went on that I'd try and recover. you know, standard prototyping stuff.

 I'll try and at least post some dimensions for you guys.._

 

Thanks.

 "Cheap" is a relative word, so if you can PM me an estimate I'd appreciate it. I'd say we already have a commitment for (6) but we might be able to round up more.


----------



## runeight

Not a great pic, but you get the basic idea.


----------



## Lou Erickson

Wow, those look really good! Those are ordinary 8-1/2" by 11" inch sheets they're on? They're smaller than I thought! Very impressive!


----------



## runeight

Yes, ordinary letter size paper.


----------



## pabbi1

When you said bad, I think you meant bad-ass?


----------



## sergery

Those are some fine looking boards


----------



## runeight

Yes, that's what I meant. And they even look better with components on them. 
	

	
	
		
		

		
			





 I can now say with high confidence that if you put all the right parts in the right orientation on the PS and if you have good solder joints and no solder bridges the PS will come up first time.

 I just finished powering the new one up. The trimpots dialed perfectly I have -306 and +304V on the rails. I dialed the biases to 280V and 600V with no problems.

 I won't get to the amp tonight. I will try to tomorrow night, but the amp is a more difficult build than the PS.


----------



## runeight

And, on top of this, the 269JX provides plenty of voltage. The filter caps are at a little over 350V. This is much more than is needed and there is no risk of low voltage. OTOH the mosfet heatsinks are dissipating 2W that is being burnt here. We'll have to monitor this as I expected the JX to run closer to 330V.


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_And, on top of this, the 269JX provides plenty of voltage. The filter caps are at a little over 350V. This is much more than is needed and there is no risk of low voltage. OTOH the mosfet heatsinks are dissipating 2W that is being burnt here. We'll have to monitor this as I expected the JX to run closer to 330V._

 

Can the whole thing run a bit higher than 300V to balance out the heat dissipation a bit?

 [EDIT] Just thinking that running 300V of zeners for 310V instead of 291V for 300V would balance it out easily enough.


----------



## runeight

Picture. Board is powered up, LEDs are lit, load resistors are melting the probe tips.






 Oh, the crud on the board is my fault, but I used it anyway.


----------



## runeight

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Can the whole thing run a bit higher than 300V to balance out the heat dissipation a bit?

 [EDIT] Just thinking that running 300V of zeners instead of 291V would balance it out easily enough._

 

Yes, with the 269JX you could run higher rails. The amps won't mind an extra 15V or so.


----------



## Beefy

Cool beans


----------



## runeight

However, I am now a bit puzzled by some of the other builds.

 I hooked up my 270AX and it is having no problem at all with this load. In fact, it is generating 335V at the filter caps. A much lighter load on the fets.

 I wonder how much the filament draw might be loading this transformer because right now we don't need the bigger one.


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I wonder how much the filament draw might be loading this transformer because right now we don't need the bigger one. 
	

	
	
		
		

		
		
	


	


_

 

Would you like to know? I have both side by side on my hybrid...


----------



## runeight

Yes.


----------



## runeight

Gents, I made it about halfway through the amp board tonight but I need to stop now so I don't make any mistakes (assuming that I haven't made any so far).

 These are really nice looking boards.


----------



## awpagan

nice boards runeight.

 If there's too much voltage for the power supply, you could always drop a few volts through a CRC?


http://www.kbapps.com/audio/tubemanual/images/158.gif


----------



## runeight

No, there is no place to easily insert a CRC into the PS. I'm glad I'm having a chance to test this out first, but I don't have the parts to build up the tube version to test the 270AX when loaded with both HV and heaters. Looking at what I get with just the HV, however, it seems like it will work alright with heaters attached.

 Since some of the proto builders saw their filter voltages drop significantly when they added additional load to the rails. My only conclusion at this point can be that they had very low line voltages. I tend to have extremely solid 120V here, sometimes even higher. Never lower. This really helps all of my transformers. But others often have much crappier power.

 Perhaps wiatrob can verify his results for us.

 OTOH, I'm guessing than most of you have bought the JX already or some toroidal equivalent. I can say that your toroids really can't produce more than 250VAC on the secondaries when loaded because this will cause way too much voltage drop in the fets.


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_No, there is no place to easily insert a CRC into the PS. I'm glad I'm having a chance to test this out first, but I don't have the parts to build up the tube version to test the 270AX when loaded with both HV and heaters. Looking at what I get with just the HV, however, it seems like it will work alright with heaters attached.

 Since some of the proto builders saw their filter voltages drop significantly when they added additional load to the rails. My only conclusion at this point can be that they had very low line voltages. I tend to have extremely solid 120V here, sometimes even higher. Never lower. This really helps all of my transformers. But others often have much crappier power.

 Perhaps wiatrob can verify his results for us.

 OTOH, I'm guessing than most of you have bought the JX already or some toroidal equivalent. I can say that your toroids really can't produce more than 250VAC on the secondaries when loaded because this will cause way too much voltage drop in the fets._

 

I haven't ordered any parts yet, except for the group buy stuff... I was planning to use the 369JX or the R-Core from eBay. But after seeing those boards, I'm glad I waited. They deserve the red resistors! My heatsinks are the gold 2-1/2" tall variant too, so it should look nice.

 I'm going to be a slow build. I'm only planning to build it once and I plan to stuff it in that TV camera or old HAM radio chassis. She'll be at CanJam 2010 along with 2 or 3 other custom amps and hopefully 5 sets of custom headphones including a pair of HE60s.


----------



## TimJo

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes, with the 269JX you could run higher rails. The amps won't mind an extra 15V or so._

 

Well, I already have the 369JX arriving from Angela today, so it seems like this may be a good option. I'll add some more 100v zeners to my parts list.

 I took a quick look at the Mouser catalog, and it looks like your already listing the largest size heatsink. I don't see a 2 1/2" tall version with the 1 x 1.65 footprint.

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_
 Since some of the proto builders saw their filter voltages drop significantly when they added additional load to the rails. My only conclusion at this point can be that they had very low line voltages. I tend to have extremely solid 120V here, sometimes even higher. Never lower. This really helps all of my transformers. But others often have much crappier power.
_

 

I just checked an outlet at my new place here in Seattle, and it is a steady 123 volts, so it'll be interesting to see what the 369JX does. I also have the 370DAX for the Bijou, so I can get you another set of data points, once I'm up and running.


----------



## Beefy

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_I took a quick look at the Mouser catalog, and it looks like your already listing the largest size heatsink. I don't see a 2 1/2" tall version with the 1 x 1.65 footprint._

 

You can get 2.5" Aavid sinks for the power MOSFETs that are experiencing the higher heat dissipation: 531302B02500G Aavid Thermalloy Heatsinks

 But according to the specs, their thermal resistance of 8C/W is actually higher than the 2" version listed just above them in the catalogue, which doesn't make much sense to me 
	

	
	
		
		

		
		
	


	




 For 2.5" sinks at other locations, Digikey might be an option: Digi-Key - HS380-ND (Manufacturer - 530002B02500G)


----------



## BoilermakerFan

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_
 I took a quick look at the Mouser catalog, and it looks like your already listing the largest size heatsink. I don't see a 2 1/2" tall version with the 1 x 1.65 footprint._

 

 Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_You can get 2.5" Aavid sinks for the power MOSFETs that are experiencing the higher heat dissipation: 531302B02500G Aavid Thermalloy Heatsinks

 But according to the specs, their thermal resistance of 8C/W is actually higher than the 2" version listed just above them in the catalogue, which doesn't make much sense to me 
	

	
	
		
		

		
			





 For 2.5" sinks at other locations, Digikey might be an option: Digi-Key - HS380-ND (Manufacturer - 530002B02500G)_

 

I have the 2-1/2" gold non-ROHS compliant versions of the Mouser part and I have the Digi-Key ones Beefy linked. Both are 2-1/2" and both fit. However, I plan to screw mine to the PCB, not solder mount... Just too much mass up high for me to trust a solder joint. Going with black 1" long 4-40s aluminum cap head screws (have to match the thermal expansion) and thread lock.

 I can probably dig up the part number for the gold ones at Mouser too. I have more money in bloody heatsinks for DB trials than I do for everything else on a Mosfet-MAX build. I have ten or twelve quads of the gold heat sinks after an accidental double order.


----------



## les_garten

I was looking for an Ultra quiet power environment and was wondering about this combo:

 R-Core 250-0-250

 and this: PSU for the heaters.

 Anybody see any problems with this combo? I know the PS is overkill, I originally started looking into this as a way to power the 6H30s in the EHHA.


----------



## BoilermakerFan

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_I was looking for an Ultra quiet power environment and was wondering about this combo:

 R-Core 250-0-250

 and this: PSU for the heaters.

 Anybody see any problems with this combo? I know the PS is overkill, I originally started looking into this as a way to power the 6H30s in the EHHA._

 

I'd avoid the switching PSU, but that's just me. Hit Peter Daniels (AudioSector) up for one of his PSU boards and tell him you need the 6Vdc for heaters.


----------



## les_garten

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I'd avoid the switching PSU, but that's just me. Hit Peter Daniels (AudioSector) up for one of his PSU boards and tell him you need the 6Vdc for heaters._

 

Thanx! Just dropped him a query. I was wondering about the switching aspect. Don't want no buzzes.


----------



## TimJo

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_You can get 2.5" Aavid sinks for the power MOSFETs that are experiencing the higher heat dissipation: 531302B02500G Aavid Thermalloy Heatsinks

 But according to the specs, their thermal resistance of 8C/W is actually higher than the 2" version listed just above them in the catalogue, which doesn't make much sense to me 
	

	
	
		
		

		
		
	


	



_

 

Well, it looks to me both are less efficient because those have a smaller footprint (1/2" x 1 3/8"). I think Alex chose the one with the best heat dissipation based on what Mouser stocks.


----------



## ericj

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I have the 2-1/2" gold non-ROHS compliant versions of the Mouser part and I have the Digi-Key ones Beefy linked. Both are 2-1/2" and both fit. However, I plan to screw mine to the PCB, not solder mount... Just too much mass up high for me to trust a solder joint. Going with black 1" long 4-40s aluminum cap head screws (have to match the thermal expansion) and thread lock._

 

Soldering down the heatsinks actually isn't an option - there is no plating for it on the board. 

 This doesn't appear to have been an issue so far in prototyping, but if you prefer to secure the heatsinks you should either find a pinless version, or pull the pins out, and install screws.


----------



## Beefy

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Well, it looks to me both are less efficient because those have a smaller footprint (1/2" x 1 3/8"). I think Alex chose the one with the best heat dissipation based on what Mouser stocks._

 

I think you are confused. The Wakefield 637-20ABP specified in the PS and Amp BOM is 1.375" x 0.5" (2" high), as detailed in the data sheet. Identical to the Aavid I linked (but 2.5" high). The Wakefield claims 55C/6W, ~9.2C/W, whereas the Aavid is 8C/W.

 For the larger footprint sink, the one I linked is identical but 0.5" taller.

  Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_Soldering down the heatsinks actually isn't an option - there is no plating for it on the board. 

 This doesn't appear to have been an issue so far in prototyping, but if you prefer to secure the heatsinks you should either find a pinless version, or pull the pins out, and install screws._

 

UGH. Tapping heatsinks was the worst part of building the MMM. Solder pins all the way for me.


----------



## BoilermakerFan

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Well, it looks to me both are less efficient because those have a smaller footprint (1/2" x 1 3/8"). I think Alex chose the one with the best heat dissipation based on what Mouser stocks._

 

There are two different footprints. The smaller ones are the 1/2" x 1-3/8" and they do have 2-1/2" versions available. The bigger sinks are the 1"x 1-5/8" footprint. 

 Both of mine fit the scale print out of the PCB. I'll dig out my specific part numbers for you later...

  Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_Soldering down the heatsinks actually isn't an option - there is no plating for it on the board. 

 This doesn't appear to have been an issue so far in prototyping, but if you prefer to secure the heatsinks you should either find a pinless version, or pull the pins out, and install screws._

 

That is what I'm doing. I don't solder any of my heatsinks, but the big heatsinks Beefy linked at Digi-Key are pinned.

 EDIT: Man, Beefy is on the ball!


----------



## BoilermakerFan

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_More chum:




_

 

From a profile, how much taller are the very tips of the tubes above the tops of the 2" heat sinks?


----------



## Beefy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_From a profile, how much taller are the very tips of the tubes above the tops of the 2" heat sinks?_

 

This might give you some idea: http://scottbecker.net/tube/sheets/093/6/6S4A.pdf


----------



## TimJo

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Well, it looks to me both are less efficient because those have a smaller footprint (1/2" x 1 3/8"). I think Alex chose the one with the best heat dissipation based on what Mouser stocks._

 

 Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I think you are confused. The Wakefield 637-20ABP specified in the PS and Amp BOM is 1.375" x 0.5" (2" high), as detailed in the data sheet. Identical to the Aavid I linked (but 2.5" high). The Wakefield claims 55C/6W, ~9.2C/W, whereas the Aavid is 8C/W.

 For the larger footprint sink, the one I linked is identical but 0.5" taller._

 

Your correct. I was looking at the 567-677-20ABP. I think it's time for reading glasses.


----------



## les_garten

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Your correct. I was looking at the 567-677-20ABP. I think it's time for reading glasses. 
	

	
	
		
		

		
		
	


	


_

 

If you're buyin' readin' glasses, get a lot of pairs! This comes from experience!


----------



## TimJo

These just arrived. I'm bagging them up now, and they may even make it to the post office in time to go out today.

 BTW, I just noticed sachu, wiatrob, & dbel84 aren't listed for boards. Am I supposed to send their sets to Texas?


----------



## BoilermakerFan

...


----------



## TimJo

So you guys are taking two sets each now?


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_This might give you some idea: http://scottbecker.net/tube/sheets/093/6/6S4A.pdf_

 

Thanks. I guess it depends on how well or low I get my sockets mounted. They'll be close to the top though.





 And I'm beginning to think Alex had a premonition about my particular chassis when he drew up the amp PCBs...




































 I still have old components to remove, but they're all riveted in so I have to drill out the rivets. 

 A little hard to see because of the slight sag, but the 170mm width of the amp boards is perfect. There is clearance for the 2-1/2" heat sinks both above and below. Plenty of room to to fab shields to isolate power from signals, etc. 

 The trafo is not my PSU iron, but the custom E-Ps for a DIY Stax SRD7 that will be fed from an EHHA in a different build, but the PSU iron will probably be the same size. I'm going with custom E-P iron with a few extra secondaries now...

 I'll modify a lens for the top mount on the turret so it will be a "peep hole" in to see the glowing tubes. Regular and Pro jacks will fill the 3 o'clock and 9 o'clock openings. The potentiometer for the balanced OptiVols will be in the bottom hole with another modified lens as the knob. I have RFQs out for having the turret and front chrome plated again. 

 The little panel on the side of the top cover is an access panel to the former trim pots for the camera. I'll remote mount the trimmers and add tip jacks for the adjustments, just because the provision is already there, but it will probably be replaced with a custom aluminum piece with the eXStata Hybrid name on it. 

 The rear panel will be stripped, repainted, and relabeled before clear coat. I haven't decided if I'll try to salvage the original paint, try to color match, or just go with a new pearl effect paint for the housing. Switches to change bias and Balanced/SE will be mounted behind the little cover door on the back. Haven't decided if I'll add a separate heater power switch if I go DC heaters. Filtered/fused IEC or PowerCon will replace the existing power jack.


 EDIT: You know, with a few LiFEPo packs in series and an armored cable, I could have a portable 300Vdc 'stat amp!


----------



## BoilermakerFan

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_So you guys are taking two sets each now?_

 

Confirm shipping with Alex...


----------



## holland

Hi,

 I've been taking a break from this hobby, and just noticed this thread. Is everything that is available in the current pre-production group buy going to be available at a later time? Or is this a buy-in special only?

 I have alot to catch up on, in this thread, but would like to partake in the future if the bits are still around.


----------



## ericj

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_Hi,

 I've been taking a break from this hobby, and just noticed this thread. Is everything that is available in the current pre-production group buy going to be available at a later time? Or is this a buy-in special only?

 I have alot to catch up on, in this thread, but would like to partake in the future if the bits are still around._

 

We all hope that there is enough demand to justify a much bigger run of boards after a successful beta phase.


----------



## holland

So, are you saying I should buy in now? Where can I find the details (long thread)?


----------



## manaox2

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_We all hope that there is enough demand to justify a much bigger run of boards after a successful beta phase._

 

I'm lurking adamantly and been stockpiling a few parts (sockets, tubes, wire chassis, etc.).


----------



## ericj

Um, the beta run of boards has been delivered. Alex is doing the first build before he ships out the rest of them. I don't personally know if there are unclaimed boards from the first run. 

 I believe there will most likely be another run of boards.


----------



## Beefy

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_I'm lurking adamantly and been stockpiling a few parts (sockets, tubes, wire chassis, etc.)._

 

As you know, I'm so committed to building one of these that I'm trying to get some Stax phones


----------



## ericj

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Thanks. I guess it depends on how well or low I get my sockets mounted. They'll be close to the top though._

 

Mill-Max makes single-pin sockets that would allow most low-power tubes to be mounted pretty much flush to the board, given a board that's drilled for them. But I've never seen a headphone amp design that uses them. 

  Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_EDIT: You know, with a few LiFEPo packs in series and an armored cable, I could have a portable 300Vdc 'stat amp!_

 

Well, +/-300vdc


----------



## mypasswordis

I have too many 'stats NOT to build one of these. I'll wait until all the kinks are worked out, though... might as well, since I'm building something else at the moment.


----------



## ericj

Quote:


  Originally Posted by *mypasswordis* /img/forum/go_quote.gif 
_I have too many 'stats NOT to build one of these. I'll wait until all the kinks are worked out, though... might as well, since I'm building something else at the moment._

 

Meh. What kinks? I'm listening to my eXStatA Sand amp at work right now. 

 (I guess alex may decide that another resistor value might change or something).


----------



## Beefy

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_Meh. What kinks? I'm listening to my eXStatA Sand amp at work right now. 

 (I guess alex may decide that another resistor value might change or something)._

 

If you knew how much I hated desoldering, then I would definitely still consider a resistor change as a kink


----------



## BoilermakerFan

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_Mill-Max makes single-pin sockets that would allow most low-power tubes to be mounted pretty much flush to the board, given a board that's drilled for them. But I've never seen a headphone amp design that uses them. 

 Well, +/-300vdc_

 

Thanks. I actually have plenty of room. 

 A 700V pack could be made and I have a source of 1000Vdc rated armoured cable. It would be expensive, but it could be done and it would technically be portable. It just cracked me up when I looked at the handle and the thought popped in my head.


----------



## mypasswordis

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_Meh. What kinks? I'm listening to my eXStatA Sand amp at work right now. 

 (I guess alex may decide that another resistor value might change or something)._

 

Oh, I assumed that another beta run meant there was more testing to be done. If it's pretty much set, then that's cool, too. I'm more interested in playing with the tube version, though.


----------



## ericj

Quote:


  Originally Posted by *mypasswordis* /img/forum/go_quote.gif 
_Oh, I assumed that another beta run meant there was more testing to be done. If it's pretty much set, then that's cool, too. I'm more interested in playing with the tube version, though._

 

Well, the CCS is new. The existing prototypes just load the followers with resistors. 

 Both tube and all-sand versions are essentially stable aside from that change. I don't have my tube hybrid amp cased up yet, though.


----------



## mypasswordis

Ah, that's great that a CCS was added to the output stage. I definitely need to get around to building one of these.


----------



## runeight

Exactly, and now that I've built the amp board, there does seem to be a new problem. Adding the CCSs was a bit risky but not super risky. And in fact the CCSs are working perfectly.

 But the amps are oscillating. Both of them are doing exaclty the same thing so it is inherent to the circuit.

 Now the only thing that is different here is that the follower load resistors have been replaced with the CCSs to give you guys a bit more voltage swing. We can achieve much of this additional swing by simply using smaller value resistors in the original design. If we have to do this we can and, since everyone of the proto amps worked, I'm sure this will work because the new amp will be exactly like the protos.

 But, give me a bit to try to diagnose what the hey is going on. I checked this thoroughly in the sims in a variety of ways. Many times sims don't always show real world behavior, particularly oscillations. So I know pretty much what to look out for. But in this case the amp sims rock solid no matter how I provoke it to oscillate.

 Something is weird here and I'll try to get to it quickly.

 If there is one of you beta guys willing to be a gunea pig this would help. Here's what I'd ask of you. Make quick build using resistors for the follower loads. See if the amp is stable. If the amp is stable then we know that the CCSs have introduced the instability. If the amp is not stable then we know that the slightly modified layout has caused a problem. This is almost impossible, but stranger things have happened. 

 If I find the problem in the meantime then removing those four resistors and replacing them with the CCSs will not be difficult.


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Exactly, and now that I've built the amp board, there does seem to be a new problem. Adding the CCSs was a bit risky but not super risky._

 

Your signature is now so very, very appropriate......


----------



## runeight

Yes, indeed it is ...


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes._

 

DC out of Both model Trafos with load resistors and the filaments connected - will that measurement do or would you like the pre-reg DC as well?


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Exactly, and now that I've built the amp board, there does seem to be a new problem. Adding the CCSs was a bit risky but not super risky. And in fact the CCSs are working perfectly.

 But the amps are oscillating. Both of them are doing exaclty the same thing so it is inherent to the circuit.

 Now the only thing that is different here is that the follower load resistors have been replaced with the CCSs to give you guys a bit more voltage swing. We can achieve much of this additional swing by simply using smaller value resistors in the original design. If we have to do this we can and, since everyone of the proto amps worked, I'm sure this will work because the new amp will be exactly like the protos.

 But, give me a bit to try to diagnose what the hey is going on. I checked this thoroughly in the sims in a variety of ways. Many times sims don't always show real world behavior, particularly oscillations. So I know pretty much what to look out for. But in this case the amp sims rock solid no matter how I provoke it to oscillate.

 Something is weird here and I'll try to get to it quickly.

 If there is one of you beta guys willing to be a gunea pig this would help. Here's what I'd ask of you. Make quick build using resistors for the follower loads. See if the amp is stable. If the amp is stable then we know that the CCSs have introduced the instability. If the amp is not stable then we know that the slightly modified layout has caused a problem. This is almost impossible, but stranger things have happened. 

 If I find the problem in the meantime then removing those four resistors and replacing them with the CCSs will not be difficult._

 

Alex, When you say you could use one of us for a quick build, are you talking about with the new PC boards? I can certainly build it if you can get me the boards. Remember, I'm here in Texas, too, and from Austin, it should be only 1 day shipping here to Victoria, either by mail, or definitely UPS ground. I also have a scope to check for oscillation. I'm a willing "gunea pig" 
	

	
	
		
		

		
		
	


	




. Just let me know. Tommy.


----------



## wiatrob

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_Mill-Max makes single-pin sockets that would allow most low-power tubes to be mounted pretty much flush to the board, given a board that's drilled for them. But I've never seen a headphone amp design that uses them. _

 

Me neither - but have a boatload of them somewhere from my Nixie days... See if I can dig them up.


----------



## runeight

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_DC out of Both model Trafos with load resistors and the filaments connected - will that measurement do or would you like the pre-reg DC as well?_

 

Thanks. I'd like to know the pre-reg voltages at the filter caps along with the rail voltages with the trimpots set to deliver 36mA on the positive rail and 41mA on the negative rail.


----------



## runeight

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Alex, When you say you could use one of us for a quick build, are you talking about with the new PC boards? I can certainly build it if you can get me the boards. Remember, I'm here in Texas, too, and from Austin, it should be only 1 day shipping here to Victoria, either by mail, or definitely UPS ground. I also have a scope to check for oscillation. I'm a willing "gunea pig" 
	

	
	
		
		

		
		
	


	




. Just let me know. Tommy._

 

Thanks. I'd like to take you up on this. Do I have your email address?

 This problem is so weird. It's one of those "this can't happen" kinds of things.


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Thanks. I'd like to take you up on this. Do I have your email address?

 This problem is so weird. It's one of those "this can't happen" kinds of things. 
	

	
	
		
		

		
		
	


	


_

 

Alex, I PM'd you my email and contact #'s. I was going to tell you that when I built my KGSS, I also got oscillation. KG knew exactly what it was, and told me how to correct it. It involved a couple of 20pF caps added, (can't remember where right now, but they weren't put into the audio path). It corrected the problem. Anyway, yes, frustrating, but sure it'll be figured out.


----------



## runeight

THanks. Sent you email.

 I like the KGSS and I understand its design pretty well. I am not surprised that it needs compensation caps. 
	

	
	
		
		

		
		
	


	




 But, I am very surprised at this oscillation because the eXStatA doesn't really have the open loop gain and the NFB is very minor.

 This behavior is more like a multi-vibrator and this would make sense if the feedback returns were crossed. But they are not. The amp should be stable with or without the CCSs.

 I'll be back ...


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Thanks. I'd like to know the pre-reg voltages at the filter caps along with the rail voltages with the trimpots set to deliver 36mA on the positive rail and 41mA on the negative rail._

 


 Directly from the cap or can I take it from T1/3?


----------



## runeight

T1/3 is close enough.


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Thanks. I'd like to know the pre-reg voltages at the filter caps along with the rail voltages with the trimpots set to deliver 36mA on the positive rail and 41mA on the negative rail._

 

Argh. Looking at my notes, I set them for 38mA and 41mA - let me know if you want me to remeasure.

 All tubes lit and PS warmed up:

 269JX:

 t3: -332
 -r: -301
 t1: 333
 +r: 301

 270AX:

 t3: -314
 -r: -302
 t1: 316
 +r: 302


 Let me know if you want me to reset the current across the positive side.


----------



## runeight

No. This is good. And if your line voltage is typical it says that the 270AX is perfectly alright for this job.


----------



## wiatrob

Line voltage is spot on 119-120 on this circuit


----------



## runeight

Gentlemen, I believe I have found the problem. 

 I'm sure that this has happened before I have never seen it. Not ever.

 When you see the amp you'll see that the heatsinks form a set of caverns, essentially square metal boxes. Amazingly the devices are being coupled through the EM radiation from the heatsinks even though they are all plastic devices and are not electrically attached to the heatsinks.

 When I ground all of the heatsinks the oscillation stops. I left pads off the heatsinks to ensure no HV electrical problems with their pins. Kind of an extra measure of safety. But with the plastic devices they can be grounded without issue.

 This is simply the strangest thing I've seen in a long time, but looking at the amp layout it is not ridiculous. It is suprising, however, just how much the current passing through the devices is coupled into the heatsinks and radiated outward to the other heatsinks.

 I am blown away ... but happy.

 I'll verify this again and do more testing.


----------



## runeight

And after more testing it is only the two CCS heatsinks at the center of the board that are causing the problems. They were coupling the two channels to each other which is why they looked exactly the same. I am wondering if any of the rest of you will actually see this problem. I bet that some of you, maybe all of you, won't. And it may not appear at all on the tube amp.

 But, once the oscillation stopped I was able to adjust offset/balance without any problems. I'll let the amp burn in tomorrow when I can be there to watch it.

 If things stay stable tomorrow I'll be willing to ship out the boards and parts. Just have to wait for TimJo's caps and I can begin.

 Before I do, however, I'll post the spreadsheet one more time.


----------



## sachu

Weird but interesting indeed..

 Congrats Alex!!


----------



## HeadphoneAddict

You are amazing. Good catch!


----------



## Beefy

Oh wow. Good to know that EMI from the mains transformer is the least of our problems then! 
	

	
	
		
		

		
		
	


	




 So is there a plan to fix it? Just earlier in the thread we were talking about options for attaching the heatsinks. Giving them solder pads to ground might now be an option? Or is it a case of connecting them to signal ground?


----------



## Coreyk78

Maybe screw mounting the sinks to the board would be an easy way to do it, just attach a small ring terminal to the bottom of the board with the mounting screws and run wires to ground. That could work for this run of boards and maybe pads could be added for the next run.


----------



## runeight

Yes, the simple fix is to solder wires to the pins on the underside of the board and run these to the star ground (or screws if you want to take the time with wires attached to them). Fortunately, not a lot of extra work for you guys.

 But, I want to do a bit more experimenting today when I can catch the time. I have some other thoughts after sleeping on it. 

 I'll be back.


----------



## wiatrob

Could it have something to do with the addition of the CCS heat sinks?


----------



## runeight

Yes, this is the most likely cause, although the layout has changed slightly too. It is still an unusual thing though and I want to test more today.


----------



## TimJo

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_When you see the amp you'll see that the heatsinks form a set of caverns, essentially square metal boxes. Amazingly the devices are being coupled through the EM radiation from the heatsinks even though they are all plastic devices and are not electrically attached to the heatsinks.

 When I ground all of the heatsinks the oscillation stops. I left pads off the heatsinks to ensure no HV electrical problems with their pins. Kind of an extra measure of safety. But with the plastic devices they can be grounded without issue.

 This is simply the strangest thing I've seen in a long time, but looking at the amp layout it is not ridiculous. It is suprising, however, just how much the current passing through the devices is coupled into the heatsinks and radiated outward to the other heatsinks.
_

 

So I am curious about this theory. I don't know a lot about EM radiation, so forgive the simple-minded questions, but are the heatsinks acting as reflectors of the energy waves emanating from the devices, or are the devices actually charging the heatsinks, like a coil?

 I'm curious because I thought the heatsinks are an extruded aluminum, and I thought aluminum is somewhat inert to EM energy - or is it the steel pins in the heatsinks that are actually getting charged.

 It truly is a curious phenomena...


----------



## audionut

Alex, Glad you got it worked out!! I couldn't check my email or your posts as of 11:15 last night. My internet went down and just now came back up this morning at 10:30. Anyway, you can ship my boards anytime, (hybrid) as I have all my parts and didn't have to get in on the cap/jfet group buy. Have everything sitting on my bench and just waiting for boards.
	

	
	
		
		

		
		
	


	




 Thanks, Tommy


----------



## runeight

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_So I am curious about this theory. I don't know a lot about EM radiation, so forgive the simple-minded questions, but are the heatsinks acting as reflectors of the energy waves emanating from the devices, or are the devices actually charging the heatsinks, like a coil?

 I'm curious because I thought the heatsinks are an extruded aluminum, and I thought aluminum is somewhat inert to EM energy - or is it the steel pins in the heatsinks that are actually getting charged.

 It truly is a curious phenomena... 
	

	
	
		
		

		
		
	


	


_

 

I am not really sure how this is working. The currents flowing in the devices are very small and the CCSs are keeping the currents constant. Thus, there shouldn't be any current-created time-varying magnetic fields to induce current in the heatsinks which can then radiate to nearby heatsinks. In fact, I'm not sure that I believe that this is what it is. I cannot, however, think of a logical and sensible explanation at this moment.

 But I do know that if I let the two heatsinks float the amp pops into oscillation within a second or two.


 Aluminum is actually a pretty good conductor (used in power transimission lines because of its light weight) so there is no trouble inducing currents in it.

 Perhaps someone reading can offer an explanation.


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I am not really sure how this is working. The currents flowing in the devices are very small and the CCSs are keeping the currents constant. Thus, there shouldn't be any current-created time-varying magnetic fields to induce current in the heatsinks which can then radiate to nearby heatsinks. In fact, I'm not sure that I believe that this is what it is. I cannot, however, think of a logical and sensible explanation at this moment.

 But I do know that if I let the two heatsinks float the amp pops into oscillation within a second or two.


 Aluminum is actually a pretty good conductor (used in power transimission lines because of its light weight) so there is no trouble inducing currents in it.

 Perhaps someone reading can offer an explanation._

 

Is that with a stock or Maxed PSU?


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Perhaps someone reading can offer an explanation._

 

ghosts?

 What type of fastener are you using to attach the device to the heat sink?


----------



## Beefy

If he is following the BOM, it would be these kits. Pretty standard steel screw.


----------



## mypasswordis

If the magnetic field is constant due to a constant current (still a function of r), maybe the heatsinks are very slightly vibrating somehow and there's some paramagnetic effects with the magnetic permeability of aluminum being slightly higher than that of air? I'm picking at straws here... will think on it some more.


----------



## TimJo

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_And after more testing it is only the two CCS heatsinks at the center of the board that are causing the problems. They were coupling the two channels to each other which is why they looked exactly the same. I am wondering if any of the rest of you will actually see this problem. I bet that some of you, maybe all of you, won't. And it may not appear at all on the tube amp._

 

Just to be clear, you are referring to Q11R & Q12L - correct?

 If that's so, have you tried leaving them floating, but separating each channel by snapping the amp boards apart, to see if this prevents the oscillation?

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I am not really sure how this is working. The currents flowing in the devices are very small and the CCSs are keeping the currents constant. Thus, there shouldn't be any current-created time-varying magnetic fields to induce current in the heatsinks which can then radiate to nearby heatsinks. In fact, I'm not sure that I believe that this is what it is. I cannot, however, think of a logical and sensible explanation at this moment.

 But I do know that if I let the two heatsinks float the amp pops into oscillation within a second or two.


 Aluminum is actually a pretty good conductor (used in power transimission lines because of its light weight) so there is no trouble inducing currents in it.

 Perhaps someone reading can offer an explanation._

 

Your guess makes perfect sense theoretically. It is interesting though that the plastic bodies become both transmitters and receivers in order to induce the instability. 

 So is the oscillation likely a harmonic of some common mode current pulse being injected into each channel, based on the switching of the transistors within each CCS pair?


----------



## runeight

Quote:


  Originally Posted by *mypasswordis* /img/forum/go_quote.gif 
_If the magnetic field is constant due to a constant current (still a function of r), maybe the heatsinks are very slightly vibrating somehow and there's some paramagnetic effects with the magnetic permeability of aluminum being slightly higher than that of air? I'm picking at straws here... will think on it some more._

 

Possible. I don't hear anything if I put my ears close to them but that doesn't mean much and the oscillation continues if I grab the heatsinks.

 TimJo, it is Q11R and Q12L. I thought about separating the boards but I don't want to break them apart. Eventually I may have to do this test. It's peculiar though that this does not involve the other set of heatsinks in the middle of the board. I'll post a picture in a bit.

 I don't know exactly how it would be happening, but the CCSs are maintaining constant current during the oscillation. At least as measured at the control resistor and every other point inside the CCSs. The only spot on the CCSs where the scope shows oscillation is at the collectors of the HV transistors.

 luvdunhill the transistors are attached with screws and thermasil pads, flat washer, lock washer, and nut on the backside.

 Gents it is very hard for me to believe that this is EM radiation from the heatsinks. And even harder to believe any kind of capacitative coupling. Yet, I pull the clipleads off and the amps go crazy. Put them on and they are quiet as a mouse.


----------



## cetoole

Pickup of airborn RF, which then gets capacitive coupled to the CCS transistors? Definitely odd though.


----------



## TimJo

As another test, I wonder if you could take a sheet of some permeable metal connected to star ground, and position it between the two heatsinks, and see if by shielding them you can get it to work. 

 I'm not sure if it would work, or what it would prove, other than more evidence to the theory that it is wave-based coupling between the two heatsinks.

 BTW, what kind of frequency are you talking about on the collectors of the KSC5042's?


----------



## runeight

The mystery deepens. I am a bit wrong about the heatsinks. It turns out that grounding either heatsink on a single channel stops the oscillation. And, likewise, having one channel's heatsink grounded while the other floating causes the floating amp to oscillate.

 So I am wrong about this being a channel interaction. But it is still related to the heatsinks.

 Here's a not-very-flattering photo.







 The board is much better looking in person and not on a magenta colored towel that covers the work area.


----------



## runeight

cetoole/TimJo we cross posted. It could be local radiation but then, I think, if it were powerful enough to get through the heatsinks it would get into everything when the inputs are floating. But it doesn't. 
	

	
	
		
		

		
		
	


	




 TimJo, it's about 20kHz. Very low frequency for parasitic oscillations that might occur, say, from a mosfet with no gate stopper. This is why it seems almost like a multivibrator to me. Also because the oscillation slams the outputs to the rails producing almost a square wave, like the amp is flip-flopping.

 Now, with the new information, it could be some kind of coupling to the interntal components in the alleyway between the heatsinks. But, heck, I don't know.


----------



## runeight

One more thing. I've had it running for over an hour now. Offset/balance are extremely stable, less than 1V.


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Here's a not-very-flattering photo._

 

Looks pretty damn good to me...... very imposing with those big sinks


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_cetoole/TimJo we cross posted. It could be local radiation but then, I think, if it were powerful enough to get through the heatsinks it would get into everything when the inputs are floating. But it doesn't. 
	

	
	
		
		

		
		
	


	




 TimJo, it's about 20kHz. Very low frequency for parasitic oscillations that might occur, say, from a mosfet with no gate stopper. This is why it seems almost like a multivibrator to me. Also because the oscillation slams the outputs to the rails producing almost a square wave, like the amp is flip-flopping.

 Now, with the new information, it could be some kind of coupling to the interntal components in the alleyway between the heatsinks. But, heck, I don't know._

 

Is it only the SS version? I was planning to use 2-1/2" sinks, but now I wonder if that would make it worse. However, I'll screw mount mine so they'll be rigid and all will be grounded at the star. 

 Is there anyway you can remove Q11R/Q12L and bottom mount them? Just to see if it goes away with ungrounded sinks when their 180 degrees apart?


----------



## runeight

Thanks. I think it's ok for me to say that these are really good looking boards. I may have to case one of these up, but then I'll have to buy a set of stats. Egads.

 Here is the latest beta list including quads and caps. Please check your stuff and then send me email with your shipping address and prefered method. If you don't say, US packages will go first class or priority mail. Overseas will go whatever the business class is for 5-7day delivery.

 alex at cavalliaudio dot com


----------



## runeight

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Is it only the SS version? I was planning to use 2-1/2" sinks, but now I wonder if that would make it worse. However, I'll screw mount mine so they'll be rigid and all will be grounded at the star. 

 Is there anyway you can remove Q11R/Q12L and bottom mount them? Just to see if it goes away with ungrounded sinks when their 180 degrees apart?_

 

I haven't built the tube version so I don't know. And I don't have the parts for it now, but I'm betting that because the arrangement of heatsinks on the tube board is different you won't have this problem. 

 I suspect that bottom mounting would fix the problem because it would get the heatsinks away from all the other components. But I guess I can't say for sure.


----------



## runeight

Oh, and when you send me your shipping address please tell me your handle so I can match to the spreadsheet. I don't think I know everyone of you yet.


----------



## BoilermakerFan

Man, I blew by 1,000th post and didn't even notice!

 If anyone is interested, I emailed Jack at Electra-Print about a custom transformer for the Hybrid so I can run a few accessories and power the heaters with DC. Here's the email I sent:

  Quote:


 Jack

 I'm interested in a custom power supply transformer for a hybrid tube amp.

 120Vac primary or 120/240Vac primary

 A 500VCT secondary at 75mA - 80mA (assuming that's how to designate 250-0-250 secondary)

 A 24Vac Aux filament winding, 1A - will be rectified and regulated down to 24Vdc for a small SS attenuator and input switching relay. 

 A 12.6VCT - 1.5A - I plan to run 6.3Vdc to my heaters, but need the 12.6V to rectify and regulate down. The tubes draw about 2A at 6.3Vac. 

 The dimensions are tight on this build so if you could let me know the transformer size as well, I would appreciate it. 
 

And his reply:

  Quote:


 Brian,

 This transformer is $103.00 each with standard 120v primary, with dual primary it $133.00 each, standard bell ends vertical mount. Plus shipping.
 The dimensions or footprint, is 3" x 3 1/2" x 3 7/8" tall. 

 

I have two other customs from E-P and they are beefy. Jack's communication was great and they arrived a week earlier than expected. This transformer will deliver a little more current than the 369JX, plus it will provide power for my OptiVols and relay input switching if I build it in, as well as leads for 6V DC (or 12Vac for any crazy tube rollers) heaters with plenty of current head-room. I plan to keep my SylveXStata amp so I'm ordering only 120Vac primaries, but I know some of you guys need 240Vac or want dual voltage capability... Only $20 more than Mouser and an extra 10-15mA of power, plus saves me space as only one trafo.


----------



## runeight

Gents, one final test was the power LED. You may recall that I was concerned about the trace spacing between the LED traces and the bias traces. However, I couldn't have picked a better spot for close spacing because this is on the output side of the 4M7 resistors. These will make it very hard for arcing to occur.

 In any case the LED lights fine and pulling the extra 5mA from the filter caps hardly affects the voltage.

 In fact, I am wondering what may have happened when earlier measurements were made on the transformer. My little 270AX is handling all of this with ease. Which causes me to suggest that you all should be careful not to over-spec the transformer as this will only over burden the mosfets in the PS.

 The 270AX is 240-0-240/50mA and is doing a good enough job. Not to say that you shouldn't diy because that's most of the fun I know. Just don't make the PS do extra work that it doesn't need to do. 
	

	
	
		
		

		
			





 So, boilermakefan, unless you're planning to draw additional current from the PS I think you can reduce the current spec on that transformer by quite a bit. Particularly if that helps to reduce cost.


----------



## ericj

BMF, the dual transformer rig is when using cheap Triads to power the sand amp. Each of the triads provides one 230v secondary (and they're really poorly regulated, and way bigger than they need to be, so we get 250v out of them easy) 

 It only takes one hammond trafo to power either amp, but the hammond is more expensive than two triads and has a heater winding that the sand amp doesn't need.


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Gents, one final test was the power LED. You may recall that I was concerned about the trace spacing between the LED traces and the bias traces. However, I couldn't have picked a better spot for close spacing because this is on the output side of the 4M7 resistors. These will make it very hard for arcing to occur.

 In any case the LED lights fine and pulling the extra 5mA from the filter caps hardly affects the voltage.

 In fact, I am wondering what may have happened when earlier measurements were made on the transformer. My little 270AX is handling all of this with ease. Which causes me to suggest that you all should be careful not to over-spec the transformer as this will only over burden the mosfets in the PS.

 The 270AX is 240-0-240/50mA and is doing a good enough job. Not to say that you shouldn't diy because that's most of the fun I know. Just don't make the PS do extra work that it doesn't need to do. 
	

	
	
		
		

		
		
	


	




 So, boilermakefan, unless you're planning to draw additional current from the PS I think you can reduce the current spec on that transformer by quite a bit. Particularly if that helps to reduce cost. 
	

	
	
		
		

		
		
	


	


_

 

Is the 250-0-250 xfmr in the BOM still ok to use for the hybrid?? Hopefully so, as I already got mine from Mouser.


----------



## runeight

Yes, it's ok to use. And in certain low line voltage situations is may be essential for the amp to work, but for me here in central Texas, it's not needed.

 The PS mosfets will get a bit hotter, but probably not dangerously so.


----------



## runeight

The rig has been on for about 5 hours now. It's hot, but acceptable. The offset/balance have stayed less than 1V.

 And yes, the amps amplify. My gain is very close to 1000. YMMV depending on the exact gm of the jfets.


----------



## Emooze

Email sent, everything looks good.

 Just to be clear, I'll be building my amp to be SE and the input grounds are just to be connected to each other and their respective pads on the boards, right? I'm assuming input ground and AC ground are to be isolated or should there be a ground loop breaker?


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_The 270AX is 240-0-240/50mA and is doing a good enough job. Not to say that you shouldn't diy because that's most of the fun I know. Just don't make the PS do extra work that it doesn't need to do. 
	

	
	
		
		

		
		
	


	




 So, boilermakefan, unless you're planning to draw additional current from the PS I think you can reduce the current spec on that transformer by quite a bit. Particularly if that helps to reduce cost. 
	

	
	
		
		

		
		
	


	


_

 

 Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_BMF, the dual transformer rig is when using cheap Triads to power the sand amp. Each of the triads provides one 230v secondary (and they're really poorly regulated, and way bigger than they need to be, so we get 250v out of them easy) 

 It only takes one hammond trafo to power either amp, but the hammond is more expensive than two triads and has a heater winding that the sand amp doesn't need._

 

This is only for the Hybrid... I'm only ordering one. I just took the spec from the Hammond 369JX, then bumped the current on the B+ secondaries up 15mA to cover any sag potentially introduced by the additional 24Vac winding draw. 

 The 12.6VCT should have been dual 6.3V so I can series for 12.6V to feed the AudioSector PSU for 6.3Vdc heaters. 

 The 24Vac secondary is needed for my OptiVols, a small phono stage, a USB DAC, and possibly a relay I/O switch like a scaled down Darwin If I don't use ALPS 4 position switches. 

 So, with a quality trafo like E-P, is the extra 15mA on the B+ secondaries unnecessary? 

 My household voltage has been rock steady 120V for 9 years since I upgraded my service and rewired the entire house, but I'm more concerned about lower line voltages at meets, especially CanJam, so I was planning to stay at 250V-0250V. I'm running 2-1/2" sinks too so they'll dissipate a little more power. 

 I really appreciate the help guys, I'm not trying to over-power the PSU, just trying to make sure it has what it needs while also supply other separate components.


----------



## les_garten

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_This is only for the Hybrid... I'm only ordering one. I just took the spec from the Hammond 369JX, then bumped the current on the B+ secondaries up 15mA to cover any sag potentially introduced by the additional 24Vac winding draw. 

 The 12.6VCT should have been dual 6.3V so I can series for 12.6V to feed the AudioSector PSU for 6.3Vdc heaters. 

 The 24Vac secondary is needed for my OptiVols, a small phono stage, a USB DAC, and possibly a relay I/O switch like a scaled down Darwin If I don't use ALPS 4 position switches. 

 So, with a quality trafo like E-P, is the extra 15mA on the B+ secondaries unnecessary? 

 My household voltage has been rock steady 120V for 9 years since I upgraded my service and rewired the entire house, but I'm more concerned about lower line voltages at meets, especially CanJam, so I was planning to stay at 250V-0250V. I'm running 2-1/2" sinks too so they'll dissipate a little more power. 

 I really appreciate the help guys, I'm not trying to over-power the PSU, just trying to make sure it has what it needs while also supply other separate components._

 

Hey,
 Can you tell me what you are using from audiosector? I sent him an email to Dan and he said he had nothing to drive tube heaters??


----------



## BoilermakerFan

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_Hey,
 Can you tell me what you are using from audiosector? I sent him an email to Dan and he said he had nothing to drive tube heaters??_

 

I'm just using his board, I'll have to spec the components to get 6.3Vdc off the regulator once I confirm I'm actually seeing 17.6V-17.8Vdc after rectification. I'll email Peter and explain what I'm doing... I know the boards can be used to produce 5Vdc and 3.3Vdc with new component values as we use them for the ShigaClone CD transport PSUs. Have to use a LM338 for 5A versus LM317 at 1.5A too.


----------



## Beefy

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_Just to be clear, I'll be building my amp to be SE and the input grounds are just to be connected to each other and their respective pads on the boards, right? I'm assuming input ground and AC ground are to be isolated or should there be a ground loop breaker?_

 

I don't think so. SE signal connects to +, SE ground connects to -. Nothing connects to the amp's ground input.


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_
 In fact, I am wondering what may have happened when earlier measurements were made on the transformer. My little 270AX is handling all of this with ease. Which causes me to suggest that you all should be careful not to over-spec the transformer as this will only over burden the mosfets in the PS._

 

IIRC, the measurements I just posted were in line with my earlier measurements. I have the sand/follower mod version up next the hybrid. Haven't A/B'd.

 Interested to hear the CCS version... although I do like the simplicity of the earlier design...


----------



## les_garten

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I'm just using his board, I'll have to spec the components to get 6.3Vdc off the regulator once I confirm I'm actually seeing 17.6V-17.8Vdc after rectification. I'll email Peter and explain what I'm doing... I know the boards can be used to produce 5Vdc and 3.3Vdc with new component values as we use them for the ShigaClone CD transport PSUs. Have to use a LM338 for 5A versus LM317 at 1.5A too._

 

OK, you're using the PS board from one of his amp kits.


----------



## Coreyk78

Email with shipping info sent. 
 I already have a 269JX sitting on my desk here, so I guess my PSU will just have to run a little warm. Heat is relative anyway, I finished building my Pass Aleph-J clone last week and I have a new definition of warm electronics now, hehe


----------



## Emooze

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I don't think so. SE signal connects to +, SE ground connects to -. Nothing connects to the amp's ground input._

 

Alright so SE ground should be isolated from AC ground then?


----------



## BoilermakerFan

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_OK, you're using the PS board from one of his amp kits._

 

Yes. Sorry, I thought you understood that. It's a very small, compact package with pads for twin leads to feed two gainclones so it can feed the two heater circuits. 

 I emailed Peter for clarifications. I'll let you know.

 He also has a PSU board for the DACs and Phono stages, but that's not a separate piece and it's designed to hold a Hammond solder-mount CT trafo.


----------



## runeight

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_Alright so SE ground should be isolated from AC ground then?_

 

To run SE you'll need to:

 1. Connect the -In to the In G terminal on the input terminal block.
 2. Connect the SE input to the +In terminal and In G.
 3. Connect the SG terminals and the PS G terminal to the star ground point

 I haven't yet had time to put up a wiring diagram for you guys. I may not get to it in time, but I know that you all can help each other if I can't.

 TimJo's caps will probably get here Monday so I won't be able to ship to those of you want caps until Tue.

 There are a few who don't and I will try to get those out sooner.


----------



## audionut

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_Alright so SE ground should be isolated from AC ground then?_

 

Alex, Can you provide some info on wiring the volume pot if you're going SE? I know the center tap of pot goes to In+, the top leg of pot goes to center connection (+) of your RCA input, and the botton leg of pot goes to ground along with the - or ground terminal on the RCA jack. I was thinking that you need to tie the gate of Q2 to ground also?? Can you clear this up for those who are not quite sure. Thanks Sorry, Cross Post


----------



## runeight

So, did the explanation help?

 Gents, I now have an extra 269JX if any of you would like one. I can ship it with your boards.


----------



## BoilermakerFan

I know it's early and CanJam is 7 months away, but is anyone else planning to be at CanJam and going to bring an eXStata? My hybrid will be there if I am, and I've already got it on the calendar so it would be an urgent work or family matter that would cause a cancellation for me.


----------



## Coreyk78

The next CanJam is in Chicago huh? That's actually driving distance for me, I might have to think about trying to go. Maybe if I can convince my best buddy to come with me, even though he's not really into headphones, then I wouldn't have to drive solo.


----------



## BoilermakerFan

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_The next CanJam is in Chicago huh? That's actually driving distance for me, I might have to think about trying to go. Maybe if I can convince my best buddy to come with me, even though he's not really into headphones, then I wouldn't have to drive solo._

 

Well, your about 3 weeks out before you can book tickets for that weekend, but Southwest Airlines was $75 airfare one-way, $171.20 with taxes round trip to Chicago Midway. I've done the drive from Minneapolis (Burnsville) to Milwaukee several times and it's not too bad, but stepping on a plane is a lot easier and only about twice the cost of gas as long as you could get someone in Chicago to meet you or pick you up. 

 My drive is 5-1/2 hours according to Mapquest and such, but in reality it's about 7 hours once stops and traffic are figured in, but we usually go up to Chicago two to three times a year.


----------



## runeight

Say, gents, we have another problem. But not a build problem.

 The fab house confused the paneling when they quoted me on these boards and they confused the manufacturing. Now that I have broken out the box I only have half the number of amp boards that I expected to have. I have the right number of PS boards.

 I just talked with the fab and cleared up what they mean by paneling which was not exactly how I sent them the gerbers.

 So, they are looking into the cheapest and fastest way to fix the problem. But this also means that the price I quoted you guys is not accurate. However, let me see what they come back with and I will do everything to maintain the $20 per pair or something very close to this.

 My bad, but I can tell you that the fab and I won't have this confusion again. 

 Two board sets went out today to beta testers who don't need the caps.


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Say, gents, we have another problem. But not a build problem.

 The fab house confused the paneling when they quoted me on these boards and they confused the manufacturing. Now that I have broken out the box I only have half the number of amp boards that I expected to have. I have the right number of PS boards.

 I just talked with the fab and cleared up what they mean by paneling which was not exactly how I sent them the gerbers.

 So, they are looking into the cheapest and fastest way to fix the problem. But this also means that the price I quoted you guys is not accurate. However, let me see what they come back with and I will do everything to maintain the $20 per pair or something very close to this.

 My bad, but I can tell you that the fab and I won't have this confusion again. 

 Two board sets went out today to beta testers who don't need the caps. 
	

	
	
		
		

		
		
	


	


_

 

Man, I would not want the cheapest way to fix, I'd prefer to have the board's build quality match the ones you posted up in black. I'm ok waiting too.

 I'm also OK with a price increase if the FAB is going to try to make you eat the expense.


----------



## runeight

No, it will be the same quality boards, exactly what I have now. I am just trying to work out quantity and speed of delivery at the best price. So far they are being reasonable and it looks like I'll have the new set by next Friday.

 Between now and then I have 11 tube boards left. Half of what we need. So, perhaps those of you who are not ready to build immediately could get the later shipments and those who are anxious to go can get the next 11 hybrids? I have almost enough sand boards because I ordered and extra couple for me to test and play with.

 Sorry for the trouble. I sent them gerbers with two amp channels on a single board. To me this was one part. But to them this was two parts (each channel being a part). Hence, I only ordered half of the amount needed plus a few extras.

 Since they did not mis-represent the qty or make a mistake, I'll have to pay for the additional parts.

 I think $5 extra per set could be reasonable based on preliminary quotes. $25 instead of $20. I'll absorb the rest because this is beta testing and you guys are all contributing your time and $$$ to verify that we have a good project. And, as the proto guys know, I always appreciate your time and money.


----------



## runeight

I meant to add that if the new price is outside your original window please let me know. I will completely understand.


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_No, it will be the same quality boards, exactly what I have now. I am just trying to work out quantity and speed of delivery at the best price. So far they are being reasonable and it looks like I'll have the new set by next Friday.

 Between now and then I have 11 tube boards left. Half of what we need. So, perhaps those of you who are not ready to build immediately could get the later shipments and those who are anxious to go can get the next 11 hybrids? I have almost enough sand boards because I ordered and extra couple for me to test and play with.

 Sorry for the trouble. I sent them gerbers with two amp channels on a single board. To me this was one part. But to them this was two parts (each channel being a part). Hence, I only ordered half of the amount needed plus a few extras.

 Since they did not mis-represent the qty or make a mistake, I'll have to pay for the additional parts.

 I think $5 extra per set could be reasonable based on preliminary quotes. $25 instead of $20. I'll absorb the rest because this is beta testing and you guys are all contributing your time and $$$ to verify that we have a good project. And, as the proto guys know, I always appreciate your time and money._

 

I can wait for both... (glances over at the list of projects in the cue...) I have plenty to keep me busy.


----------



## MrMajestic2

I dont mind the added cost plus I can wait for my tube a bit longer.


----------



## scompton

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_I dont mind the added cost plus I can wait for my tube a bit longer._

 

x2


----------



## Emooze

Pity about the boards. I'm ok with waiting and the price change

 Also my SE input wiring would look like so:


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Say, gents, we have another problem. But not a build problem_

 

Alex, I recently had the same problem with a fab house. My board had four identical circuits on it, and they kept wanted to chop the board up in fourths, despite what my Gerber files said. I wish more people used a separate board outline Gerber, rather than overloading the silk (often times a zero width line) with multiple meanings...


----------



## audionut

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_Pity about the boards. I'm ok with waiting and the price change

 Also my SE input wiring would look like so:





_

 

This should be correct.


----------



## spritzer

That is indeed correct.


----------



## Lou Erickson

I can definitely wait for my boards. The extra cost is not a problem, either. I'd rather pay more than have you eat the difference, in fact. You've done so much great stuff for this project, I'd hate to see it cost you any more.


----------



## Coreyk78

The extra cost is no problem for me.


----------



## scompton

Quote:


  Originally Posted by *Lou Erickson* /img/forum/go_quote.gif 
_I can definitely wait for my boards. The extra cost is not a problem, either. I'd rather pay more than have you eat the difference, in fact. You've done so much great stuff for this project, I'd hate to see it cost you any more._

 

Well said


----------



## runeight

Thanks for this thought. But I am really ok with the $5 adjustment. It will get me close enough.

 In the meantime 12 of you have not yet sent me a mailing address. I'm waiting...


----------



## Coreyk78

Had a box waiting for me on my front step from Par-Metal when I got home. I now have cases for my Exstata and Buffalo24 
	

	
	
		
		

		
		
	


	




 edit- Argh... I should have opened the box before I typed that out, just opened it now, and the cases are clear finish when they are supposed to be black. Only the third time that they've sent me the wrong cases lol. I ordered clear for my Aikido and got gold alodine, a 12"x16" for a speaker amp and they sent 16"x16" (sent that one back). At least these are the right size, I'm just gonna keep 'em and paint them myself if I feel like it. My Antek orders have always been spot on, I think they need a new shipping person for par-metal though, haha.


----------



## runeight

Gents, I'm going to do wiring diagrams this weeked. Can you guys send me the various output jack options including the bias pins.

 I'll assume standard XLR or RCA for the inputs.


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Gents, I'm going to do wiring diagrams this weeked. Can you guys send me the various output jack options including the bias pins.

 I'll assume standard XLR or RCA for the inputs._

 

here you go Alex..
Stax jack pin outs


----------



## runeight

Thanks.

 As for the rig, I turned it on tonight about an hour ago. It came to operating point in less than 1 second. The offset/balance on the right channel were both less than 1V. On the left they were less than 2V and drifted down to below 1V within a few seconds.

 There are no visible voltage swings. The amps just go quickly to their op points.


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Thanks.
 There are no visible voltage swings. The amps just go quickly to their op points. 
	

	
	
		
		

		
		
	


	


_

 

Good to know - that's the experience I've had with the protos. Re-tweaked it t'other night down below 1V each and that's where it's stayed...


----------



## sergery

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Thanks. I think it's ok for me to say that these are really good looking boards. I may have to case one of these up, but then I'll have to buy a set of stats. Egads.

 Here is the latest beta list including quads and caps. Please check your stuff and then send me email with your shipping address and prefered method. If you don't say, US packages will go first class or priority mail. Overseas will go whatever the business class is for 5-7day delivery.

 alex at cavalliaudio dot com_

 

Just wanted to make sure you saw this - I don't need tubes, but thanks very much for offering this package. 
	

	
	
		
		

		
		
	


	




 sergery


----------



## BoilermakerFan

Ordered my custom Electro-Print iron today after speaking to Jack on the phone for almost an hour. I wish it registered that he lives in Las Vegas as I was just out there for the SEMA show. Next year, I'm taking him out for a beer just to chat. I learned more about transformers in an hour on the phone with him than I have in the last ten years!

 Final specs are:

 120v primary

 500vct @ 65ma
 24v @ 750ma
 12v @ 400ma
 12v @ 400ma
 8v @ 250ma
 8v @ 250ma
 12.6v @ 2.5a

 All of the secondary windings required a larger frame and M6 so the price went up, but IMHO, it was well worth the expense to have all the windings for my integrated accessories like the phono stage, relay switching, OptiVols, and DAC. 

 E-P transformers are definitely beefier and hold tolerance and spec, so their 2.5A winding will deliver 2.5A at 6.3V from the start, no voltage spike and decay, no sag. So... anyone who hasn't ordered a Hammond, consider a 480VCT @ 60mA with 6.3V @ 2.5A heaters and it should be the same or even lower cost than what I was quoted initially and be in a 3"x3-1/2"x3-7/8" package.


----------



## ericj

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Gents, I'm going to do wiring diagrams this weeked. Can you guys send me the various output jack options including the bias pins.

 I'll assume standard XLR or RCA for the inputs._

 

The ESP/950 pins are here: 

ESP/950 Electrostatic Stereophone - Wikiphonia

 The socket is custom manufactured for Koss and you can get one by buying an extension cord for about $16 shipped, then get creative with mounting options. The truly ambitious DIYer can probably fabricate one out of teflon and socket pins, but, what a lot of work - most people with that kind of ambition would just recable them with a stax extension cord. 

 he60 is like this: 

  Code:


```
[left] _____________ / \ | 1 2 3 4 5 6 | --------------- 1: right + 2: right bias 3: right - 4: left - 5: left bias 6: left +[/left]
```

Dunno if it's a widely available connector or what. Not an expert there. Someone who knows more should chime in - i don't even know if this is a diagram of the male or female connector. Then again, getting it backwards would just reverse the channels. 

 The HE90 connector is described in a round-about way here: Sennheiser HE90 "Orpheus" electrostatic headphone connector info and sounds like something you can potentially purchase. 

 The SR-001 connector is described here: http://www.head-fi.org/forums/4464183-post141.html (but there is no commercial connector available - DIYers must fabricate their own out of a bit of circuit board and something to hold a bit of circuit board).

 People with miscellaneous OEM stax (and Stax clones) are better off rewiring their gear to the Stax low-bias standard (and adding a 5 megohm resistor to the bias line, preferably inside the earcup. At least this appears to be true of the Marantz, and probably true of the Magnavox, Radioshack, K-Mart, etc)


----------



## Beefy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_So... anyone who hasn't ordered a Hammond, consider a 480VCT @ 60mA with 6.3V @ 2.5A heaters and it should be the same or even lower cost than what I was quoted initially and be in a 3"x3-1/2"x3-7/8" package._

 

Which of those dimensions is height?

 And any idea how much the price bump is for universal primaries?


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Which of those dimensions is height?

 And any idea how much the price bump is for universal primaries?_

 

Dual Primaries added $30, height is 3-7/8".

 But email Jack and ask for the actual quote as originally asked for a 12VCT secondary, not standard 12V, plus I had a 24V @ 1A aux winding in it.


----------



## Beefy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Dual Primaries added $30, height is 3-7/8".

 But email Jack and ask for the actual quote as originally asked for a 12VCT secondary, not standard 12V, plus I had a 24V @ 1A aux winding in it._

 

No good, as that is far too high. Even the Hammond at 77mm high only just fits inside a 2U chassis.

 370AX or 369JX it is.


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_No good, as that is far too high. Even the Hammond at 77mm high only just fits inside a 2U chassis.

 370AX or 369JX it is._

 

He can do a horizontal mount, 3" height then, but it's an adder, No idea how much though. I have vertical height, not area, so taller was better for me. 

 My Beefy trafo, 
	

	
	
		
		

		
			





, will probably have to step up to the larger 150 frame so it will be the 4" cube like my mock up pics. Kinda stinks too as I made a cardboard mock-up of the smaller one for fitting. It will fit, I just have to move the PSU forward and fab up more shielding... Luckily, aluminum or steel sheet is cheap, easy to fab, and can be painted with the base or side panels.


----------



## runeight

Gents, I've stared the wiring section. Should be visible on the website.

 Don't know how to handle all the O/P jack variations at the moment, but you'll be able to figure it all out.

 If you guys see any errors on the website or sections that are not clear please let me know.


----------



## TimJo

Looks good. 
	

	
	
		
		

		
		
	


	




 For the heatsink grounding, do we know if this is needed for the hybrid board yet? 

 If we are lucky, maybe it will just require grounding the CCS sinks.


----------



## TimJo

One other question. In my mind I had pictured the heater bias resistors (and their -300 volt connection) being located near the transformer, and had laid out the wiring with them at a terminal block next to the transformer, where the heater cables are distributed. Being new to elevated LV supplies, is this okay, or do they need to be closer to the filaments? 

 The reason I ask is I just noticed last night that you had provided pads on the left channel board when I was studying the pfd of the silkscreen a bit more closely. Oh well...


----------



## runeight

I'm willing to bet that the hybrid boards will not oscillate because the heatsinks are far apart. But I do know that grounding the CCS heatsinks solves this problem.

 I have just posted to the website two ways I think will work on the sand map. I've only tried one, but if the problem is capacitative coupling through the heatsinks, the other method should work too. In fact, if someone would have time to try the second method that would be great. I've already soldered the jumpers on my sand board.

 As for heaters, I aim to be a full service designer. 
	

	
	
		
		

		
		
	


	




 All you need to do is to include RH1/RH2 on the board and you won't have to worry about the heater biasing. The proto guys did not detect any negative effects from attaching the heaters directly to the negative rail. However, some particularly dirty line/heater conditions might cause problems. We'll have to see.


----------



## luvdunhill

Guys, there were a few people in this thread interested in my Teflon Stax jacks. I'm ready to go, just need to figure out how much material I need to buy (which will determine the final cost). Please PM me with an estimated quantity you'd be interested in.


----------



## Beefy

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Guys, there were a few people in this thread interested in my Teflon Stax jacks. I'm ready to go, just need to figure out how much material I need to buy (which will determine the final cost). Please PM me with an estimated quantity you'd be interested in._

 

I suspect you might get asked these a few times, so I'll get it right out there in the open...... 
	

	
	
		
		

		
		
	


	




 Will there be the option for both pro and normal bias?

 And do you have you got a technical drawing, to see what casework will be like?


----------



## green0153

I can wait for my boards.


----------



## ericj

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Gents, I've stared the wiring section. Should be visible on the website.

 Don't know how to handle all the O/P jack variations at the moment, but you'll be able to figure it all out.

 If you guys see any errors on the website or sections that are not clear please let me know._

 

I don't think you need to go into exhaustive detail on the non-stax connectors. I just thought I'd try to get the connector descriptions and pin assignments into a single post.

 There's a rumor that the HE60 connector is compatible with one found at auto parts stores, btw, but not having an he60 i can't verify it. There are probably people who custom manufacture them. But, the HEV70 is said to be a wretched amp, so it would not surprise me if people preferred to just convert the HE60 to a stax connector.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_I don't think you need to go into exhaustive detail on the non-stax connectors. I just thought I'd try to get the connector descriptions and pin assignments into a single post.

 There's a rumor that the HE60 connector is compatible with one found at auto parts stores, btw, but not having an he60 i can't verify it. There are probably people who custom manufacture them. But, the HEV70 is said to be a wretched amp, so it would not surprise me if people preferred to just convert the HE60 to a stax connector._

 

The HEV70 isn't that bad - I think it is better than the Koss E90 when paired with the HE60. True, the SRM-1 Mk2 Pro is slightly better and the SRM-T1 and Woo GES are a good bit better, but it isn't total poo.


----------



## BoilermakerFan

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_The HEV70 isn't that bad - I think it is better than the Koss E90 when paired with the HE60. True, the SRM-1 Mk2 Pro is slightly better and the SRM-T1 and Woo GES are a good bit better, but it isn't total poo._

 

So did you recable or have a adapter cable made?

 The custom HE60s I'm building for a member are being recabled with a Stax cable...


----------



## HeadphoneAddict

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_So did you recable or have a adapter cable made?

 The custom HE60s I'm building for a member are being recabled with a Stax cable..._

 

The end of the HE60 was cut off and a stax plug was installed, then the remnant had a Stax jack installed to use it as an adapter.


----------



## runeight

So, I hadn't checked yesterday's mail until today. The caps are here.

 Not everyone has supplied a shipping address so I'm just going to start sending to those who have until I run out of boards.


----------



## runeight

Meanwhile, I've been running the sand amp for hours, at least 20-30 by now. Cycled it many times. Comes up great every time and doesn't drift very much.


----------



## Beefy

And it sounds........?


----------



## luvdunhill

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_And it sounds........? 
	

	
	
		
		

		
		
	


	


_

 

sinusoidal?


----------



## TimJo

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_sinusoidal?_


----------



## Beefy

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_sinusoidal?_

 

You're not helping!


----------



## runeight

Gents, I have packaged the following for shipment tomorrow:

 emooze
 awpagan
 studeb
 sergery
 coreyk78
 minivan
 mrmajestic
 lou erickson
 boilermakerfan
 headphoneaddict

 Plus two others who wish to be anonymous.

 This packages include the quads and caps. TimJo was extraordinarily helpful in packaging up the caps for us. Saved mucho time. 
	

	
	
		
		

		
		
	


	




 I still have two sand boards and two tube boards remaining in this lot. If anyone else would like theirs now please send me your address.


----------



## runeight

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_And it sounds........? 
	

	
	
		
		

		
		
	


	


_

 

Ahhh. I don't have stats. But I know how it looks.


----------



## runeight

Let me modify my statement. I heard the original version with a pair of HE60s and was able to compare it to a very famous, reference DIY amplifier with HD800s. IMHO, the eXStatA/HE60 combination was better. But then I designed it so you all will decide for yourselves.


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Ahhh. I don't have stats. But I know how it looks. 
	

	
	
		
		

		
		
	


	


_

 

I look forward to some specs based on the scope then!


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Gents, I have packaged the following for shipment tomorrow:

 emooze
 awpagan
 studeb
 sergery
 coreyk78
 minivan
 mrmajestic
 lou erickson
 boilermakerfan
 headphoneaddict

 Plus two others who wish to be anonymous.

 This packages include the quads and caps. TimJo was extraordinarily helpful in packaging up the caps for us. Saved mucho time. 
	

	
	
		
		

		
		
	


	




 I still have two sand boards and two tube boards remaining in this lot. If anyone else would like theirs now please send me your address._

 

Sweet! Alex, can you hold mine for shipment until Thursday please? I'll be buried all week and will not be at the home office to receive the boards until Sat. or the following week. My wife works too so they would be sitting on the door step and I'd prefer to not have that happen, especially with rain in the forecast.


----------



## runeight

One more set has been packaged. One sand and one tube board left. The rest will be here on Friday.


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_One more set has been packaged. One sand and one tube board left. The rest will be here on Friday._

 

If you get two requests for the two remaining ones, you can feel free to relabel my package for the second request as one more day before you ship really won't bother me, but earlier shipping would.


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Let me modify my statement. I heard the original version with a pair of HE60s and was able to compare it to a very famous, reference DIY amplifier with HD800s. IMHO, the eXStatA/HE60 combination was better. But then I designed it so you all will decide for yourselves. 
	

	
	
		
		

		
		
	


	


_

 

Remember - Alex likes designing most. The fact that we get to enjoy _the sound_ is a convenient side effect of his obsesssion...


----------



## Emooze

Sweet, thanks Alex. gonna place the order for the rest of my parts tomorrow then.


----------



## HeadphoneAddict

We should take up a collection to buy Alex a pair of SR-003.


----------



## sachu

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_We should take up a collection to buy Alex a pair of SR-003._

 

Or a pair of Koss ESP950s..I had suggested this to a couple of the proto team members but it didn't go forward then..but am up for contributing to the pot.


----------



## runeight

Thanks gents for even thinking of this. But I have been gifted with three really nice dynamic headphones.


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Thanks gents for even thinking of this. But I have been gifted with three really nice dynamic headphones._

 


 Mind telling us Which dynamics you have?? Are you using one of Your amps to power them?


----------



## runeight

Gents, the following care packages just went out:

 emooze
 awpagan
 bada bing
 studeb
 sergery
 scompton
 headphoneaddict (and his ghost writer)
 coreyk78
 minivan
 mrmajestic
 lou erickson

 It appears that audionut got the first boards today.

 Please let me know when your packages arrive or if I made a mistake in what you were supposed to get.

 Now the fun starts.


----------



## audionut

Alex, or anyone, Did R10,11 150k's get omitted when power supply was modified earlier in the thread? Found R9,12 just fine but not seeing R10,11. Maybe I'm just blind or maybe I missed the earlier mod/omission?? Double checking. Thank, Tommyy


----------



## runeight

My bad in the BoM. R10/R11 have been elminated from the build. You do have all the 51V zeners that replace them?

 Sorry.


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_My bad in the BoM. R10/R11 have been elminated from the build. You do have all the 51V zeners that replace them?

 Sorry._

 

That would be Z3-Z5, Z6-Z8, correct? If so, I have them


----------



## runeight

Yes.


----------



## Beefy

Looking for the replaced zeners got me looking at the website again, and I am curious about the ground wiring.

 What would you recommend doing with respect to connecting an earth ground? For a HV project such as this, I would absolutely like to keep the chassis earthed for safety, but that brings up the problem of ground loops......


----------



## ericj

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Looking for the replaced zeners got me looking at the website again, and I am curious about the ground wiring.

 What would you recommend doing with respect to connecting an earth ground? For a HV project such as this, I would absolutely like to keep the chassis earthed for safety, but that brings up the problem of ground loops......_

 

My SS build is inside an aluminum enclosure with the enclosure earthed through the metal body of the filtered IEC inlet i used. 

 I haven't experienced a ground loop but so far I've only used it with portable sources since enclosing it. A portable source that was plugged into it's charger, but i haven't plugged it into a normal wall-powered source. 

 I'm curious if there's anything i ought to do as a preventative measure, but, no trouble found so far.


----------



## runeight

Good question. Ground loops notwithstanding, I would first try tying the star directly to the enclosure along with the line/mains ground. I bet this will work under many, if not most, situations.

 If it doesn't, ground loop breakers should work.

 Of course, in theory, it doesn't really matter if the PS/Amps float because the headphones don't care about anything but the differential signal and the PS ground references the bias supplies to the rails.


----------



## ericj

If you have a number of different amps hooked up to a switchbox or preamp or something, it's possible that connecting signal ground to earth directly could cause a ground loop for another device on the same signal ground.


----------



## luvdunhill

Nelson Pass seems to have a creative way to handle this, using a NTC thermistor. I have starting putting a pair of thermistors in series with the primaries for 120VAC mains (and similarly a single between the two windings for 220VAC mains) as well as one from PS ground (in your case star ground) to the chassis at the same point where the IEC earth is connected.


----------



## sachu

In my proto build the chassis was tied to star ground without a ground loop breaker and it worked just great.


----------



## audionut

Alex, Looking at the BOM for hybrid, R30L, R20R, is that another misprint? Shouldn't R20R actually be R30R, and both should be the 68.1K values? Thanks, Tommy


----------



## luvdunhill

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_In my proto build the chassis was tied to star ground without a ground loop breaker and it worked just great._

 

sure, but not everyone has the same component chain as you do, that may or may not be susceptible to ground loops 
	

	
	
		
		

		
			





 Also, these sort of things are often great belt-and-suspenders additions, as they protect against all kinds of strange failure conditions.


----------



## runeight

Thanks. It is a misprint. Should be R30L, R30R. Both 68k.


----------



## sachu

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_sure, but not everyone has the same component chain as you do, that may or may not be susceptible to ground loops 
	

	
	
		
		

		
		
	


	




 Also, these sort of things are often great belt-and-suspenders additions, as they protect against all kinds of strange failure conditions._

 

Agreed..I did have to install a ground loop breaker for a CK2III i built a year ago.

 Btw, my proto worked fine in San Fransisco and also at the new owners place in Los Angeles with different sources in both occasions.
 Of course if someone's having problems they'll have the good sense to install it..not saying don't put one in.


----------



## BoilermakerFan

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_sure, but not everyone has the same component chain as you do, that may or may not be susceptible to ground loops 
	

	
	
		
		

		
		
	


	




 Also, these sort of things are often great belt-and-suspenders additions, as they protect against all kinds of strange failure conditions._

 

So if I already have the correct cap and resistor for them, no harm to the SQ would result with them installed, correct? I have enough parts for 4 amps, IIRC.


----------



## BoilermakerFan

I want to use a PowerCon connector for my power input, but I'd like to copy the filtering of the filtered IEC fused inputs. Is there a schematic to a good filter network with recommend parts spec'd?


----------



## runeight

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_So if I already have the correct cap and resistor for them, no harm to the SQ would result with them installed, correct? I have enough parts for 4 amps, IIRC._

 

Correct.


----------



## Emooze

I have these plans from back when I was looking into power filters. It uses pre-made AC filters you can get from Mouser and such.

http://www.hagtech.com/pdf/conditioner.pdf


----------



## sachu

Alex, a single Mills MRA-12 100k 12 watt resistor can be used instead of 3 x 33k 2 watt resistors right in place of R23-R25 and R26-R28? WOuld've used the MRA-5 if they were made in that value

 Also a single 120k 3 watt resistor to sub the R29 and R30?


----------



## runeight

You don't need 12W for the 100k resistor. 3W will do. The 33k are slightly over spec'd.

 120k will probably be alright unless something else is way out of whack.


----------



## luvdunhill

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I want to use a PowerCon connector for my power input, but I'd like to copy the filtering of the filtered IEC fused inputs. Is there a schematic to a good filter network with recommend parts spec'd?_

 

an across-the-line cap is usually sufficient. However, if you're looking for more, check out the Tangent's STEPS supply:

Single-voltage Tangent Easy Power Supply


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_You don't need 12W for the 100k resistor. 3W will do. The 33k are slightly over spec'd.

 120k will probably be alright unless something else is way out of whack._

 

yeah but PcX doesn't have that value in 5 watts..I guess I will just go with Kiwarne resistors that are rated at 5 watts then instead.


----------



## runeight

What about using 3 x CCF60 at 33.2k????


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_What about using 3 x CCF60 at 33.2k????_

 

Too late..already bought the 100k, 56k and 62k Kiwarnes with 100 ohm Rikens for R38 and R37


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_You don't need 12W for the 100k resistor. 3W will do. The 33k are slightly over spec'd.

 120k will probably be alright unless something else is way out of whack._

 

So the 100K is far too over spec'd? I went with the single 100K Mills. it was cheaper than (3) 5W Mills anyways.


----------



## BoilermakerFan

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_I also have these plans from back when I was looking into power filters. It uses pre-made AC filters you can get from Mouser and such.

http://www.hagtech.com/pdf/conditioner.pdf_

 

 Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_an across-the-line cap is usually sufficient. However, if you're looking for more, check out the Tangent's STEPS supply:

Single-voltage Tangent Easy Power Supply_

 

Thanks guys. I'll check those links out later. I'll limited depth at the power jack, but no real height restrictions, so the filtering and fuses will be on the jack or above it.


----------



## runeight

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_So the 100K is far too over spec'd? I went with the single 100K Mills. it was cheaper than (3) 5W Mills anyways._

 

100k 12W is about four times the amount of wattage actually needed. A 3W resistor will do for this spot. Or three 33k 1W resistors in series. I set them at 33k 2W very conservatively in the BoM.


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_100k 12W is about four times the amount of wattage actually needed. A 3W resistor will do for this spot. Or three 33k 1W resistors in series. I set them at 33k 2W very conservatively in the BoM._

 

I wasn't really worried about the power rating, more concerned about the 100K value being too high. I just want a Mills in there and that was the easiest and cheapest way to get it. PCX only has 27K 5W Mills and I didn't feel like trying to add a fourth in series...


----------



## runeight

Oh. 100k is ok. In fact it was the original value before I put the resistors in series.


----------



## Beefy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I just want a Mills in there_

 

Isn't using a wirewound resistor a really bad idea? Even though they say they are non-inductive, they would still be worse in this respect than an equivalent metal film.

  Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_yeah but PcX doesn't have that value in 5 watts..I guess I will just go with Kiwarne resistors that are rated at 5 watts then instead._

 

And a carbon film? Why? I just don't get it


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Isn't using a wirewound resistor a really bad idea? Even though they say they are non-inductive, they would still be worse in this respect than an equivalent metal film.



 And a carbon film? Why? I just don't get it 
	

	
	
		
		

		
		
	


	


_

 

The Mills is only for the B+, R23-R25 and R26-R28. A Riken is going in at R3/R4. The rest will be PRPs, but that's just my preference.


----------



## sachu

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_The Mills is only for the B+, R23-R25 and R26-R28. A Riken is going in at R3/R4, and Holcos as a possible sub for R31-R34. The rest will be PRPs, but that's just my preference._

 

I'd stay away from holcos..read reports of them failing at much lower voltages than what will be on the balance control. Apparently they are even rated at much lower voltage compared to even the RN55.


----------



## BoilermakerFan

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_I'd stay away from holcos..read reports of them failing at much lower voltages than what will be on the balance control. Apparently they are much lower voltage rating compared to even the RN55._

 

Thanks. I'll edit the above too. I'll use the Holcos in the phono stage.


----------



## runeight

Gents, I know that diyers like to tinker. And this is generally OK in low voltage amps, but here tinkering is not always good. Resistor voltage ratings are important as you know. HV offers a few more challenges than the average LV circuit. Just try to be thoughtful about the changes you are making.


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Gents, I know that diyers like to tinker. And this is generally OK in low voltage amps, but here tinkering is not always good. Resistor voltage ratings are important as you know. HV offers a few more challenges than the average LV circuit. Just try to be thoughtful about the changes you are making._

 






 I would have caught the voltage ratings on the Holcos as I triple check everything against the BOMs. The PRPs and Rikens either match or exceed the V-Ds. 

 Alex, I know you won't be surprised to hear this, but nothing in my house (built in '38) is stock, including my entire house's wiring which was upgraded in 2000.


----------



## audionut

Posted too quick


----------



## scompton

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_





 Alex, I know you won't be surprised to hear this, but nothing in my house (built in '38) is stock, including my entire house's wiring which was upgraded in 2000._

 

That probably wasn't cheap. Our house is the same age, but it's solid masonry, so it would be difficult to rewire the house.


----------



## runeight

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Posted too quick_

 

OK. How is it going?


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_OK. How is it going?_

 

Sorry, PS up and running but had a question. Adjusted P1 and P2 to set current, 360mV for + rail and 410mV for -. Left it running for about a minute and half to let stabilize. Both rails stabilized at about +/-300V. T1 and T3 measured +/- 367V. Are the T1,T3 measurements about right, and is a minute and a half long enough to let everything stabilize? I know you don't want to run this PS too long, as the load resistors will get plenty hot. Just wanted to know if anything else should be checked or readjusted. Thanks, Tommy


----------



## runeight

This is all good except the 367V. It is too high. Are you using the JX transformer?

 After about 10 mins the PS can be connected to the amps.


----------



## audionut

I'm using the 270CAX 250-0-250 @81ma. Don't have the amps built yet. Hope I'm not going to have to get another xfrm?


----------



## audionut

Also, my line voltage here at work runs almost 127VAC. I think my voltage at home is closer to 120VAC, but haven't checked it in awhile. Can check it this evening when I get home.


----------



## runeight

Well ........

 Q4 will drop 67V at 41mA. This is 2.7W. And this is probably too much for the heatsink that it is attached to. It will get very, very hot. You will have to monitor this.


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Well ........

 Q4 will drop 67V at 41mA. This is 2.7W. And this is probably too much for the heatsink that it is attached to. It will get very, very hot. You will have to monitor this._

 

I used my variac here at work and dropped line down to 121VAC, T1,T3 drops to 352V. Do you think the 269JX would change anything, as it has the same secondary rating, but has a 12mA less rating at 69 vs the one I have at 81mA? Mouser has the 269JX in stock and could have here tomorrow. Or, should I get amps built and hook up and monitor Q4?


----------



## runeight

You can probably run the amps for a while, while you keep an eye on Q3 and Q4.

 What is the HV secondary AC voltage?


----------



## audionut

At full line voltage here at work of 127VAC, secondary is 286VAC from CT to each leg. If I vary down to 121VAC, secondary is 273VAC from CT to each leg. Will go ahead and build amps and hook up. Exactly how should Q3,4 be monitored? Don't have a temp meter to check actual degrees. Also, the next smaller xfrm in the Hammond line is the 270AX, with a 480V C.T., 58mA, which would be below the spec for current specified. Hopefully, I can make this work, but really need to check my line voltage at home, which is where this amp will only be used.


----------



## runeight

Touch the heatsinks with your fingers quickly. If they are way too hot to touch then the devices are also running too hot.

 I'm sorry for this. We (meaning me) must have misunderstood the results from the proto builders when we upped the current requirements. This caused me to suggest using the 269JX to get a little extra voltage. But my latest build says that the 270AX can support this amp without difficulties in my house where 120VAC is very steady.

 Thus, the spec on the BoM may also be too high now. But, then we haven't heard from anyone yet who has really bad AC power.

 In general, however, we want T1/T3 to be around 320-335V if we can. This is what the heatsinks were set for.


----------



## Beefy

I'm also interested to hear from someone who tries a 3** series transformer. I suspect that they might put out a higher voltage than the equivalent 2** series......


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Touch the heatsinks with your fingers quickly. If they are way too hot to touch then the devices are also running too hot.

 I'm sorry for this. We (meaning me) must have misunderstood the results from the proto builders when we upped the current requirements. This caused me to suggest using the 269JX to get a little extra voltage. But my latest build says that the 270AX can support this amp without difficulties in my house where 120VAC is very steady.

 Thus, the spec on the BoM may also be too high now. But, then we haven't heard from anyone yet who has really bad AC power.

 In general, however, we want T1/T3 to be around 320-335V if we can. This is what the heatsinks were set for._

 

Alex, No problem. Just got home and checked my line voltage, is 122VAC. Will go ahead and build amps, then check heatsinks. I do know that when I left PS on for the minute and half while setting up current, Q3,4 heatsinks were barely warm. Really need to get amps built/hooked up, and then do like you said, and see if they are too hot to touch. Good news, if I ultimately need the 270AX, it's in stock right now. If you think I should just go ahead and get the 270AX, let me know and I'll order tomorrow. Will be off line for the next several hours. Will check back in around 8:00PM. Thanks.


----------



## BoilermakerFan

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_That probably wasn't cheap. Our house is the same age, but it's solid masonry, so it would be difficult to rewire the house._

 

It wasn't as bad as you think, only because my best friend is a journeyman electrician and I used to work for Cutler-Hammer so a distributor in MA sent me about $7K in gear because I closed a $500K/yr account for them when I was a trainee in the Boston Dist. office. I won the order on aesthetics: I made their product look cool as hell by custom painting two parts and using all black pushbuttons. 
	

	
	
		
		

		
			





 The house now has 200A service, 3 sub-panels (60A Lighting, 90A Kitchen, 60A Garage), all wiring up sized one gauge, and one receptacle circuit and one lighting circuit per room, except for dedicated circuits for the vacuum cleaner, PCs, audio equipment, and basement workbench 240Vac. My walls are 3/4" thick though, 3/8" drywall with 3/8" plaster skin, so it was not fun to cut in new boxes, but it's quiet!

 Edit: It's a Cape Cod with only 1,600sq. ft. above ground and another 500sq ft finished in the basement. I pulled Cat5 and quad-shield RG6 throughout the house too, commercial style phone and data distribution panel that supports 4 phone lines and 17 phone jacks. Data, Cable, and Phone were pulled out to the detached garage too. It was my hobby for 6 months before we moved in. Now jacks and wires are added slowly when I need them. Oh, the loadcenter also has power monitoring capabilities with Utility Grade Billing resolution. So I could buy my power over the internet from Washington State if Indiana was deregulated, but it's not...

 EDIT 2: Now back on topic...


----------



## Emooze

As an EE, this excites me. Nice job.


----------



## audionut

Alex, You have email


----------



## TimJo

So my parts arrived today, and one thing I noticed is that the KSC5042's (Q11 thru Q14) that are in the BOM for the hybrid are spec'd as 512-KSC5042FYDTU. These have the TO-220F casing with the collector pin y'd forward, rather than all three pins on the same plane.

 Should these really be called out as KSC5042FTU Fairchild Semiconductor Bipolar Transistors instead?


----------



## runeight

Good question. I thought that they all had the bent lead now. The fairchild datasheets always seem to show the inline leads but the parts always seem to come with bent leads. But maybe I didn't look hard enough??


----------



## runeight

Not only this, but the fairchild website now shows the KSC5042 as obsolete. There are alternatives, but I liked these the best.

 And there are still about 1100 of these in stock at mouser.


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Not only this, but the fairchild website now shows the KSC5042 as obsolete._

 

oh no! the horror of obsolete parts in an electrostatic amplifier! whatever will we do?


----------



## BoilermakerFan

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_oh no! the horror of obsolete parts in an electrostatic amplifier! whatever will we do?_

 

Might as well spec in the SJ74s and rework the R values to get the gain in line and have all obsolete, but better performing sand in there! 
	

	
	
		
		

		
			





 EDIT: Marc, did you receive my PM yesterday night?


----------



## luvdunhill

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Might as well spec in the SJ74s and rework the R values to get the gain in line and have all obsolete, but better performing sand in there! 
	

	
	
		
		

		
		
	


	




 EDIT: Marc, did you receive my PM yesterday night?_

 

Might as well do it right and use the 2SJ109 
	

	
	
		
		

		
		
	


	




 Yes I did, must search again for question marks..


----------



## studeb

If i want to use this amp downstream of a preamp, can i dispense with the input pot?


----------



## runeight

luvdunhill;6168306 said:
			
		

> Might as well do it right and use the 2SJ109
> 
> 
> 
> ...


----------



## runeight

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_If i want to use this amp downstream of a preamp, can i dispense with the input pot?_

 

Yes, but you might want to reduce the values of R1/R2 to 470k or even less. Most preamps expect to see a power amp Zi of 50k or so. Not that this matters in terms of impedance, but lowering the resistor value protects the input better if there are any small DC transients. When a vol pot is connected it takes care of this.


----------



## les_garten

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_oh no! the horror of obsolete parts in an electrostatic amplifier! whatever will we do?_

 

You should feel right at home!


----------



## luvdunhill

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_You should feel right at home!_

 

maybe Alex should do a Ge transistor amp for the ultimate in obsolete


----------



## runeight

But then I would be showing my age more than I do. Because you guys weren't alive when Ge transistors were first available commercially. I had to take a bus then the subway into downtown Phila when I was about 8 years old to go to the only store where I could buy Ge PNP transistors. You guys would have loved this place because it had boxes and boxes and boxes of surplus and new tubes. I used to buy them just to break them open to see how they were made. Nothing like some heavy metal dust to sharpen your brain.

 But the transistors, they were new and different and very hard to resist. 
	

	
	
		
		

		
		
	


	




 Not long after this surplus circuit boards showed up from military and other equipment. Lots of switching transistors to pull off and reuse.

 And, of course, I walked to school uphill both directions in 20F below zero weather through the snow and ice with 500lbs of books and no backpack.


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_But then I would be showing my age more than I do. Because you guys weren't alive when Ge transistors were first available commercially. I had to take a bus then the subway into downtown Phila when I was about 8 years old to go to the only store where I could buy Ge PNP transistors. You guys would have loved this place because it had boxes and boxes and boxes of surplus and new tubes. I used to buy them just to break them open to see how they were made. Nothing like some heavy metal dust to sharpen your brain.

 But the transistors, they were new and different and very hard to resist. 
	

	
	
		
		

		
		
	


	




 Not long after this surplus circuit boards showed up from military and other equipment. Lots of switching transistors to pull off and reuse.

 And, of course, I walked to school uphill both directions in 20F below zero weather through the snow and ice with 500lbs of books and no backpack._

 

500 pounds of books were actually called stone tablets back then...


----------



## Emooze

Post edited twice and removed because I am apparently way too tired to be making coherent posts.


----------



## MrMajestic2

Trying to figure out what to use as attenuator on this. I don't think I want a Blue Velvet. Maybe this would be a nice one:
Balance XLR 23 Stepped Attenuator Potentiometer 10K Log - eBay (item 290362457852 end time Nov-21-09 08:27:03 PST)


----------



## Beefy

I am planning on going all-out, and using a balanced PGA2320 based controller or a Joshua Tree.


----------



## MrMajestic2

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I am planning on going all-out, and using a balanced PGA2320 based controller or a Joshua Tree._

 

For once, I'm going to keep the cost down


----------



## TimJo

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Good question. I thought that they all had the bent lead now. The fairchild datasheets always seem to show the inline leads but the parts always seem to come with bent leads. But maybe I didn't look hard enough??_

 

 Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Not only this, but the fairchild website now shows the KSC5042 as obsolete. There are alternatives, but I liked these the best.

 And there are still about 1100 of these in stock at mouser._

 

Well, to be honest, with Mouser still stocking these, I'd say that's quite a few eXStatA's that can be built. 
	

	
	
		
		

		
		
	


	




 Poking around some more on the net, I did find some stuff on the Fairchild site, one of which saying that the technical drawings for the KSC5042F were TBD. 
	

	
	
		
		

		
		
	


	




 But, in another section there is a verbal description of the package, and it does seem to indicate that the YD part of the p/n indicates the bent pin version.

Customer Qualification Product Folder - Fairchild P/N KSC5042FTU - NPN Triple Diffused Planar Silicon Transistor

Customer Qualification Product Folder - Fairchild P/N KSC5042FYDTU - NPN Triple Diffused Planar Silicon Transistor

 One option that makes the most sense to me (provided you agree) may simply be to add a second solder pad for the collector based on the pinout of the bent pin variety, and then list both p/n's as alternatives. This way when the next run of boards are made, no matter which version someone buys from Mouser, they will just drop in. This may involve moving the -300/SG connectors on the outside of the boards slightly, but it probably can be done...


----------



## studeb

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_
 One option that makes the most sense to me <SNIP>, but it probably can be done..._

 

Can one not straighten the pins?


----------



## luvdunhill

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_This may involve moving the -300/SG connectors on the outside of the boards slightly, but it probably can be done..._

 

given runeight's signature.... why not just use a pair of pliers to fix the situation?


----------



## studeb

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_given runeight's signature.... why not just use a pair of pliers to fix the situation?_

 

i don't think pliers can move the pads, perhaps a dremel?


----------



## luvdunhill

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_i don't think pliers can move the pads, perhaps a dremel? 
	

	
	
		
		

		
		
	


	


_

 

the device legs are much more movable via pliers than the pads are, right?


----------



## Emooze

Well my parts are nearly all here, bent pins included. Shouldn't be a problem to bend them back carefully. Essentially just waiting on 600V wire.

 Now the question is whether my homework due tomorrow is more important than a night of soldering....


----------



## les_garten

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_Well my parts are nearly all here, bent pins included. Shouldn't be a problem to bend them back carefully. Essentially just waiting on 600V wire.

 Now the question is whether my homework due tomorrow is more important than a night of soldering...._

 

Emooze,
 Where'd you get your wire?


----------



## TimJo

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_Can one not straighten the pins?_

 

 Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_given runeight's signature.... why not just use a pair of pliers to fix the situation?_

 

Well, this _is_ the obvious solution. 
	

	
	
		
		

		
		
	


	




 I was just saying that since new boards are going to be made, rather than change parts (which was the direction things were drifting as a result of my original post), it seems like an alternative solution would be to add an extra pad, and then we can stick with the part that Alex already designed with. That's all...


----------



## scompton

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_Emooze,
 Where'd you get your wire?_

 

I bought mine from Apex Jr. I also found some here Watts Tube Audio ~ Everything Tube Amps!


----------



## les_garten

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_I bought mine from Apex Jr. I also found some here Watts Tube Audio ~ Everything Tube Amps!_

 

Thanx! Who's Apex Jr?


----------



## scompton

Probably 10 pages back, someone posted about them

Apex Jr.Home Page


----------



## les_garten

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_Probably 10 pages back, someone posted about them

Apex Jr.Home Page_

 

Heh, Yeah I remember now. Thanx!


----------



## Emooze

I ordered mine from Ebay but I'm gonna see if my school shop has some 600V wire I can use so I don't have to wait.


----------



## runeight

Transistor leads are easy to bend into alignment with the other leads. My vote is to stick with the plier solution.

 Thanks for all of you who have pushed the paypal button.

 How do you all like the black boards?


----------



## sachu

The boards look friggin great Alex. very nice


----------



## Emooze

I don't want to solder anything to them. That or I wish I bought all-black components.


----------



## les_garten

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_I don't want to solder anything to them. That or I wish I bought all-black components._

 

You'll be OK, just use Silver Solder!


----------



## BoilermakerFan

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_I don't want to solder anything to them. That or I wish I bought all-black components._

 

That's why I decided to use PRPs. They might sound a little better, they might not, but they'll look great on the board!


----------



## audionut

Gentlemen, got my hybrid up and running and listening to my ESP-950's as we speak. Yes, Alex, the boards look great
	

	
	
		
		

		
			





 Will be listening throughout the evening, and so far, I must say it's sounding every bit as good as my KGSS. Need to listen more, though, to get a better idea how they compare. Thanks to Alex for his email help on a few minor issues regarding oscillation and balancing. I believe he's going to recommend everyone ground the heatsinks from the get go as my hybrid also oscillated. Grounding heatsinks took care of problem. Alex will probably chim in here on the oscillation issue. Tommy.


----------



## les_garten

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Gentlemen, got my hybrid up and running and listening to my ESP-950's as we speak. Yes, Alex, the boards look great
	

	
	
		
		

		
		
	


	




 Will be listening throughout the evening, and so far, I must say it's sounding every bit as good as my KGSS. Need to listen more, though, to get a better idea how they compare. Thanks to Alex for his email help on a few minor issues regarding oscillation and balancing. I believe he's going to recommend everyone ground the heatsinks from the get go as my hybrid also oscillated. Grounding heatsinks took care of problem. Alex will probably chim in here on the oscillation issue. Tommy.
	

	
	
		
		

		
		
	


	


_

 

Sweet! We'll want to hear more about the KGSS comparison for sure.


----------



## sachu

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Gentlemen, got my hybrid up and running and listening to my ESP-950's as we speak. Yes, Alex, the boards look great
	

	
	
		
		

		
		
	


	




 Will be listening throughout the evening, and so far, I must say it's sounding every bit as good as my KGSS. Need to listen more, though, to get a better idea how they compare. Tommy.
	

	
	
		
		

		
		
	


	


_

 

Congrats Tommy..look forward to impressions as will many others.


----------



## TimJo

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Gentlemen, got my hybrid up and running and listening to my ESP-950's as we speak. Yes, Alex, the boards look great
	

	
	
		
		

		
		
	


	




 Will be listening throughout the evening, and so far, I must say it's sounding every bit as good as my KGSS. Need to listen more, though, to get a better idea how they compare. Thanks to Alex for his email help on a few minor issues regarding oscillation and balancing. I believe he's going to recommend everyone ground the heatsinks from the get go as my hybrid also oscillated. Grounding heatsinks took care of problem. Alex will probably chim in here on the oscillation issue. Tommy.
	

	
	
		
		

		
		
	


	


_

 

That great Tommy! 
	

	
	
		
		

		
		
	


	




 It seems then the build is straightforward and goes back to the notion that double checking your parts and their orientation is the key. 

 It makes sense about the grounding, and that's easy as well. When I was looking at the board last night, it did make we wonder about the EM radiation and if it was strong enough to jump channels, then what effect would it have on the tube sitting next to it. I know tubes are sensitive to RF interference, but what about EM interference?


----------



## smeggy

Wait, are the boards ready and waiting to get paid for? 

 I been too busy to keep track of what's going on....


----------



## Emooze

Grats on the build.

 Looks like mine will be a little bit longer, managed to order too few rectifiers.


----------



## runeight

Yes, I can breathe a bit of relief. 
	

	
	
		
		

		
		
	


	




 It's been great to work with Tommy on this build.

 I will look forward to everyone's impressions as the builds are made.

 As for the oscillation, everyone should plan to ground all of the CCS heatsinks. If you are concerned about the tubes you can ground the other four heatsinks near the tubes.

 The main remaining issue is the heat on Q3/Q4 in the PS. My apologies for the mixup in the communication about this during the proto phase. My fault.

 However, the bigger transformers are simply going to overheat these devices. I have sent Tommy a spare 270AX and I am pretty sure it will work without any problems.

 The rest of you will have to monitor the PS mosfets for power dissipation.

 Now the rest of you guys ........


----------



## runeight

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Wait, are the boards ready and waiting to get paid for? 

 I been too busy to keep track of what's going on...._

 

Yes, boards are ready. PM me your shipping address and I'll shoot everything to you.


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes, I can breathe a bit of relief. 
	

	
	
		
		

		
		
	


	




 It's been great to work with Tommy on this build.

 I will look forward to everyone's impressions as the builds are made.

 As for the oscillation, everyone should plan to ground all of the CCS heatsinks. If you are concerned about the tubes you can ground the other four heatsinks near the tubes.

 The main remaining issue is the heat on Q3/Q4 in the PS. My apologies for the mixup in the communication about this during the proto phase. My fault.

 However, the bigger transformers are simply going to overheat these devices. I have sent Tommy a spare 270AX and I am pretty sure it will work without any problems.

 The rest of you will have to monitor the PS mosfets for power dissipation.

 Now the rest of you guys ........ 
	

	
	
		
		

		
		
	


	


_

 

Likewise a pleasure working with Alex
	

	
	
		
		

		
		
	


	




 May have to start an Alex Cavalli apreciation thread, as someone else here did for Ti Kan here on head-fi
	

	
	
		
		

		
		
	


	




 Between Ti and Alex, don't think there's any better tech support for the great designs they come up with. Gosh, when I think of all the cash I've saved by building these great amps, vs buying a commercially built one, still amazes me! Some have said a great amp like the extata or B22, would probably go for north of 2 grand.
 Anyway, back to the build, I'm going to try and find access to a heat sensing device, to measure heat on Q3,4 in PS. If I can't find one, will be hooking up the 240-0-240 that I get tomorrow, and compare by touch how hot they get compared to the 250-0-250 xfmr that I have in there now. The jury's still out, but maybe we'll get lucky and still be able to use the 250-0-250 xfmr's that some have already purchased. Will leave that decision up to Alex after I've done the comparisons tomorrow evening
	

	
	
		
		

		
		
	


	




 Tommy


----------



## BoilermakerFan

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Likewise a pleasure working with Alex
	

	
	
		
		

		
		
	


	




 May have to start an Alex Cavalli apreciation thread, as someone else here did for Ti Kan here on head-fi
	

	
	
		
		

		
		
	


	




 Between Ti and Alex, don't think there's any better tech support for the great designs they come up with. Gosh, when I think of all the cash I've saved by building these great amps, vs buying a commercially built one, still amazes me! Some have said a great amp like the extata or B22, would probably go for north of 2 grand.
 Anyway, back to the build, I'm going to try and find access to a heat sensing device, to measure heat on Q3,4 in PS. If I can't find one, will be hooking up the 480-0-480 that I get tomorrow, and compare by touch how hot they get compared to the 500-0-500 xfmr that I have in there now. The jury's still out, but maybe we'll get lucky and still be able to use the 500-0-500 xfmr's that some have already purchased. Will leave that decision up to Alex after I've done the comparisons tomorrow evening
	

	
	
		
		

		
		
	


	




 Tommy_

 

Wow you're running a 1000VCT trafo? 
	

	
	
		
		

		
		
	


	




 My custom iron was three times more than the Hammond, or pretty close to that, so I'm running 500VCT, but I'll use 2-1/2" heatsinks to help with the heat, plus a little passive convection by vent location and ducting to bring in cool air to the base of the heat sinks. My chassis is pretty open on the bottom as well as the top, so I'll have enough air flow to keep things cool.


----------



## Emooze

By 480-0-480 and 500-0-500 I'm assuming you mean 240-0-240 and 250-0-250?

 Also, for those with the 2 triads, I just wire the 2 coils on each xfmr in series and then the 2 xfmrs in series again? And 22 AWG should be enough for the power lines, correct?


----------



## runeight

emooze, I have a Triad wiring diagram. I'll post it on the website.


----------



## runeight

Diagram posted. Look under INSTRUCTIONS. 

 Just like you said.


----------



## audionut

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Wow you're running a 1000VCT trafo? 
	

	
	
		
		

		
		
	


	




 My custom iron was three times more than the Hammond, or pretty close to that, so I'm running 500VCT, but I'll use 2-1/2" heatsinks to help with the heat, plus a little passive convection by vent location and ducting to bring in cool air to the base of the heat sinks. My chassis is pretty open on the bottom as well as the top, so I'll have enough air flow to keep things cool._

 

My bad, alright
	

	
	
		
		

		
		
	


	




 Guys, it's been a looooong day!! 500VCT or 250-0-250 is what's in there now (BOM spec). 480VCT or 240-0-240 is what I'll try tomorrow. Now that I've corrected myself, can I pleeeeze go to bed now?
	

	
	
		
		

		
		
	


	




 Damn, a 1000VCT would've really got the 4th of July off to an early start
	

	
	
		
		

		
		
	


	




 Oh, edited my huge xfmr post above, couldn't let that stand..!!


----------



## awpagan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes, I can breathe a bit of relief. 
	

	
	
		
		

		
			







 The rest of you will have to monitor the PS mosfets for power dissipation.

 Now the rest of you guys ........ 
	

	
	
		
		

		
		
	


	


_

 

found this http://tubedata.milbert.com/sheets/093/6/6S4A.pdf

 Is 6S4 the same as the 6S4A?

 600mA heater current.
 2.5 amp transformer with 4 Tubes cutting a bit close.

 how much extra power do we need to dissapate if using the 269JX?
 In my case I'll have to use the 369JX (240V primary) version as to import a tranny is not really worth it.
 cannot find a 370AX locally, only the 370X, but too lower voltage.

 Been looking for that PDF for a while now.


----------



## pertube

Fantastic thread I’m very impressed and like building my on Amp. Does everyone have a Layout for the Power supply – best as Eagle-File? Can’t find it in the thread….


----------



## runeight

Quote:


  Originally Posted by *awpagan* /img/forum/go_quote.gif 
_found this http://tubedata.milbert.com/sheets/093/6/6S4A.pdf

 Is 6S4 the same as the 6S4A?

 600mA heater current.
 2.5 amp transformer with 4 Tubes cutting a bit close.

 how much extra power do we need to dissapate if using the 269JX?
 In my case I'll have to use the 369JX (240V primary) version as to import a tranny is not really worth it.
 cannot find a 370AX locally, only the 370X, but too lower voltage.

 Been looking for that PDF for a while now._

 

Yes, they are effectively the same. I think a 2.5A secondary will be alright and will pull down to 6.3V or so. At least that's been the case with the proto builds so far.

 How much extra PD the JX adds depends on the actual line voltage. In my house it adds a bit more than 800mW per device.


----------



## awpagan

Runeight
 As far as Line voltages go...
 I go for a variable of approx 5 to 10%

 being 240vac down to 230vac or up to 250vac
 This doesn't happen here very often but you wouldn't want to switch on at an unfortunate time and pop the power supply.

 we could use a bit more "just in case" protection in the power supply.


----------



## runeight

If the voltage runs low the PS should be fine. If it runs high the mosfets will burn more power. With 2" heatsinks there is headroom. They'll just run hotter than I intended.

 At this point there is nothing else to be done to get "just in case" headroom except to use 2.5" heatsinks on the fets in the PS.

 In my rig here with 120V steady, the 269JX did not burn up the fets. It was just hotter than I wanted.

 I'll do a temp measurement this morning.


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_In my rig here with 120V steady, the 269JX did not burn up the fets. It was just hotter than I wanted._

 

Any further thought to my suggestion of running a 300V zener string instead of the default 291V to ease up the heat dissipation a bit?


----------



## runeight

Yes. Good idea. 
	

	
	
		
		

		
		
	


	




 But you'll have to pay attention to where all of the voltages come to. From the current builds we can guess that the actual voltage will be about 10-15V above the zener voltage. This puts you at 315V. The input to filter should be at least 15V above this. If the mains voltage stays high enough to maintain 330V at T1/T3 then you're good to do.

 And you'll squeak out a few more volts from the amp.


----------



## TimJo

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Can the whole thing run a bit higher than 300V to balance out the heat dissipation a bit?

 [EDIT] Just thinking that running 300V of zeners for 310V instead of 291V for 300V would balance it out easily enough._

 

 Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes, with the 269JX you could run higher rails. The amps won't mind an extra 15V or so._

 

I bought the 369JX, and my line voltage runs high, so do you think I should populate the PS with all 100 volt zeners right from the start, like Beefy suggested? I ordered extras just in case...

 Whoops - cross post. Question answered...


----------



## runeight

Yes, I think you should do that. Because, as you will see, once you get the PS fully built it's hard to get to these components. This is actually intentional to make it nearly imposible for you to touch the exposed leads of the tombstoned devices. 
	

	
	
		
		

		
		
	


	




 The sand amp boards have a similar design where the heatsinks protect the exposed leads. It wasn't possible to do quite as good a job on the tube boards.


----------



## TimJo

Thanks.

 It will be interesting to see where the voltages end up with the 300 series. I'm hoping the effect of my high line voltage will be less significant since the 300 series has both 110v and 120v taps, whereas the the 200 series is spec'd at 115v. I guess I'll know soon enough.


----------



## runeight

Some temp results using the 269JX. The input T1/T3 voltages are about 355VDC.

 I have a contact sensor and it's not quite as accurate as an IR sensor.

 Q3 runs at about 51C on the attachment screw.

 Q4 runs at about 48C on the attachment screw.

 All the rest of the devices are around 41C or less.

 50C is not death. Without actually doing the thermal calculations we can guess that on the plastic devices the junction temp is at least 10C higher. 60C at the junction is still less than half the 150C rating. For fets this should be ok.


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Transistor leads are easy to bend into alignment with the other leads. My vote is to stick with the plier solution.

 Thanks for all of you who have pushed the paypal button.

 How do you all like the black boards?_

 

I've been bending these pins since the very _first_ poor mans proto - without ill effect.

 The Black Boards are smashing!


----------



## TimJo

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Transistor leads are easy to bend into alignment with the other leads. My vote is to stick with the plier solution._

 

 Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I've been bending these pins since the very first poor mans proto - without ill effect._

 

Agreed. Sorry to have muddied the waters. I think it's too many years of engineering in a production environment - I need to remember this is a DIY project after all...


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Some temp results using the 269JX. The input T1/T3 voltages are about 355VDC.

 I have a contact sensor and it's not quite as accurate as an IR sensor.

 Q3 runs at about 51C on the attachment screw.

 Q4 runs at about 48C on the attachment screw.

 All the rest of the devices are around 41C or less.

 50C is not death. Without actually doing the thermal calculations we can guess that on the plastic devices the junction temp is at least 10C higher. 60C at the junction is still less than half the 150C rating. For fets this should be ok._

 

So, Alex, My T1,T3 volatages were running about the same as yours, 357VDC in my case. I'm still going to try and locate a temp measuring device, but based on what you're seeing temp wise, it's looking a little more promising for being able to use the 500VCT xfmr? I'm expecting the smaller one in today and will still compare tonight. Oh, my rails are running steady at -306DC and +305VDC.


----------



## runeight

I can't say for sure. My boards are not cased up so there is plenty of ventilation. What will happen in an enclosure depends, as you know.

 However, the 100V zener fix might just do the trick for everyone. Taking 15V off the fets will reduce their PD by around 600mW. This is a lot when the PD is 1.4W. We may be ok.

 But try the AX later and see what you get. If it works it is a better solution.


----------



## runeight

Another simple thing to do will be to install the power LED. This draws 5mA from the filter caps and will reduce the filter voltage even further.


----------



## Beefy

You know, all this talk might be a bit redundant...... J271 Fairchild Semiconductor JFETs

 The most troubling part is the 'On Order: 0'. So if somebody is placing a Mouser order, perhaps they could order some of these extra just to make sure Mouser has incoming stock?


----------



## runeight

Wow, the components which were plentiful when we started are dropping like flies.


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Another simple thing to do will be to install the power LED. This draws 5mA from the filter caps and will reduce the filter voltage even further._

 


 I haven't installed my PS LED, yet, cuz I hadn't planned on using it right off. I will go ahead and install it this evening, though, as I do have it.


----------



## runeight

It will only be a small adjustment, but everything helps.

 I have talked with Mouser. The J271 is a good selling product for them and they told me that they expect to continue with it until Fairchild makes it obsolete. Fairchild lists it as full production. But the jfet is also manuf by Vishay and I think one other manufacturer. Perhaps they will stay around for a while.

 I also asked about the KSC5042 since Fairchild is obsoleting it. They couldn't offer much help but I did suggest that they start carrying some of the Sanyo HV BJTs. The person I talked with actually took this request seriously because Mouser evidently wants to expand its line of semiconductors. We shall see. In the meantime the KSC5027 can sub directly for the KSC5042.


----------



## luvdunhill

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_You know, all this talk might be a bit redundant...... J271 Fairchild Semiconductor JFETs

 The most troubling part is the 'On Order: 0'. So if somebody is placing a Mouser order, perhaps they could order some of these extra just to make sure Mouser has incoming stock?_

 

SOT-23 anyone?

MMBFJ271 Fairchild Semiconductor MOSFETs

 Alex, that would be Siliconix, pre Vishay acquisition.


----------



## audionut

Alex, There's no place on PS board to put LED, correct? You just hook it up to termial strip at the L- and L+, anode to + and cathode to -?


----------



## runeight

Noooo, I won't do it. 
	

	
	
		
		

		
		
	


	




 Yes, thanks. Siliconix.


----------



## runeight

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Alex, There's no place on PS board to put LED, correct? You just hook it up to termial strip at the L- and L+, anode to + and cathode to -?_

 

Right. It's meant to provide power for a panel mount power indicator.


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Noooo, I won't do it. 
	

	
	
		
		

		
		
	


	


_

 

not too hard to get creative. Would require the elusive pliers and some scrap component leads though 
	

	
	
		
		

		
		
	


	




 I guess you could stick the layout on the bottom, but going up-hill both ways to school your whole life usually means adoption of the matra of not soldering anything one cannot see 
	

	
	
		
		

		
		
	


	




 In reality, I'm not sure how smart that would be, as surface mount JFETs might exhibit memory distortion:

lab page

 ... I've seen a few beginner builders squish TO-92 parts down so far that the leads weren't even visible to "shorten the signal path" to the input JFETs... perhaps not such a great idea


----------



## Beefy

So you suggest the legs are useful as mini heatsinks?


----------



## runeight

Thanks. Very interesting link. Nothing much that can be done about it either it would seem. 
	

	
	
		
		

		
		
	


	




 Let's wait on the jfet issue. They are still around and there are subs, although their gm is lower.


----------



## runeight

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_So you suggest the legs are useful as mini heatsinks?_

 

Actually, they are. I leave a fair amount of exposed leg on all the TO92 devices. (Now don't go there ...)


----------



## luvdunhill

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_So you suggest the legs are useful as mini heatsinks?_

 

yes, also, a 1-2oz copper board can transfer heat very well, especially with multiple big heat sinks directly coupled to it. One way you can help mitigate this is to raise all resistor bodies from the PCB (a very good idea anyways with HV) and to insulate the heat sinks from the boards using a fiber or nylon washer between the top of the PCB and heat sink itself. This also is a good idea to protect against the heat sink penetrating the solder mask in places it shouldn't.


----------



## spritzer

Marc's point of not relying on the solder mask to provide the necessary insulation is something every one who wants to build this amp should take to heart. Same goes for all other insulation present in the amp.


----------



## audionut

Haven't seen anyone mention this yet, but regarding the heatsink issue, I personally always use thermal heatsink compound (white) on any device mounted to a heatsink. Just a little extra precaution, and not sure how much it helps, but every little bit is worth it. Anyone else do this?


----------



## Beefy

In all of my projects, I have used the Aavid Thermalloy Thermasil pads as specified in the exstata BOM. They electrically isolate _and_ facilitate heat transfer.

 I wouldn't have thought thermal compound would offer any additional protection over these pads. Nor would I think that thermal compound would offer any protection on its own.


----------



## les_garten

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_In all of my projects, I have used the Aavid Thermalloy Thermasil pads as specified in the exstata BOM. They electrically isolate and facilitate heat transfer.

 I wouldn't have thought thermal compound would offer any additional protection over these pads. Nor would I think that thermal compound would offer any protection on its own._

 

I was wondering about this too. Thanx! Funny thing, when Apple came out with the first Intel MacBook Pros, they put too much thermal compound on the chips casuing them to overheat. Fix was to open them up and scrape the goop off, and apply a thin layer. An example of when MOAR is not always MO' better.


----------



## manaox2

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_In all of my projects, I have used the Aavid Thermalloy Thermasil pads as specified in the exstata BOM. They electrically isolate and facilitate heat transfer.

 I wouldn't have thought thermal compound would offer any additional protection over these pads. Nor would I think that thermal compound would offer any protection on its own._

 

I've seen people use the thermal compound where heatsinks meet an enclosure. That seems like it might help aid heat transfer. I wouldn't recommend doing that to board mounted heatsinks of course.

 And, yes, I learned way back that putting too much thermal compound can actually be a harmful thing.


----------



## audionut

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_I've seen people use the thermal compound where heatsinks meet an enclosure. That seems like it might help aid heat transfer. I wouldn't recommend doing that to board mounted heatsinks of course.

 And, yes, I learned way back that putting too much thermal compound can actually be a harmful thing._

 

Uhm, I've seen and replaced thousands of horizontal out xistors and regulator IC's that are mounted to heatsinks ON PC boards in televisions that I've repaired. These devices all came stock with thermal compound from the individual manufacturer, so putting it on board mounted heatsinks is no problem. Whether or not you choose or believe in using it, is an individual choice. Not talking about gobbing it on, just a small dab to barely cover surface of device. I personally don't think major TV manufacturers would have used it for nothing IMHO


----------



## ericj

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_In all of my projects, I have used the Aavid Thermalloy Thermasil pads as specified in the exstata BOM. They electrically isolate and facilitate heat transfer.

 I wouldn't have thought thermal compound would offer any additional protection over these pads. Nor would I think that thermal compound would offer any protection on its own._

 

On the transistors with metal backs I used berquist wax/fabric pads because i have dozens of them. They work well but since they're wax-based they are necessarily not reusable when replacing a transistor, while the silicone pads are reusable. 

 I don't think the addition of paste would improve thermal transfer for people using silicone or wax pads. It's likely to make it worse. 

 If you're using mica pads, it might help if you add a vanishingly small amount, because mica doesn't form to the parts the way wax or silicone would. The white zinc-based pastes don't conduct at low voltages but at 300v it would make me worry, so I'd recommend a nonmetallic paste, or just straight up pure silicone grease. 

 On parts with a full plastic package, there's no need for an insulating pad, but you still need a good thermal interface. Use silpads or wax pads if you've got 'em, or use any thermal compound (judiciously applied of course). I used Arctic Silver 5 on the plastic parts because i bought a couple grams of it like eight years ago and i still have some.


----------



## les_garten

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Uhm, I've seen and replaced thousands of horizontal out xistors and regulator IC's that are mounted to heatsinks ON PC boards in televisions that I've repaired. These devices all came stock with thermal compound from the individual manufacturer, so putting it on board mounted heatsinks is no problem. Whether or not you choose or believe in using it, is an individual choice. Not talking about gobbing it on, just a small dab to barely cover surface of device. I personally don't think major TV manufacturers would have used it for nothing IMHO
	

	
	
		
		

		
		
	


	


_

 

I certainly didn't mean you would slop it on, sorry if you took it that way. 
 Let me clarify. Sometimes combining 2 methods to accomplish a task makes both methods less than optimal. In the kits there is a dialectric layer, maybe Mica. I don't know. Adding the thermal grease to the mica might hurt, might help, might not make any difference at all. You would hate it if it hurt heat transfer though.


----------



## les_garten

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_On the transistors with metal backs I used berquist wax/fabric pads because i have dozens of them. They work well but since they're wax-based they are necessarily not reusable when replacing a transistor, while the silicone pads are reusable. 

 I don't think the addition of paste would improve thermal transfer for people using silicone or wax pads. It's likely to make it worse. 

 If you're using mica pads, it might help if you add a vanishingly small amount, because mica doesn't form to the parts the way wax or silicone would. The white zinc-based pastes don't conduct at low voltages but at 300v it would make me worry, so I'd recommend a nonmetallic paste, or just straight up pure silicone grease. 

 On parts with a full plastic package, there's no need for an insulating pad, but you still need a good thermal interface. Use silpads or wax pads if you've got 'em, or use any thermal compound (judiciously applied of course). I used Arctic Silver 5 on the plastic parts because i bought a couple grams of it like eight years ago and i still have some._

 

Thanx! The differences at higher voltages is something to keep in mind.


----------



## manaox2

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Uhm, I've seen and replaced thousands of horizontal out xistors and regulator IC's that are mounted to heatsinks ON PC boards in televisions that I've repaired. These devices all came stock with thermal compound from the individual manufacturer, so putting it on board mounted heatsinks is no problem. Whether or not you choose or believe in using it, is an individual choice. Not talking about gobbing it on, just a small dab to barely cover surface of device. I personally don't think major TV manufacturers would have used it for nothing IMHO
	

	
	
		
		

		
		
	


	


_

 

I meant on the bottom of the heatsink, that is going to be placed near the solder mask. I was referring that some people do that for heatsinks mounted on enclosures. I use it on Mica pads and I would expect someone to use it on components like a CPU, that is why it was created I believe.


----------



## Pyriel0

You guys could give this a shot on the heatsinks. 
Newegg.com - Arctic Silver Ceramique Thermal Compound - Thermal Compound / Grease
 I have used it on computer components and it has always worked well. The ceramique type is not supposed to conduct electricity. When I used it on my motherboards cooler, I just put a little on the bottom of the heatsinks and spread it around with my finger inside of a ziplock bag. Then screwed the thing back onto the board.


----------



## Beefy

There's a difference between not conducting electricity, and being able to withstand 300V......


----------



## Pyriel0

From the main website:
 Thermal Conductance:
 >200,000W/m2.°C (0.001 inch layer) 

 I guess someone could figure it out for approx 1/2 by 1/2 inch area but you would have to know the voltage and current going through the piece too. Was just throwing it out there.

 Edit: The m2 is m squared. It just didn't copy/paste right.


----------



## Coreyk78

Man, I haven't been to the old house for a couple of days so the boards are probably waiting for me, I can't wait to get there and pick them up. 

 One side benefit of moving is that you find a bunch of stuff that you don't want anymore. I sold a bunch of crap on craigslist Wednesday and had enough mad money that I ordered a pair of SR-404 Signature today 
	

	
	
		
		

		
		
	


	




 I won't have anything to listen to them with until I build the exstata, how's that for motivation?


----------



## wiatrob

Alex and I covered the Thermalsil issue when we were doing early boms (Alex was initially suspicious of these little grey mystery slabs). 

 They will protect you far better than misapplied thermal compound every time. And they're pretty good insulators...


----------



## Beefy

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_They will protect you far better than misapplied thermal compound every time. And they're pretty good insulators..._

 

My point exactly. The right tool for the job, and the simplest tool for the job.


----------



## runeight

Hmmmm. Several thoughts for what they are worth.

 1. You shouldn't have to worry about the mask standing off voltages. You may remember that Marc suggested some routing changes a while back and I went through all boards checking trace spacing and ensuring that there are no top layer traces under the heatsinks. The heatsinks have no pads so there is little risk that they will conduct to anything on the board. There are no ground planes either topside or bottomside because of the HV everywhere.

 2. For the plastic devices, they are obviously packaged to standoff their maximum voltages plus some. The KSCs are not going to arc between their internal devices and the heatsink. Thus, the only thing that is required is good thermal contact either with grease or a pad. Beyond this it's someone's choice what to do. But because the devices are plastic they need the best possible thermal path to the heatsink.

 3. Standard mounting should be used for devices with metal tabs. Shoulder washer and insulating pad. However, with the heatsinks floating is no voltage differential between the heatsink and the device anyway. One reason for doing it this way.

 4. The CCS heatsinks must be grounded but they have only plastic devices. No risk of voltage arcing there.

 5. I cannot assert unequivocally that no one will ever have an arcing problem on these boards. But I don't think you will based on what I know and based on using some industry-wide guidelines for trace spacing.

 6. Incidentally, these guidelines take into account the use of polymer masks and the trace spacing, IIRC, can be closer when there is a mask.

 7. There is no reason for anyone to have to depend on masks to prevent arcing since this is already built into the board design. Just put the components in the way they are supposed to go.


----------



## runeight

Number 8: the main thing you all need to be careful about is that you don't create solder blobs that are larger than the pads and which decrease the pad-to-pad spacing, particularly on the HV devices where there will be many hundreds of volts between a pair of pads on the same device.


----------



## ericj

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_There's a difference between not conducting electricity, and being able to withstand 300V......_

 

Yes, the arctic ceramica is nonconductive, but it's not going to provide insulation between metal parts because it's not going to prevent metal-to-metal contact the way that an insulating pad will.


----------



## studeb

it seems that this heat dissapation issue only came up for people building the hybrid amp. Something about the transformer used, right?
 Am i correct in assuming that this is less of an issue for the sand amp?


----------



## sachu

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_it seems that this heat dissapation issue only came up for people building the hybrid amp. Something about the transformer used, right?
 Am i correct in assuming that this is less of an issue for the sand amp?_

 

Only if you are using the Triad transformers for your sand amp or the hammond 270AX.


----------



## runeight

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_it seems that this heat dissapation issue only came up for people building the hybrid amp. Something about the transformer used, right?
 Am i correct in assuming that this is less of an issue for the sand amp?_

 

It is, as Sachu notes, the same for both versions. But let's see what the rest of you get.


----------



## Coreyk78

My boards were waiting for me today, they look very nice
	

	
	
		
		

		
		
	


	




 I'm still waiting on my potentiometer from china and my headphone jack from woo audio and I _should_ have all the parts.

 1/2" standoffs should give plenty of distance between the bottom of the board and the case I would think right? I have some longer standoffs on hand too, but they are a lot longer.


----------



## runeight

1/2" is plenty.

 I see that a lot of you guys have gotten your boards. I'm looking forward to the pics and the impressions. 
	

	
	
		
		

		
		
	


	




 Thanks again to all of you for being on the team.


----------



## pabbi1

Well, well, my long missing matched quad of sj74 showed up today from Taiwan - posted on 8-19-09... oh, and listening to the sand version of the amp, but need to issue a warning. DO NOT use a Sun enclosure with the Triads - it is the case that hums, and I cannot dampen it for squat.

 That said, mechanical noise is a non-factor when listening to the amp. But, about to ship this one off, and retrofit the Hybrid.

 There are still some tubes left - four matched pairs (and a spare), and about 20 singles.

 Oh, and since I have the coming week off, with NO visitors, and I'm off my (wife enforced) DIY "time-out", maybe I can get ONE of the other stat designs up and running for some honest comparisons.

 Hope to hear some impressions, and not just the euphoric "Hey, it works!" variety, especially since these impressions will be done in familiar confines (not meet conditions), with your source, your music, your biosphere.


----------



## ericj

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Well, well, my long missing matched quad of sj74 showed up today from Taiwan - posted on 8-19-09... oh, and listening to the sand version of the amp, but need to issue a warning. DO NOT use a Sun enclosure with the Triads - it is the case that hums, and I cannot dampen it for squat.

 That said, mechanical noise is a non-factor when listening to the amp. But, about to ship this one off, and retrofit the Hybrid._

 

My sand amp had a slight vibration issue at first, but the transformers just weren't well bolted down.


----------



## pabbi1

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_My sand amp had a slight vibration issue at first, but the transformers just weren't well bolted down._

 

Yep, she's dead quiet - with the top off. The thin metal shielding that is snapped against the vinyl is the real culprit, but, the vibration is the top lid against the bottom tray. A 12" Stanley clamp takes care of it, but, somewhat less than visually appealing. In any event, it has NO sonic impact whatsoever.

 Can't wait to hear the CCS version, though the proto builds are getting lots of play in the interim. Switched back to the hybrid, and just enjoying. It is a REALLY fun amp, and sometimes quite startling in it's honesty.

 Anyone else close on the build?


----------



## studeb

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_
 Anyone else close on the build?_

 

i got a big ol box'o'stuff from mouser today
 busy sorting, deal with reality, then maybe fun can begin

 so not really close


----------



## TimJo

Well, I got the power supply finished tonight. 
	

	
	
		
		

		
		
	


	




 Wow Alex, the black boards really make the components pop out. The red, green, and blue all look great against the solder mask.

 I didn't power it up yet, I'm going to wait till tomorrow. I'll post the voltage measurements as soon as I do.


----------



## Lou Erickson

I've got projects defined at Mouser and have got everything in the parts lists or sensible replacements for the few things that had gone out of stock... except for the J271's.

 I know enough to find a replacement for a resistor or a capacitor, but not about the transistors.

 I've searched the internet and discovered that Digi-Key and Newark both list this as a non-stock item. Mouser shows none on hand and none ordered.

 Can anyone help find an equivalent? Or should I just file the Mouser order and hope they get more?


----------



## Beefy

Quote:


  Originally Posted by *Lou Erickson* /img/forum/go_quote.gif 
_I know enough to find a replacement for a resistor or a capacitor, but not about the transistors._

 

 Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Might as well spec in the SJ74s and rework the R values to get the gain in line and have all obsolete, but better performing sand in there! 
	

	
	
		
		

		
		
	


	


_

 

In light of the J271 shortage, does BoilermakerFan's suggestion start making a bit more sense? At least until Mouser has the J271 again?

 [EDIT] Oh, and FWIW, Mouser has ordered 1964 of the J271. No ETA yet.


----------



## sachu

I ended up ordering a pair of quad matched J74s though i think i have two more quad matched J271s to pick from if need be. Waiting for parts from mouser..probably be here on tuesday/wednesday. 
 Digikey parts with the panasonic metal oxide resistors to sub the 3 x 33k resistors and 56k , 62k resistors are here already.

 edit: bah forgot about the parts from pcx..its gona be a while before that thing gets to me.


----------



## BoilermakerFan

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_
 edit: bah forgot about the parts from pcx..its gona be a while before that thing gets to me._

 

Not too long I hope. Except that I'm out of the office Nov. 30 until Dec. 4.


----------



## luvdunhill

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Oh, and FWIW, Mouser has ordered 1964 of the J271. No ETA yet._

 

I'd wager 8 weeks. Also, it's very likely they ordered 2,000 and someone has a backorder for (2000-1964). If you guys can find the Vishay parts, I've found that on average they have a higher Idss, compared to the average 7-8mA @ 12V of the Fairchild parts.


----------



## runeight

Not to set off a gold rush. I have all the quads necessary for the original sign up. There is one builder who has not checked in yet.

 But, I have managed to get 3 quads from the 20 jfets I just bought plus a few that I had from before.

 Let me know if you would like one. I'd like to ensure that all of the beta builders get a set first.


----------



## runeight

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Well, I got the power supply finished tonight. 
	

	
	
		
		

		
			





 Wow Alex, the black boards really make the components pop out. The red, green, and blue all look great against the solder mask.

 I didn't power it up yet, I'm going to wait till tomorrow. I'll post the voltage measurements as soon as I do._

 

I'm waiting for audionut to post some preliminary review information. I think it will be good. 

 But, maybe you'll have some results sooner.


----------



## audionut

Gentlemen, I've had a chance to listen to my hyrid extata this weekend, and so far, my initial impression is that it's definitely on par with my KGSS!
	

	
	
		
		

		
		
	


	




 First off, my headphones are the ESP-950's that I got last year at Christmas, source is an Onkyo DX-7555 component CD player, and I use the pre-amp out of my older JVC RX-8040.
 Why I wanted the hybrid, is I felt the ESP's were somewhat lacking in over all bottom end. Lows were good and clean, but just didn't seem to have the full, warm, deep bass that tubes seem to have. The ESP's are somewhat known for lacking in the bass region, especially with the crappy stock E90 energizer. With the KGSS, the bass definitely improved, but I had started feeding my CD player through my Bijou, which definitely gave me the bass I was missing with just the KGSS. Again, I think it's just more my preference for tubes in the bass region, and not the KGSS.
 Now, to the extata. It definitely achieved the low end I was looking for, without having to have the Bijou in the chain. The bass is very full, warm, and VERY clean and detailed. No muddy sound at all. As far as the mids and highs go, they are the equal to the KGSS in every way, and may actually surpass it in some. Haven't listened long enough to determine. The ESP's have the most air around instruments and best soundstage I've heard so far. They are very detailed, and every instrument is easily seperated and not all blended together. However, the extata/ESP combo is not so analytical that it becomes fatiguing, it's just a fun combo that has you not wanting to stop listining. As dead tired as I was last night, I said to myself I'm only going to listen for about an hour. Three hours later, I finally tore them off my head
	

	
	
		
		

		
		
	


	



 In closing, sorry I don't describe sound in "proper audiophile terminolgy", I'm from South Texas for cryin' out loud
	

	
	
		
		

		
		
	


	




 However, if you're wondering whether to build this amp and how it compares to one of the other top DIY (KGSS) amps, then put your worries aside and build this thing! Not only is it on par with the KGSS, it's considerably cheaper (not quality wise) and much easier to build (especially P2P, which I did on my KGSS) than the KGSS. Alex really has a winner here and finally there's an alternitive to the KGSS
	

	
	
		
		

		
		
	


	




 I do believe that Ericj's goals and dream have been achieved, and then some


----------



## manaox2

Darn you.


----------



## les_garten

@Audionut Thanx! Nice compare!


----------



## studeb

i have the PS built, and will power it up this evening if i have time
 Some notes about the build:

 There are no R9 and R10 on the board.
 Put the LEDs in before you put the transistors in.
 My heatsinks for Q4 touches the Q7/Q8 heatsink, have to adjust that.
 Maybe put C3 and C4 in after you have the heatsinks in place, it is easier to screw them down without the big caps in the way.
 Also with the screw heads on the inside of the board, the ends of the screws touch C3 and C4
 The rest was pretty straightforward.

 Not sure if i will get the amps built before the long weekend.


----------



## studeb

When powering up the PS how long is too long with the dummy loads in place?


----------



## BoilermakerFan

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Gentlemen, I've had a chance to listen to my hyrid extata this weekend, and so far, my initial impression is that it's definitely on par with my KGSS!
	

	
	
		
		

		
		
	


	




 First off, my headphones are the ESP-950's that I got last year at Christmas, source is an Onkyo DX-7555 component CD player, and I use the pre-amp out of my older JVC RX-8040.
 Why I wanted the hybrid, is I felt the ESP's were somewhat lacking in over all bottom end. Lows were good and clean, but just didn't seem to have the full, warm, deep bass that tubes seem to have. The ESP's are somewhat known for lacking in the bass region, especially with the crappy stock E90 energizer. With the KGSS, the bass definitely improved, but I had started feeding my CD player through my Bijou, which definitely gave me the bass I was missing with just the KGSS. Again, I think it's just more my preference for tubes in the bass region, and not the KGSS.
 Now, to the extata. It definitely achieved the low end I was looking for, without having to have the Bijou in the chain. The bass is very full, warm, and VERY clean and detailed. No muddy sound at all. As far as the mids and highs go, they are the equal to the KGSS in every way, and may actually surpass it in some. Haven't listened long enough to determine. The ESP's have the most air around instruments and best soundstage I've heard so far. They are very detailed, and every instrument is easily seperated and not all blended together. However, the extata/ESP combo is not so analytical that it becomes fatiguing, it's just a fun combo that has you not wanting to stop listining. As dead tired as I was last night, I said to myself I'm only going to listen for about an hour. Three hours later, I finally tore them off my head
	

	
	
		
		

		
		
	


	



 In closing, sorry I don't describe sound in "proper audiophile terminolgy", I'm from South Texas for cryin' out loud
	

	
	
		
		

		
		
	


	




 However, if you're wondering whether to build this amp and how it compares to one of the other top DIY (KGSS) amps, then put your worries aside and build this thing! Not only is it on par with the KGSS, it's considerably cheaper (not quality wise) and much easier to build (especially P2P, which I did on my KGSS) than the KGSS. Alex really has a winner here and finally there's an alternitive to the KGSS
	

	
	
		
		

		
		
	


	




 I do believe that Ericj's goals and dream have been achieved, and then some
	

	
	
		
		

		
		
	


	


_

 

Whoah. You think the ESP/950s lack bass? I've always been told the only 'stats that have bass are the 950s and O2s. Also been told the limiting factors on the 950s are the E/90 and the crappy pads. I plan to build a custom pair of 950s with JMoney HE90 pads on a custom cup for the 950 driver with a Stax cable in my custom headband design. So, in the end, I'll only be using the actual driver, but, well, I do that a lot with my headphones... 

 Glad to hear your impressions though and I'm glad I spent the bucks on the custom iron for my Hybrid. Planning to run a few 'trets off it too, so the extra bass will definitely help.


----------



## runeight

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_When powering up the PS how long is too long with the dummy loads in place?_

 

Actually, the website needs to be corrected. You power on as long as you want with the loads connected.


----------



## audionut

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Whoah. You think the ESP/950s lack bass? I've always been told the only 'stats that have bass are the 950s and O2s. Also been told the limiting factors on the 950s are the E/90 and the crappy pads. I plan to build a custom pair of 950s with JMoney HE90 pads on a custom cup for the 950 driver with a Stax cable in my custom headband design. So, in the end, I'll only be using the actual driver, but, well, I do that a lot with my headphones... 

 Glad to hear your impressions though and I'm glad I spent the bucks on the custom iron for my Hybrid. Planning to run a few 'trets off it too, so the extra bass will definitely help._

 

Something I should have stated is my other top rig is a 3 channel B22 with Denon AHD-5000, which, have the best bass I've ever heard. Unfortunately, I've never heard any Stax, but would like to. I've also heard the same thing, that in the Stat world, the 950's do have great bass compared to most. Again, I don't know, because I've never heard anything other than the Koss. Hope people won't misunderstand, the Koss have great bass, but when compared to my other setup, they lack a bit. Still a fantastic listen. I go back and forth on my two rigs, and it's somewhat not a fair comparison. They're both fantastic and fun to listen to in there own way. I've often said that if I could have the perfect sounding headphone, it would have the low end of the Denons and mids/highs of the Koss. Oh, well, that's what makes this hobby so fun! Variety is very much the spice of life


----------



## BoilermakerFan

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Something I should have stated is my other top rig is a 3 channel B22 with Denon AHD-5000, which, have the best bass I've ever heard. Unfortunately, I've never heard any Stax, but would like to. I've also heard the same thing, that in the Stat world, the 950's do have great bass compared to most. Again, I don't know, because I've never heard anything other than the Koss. Hope people won't misunderstand, the Koss have great bass, but when compared to my other setup, they lack a bit. Still a fantastic listen. I go back and forth on my two rigs, and it's somewhat not a fair comparison. They're both fantastic and fun to listen to in there own way. I've often said that if I could have the perfect sounding headphone, it would have the low end of the Denons and mids/highs of the Koss. Oh, well, that's what makes this hobby so fun! Variety is very much the spice of life
	

	
	
		
		

		
		
	


	


_

 

LOL! I figured you were a basshead, but you left that key bit of info out. 
	

	
	
		
		

		
		
	


	




 It's ok, I was told I'm a basshead too, but I never realized it, especially since I thought my K240 Sexttet MPs had a little too much bass before I swapped pads. Off the E/90 I thought the 950 lacked bass I was very disappointed. The E/90s short comings and the leaking pads of the 950s have given me hope that I can customize them and bend them to my needs.


----------



## ericj

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Actually, the website needs to be corrected. You power on as long as you want with the loads connected._

 


 Well, I did partially melt the insulation on one of my alligator clips, that i left clipped to the center (ground).


----------



## runeight

Ah yes, good point. The loads get blisteringly hot. I melted my test leads too when I left them attached.

 I should probably put this on the website.

 So do we have two more power supplies working now??? TimJo and Studeb??


----------



## audionut

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_LOL! I figured you were a basshead, but you left that key bit of info out. 
	

	
	
		
		

		
			





 It's ok, I was told I'm a basshead too, but I never realized it, especially since I thought my K240 Sexttet MPs had a little too much bass before I swapped pads. Off the E/90 I thought the 950 lacked bass I was very disappointed. The E/90s short comings and the leaking pads of the 950s have given me hope that I can customize them and bend them to my needs. 
	

	
	
		
		

		
		
	


	


_

 

Well, don't think I'd consider myself a basshead for liking the low end of the Denons, but that sorta depends on how one defines basshead
	

	
	
		
		

		
		
	


	




 To me, basshead is someone who cranks up an eq on the low end 12dB or listens to headphones with their 12" sub on. Please, no one flame me if that's the way you listen
	

	
	
		
		

		
		
	


	




 Honestly, how anyone listens is ok, and as long is YOU like it, is all that matters.
	

	
	
		
		

		
		
	


	




 Hey BoilermakerFan, have you had a chance to hear the Denons with a good amp and no bass boost? In this particular section of Head-Fi (DIY), I don't see many posting on the Denon's and just sorta wonder what you or anyone else thinks of their overall sound. They are by far my favorite set of dynamics I've heard, including my Senn HD-650's, or my Sony SA-5000's that I sold.


----------



## Coreyk78

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_i have the PS built, and will power it up this evening if i have time
 Some notes about the build:

 There are no R9 and R10 on the board._

 

Haha, I stared at the board for about 20 minutes last night trying to find those on the board before I pulled up the schematic and saw they don't exist.

 I finished stuffing my power supply and amp boards tonight, I'm going to set up the ps tomorrow.


----------



## pabbi1

The he60 have excellent bass as well, but only through a good amp (meaning NOT a hev70). It is clear, deep and has a fully extended soundstage on the eXStata.


----------



## runeight

Yes, R10/R11 are kind of a reverse easter egg. Something for you guys to discover that is NOT there.


----------



## BoilermakerFan

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_<snip>Hey BoilermakerFan, have you had a chance to hear the Denons with a good amp and no bass boost? In this particular section of Head-Fi (DIY), I don't see many posting on the Denon's and just sorta wonder what you or anyone else thinks of their overall sound. They are by far my favorite set of dynamics I've heard, including my Senn HD-650's, or my Sony SA-5000's that I sold._

 

No, I haven't. I do not use any bass boost, always a flat signal though I try to tune my orthos to have the sound sig and strong bass I want with a flat signal. I only have my C710s, but they have the Denon sound sig and really nice bass for a portable. So much so my quest for a portable amp and Sony X upgrade ended. They're perfect with my Sony A816 and it's just too small and convenient to carry anything else. If only the Sony played FLACs, then I would upgrade to the X for the 32Gig of space. In due time I'll upgrade, but no rush now. 

  Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_The he60 have excellent bass as well, but only through a good amp (meaning NOT a hev70). It is clear, deep and has a fully extended soundstage on the eXStata._

 

I'll get to hear a set of custom HE60s on the eXStata after I build them. HE60s will actually be similar to the 950 build, HE90 pads, custom wood cups, Stax cable, custom headband... I have permission from the owner to bring them to CanJam too.


----------



## manaox2

Is anyone planning on testing these with the O2 with the new protos currently?


----------



## les_garten

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Well, don't think I'd consider myself a basshead for liking the low end of the Denons, but that sorta depends on how one defines basshead
	

	
	
		
		

		
		
	


	




 To me, basshead is someone who cranks up an eq on the low end 12dB or listens to headphones with their 12" sub on. Please, no one flame me if that's the way you listen
	

	
	
		
		

		
		
	


	




 Honestly, how anyone listens is ok, and as long is YOU like it, is all that matters.
	

	
	
		
		

		
		
	


	




 Hey BoilermakerFan, have you had a chance to hear the Denons with a good amp and no bass boost? In this particular section of Head-Fi (DIY), I don't see many posting on the Denon's and just sorta wonder what you or anyone else thinks of their overall sound. They are by far my favorite set of dynamics I've heard, including my Senn HD-650's, or my Sony SA-5000's that I sold._

 

Man, after what you said about the D5000s puts the mark of the "B" on your forehead. Wear it proudly!


----------



## studeb

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_
 So do we have two more power supplies working now??? TimJo and Studeb??_

 

i am not sure i can get it powered up tonite, but in the mean time some pics may help.


----------



## studeb

some more


----------



## studeb

last ones


----------



## sergery

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_The he60 have excellent bass as well, but only through a good amp (meaning NOT a hev70). It is clear, deep and has a fully extended soundstage on the eXStata._

 

I would love to find a pair of these for close to what they retailed... By reputation these sound like the stats for me, probably try to make the next canjam to hear them.
  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes, R10/R11 are kind of a reverse easter egg. Something for you guys to discover that is NOT there. 
	

	
	
		
		

		
		
	


	


_

 

Yes I looked at the schematic for quite some time making sure I was not losing it 
	

	
	
		
		

		
		
	


	






  Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_Man, after what you said about the D5000s puts the mark of the "B" on your forehead. Wear it proudly!_

 

agreed
	

	
	
		
		

		
		
	


	




 Me? I am finished with stuffing the PS. I will test tomorrow after I have thoroughly checked it over - this last week was exhausting and I am taking this high voltage seriously and slowly. I also finished most of my case prep. The amp I will begin tomorrow/tuesday with an goal of for mid-week. My last couple of parts should arrive then anyhow.

 I hope everyone else is doing ok.
	

	
	
		
		

		
		
	


	




 cheers,
 serge


----------



## Lou Erickson

Found the J271's!

 Fairchild will sell them directly. Power Management ICs, Power Semiconductors, Signal Path ICs, Lighting and Display, Logic, Optoelectronics, Fairchild Semiconductor - Global Leader in Power Optimization of all places. Farnell (Farnell / Electronic Component Distributors / Suppliers / Electronics, Electrical Parts, Electrical Components and Wholesale Electronics.) also apparently had them in stock, but wanted to do everything in pounds sterling.

 With that, I pushed the button on my Mouser order and parts will come. Everything in stock and headed my way. Yay!


----------



## wiatrob

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Is anyone planning on testing these with the O2 with the new protos currently?_

 

Me. With the amp I'm Ghost Building for someone who owns a pair. I probably won't get to the build until the Holiday weekend though...

 I thought the O2s were an excellent match with the Follower Mod, but I'm probably the only one who's heard that combo.


----------



## BoilermakerFan

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Is anyone planning on testing these with the O2 with the new protos currently?_

 

I'm going to see if I can get a member I know to ship his to me for a brief audition, then I'll ship him either my Hybrid or the SS. Probably the SS since he's building an OTT KGSS...


----------



## TimJo

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_
 So do we have two more power supplies working now??? TimJo and Studeb??_

 

Well, I didn't get a chance to power it up yesterday. I had less free time than I was hoping for, and then when I got to the shop, I realized I forgot to bring a power cord. 
	

	
	
		
		

		
			





 Oh well, I worked on the amp instead. It's about halfway finished. At this point, my guess is I won't have the whole thing finished till Thanksgiving. I'm okay with that though, because I'm enjoying taking my time on he build, and because of this, I have a high degree of confidence that it'll power up from the start.

 This morning I grabbed a power cord, so I'll report back with some voltages later...


----------



## TimJo

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Gentlemen, I've had a chance to listen to my hyrid extata this weekend, and so far, my initial impression is that it's definitely on par with my KGSS!
	

	
	
		
		

		
		
	


	




 First off, my headphones are the ESP-950's that I got last year at Christmas, source is an Onkyo DX-7555 component CD player, and I use the pre-amp out of my older JVC RX-8040.
 Why I wanted the hybrid, is I felt the ESP's were somewhat lacking in over all bottom end. Lows were good and clean, but just didn't seem to have the full, warm, deep bass that tubes seem to have. The ESP's are somewhat known for lacking in the bass region, especially with the crappy stock E90 energizer. With the KGSS, the bass definitely improved, but I had started feeding my CD player through my Bijou, which definitely gave me the bass I was missing with just the KGSS. Again, I think it's just more my preference for tubes in the bass region, and not the KGSS.
 Now, to the extata. It definitely achieved the low end I was looking for, without having to have the Bijou in the chain. The bass is very full, warm, and VERY clean and detailed. No muddy sound at all. As far as the mids and highs go, they are the equal to the KGSS in every way, and may actually surpass it in some. Haven't listened long enough to determine. The ESP's have the most air around instruments and best soundstage I've heard so far. They are very detailed, and every instrument is easily seperated and not all blended together. However, the extata/ESP combo is not so analytical that it becomes fatiguing, it's just a fun combo that has you not wanting to stop listining. As dead tired as I was last night, I said to myself I'm only going to listen for about an hour. Three hours later, I finally tore them off my head
	

	
	
		
		

		
		
	


	



 In closing, sorry I don't describe sound in "proper audiophile terminolgy", I'm from South Texas for cryin' out loud
	

	
	
		
		

		
		
	


	




 However, if you're wondering whether to build this amp and how it compares to one of the other top DIY (KGSS) amps, then put your worries aside and build this thing! Not only is it on par with the KGSS, it's considerably cheaper (not quality wise) and much easier to build (especially P2P, which I did on my KGSS) than the KGSS. Alex really has a winner here and finally there's an alternitive to the KGSS
	

	
	
		
		

		
		
	


	




 I do believe that Ericj's goals and dream have been achieved, and then some
	

	
	
		
		

		
		
	


	


_

 

Boy, I'm even more excited to hear the amp after reading this. I just need some phones at this point. 
	

	
	
		
		

		
		
	


	




 Mine are still on order, so there is the chance I'll have it built and tested, and I'll only be able to use it as a heater for a little while. After reading about the ESP950's, maybe I shouldn't hold out for Stax, and start out with the 950's...


----------



## TimJo

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_Some notes about the build:

 There are no R9 and R10 on the board.
 Put the LEDs in before you put the transistors in.
 My heatsinks for Q4 touches the Q7/Q8 heatsink, have to adjust that.
 Maybe put C3 and C4 in after you have the heatsinks in place, it is easier to screw them down without the big caps in the way.
 Also with the screw heads on the inside of the board, the ends of the screws touch C3 and C4
 The rest was pretty straightforward.

 Not sure if i will get the amps built before the long weekend._

 

I agree with these notes as well. 

 As Alex has said many times, if the correct part is inserted with the correct orientation, then the build is a piece of cake. 
	

	
	
		
		

		
		
	


	




 The only part that required a little bit of planning were the orientation of the heatsinks and their hardware, in order to simplify tightening and loosening once in place. As you will discover, once the electrolytics and the big film caps are in, access to the hardware is greatly reduced.


----------



## Beefy

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_The only part that required a little bit of planning were the orientation of the heatsinks and their hardware, in order to simplify tightening and loosening once in place. As you will discover, once the electrolytics and the big film caps are in, access to the hardware is greatly reduced._

 

The way i have done my builds in this past is like this...... I loosely assemble all of the heatsink assemblies. Place one in the board at its correct location, tighten the transistor screw, then remove it from the board and set aside. Repeat for all of them. Then go back and re-fit them one by one, solder, etc.

 Usually I do the assembly and test fit before anything else goes on the board.


----------



## ericj

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_The way i have done my builds in this past is like this...... I loosely assemble all of the heatsink assemblies. Place one in the board at its correct location, tighten the transistor screw, then remove it from the board and set aside. Repeat for all of them. Then go back and re-fit them one by one, solder, etc.

 Usually I do the assembly and test fit before anything else goes on the board._

 


 I'd recommend marking each heatsink with it's part number in pencil or chalk or grease pen or something. Bad things happen if you confuse the fets on the power supply, for example.


----------



## marcus1

I hope to be building a hybrid amp once these prototypes have been tested - can't wait for some more reviews!

 I think the original goal was to build the amp for under $300 - I think that there was some discussion in this thread (about the cost) but can't find it. Could someone please give me a rough idea on the total cost for transformers, boards and components to build the amp?

 Thanks


----------



## studeb

Quote:


  Originally Posted by *marcus1* /img/forum/go_quote.gif 
_I hope to be building a hybrid amp once these prototypes have been tested - can't wait for some more reviews!

 I think the original goal was to build the amp for under $300 - I think that there was some discussion in this thread (about the cost) but can't find it. Could someone please give me a rough idea on the total cost for transformers, boards and components to build the amp?

 Thanks_

 

The proto boards + caps + matched quads were some thing like $40.
 The remaining parts from mouser for a complete sand amp + ps were $160 plus shipping.
 Add whatever you want for jacks, a pot and a case.
 The hybrid parts bill is about $15-20 more.


----------



## Beefy

My PSU BOM comes to $192.53, but that includes the rather expensive Hammond 369JX. My SS amp BOM comes to $77.50. Add volume control, jacks, wiring, IEC and casework, and I will *definitely* be *well* over $300.

 But depending on how cheap you want to go for casework, you can probably _just_ manage it......


----------



## les_garten

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_
 But depending on how cheap you want to go for casework, you can probably just manage it......_

 

Which is AMAZING!


----------



## runeight

This seems high to me, but I may not be doing my own math right.

 Having just bought the parts, I think I paid about $150 for both PS and amp (SS version). Add $25 for the board set that's $175. Then add transformer, jacks, etc. 

 The original goal was <$300 BEFORE casework. I think we are within that limit if you don't use boutique parts. 

 Of course, we never did define what "before casework" means. Perhaps Ericj can clarify. 
	

	
	
		
		

		
		
	


	




 If casework is a broad definition that includes IEC inlets, switches, fuses, knobs, hardwar, etc (which was my interpretation) then I think we've met the goal.


----------



## Beefy

Oh crap, mine is in Canadian dollars too......


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_This seems high to me, but I may not be doing my own math right.

 Having just bought the parts, I think I paid about $150 for both PS and amp (SS version). Add $25 for the board set that's $175. Then add transformer, jacks, etc. 

 The original goal was <$300 BEFORE casework. I think we are within that limit if you don't use boutique parts. 

 Of course, we never did define what "before casework" means. Perhaps Ericj can clarify. 
	

	
	
		
		

		
		
	


	




 If casework is a broad definition that includes IEC inlets, switches, fuses, knobs, hardwar, etc (which was my interpretation) then I think we've met the goal. 
	

	
	
		
		

		
		
	


	


_

 

I would say your definitions are correct, or rather, all the bits required to get it up and running on the bench. I went boutique so, uh, well, I don't keep track of stuff like that, at least not publicly. 

 My package arrived today Alex, so PP will be heading your way this evening.


----------



## Emooze

I got free sample enclosures from Teko. I'm pretty sure I'm sitting right around $250 which includes boards, all components, Stax jack, RCA jacks, e27 and Alps RK27 from AMB and 600v wire because I had none.


----------



## ericj

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_If casework is a broad definition that includes IEC inlets, switches, fuses, knobs, hardwar, etc (which was my interpretation) then I think we've met the goal. 
	

	
	
		
		

		
		
	


	


_

 

That's basically how i interpret it too. 

 There are those who will choose to spend more on a custom machined front panel than i will spend on case work for both of my amps combined, and many who have no problem spending more on a single knob than i'm likely to spend on all the case work for my SS amp. So far I'm at $16 for case & front panel, btw. 

 So, the total cost of the amp can go anywhere. Some will choose to DIY a wood or metal case out of materials they already have, and they may well case it cheaper than i. Many will spend a lot more. Some will spend well over $100 on cosmetics.


----------



## BoilermakerFan

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_Some will spend well over $100 on cosmetics._

 

I'm actually hoping to find a C-mount camera lens for less than that.


----------



## pabbi1

I spent $315 on a sand version with Triads, and about $340 on a DIY wood exclosure hybrid. 







 And, I do have incoming boards to build the latest version - just not sure if it will be another unit, or retrofit this one.


----------



## Lou Erickson

What values are those of you with running amps using for the volume pot? I don't see one specified. 50kohm? 10kohm?

 I really want to find a quad pot. I know I'd be fiddling with separate ones constantly. They seem unusual. And some seem really foolishly expensive.


----------



## runeight

From the amp's point of view anything from 10k to 100k would be suitable. The lower the value the less noise, but most amps seem to use 50k.


----------



## MrMajestic2

Im going over my eXstatA parts list and I cant seem to find a replacement for the R17, R18, R20, R21 on the hybrid. Any ideas?


----------



## wiatrob

Quote:


  Originally Posted by *Lou Erickson* /img/forum/go_quote.gif 
_What values are those of you with running amps using for the volume pot? I don't see one specified. 50kohm? 10kohm?

 I really want to find a quad pot. I know I'd be fiddling with separate ones constantly. They seem unusual. And some seem really foolishly expensive._

 

Dual pots is much less of a hassle than many people think. Many people listened to the proto at RMAF with dual pots, no one complained.


 I'm using dual (cheap) two channel stepped attenuators in my new builds.


----------



## runeight

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Im going over my eXstatA parts list and I cant seem to find a replacement for the R17, R18, R20, R21 on the hybrid. Any ideas?_

 

Could you re-post the resistors in question. These are different resistors on the schematic. Thanks.


----------



## TimJo

Just a quick update, and then I need to get back to work.

 The P/S came up without a hitch. These measurements are from work, which has lower line voltage than home. I'll test it again tonight when I'm home.

 Line - 119.2v
 369JX unloaded - 271v
 369JX loaded - 257v
 Upper rail - 310v
 Lower rail - 309v
 T1 to gnd - 324v
 T3 to gnd - 321v

 Also, this is with 300 volts in the zener chain, rather than 291 volts.


----------



## MrMajestic2

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Could you re-post the resistors in question. These are different resistors on the schematic. Thanks._

 

Doh, its for the PSU, not the amp. But here they are:
 R17, R18, R20, R21 1/2W 1% Metal Film Resistor 250KΩ

 Not a good idea to do this late at night.


----------



## runeight

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Just a quick update, and then I need to get back to work.

 The P/S came up without a hitch. These measurements are from work, which has lower line voltage than home. I'll test it again tonight when I'm home.

 Line - 119.2v
 369JX unloaded - 271v
 369JX loaded - 257v
 Upper rail - 310v
 Lower rail - 309v
 T1 to gnd - 324v
 T3 to gnd - 321v

 Also, this is with 300 volts in the zener chain, rather than 291 volts.




_

 

This is so strange. Tim could you check T1/T3 to ground. Other folks are getting 355V at these points ane you are getting 30V lower than this for about the same line voltage. If the T1/T3 remain at 324/321 then it would be better to use the 91V zeners.


----------



## runeight

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Doh, its for the PSU, not the amp. But here they are:
 R17, R18, R20, R21 1/2W 1% Metal Film Resistor 250KΩ

 Not a good idea to do this late at night._

 

Are the 249k resistors in the BoM not available? If not, try 240k or even 220k if you have to.


----------



## Sathimas

You guys keep me dreaming.

 Since I am not a very experienced builder, I'll wait for the final version.

 For now all I can do is dream of electrostatic amps and render things I'll build


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_This is so strange. Tim could you check T1/T3 to ground. Other folks are getting 355V at these points ane you are getting 30V lower than this for about the same line voltage. If the T1/T3 remain at 324/321 then it would be better to use the 91V zeners._

 

Man, I think I'll order both the 91V and extra 100V diodes...


----------



## Lou Erickson

I may have had an alternate for that resistor, but my notes are at home. I just placed an order last night which had nothing backordered. I'll post what I found for those, but it may not be till late tonight. I'm pretty sure the only substitutions I had to make were good... and if not, I'd like to know it ASAP. 
	

	
	
		
		

		
		
	


	




 As far as pots go, using two stepped attenuators would be less annoying, because you'd be confident you had them on the same setting. I'd still rather have one control, and if all it takes to get it is an extra $40, so be it.

 I think that makes the case my last big unknown. Any suggestions for affordable ones would be welcome.


----------



## runeight

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_You guys keep me dreaming.

 Since I am not a very experienced builder, I'll wait for the final version.

 For now all I can do is dream of electrostatic amps and render things I'll build 
	

	
	
		
		

		
		
	


	






_

 

Sathimas, very happy to know that you're interested. However, unless these beta builds all blow up, this IS the final version.


----------



## ericj

Alex, I have the 269jx and the 270ax, and have the higher-current follower resistors on my hybrid amp. Would it be useful for me to get you some voltage readings?


----------



## runeight

Yes please. Both T1/T3 to ground and T1-T2, T3-T4 and the rail voltages.

 Thanks.


----------



## BoilermakerFan

Quote:


  Originally Posted by *Lou Erickson* /img/forum/go_quote.gif 
_I may have had an alternate for that resistor, but my notes are at home. I just placed an order last night which had nothing backordered. I'll post what I found for those, but it may not be till late tonight. I'm pretty sure the only substitutions I had to make were good... and if not, I'd like to know it ASAP. 
	

	
	
		
		

		
			





 As far as pots go, using two stepped attenuators would be less annoying, because you'd be confident you had them on the same setting. I'd still rather have one control, and if all it takes to get it is an extra $40, so be it.

 I think that makes the case my last big unknown. Any suggestions for affordable ones would be welcome._

 

The surplus NABU gets my vote! 

 Lots of room for 1/2" stand-offs and 2-1/2" heatsinks. Probably room for the transformers in the PSU side too.


----------



## Coreyk78

Got my power supply set up.

 269JX, 119.2v mains
 T1-gnd = 339v
 T3-gnd = 337v
 +300.5v
 -300.4v

 easy set up, pretty rock solid after a little more tweaking on P1,P2 when things warmed up


----------



## audionut

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_Got my power supply set up.

 269JX, 119.2v mains
 T1-gnd = 339v
 T3-gnd = 337v
 +300.5v
 -300.4v

 easy set up, pretty rock solid after a little more tweaking on P1,P2 when things warmed up_

 

Corkey78, Which zener string did you use, the 291v, or did you go with the 300v string? Thanks, Tommy


----------



## BoilermakerFan

Question on the R-Core for the SS: 

 R80-36 260-230-0-230-260(90mA). 2.5-0-2.5(3A).(3.15-0-3.15)X2(3A)

 I should use the 230-0-230 taps with 291V Zeners and not the 260-0-260 with 300V Zeners correct?

 Happened to notice that that transformer is also perfect for a Bijou too... 

 My target chassis has a 60mm height restriction on the bottom of the sub-chassis. Or it's also a great fit in the PSU section of a NABU.


----------



## runeight

Yes, use the 230 taps with 291V zeners. 260 will melt everything.


----------



## Coreyk78

I used the ones spec'd in the BOM, so 291v right?


----------



## Beefy

Man, some HUGE variation in readings from different people with the same transformer.

 I wonder whether everybody's multimeters up to the job of these high voltages?


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes, use the 230 taps with 291V zeners. 260 will melt everything. 
	

	
	
		
		

		
		
	


	


_

 

Thanks. Now the big question is whether to order one, two, or three...


----------



## runeight

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_I used the ones spec'd in the BOM, so 291v right?_

 

Right.


----------



## runeight

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Man, some HUGE variation in readings from different people with the same transformer.

 I wonder whether everybody's multimeters up to the job of these high voltages?_

 

Exactly. This is not adding up ... yet.


----------



## Coreyk78

I'm using a Fluke 87, I trust it


----------



## runeight

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Thanks. Now the big question is whether to order one, two, or three... 
	

	
	
		
		

		
		
	


	


_

 

I know that I've mentioned this and I know that your reply was most gracious, but this transformer is much heftier than is really needed and it won't add anything to the performance of the PS or the amp.

 I just felt I should say this one more time. I'll stop now.


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I know that I've mentioned this and I know that your reply was most gracious, but this transformer is much heftier than is really needed and it won't add anything to the performance of the PS or the amp.

 I just felt I should say this one more time. I'll stop now. 
	

	
	
		
		

		
		
	


	


_

 

It's not a power or performance issue, it's a size issue (or 230V primaries for some) and difficult restrictions my desired chassis places on an aesthetically pleasing build. It's the closest R-Core to the spec'd 480VCT... 460VCT is actually a little under voltage. The other windings will be used to power other input boards in the SS version just like the Hybrid.


----------



## runeight

OK. That was my last thought on the topic. 
	

	
	
		
		

		
		
	


	




 Now to figure out why the readings are so different for what seem to be nearly identical circumstances.


----------



## pabbi1

Alex, resistance is futile. 
	

	
	
		
		

		
			





 And, one more time with a link to the veritable NABU case - amazing how many of these they have. There are also some new possibilities on that page, especially the SRS Remote, which looks to have an Amphenol 6 pin jack. The NABU is the most time tested DIY box out there, and the best bang for buck REPEATABLE experience, bar none.


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Now to figure out why the readings are so different for what seem to be nearly identical circumstances. 
	

	
	
		
		

		
		
	


	


_

 

Hammond QC sucks? Or parts at the very ends of the tolerances? 

  Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Alex, resistance is futile. 
	

	
	
		
		

		
		
	


	




 And, one more time with a link to the veritable NABU case - amazing how many of these they have. There are also some new possibilities on that page, especially the SRS Remote, which looks to have an Amphenol 6 pin jack. The NABU is the most time tested DIY box out there, and the best bang for buck REPEATABLE experience, bar none._

 

And a huge thanks to Pabbi for introducing me to that chassis! I have 5, but I'll probably order 5 more after the first of the year.


----------



## audionut

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_OK. That was my last thought on the topic. 
	

	
	
		
		

		
		
	


	




 Now to figure out why the readings are so different for what seem to be nearly identical circumstances. 
	

	
	
		
		

		
		
	


	


_

 

Alex, I went ahead and ordered more 100V zeners from Mouser today, since I have till the end of the week to return my CAX xfmr. Curiosity got the best of me, and I decided to try the 300V zener string to see if it drops the T1,T3 voltage to acceptable level. I will put them in my PS tomorrow when they come in, and report back my findings. Tommy


----------



## audionut

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_I used the ones spec'd in the BOM, so 291v right?_

 

If you're getting 339, and 337 at the T1,T3 testpoints, then you are closer to the voltages that Alex said they need to be, and probably will not have PS fets getting too warm. With the same secondary rating and line voltage as yours, I was getting 357V at the T1,T3 points. Alex may have something to add to what I've said, too.


----------



## ericj

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes please. Both T1/T3 to ground and T1-T2, T3-T4 and the rail voltages.

 Thanks._

 

Alright, hybrid amp with increased follower current by resistors, 269jx: 

 Line voltage: 119.5vac

 High voltage secondaries: both steady at 271.3vac

 T1 to ground: 341vdc

 T3 to ground: -340vdc

 T1-T2: .378vdc

 T3-T4: .409vdc

 Rails after regulation: -300vdc/+298.7vdc (and creeping upward - this n-channel FET is still burning in i think) 

 Heatsink temperatures (IR thermometer): 

 Q3: 110F
 Q5/Q6: 92F
 Q7/Q8: 93F
 Q4: 104F

 Q9L: 130F
 Q10L: 146F
 Q9R: 145F
 Q10R: 125F

 270AX numbers in about 15-20 minutes

  Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_The surplus NABU gets my vote! 

 Lots of room for 1/2" stand-offs and 2-1/2" heatsinks. Probably room for the transformers in the PSU side too._

 

You could fit three of these amps in the NABU!


----------



## ericj

Alright, hybrid amp with increased follower current via resistors on the 270AX: 

 Line voltage: 118.5vac

 HV secondaries: both 257.3vac

 T1 to ground: 312.8vdc

 T3 to ground: -311vdc

 T1-T2: .379vdc

 T3-T4: .411vdc

 Rails after regulation: -300vdc / +287vdc (Edit: This crept up to +298vdc while i was testing, with T1-T2 up to 381mv) 

 Heatsink temperatures: 

 Q3: 91F
 Q5/Q6: 90F
 Q7/Q8: 94F
 Q4: 85F

 Q9L: 115F
 Q10L: 140F
 Q9R: 138F
 Q10R: 120F


----------



## studeb

Sand PS is up and running
 Went fine

 AC 120V
 Secondary 259V
 T1 332V
 T3 327V
 Across Load R 301 and 302V
 T1-T2 0.35V
 T3-T4 0.40V

 edit, no power LED yet


----------



## MrMajestic2

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Are the 249k resistors in the BoM not available? If not, try 240k or even 220k if you have to._

 

Nope, they are out of stock. 221k is available though.


----------



## MrMajestic2

By the way, would these make good load resistors?

NH-50 50 1% C02 Vishay/Dale Power Resistors Wire Wound


----------



## runeight

They would, but they need to be 10k. And don't forget the 5k1 to parallel the 10k on the negative rail.


----------



## Lou Erickson

Quote:


  Originally Posted by *Lou Erickson* /img/forum/go_quote.gif 
_I may have had an alternate for that resistor, but my notes are at home. I just placed an order last night which had nothing backordered. I'll post what I found for those, but it may not be till late tonight. I'm pretty sure the only substitutions I had to make were good... and if not, I'd like to know it ASAP. 
	

	
	
		
		

		
		
	


	


_

 

Apparently these are not the one I remember having to find a substitution for. I guess I got the last ones. My order last night said they were all in stock, but they now say they have shipped 6 of 8. Yay. They also decided to only ship one of the two 269JX transformers. Strange.

  Quote:


 I think that makes the case my last big unknown. Any suggestions for affordable ones would be welcome. 
 

Yes, that NABU case is tempting. It's big! The price is sure right, though. There's a couple of fun things on that page. That walnut cabinet attracts the eye... a chassis to bolt things to and a front panel from Front Panel Express would make a lovely amp. Not cheap, though.


----------



## MrMajestic2

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_They would, but they need to be 10k. And don't forget the 5k1 to parallel the 10k on the negative rail. 
	

	
	
		
		

		
		
	


	


_

 

Ok. I was thinking the same as for the S22 would work. Good thing I didn't try it without asking first 
	

	
	
		
		

		
		
	


	



 What wattage does the 5K1 need to be?


----------



## sachu

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_What wattage does the 5K1 need to be?_

 

Umm i think Alex meant that to be 51k. 

 They need to be 5 Watt resistors.. Everything is in the BOM.


----------



## MrMajestic2

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Umm i think Alex meant that to be 51k. 

 They need to be 5 Watt resistors.. Everything is in the BOM. 
	

	
	
		
		

		
		
	


	


_

 

Damn, I just assumed they were not in there, but I see now that they are. Thanks. I shouldn't be doing Mouser lists at night.


----------



## TimJo

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Just a quick update, and then I need to get back to work.

 The P/S came up without a hitch. These measurements are from work, which has lower line voltage than home. I'll test it again tonight when I'm home.

 Line - 119.2v
 369JX unloaded - 271v
 369JX loaded - 257v
 Upper rail - 310v
 Lower rail - 309v
 T1 to gnd - 324v
 T3 to gnd - 321v

 Also, this is with 300 volts in the zener chain, rather than 291 volts.




_

 

 Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_This is so strange. Tim could you check T1/T3 to ground. Other folks are getting 355V at these points ane you are getting 30V lower than this for about the same line voltage. If the T1/T3 remain at 324/321 then it would be better to use the 91V zeners._

 

Sorry for the delay getting back about this. This is my first chance to look at this again. 

 The original measurements were taken at work, and I could bring it back if you want to see if I misread the readings. I'm getting the feeling they might have been 334/331 at the caps, based on what I just saw here.

 At home, which is where I'll be using it, this is what I get after letting it burn in for a while so that the regulation had stabilized.

 Line 121.4v
 Tran 265v
 T1-T2 ~360mv
 T3-T4 ~410mv
 T1-gnd ~339v
 T3-gnd ~336v
 + rail 312v
 - rail 310v

 What do you think now?


----------



## cfcubed

Quote:


  Originally Posted by *Lou Erickson* /img/forum/go_quote.gif 
_Yes, that NABU case is tempting. It's big! The price is sure right, though._

 

Fleabay johnango (AnTek) cases are not news around here but @ last NY meet Nate gave me a heads-up on them like these.
 I've gone 'round on cases from making my own from raw materials to using cheapo ones. 
 Now thinking that since, at some point, my builds are looked at perhaps it's worth spending $100USD to impress non-DIYers
	

	
	
		
		

		
			





: 
 But lots of factors come into play of course & wouldn't spend that for a test build, etc.


----------



## pabbi1

I really do want to point out this design is well beyond what I would consider a test build, and worthy of a nice case. While there are some final tweaks, this amp is up and running. Mine has been running well for about 2 months for the sand, and 6 weeks on hybrid, with daily use.

 But, for those being cost conscious, there are economic options, and some DIY options (shout out to zcool) that surpass a lot of "commercial" packages.

 I have also used Antek in the past, with good results, IFF you buy what is readily available on an auction, but Pars-metal has been spotty off and on (annodizing, specifically and availability/delivery).

 Pity that casing options are the hardest part of any build.


----------



## Coreyk78

I'm going to use a 12"x12" Par-Metal case for mine, I'm debating if I want to have an FPE panel made for it, since I think I'm going to have one made for my Buffalo. I think I'm going to start on case work tonight since I have everything but my 4 pole Alps blue pot that is supposed to be coming at some point from Tubeshunter in China that I bought off ebay.


----------



## Beefy

I'm going to use a HiFi2000 Pesante 2U 300mm deep, FPE front (6mm) and back (4mm).

 Together with my Buffalo24 going into an identical case and panel style, they will be my magnum opus.


----------



## n_maher

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_they will be my magnum opus._

 

I've heard this before, don't kid yourself.


----------



## pabbi1

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I've heard this before, don't kid yourself._

 

QFT - Magnum Opus, du jour maybe...


----------



## Lou Erickson

These are some excellent ideas for cases, thank you!

 It is somewhat ironic that the casework is often the most difficult part, yes.

 I have had an idea for a case, but I suspect it will be expensive. I think I'll get a simpler box and recase it later in grand style if I'm still pleased with it after a bit. I expect to be, but would like to get a project or two actually finished. A detailed case can be a later project.


----------



## Beefy

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I've heard this before, don't kid yourself._

 

Why not? You managed to retire successfully......


----------



## pabbi1

Yeah, Nate, can you define "retired"? 
	

	
	
		
		

		
		
	


	




 That said, I have at least 3 Magnum Opus(es) lined up in my office right now, meaning I know a place where dreams get crushed... and eXStata is NOT one of those places. It makes DIY _fun_ again.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Yeah, Nate, can you define "retired"? 
	

	
	
		
		

		
		
	


	




 That said, I have at least 3 Magnum Opus(es) lined up in my office right now, meaning I know a place where dreams get crushed... and eXStata is NOT one of those places. It makes DIY _fun_ again._

 

LOL! Mine are coming along a little slower than the Sistine Chapel and two have changed completely in just over a year of planning.


----------



## n_maher

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Yeah, Nate, can you define "retired"? 
	

	
	
		
		

		
		
	


	


_

 

Sure, I now occasionally allow myself to say "no" but reserve the right to say yes. My Magnum Opi(?) are in the works and like you Al, the eXStata isn't one of them.


----------



## wiatrob

Well, Larry, your parts are almost all here. I'll start stuffing this weekend most likely. 

 Just gotta figure out how to do a SE/Balanced input selector switch (or of course, balanced/balanced). Any of you vets know of a suitable switch model?


----------



## les_garten

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Well, Larry, your parts are almost all here. I'll start stuffing this weekend most likely. 

 Just gotta figure out how to do a SE/Balanced input selector switch (or of course, balanced/balanced). Any of you vets know of a suitable switch model?_

 

This is of interest to me as well.


----------



## Hopstretch

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_My Magnum Opi(?) are in the works and like you Al, the eXStata isn't one of them. 
	

	
	
		
		

		
		
	


	


_

 

Well, I hope you'll still put at least a smidgen of effort into it!


----------



## spritzer

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Just gotta figure out how to do a SE/Balanced input selector switch (or of course, balanced/balanced). Any of you vets know of a suitable switch model?_

 

I normally just use two ON-ON 3PDT switches on each side of the back panel but a 4PDT will work by leaving the GND shared. For 6PDT is available not in a toggle switch.


----------



## sachu

a 4PDT gets my vote.


----------



## audionut

Gentlemen, Just a quick update on the transformer questions and PS fets getting too hot. I orderd a Hammond 270CAX, 250-0-250 for my hybrid. When I got it up and running last week, the T1,T3 voltages were higher than Alex wanted to see there at +/- 352VDC, my line voltage runs 122VAC. He said they should be around 325VDC, and my PS fets may get too hot. To the touch, they were getting hot enough to only be able to keep my finger on either fet heatsink for about 5 seconds or so. Alex sent me a 269AX 240-0-240 to try. That dropped fet temp considerably, and were barley warm to the touch. Today, I got some more 100V zeners in to get a 300V string, and put the 250-0-250 back in, and fets are cooler and I'm able to keep finger on either one for 30 sec or more before getting a bit uncomfortable. Rails only went up to +/- 313V, up from 304V.
 For those who already purchased a 250-0-250 xfmr, and if your T1,T3 voltages are high, the easier thing to do is to use the 300V zener string in place of the 291V string, instead of trying to exchange xfmr like I almost did with Mouser. A couple of 100V zeners is only 10 cents, and was an easier route for me. Everyone can decide for themselves, though. Tommy.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Well, Larry, your parts are almost all here. I'll start stuffing this weekend most likely. 

 Just gotta figure out how to do a SE/Balanced input selector switch (or of course, balanced/balanced). Any of you vets know of a suitable switch model?_

 

Do you want to borrow the O2 Mk1 again, for testing? We'll be up in the Denver area (Lafayette) Thursday for Thanksgiving brunch, and as long as I don't have to detour much then I could bring them with me.

 I don't think I can offer help on the switch.


----------



## wiatrob

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Do you want to borrow the O2 Mk1 again, for testing? We'll be up in the Denver area (Lafayette) Thursday for Thanksgiving brunch, and as long as I don't have to detour much then I could bring them with me.

 I don't think I can offer help on the switch. 
	

	
	
		
		

		
		
	


	


_

 



 I appreciate the offer, but I will let you be one of the first to enjoy this combo. 

 I have the Lambda Normal and Sigs fro Norm/Pro testing. Er, and the electrets for smoke tests.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I appreciate the offer, but I will let you be one of the first to enjoy this combo. 

 I have the Lambda Normal and Sigs fro Norm/Pro testing. Er, and the electrets for smoke tests. 
	

	
	
		
		

		
		
	


	


_

 

So, have you found a selector switch/knob that could match the volume knob in style if not size, to mount on the front of the amp?


----------



## runeight

Someone suggested that an input selector diagram might be helpful. This is one way to use a DPDT switch to select input so that both SE and Balanced can remain connected simultaneously. A 4PDT switch will select both channels.

 Diagram shows both positions:






 Please check my wiring.


----------



## Anouk

Hello Thanks Alex for designing this amp and Eric for the idea.
 I am following this thread with a lot of interest not as a diyer but an interested party in a relatively cheap but good stat amp, will be interesting to see how this beta program develops and how it eventually compares to whatever amps stax themselves are using now.
 Greetings, Anouk


----------



## pabbi1

Any LA area prototypers? Please shoot me a PM.


----------



## digger945

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Someone suggested that an input selector diagram might be helpful. This is one way to use a DPDT switch to select input so that both SE and Balanced can remain connected simultaneously. A 4PDT switch will select both channels.

 Diagram shows both positions:






 Please check my wiring._

 

The only difference between this scheme and Ti's switching scheme is to have the attenuator before the switch(on the negative amp input) so when in the unbalanced position the negative amp input is shorted directly to ground, bypassing the variable resistance to ground for that input.






 I know not the advantages of such a method, but apparently Ti does
	

	
	
		
		

		
		
	


	




(and I've used this method in my own balanced amp without issue)


----------



## runeight

Ti's method might be considered a little more perfect, but I don't think it will make any difference either way and I prefer the full input signal through the switch before attenuation on both sides.

 Having the negative input connected to the wiper when both ends of the pot are grounded shouldn't cause problems unless the pot is defective. The pot will provide low enough resistance to ground to keep the gate of the fet well grounded. Furthermore the fets have 1M gate leak resistors that prevent the gates from getting too far from ground.

 But, however anyone wants to do this is ok with me.


----------



## wiatrob

Now to find a suitable rotary switch. I know Larry won't want to reach behind the amp and throw two switches


----------



## les_garten

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Now to find a suitable rotary switch. I know Larry won't want to reach behind the amp and throw two switches 
	

	
	
		
		

		
		
	


	


_

 

It would be a single 4PDT right? Or would it need two?


----------



## HeadphoneAddict

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Now to find a suitable rotary switch. I know Larry won't want to reach behind the amp and throw two switches 
	

	
	
		
		

		
		
	


	


_

 

That would be much nicer. I am not forgetting that I still need to pay for the case and rotary switch, since Sherwood got the extra cash that I had on me that day for his TT, which would have gone towards the rest of the parts.


----------



## digger945

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_It would be a single 4PDT right? Or would it need two?_

 

You could use one 4PDT switch for stereo/two channels/four wires.
 Or two DPDT switches, one for each stereo channel/two wires, and flip them both at the same time.

 I used this Mountain 4PDT switch from Mouser cuz it is oriented such that the toggle bat would be moved up and down with the poles of the switch side by side, and it's solder tab, and it fits a 1/4" hole(small booger).
 There are many different ones that could be used though. Some have used the TPA OTTO for this.


----------



## bidoux

I'm sorry if answers to my question have been posted, the thread is just really long. Is there any substitutes for KSC5042M (they are 5.91€ each) and where can we buy boards ?


----------



## Beefy

KSC5042M is the wrong part number...... where did you get that from? They are obsolete, hence the high price. The correct part number for a current production part is KSC5042F, and they are less than a dollar at Mouser.


----------



## runeight

You can sub the KSC5027 from fairchild. Or any 800-900V Vceo NPN TO220 BJT that has a base power rating of at least 10W.

 While I still have a few boards left from the proto run you can buy them from me at $25 a set (amp and PS) plus shipping. I have a few more SS boards than hybrid boards.

 Edit: See Beefy's cross-posted reply.


----------



## bidoux

Thank you Beefy and runeight. I'm trying to source most part from the same source so I got the KSC5042 from Awatronic.
 I guess I'll have to order at mouser's... I'm more interested in the solid state version. I'll see.


----------



## pabbi1

Outta be some feedback by now, no?


----------



## sergery

I could use some feedback. I am not sure if my transformer is to blame, but it keeps blowing fuses, getting super hot, smoking, and leaking stinky fluid. Now the tafo is putting out only a few volts from the 250 volt tap. The only thing I can think of I may have done wrong is my q5/6 may have been heat damaged from a desolder/move. It doesn't seem like this should be enough to kill a trafo? Was this a bad unit? 

 I am pretty sure it was wired correctly, blue/black to live, brown/ white to neutral. Red's to 250's, red&yellow to CT. Load resistors as in the instructions. Hammond's website for reference. I have a 369jx. Regardless I guess I need a new one, what is the new recommended or is the call yet to be made?


----------



## runeight

It sounds like the trafo was shorted out for quite a while. And if so there are probably other things wrong in the PS.

 Is the secondary low when it's disconnected? Or only when connected?

 If only when connected, first check the orientation of all of your diodes. On vertical devices the cathode stripe is up and away from the board.

 Then check the polarity of all the transistors, particularly Q3 and Q4 and the orientation of their zener diodes.

 Then check for solder bridges and other wiring shorts.


----------



## Emooze

Pretty sure the last of my parts are in my school mailbox, I'll have it together hopefully this week.


----------



## Coreyk78

I should have time to finish wiring mine up later tonight, hopefully I'll be able to do some initial listening with my electrets, my SR 404's should be here in the first half of next week.


----------



## sergery

Zener's and q3/4 are correct. When I looked today it was immediately obvious - in the bundle of wires I had tied together out of the way, two of the filament wires had come in contact. what a stupid mistake. 
	

	
	
		
		

		
		
	


	




 Well now I am in the market for a new transformer, given my ~123V mains and mixed luck people have been having, I am unsure what to go for. any thoughts? (I used the 291V zener string)


----------



## Beefy

Quote:


  Originally Posted by *sergery* /img/forum/go_quote.gif 
_in the bundle of wires I had tied together out of the way, two of the filament wires had come in contact. what a stupid mistake. 
	

	
	
		
		

		
		
	


	


_

 

HEH! I _always_ have a terminal block handy before hooking up a power supply for the first time, to screw down all transformer wires before I connect them to anything.......


----------



## ericj

Quote:


  Originally Posted by *sergery* /img/forum/go_quote.gif 
_Zener's and q3/4 are correct. When I looked today it was immediately obvious - in the bundle of wires I had tied together out of the way, two of the filament wires had come in contact. what a stupid mistake. 
	

	
	
		
		

		
		
	


	




 Well now I am in the market for a new transformer, given my ~123V mains and mixed luck people have been having, I am unsure what to go for. any thoughts? (I used the 291V zener string)_

 


 Well i have one more transformer than i need. I just need to figure out which one to get rid of. You are in california and thus do not need the dual primaries, right? 

 Which reminds me, I wonder if Alex has any comments wrt the voltage readings i posted a few days back.


----------



## sergery

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_HEH! I always have a terminal block handy before hooking up a power supply for the first time, to screw down all transformer wires before I connect them to anything......._

 

I think this is the route I will be going from now on, good idea!

 Ericj, what models do you have? Although I don't NEED the dual primaries, I am interested in the nicer quality iron and, supposedly, lower mechanical noise.


----------



## BoilermakerFan

Quote:


  Originally Posted by *sergery* /img/forum/go_quote.gif 
_<snip> I am interested in the nicer quality iron and, supposedly, lower mechanical noise._

 

Then you need an Electra-Print.


----------



## les_garten

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_Well i have one more transformer than i need. I just need to figure out which one to get rid of. You are in california and thus do not need the dual primaries, right? 

 Which reminds me, I wonder if Alex has any comments wrt the voltage readings i posted a few days back._

 

I'm not following you on the Dual Primaries? Why on this amp would you need dual primaries?


----------



## BoilermakerFan

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_I'm not following you on the Dual Primaries? Why on this amp would you need dual primaries?_

 

The 120/240 primaries. 120V for US, 240V for the ROTW. Les, you'll only need 120V primary, but the 300 series Hammond is a dual primary trafo with better build quality than the 200 series. The E-P trafo would be a little more than the Hammond 300 series with only one primary voltage winding (about $95 in M19 IIRC), but it's a hand-wound transformer of much higher quality than the Hammond and you'd be supporting a small, private US business. The E-P is also physically larger, built on a 125VA frame for roughly a 3" cubed package size. 

 If your going to do a more integrated build like mine, I can walk you through a lot of it via PMs or email later. My AudioSector rectifier and phono stage boards showed up, but I didn't know Peter had F5 boards and a universal PSU board, so I'm ordering (8) F5 boards and (4) full PSU boards, so the PSUs for the DC heaters and OptiVol/relay switching just became a lot easier to build for my eXStata Hybrid. The eXStata SS will cased up with the balanced F5 so I can bring just one amp to meets and play all headphones or even speakers.


----------



## les_garten

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_The 120/240 primaries. 120V for US, 240V for the ROTW._

 

I understand that. Just not sure about one person in Utah saying it to someone in CA


----------



## BoilermakerFan

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_I understand that. Just not sure about one person in Utah saying it to someone in CA_

 

I suspect Eric has a spare 200 series, but Sergery lost a 300 series... Sergery didn't need the dual primaries to power the amp, he went with the 300 series for better build quality.


----------



## luvdunhill

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_my eXStata Hybrid and the eXStata SS will cased up with the balanced F5 so I can bring just one amp to meets and play all headphones or even speakers._

 

this could turn out pretty badly, IMHO. You're going to need a lot of aluminum if you're planning on hitting the target F5 bias times four in a single chassis.


----------



## BoilermakerFan

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_this could turn out pretty badly, IMHO. You're going to need a lot of aluminum if you're planning on hitting the target F5 bias times four in a single chassis._

 

I edited my original post, but only the balanced F5 (running at 1.3A) and eXStata SS would be in a single chassis. PSU will be in separate chassis. It will have four separate heatsinks. One side and one top sink per F5 balanced channel. The eXStata will actually be in the middle with 2-1/2" heatsinks on the boards, isolated via sheetmetal from the two F5s on each side. 2" high cone feet underneath so it has enough room for air flow around and under the chassis. She's not going to be a small amp. Or light, but she will be transportable in a rolling Pelican case. 

 If it gets really tight or I have problems with too much heat even at the lower 1.3A bias level, I'd have to drop down to a SE F5 on each side, but the plan is to use each balanced side as a separate SE headphone amp for the dynamics/orthos...


----------



## luvdunhill

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I'd have to drop down to a SE F5 on each side..._

 

That's where my money will be 
	

	
	
		
		

		
			





 Have fun though and see if you can track down those out of production Fairchild parts.


----------



## BoilermakerFan

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_That's where my money will be 
	

	
	
		
		

		
		
	


	




 Have fun though and see if you can track down those out of production Fairchild parts._

 






 Thanks. 
	

	
	
		
		

		
		
	


	




 The FQA12P20 and FQA19N20s? Already found 'em. Also ordering some Toshibas as an alt just because I like to roll transistors almost as much as tubes. 

 But more importantly, I've been persuaded and now believe the F5 will serve my purpose of having a high power SS ortho amp that isn't a B22 to complement the eXStata SS. Does it get any better than an Alex Cavalli and a Nelson Pass design in the same chassis when they have to be SS amps?


----------



## ericj

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I suspect Eric has a spare 200 series, but Sergery lost a 300 series... Sergery didn't need the dual primaries to power the amp, he went with the 300 series for better build quality._

 


 Yup. I have both the 269jx and the 270ax. 

 The 300 series may have "less" mechanical noise than the 200 series but i lose very little sleep over sounds that are merely inaudible rather than less than inaudible.


----------



## Coreyk78

My Exstata is alive 
	

	
	
		
		

		
		
	


	




 fired up perfectly the first time, spent a lot of time being anal retentive adjusting the offsets on each channel, all measurements less than 100mV.

 I'm listening to it with my SR-30's right now, pretty damn sweet so far, seems to give a little more weight to the bass compared to the SRD-4 energizer. I don't like to describe sound, but I think it sounds very nice. Great job Alex! Can't wait for my 404's to show up now!


----------



## Coreyk78

Couple of quickie pictures, my photography skills are poor, sorry.


----------



## sachu

very nice


----------



## n_maher

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_The 300 series may have "less" mechanical noise than the 200 series but i lose very little sleep over sounds that are merely inaudible rather than less than inaudible._

 

You may find that after a few years you regret your decision. I had a 200 series that was not only audible when using open headphones (which just about all stats are) it was actually leaking hum into the audio. You might also find out that the humming/buzzing is enough so that if you have a microphonic tube it affects that as well.


----------



## Beefy

That is awesome Coreyk...... the PS boards just look awesome with those massive 1µF caps on the output 
	

	
	
		
		

		
		
	


	




 *

 With all this talk of transformers...... for those of us planning on the SS build, is there any other high-quality alternative to the Triad that doesn't have the filament windings? I have been planning on the Hammond 370AX or 369JX all along, but am probably paying a lot extra for filament windings that I don't need.

 I really just want a nice single unit 115+115 50/60Hz primary, 2x 240 (or 250) secondary. Does anybody make anything like this off-the-shelf?

 Alternatively, I wonder if SumR can do a custom jobbie, potted and shielded, for not much more than the Hammond....... hmmmmmm......


----------



## runeight

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_My Exstata is alive 
	

	
	
		
		

		
		
	


	




 fired up perfectly the first time, spent a lot of time being anal retentive adjusting the offsets on each channel, all measurements less than 100mV.

 I'm listening to it with my SR-30's right now, pretty damn sweet so far, seems to give a little more weight to the bass compared to the SRD-4 energizer. I don't like to describe sound, but I think it sounds very nice. Great job Alex! Can't wait for my 404's to show up now!_

 

Really nice work on the build. What enclosure did you use??


----------



## TimJo

That looks great Corey. I can't wait. Mine may be done tonight. We'll see...


----------



## ericj

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_You may find that after a few years you regret your decision. I had a 200 series that was not only audible when using open headphones (which just about all stats are) it was actually leaking hum into the audio. You might also find out that the humming/buzzing is enough so that if you have a microphonic tube it affects that as well._

 

I haven't heard the 270dax in my bijou yet.


----------



## runeight

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_My Exstata is alive 
	

	
	
		
		

		
			





 fired up perfectly the first time, spent a lot of time being anal retentive adjusting the offsets on each channel, all measurements less than 100mV.

 I'm listening to it with my SR-30's right now, pretty damn sweet so far, seems to give a little more weight to the bass compared to the SRD-4 energizer. I don't like to describe sound, but I think it sounds very nice. Great job Alex! Can't wait for my 404's to show up now!_

 

A bizarre double post.


----------



## Coreyk78

Thanks for the nice words guys, the enclosure is a Par-Metal 20 series, 12"x12"x4". I have it sitting on top of my Aikido right now which is in a 16"x12"x5" Par-Metal case. My Buffalo will be in a silver case to match the Exstata. My desktop stack will be pretty tall when I'm done, hehe.

 Also my 269JX is completely hum free, and it doesn't get warm at all, plus it was only $40 from Angela.


----------



## TimJo

Trivial question. What is the solder pad next to Q12 (on the hybrid amp) used for? Just noticed it last night...


----------



## runeight

It is a via from top trace to bottom trace. You can leave it alone or fill it in with solder.


----------



## runeight

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_My Exstata is alive 
	

	
	
		
		

		
		
	


	




 fired up perfectly the first time, spent a lot of time being anal retentive adjusting the offsets on each channel, all measurements less than 100mV.

 I'm listening to it with my SR-30's right now, pretty damn sweet so far, seems to give a little more weight to the bass compared to the SRD-4 energizer. I don't like to describe sound, but I think it sounds very nice. Great job Alex! Can't wait for my 404's to show up now!_

 

After you've listened for a few hours check the offsets again to see what they are.

 Also, if you would be so kind, could you please measure T1 to ground and T3 to ground. Let's see what your 269JX is doing.


----------



## Emooze

Beefy, I did a quick search for transformers and didn't really find anything without filaments.

 Let me know if you get a quote on a custom job, I might be interested.


----------



## BoilermakerFan

Since I've changed the case plans for the SS, I'm not restricted in height anymore, so I'll go to Jack at E-P for a custom PSU transformer. I'll keep to spec, no additional secondary windings, so the price will be the same for everyone. Asking for 120V primary, two 240V secondaries @ 65mA each. The the option for 120/240V primary.

 Edit: Nevermind, saw it in the BOM. Too tired from the holiday...


----------



## les_garten

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_Beefy, I did a quick search for transformers and didn't really find anything without filaments.

 Let me know if you get a quote on a custom job, I might be interested._

 

I'm interested in this guy for his R-Cores. He'll do anything you want just about and it's pretty cheap as much as I remember. Plus I was under the impression that R-Core was inherently quieter.

100W R-Core Transformer 115V//230V ,Pre amplifier / DAC - eBay (item 290374357810 end time Dec-25-09 15:04:44 PST)
 Anybody see a reason not to use these?


----------



## BoilermakerFan

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_I'm interested in this guy for his R-Cores. He'll do anything you want just about and it's pretty cheap as much as I remember. Plus I was under the impression that R-Core was inherently quieter.

100W R-Core Transformer 115V//230V ,Pre amplifier / DAC - eBay (item 290374357810 end time Dec-25-09 15:04:44 PST)
 Anybody see a reason not to use these?_

 

That's the one Spritzer linked a while ago. The 230/260 secondaries is the one we would use. I planned to use them for my SS and a Bijou if I build one, but the shipping is high, even with multiple units. They are very nice transformers, Spritzer has used them as have others on diyAudio. 

 The R-Core is quieter and it isn't wide open like a toroid, it has the noise properties of a E-I. I talked to Jack about tooling up for them, but it's about $1K-$2K in tooling. If I had my own design and was planning a production run for commercial release, I'd pursue it with Jack. Any takers?


----------



## jcx

no safety specs?


----------



## les_garten

Quote:


  Originally Posted by *jcx* /img/forum/go_quote.gif 
_no safety specs?_

 

Heh, safety! You want safety from the country that feeds their kidz ground up plastic from the 50's!


----------



## les_garten

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_That's the one Spritzer linked a while ago. The 230/260 secondaries is the one we would use. I planned to use them for my SS and a Bijou if I build one, but the shipping is high, even with multiple units. They are very nice transformers, Spritzer has used them as have others on diyAudio. 

 The R-Core is quieter and it isn't wide open like a toroid, it has the noise properties of a E-I. I talked to Jack about tooling up for them, but it's about $1K-$2K in tooling. If I had my own design and was planning a production run for commercial release, I'd pursue it with Jack. Any takers? 
	

	
	
		
		

		
		
	


	


_

 

I don't know how much this would help, but I'm looking for 4 R-Cores for a few projects. There would be different requirements for them though. One would be for the Hybrid here.


----------



## fierce_freak

Whew, just got done reading all the posts in this thread. Any plans for more boards?


----------



## BoilermakerFan

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_I don't know how much this would help, but I'm looking for 4 R-Cores for a few projects. There would be different requirements for them though. One would be for the Hybrid here._

 

I had inquired about (2) 50W and (2) 100W shipped together or (2) 50W and (4) 100W together, here's the reply:

 If you buy 2 50W & 2 100W , the shipping will be USD86.00 (7.5Kg/Gross)

 If you buy 2 x 50 & 4 x 100W the shipping will be USD116 for shipping.


 I wasn't going custom, just using the 230/260 one with the extra filament windings. Planned to use the 6.3V secondaries in the SS in series, then a voltage doubler to get the voltage up to 18Vdc before regulating it down to 15Vdc for the OptiVols and Phonostage. The 3.15V secondaries would be tied in series and regulated down to 5V and 3.3V for a DAC... So I'd use all the windings and not need a second transformer for the accessories.


----------



## Coreyk78

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_After you've listened for a few hours check the offsets again to see what they are.

 Also, if you would be so kind, could you please measure T1 to ground and T3 to ground. Let's see what your 269JX is doing._

 

I just readjusted the offsets, they had drifted a little, up to around 400-500mV from the 100mV or less I had them set to last night.

 I measured power supply voltages:
 T1 to ground = 330.1V
 T3 to ground = 328.2V


----------



## runeight

All of your voltages are close to perfect.


----------



## runeight

Quote:


  Originally Posted by *fierce_freak* /img/forum/go_quote.gif 
_Whew, just got done reading all the posts in this thread. Any plans for more boards?_

 

I think I have two extra sets of each board type. After that what happens depends on the interest level of the community.


----------



## n_maher

I sorted all of my power supply parts today and started stuffing boards so we should have a few more data points in the near future using the 3XX series Hammond transformer.


----------



## les_garten

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I had inquired about (2) 50W and (2) 100W shipped together or (2) 50W and (4) 100W together, here's the reply:

 If you buy 2 50W & 2 100W , the shipping will be USD86.00 (7.5Kg/Gross)

 If you buy 2 x 50 & 4 x 100W the shipping will be USD116 for shipping.


 I wasn't going custom, just using the 230/260 one with the extra filament windings. Planned to use the 6.3V secondaries in the SS in series, then a voltage doubler to get the voltage up to 18Vdc before regulating it down to 15Vdc for the OptiVols and Phonostage. The 3.15V secondaries would be tied in series and regulated down to 5V and 3.3V for a DAC... So I'd use all the windings and not need a second transformer for the accessories._

 

His shipping does seem a bit high doesn't it?


----------



## Emooze

From hong kong, I'm hoping its air mail or at least something expedited...


----------



## BoilermakerFan

Initial response from Jack at Electra-Print:

 The quote for this power trans is, $56.00 each for 120v pri, $66.00 for the dual primary (same size).

 These would be standard open frame type. other means available. No need for M6 in this one.

 I asked for closed bell end covers to match my other transformers and the physical dimensions. What we actually need is a 480V CT secondary too, so I let him know that and see if the price changes any. But, based on the price quoted, they're smaller than my Hybrid 150 frame.


----------



## awpagan

Runeight

 I've received the pcb's and trannies. 
	

	
	
		
		

		
		
	


	



 also just got some parts from mouser.
 away for work this week, so i'll see how far I get this weekend.

 as for KSC5042 alternatives, how about Sanyo 2SC3675, 2SC4630.
 On paper they look ok, but I havn't tried them yet.


----------



## runeight

Glad they made it.

 The 2SC3675 is a near perfect sub assuming the pinout is the same. the 2SC4630 can't be sub'd because its power dissipation is only 2W.


----------



## scompton

I've finished populating the PS board and I'm half done the amp boards for the sand amp, so I'll be ready to test soon.

 I had one question about layout. Is there any way to arrange the transformers in the sand amp that is bad?


----------



## studeb

Could i have a show of hands?

 How many noticed that Q3 and Q4 are not in the same orientation on the board?

 Good.

 Now how many of you still put one in the wrong way?

 Please don't let me be alone........


----------



## n_maher

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_Could i have a show of hands?

 How many noticed that Q3 and Q4 are not in the same orientation on the board?

 Good.

 Now how many of you still put one in the wrong way?

 Please don't let me be alone........_

 

Bummer man. If it makes you feel better I did make extensive use of the excellent pictures you posted a few pages back. They were quite helpful, thanks.


----------



## studeb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Bummer man. If it makes you feel better I did make extensive use of the excellent pictures you posted a few pages back. They were quite helpful, thanks._

 

Glad to hear they helped. Its all right, a couple of snips and one is now slightly shorter than the rest. Did it with Q1 too. It is what happens when you are watching innane Christmas movies with your family and building at the same time.

 i will put up some sand amp pics tonite, should have it fully stuffed by then.


----------



## sergery

It also happens when you solder later than you should


----------



## runeight

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_Could i have a show of hands?

 How many noticed that Q3 and Q4 are not in the same orientation on the board?

 Good.

 Now how many of you still put one in the wrong way?

 Please don't let me be alone........_

 

Sorry about that. But, there is the silkscreen ... 
	

	
	
		
		

		
		
	


	




 You might want to check the protection zener for Q4 before you fire up again.


----------



## runeight

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_I've finished populating the PS board and I'm half done the amp boards for the sand amp, so I'll be ready to test soon.

 I had one question about layout. Is there any way to arrange the transformers in the sand amp that is bad?_

 

Yes. Anywhere near the input side of the amp board is bad. As you would guess. Other than that, as far away as possible and such that the transformer fields don't radiate easily into the board-to-board or board-to-panel wiring.


----------



## sachu

all too easy to happen ..but never fear..like most Cavalli Audio designs, you'll be able to resurrect it, they are extremely robust.


----------



## studeb

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Sorry about that. But, there is the silkscreen ... 
	

	
	
		
		

		
			





 You might want to check the protection zener for Q4 before you fire up again._

 

i caught it on a visual inspection, so baring a few extra heat cycles all should be well


----------



## runeight

Folks, just some information, a few individuals have PM'd me for the last few boards. I am now out of hybrid board sets and I have two sand sets remaining.

 Also, if there is someone who is interested but does not want to build right now I am willing to part with the sand amp that I built for testing. It works and is burnt in. Just my cost plus shipping.

 Edit: I should clarify that this is not a completed amp, but only the fully populated boards. I am willing to include a 270AX as part of the package.


----------



## runeight

A question, slightly of topic, for those who have been paying more attention. Are the 2SK170/2SJ74 totally unavailable in new production? I know that Toshiba discontinued a while ago, but I haven't followed any further developments. And if so, what does the current stock of them look like at the various sources?


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_A question, slightly of topic, for those who have been paying more attention. Are the 2SK170/2SJ74 totally unavailable in new production? I know that Toshiba discontinued a while ago, but I haven't followed any further developments. And if so, what does the current stock of them look like at the various sources?_

 

For those that don't know, I tend to buy parts in volume. I recently bought 1000 2SK170 and 1000 2SJ74 from a contact in the Far East. He said that he cannot get anymore of these in the original Toshiba packaging. This is telling as he can usually get parts far past when something has been marked out of production. For example, I was able to only get around 200 of the violet grade parts about a year ago and according to him those were the first to be pulled (2SJ74V), as they are very low yield from whatever the production process Toshiba uses.

 I think we have to keep pressuring Linear Systems to release the p-ch parts. There was a group buy that I headed up a while back that netted a $7K order, but even that is peanuts... nevertheless, I still hit up my local distributor here in Austin for Linear Systems every couple months and let them know that "we" (being the DIY community) would be very interested in doing a group buy that could potentially double the last one once the p-ch parts are released... they keep saying "very soon" or something to that effect, and probably is related to seeing what Toshiba does with these parts.

 As for possible availablity, B&D is probably the standard place... Ebay being way to risky. But check what B&D wants for a 2SJ74V, a whopping $6 each.


----------



## sachu

At one point I had bought a few dozen pairs of the JFETs from spencer on diyaudio.com

 But i know he is running low on the J74 and soon will be on the K170 as well.


----------



## runeight

Marc, is Linear producing the nfet?


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Marc, is Linear producing the nfet?_

 

oh yes they are. Single and the dual. I have some if you'd like them...

http://www.linearsystems.com/datasheets/LSK389.pdf

http://www.linearsystems.com/datasheets/LSK170.pdf


----------



## runeight

So they must be getting enough volume to burn their production lines on these. But not the pfets?


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_So they must be getting enough volume to burn their production lines on these. But not the pfets?_

 

I suppose so. I'd have to guess that the tooling to produce the p-ch devices must be quite high. Like I said, I have a feeling that they are waiting to see what Toshiba does. Perhaps they will come out with an improved device? Linear System seems to almost be entirely founded on "direct replacement" devices, as well as doing what they call "All Devices are available with special testing to customer specification", in other words, they can do very tight matching on the devices for the end consumers. I can only expect if an improved device was released, that this wouldn't go over so well with their business model.


----------



## runeight

I see what you mean. Makes it hard to design discrete audio if you need a good set of complementary audio fets.

 Thanks for taking time for my detour.

 How are the builds going gents? Seems like some of you are close?


----------



## pabbi1

Regarding KSC5042, so either the 2sc3675 or 2sc3676 will work, as I have a stash of both?


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_
 How are the builds going gents? Seems like some of you are close?_

 

Received the last of the parts..but feeling too lazy to smell solder fumes tonight. But will get to them soon


----------



## runeight

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Regarding KSC5042, so either the 2sc3675 or 2sc3676 will work, as I have a stash of both?_

 

If I read the datasheets correctly, they are both excellent subs. In fact, I'd recommend the 76 for the hybrid because output fets there get hot as a result of being close to the tubes.

 Edit: the KSC5027 would also be an excellent sub for the follower devices in the hybrid amp.


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I see what you mean. Makes it hard to design discrete audio if you need a good set of complementary audio fets._

 

what about paralleling J271/J310 or even using bipolar devices?


----------



## runeight

Yes, that pair of fets might be close enough if they were Idss matched. The only problem with BJTs will be the input impedance. It won't be as high as fets. Although it may not be low enough to matter.


----------



## studeb

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_How are the builds going gents? Seems like some of you are close?_

 

Here you go, the PS under test:


----------



## BoilermakerFan

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_At one point I had bought a few dozen pairs of the JFETs from spencer on diyaudio.com

 But i know he is running low on the J74 and soon will be on the K170 as well._

 

He is out of the SJ74BLs and I don't think the SJ74Vs measured over 10 IIRC.

 The problem with the available J74/K170 pairs is that they almost all measure under 9mA...

 They're fine for the F5, but won't work in the eXStata. 



 I also received this quote back from Jack for the SS iron:

 "OK, a transformer with 120/120 primary to 480vct @ 65ma is $85.00 each plus shipping.
 The dimensions are, 3" long, 2" wide and 2 1/2" tall, open frame type, the bellend type is 2 3/4" x 2 3/4" x 3" tall"

 I'm confirming, but a single 120V primary should be $75 plus shipping. 

 My resistor order is finally in it's entirety for PRPs, Rikens, Kiwame 2W for the 300K, and big 12W Mills for the 100K B+. I have some Takmans in the order to try too. It might have been a little less, but I ordered parts for (3) F5s and (2) phono stages too and there is a lot of 47R values.


----------



## studeb

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_How are the builds going gents? Seems like some of you are close?_

 

And the amp boards:

 My notes, apart from reversing Q4 and Q1, if you like long legs, its really tight against the heat sinks for some of the Qs.
 The rest was fine. I have the Q11-17 mounted on the heatsinks, but cannot go further tonite.


----------



## studeb

Here are some bent legs and the bent-leg-correcting-device


----------



## studeb

more boards


----------



## runeight

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_And the amp boards:

 My notes, apart from reversing Q4 and Q1, if you like long legs, its really tight against the heat sinks for some of the Qs.
 The rest was fine. I have the Q11-17 mounted on the heatsinks, but cannot go further tonite._

 

Progress!!! 
	

	
	
		
		

		
			





 It would be good to bend the to92s away from any thermal contact with the hardware. I think I mounted mine about 1/2 to 3/4 of that lead length.


----------



## TimJo

Sorry for the delay in an update. Life get in the way sometimes...

 I got my amp board finished over the weekend, and so I just need to power it up - just haven't had the time to do it yet. Want to do one last triple check on parts and orientations before I give it a go.

 I'll try to post some pics. All I can say, is the boards look great.


----------



## Coreyk78

I just ordered some 2SJ74 a few weeks ago for an F5 from tech-diy and they seem to be out of BL grade there since I got GR. I also have some BL grade that I got from Tubeshunter off ebay, which as far as ebayers from China go he seems to be one of the best, I haven't had a chance to compare them visually to see if the pieces from China are genuine or fakes. The 2SK170 seem to be easier to find.


----------



## TimJo

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Progress!!! 
	

	
	
		
		

		
		
	


	




 It would be good to bend the to92s away from any thermal contact with the hardware. I think I mounted mine about 1/2 to 3/4 of that lead length._

 

I see what you mean about Q9 on the hybrid boards as well. Mine are positioned with only the top third of the device next to the heatsink, but they are very close together (but no contact). Should I try to fix this before I go any further?


----------



## TimJo

Here are a few quick pics of the boards on my test jig.


----------



## runeight

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_I see what you mean about Q9 on the hybrid boards as well. Mine are positioned with only the top third of the device next to the heatsink, but they are very close together (but no contact). Should I try to fix this before I go any further?_

 

They are very close, but as long as they are not touching the heatsink hardware that's ok.

 Where did you get the black tube sockets?


----------



## Beefy

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_I just ordered some 2SJ74......_

 

I don't like to ask for % differences, because that is pretty meaningless...... but I guess the key question to all knowledgeable parties, what benefit would chasing up these obsolete JFETs provide?

 Are talking night and day? Dawn and dusk? Or is it mostly just technical masturbation?


----------



## pabbi1

My matched 2sj74 from HK and Taiwan (3x at this point) have all been in the 8-9 range, but ALL less that the magical 10 threshhold, even when matched to the mV. So, YMMV, but it seems less than advertised for our purposes.


----------



## Beefy

I realise that the Idss is related to the transconductance which determines the amp's gain - but is having a gain of 1000x all that critical? The amp will clip WELL before you hit that from most 2VRMS sources.

 I suppose it _may_ be important for less hot sources or quietly recorded classical music......


----------



## runeight

A gain of 1000 it a bit arbitrary I think. A good number to target: 1V in = 1000V out.

 But it is not strictly necessary to have this gain and less gain for the most part should not make much difference. You just turn up the volume and since the gain is linear the low passages get louder too.

 However, the less gain there is in the amp the more signal it needs at the front end and the more signal into diff pair the higher the distortion. This particular design was a trade-off to try to achieve ericj's design goals while still getting good SQ.

 All this to say that the target of 1000 is a good point for this amp to work at given the trade-offs that it is making.

 And, I should add, every amp that I have ever seen makes design trade-offs, one way or another.


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_However, the less gain there is in the amp the more signal it needs at the front end and the more signal into diff pair the higher the distortion._

 

Excellent, that clears things up a lot in my mind 
	

	
	
		
		

		
			





 So I guess the question again is, if we did make this trade off for these super-duper obsolete JFETs - but with lower Idss - what sort of improvements or decreases can we expect?

 Without changing the design entirely, are the 2SJ74 actually going to be any better than the J271? At least on a technical level......


----------



## Coreyk78

So I have a question about something I tried last night.

 I have both XLR and RCA inputs on my amp, and I used a switch to short pin 1 and pin 3 when using the RCA input which is the same as jumpering -IN to GND at the board. I did it this way because I had a DPDT switch handy and I will only have 1 source connected at a time.

 I have it wired exactly the same as the inputs on my Aleph-J speaker amp which also has differential input. Only difference being that I have a 4-gang pot in the exstata and none in the Aleph. I notice a large difference in gain when I flip the switch on my Aleph, Pin1 and 3 shorted I have full gain, pin1 and 3 not shorted it is a lot quieter.

 On the Exstata however I can't hear any difference at all running from RCA inputs when I flip the switch. I verified that the -IN is being shorted to ground with a meter when the switch is closed and left open when the switch is open so that part is working. 

 I'm just wondering how much difference in gain it really makes on this amp running single ended with -IN left floating. Only curious, it seems to work fine regardless.


----------



## studeb

all this talk of Aleph and F5 has got me wondering, is there something about this amp that sucks in people from PassDIY? Am i in head-fi or in a Pass Labs forum?

 its wierd, my next build was going to be an F5, but this came up.

 Boilermakerfan, what phono stage are you building?


----------



## runeight

Beefy, MHO is that the fancy Toshiba fets are not necessary for this amp. Which is one reason we used the J271s. If you notice a difference, other than gain, I'll be interested. 
	

	
	
		
		

		
		
	


	




 Coreyk78, you may remember our earlier conversation about this. So this time I'll try to be more precise.

 The gain of the amp doesn't change when you short the negative input. But, here's what I meant earlier in the thread.

 Let's say you're feeding a balanced signal with 600mV peak to peak (that's 300mV per side). If the amp has a gain of 1000 you'll get 600V peak to peak at the outputs.

 Now if you feed it with an SE signal from only half the balanced signal you'll be pushing 300mV into one of the inputs with the other grounded. The amp's gain is still 1000 but you'll only get 300V peak to peak at the output. So while the gain hasn't really changed, to you it will feel like half the gain is gone.

 However, if you feed a 600mV peak to peak SE signal then the amp will produce 600V at its output although with slightly higher distortion than with a balanced signal.

 So, it's hard to know what exactly you are experiencing between the two amps as it depends on several factors in the mix.


----------



## Coreyk78

Runeight, that makes perfect sense to me, I didn't use the correct terms in my post. I should have said I notice a difference in output level with the Aleph when using SE inputs and having -IN grounded or not. I don't notice the same kind of difference with the Exstata. I'm not worried about it, I was just wondering why, 'nuff said


----------



## luvdunhill

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_My matched 2sj74 from HK and Taiwan (3x at this point) have all been in the 8-9 range_

 

again, what voltage is this measured at? That's very important when claiming these Idss numbers. It's easy enough to accommodate for smaller or large Idss. That brings me to the point, I'm not sure why we are comparing Idss here anyways, isn't >Yfs and <En the important parameter here? Yes they are related, but not comparable across different model numbers..


----------



## runeight

Within reason, because the jfet curves are flat after turn-on, the Idss should be fairly constant. But not completely so, thus the voltage does matter.

 You are absolutely correct about the Yfs. It is the more important parameter, but not as easy to measure. Hence the simple matching of Idss in the hope of getting decent, but not as good, Yfs matches.


----------



## wiatrob

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Excellent, that clears things up a lot in my mind 
	

	
	
		
		

		
		
	


	



 Without changing the design entirely, are the 2SJ74 actually going to be any better than the J271? At least on a technical level......_

 

I have heard both in the proto amp - can't tell the difference, SQ wise. Could be my tin ears...


----------



## runeight

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_Runeight, that makes perfect sense to me, I didn't use the correct terms in my post. I should have said I notice a difference in output level with the Aleph when using SE inputs and having -IN grounded or not. I don't notice the same kind of difference with the Exstata. I'm not worried about it, I was just wondering why, 'nuff said 
	

	
	
		
		

		
		
	


	


_

 

Oh. This depends, I think, on how the inputs of the Aleph are terminated. In the exstata there is a 1M gate resistor that keeps the gates grounded (or nearly so) when signal is applied to the other gate. Hence the exstata doesn't change much if the unused input is forcibly grounded or not.

 The Aleph may have a different scheme on how this input is grounded and if it is allowed to float (hard to believe) it could affect the signal amplitude. At least that's my theory.


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Within reason, because the jfet curves are flat after turn-on, the Idss should be fairly constant. But not completely so, thus the voltage does matter.

 You are absolutely correct about the Yfs. It is the more important parameter, but not as easy to measure. Hence the simple matching of Idss in the hope of getting decent, but not as good, Yfs matches._

 

Good, now we can stop comparing Idss across different JFET models 
	

	
	
		
		

		
		
	


	




 Case in point:

http://www.fairchildsemi.com/ds/J1/J174.pdf

 minimum Idss is -20mA max is -100mA.

 edit: The J271 isn't very flat. IIRC, between 9V and 12V Idss varies 2-3mA?


----------



## runeight

Yes, we can stop talking about it. The other reason for the Idss match is so that the balance control has enough range to zero the balance at the output. If the Idss of the fets is too far off there won't be enough range in the trimpot.

 Now, we can really stop talking about it.


----------



## Beefy

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I have heard both in the proto amp - can't tell the difference, SQ wise. Could be my tin ears..._

 

That is exactly the sort of experience I was hoping for. Thanks! 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes, we can stop talking about it. The other reason for the Idss match is so that the balance control has enough range to zero the balance at the output. If the Idss of the fets is too far off there won't be enough range in the trimpot.

 Now, we can really stop talking about it. 
	

	
	
		
		

		
		
	


	


_

 

I'm sorry that I keep asking about it 
	

	
	
		
		

		
		
	


	




 I just find the design process quite fascinating, and always try to learn as much as I can about a design and its components before I start.....


----------



## runeight

Oh. Then we can keep talking. 
	

	
	
		
		

		
		
	


	




 The Idss match on the fets helps to keep their operating points as close as possible. The balance trimpot adjusts the source voltages on the differential pair and the closer the Idss match the closer will be the source voltages (assuming that the rest of the circuit is not seriously out of whack). In my first build I tested this by just grabbing two random fets from the bag. It was not possible to balance either channel because the fets were too far apart. I thought this might be the case and so we established the 10% Idss matching.

 The transconductance, OTOH, is really an AC parameter and it determines the gain of the jfets in the diff pair. There are two important pieces to this.

 This first is that the better the transconductances match at the operating point the better gain equality there will be in each half of a single channel. If the transconductances are really far apart than one side will swing higher than the other. And there isn't really enough feedback to handle this.

 The second is that in order to get our gain goal of 1000 we need the higher transconductance devices because all of the gain in the amp resides in the diff amp. There is no additional gain stage. This was one of the simplifications I made in order to meet the design goals.

 It won't kill anything to use lower transconductance devices, but the gain will be lower. Using Idss >10mA does not really guarantee that the transconductance will be fantastic. But it loosely correlates and is an easy DC matching measurement.

 These are the reasons we played with the jfets at the beginning of the process, but then just settled in on a convenient matching scheme that gets us close but not perfect.


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Using Idss >10mA does not really guarantee that the transconductance will be fantastic. But it loosely correlates and is an easy DC matching measurement_

 

What about this, for the more advanced students 
	

	
	
		
		

		
		
	


	




 In addition to the 12V supply you guys are already using, you could take a 9V battery and strap a 10K trimmer across that and use it to vary Vgs. Then, adjust the trimmer until you get say 10mA Id then write down the Vgs measurement at that point. Then group by Vgs.

 Oh Beefy, this is a good place to start learning more about JFETs:

http://www.borbelyaudio.com/adobe/ae599bor.pdf


----------



## runeight

This would be tidier. And since the fets are running at 1mA in the amp, just match them at 1mA instead of 10mA.


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_This would be tidier. And since the fets are running at 1mA in the amp, just match them at 1mA instead of 10mA._

 

I just kept the 10mA because it's supposedly magic number 
	

	
	
		
		

		
			





 Don't ruin the magic! (Yeah, that's the idea though)

 I actually have started matching power MOSFETs this way that are paralleled in class A output stages. So, in this case I have a 15V supply and set the current to right around 2A with my little 9V battery trimmer (which settles in around 2.5V for this particular Toshiba MOSFET). The trick then is keeping the devices at the same measuring temperature. To do that, I use an "un-heatsink" which is a block of solid aluminum. I drilled a small hole above the device to insert a temperature probe. Then I wait until the block is around 55C and take the Vgs measurement. Then try to keep moving so the block is around the same temperature, and the same torque is used to fasten the device. The process works well, I can get very good matches this way, albeit a little bit unconventional. You really do need accurate meters though, both to measure the current and to measure the final Vgs voltage.

 Anyways, back to the builds!


----------



## Beefy

Good stuff lads 
	

	
	
		
		

		
		
	


	




 A-reading I will go......


----------



## HeadphoneAddict

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I have heard both in the proto amp - can't tell the difference, SQ wise. Could be my tin ears..._

 

So, how is the most recent version coming along so far?


----------



## runeight

wiatrob has been goofing off lately. Don't bug him.


----------



## Coreyk78

Got my SR-404 today 
	

	
	
		
		

		
		
	


	






 Its fun to say the least


----------



## pabbi1

OK, ok, I'll get a 12v battery and remeasure... 
	

	
	
		
		

		
		
	


	




 A couple of questions - what about off board caps for the psu - possible bad? And, can I sub a 50ohm trimpot for P1,P2?

 And, isn't either the mpsa42 or mpsa92 PNP, as both are listed NPN on the 100.d BOM...


----------



## runeight

No, no off board caps please. Bad. 
	

	
	
		
		

		
		
	


	




 50R trimpots are ok. I had to use these on the beta build that I made.

 Good catch on the BoM. MPSA92 is PNP.


----------



## runeight

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_Got my SR-404 today 
	

	
	
		
		

		
		
	


	






 Its fun to say the least 
	

	
	
		
		

		
		
	


	


_

 

Is there any way we could entice you to say more??


----------



## Coreyk78

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Is there any way we could entice you to say more?? 
	

	
	
		
		

		
		
	


	


_

 

Well for starters I think my dynamic phones are going to be collecting dust for a while, the Exstata and the 404s sound fantastic together. I've been going through a lot of my favorite music and it sounds the best it ever has. I listened to some classical and I could hear everything like I was in the room, the creak of a chair, the musicians turning pages, incredible detail. Even listened to some house music and it was like being in the club, just tons of fun. I've read some comments that stats are bass shy but I have no complaints. Rock, classical, jazz, electronic, whatever It is I think this is going to be my go to setup for a looong time. 
 I am going to need to be careful with the volume though, everything sounds so clean that you don't realize just how loud it really is


----------



## BoilermakerFan

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_all this talk of Aleph and F5 has got me wondering, is there something about this amp that sucks in people from PassDIY? Am i in head-fi or in a Pass Labs forum?

 its wierd, my next build was going to be an F5, but this came up.

 Boilermakerfan, what phono stage are you building?_

 

Well, look at my sig... I'm pretty much limiting what I build to designs by those six great guys and they're are still too many amps to build and they keep cranking out new designs. 
	

	
	
		
		

		
		
	


	




 But seriously though, the F5 met my requirements of a powerful SS amp to complement the eXStata SS. My only other requirement was that it was not a B22. The fact that it will run as two SE amps with headphones or be 50W Class A for speakers is just the perfect icing on great cake. 

 Phonostage is Peter Daniel's AudioSector design, using OPA627BP then OPA637BP. You can build it insanely expensive with Caddocks, BGs, and V-Caps, or go more reasonable with a couple BG STDs, Nichion FGs, Silmic IIs, Holco, Takman or Panasonic resistors and Vishay film caps. 

  Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_Well for starters I think my dynamic phones are going to be collecting dust for a while, the Exstata and the 404s sound fantastic together. I've been going through a lot of my favorite music and it sounds the best it ever has. I listened to some classical and I could hear everything like I was in the room, the creak of a chair, the musicians turning pages, incredible detail. Even listened to some house music and it was like being in the club, just tons of fun. I've read some comments that stats are bass shy but I have no complaints. Rock, classical, jazz, electronic, whatever It is I think this is going to be my go to setup for a looong time. 
 I am going to need to be careful with the volume though, everything sounds so clean that you don't realize just how loud it really is 
	

	
	
		
		

		
		
	


	


_

 

Very nice. 

 I just caught that your in Minneapolis. I flew in Monday and I'm sitting in my hotel room in Burnsville after driving all over town today; up to Arden Hills, out to Delano, back to Roseville, and then back down to Burnsville. I lived in Burnsville 10 years ago so it's fun to be back in my stompin' grounds. I'm flying out a day early tomorrow morning though because two other calls fell through. 

 It's not cold enough yet and I'm a glutton for punishment so I'll be back up in mid-to-late January or February.


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_wiatrob has been goofing off lately. Don't bug him. 
	

	
	
		
		

		
		
	


	


_

 


 Har. I have five boards in front of me, getting stuffed. This 'ghost building' isn't all it's cracked up to be. 

 I have had some extra constraints on my time and resources lately. Good thing I've built this amp like 4 times already. 
	

	
	
		
		

		
		
	


	




 Larry, I'll update you daily.


----------



## wiatrob

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_I am going to need to be careful with the volume though, everything sounds so clean that you don't realize just how loud it really is 
	

	
	
		
		

		
		
	


	


_

 

Congrats. You will notice that all the Stax Folk listen at *exceedingly *loud volume levels - which is why I think they're driving some of the earlier designs to clip. 

 Come to think of it, this was not mentioned in the original requirements


----------



## BoilermakerFan

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Har. I have five boards in front of me, getting stuffed. This 'ghost building' isn't all it's cracked up to be. 

 I have had some extra constraints on my time and resources lately. Good thing I've built this amp like 4 times already. 
	

	
	
		
		

		
		
	


	


_

 

You want to ghost build my two for me too? I'm using boutique parts so mine will be more fun to build. Yeah, that's the ticket!

 I'll take one of those "other" or "extra" constraint builds too.


----------



## Emooze

gents and ladies, had school not got in the way (again) I would have had my power supply up and tested this evening. I should have mine running tomorrow evening at some point and then I'll begin populating the amp boards.


----------



## BoilermakerFan

I have the green screw terminals like Emooze, but I prefer the black or blue ones others have used. Can any one give me parts numbers from Mouser or Digi-Key for them?


----------



## Emooze

They make black ones? Why was I not informed of this!


----------



## runeight

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_Well for starters I think my dynamic phones are going to be collecting dust for a while, the Exstata and the 404s sound fantastic together. I've been going through a lot of my favorite music and it sounds the best it ever has. I listened to some classical and I could hear everything like I was in the room, the creak of a chair, the musicians turning pages, incredible detail. Even listened to some house music and it was like being in the club, just tons of fun. I've read some comments that stats are bass shy but I have no complaints. Rock, classical, jazz, electronic, whatever It is I think this is going to be my go to setup for a looong time. 
 I am going to need to be careful with the volume though, everything sounds so clean that you don't realize just how loud it really is 
	

	
	
		
		

		
			



_

 

Thanks. As the designer it helps to know if we're succeeding in making a good amp. I think I'll have to ask for some stats for Christmas.


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Thanks. As the designer it helps to know if we're succeeding in making a good amp. I think I'll have to ask for some stats for Christmas. 
	

	
	
		
		

		
		
	


	


_

 

alright already..third time calling for the hat to be passed around..An ESP950 for Alex would be awesome, i do believe the exstata pairing with the ESP950 is one of the best..if there is general agreement we can start a thread.


----------



## Coreyk78

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Very nice. 

 I just caught that your in Minneapolis. I flew in Monday and I'm sitting in my hotel room in Burnsville after driving all over town today; up to Arden Hills, out to Delano, back to Roseville, and then back down to Burnsville. I lived in Burnsville 10 years ago so it's fun to be back in my stompin' grounds. I'm flying out a day early tomorrow morning though because two other calls fell through. 

 It's not cold enough yet and I'm a glutton for punishment so I'll be back up in mid-to-late January or February. 
	

	
	
		
		

		
		
	


	


_

 

Its been an exceptionally mild Fall here this year, I've barely had to scrape my car windows in the morning yet. Hopefully when you come back this winter we'll have some nice sub-zero weather to welcome you hehe 
	

	
	
		
		

		
		
	


	




 I'm actually living back in Farmington now where I grew up, about 15 miles or so southeast of Burnsville, but I still work in Minneapolis.


----------



## ericj

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I have the green screw terminals like Emooze, but I prefer the black or blue ones others have used. Can any one give me parts numbers from Mouser or Digi-Key for them?_

 

The blue 2-position terminals i used for heaters were purchased locally, from a vendor that doesn't exactly fill me in on part numbers. And somewhat cheezy quality. They work but with less confidence than the phoenix parts. 

 they look exactly like these: 

http://www.allelectronics.com/make-a...L-STRIP/1.html

 Notice how the construction has you driving a screw down to push a little metal strap against whatever you shoved in there, as compared to drawing up a little box that traps the wire as in the phoenix terminal. 

 come to think of it, I don't think y'all actually saw those . . . .


----------



## pabbi1

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Congrats. You will notice that all the Stax Folk listen at *exceedingly *loud volume levels - which is why I think they're driving some of the earlier designs to clip. 

 Come to think of it, this was not mentioned in the original requirements 
	

	
	
		
		

		
		
	


	


_

 

Well, yeah... doh! Forgot to mention 'Tool' in the original spec also, but have made that a future request. 
	

	
	
		
		

		
		
	


	




 And, i'd like to point out the only stats Alex has heard, to my knowledge, are the he60 and OII... and he can speak to which he preferred.


----------



## TimJo

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Oh. Then we can keep talking. 
	

	
	
		
		

		
		
	


	


_

 

 Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_What about this, for the more advanced students 
	

	
	
		
		

		
		
	


	




 In addition to the 12V supply you guys are already using, you could take a 9V battery and strap a 10K trimmer across that and use it to vary Vgs. Then, adjust the trimmer until you get say 10mA Id then write down the Vgs measurement at that point. Then group by Vgs.

 Oh Beefy, this is a good place to start learning more about JFETs:

http://www.borbelyaudio.com/adobe/ae599bor.pdf_

 

 Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_This would be tidier. And since the fets are running at 1mA in the amp, just match them at 1mA instead of 10mA._

 

 Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_I just kept the 10mA because it's supposedly magic number 
	

	
	
		
		

		
		
	


	




 Don't ruin the magic! (Yeah, that's the idea though)

 I actually have started matching power MOSFETs this way that are paralleled in class A output stages. So, in this case I have a 15V supply and set the current to right around 2A with my little 9V battery trimmer (which settles in around 2.5V for this particular Toshiba MOSFET). The trick then is keeping the devices at the same measuring temperature. To do that, I use an "un-heatsink" which is a block of solid aluminum. I drilled a small hole above the device to insert a temperature probe. Then I wait until the block is around 55C and take the Vgs measurement. Then try to keep moving so the block is around the same temperature, and the same torque is used to fasten the device. The process works well, I can get very good matches this way, albeit a little bit unconventional. You really do need accurate meters though, both to measure the current and to measure the final Vgs voltage.

 Anyways, back to the builds!_

 

Thanks for the discusion guys. This is the main reason I like to check in every day. 
	

	
	
		
		

		
		
	


	




 After all, other than Alex, am I the only one who's building the amp and doesn't even own stats yet?


----------



## BoilermakerFan

Nope. I have Kabeer's 950s here on loan, but I do not actually own a pair yet. I have a pair of vintage electrets that I need to mod as their transformers are built into the ear cups. I'll start with 950s once I sell off my dynamics except for the K401s and K141s.


----------



## scompton

Does anyone know what size tap I need to tap the heat sinks?


----------



## wiatrob

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I have a pair of vintage electrets that I need to mod as their transformers are built into the ear cups._

 

I have a pair of Sr-40s I use to 'smoke test' with - they actually sound pretty good. is that heresy?


----------



## BoilermakerFan

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_Does anyone know what size tap I need to tap the heat sinks?_

 

It should be a 4-40, but let me check on the morning...


----------



## scompton

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I have a pair of Sr-40s I use to 'smoke test' with - they actually sound pretty good. is that heresy? 
	

	
	
		
		

		
		
	


	


_

 

I have SR-30s and SR-40s. The SR-30s sound pretty good. The SR-40s have static in one ear from a bad wire. My AT electrets sound pretty good too.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_alright already..third time calling for the hat to be passed around..An ESP950 for Alex would be awesome, i do believe the exstata pairing with the ESP950 is one of the best..if there is general agreement we can start a thread._

 

I think a SR-Lambda normal bias might be a better choice and a more attainable goal, but I'd chip in for whatever if someone sets things up for a collection. SR-Lambda sounded quite good with the 1st prototype at RMAF. Even an SR-003 would be a good option for this amp.


----------



## wiatrob

This is slightly OT - I'm going to go out on a limb here - I think what Alex would like more than a pair of stats is for people to build and objectively review these amps, in their own words, on their own rigs. 

 I've known Alex for a while now and he loves designing amps. He does that for this community, and the best way to show appreciation is to listen and provide feedback on the designs. 

 That was one of the original purposes of this beta period, along with flushing any possible problems the proto team didn't find.

 Build those amps!


----------



## wiatrob

And, on another note - If I have to Tombstone *ONE MORE @^%#%@ component*, postal!!


----------



## wiatrob

Sand Beta is up. This board is a brick with all those sinks. No Oscillation. Dead quiet w/ no input.

 "Listening to Rock n Roll Ain't Noise Pollution" on the SR-40s. Too late for comparo or detailed impressions, but it's tight on the bottom and fast, something it shares with my follower modded proto. Actually bringing these old $28 SR-40s to life...

 I'll break out the Tool and some 'stats tomorrow.

 Bodes well for those 'ghostbuilds' 

 Nice Job Alex!


----------



## HeadphoneAddict

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Sand Beta is up. This board is a brick with all those sinks. No Oscillation. Dead quiet w/ no input.

 "Listening to Rock n Roll Ain't Noise Pollution" on the SR-40s. Too late for comparo or detailed impressions, but it's tight on the bottom and fast, something it shares with my follower modded proto. Actually bringing these old $28 SR-40s to life...

 I'll break out the Tool and some 'stats tomorrow.

 Bodes well for those 'ghostbuilds' 

 Nice Job Alex! 
	

	
	
		
		

		
		
	


	


_

 

Congrats - my son still likes his SR-30 (free) and SR-84 ($40), but the SR-Lambda is still better.


----------



## Beefy

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_Does anyone know what size tap I need to tap the heat sinks?_

 

4-40 or M3.


----------



## n_maher

Quick question/comment: anyone found a good (preferably easy) way to remove the pins from the stock heat sinks? I'm assuming that there wasn't an option for sinks without the pins. I hate pins. 

 In other news, I got one power supply 90% stuffed last night and all that's left to do there is get the heat-sink mounted components on.


----------



## Beefy

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I'm assuming that there wasn't an option for sinks without the pins. I hate pins._

 

These Aavid sinks are a pinless replacement for the Wakefield 637-20ABP.

 But I couldn't find a pinless version of the larger sinks.


----------



## Coreyk78

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Quick question/comment: anyone found a good (preferably easy) way to remove the pins from the stock heat sinks? I'm assuming that there wasn't an option for sinks without the pins. I hate pins. 

 In other news, I got one power supply 90% stuffed last night and all that's left to do there is get the heat-sink mounted components on._

 

I used a vice grip clamped on really tight and just used a counter-clockwise twisting/pulling motion and they came out pretty easy. At least that worked for the smaller sinks, the bigger ones seem to have pins that are much more brittle and I snapped off the first one I tried to pull. I only screw mounted the smaller sinks with one FET on them because I didn't want it to be able to flop around, the bigger sinks with 2 devices seem to be pretty secure with just the component legs so I figured it wouldn't be worth the hassle of snapping off more of those pins.


----------



## BoilermakerFan

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Quick question/comment: anyone found a good (preferably easy) way to remove the pins from the stock heat sinks? I'm assuming that there wasn't an option for sinks without the pins. I hate pins. 

 In other news, I got one power supply 90% stuffed last night and all that's left to do there is get the heat-sink mounted components on._

 

If you have a good hot mitt and your oven can be set low enough, put them in the oven at 175-200. Hold it with the hot mitt and use the vise grips. I ordered pin-less for the MHMs long ago, but all of the bigger sinks are pinned. 

 The good news is that the hole is the pilot size for a 4-40 tap, so you just have to run the tap in and not drill it first.


----------



## n_maher

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_I used a vice grip clamped on really tight and just used a counter-clockwise twisting/pulling motion and they came out pretty easy. At least that worked for the smaller sinks, the bigger ones seem to have pins that are much more brittle and I snapped off the first one I tried to pull. I only screw mounted the smaller sinks with one FET on them because I didn't want it to be able to flop around, the bigger sinks with 2 devices seem to be pretty secure with just the component legs so I figured it wouldn't be worth the hassle of snapping off more of those pins._

 

I too have used the vice grip method and I guess my luck must be worse since I'd say ~90% of the pins snapped when I did that. I then had to drive the pins out using a hammer and screw driver. Not fun. Hopefully the small sinks will give up their pins as easily for me as they did for you.

 Personally I would be at all comfortable with any component supporting a heat sink so I'll be removing all of them, drilling, tapping and securely mounting the heat sink prior to soldering the component legs so that there's as little stress on the solder joint as possible. I've seen unsecured sinks snap off three legged TO-220 devices before and it's not pretty.


----------



## BoilermakerFan

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I too have used the vice grip method and I guess my luck must be worse since I'd say ~90% of the pins snapped when I did that. I then had to drive the pins out using a hammer and screw driver. Not fun. Hopefully the small sinks will give up their pins as easily for me as they did for you.

 Personally I would be at all comfortable with any component supporting a heat sink so I'll be removing all of them, drilling, tapping and securely mounting the heat sink prior to soldering the component legs so that there's as little stress on the solder joint as possible. I've seen unsecured sinks snap off three legged TO-220 devices before and it's not pretty._

 

I have a nail set that is just about the perfect diameter and pretty long too, it's long enough to reach the top of the pins. It's a Sears brand. You might be able to find one and use that to knock those broken pins out. Heating the sinks will help too. You can use thick leather to protect the sink from a big cast iron vise and not have to worry about the plastic melting.


----------



## Beefy

Couple of things...... First, J271's are back in stock at Mouser. Huzzah!

 Second, I was thinking of getting a quote from SumR for the following custom toroidal transformer for SS builds...

 Primary: 2x 115V, 50/60Hz
 Secondary: 2x 240V, 62.5mA (this is 15VA per secondary winding, 30VA total, so should be a standard toroid core)
 Fully potted and shielded.

 Can anybody suggest any improvements?


----------



## luvdunhill

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_ I've seen unsecured sinks snap off three legged TO-220 devices before and it's not pretty._

 

worse-case, turn them upside down and drill a new hole to attach the device to.


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Couple of things...... First, J271's are back in stock at Mouser. Huzzah!

 Second, I was thinking of getting a quote from SumR for the following custom toroidal transformer for SS builds...

 Primary: 2x 115V, 50/60Hz
 Secondary: 2x 240V, 62.5mA (this is 15VA per secondary winding, 30VA total, so should be a standard toroid core)
 Fully potted and shielded.

 Can anybody suggest any improvements?_

 

Yes, the secondary should be 480VCT instead of the two separate windings... An EI core will not let as much noise through as a toroid. 

 Also, I have one quad of the matched J271s that I will not be using in my eXStata SS, so if you want them, I'll sell them to you at the cost that was passed on to us by Bill and Alex. I just have to find out from Alex what that actually was.


----------



## Beefy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Yes, the secondary should be 480VCT instead of the two separate windings..._

 

Connect the end of one winding to the start of the other - instant centre tap.

  Quote:


 An EI core will not let as much noise through as a toroid. 
 

I'm not really worried about line noise so much as magnetic field from the transformer in my rack. And I use IEC filters in all of my builds as well.

  Quote:


 Also, I have one quad of the matched J271s that I will not be using in my eXStata SS, so if you want them 
 

Thanks, but I'll be right


----------



## les_garten

BoilermakerFan;6203492 said:
			
		

> If you have a good hot mitt and your oven can be set low enough, put them in the oven at 175-200. Hold it with the hot mitt and use the vise grips. I ordered pin-less for the MHMs long ago, but all of the bigger sinks are pinned.
> 
> The good news is that the hole is the pilot size for a 4-40 tap, so you just have to run the tap in and not drill it first.[/QUOTlanE]
> 
> Sounds like a good plan for a Hair Dryer or Heat Gun as well.


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Connect the end of one winding to the start of the other - instant centre tap.

 I'm not really worried about noise so much as magnetic field from the transformer in my rack.

 Thanks, but I'll be right 
	

	
	
		
		

		
			



_

 

I'm not a trafo expert by any stretch, but I had asked Jack for the dual windings and he said the way he winds, a true CT secondary would yield better performance. I left it at that and let him quote me the CT.

 If you can post up the dimensions and price I would be interested in the shielded version. I was going to shield the E-P in my build... I'm going to need a 1000VA dual 18Vac secondaries toroid for my F5 too so I was going to get a quote from them for that beast. 

 No problem.


----------



## studeb

I have the amp boards stuffed, with a wave of my magic wand several of the long legged beasts shrunk. They were not in contact with the sink, just close to the mounting screw. I will post pics this evening, but i think the last ones were just missing the KSC5024s anyways.

 Wiatrob, how did you check for oscillation?

 Alex, would the PS be happy with just one channel connected?

 Another build note, even if you do not like screw terminal connections, at least use one for the +/- 300 and Gnd out of the PS. It seems to be the only way to get two wires off of those pads.


----------



## Beefy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_If you can post up the dimensions and price I would be interested in the shielded version._

 

If it does end up being a standard 30VA unit, I can tell you right now that a fully shielded and encapsualted SumR jobbie would probably be 94mm wide, 110mm long and 50mm high. I've already bought 3 30VA units for other builds; they were $61 each for off-the-shelf 2x9/12/15VAC secondaries, so you can expect to pay more than than that for a custom secondary config.


----------



## Beefy

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_Alex, would the PS be happy with just one channel connected?_

 

You HAVE to have a load of some sort, otherwise the whole CCS current will flow through the shunt and you will fry the shunt transistors. If you don't have an amp board connected, keep the load resistors in there!


----------



## les_garten

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_You HAVE to have a load of some sort, otherwise the whole CCS current will flow through the shunt and you will fry the shunt transistors. If you don't have an amp board connected, keep the load resistors in there!_

 

I think he's talking about just the L or R channel? Most likely for testing the boards as they are built.


----------



## studeb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_You HAVE to have a load of some sort, otherwise the whole CCS current will flow through the shunt and you will fry the shunt transistors. If you don't have an amp board connected, keep the load resistors in there!_

 

i know, i am just not enough of an EE to be sure that one channel is enough of a load

 And Les is right i was going to power them up one at a time.


----------



## runeight

One channel is not enough of a load for the PS. You could run maybe one or two mintues befure the shunt bjts got too hot for their heatsinks.

 The amps, if they are built right, will come up properly and you can bring them up at the same time without worry.

 Just be sure the ground all four of the small heatsinks for the CCSs and you won't have oscillation. If it is oscillating your DMM will flake out and not even be able to take DC measurements at the output pins.


----------



## Beefy

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_i know, i am just not enough of an EE to be sure that one channel is enough of a load

 And Les is right i was going to power them up one at a time._

 

Yeah, I had a total brain fart. It clicked as I was walking away from my computer to the lab


----------



## luvdunhill

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_a true CT secondary would yield better performance. I left it at that and let him quote me the CT._

 

This is true. The fewer windings and gap in said windings the better. However, sometimes the convenience of a dual primary and separate secondary windings is worth it. I'd go separate windings myself if I was doing a custom job.


----------



## Beefy

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_This is true. The fewer windings and gap in said windings the better._

 

What sort of differences are we talking about here? I imagine it would primarily be in the overall efficency, but am mostly just guessing......


----------



## n_maher

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_worse-case, turn them upside down and drill a new hole to attach the device to._

 

I've had bad luck recently with hand-drilled holes tearing isolation pads so my preference is definitely to use the stock hole but I'd thought of the flip-it, drill-it routine too. That strikes me as even more painful than pulling the pins.


----------



## runeight

I swear I will not talk about transformers. I swear I will not talk about transformers. I swear ...


----------



## luvdunhill

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_What sort of differences are we talking about here? I imagine it would primarily be in the overall efficency, but am mostly just guessing......_

 

I'm not sure about efficiency. I was thinking more along the lines of leakage, but perhaps the shielding would mitigate that? It's more work for the winder I'd guess as well.

 Nate: post deburring tool?!


----------



## Beefy

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_I'm not sure about efficiency. I was thinking more along the lines of leakage, but perhaps the shielding would mitigate that? It's more work for the winder I'd guess as well._

 

Thanks


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I swear I will not talk about transformers. I swear I will not talk about transformers. I swear ... 
	

	
	
		
		

		
		
	


	


_

 

Well then, we can talk about inductively coupled conductors, magnetic flux and EMF instead. 

 I think the only left is to discuss the merits or faults of boutique resistors. Of course, if the design didn't limit the effects of tube rolling, that could have been a good 20 page running discussion too.


----------



## n_maher

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Nate: post deburring tool?! 
	

	
	
		
		

		
			



_

 

I don't think the deburring tool can really help on a .1" diameter hole.


----------



## runeight

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Well then, we can talk about inductively coupled conductors, magnetic flux and EMF instead. 

 I think the only left is to discuss the merits or faults of boutique resistors. Of course, if the design didn't limit the effects of tube rolling, that could have been a good 20 page running discussion too. 




_

 

The only thing I can think of to say is: thank goodness there are no capacitors in the amps.


----------



## luvdunhill

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_ if the design didn't limit the effects of tube rolling, that could have been a good 20 page running discussion too._

 

I have personally seen about 20 different construction variants of the 6S4A


----------



## studeb

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_The only thing I can think of to say is: thank goodness there are no capacitors in the amps. 
	

	
	
		
		

		
		
	


	


_

 

Could you add some?


----------



## luvdunhill

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_Could you add some? 
	

	
	
		
		

		
		
	


	


_

 

input caps could be arranged


----------



## les_garten

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I don't think the deburring tool can really help on a .1" diameter hole._

 

MOAR Tools!

Micro deburring tool - US Patent 5277528 Description


----------



## BoilermakerFan

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I don't think the deburring tool can really help on a .1" diameter hole._

 

The simple cone shaped fine emery bit in a Dremel works just fine, but I would just knock them out from the top and tap the hole like you did.


----------



## BoilermakerFan

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_I have personally seen about 20 different construction variants of the 6S4A 
	

	
	
		
		

		
		
	


	


_

 

Which is why I bought a matching manufacturer, matching construction octet of them from Al. Which is funny because now I think I'll be selling off the Hybrid and keeping the SS version. The Hybrid is still going into the Sylvania TV camera chassis and heading to CanJam, but I don't plan to keep it after that unless it just smacks the SS into the ground. Reports to date allow me to believe that won't be the case. I'll pull it out of the Sylvania chassis though, and just case it up in a normal NABU.


----------



## wiatrob

Um, how many of you have spent some time with the Sand version of this amp? It turns my Lambda Sigs into OIIs. I have never heard this much/tight bass in them.

 Wonder how the Normals sound.... 
	

	
	
		
		

		
		
	


	




 Al, have you heard this new version? I have a feeling it is going to _KILL_ with the HE-60s... It _will_ clip at insanely, deafening volume levels with Tool's 'Vicarious', but I can get moar out of the volume knobs before that happens. 

 We know this amp will clip eventually, but I couldn't leave the 'phones on my ears it was so loud.

 Still no comparo, and not a lot of time spent with the amp -chores to do here. Truthfully, I was skeptical this version would be an improvement on the follower mod'd version (which I think is a fantastic amp). 

 But it just may be.


----------



## luvdunhill

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Which is why I bought a matching manufacturer, matching construction octet of them from Al. Which is funny because now I think I'll be selling off the Hybrid and keeping the SS version. The Hybrid is still going into the Sylvania TV camera chassis and heading to CanJam, but I don't plan to keep it after that unless it just smacks the SS into the ground. Reports to date allow me to believe that won't be the case. I'll pull it out of the Sylvania chassis though, and just case it up in a normal NABU._

 

Didn't I tell Al to send you the worse sounding construction? yeah, that sounds right 
	

	
	
		
		

		
		
	


	




 The big difference is grey plate versus black plate. The rest is open for interpretation by someone with more free time than myself.


----------



## TimJo

Okay, time for an update. Finally had time this morning to get it wired up, and tested. Dialed right in without a problem. 
	

	
	
		
		

		
		
	


	




 Great design Alex, and my build proves if you get the right parts in the right place with the right orientation, it'll work without issues.

 Now I just need to get the casework finished and wait for my phones to arrive... 

 In the meantime, I'll get it well burned in.

 Here's a not so good picture of it on it's test gig (from my iPhone).


----------



## luvdunhill

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_In the meantime, I'll get it well burned in._

 

don't you need a source and a load to burn it in?


----------



## TimJo

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_don't you need a source and a load to burn it in?_

 

Suppose that's true... well I'll at least get it stabilized as described on the website. I only had time to run it for about twenty minutes, and adjusted the balance and tail of the input stage twice... Alex recommends at least an hour, checking every half hour.


----------



## Beefy

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_don't you need a source and a load to burn it in?_

 

Good point...... any suggestions on a good test load for an amplifier like this?

 I would much rather load/reliability test it with some cheap components than my 'new' Lambdas.


----------



## runeight

A 47pf 1.6kV cap will make a simple dummy load.


----------



## BoilermakerFan

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Um, how many of you have spent some time with the Sand version of this amp? It turns my Lambda Sigs into OIIs. I have never heard this much/tight bass in them.

 Wonder how the Normals sound.... 
	

	
	
		
		

		
			





 Al, have you heard this new version? I have a feeling it is going to KILL with the HE-60s... It will clip at insanely, deafening volume levels with Tool's 'Vicarious', but I can get moar out of the volume knobs before that happens. 

 We know this amp will clip eventually, but I couldn't leave the 'phones on my ears it was so loud.

 Still no comparo, and not a lot of time spent with the amp -chores to do here. Truthfully, I was skeptical this version would be an improvement on the follower mod'd version (which I think is a fantastic amp). 

 But it just may be._

 

That makes me very happy to hear. I might have to go with 500VCT on the SS too and run the 300V zenner string for just that extra last 15V. 

 I will be making custom cups and a custom headband for set of HE60 drivers for a member here. Using JMoney HE90 pads and a Stax cable for them. He's looking forward to getting his drivers made into headphones and I'm excited about hearing them on the eXStata. 

 I'll go with 950s initially, but the SR404LEs are still pulling at me. Has anyone heard the LEs that also has the normal SR404s and O2s?


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_A 47pf 1.6kV cap will make a simple dummy load._

 

These perhaps? Definitely seems worth a quarter to me


----------



## TimJo

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_A 47pf 1.6kV cap will make a simple dummy load._

 

Okay, i'll pick some up for the interim.


----------



## sergery

Can anybody clue me into a source for male stax connectors? Ampwise I have my amp boards stuffed except waiting for sockets. Also a few other odds and ends need to trickle in.


----------



## pabbi1

Bill, I am just digging the snot out of the non-resistor modded hybrid proto, for those times when I'm NOT listening to Tool... but, over time, the clipping has subsided somewhat. That said, my Mouser order is here today for all the stuff I couldn't find at Tanners ( a couple of resistors, the current reg diodes, and the 2n5550)... and, Marc is making some sockets, allegedly - yes?

 So, I'll start the new version tomorrow night, and should have it by Sunday, unless I'm feeling masochistic and look at one of the magnum opii again - though, allegedly, I only have to power one on. Still no other amps to compare to, and my SS version didn't fare well on it's trip to Cali, so, very sad the new owner isn't enjoying it - yet.

 Alex, what do I need to do to use the 269jx, if anything? Run through a resistor to drop the current, or use the lower (91v) zener string? And, any issues (other than polarity) to bottom mounting the caps on the psu? My caps are 330uf, 450v but (always a but) 31mm - kinda ok on one side, but not so much on the other. I am also considering laying them down on the case, and using 1" 18awg leads... still REALLY bad (this is where I usually say "Wahhh, you let ferrari do it... but, then again, he KNOWS what he is doing)? 

 Finally, I have a set of hybrid proto amp boards, and can include _some_ parts (jfets, transistors, resistors, tubes, heatsinks, wire), if anyone is interested, but by no means a complete kit.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_and, Marc is making some sockets, allegedly - yes?_

 

Yes, he's starting them this week or early next, IIRC.

  Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_and my SS version didn't fare well on it's trip to Cali, so, very sad the new owner isn't enjoying it - yet._

 

What happened? I'm planning to keep the SS just so I can ship it all around the country or ROTW with me when I travel...


----------



## HeadphoneAddict

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Um, how many of you have spent some time with the Sand version of this amp? It turns my Lambda Sigs into OIIs. I have never heard this much/tight bass in them.

 Wonder how the Normals sound.... 
	

	
	
		
		

		
		
	


	




 Al, have you heard this new version? I have a feeling it is going to KILL with the HE-60s... It will clip at insanely, deafening volume levels with Tool's 'Vicarious', but I can get moar out of the volume knobs before that happens. 

 We know this amp will clip eventually, but I couldn't leave the 'phones on my ears it was so loud.

 Still no comparo, and not a lot of time spent with the amp -chores to do here. Truthfully, I was skeptical this version would be an improvement on the follower mod'd version (which I think is a fantastic amp). 

 But it just may be._

 

Remember at RMAF when we hooked up the SR-Lambda and the O2 Mk1 to your 1st prototype at the same time, and the Lambdas were elevated to such high levels of sound quality that we were blown away by how close they got, with mouths hanging open?


----------



## studeb

i have he amp hooked up to the PS, and no smoke

 BUT when i put the DMM probe on the output pads, i can measure voltage, but all the decimal places are on. If i check the PS i am getting 285V on each rail at the terminal, i will adjust this back up to 300V each side

 i can haul out a scope if that would help.


----------



## wiatrob

Recheck your PS current (across the test points) after the amp and PS warm up and adjust if necessary.

 When you say you are measuring at the output pads, do you mean across +/- for each channel or from SG to + and SG to - for each channel or both?


----------



## wiatrob

I listened to the Beta and Proto sand amps for a little bit side by side with the Lambda Normals and Sigs tonight (mostly Normals). Both amps are like scalpels when it comes to revealing your source. 

 The Beta and the Normals are an even better pairing than the they were with Proto. The more powerful and controlled bottom end I heard on the bench with the Sigs is still there. Probably more so than the Proto. Too bad I'm too fatigued for any more critical listening tonight.

 Larry, 

 Your daily update: GhostBeta amp is stuffed, cleaned, inspected, touched up, re-cleaned, and ready for me to pick up the damn Zeners I forgot to order to finish the Ps's. Duh. And if the Hybrid is still a faster amp than the Sand, I'm very much looking forward to hearing it too.


----------



## BoilermakerFan

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I listened to the Beta and Proto sand amps for a little bit side by side with the Lambda Normals and Sigs tonight (mostly Normals). Both amps are like scalpels when it comes to revealing your source. 

 The Beta and the Normals are an even better pairing than the they were with Proto. The more powerful and controlled bottom end I heard on the bench with the Sigs is still there. Probably more so than the Proto. Too bad I'm too fatigued for any more critical listening tonight.

 Larry, 

 Your daily update: GhostBeta amp is stuffed, cleaned, inspected, touched up, re-cleaned, and ready for me to pick up the damn Zeners I forgot to order to finish the Ps's. Duh. And if the Hybrid is still a faster amp than the Sand, I'm very much looking forward to hearing it too._

 

Bill, any chance your building one of those SS amps with SJ74s? I'm curious if the faster SJ74s is audible over the S271s. 

 I figured out how to build the Balanced F5 flanking the eXStata SS and keep all amps happy with enough heatsinking, shielding, and air flow. At least in theory without having to use fans. She'll be a wee bit taller than I had hoped, but the F5s will have double the recommended heatsinking per channel and I'm isolating the eXStata SS as much as I can both electrically and thermally. I might even have enough room for a few white rabbits.


----------



## studeb

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Recheck your PS current (across the test points) after the amp and PS warm up and adjust if necessary.

 When you say you are measuring at the output pads, do you mean across +/- for each channel or from SG to + and SG to - for each channel or both?_

 

368mV
 414mV
 rails are up to +/- 302V

 measure across the + and - pads one one amp, set to 0V with P2
 measure from pad to SG set to 0V with P1


----------



## HeadphoneAddict

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I listened to the Beta and Proto sand amps for a little bit side by side with the Lambda Normals and Sigs tonight (mostly Normals). Both amps are like scalpels when it comes to revealing your source. 

 The Beta and the Normals are an even better pairing than the they were with Proto. The more powerful and controlled bottom end I heard on the bench with the Sigs is still there. Probably more so than the Proto. Too bad I'm too fatigued for any more critical listening tonight.

 Larry, 

 Your daily update: GhostBeta amp is stuffed, cleaned, inspected, touched up, re-cleaned, and ready for me to pick up the damn Zeners I forgot to order to finish the Ps's. Duh. And if the Hybrid is still a faster amp than the Sand, I'm very much looking forward to hearing it too._

 

Cool - better is nice!


----------



## runeight

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Alex, what do I need to do to use the 269jx, if anything? Run through a resistor to drop the current, or use the lower (91v) zener string? And, any issues (other than polarity) to bottom mounting the caps on the psu? My caps are 330uf, 450v but (always a but) 31mm - kinda ok on one side, but not so much on the other. I am also considering laying them down on the case, and using 1" 18awg leads... still REALLY bad (this is where I usually say "Wahhh, you let ferrari do it... but, then again, he KNOWS what he is doing)?_

 

Why not just buy the right caps?? They'l fit better and bigger filter caps in this PS really don't help its regulation. 
	

	
	
		
		

		
		
	


	




 You shouldn't need to do anything with the JX if you use 3x100V zeners in the string (leave out 91V zeners). I think we should wait to see what you get.


----------



## runeight

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_368mV
 414mV
 rails are up to +/- 302V

 measure across the + and - pads one one amp, set to 0V with P2
 measure from pad to SG set to 0V with P1_

 

Does this mean that your amps are both working now?


----------



## studeb

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Does this mean that your amps are both working now?_

 

No, the offets are not stable, I was just verifying the set up procedure. The offsets start high 2V if i believe the meter, and slowly drop when i hold the meter on them. The DMM still shows all the decimals when i am measuring . The PS seems to be stable. i used heatsink wiring version B, i will try it with version A as well


----------



## runeight

If you can make a DC measurement then the amps are not oscillating. No need to adjust the heatsink wiring.

 It is normal for the offset to change as the amps warm up. If you set them when the amp is really toasty then they might be a few volts different right at startup. They should drift down to the set voltages when the amp comes to temperature. This is normal.

 If you get offsets, at temperature, that are less than 1V that's the best that this amp will do and it is plenty good enough for headphones that thrive on hundreds of volts across their stators. And, the offsets will wander around due to various thermal fluctuations. This is normal too.


----------



## Beefy

I got a quote back from SumR already...... now that's service! Here's a modified paste:

 *

 ( 2 x 115V primary), ( 2 x 240V secondary) 30VA.
 Note: (off-load for the secondaries is 270Vac.)

 Fully shielded and encapsulated in toroid container (same container as previous purchase).
 All leads exit same side.

 Price: qty =1 Cdn $ 67/e

 *

 So even with postage and GST, it is cheaper for me to buy than a Hammond 3** series, a better form factor, shielded, and no filament wires to secure in the case.

 Now it is still a risk that this will spec up to the right voltage under load, but I think with manipulation of the Zener string around 291±9V it will be an excellent solution for the SS build.


----------



## nattonrice

His communication is second to none.
 Part the reason why I keep buying off him =)


----------



## pabbi1

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Why not just buy the right caps?? They'l fit better and bigger filter caps in this PS really don't help its regulation. 
	

	
	
		
		

		
		
	


	




 You shouldn't need to do anything with the JX if you use 3x100V zeners in the string (leave out 91V zeners). I think we should wait to see what you get._

 

Gracias, and Rodger on the zeners.

 Caps - cause, just once, I'd like to use _some_ of my $1000+ caps "collection"... 
	

	
	
		
		

		
		
	


	




 But, if I gotta, I gotta. Damnit.


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I got a quote back from SumR already...... now that's service! Here's a modified paste:

 *

 ( 2 x 115V primary), ( 2 x 240V secondary) 30VA.
 Note: (off-load for the secondaries is 270Vac.)

 Fully shielded and encapsulated in toroid container (same container as previous purchase).
 All leads exit same side.

 Price: qty =1 Cdn $ 67/e

 *

 So even with postage and GST, it is cheaper for me to buy than a Hammond 3** series, a better form factor, shielded, and no filament wires to secure in the case.

 Now it is still a risk that this will spec up to the right voltage under load, but I think with manipulation of the Zener string around 291±9V it will be an excellent solution for the SS build._

 

Did you just email him or fill out his form? I need a 1000VA dual 18VA secondaries shielded toroid for the F5s... Otherwise I have to go dual 600s from Antek.


----------



## Beefy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Did you just email him or fill out his form? I need a 1000VA dual 18VA secondaries shielded toroid for the F5s... Otherwise I have to go dual 600s from Antek._

 

Email.

 If your request is simple and you are very clear about what you want, email should be fine. The form would be better for more tricky stuff.


----------



## runeight

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Gracias, and Rodger on the zeners.

 Caps - cause, just once, I'd like to use _some_ of my $1000+ caps "collection"... 
	

	
	
		
		

		
		
	


	




 But, if I gotta, I gotta. Damnit._

 

Oh. Well then you should use them.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Gracias, and Rodger on the zeners.

 Caps - cause, just once, I'd like to use _some_ of my $1000+ caps "collection"... 
	

	
	
		
		

		
		
	


	




 But, if I gotta, I gotta. Damnit._

 

Want to sell some of the big caps off? I'll need anywhere from 240K-320KuF for my other amp.


----------



## runeight

Gents, as a result of some background conversation, I'm removing the alternative B heatsink wiring as it does not appear to work in all cases. Whereas diagram A does work.


----------



## wiatrob

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Bill, any chance your building one of those SS amps with SJ74s? I'm curious if the faster SJ74s is audible over the S271s. 
 ._

 

My Proto has 2SJ74s - if I have another matched set in my quiver, I'll consider a swap in.


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Gents, as a result of some background conversation, I'm removing the alternative B heatsink wiring as it does not appear to work in all cases. Whereas diagram A does work._

 


 None of my sinks are wired. Should I pay more attention or try the amps without wiring?


----------



## runeight

Yes, please wire as per the diagram on the website.


----------



## wiatrob

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_No, the offets are not stable, I was just verifying the set up procedure. The offsets start high 2V if i believe the meter, and slowly drop when i hold the meter on them._

 

 Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I

 It is normal for the offset to change as the amps warm up. If you set them when the amp is really toasty then they might be a few volts different right at startup. They should drift down to the set voltages when the amp comes to temperature. This is normal._

 

studeb, It sounds like you have a working amp. After being on for a bit, the offesets should 'stabilize' into a range and wander around there. Have you tweaked the offset/balance pots per the website yet?


----------



## xxbaker

I'm looking snag an extra set of boards if anyone has an extra. Either the SS or the hybrid version (or both) is good with me. PM if you have an extra set of boards you're willing to part with. Thanks


----------



## studeb

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_studeb, It sounds like you have a working amp. After being on for a bit, the offesets should 'stabilize' into a range and wander around there. Have you tweaked the offset/balance pots per the website yet?_

 

Yes i have, i can get them to zero out. But if i come back later they are off again. how much wander is okay?

 the only thing that bothers me is when i put the (non-autoranging) DMM probes on the pads the display on a 20v scale goes from 0.00 to .1.X.X
 i can get the offsets to .0.0.0 but i do not like having those extra decimals there on the display. The manual does not mention what that means.
 should there be AC at the pads?

 i will check the resistor values when i get home tonite


----------



## luvdunhill

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_Yes i have, i can get them to zero out. But if i come back later they are off again. how much wander is okay?_

 

Are the inputs shorted? It could be oscillation.


----------



## runeight

xxbaker, I have two SS board sets left. One of them is on hold for someone pending a PM from him. You can have the other one if you'd like it.


----------



## runeight

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Are the inputs shorted? It could be oscillation._

 

I think that studeb needs to ground the four CCS heatsinks. Then we'll see.


----------



## studeb

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Are the inputs shorted? It could be oscillation._

 

They are not, at least to the best of my knowledge they are not shorted.
 I will tie the heatsinks to ground tonite and report back.


----------



## runeight

I'm pretty sure that this will solve any oscillation problems.


----------



## Emooze

Happy to report my power supply is functioning perfectly. Both rails sitting right around +\-299V, LED's all on, HV bias at 580V. I noticed the instructions state that the DMM will pull the bias reading down? Well I left mine on there for a bit and it stayed right at 580. Should I check this before I hook up any headphones?


----------



## wiatrob

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_Happy to report my power supply is functioning perfectly. Both rails sitting right around +\-299V, LED's all on, HV bias at 580V. I noticed the instructions state that the DMM will pull the bias reading down? Well I left mine on there for a bit and it stayed right at 580. Should I check this before I hook up any headphones?_

 


 Touch it to the bias terminal and not the test pad and see what happens... 

 I think the instructions may need an update.


----------



## wiatrob

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_Yes i have, i can get them to zero out. But if i come back later they are off again. how much wander is okay?_

 

Follow Alex instructions to ground the heatsinks - but I've seen wander around +/- a volt or two. Don't know what the decimal places on your meter are telling you.


----------



## ericj

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_Happy to report my power supply is functioning perfectly. Both rails sitting right around +\-299V, LED's all on, HV bias at 580V. I noticed the instructions state that the DMM will pull the bias reading down? Well I left mine on there for a bit and it stayed right at 580. Should I check this before I hook up any headphones?_

 

You have to read the bias voltage from the provided test point, not from the bias output.


----------



## runeight

emooze, the voltages at the test points will not pull down by very much. But if you look quickly you might see them change a little. If you set for a loaded 580V you may actually run with 5-10V more. Not enough to disturb the headphones.


----------



## Emooze

Hmmmm. I'll check it when I get it all running, before I test with headphones.

 Pending any other work, I should have most of the amp soldering done this weekend. Hopefully I can have everything working next week.


----------



## studeb

a brief update, i have grounded all the heatsinks, and the meter behaves, and there offsets are zeroed in

 now to hook it up


----------



## n_maher

Ok, I've hit my first potential parts snag. The Mouser import tool evidently saw fit to make a few substitutions without informing me 
	

	
	
		
		

		
			





 so I need confirmation if it's ok that Q5,6,7 and 8 are all the 'G' version of the transistors instead of the BOM-spec'd 'STU' version. I looked at the spec and there are differences so I'm guessing I'm screwed and will have to place another order. Not pleased with Mouser.


----------



## BoilermakerFan

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Ok, I've hit my first potential parts snag. The Mouser import tool evidently saw fit to make a few substitutions without informing me 
	

	
	
		
		

		
		
	


	




 so I need confirmation if it's ok that Q5,6,7 and 8 are all the 'G' version of the transistors instead of the BOM-spec'd 'STU' version. I looked at the spec and there are differences so I'm guessing I'm screwed and will have to place another order. Not pleased with Mouser._

 

They should RMA the parts and replace with the correct ones when back in stock at their expense. That happened to me with a MHM parts order. They covered the shipping back and the replacement shipping.


----------



## scompton

863-MJE340G and 863-MJE350G are listed as the alternates in the BOM I have.


----------



## n_maher

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_863-MJE340G and 863-MJE350G are listed as the alternates in the BOM I have._

 

Thanks for checking that, I didn't like seeing that the were different specs but perhaps they are inconsequential specs?


----------



## runeight

Yes, these versions are ok. I don't think there is any consequential change.


----------



## runeight

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_a brief update, i have grounded all the heatsinks, and the meter behaves, and there offsets are zeroed in

 now to hook it up_

 

Good!! Let us know ...


----------



## Lou Erickson

Yay! My J271's came! I think all I still need is the pot, tubes, and a case. I'll have to double-check before I start putting it together. I can build the power supplies without the pots.


----------



## studeb

Holy smokin bass batman.

 Lotsa bass with SRX-Mk3

 almost too much

 i will give a more serious review this weekend, but its waaay to late for me now


----------



## spritzer

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_I noticed the instructions state that the DMM will pull the bias reading down? Well I left mine on there for a bit and it stayed right at 580. Should I check this before I hook up any headphones?_

 

In many cases cheap DMM's will give you an incorrect reading when configuring bias supplies. The meters claim to be CAT II 1000v but they really aren't and thus can't handle the high impedance/voltage.


----------



## Emooze

Ah alright, thanks spritzer. I'll bring it over to the school lab at some point and use their meters.


----------



## runeight

I'm not sure that you really need to except to get a comfort level with the bias supplies. It seems to me that your readings are ok and I wouldn't let this stop you from playing some music.


----------



## pabbi1

So, if I happen to have 1n5369b (51v, 5w - and yes, the leads barely fit), can that sub in for the 1n4757a? And, if I happen to have a 47v, 1w (1n4756a), are we still trying to get closer to 150v total, so 2x 51v and 1x 47v ok, or better at 153v for the z3-5 and z6-8 strings, respectively?

 oK, so Tanners was out of 1n4757a...


----------



## spritzer

If you go much above 600V then you will damage any of the Lambdas, Sigmas, 4070, Gammas and SR-003. Same probably applies to the SR-Omega but I'd never risk drivers which are worth their weight in gold (probably more) with anything but 580V. The HE90 and HE60 will also be damaged soon after 600V since since you are already pushing them at 580V. The SR-007 can take 800V without complaining but it's not something I'd recommend.


----------



## runeight

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_So, if I happen to have 1n5369b (51v, 5w - and yes, the leads barely fit), can that sub in for the 1n4757a? And, if I happen to have a 47v, 1w (1n4756a), are we still trying to get closer to 150v total, so 2x 51v and 1x 47v ok, or better at 153v for the z3-5 and z6-8 strings, respectively?

 oK, so Tanners was out of 1n4757a... _

 

Yes, this will be ok.


----------



## runeight

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_If you go much above 600V then you will damage any of the Lambdas, Sigmas, 4070, Gammas and SR-003. Same probably applies to the SR-Omega but I'd never risk drivers which are worth their weight in gold (probably more) with anything but 580V. The HE90 and HE60 will also be damaged soon after 600V since since you are already pushing them at 580V. The SR-007 can take 800V without complaining but it's not something I'd recommend._

 

Thanks for this info.


----------



## BoilermakerFan

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_If you go much above 600V then you will damage any of the Lambdas, Sigmas, 4070, Gammas and SR-003. Same probably applies to the SR-Omega but I'd never risk drivers which are worth their weight in gold (probably more) with anything but 580V. The HE90 and HE60 will also be damaged soon after 600V since since you are already pushing them at 580V. The SR-007 can take 800V without complaining but it's not something I'd recommend._

 

What are the HE60s rated for? I do NOT want to blow Tachi's drivers via ignorance.


----------



## Beefy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_What are the HE60s rated for? I do NOT want to blow Tachi's drivers via ignorance._

 

Google says 540V.


----------



## pabbi1

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_What are the HE60s rated for? I do NOT want to blow Tachi's drivers via ignorance._

 

I have used them many times in Stax rated stuff @ 580v. There was some issue back when about the he90 (500v rated) running in Stax gear needing a resistor of some sort to prevent some mischief, but he60 I think are fine there. I mostly run mine at 550v and they sound really good in eXStata at that voltage.


----------



## spritzer

540v and a 10M ballast resistor is the spec for the HE60. While most of them run fine on 580V I've seen them do some funky things in the past like oscillating so violently that the phones danced around on a table. That was off a stock Stax SRM-1 Mk2. While we normally say that only the correct bias voltage is needed to use the various phones on any amp there is quite a bit more to it then that. A Koss ESP950 will misbehave on a Stax amp that has less bias then stock but is fine from the Koss amp for example. 

 One other thing, there has been some confusion in the past about what the normal bias really is. I've seen 280V quoted more then once but it is 230V for the SR-Lambda/SR-Sigma but 200V for all the SR-X Mk3 and older. If you manage to find a SR-1 then there were both 150V and 200V versions with the 150V being the older one. Running a 200V set on 230V has never caused any issues for me and the specs for NB confirm that this is well withing the operational parameters of the drivers. Any higher then that and you are asking for trouble.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_540v and a 10M ballast resistor is the spec for the HE60. While most of them run fine on 580V I've seen them do some funky things in the past like oscillating so violently that the phones danced around on a table. That was off a stock Stax SRM-1 Mk2. While we normally say that only the correct bias voltage is needed to use the various phones on any amp there is quite a bit more to it then that. A Koss ESP950 will misbehave on a Stax amp that has less bias then stock but is fine from the Koss amp for example. 

 One other thing, there has been some confusion in the past about what the normal bias really is. I've seen 280V quoted more then once but it is 230V for the SR-Lambda/SR-Sigma but 200V for all the SR-X Mk3 and older. If you manage to find a SR-1 then there were both 150V and 200V versions with the 150V being the older one. Running a 200V set on 230V has never caused any issues for me and the specs for NB confirm that this is well withing the operational parameters of the drivers. Any higher then that and you are asking for trouble._

 

I'm having Woo make me an "HE90 to Stax" adapter so I can try out the lower 540v bias jack on the WES and see how it sounds. I was thinking it wont make a big difference.


----------



## runeight

Gents, I think the last sand board set is now taken. No more boards left. Perhaps your builds and impressions will get others interested and we can make another run. If not, well, you guys are going to have a really nice inexpensive stat amp.


----------



## digger945

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_ Perhaps your builds and impressions will get others interested and we can make another run. If not, well, you guys are going to have a really nice inexpensive stat amp. 
	

	
	
		
		

		
		
	


	


_

 








 Ahem. Interested.


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Gents, I think the last sand board set is now taken. No more boards left. Perhaps your builds and impressions will get others interested and we can make another run. If not, well, you guys are going to have a really nice inexpensive stat amp. 
	

	
	
		
		

		
		
	


	


_

 






 I'm now all BOM'ed up without issue, being able to get everything except C6 which I don't need immediately as my Stax are normal bias...... but before I whip out the credit card are there any additional tweaks or changes you were considering before the 'final' version?

 The only thing I can think of that hasn't been discussed yet is whether there are any Schottky diodes that would be worthwhile replacements for the standard 1n4007? Though I suspect that there aren't many devices that will handle the voltage.


----------



## runeight

No, no changes that I can think of. The amp and ps are pretty well vetted by now and we know that they come up and sound pretty good.

 Since the amps seem to be very quiet I don't think there is any need to adjust the rectifiers. They are already ultra fast if you get the uf4007s.


----------



## runeight

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_







 Ahem. Interested.
	

	
	
		
		

		
		
	


	


_

 

OK. Thanks!!!


----------



## luvdunhill

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_are any Schottky diodes that would be worthwhile replacements for the standard 1n4007? Though I suspect that there aren't many devices that will handle the voltage._

 

Digi-Key - C2D05120A-ND (Manufacturer - C2D05120A)


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_No, no changes that I can think of. The amp and ps are pretty well vetted by now and we know that they come up and sound pretty good.

 Since the amps seem to be very quiet I don't think there is any need to adjust the rectifiers. They are already ultra fast if you get the uf4007s._

 

Thought as much. Cheers 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Digi-Key - C2D05120A-ND (Manufacturer - C2D05120A)_

 

_Clearly_ worth the money......


----------



## Emooze

Pffft garbage, you need some of these:

R1600B16C Ruttonsha Diodes (RF, Signal, Switching, Power)


----------



## pabbi1

Marc, always a budget buster, as that is x7... 
	

	
	
		
		

		
		
	


	




 Alex, better at 153v or 149v on the zener string, or ambivalent?


----------



## Beefy

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_Pffft garbage, you need some of these:

R1600B16C Ruttonsha Diodes (RF, Signal, Switching, Power)_

 

Max Surge Current: 16600 A


----------



## runeight

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Marc, always a budget buster, as that is x7... 
	

	
	
		
		

		
		
	


	




 Alex, better at 153v or 149v on the zener string, or ambivalent?_

 

Doesn't matter and will not cause problems either way.


----------



## sergery

Percy carries some fairchild fred diodes rated at 1200V 8A for 1.95$ each. They are TO-220, and would require some tweaking to get to fit though. I don't know how they compare to stock or the Schottkys, but at least they aren't $10 each


----------



## Beefy

Oh god, I hope I haven't sparked a whole round of discussion about new and unnecessary non-tweaks


----------



## BoilermakerFan

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Digi-Key - C2D05120A-ND (Manufacturer - C2D05120A)_


----------



## pabbi1

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Oh god, I hope I haven't sparked a whole round of discussion about new and unnecessary non-tweaks 
	

	
	
		
		

		
		
	


	


_

 

Someone had to do it...


----------



## luvdunhill

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_






_

 

pretty much the only high voltage Schottky I know about. SiC is the new rage anyways, right? (i.e. the new fancy SemiSouth SiC JFETs that Nelson Pass is using)


----------



## n_maher

Another power supply up and running and appearing to work just fine. Power trafo is the 369JX. And I think this picture illustrates perfectly the reason for owning more than one DMM.


----------



## sachu

Just finished populating 2 PSU boards...will finish up the amp boards and then test the supplies..also have a 369JX here so more test points with the 300 series transformer forthcoming in due time


----------



## BoilermakerFan

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_pretty much the only high voltage Schottky I know about. SiC is the new rage anyways, right? (i.e. the new fancy SemiSouth SiC JFETs that Nelson Pass is using)_

 


 Well, if it's good enough for Papa Pass... So very, very tempting.


----------



## runeight

Yes, those SiC jfets are pretty interesting. They are big jobbies though, but they might be really handy in a very high voltage stat amp. You could get at least 2000Vpp out of them if the rest of the amp's components could stand it. But, such an amp would probably kill someone sometime. I know because a 1kV supply almost killed me many moons ago.

 But, back to builds ...

 Nate, your filter cap voltage looks like nearly 360V. Is that right? If so, keep an eye on the fets in the PS. It may be that the all 100V zener string is the best way to go.


----------



## webbie64

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_No, no changes that I can think of. The amp and ps are pretty well vetted by now and we know that they come up and sound pretty good.

 Since the amps seem to be very quiet I don't think there is any need to adjust the rectifiers. They are already ultra fast if you get the uf4007s._

 

Sounds great.

 Alright I have a request that may sound lazy but it is simply because I am extremely short on time ATM - family issues (elderly mother and mother-in-law have both had (different) operations in the last fortnight; both out of their respective hospitals for Xmas we hope) plus dramatic work change last week (I work in the state political area and we've changed our leader last week, meaning everything will now be changed - ministers, responsibilities, priorities, etc - and the coming fortnight will be FULL ON).

 I wanted to complete my Beta Build during my Christmas break but will not have time to get the parts together (I have the boards for the tube amp).

 I am looking for someone to assist me by offering to get the full kit of required parts ordered and out to me in Sydney Australia.

 I know it's a big ask but I'm from one of those families that reinforced that if you don't at least ask, you'll never know what's possible (or not) 
	

	
	
		
		

		
		
	


	




 Please don't clog the thread with any responses. If you are willing and able to help then please PM or email me direct.

 Thanks.

 Ian


----------



## Keithpgdrb

I really hope this proto team wasnt the only build. I am completely NOT ready to attempt this high voltage project, but I do not want to miss out on this. its perfect for what i want. SO, even If I dont get the parts right away, please sign me up for a board on the next run. I'll have to wait for more feedback on the two designs to decided which to build. I remember in an earlier post that you said the two amps sound nearly identical because of the way the tube is integrated. Looking for some more feedback as people start testing. I'll be running NB sr-lambdas.


----------



## sumo-kun

Whew! Just finished a marathon run reading this whole thread.

 I'd first like to say, congrats and thanks for the GREAT work guys!
	

	
	
		
		

		
		
	


	




 I'd definitely be interested in the next run of amps. I have a SR303 + SRM313 system and its great but this thread has me intrigued. I was looking at getting an Airbow modded 404 sometime and it would be interesting to see how that sounds 
	

	
	
		
		

		
		
	


	




 When is a next run expected? I'm in Japan so I'll probably have to some homework to see what parts I can get. It will probably be a tube version... maybe. Are there no listening results from the builds yet?


----------



## n_maher

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Nate, your filter cap voltage looks like nearly 360V. Is that right? If so, keep an eye on the fets in the PS. It may be that the all 100V zener string is the best way to go._

 

Left to Right those meters are reading:

 408mVDC from test point 3 to 4.
 359mVDC from test point 1 to 2.
 298VDC on the positive rail (across the 10k resistor).

 I haven't checked the voltage at the caps yet, it was getting late last night. So today I'll do that and also check the bias side of things.


----------



## minivan

psu report

 this is for aussie builder's reference or for someone from country with line voltage 240v.

 my line voltage at home is high, around 251-5 v, alex suggested to used the 300v zener strings instead of the 291v zener strings.

 transfomer is 369jx for 240v line voltage

 my readings are:
 line voltage: 251v
 secondary: 274 v
 t1-t2:359mv
 t3-t4:-414mv
 t3:-352v
 t1:355v
 rail:-314, 314
 all heatsinks can be touch for long period with no problem.

 for some reason, when i first start up the psu, t3-t4 and t1-t2 voltages will drop causing both led to turn off, the voltage of t1-t2, t3-t4 will eventually stablized in about 5 mins. alex suggest me to power up the psu and wait 20 minutes then readjust p1 and p2 to raise t1-t2 ,t3-t4 to 360mv and 410mv, and it's been all good since. 


 also for aussie builder's info, if you ordered $200 aud worth of goods from mouser , they will give you free shipping.i reckon if you source all the parts including the transfomer you should come very close to $200 aud.

 i am currently four 100v 1w zener d041(mouser part: 78-1N4764A-TAP) short for the 300v zener string of my other psu build. i will be grateful if someone have some spares one of those to sell me or order 4 extra of those if they are ordering parts from mouser and resell them to me.


----------



## Beefy

Quote:


  Originally Posted by *webbie64* /img/forum/go_quote.gif 
_I am looking for someone to assist me by offering to get the full kit of required parts ordered and out to me in Sydney Australia._

 

Not what you were looking for I'm sure, but I am more than happy to share my Mouser project with you for the PS and SS. You will still need to add a fair few accessories for casing, etc (which you would still probably have to do with a kit anyone else offers) and a power transformer, but most of the work is done.

Exstata PS
Exstata SS

 I make no guarantees for accuracy (if we're _both_ lucky, someone might be bored enough to confirm it), or that everything will stay in stock...... but this is exactly what I will be ordering tomorrow, plus a couple of spares of most of the transistors.

  Quote:


  Originally Posted by *minivan* /img/forum/go_quote.gif 
_i am currently four 100v 1w zener d041(mouser part: 78-1N4764A-TAP) short for the 300v zener string of my other psu build. i will be grateful if someone have some spares one of those to sell me or order 4 extra of those if they are ordering parts from mouser and resell them to me._

 

I can order you the zeners as requested...... I just still think it is silly for me to order them from the US, get them in Canada, and then send them to Australia.

 There has to be a more efficient way......


----------



## minivan

hi beefy, thanks for the offer to help. i am not planning to buy another $200 aud parts from mouser, it mean i have to pay high shipping fee ($39aud shipping charge) just for 4x 100v zener that cost 26cents. now if someone can send those zener to me in a letter, that mean my postage cost will be just the cost of the stamp and the envelop.


----------



## fierce_freak

Can anyone confirm 512-KSC5027OTU as a replacement for the KSC5042?


----------



## runeight

Yes, it is ok. Are you ordering from Mouser? They have about 1000 KSC5042s still in stock.


----------



## fierce_freak

:facepalm: I don't know why I thought it was out of stock. It must have been the talk about KSC5027 being a good sub for hybrid builds.


----------



## runeight

Ah. The 5027 is still a good sub for the follower devices in the hybrid. And, eventually, the 5042s will be out of stock. Then everyone will have to use the 5027s or those much better Sanyo jobbies that pabbi1 posted a few pages back.


----------



## n_maher

Checked my caps this afternoon, they are both right around 336VDC which seems about right to me.


----------



## runeight

Yes, that's right in the target range.

 Those of you who have working amps, have you been listening to them? How are they holding up over time?


----------



## runeight

And while we're waiting, Marc if you're still listening in, what about J112/J177 (or maybe J176) as a decent complementary pair? Seems like the could be Idss matched which would get their gms close to the same.


----------



## studeb

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes, that's right in the target range.

 Those of you who have working amps, have you been listening to them? How are they holding up over time?_

 

Well mine has been on since Friday night non stop, except for a few hours today. PSU is stable, i have to check the offsets again, but i think they will be stable. All the heatsinks are warm, except for Q5/6 on the PSU which is about 5 sec hot.

 Soundwise, this is great. Nice tight bass. You know something is up when you say, "hey where did that bass line come from...." When i first powered it up it seemed to be bass heavy, but that has changed over the last few days. Top end is smooth, not too bright, i have been a tube kinda guy fo a long time, but i do not mind this sand amp one bit.

 Thanks Alex, all in all a super smooth amp.

 I do not have another stat amp to compare it to, but if anyone in San Diego has one ands is interested in a listen, let me know.


----------



## pabbi1

Ok, let's talk about PSU wiring - in the original proto, I had to add some resistors on the input - is that no longer the case, even with the 269jx?


----------



## BoilermakerFan

Another PSU question... Is the Nichicon a superior cap to the Panasonic and worth the extra $10 a pair in the PSU? I've always preferred Panasonic caps, hence my question. The price deltas between Mouser and Digi-Key prevent me from assuming more expensive means better.


----------



## wiatrob

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Another PSU question... Is the Nichicon a superior cap to the Panasonic and worth the extra $10 a pair in the PSU? I've always preferred Panasonic caps, hence my question. The price deltas between Mouser and Digi-Key prevent me from assuming more expensive means better._

 

I wouldn't spend extra for PSU caps, there's not much to be gained from what's been spec'd.

 I had Obligato films on my PS output early in the proto phase when I spaced a cap order. Coudn't hear a difference


----------



## runeight

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Ok, let's talk about PSU wiring - in the original proto, I had to add some resistors on the input - is that no longer the case, even with the 269jx?_

 

I think you should try it without any resistors. I suspect it will be ok.


----------



## awpagan

Quote:


  Originally Posted by *minivan* /img/forum/go_quote.gif 
_psu report


 i am currently four 100v 1w zener d041(mouser part: 78-1N4764A-TAP) short for the 300v zener string of my other psu build. i will be grateful if someone have some spares one of those to sell me or order 4 extra of those if they are ordering parts from mouser and resell them to me._

 

But I did get 12 100v 1w zener d041(mouser part: 78-1N4764A-TAP).
 enough for 2 psu's + spare.
 You're welcome to 4 of them.

 I'm in Sydney too. pm me


 I ordered the 269jx transfomer instead of the 369jx "Doh"


----------



## BoilermakerFan

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I wouldn't spend extra for PSU caps, there's not much to be gained from what's been spec'd.

 I had Obligato films on my PS output early in the proto phase when I spaced a cap order. Coudn't hear a difference 
	

	
	
		
		

		
		
	


	


_

 

Thanks Bill, I just wanted to make sure there wasn't a potentially audible difference in ripple or PSRR.


----------



## Beefy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Thanks Bill, I just wanted to make sure there wasn't a potentially audible difference in ripple or PSRR._

 

The caps feed a CCS, and the CCS feeds a shunt. They would have to be _seriously_ bad caps to make a difference in all of this.


----------



## pabbi1

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Those of you who have working amps, have you been listening to them? How are they holding up over time?_

 

Ok, the SS is going SE (now residing in Cali), and no idea what is causing a hum in one system (no idea on the chain), but not in two others. Maybe Sergery can update? it is the 2nd generation proto with Triads.

 2nd generation Hybrid is a daily player, and, well, it continues to be a fun. It really does nail guitars (my focal obsession) and all manner of microdetail - with prodigious bass. I did notice a 'smoothing' of the amp at about the two week level (~60-70 hours), but who knows if it is the tubes, sand, or just everything playing well together.

 3rd generation Hybrid missing 3 resistors that I'll pick up at lunch, though I'm waiting on a few chasis parts to fire it all up. Will power psu tonight or tomorrow to see if everything holds (yes. my load resistors are on the desk) - might even post a pic just to have Runeight's personal physician prescribe some digitalis... then I can compare the 2nd and 3rd generation Hybrids except for a couple of other differences (tubes, tranny, jacks, attenuators, etc) - never ceteris paribus, eh?


----------



## marcus1

Hi

 I've been an avid follower of this thread and hopefully will be building a hybrid soon but I'm a bit confused when you write about the 2nd and 3rd generation hybrids. What are the differences between the two - are you using different components or design?


  Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Ok, the SS is going SE (now residing in Cali), and no idea what is causing a hum in one system (no idea on the chain), but not in two others. Maybe Sergery can update? it is the 2nd generation proto with Triads.

 2nd generation Hybrid is a daily player, and, well, it continues to be a fun. It really does nail guitars (my focal obsession) and all manner of microdetail - with prodigious bass. I did notice a 'smoothing' of the amp at about the two week level (~60-70 hours), but who knows if it is the tubes, sand, or just everything playing well together.

 3rd generation Hybrid missing 3 resistors that I'll pick up at lunch, though I'm waiting on a few chasis parts to fire it all up. Will power psu tonight or tomorrow to see if everything holds (yes. my load resistors are on the desk) - might even post a pic just to have Runeight's personal physician prescribe some digitalis... then I can compare the 2nd and 3rd generation Hybrids except for a couple of other differences (tubes, tranny, jacks, attenuators, etc) - never ceteris paribus, eh?_


----------



## runeight

Version 1 was the original proto. Version 2 was the original proto with resistor changes to the emitter followers.

 Version 3 is what we have now and if there are future boards, this is what they will be.


----------



## Emooze

Version 1 = red boards
 Version 2 = green boards
 Version 3 = black boards right?

 Also, my amp is all soldered together, I have enough time tonight after work I'll be giving it a test run, otherwise it'll be tomorrow after I clean the boards and heatshrink all the exposed connectors.


----------



## runeight

LOL. Close enough.


----------



## pabbi1

Also note, for those playing along, we had a 0 Generation version that laid the groundwork for where we are now.

 So, technically accurate is:

 Gen 0 - Green boards
 Gen 1 - Red boards
 Gen 2 - _same_ Red boards, with a resistor mod, and ccs protoboard
 Gen 3 - Black boards

 If anyone is interested in a "Collectors Edition" of Red hybrid boards, let me know. Also, if anyone wants to try the 2sc3675 in place of the 5042, I have enough for 3 sets.


----------



## Beefy

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Also, if anyone wants to try the 2sc3675 in place of the 5042, I have enough for 3 sets._

 

Looking at the data sheets, I can't see any major differences in the specs between those two. Am I missing something?


----------



## studeb

another silly question, what size are the mounting holes on the PCB?

 My standoffs do not fit.


----------



## sachu

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_another silly question, what size are the mounting holes on the PCB?

 My standoffs do not fit.
	

	
	
		
		

		
		
	


	


_

 

All of Alex's boards are designed for 4-40 hardware


----------



## runeight

They should clear a 4-40 screw.


----------



## runeight

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Looking at the data sheets, I can't see any major differences in the specs between those two. Am I missing something?_

 

No you're not. They are nearly identical which makes the Sanyo a very good sub.


----------



## Beefy

Ah, I got the impression earlier that the Sanyo would actually be better, but was confused when they were so similar


----------



## runeight

Right. What I meant to say earlier is that the sanyo is a better sub than the ksc5027. Although the 5027 is not a bad sub at all if needed.


----------



## sachu

both versions of the boards are all populated...will get around to testing them this week..ordered a few more 100V zeners in case i might want to change the zener string.


----------



## wiatrob

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Also note, for those playing along, we had a 0 Generation version that laid the groundwork for where we are now.

 So, technically accurate is:

 Gen 0 - Green boards
 Gen 1 - Red boards
 Gen 2 - _same_ Red boards, with a resistor mod, and ccs protoboard
 Gen 3 - Black boards

 If anyone is interested in a "Collectors Edition" of Red hybrid boards, let me know. Also, if anyone wants to try the 2sc3675 in place of the 5042, I have enough for 3 sets._

 

Technically, there were both Green and Red Gen 1 boards, but who's counting


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Also, if anyone wants to try the 2sc3675 in place of the 5042, I have enough for 3 sets._

 

I'm interested Al... Why not, I haven't really followed the BOM for the SS so far... 
	

	
	
		
		

		
			





 Might as well build my SS with all subs or alts.


----------



## Beefy

Right, so the very last thing I need for my build is some high voltage hook-up wire. It would be absolutely nuts for me to buy 100ft of a couple of different colours from Mouser or Digikey so I don't want to do that. ApexJr as mentioned earlier in the thread would be an option, if it weren't for the fact they only accept wire transfer for international orders - and a hefty fee for the privilege. The best eBay option I found would not ship outside the US.

 Can anybody suggest any other alternatives?


----------



## Emooze

I got my wire off of eBay, 100ft for like $15 or so.


----------



## Beefy

Well this stuff and others from the same vendor would be perfect, but no international shipping


----------



## digger945

Pick out what you want, and I will ship it to you.
 I need to get some to do some HV wiring myself so it would really be no trouble at all.


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Well this stuff and others from the same vendor would be perfect, but no international shipping 
	

	
	
		
		

		
		
	


	


_

 

How fast are yo looking to build? I need 600V or 1KV hook up wire and I haven't ordered mine yet. I'll be happy to CYA and ship it to you in a Tyvek envelope. I'll get around to ordering it this week or early next. Have to get the Mouser and Digi-Key orders in first. Have a local customer wanting his old HAM radio recapped by Christmas so that has to be done...


----------



## luvdunhill

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Right, so the very last thing I need for my build is some high voltage hook-up wire. It would be absolutely nuts for me to buy 100ft of a couple of different colours from Mouser or Digikey so I don't want to do that. ApexJr as mentioned earlier in the thread would be an option, if it weren't for the fact they only accept wire transfer for international orders - and a hefty fee for the privilege. The best eBay option I found would not ship outside the US.

 Can anybody suggest any other alternatives?_

 

well, seeing as I already have a package that's collecting contents for Beefy, I can help out, let me know what you'd like.

 Here's my suggestion:

Belden Hookup Wire Teflon, Silver Coated 22 AWG, 83006 - eBay (item 220381966211 end time Oct-27-09 09:36:27 PDT)


----------



## Beefy

Awww shucks, spoiled for choice 
	

	
	
		
		

		
		
	


	




 I'll have a closer look tomorrow when I don't have quite so much of a headache.


----------



## pabbi1

In grounding the heatsinks on the Hybrid, is it the same - i.e. grounding the two sinks on (only) the input side?


----------



## runeight

Correct, both input side heatsinks on both amp boards for a total of four heatsinks. See the wiring diagram on the website.


----------



## pabbi1

Just making sure since it is the SS version on the website...


----------



## runeight

Right. I'll have to fix that.


----------



## Beefy

I just realised this morning that I put my Mouser order for all the parts for this on the wrong credit card. Thankfully the order went through, but I really should pay more attention 
	

	
	
		
		

		
		
	


	




 Late night idiocy aside, back to hook up wire...... is 22AWG going to be sufficient for the power wiring? I would normally use 17-20AWG for power, just because that is what I would have handy.


----------



## runeight

22awg is more than enough for the currents involved except for the heaters. Depending on how your wire them you might want to use 20awg.


----------



## Beefy

Thanks


----------



## luvdunhill

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Thanks 
	

	
	
		
		

		
			



_

 

Not sure why you mentioned 22 awg, but if it was based on the Ebay auction above, they also sell 18 awg in the same stuff.


----------



## Beefy

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Not sure why you mentioned 22 awg, but if it was based on the Ebay auction above, they also sell 18 awg in the same stuff._

 

Yeah, I'm looking at and deciding between 18 and 22 from the store you linked. I'm not sure I want 18 all round because it seems a bit nuts to run something so bulky for the bias and audio outs.

 But I wasn't sure 22 would be sufficient gauge for the power wiring either, if only because I have used bigger stuff for previous projects - mainly based on AMB's recommendations for the M3 and B22. I appreciate that they run much higher current than this amp will, but this being my first HV project, I want to make sure I'm not likely to burn the house down


----------



## n_maher

Why pick one when you can just buy both? 
	

	
	
		
		

		
		
	


	




 The 18ga stuff makes for nice DIY PC's too.


----------



## spritzer

22AWG is fine for all the DC power lines but I usually wire live AC with 18AWG out of habit.


----------



## Beefy

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Why pick one when you can just buy both? 
	

	
	
		
		

		
		
	


	




 The 18ga stuff makes for nice DIY PC's too._

 

Because after a huge Mouser order, paying for Stax jacks, casework tools, etc. etc. I am effectively too broke to buy several different kinds of wire 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_22AWG is fine for all the DC power lines but I usually wire live AC with 18AWG out of habit._

 

No complaints here. I already have some bog-standard hook up wire for that.


----------



## pabbi1

Always use 18awg for heaters myself, preferrably 200c PTFE - and boy, look at the geeks pop out when someone starts talking about wire... who'd a thunk it?


----------



## n_maher

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Always use 18awg for heaters myself, preferrably 200c PTFE - and boy, look at the geeks pop out when someone starts talking about wire... who'd a thunk it?_

 

Did you just call me a geek?


----------



## studeb

i ran:

 18g canabilised stranded for the AC
 18g teflon stranded spc for the DC power
 22g solid spc for the outputs
 canabilised canare for the inputs

 i'll have to post some more pics i guess

 had three hours of blackout yesterday, amp was done, but can't listen to it...


----------



## pabbi1

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Did you just call me a geek? 
	

	
	
		
		

		
		
	


	


_

 

Great avatar - now would I do something stupid like that (uber rhetorical)? 
 Even better asking marc an offline question while doing so...

 To a bit different topic, what are folks doing about casing? I am currently on top dead center fail on this one - another wood case <sigh>?


----------



## wiatrob

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_
 To a bit different topic, what are folks doing about casing? I am currently on top dead center fail on this one - another wood case <sigh>?_

 

Pedestrian ParMetal...


----------



## Beefy

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_To a bit different topic, what are folks doing about casing?_

 

I bought two HiFi2000 Pesante 2U cases in a group buy on another forum. The Exstata is going in one of those, to make a matching stack with my Buffalo DAC going in the other.

  Quote:


 I am currently on top dead center fail on this one - another wood case <sigh>? 
 

Why would you sigh at that idea? Your wood cases are beautiful!


----------



## studeb

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_To a bit different topic, what are folks doing about casing? I am currently on top dead center fail on this one - another wood case <sigh>?_

 

i was going to try a wood one, i do not have anything metal to salvage it into. i think Xmas cookie tins are not quite right for this, and given that my youngest likes to touch this project, a case is required

 any reason this could not be a two box build?


----------



## pabbi1

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Why would you sigh at that idea? Your wood cases are beautiful! 
	

	
	
		
		

		
		
	


	


_

 

Gracias, but Dr Wood isn't doing the dovetails for me on this one (and I just plain suck at dovetail or box joints), and think this amp deserves better than what I've been doing. Besides, wait until you see the metal cases I have (mostly) fabbed - just need to find a GOOD aluminum welder in DFW.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_To a bit different topic, what are folks doing about casing? I am currently on top dead center fail on this one - another wood case <sigh>?_

 

eBAy is your friend... In addition to the Sylvania TV camera, now gutted for a tube amp, I also picked this up:

Hallicrafters S-95 Civic Patrol SW Receiver 40 Watts - eBay (item 120491506095 end time Nov-17-09 14:45:15 PST)

 My plans have since changed, as I originally planned to keep the Hybrid in the Sylvania and sell the SS. Now I've flopped and will probably sell the populated Hybrid boards after testing, unless it's just a far more entertaining amp than the SS...

 They'll both fit in your old standby... NABU. You could go crazy and cut out a port hole window into the NABU through the front faceplate so you can see the tubes glowing...

 My standard faceplate is walnut or maple. Stealthed LEDs, counter sunk volume knob, countersunk jacks, etc... 

 I'm trying to stuff the two F5s, with PSU at the far sides on each end with the eXStata SS in the middle within the confines of a NABU base. To alleviate confusion, only one amp will be powered at a time. So either the F5s or the eXstata, but not both. One master power switch, crossed within the eXStata switch so if the eXStata is flipped on, the F5s go off. Might have to put an E12 time delay in there too, to make it 4yo destructive son proof.


----------



## n_maher

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_To a bit different topic, what are folks doing about casing?_

 

Probably going either with Lansing or Context for mine.


----------



## sumo-kun

Is there any news on if there is going to be a new run of boards available? 
	

	
	
		
		

		
			




 I'd be up for one and there seems to be a few guys earlier in the thread showing interest. How many boards/requests would be needed to make a next run feasible?


----------



## M3NTAL

Is there anyone interested in doing a commissioned build of one of these when the boards become available?


----------



## BoilermakerFan

Quote:


  Originally Posted by *M3NTAL* /img/forum/go_quote.gif 
_Is there anyone interested in doing a commissioned build of one of these when the boards become available?_

 

PM Sent.


----------



## wiatrob

Three power supplies up. Load tested with Larry's Hybrid amp board - it's up with stable offsets hovering around 0V. 

 Maybe get it to make some sounds tomorrow eve...


----------



## Uncle Erik

I haven't been around here as much as I'd like lately, but wanted to say thanks for the gorgeous boards and chips! Hopefully, I can find the time to order the parts this weekend and I've got a spare Par-Metal case to put it in. With a little luck, I can stuff the boards between Christmas and New Year's and get it up and running.

 I'm really looking forward to it. n3rdling's solid state version sounded incredible at the Orange County meet, so I'm looking forward to jacking my O2 into my own.

 Thanks again!


----------



## HeadphoneAddict

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Three power supplies up. Load tested with Larry's Hybrid amp board - it's up with stable offsets hovering around 0V. 

 Maybe get it to make some sounds tomorrow eve... 
	

	
	
		
		

		
		
	


	


_

 

Sounds exciting!

 BTW, we'll get to compare the eXStatA to the Woo WES now...


----------



## Lil' Knight

Quote:


  Originally Posted by *M3NTAL* /img/forum/go_quote.gif 
_Is there anyone interested in doing a commissioned build of one of these when the boards become available?_

 

Same here. 
	

	
	
		
		

		
		
	


	




 Did any compare the SE and balanced inputs? Is there any difference in sound?


----------



## n_maher

Unless the source has a different output stage for its SE vs. balanced output I would think that if you were using short IC's it'd be impossible to distinguish between the two.


----------



## FrankCooter

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Unless the source has a different output stage for its SE vs. balanced output I would think that if you were using short IC's it'd be impossible to distinguish between the two._

 

Be careful Nate! You'll get the peasants with the pitchforks after you!


----------



## n_maher

Quote:


  Originally Posted by *FrankCooter* /img/forum/go_quote.gif 
_Be careful Nate! You'll get the peasants with the pitchforks after you!_

 

I ain't skeeeered, I'll just start throwing transformers and chokes at them!


----------



## wiatrob

Balanced vs. Un - that's another thread isn't it? That said - we did notice a difference with the proto at RMAF. even though there's not supposed to be a gain difference between the two inputs, we heard lower gain on the SE.

 Larry, did we ever listen to the dif's after we solved the source problem? I think it was only running balanced from my Opus the rest of the show.

 Sherwood has listened extensively SE, perhaps he could be cajoled into sharing his experience.

 I can A/B with my DAC Magic, but can't be sure of it's output stage topology differences between SE and Balanced.


----------



## spritzer

The isn't any difference in gain between the inputs (or rather grounding one half of the input to be more precise) but balanced has twice as much voltage as SE (2V vs. 4VRMS) so the end voltage swing is doubled.


----------



## n_maher

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_The isn't any difference in gain between the inputs (or rather grounding one half of the input to be more precise) but balanced has twice as much voltage as SE (2V vs. 4VRMS) so the end voltage swing is doubled._

 

Slight clarification, feeding the amp with a balanced input provides the *potential* for more output voltage swing. But as previously explained by jcx this amp has sufficient gain such that even a 2V input signal will allow for maximum output voltage swing as limited by the power supply. I think I have that right.


----------



## spritzer

Indeed that is correct. 
	

	
	
		
		

		
		
	


	




 Feed it 4V and it should then output 2kV but that won't happen.


----------



## Beefy

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_Indeed that is correct. 
	

	
	
		
		

		
		
	


	




 Feed it 4V and it should then output 2kV but that won't happen._

 

At a gain of 1000 it would try and output 4kV, wouldn't it?


----------



## spritzer

The gain is 500 I believe or I'm just too fried from reading way too many tube data sheets today.


----------



## Beefy

No, I'm quite sure it is ~1000 
	

	
	
		
		

		
			





  Quote:


 A small amount of NFB is applied to the sources of the diff pair. However, the NFB is small enough that it does not entirely control the gain of the amp, which is still primarily in hands of the jfets. The values chosen are an average value to bring the average gain down to about 1000. Jfets with high transconductance will cause the amp to have higher gain and vice versa. 
 

From The eXStatA Electrostatic Amplifier


----------



## spritzer

Ahh ok. I blame it on obscure TV tubes messing with my brain...


----------



## BoilermakerFan

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_Ahh ok. I blame it on obscure TV tubes messing with my brain... 
	

	
	
		
		

		
		
	


	


_

 


 Oooo. I have a box of those and HAM radio tubes in my basement. Send me a PM if you come across some with great potential.


----------



## runeight

Well, it depends on how you measure gain, but ...

 If you put 600mV peak to peak across the balanced inputs you will get, approximately, 600V peak to peak at the output. Approximately because it depends on the transconductance of the jfets as you all know. 
	

	
	
		
		

		
		
	


	




 But, with sources that routinely generate 2V or more any one of them can drive this amp to clipping.


----------



## spritzer

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Oooo. I have a box of those and HAM radio tubes in my basement. Send me a PM if you come across some with great potential. 
	

	
	
		
		

		
		
	


	


_

 

There are some strong candidates but nothing solid until I've built and tested a prototype.


----------



## sumo-kun

Regarding balanced vs SE, how about if I want say 600V at the output. For SE, that means the volume pot will need to be turned to say position X. But for balanced, the pot will be turned to half of X, or basically the amp will need to amplify half as much? So keeping that in mind, won't distortions etc from the higher gain needed in SE affect sound? Whether you'll be able to hear the difference or not is another matter, I know 
	

	
	
		
		

		
		
	


	



 Just thought I'd throw that on the fire


----------



## runeight

Yes. I explained this in post a few pages back. 
	

	
	
		
		

		
		
	


	




 The distortion goes up slightly if you drive the same output with SE.


----------



## jgazal

Quote:


  Originally Posted by *sumo-kun* /img/forum/go_quote.gif 
_Regarding balanced vs SE, how about if I want say 600V at the output. For SE, that means the volume pot will need to be turned to say position X. But for balanced, the pot will be turned to half of X, or basically the amp will need to amplify half as much? So keeping that in mind, won't distortions etc from the higher gain needed in SE affect sound? Whether you'll be able to hear the difference or not is another matter, I know 
	

	
	
		
		

		
		
	


	



 Just thought I'd throw that on the fire 
	

	
	
		
		

		
		
	


	


_

 

 Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes. I explained this in post a few pages back. 
	

	
	
		
		

		
		
	


	




 The distortion goes up slightly if you drive the same output with SE._

 

Wouldn't be better to add a "phase splitter"?

 A single ended phase signal enters the splitter and two signals, on in phase and the other out of phase sinal come out the splitter. 

 Does this increase single ended level and maintain volume pot at the same balanced position?

 Best regards,

 Jose Luis

 ps.: sorry, Alex already answered at post 617: http://www.head-fi.org/forums/6130256-post617.html


----------



## HeadphoneAddict

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Balanced vs. Un - that's another thread isn't it? That said - we did notice a difference with the proto at RMAF. even though there's not supposed to be a gain difference between the two inputs, we heard lower gain on the SE.

 Larry, did we ever listen to the dif's after we solved the source problem? I think it was only running balanced from my Opus the rest of the show.

 Sherwood has listened extensively SE, perhaps he could be cajoled into sharing his experience.

 I can A/B with my DAC Magic, but can't be sure of it's output stage topology differences between SE and Balanced._

 

The "dif's" ?


----------



## wiatrob

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_The "dif's" ?_

 

That's what we computer geeks call a 'difference' 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *jgazal* /img/forum/go_quote.gif 
_Wouldn't be better to add a "phase splitter"?_

 

And I think the addition of a phase splitter (while an excellent solution) would be beyond the scope of the requirements for this particular amp. 

 Luckily it's got spectacular price/performance.


----------



## pabbi1

Ok, ok, ok so I have a reading comprehension problem - completely missed the 51k load resistor - but (as luck would have it) I do have a 50k 5w - will that work, or do I need to cobble 2 extra 500r (10w-20w, iirc) resistors also (again, what I happen to have)?

 Always something.

 Oh, and if anyone is Jonesing to do a phase splitter, I have some interstage transformers that might interest you.


----------



## runeight

50k 5W is ok.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_That's what we computer geeks call a 'difference' 
	

	
	
		
		

		
		
	


	






 And I think the addition of a phase splitter (while an excellent solution) would be beyond the scope of the requirements for this particular amp. 

 Luckily it's got spectacular price/performance. 
	

	
	
		
		

		
		
	


	


_

 

I don't recall how the RCA inputs sounded vs the XLR, if that's what you mean. I do recall that the 5v from the stock PS Audio DLIII XLR was a bit too hot for the inputs, while the modded PS Audio XLR and Opus DAC were better.


----------



## Emooze

Hooked up my amp to the power supply finally. Everything is looking good. Going to check the offsets in a bit and then its listening time!

 Running at stats at a lower voltage should still work, correct? I never got around to rechecking the bias voltages and its way to wet and nasty out to go to the lab.


----------



## wiatrob

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_
 Running at stats at a lower voltage should still work, correct? I never got around to rechecking the bias voltages and its way to wet and nasty out to go to the lab._

 

Yes, if you're *SURE* it's lower voltage. running them at higher voltage might not be so good...


----------



## wiatrob

Ok, the hybrid is up and playing music. Completely immune to AC heater noise from my sloppy wiring too. 

 I think I might like it better than the sand amp. But it's too soon to tell. I only listened to 3-4 songs. All Rock, and this amp is _rocking_. Very similar to the sand amp, certainly sharing all the strengths. I'll let those tubes burn overnight and revisit tomorrow.

 Attached a picture to make Larry Cringe: - Uncased Amp Spoiler Alert!


----------



## Emooze

Very little drift, heatsinks are only warm to the touch. Bias at ~500 +/- 10V for safety right now.

 Gentlemen, it sounds fantastic. I've never heard electrostatics before until right now but I think I like them. Just using my iPod with lossy files, certainly has more detail, much less resonant (big issue with ambient music) and there's definitely lots of nice punchy bass. To say that I'm impressed would be an understatement. I'll have some more impressions after more listening and I get everything all cased up.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Ok, the hybrid is up and playing music. Completely immune to AC heater noise from my sloppy wiring too. 

 I think I might like it better than the sand amp. But it's too soon to tell. I only listened to 3-4 songs. All Rock, and this amp is rocking. Very similar to the sand amp, certainly sharing all the strengths. I'll let those tubes burn overnight and revisit tomorrow.

 Attached a picture to make Larry Cringe: - Uncased Amp Spoiler Alert!_

 

Thanks for the update!


----------



## Sathimas

My Stax SR-303 arrived today - I never heard a Stax before ...

 Bought the headphone "blind" and borrowed an amp from a forum-fellow.

 Well - this is simply amazing!

 So my decision to build the eXStata is now definitely, hope there will be boards soon.

 Other important question:
 Will somebody offer kits?

 I'm living in Germany and some parts might be hard to get for me.


----------



## audionut

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_Very little drift, heatsinks are only warm to the touch. Bias at ~500 +/- 10V for safety right now.

 Gentlemen, it sounds fantastic. I've never heard electrostatics before until right now but I think I like them. Just using my iPod with lossy files, certainly has more detail, much less resonant (big issue with ambient music) and there's definitely lots of nice punchy bass. To say that I'm impressed would be an understatement. I'll have some more impressions after more listening and I get everything all cased up._

 

Emooze, Which stats are you using??


----------



## runeight

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_My Stax SR-303 arrived today - I never heard a Stax before ...

 Bought the headphone "blind" and borrowed an amp from a forum-fellow.

 Well - this is simply amazing!

 So my decision to build the eXStata is now definitely, hope there will be boards soon.

 Other important question:
 Will somebody offer kits?

 I'm living in Germany and some parts might be hard to get for me._

 

If/how another round of boards or kits will be made available is not determined yet.


----------



## Sathimas

So I'll just hope...

 There are not too many diy- stat-amps out there that fit my budget.


----------



## Coreyk78

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_Ahh ok. I blame it on obscure TV tubes messing with my brain... 
	

	
	
		
		

		
		
	


	


_

 

OT, but a good use of some "worthless" TV tubes here DCPP Amp

 Back on topic, I've been listening to my Exstata pretty much daily since I got it up and running and it continues to impress! 
	

	
	
		
		

		
		
	


	




 It does put out a little bit of heat, enough to get the top of my Par-Metal case a little warm to the touch after its been on for a few hours, so I would recommend at least some ventilation when folks are casing one of these up.


----------



## Emooze

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Emooze, Which stats are you using??
	

	
	
		
		

		
		
	


	


_

 

A pair of Lambda Nova Classics, Pro Bias


----------



## Keithpgdrb

Listening Impressions are coming soon.. I can feel it. Lets get some excitement going so we can get that next set of boards ordered. I'm kicking myself for just not picking up the boards and waiting.


----------



## runeight

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_OT, but a good use of some "worthless" TV tubes here DCPP Amp

 Back on topic, I've been listening to my Exstata pretty much daily since I got it up and running and it continues to impress! 
	

	
	
		
		

		
		
	


	




 It does put out a little bit of heat, enough to get the top of my Par-Metal case a little warm to the touch after its been on for a few hours, so I would recommend at least some ventilation when folks are casing one of these up._

 

Yes. Just as a reminder the sand amp burns about 35W and the hybrid about 50W. Both should have good ventilation.


----------



## runeight

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Ok, the hybrid is up and playing music. Completely immune to AC heater noise from my sloppy wiring too. 

 I think I might like it better than the sand amp. But it's too soon to tell. I only listened to 3-4 songs. All Rock, and this amp is rocking. Very similar to the sand amp, certainly sharing all the strengths. I'll let those tubes burn overnight and revisit tomorrow.

 Attached a picture to make Larry Cringe: - Uncased Amp Spoiler Alert!_

 

Just a question. Are the heatsinks on the front taller than the ones in the back?


----------



## runeight

Quote:


  Originally Posted by *Keithpgdrb* /img/forum/go_quote.gif 
_Listening Impressions are coming soon.. I can feel it. Lets get some excitement going so we can get that next set of boards ordered. I'm kicking myself for just not picking up the boards and waiting._

 

I sure hope so. These guys are awfully quiet.


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes. Just as a reminder the sand amp burns about 35W and the hybrid about 50W. Both should have good ventilation._

 

That high? I thought that since the 270AX (480V @ 58mA = 27.84VA) is sufficient, power usage would be below 30W.

 I hope my custom 30VA unit is not going to be pushed too hard


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_That high? I thought that since the 270AX (480V @ 58mA = 27.84VA) is sufficient, power usage would be below 30W.

 I hope my custom 30VA unit is not going to be pushed too hard 
	

	
	
		
		

		
			



_

 

You should be ok Beefy, they are usually (at least good ones like SumR and E-P) built conservatively so you should really have 33-35Va... I know Jack's rated conservatively so they don't get too hot. He explained it at to me over the phone and it shot over my head.


----------



## runeight

Well, maybe I remember wrong. 
	

	
	
		
		

		
		
	


	




 Too many amps going.

 Negative rail 41mA x 300V = 12W

 Positive rail 36mA x 300V = 11W

 So the sand amp is 23W. Good catch.

 Heaters 2.4A x 6.3V = 15W

 The hybrid amp is 38W.

 This is less than other amps that might be available for diy so far as I know.


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Just a question. Are the heatsinks on the front taller than the ones in the back?_

 

Nope, that's just the poor iphone camera lens barrel distortion


----------



## wiatrob

Hmmm. I hooked up the 270AX to test PS's with the recommended load resistors for the beta amp and dialed voltages no problem.

 I was not able to do so with the hybrid board I tested last night - the negative rail just faded out and i couldn't dial it up to 410mV.

 Ya know, I migt have actually tested the PS's with my triads. You're right Runeight, there are a lot of versions floating around...


----------



## Beefy

Something I would test......

 Connect up the tube heaters, but connect the ±300V to load resistors instead of the amp.

 Disconnect two tubes, and re-test. Disconnect the remaining two tubes, and re-test. At what point does it start regulating properly?

 [EDIT] Actually, I'd go the other way round. Set it all up with the resistors without tubes connected, add two tube heaters and re-test, add the final two heaters and re-test.


----------



## runeight

If we assume a proper primary voltage, then the 270ax should work for either amp.

 For the SS, the transformer will be relatively unloaded and the HV secondary will be, should be, more than needed.

 However, when the heater supply is fully loaded then the HV secondary will pull down some. How much depends on a few things, but it should still be enough.

 If the LEDs go out for the hybrid then I think that just re-dialing the trimpots should bring it back.

 However, if the line side drops or is low then the 270ax in the hybrid may show an HV secondary that is also too low.


----------



## wiatrob

Line conditions have been a problem here in the past. Let me check secondary and primary volatges..


----------



## runeight

The weekend is upon us gents. Any of you care to provide more in depth listening reviews? I'd just like to know how we're doing.


----------



## Beefy

Can't help you out on listening impressions, but my parts from Mouser did arrive today. I had no idea the reservoir caps were so huge 
	

	
	
		
		

		
		
	


	




 Off to a great start with the heatsinks...... of 8 pins on the big sinks, 3 came out clean, 2 sheared off clean, and 3 just crunched down into a big mangled mess


----------



## Keithpgdrb

someone send me their exstata, and I'll start listening Right Away!!


----------



## studeb

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_The weekend is upon us gents. Any of you care to provide more in depth listening reviews? I'd just like to know how we're doing. 
	

	
	
		
		

		
		
	


	


_

 

Well, as a start, in a feat of super herculean strength i moved the amp from the assembly countertop with minidisc as source to my main rig. As the R2R had interconnects handy i plugged them in and loaded up Frank Sinatra's Strangers in the Night. Hmmm. Interesting choice i know. Actually i wanted to listen to Summer Wind.
 Anyways, i can still make the same comments i have before, fabulous bass extension and control. For me, there is a lot of "where-did-that-bass-line-come-from" with this amp. Not just slam but also detail, i could hear the upright bass in space if you will, its body resonating. I also reaslied how bad Frank "sounds" on the first two tracks. The rest of the ochestra sounded great. Detail-a-plenty to go around. This must be what a reavealing amp can do. I'll mate it with the rest of the rig and report back.

 If you have't built yours yet. GET GOING!!! Its worth every bit of effort.


----------



## looser101

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Can't help you out on listening impressions, but my parts from Mouser did arrive today. I had no idea the reservoir caps were so huge 
	

	
	
		
		

		
		
	


	




 Off to a great start with the heatsinks...... of 8 pins on the big sinks, 3 came out clean, 2 sheared off clean, and 3 just crunched down into a big mangled mess 
	

	
	
		
		

		
		
	


	


_

 

If you have access to a vise... find a piece of rod that will go in the top side of the heatsink pin hole with a little bit sticking out. Put a piece of wood with a hole on the other side where the pin sticks out. Tighten the vise to push the pin out by the pushing force on the rod you inserted. If you can't find something suitable to use as a rod you can try and find a couple largish finishing nails with the appropriate diameter (cut off the heads and file ends flat) and just stick 2 down the hole.


----------



## wiatrob

Quote:


  Originally Posted by *Keithpgdrb* /img/forum/go_quote.gif 
_someone send me their exstata, and I'll start listening Right Away!! _

 

PM me, that can probably be arranged now.


----------



## Beefy

Quote:


  Originally Posted by *looser101* /img/forum/go_quote.gif 
_If you have access to a vise... find a piece of rod that will go in the top side of the heatsink pin hole with a little bit sticking out. Put a piece of wood with a hole on the other side where the pin sticks out. Tighten the vise to push the pin out by the pushing force on the rod you inserted. If you can't find something suitable to use as a rod you can try and find a couple largish finishing nails with the appropriate diameter (cut off the heads and file ends flat) and just stick 2 down the hole._

 

Thanks, I was definitely going to try something like this next.

 I would just drill the little buggers out, if it weren't for the fact that some of them sheared off so messily...... the drill bit will likely just wander off the top and right into the soft aluminium.


----------



## Keithpgdrb

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_PM me, that can probably be arranged now. 
	

	
	
		
		

		
		
	


	


_

 

PM sent


----------



## fierce_freak

Would this work the way I think it would (allow proper volume control for switched rca and xlr inputs)?


----------



## runeight

Yes, this would work. As you know you just want to be careful that you don't load your source when the rheostat is near zero ohms.

 Here's something to consider though:

 In a normal vol pot configuration, if the Zi of the amp is very high (true for the exstata) then the source sees a nominally constant load as you sweep the volume pot which is the full resistance of the pot.

 In your design, for any reasonable value of the series resistors that I can think of, your source will see a widely varying load. Depending on the source you may notice SQ effects from this. OTOH, you may not. 
	

	
	
		
		

		
		
	


	




 For example, if the series resistors are 5k each and the pot is 50k, your balanced souce will see 60k at full volume and 10k and zero volume. Ignoring the Zi of the amp for this estimate. Your SE source will see 55k at full volume and 5k at zero volume.


----------



## fierce_freak

I had considered the load on the source and hadn't thought it would get quite that low. I'll have to take that into consideration as I decide on a volume control for the amp. I appreciate the insight.

 My mouser order should be here early next week, so hopefully I can get working on it soon and have my ESP950's singing ;D


----------



## sergery

*Mini-impression:*
 I have listen to the SS amp paired with some SR-303's for a short while now. Wow! The sound they produce is very energetic. Not only this, but complete, to my ears it really doesn't have any obvious weaknesses. I was expecting a killer attack, holographic soundstage, and wimpy bass. What we ended up with here is something strong and natural sounding, definitely good. Very good control over the different voices/instruments. I would definitely recommend this combination.

 Btw, single ended has plenty of gain.

*Edit:*Note this is on the prototpe


----------



## HeadphoneAddict

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_PM me, that can probably be arranged now. 
	

	
	
		
		

		
		
	


	


_

 

Can I get one to listen to also?


----------



## runeight

Maybe you need to take a drive into the Front Range to see exactly what wiatrob is doing? Perhaps he's making it all up.


----------



## pabbi1

Quote:


  Originally Posted by *sergery* /img/forum/go_quote.gif 
_mini-impression:
 I have listen to the SS amp paired with some SR-303's for a short while now. Wow! The sound they produce is very energetic. Not only this, but complete, to my ears it really doesn't have any obvious weaknesses. I was expecting a killer attack, holographic soundstage, and wimpy bass. What we ended up with here is something strong and natural sounding, definitely good. Very good control over the different voices/instruments. I would definitely recommend this combination.

 Btw, single ended has plenty of gain._

 

I also noted some synergy with this amp and the Stax 303 (and even 202), so I think it actually raises the bar with the "lesser" electrostats. Now, it also loves the he60, so, c'mon you guys with the OII - I have my thoughts, but, let's hear yours... 

 Is that the proto or your current version?


----------



## wiatrob

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Can I get one to listen to also? 
	

	
	
		
		

		
		
	


	


_

 


 If you want your amp in my proto case, (IOW wait a bit for the input select) you can listen tomorrow


----------



## sergery

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Is that the proto or your current version?_

 

Thanks, this is all only on the prototype which differs slightly. *note added


----------



## Beefy

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_What about this, for the more advanced students 
	

	
	
		
		

		
		
	


	




 In addition to the 12V supply you guys are already using, you could take a 9V battery and strap a 10K trimmer across that and use it to vary Vgs. Then, adjust the trimmer until you get say 10mA Id then write down the Vgs measurement at that point. Then group by Vgs._

 

I fall in the less advanced category, but would like to give this a shot anyway. I found your previous thread here and assume you were suggesting a version of Pass' circuit, but I can't quite get my head around exactly how it would need to be wired up. Any suggestions?

 Oh, and what sort of power supply are people using for the Idss matching? I have a 12V/4A switcher for a T-amp that I need to replace the plug on, so was thinking this would do the trick while it is chopped up.


----------



## digger945

The eXStatA Electrostatic Amplifier <--According to Alex, Idss matching to within 10% should be used here, with devices having a mimimum of 10mA(or no less than 10mA)

 The 271 is a P-channel. In another related thread we used a 10-ohm resistor in series with the drain(same location as the DMM in the diagram above) and just measured the voltage across that 10-ohm resistor and used ohms law to calculate the current.


----------



## Beefy

Yeah, I know how to do the Idss matching 
	

	
	
		
		

		
		
	


	




 The Vgs matching proposed by luvdunhill is an additional/improved matching measure. Check out his post linked here, and the few posts before and after.


----------



## luvdunhill

sure, I can post a circuit. It will be a day or so, today is my 4-year olds much anticipated birthday party, so I'm otherwise consumed. 
	

	
	
		
		

		
		
	


	




 I hope he likes JFETs!


----------



## BoilermakerFan

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_sure, I can post a circuit. It will be a day or so, today is my 4-year olds much anticipated birthday party, so I'm otherwise consumed. 
	

	
	
		
		

		
		
	


	




 I hope he likes JFETs!_

 

My son turned 4 in early October. Tell him daddy's friends said Happy Birthday.

 You know, the Cavalli Audio logo on the top of a 9" round cake would look awesome!


----------



## digger945

Luvdunhill's method is to vary the voltage from the PS used for testing until you get the desired current for the device under test, then measure the voltage across the gate and source.
 A simplified circuit would be like the one in the attachment at the bottom of this post.

 In my estimation, you would be way ahead to Idss match first, then Vgs match from those.


----------



## les_garten

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_sure, I can post a circuit. It will be a day or so, today is my 4-year olds much anticipated birthday party, so I'm otherwise consumed. 
	

	
	
		
		

		
			



* I hope he likes JFETs!*_

 

It's all in the presentation!

  Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_My son turned 4 in early October. Tell him daddy's friends said Happy Birthday.

*You know, the Cavalli Audio logo on the top of a 9" round cake would look awesome!*_

 

That's what I'm talkin' bout!


----------



## Beefy

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_sure, I can post a circuit. It will be a day or so, today is my 4-year olds much anticipated birthday party, so I'm otherwise consumed. 
	

	
	
		
		

		
		
	


	




 I hope he likes JFETs!_

 

No rush at all


----------



## wiatrob

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_...
	

	
	
		
		

		
		
	


	




 I hope he likes JFETs!_

 

They look quite nice strewn across cakes!


----------



## runeight

Is there anyone who has requested a board who has not received one yet? Everyone outside the US has boards?


----------



## les_garten

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_They look quite nice strewn across cakes! 
	

	
	
		
		

		
		
	


	


_

 

I'll bet designer Colors would sell great!


----------



## Emooze

You know, that sounds great actually. For my next build I want bright red FETs.


----------



## Beefy

Quote:


  Originally Posted by *looser101* /img/forum/go_quote.gif 
_If you have access to a vise... find a piece of rod that will go in the top side of the heatsink pin hole with a little bit sticking out. Put a piece of wood with a hole on the other side where the pin sticks out. Tighten the vise to push the pin out by the pushing force on the rod you inserted. If you can't find something suitable to use as a rod you can try and find a couple largish finishing nails with the appropriate diameter (cut off the heads and file ends flat) and just stick 2 down the hole._

 

Worked a treat - thanks! I used "common 3d" nails (37mm long, 2mm wide), cut to the appropriate length. Heatsinks are now all tapped and ready to go


----------



## looser101

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Worked a treat - thanks! I used "common 3d" nails (37mm long, 2mm wide), cut to the appropriate length. Heatsinks are now all tapped and ready to go 
	

	
	
		
		

		
		
	


	


_


----------



## HeadphoneAddict

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_If you want your amp in my proto case, (IOW wait a bit for the input select) you can listen tomorrow 
	

	
	
		
		

		
		
	


	


_

 

I don't mind waiting a little longer. 
	

	
	
		
		

		
		
	


	




 I also still owe you for the case and input selector, (and case, resistors/caps, etc for the Corda Cross)...


----------



## wiatrob

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_I don't mind waiting a little longer. 
	

	
	
		
		

		
		
	


	




 I also still owe you for the case and input selector, (and case, resistors/caps, etc for the Corda Cross)..._

 

I know you're good for it. I really want you to hear this amp though. I could loan you Sherwood's while I finish yours.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I know you're good for it. I really want you to hear this amp though. I could loan you Sherwood's while I finish yours. 
	

	
	
		
		

		
		
	


	


_

 

I shall not incur the wrath of Sherwood by pillaging his gear.


----------



## wiatrob

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_I shall not incur the wrath of Sherwood by pillaging his gear. 
	

	
	
		
		

		
		
	


	


_

 

He hasn't been beating down my door for this. Although judging from how long he hung on to my proto - I think you might have a point.


----------



## n_maher

I finished populating my hybrid amp boards today so with a little luck I'll get to work on air wiring the whole thing this week for some additional testing and chassis layout work.


----------



## pabbi1

Finishing up my chasis work in the next couple of hours, then powering up. This is probably the most blinged eXStata to date, so, pics in just a bit. About $400 in parts.


----------



## runeight

And I keep waiting for someone, anyone, to report on a more extensive review.


----------



## les_garten

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Finishing up my chasis work in the next couple of hours, then powering up. This is probably the most blinged eXStata to date, so, pics in just a bit. About $400 in parts._

 

We're on the edge of our seats AL!


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Finishing up my chasis work in the next couple of hours, then powering up. This is probably the most blinged eXStata to date, so, pics in just a bit. About $400 in parts._

 

What resistors did you use?


----------



## n_maher

Well, the easy part is done.


----------



## wiatrob

Fires right up Nate. Heater wiring will probably be a little _easier _with the boards split apart.


----------



## pabbi1

Dayum eet... ok, dialed in to the spec, 360 +, 410 -, T1/T3 to G is 332v, VOut is 297v on both + and -... but...

 First, some pics:
















 Now, the but... I caught a whif of smoke early on (before the channels were balanced (to the extent one LED wasn't on. Have had it on another 5 minutes with everything dialed in, thinking whatever it was would go ahead and crisp out. Heatsinks all ok to the touch, and the whisp looked to come from close to R7/R8, but nothing since - guess I'll measure and watch.


----------



## les_garten

@Pabbi!: What attenuator is that?


----------



## n_maher

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Fires right up Nate. Heater wiring will probably be a little easier with the boards split apart._

 

Not sure how this week is going to go schedule wise so it may have to wait to get power applied until after Xmas unfortunately. But the important thing was to get it all together so that I could start laying out the chassis component since that is going to take some serious effort. 

 Al, looks great man. Is it me or does the resistor in the lower left hand corner of the board look a little stressed? Could just be the flash but the center of the body looks like it's been overheated.


----------



## pabbi1

Sharp eye Nate, but... they are actually different colors, the top being blue, and the bottom being gray.

 Les, that is an Acoustic Dimensions unit (Edit: Acoustic-Dimension, high-end audio and components for tube audio ) 41 step, with a custom 50k attenuation - part of the bling. The Stax jack is the teflon with gild pins courtesy of luvdunhill, as is the detented delrin knob.

 Case is rosewood and granadillo, I think.

 Well, I let it cook for 20 minutes, and it held pretty steady. One odd thing is that the positive rail led is very bright, all the way from 340mv to 365, where the negative rail is ok at 410, dull at 405, and off completely at 400mv - clue?


----------



## runeight

This means that the current draw from the negative rail load resistors is a little higher than expected. I think you have a different resistor here?

 When the amp is connected, with less draw, the LEDs should light about the same.


----------



## luvdunhill

speaking of jacks, everyone who sent me money so far will have one dropped into the the mail in the next day or so (if they are not already mailed). I won't be able to get anymore until after the New Year, but I'll try and scrounge around for a few more parts and probably can get 1 or 2 more. PM me if you're interested.


----------



## manaox2

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_speaking of jacks, everyone who sent me money so far will have one dropped into the the mail in the next day or so (if they are not already mailed). I won't be able to get anymore until after the New Year, but I'll try and scrounge around for a few more parts and probably can get 1 or 2 more. PM me if you're interested._

 

Looks like your PMs are full, but I'd love to get two of those jacks for my upcoming builds, after the New Year is fine.


----------



## n3rdling

I wouldn't mind getting 2 as well if available.


----------



## BoilermakerFan

I'm considering the use of E-P PVA iron for my attenuator on one, maybe both, builds. 

 Edit: Nevermind, I need to make up the correct schematic first...


----------



## digger945

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I'm considering the use of E-P PVA iron for my attenuator on one, maybe both, builds. 

 Here's Jack's schematic:
Electra-Print.com PVA Passive Audio Pre-Amplifier

 I know the 4PDT balanced/SE switch would be before the PVA Primary and I'm not planning to use leg with the 1K resistor to a bass amp. 

 Any issues with the plan?_

 

Very interesting, and affordable.
 Input wiring would be a little different for this type of setup.


----------



## BoilermakerFan

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Very interesting, and affordable.
 Input wiring would be a little different for this type of setup._

 

The secondary wiring is incorrect for balanced. I have to draw it out...


----------



## minivan

just fired up my ss version last night, very good detail with good extension on both end. 

 anyone live near me wish to audition the amp before their build can pm me for time arrangmement


----------



## BoilermakerFan

OK, I cleared up the schematic for the PVA preamp attenuator:

 LMK if there will be issues since it has a gain of 2 for preamp use to my F5s. The 4PDT on the Balanced/SE will be before the primaries and the 4PDT for the eXStata/Preamp will be after the RK27, I just didn't draw them in and the SE drawing I forgot to label the two series resistors as 5K, but they're the same...








 EDIT: Have to thank cetoole for the idea and all the help getting the wiring correct. 

 The 1:2 PVA transformers are $55 each from E-P. So for under $150 I have a pretty nice preamp attenuator.


----------



## n_maher

Quote:


  Originally Posted by *minivan* /img/forum/go_quote.gif 
_just fired up my ss version last night, very good detail with good extension on both end. 
]Imageshack - estatass - Uploaded by triseven_

 

Interesting use of the Neutrik D housing to hold the Stax jack. Does that actually work out ok?


----------



## digger945

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_OK, I cleared up the schematic for the PVA preamp attenuator:_

 

Are the 5k's really necessary? The reason I ask is because I dunno 
	

	
	
		
		

		
		
	


	



 I was thinking we would see something where the only resistance was in the shunt element of the circuit.
 I'll be trying this soon to listen for meself. Already have some transformers, just need some time.




  Quote:


 The 1:2 PVA transformers are $55 each from E-P. So for under $150 I have a pretty nice preamp attenuator. 
 

I like the price.


----------



## BoilermakerFan

.


----------



## BoilermakerFan

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Are the 5k's really necessary? The reason I ask is because I dunno 
	

	
	
		
		

		
		
	


	



 I was thinking we would see something where the only resistance was in the shunt element of the circuit.
 I'll be trying this soon to listen for meself. Already have some transformers, just need some time._

 

Without the series resistors in place, mimicking the schematic from the E-P site and only using the single 10K pot while bringing the secondary's grounded point high as IN- with the wiper going to IN+; the signal is only balanced at full volume, with no attenuation going on at all. Turn it down a bit though, and you have a resistor divider on the + phase, but nothing on the - phase. This still provides a constant 10k load to the _transformer_, because the transformer just sees the impedance across the whole conductive track of the pot, but not the amp's signals are unbalanced as soon as the pot is turned down. 

 Now, with the schematic I posted, the one with the series resistors and the pot used as just a variable resistor, we have a fixed series element on both phases, but the shunt varies. When the pot is at 10k (all the way up), we get 6dB attenuation. As we turn the pot down, the shunt element gets smaller, so the attenuation increases equally for both phases and we stay in balance. 

 And we get to use a single ALPS or Nobel stereo pot instead of quad.


----------



## pabbi1

Ok, found my psu faux pas... well, at least the symptoms - its r16:






 While it would give off a whisk every now and then, it never failed with the psu running for 20 minutes - and where the left rail would drop a few mv, and I'd crank it back up... where the led was dying. All making more sense. I was almost convinced the wisps were cat hair or some stray saw dust (hey, it happens - at least it wasn't stray aluminum shavings).

 Well, except for what the root cause might be?

 And, an obligatory money shot:


----------



## les_garten

Nice Looking Build AL! Can't wait to hear your thoughts on the Sound.


----------



## gilency

Al's SS prototype sounds wonderful with my Sigma Pros. There is plenty of volume . I can't listen if I turn the know all the way up. I have to remove the SP's from my ears. There is zero distortion at max volume.
 It sounds energetic with lots of bass and plenty of detail.
 Kudos to Alex, Al and Nick.


----------



## runeight

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Ok, found my psu faux pas... well, at least the symptoms - its r16:

 While it would give off a whisk every now and then, it never failed with the psu running for 20 minutes - and where the left rail would drop a few mv, and I'd crank it back up... where the led was dying. All making more sense. I was almost convinced the wisps were cat hair or some stray saw dust (hey, it happens - at least it wasn't stray aluminum shavings).

 Well, except for what the root cause might be?

 And, an obligatory money shot:
_

 

This is hard to diagnose. Since the LED does light there is current in Q7/Q8. But for this resistor to burn also means that too much current has passed through it which means that during power up something is awry.

 I think you have to check all of the transistors in the shunt portion of the negative (edit) rail. Make sure they are the right polarity. And check the zener string too.

 This would be Q7,Q8,Q11,Q12. And then if everything checks out you might have to replace the CRD (R14). Is the CRD in the right orientation? If you don't have one handy for replacement you can temporarily run with 4k7 resistor in this spot.

 EDIT: I meant to say negative rail and I've edited the post.


----------



## n_maher

That resistor doesn't look cooked in the traditional sense, looks more like it was damaged by force or perhaps just flawed to begin with? As a first try I'd remove it and replace it in kind and monitor the voltage drop across it during the initial power up. That is of course after checking the parts that Alex suggested to make sure it isn't simply a current over-load situation.


----------



## runeight

Good catch Nate. You might very well be right and it would save Al mucho work.


----------



## pabbi1

Saving Al mucho work is a good thing... 

 IIRC, that resistor looked funky from the get go, so I'll replace it to see if I get lucky. The zeners are all oriented correctly, and I'll recheck everything else. That said, it wouldn't dial in right otherwise - or am I just being, well, optimistic?

 Oh, and are there any other points to measure to see if something else is awry? And, maybe a higher value resistor, say .5 or .75w - or is that just squeezing the baloon?


----------



## runeight

Measure R12. Should be near 150V. Higher wattage is not needed. If everything is working properly 1/8W is 10X more than required.


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Measure R12. Should be near 150V. Higher wattage is not needed. If everything is working properly 1/8W is 10X more than required._

 

It's hard to tell from the picture, but it seems that that resistor is too big to fit. Perhaps using a properly sized resistor would help prevent this, as I agree, it seems that the damage was done before power-up.


----------



## pabbi1

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_It's hard to tell from the picture, but it seems that that resistor is too big to fit. Perhaps using a properly sized resistor would help prevent this, as I agree, it seems that the damage was done before power-up._

 

Nope, the exact correct size resistor (RN55), but remember it looked a little funky before I even bent the leads. Question is, was that my last one, and ignored the visual oddity because of? 

 That said, I have never actually broken a resistor (but have burned up a few), and shy away from PRP as they are (allegedly) a bit more brittle. 

 Always freaking something.


----------



## luvdunhill

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Nope, the exact correct size resistor (RN55)_

 

hm, the pitch looks a bit small for a RN55 to me at least.


----------



## Beefy

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_That said, I have never actually broken a resistor (but have burned up a few), and shy away from PRP as they are (allegedly) a bit more brittle._

 

I have had one, just one, RN55 do that exact same thing. It 'cracked' as I was bending the leads with pliers prior to installing it in the board.


----------



## wiatrob

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Nope, the exact correct size resistor (RN55), but remember it looked a little funky before I even bent the leads._

 

Comparing it to the one next to it - that's a tight bend or there is something funky with it. good catch, easily fixed, and no catasrophic fail.

 FWIW, I hand bent all the RN55s on my boards and they were perfect fits. I did have a few problems with those larger tan resistors, they're pretty soft casings...


----------



## BoilermakerFan

.


----------



## n_maher

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I have had one, just one, RN55 do that exact same thing. It 'cracked' as I was bending the leads with pliers prior to installing it in the board._

 

 Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Nope, the exact correct size resistor (RN55), but remember it looked a little funky before I even bent the leads. Question is, was that my last one, and ignored the visual oddity because of? 

 That said, I have never actually broken a resistor (but have burned up a few), and shy away from PRP as they are (allegedly) a bit more brittle. 

 Always freaking something._

 

With these boards having the pitch _exactly_ the right size for the resistor body I find that it's much better practice to bend the leads by hand. Just squeeze the leads one at a time and you should get a good fit. Using pliers that close to the resistor body is a recipe for a cracked casing which is what it appears happened in that picture. I've had it happen and usually it's while abusing a resistor that I'm trying to remove so I don't care. But really, the RN55s aren't hard to break if you apply much force or any sort of sharp edge.


----------



## sergery

Quote:


  Originally Posted by *gilency* /img/forum/go_quote.gif 
_Al's SS prototype sounds wonderful with my Sigma Pros. There is plenty of volume . I can't listen if I turn the know all the way up. I have to remove the SP's from my ears. There is zero distortion at max volume.
 It sounds energetic with lots of bass and plenty of detail.
 Kudos to Alex, Al and Nick._

 







 Let's not forget, thanks Frank! 
	

	
	
		
		

		
		
	


	




 Alex, on the resistor topic, would you consider making the hole spacing just a hair wider for some of these resistors on whatever next revision of board makes it? A lot of them have to be bent very sharply in order to fit.

 Al, your layout looks very nice. With any luck you will be up and running soon too.


----------



## luvdunhill

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_With these boards having the pitch exactly the right size for the resistor body_

 

Again, IMHO and all that, but that's too small. Despite the potential mechanical issues, I like to have to have room for grabber probes and what not..


----------



## BoilermakerFan

Then why not use the 1/4W Vishay CMF50 series... Nearly identical to the RN55s, but smaller.

 Or if you must populate with TOTL or OTT, the Caddocks will fit nicely too.
	

	
	
		
		

		
		
	


	




 EDIT: BAH! The CMF50 is only 200V rated.


----------



## pabbi1

Oh, most certainly mine should not be the only one about to come up... after all this is my 4th one, even if the first was stillborn.

 Funniest thing - I have NEVER bent a single resistor, ever, with pliers or other metal tool - always by hand, and mostly against the inside of my thumb, and sometimes against the fingernail JUST to make sure I never crack the resistor. As I say, first one I've ever even seen damaged. Now maybe rolled the desk chair over it or the dog chewed it - or somesuch.

 Indeed, much thanks to Frank - who might need a couple of proto boards, along with, say, some mercury vapor rectifiers? 

 Speaking of, c'mon slackers - Alex deserves quite a bit more (positive) feedback than has been given to date. We have been gifted far better a design than we deserve, and have naught to say?


----------



## digger945

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Then why not use the 1/4W Vishay CMF50 series... Nearly identical to the RN55s, but smaller._

 

That's what I was thinking, and they're a perty blue to boot.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Speaking of, c'mon slackers - Alex deserves quite a bit more (positive) feedback than has been given to date. We have been gifted far better a design than we deserve, and have naught to say?_

 

I can deal with being a slacker. My parts are slowly trickling in... I will start building as soon as everything is here. marc's jacks showed up yesterday, your transistors a few days before that, digger's wire arrived today. Digi-Key order goes in tonight...

 Percy Audio order on Friday... 

 I'm more of a tortoise than a slacker. Always moving forward, just slowly sometimes.


----------



## BoilermakerFan

.


----------



## Beefy

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Speaking of, c'mon slackers - Alex deserves quite a bit more (positive) feedback than has been given to date. We have been gifted far better a design than we deserve, and have naught to say?_

 

Only got my boards today, and I won't get my transformer until after Christmas, but I'm trying!


----------



## scompton

My boards for my sand amp are populated, but I had some minor surgery. I don't want to play with high voltage while distracted by pain. I'll get back to it after Christmas.


----------



## Emooze

Ok I'll see what I can do for impressions. My background is primarily a Grado SR80 and JVC RX700 on an M3 straight from my laptop. Same for the eXStata. I'm using Lambda Nova Classics on the SS eXStata with a maxed PS.

 First impression was that this setup was astonishingly clear. Almost painfully so on a bad recording/rip. One thing I notice (might be my ears) is that if there's a particularly complicated song, it's hard to pick out individual details on all my other cans. Not so here. I could tell you each instrument being played and focus on just that one. The clarity might end up being a bad decision because it hasn't punished me by being liberal with the volume yet. Cranking it another degree never subtracts from the sound. I don't think I could stand the volume at which this amp distorts nor do I want to find out.

 One thing that is gone but I think is just from using electrostatics is resonance. I listen to some ambient electronic music and I hate when a note is obviously overemphasized somehow and it becomes really annoying. Haven't heard that so far.

 I wouldn't consider the sound to be particularly bright or harsh though. I get the impression that it might be a bit darker than my Grados. The highs aren't painful when I reach that critical level but they're definitely still there. The Grado's can reach well down into sub bass but the stat's just have so much more. Not more to the point where it sounds like some badly tuned car sub but with a punch that reminds me of a good 8" subwoofer. I heard someone once say on listening to thunder "it doesn't rumble, it cracks." That would be a good way to describe the way this sounds.

 Vocals scare me, Frank Sinatra whispering into my ear is a bit disconcerting the first time around. The JVC's are unbelievable on vocals and I didn't think it could get better but this is just soooo much better.

 From a new guy to stats talking to those looking into it; go for it. And then beg Alex to make more of these, this is definitely the amp to start with. To those who have been around stats, maybe you can comment on what I'm hearing is the phones or the amp but I am so glad I chose to do this.

 Few technical details: Running the amp open air right now, heatsinks never get more than warm to the touch. I think the M3 got hotter. There is little to no noise at all. All I hear is definitely the noise from my laptop. The triads have a little mechanical hum but I cant tell unless i put my ear to them.

 Questions? Comments?


----------



## pabbi1

Gonna start posting my prior love notes to runeight... maybe that will motivate folks a bit... originally posted elsewhere on Oct 30:

 Just listened to Radiohead's 'Packt Like Sardines in a Crushd Tin Box'. This is a defining experience for this amp. It literally created a total equilibrium imbalance for me there was so much going on - that I have NEVER heard in the 100 listenings of that piece before. 

 Normally I'd chalk this up to mushrooms, acid flashback, food poisoning or H1N1, but no - on second listen, it is just stunning. The entire 'Amnesiac' disc is just a treat.

 When this group gets their build on, Katy bar the door.

 Good stuff, Alex.


----------



## pabbi1

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Is it me or does the resistor in the lower left hand corner of the board look a little stressed? Could just be the flash but the center of the body looks like it's been overheated._

 

Boy, how dare I dispute that? You were/are, of course right. r24 now has charcoal bands, with no color at all. I *think* I used 68k 3w resistors. r23 looks fine.

 r12 is exactly 150v, and the replaced resistor is holding fine, no smoke, with about 20 minutes of cook time. 

 Fairly stable on both channels, with a few mv drift on the "bad" channel.

 LED works fine, but is that resistor burning because I (perhaps) have the LED backwards (long lead to +)?


----------



## sumo-kun

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_From a new guy to stats talking to those looking into it; go for it. And then beg Alex to make more of these, this is definitely the amp to start with. To those who have been around stats, maybe you can comment on what I'm hearing is the phones or the amp but I am so glad I chose to do this._

 

Interesting because I had a similar experience when I first started into stats a few years ago with my 303 + 313 amp combo. They came one day as I was about to go out but I was so curious I just had to plug them in. The only nearby source was a PS2. I started up a game and the PS2 logo sound came up. I was thinking I connected the stax up wrong because I was SURE the sound came from the TV. But it was from the phones. First thing that came to me was the soundstage and the clarity. Everything was also nice and crisp and open. I thought bass was lacking at first but then I found it was there but just really well controlled and defined. Voices were smooth but maybe a bit harsh sometimes with females. I'd say it was a very similar experience to what you had. So with that in mind I would maybe attribute a good chunk of the SQ gains you got to the stats.
 But reading other posters' comments, it seems that the exStata is actually a very nice amp 
	

	
	
		
		

		
			





. This has me really interested because I would like a (cheap) upgrade from my 313. So, has anyone familiar with stats got any views on the exStata? I'm pretty sure its better than my 313 but I'd still like to read some opinions 
	

	
	
		
		

		
		
	


	




 Also, YES to more boards! Pleeeaaasssseee!!


----------



## runeight

You know, the value for R23/R24 was calculated for the nominal filter voltage of around 325-330V. If you have much higher than that then these resistors will get quite a bit hotter than I had expected.

 The original calculation was:

 330V / 75k = 4.4mA

 330V * 4.4mA = 1.5W

 3W is cutting it close, but should be ok.

 However, if the filter voltage is higher because of the transformer and the resistor value is lower then we might get this:

 350V / 68k = 5.2mA

 350V * 5.2mA = 1.8W

 The difference between 1.5W and 1.8W is not that great, but generally it's good to stay below half the power rating and even less under most circumstances.

 In this latter case it would be better to find small 5W resistors and to squeeze them in.


----------



## pabbi1

I have 5w 50k in that size, but will look to see what I can find in 75k. I even have plenty of room to go offboard (hang over the side) as needed.


----------



## Emooze

Quote:


  Originally Posted by *sumo-kun* /img/forum/go_quote.gif 
_So with that in mind I would maybe attribute a good chunk of the SQ gains you got to the stats._

 

Hmm you're most likely right.

 If anyone's in Massachusetts with a different 'stat rig that wants to compare, I'm sure we can find a way. Let me know please.

 Edit: I should probably case it up before that but still let me know.


----------



## TimJo

From the Stax thread....

  Quote:


  Originally Posted by *gilency* /img/forum/go_quote.gif 
_I have been comparing the eXStata with the SRD7mk2 tonight. Whether is Jack Johnson or Bach's chorales, there is a definite difference in the level of detail, bass and overall sound richness. I will keep the transformer box as a back up, but for day to day listening the eXStata wins hands down. Bach's organ works resonate with a deep rumbling bass which reminds me of a live organ performance. (My local church has a beautiful Casavant organ I listen to every weekend). Vocal solos are sweet and realistic.
 Couldn't be happier with the sound....for the time being... 
	

	
	
		
		

		
		
	


	


_

 


http://www.head-fi.org/forums/f113/s...ml#post6241475


----------



## TimJo

A quick update. Still waiting on my stats to arrive. I've been told two more weeks (via Yama). It's killing me to have this amp sitting here and no way to listen. As a matter of fact, I am almost thinking about getting some ESP 950's because my faith in a delivery from Japan is waning...


----------



## wiatrob

TimJo,

 if you had let me know, I would've loaned you a pair. I know I've promised people here listening opportunities, and I know Larry and Sherwood are waiting patiently for their Beta amps.

 I've had some unexpected work duties, and since it's bonus time., they're taking up a bit more of my time. But I have a week and a half off starting next Tuesday, so I'll knock these out and we can get some more impressions.


----------



## wiatrob

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_Hmm you're most likely right.

 If anyone's in Massachusetts with a different 'stat rig that wants to compare, I'm sure we can find a way. Let me know please.

 Edit: I should probably case it up before that but still let me know._

 


 That said, after you have some more experience listening to various stats, you'll realize this amp _is _special. We're blessed here in Colorado with generous Head-Fi'ers who own an abundance of high end stats and amps, and audio shows with both.


----------



## Hopstretch

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_Hmm you're most likely right.

 If anyone's in Massachusetts with a different 'stat rig that wants to compare, I'm sure we can find a way. Let me know please._

 

I think we can make that happen.


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_You know, the value for R23/R24 was calculated for the nominal filter voltage of around 325-330V. If you have much higher than that then these resistors will get quite a bit hotter than I had expected.

 The original calculation was:

 330V / 75k = 4.4mA

 330V * 4.4mA = 1.5W

 3W is cutting it close, but should be ok.

 However, if the filter voltage is higher because of the transformer and the resistor value is lower then we might get this:

 350V / 68k = 5.2mA

 350V * 5.2mA = 1.8W

 The difference between 1.5W and 1.8W is not that great, but generally it's good to stay below half the power rating and even less under most circumstances.

 In this latter case it would be better to find small 5W resistors and to squeeze them in._

 

I've changed to 480VCT transformers from the original 500VCT and I was planning to keep the 291V Zener string, but should I bump R23/R24 from the 75K to 80K?


----------



## runeight

With 480V I think you can use the 75k/3W. You can move to 82k, but then your LED current will decrease to 330V / 82k = 4mA. Probably still bright enough for you to see.

 Power will be around 1.3W.

 I have run my sand amp for hours and hours (testing offsets) with a 270AX with no ill effects on these resistors.


----------



## BoilermakerFan

Looking at the Hybrid boards and the heater wiring, is there any reason why I couldn't wire the 4 heaters in series to run them at 12.6Vdc?

 I have dual 6.3V secondaries of my power transformer and nice little regulated DC PSU board.


----------



## pabbi1

There are a few auctions of interest atm for matched construction 6s4a - I have no ties to any of these, but kind of unique.

* 4 NOS/NIB RCA 6S4A 6S4 TUBES TESTED BLACK PLATES - eBay (item 370308320188 end time Jan-16-10 14:37:18 PST)

 And, there are currently some bargains for the value conscious consumer - with a tube tester, of course...


----------



## luvdunhill

Hey Al, how do the new amps with HE-60 compare to Alex's old ES-1/SR-Ω combo?


----------



## runeight

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Looking at the Hybrid boards and the heater wiring, is there any reason why I couldn't wire the 4 heaters in series to run them at 12.6Vdc?

 I have dual 6.3V secondaries of my power transformer and nice little regulated DC PSU board._

 

You should not do this because of the built-in heater biasing circuit.


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_You should not do this because of the built-in heater biasing circuit._

 


 Thanks Alex. I'll just keep it 6.3Vac...


----------



## pabbi1

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Hey Al, how do the new amps with HE-60 compare to Alex's old ES-1/SR-Ω combo?_

 

Boy, you'd trust my memory? And, I am sure this is a set-up, but, I'll bite. 

 Actually, I never heard that combo, for two reasons - a) Alex would not (and reasonably so) bring the Omega to a meet, and b) he sold them (in 1q2007 iirc) before I got a chance to hear them at his house, oh, and before the amp developed Singlepower-itis.

 I was VERY familiar with that particular amp, as Rob let me listen to it on several occasions, at meets and his house, both with his OII, and with my he-60. The amp also had a very pricey set of Telefunken driver tubes, which was, as one would imagine, superb - and, all told that amp cost about $4500.

 Caveat: IMHO!!!!

 So, to hold anything ceteris paribus (from my fading memory, with declining capacity, and creeping tinnitis) it would be fairer for me to eval against the BH or even your KGSS. It compares favorably with those amps (my source, and the he-60), but no specific areas better or worse except IIRC the bass on eXStata is better than either KG design (of the builds I've heard, my tubes, my source, my music selection, my areas of interest, etc), and, from what i can tell, no weaker in any area. 

 I know this differs from your experience with the OII and the SS proto version, but we do need a LOT more A/B, with better overall critical listening conditions.

 Now, IFF Vulcan will power up, and actually run (given it's 3x places I could have screwed up, not to mention just it's wiring scheme), then I can make a truer comparison side by side, and maybe BH will benefit from angelic intervention (found a shipping box!!!), and that will be available by the January Dallas meet IFF the tranny isn't burned (the SumR unit spec'd for Vulcan can be used in BH worst case).

 BUT, I have not heard my latest version (JUST got back from picking up the LED resistors at Tanners, and should have all that sorted by early evening), so I will be really vocal about comparisons, with a complete SWOT analysis as soon as I think it is burned in - hopefully by Monday. I could not do that with the proto, and my reservations there led directly to the ccs in this version - all so I can listen to 'Tool' with impunity, or, extreme prejudice.

 Now, I REALLY cannot wait to have the take-it-to-the-mat discussions regarding flavor of 6s4a (hey, at least we are only arguing about ONE tube), whether Tung-Sol or Amperex or some odd matched getter/flashing version is best, not to mention what happens with cryo... 

 So, in summary, no opinion - iirc, Alex raved about he-60 with BH, then liked the ES-1/SR-Ω combo better, albeit after paying about $8.5k for the amp and phones, and had a second pair of SR-Ω at $4kish, so he was rather heavily invested. Not that the $ expenditure EVER influences our opinions about how something sounds...


----------



## luvdunhill

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_So, in summary, no opinion_

 

heh, not a setup at all. Just never thought to ask about it


----------



## pabbi1

Good idea though - getting Alex's opinion on eXStata - and something for us to accomplish at the Dallas meet as I understand there will now be a BHSE in attendance as well.

 OK, off to some errands, then hopefully get this party started... again.


----------



## runeight

I trust that this Alex you're talking about is not me?


----------



## pabbi1

No, Alex @ apuresound. Now, had it been you, we' might have _started_ at the 1400Vpp spec...


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_No, Alex @ apuresound. Now, had it been you, we' might have _started_ at the 1400Vpp spec... 
	

	
	
		
		

		
		
	


	


_

 

Ask him why he's not making cables for the ESP/950s anymore, you know, if you can casually work it into the conversation. Something subtle like, "Hey Alex, why aren't you making cables for the 950s anymore? Now that DIY'ers are saving so much money with the eXStata, they have money for a great cable to really make the 950s sing..." 

 Thanks Al.


----------



## pabbi1

OK, everything is dialed in, but my rails are at 311/312. About 15 minutes plus at this point. 

 With the resistor load, T1/T3 to ground was 330. rails 305v (T1/2 and T3/4 were right at spec).

 Just for reference, I used 100k 3w for r23/r24, and the led is plenty bright to indicate power. The 68k left a nasty scorch on the board, but no pad nor trace damage - again with my line voltage, 269jx, etc.

 I'll mention that to Alex, but he's offline atm (I have him on IM) - I'd be real surprised if it is anything more than lack of good flat cable, but I need to know for my brother anyway.

 Oh, and another motivation shot - eXStata #4 lives.


----------



## Emooze

Quote:


  Originally Posted by *Hopstretch* /img/forum/go_quote.gif 
_I think we can make that happen. 
	

	
	
		
		

		
		
	


	


_

 

I think we should just make it a straight up Massachusetts-area meet if you're down. Haven't had one in a while.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_OK, everything is dialed in, but my rails are at 311/312. About 15 minutes plus at this point. 

 With the resistor load, T1/T3 to ground was 330. rails 305v (T1/2 and T3/4 were right at spec).

 Just for reference, I used 100k 3w for r23/r24, and the led is plenty bright to indicate power. The 68k left a nasty scorch on the board, but no pad nor trace damage - again with my line voltage, 269jx, etc.

 I'll mention that to Alex, but he's offline atm (I have him on IM) - I'd be real surprised if it is anything more than lack of good flat cable, but I need to know for my brother anyway.

 Oh, and another motivation shot - eXStata #4 lives._

 

Thanks Al. The story I heard was concern about voiding the warranty, which it doesn't since Koss has a No Questions Asked LTW policy. I'd just have to take the cable off before shipping them in... I haven't talked to or asked Alex directly, but since you know him, it was easier that way.


----------



## pabbi1

Listening with the electrets (SR-40), and will allow a few hours burn in with them (well, or as long as I can stand it before plugging in the he-60). Wired my pot diametrically opposite of the attenuation curve (yes, Marc, as you knew I would), but will sort that out later on today, even if it "works" now.

 But, she is up and running, making even the most humble stats sound good. Who said electrets don't have any bass or soundstage? Looks like my 'spare' Hybrid will be finding a new home.

 Oh, and for you guys sitting on the sidelines _hoping_ Runeight does another board run, you might want to start an interest check thread to start collecting names, and versions desired (SS or Hybrid), as it will take some serious love (quite appallingly missing so far) to convince him this effort is worth continuing. 

 So many toys, and it isn't even Christmas yet. Thanks Santa Alex!


----------



## les_garten

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Listening with the electrets (SR-40), and will allow a few hours burn in with them (well, or as long as I can stand it before plugging in the he-60). Wired my pot diametrically opposite of the attenuation curve (yes, Marc, as you knew I would), but will sort that out later on today, even if it "works" now.

 But, she is up and running, making even the most humble stats sound good. Who said electrets don't have any bass or soundstage? Looks like my 'spare' Hybrid will be finding a new home.

 Oh, and for you guys sitting on the sidelines _hoping_ Runeight does another board run, you might want to start an interest check thread to start collecting names, and versions desired (SS or Hybrid), as it will take some serious love (quite appallingly missing so far) to convince him this effort is worth continuing. 

 So many toys, and it isn't even Christmas yet. Thanks Santa Alex!_

 

Did you wire your POT as a shunt? If so, what R did you use on the inputs?

 Actually, I'll take that back but leave it standing, you didn't wire THAT pot as a shunt, did you?


----------



## pabbi1

Nope, just backwards - just need to change the IN and the G to catch the smaller side of the resistor chain.


----------



## Beefy

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Oh, and for you guys sitting on the sidelines _hoping_ Runeight does another board run, you might want to start an interest check thread to start collecting names, and versions desired (SS or Hybrid), as it will take some serious love (quite appallingly missing so far) to convince him this effort is worth continuing._

 

I sincerely believe it *is* worth it - before I have even started applying solder. I haven't been this excited about a DIY build since my very first project 
	

	
	
		
		

		
			





 The impression I am getting is that there is a severe case of DDIY..... _don't_ do it yourself. Now I'm FAR from independent when it comes to this business and still need a lot of hand-holding (just ask luvdunhill, I've lost track of how many PM's I've sent him in the last month 
	

	
	
		
		

		
		
	


	




), but soooooo many people just want to take the easy way out and just get a kit. And when the BOM is so plainly available, it is just plain lazy and entirely defeats the purpose.

 I really hope more people pluck up the intestinal fortitude to demand more boards, and do their builds under their own steam.


----------



## Emooze

It's definitely worth it to build this amp. Easily cheaper than nearly all the electrostatic energizers and amps available and I'm willing to bet sounds better than anything double the price.

 It would be a serious waste to let all the work done by everyone not amount to anything.


----------



## manaox2

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Oh, and for you guys sitting on the sidelines _hoping_ Runeight does another board run, you might want to start an interest check thread to start collecting names, and versions desired (SS or Hybrid), as it will take some serious love (quite appallingly missing so far) to convince him this effort is worth continuing._

 

Seriously? I've been holding out for 'testers' to finish so that I can get in on the first official board run. I bought parts in preparation and really want this to happen. I didn't know it being released officially was still in question.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Listening with the electrets (SR-40), and will allow a few hours burn in with them (well, or as long as I can stand it before plugging in the he-60). Wired my pot diametrically opposite of the attenuation curve (yes, Marc, as you knew I would), but will sort that out later on today, even if it "works" now.

 But, she is up and running, making even the most humble stats sound good. Who said electrets don't have any bass or soundstage? Looks like my 'spare' Hybrid will be finding a new home.

 Oh, and for you guys sitting on the sidelines _hoping_ Runeight does another board run, you might want to start an interest check thread to start collecting names, and versions desired (SS or Hybrid), as it will take some serious love (quite appallingly missing so far) to convince him this effort is worth continuing. 

 So many toys, and it isn't even Christmas yet. Thanks Santa Alex!_

 

I'm definitely looking forward to recabling my Kenwood KH-82 electrets and removing the undersized transformers. They're a really special headphone and I can't wait to lift the restrictions off their performance! 

 I agree with Beefy and Emooze, I think the amp is just awesome for the value. I'm confident in the design and the initial impressions that I decided to spend more money and upgrade to custom E-P PS iron, E-P PVA transformer attenuator, boutique resistors, matched SJ74s, alt. C3676s, luvdunhill's gorgeous Stax jacks, Vampire XLRs, and larger heatsinks. Waiting on all the parts has been tough, but I'm doing the chassis layout, front panel, and steel work while I wait. Heck, I'm even ordering custom paint for mine... It will have a permanent home in my system with the F5s, Shigaclone, AudioSector phono stage and USB DAC. 


 Just the reports of the great bass out of the Koss 950s on this amp has me very excited about buying a set and recabling them, then putting them into custom cups and headband. I'm using Kabeer's stock pair for auditioning after I run them in... Then I get to hear HE60s after Tachi sends me the drivers and cable for his custom headband. 


 Starting to browse for a set of SR-40s too. I really can't wait to haul my eXStata to CanJam in June so I can audition those other great Stax and Beyers on it. 


 I'm building the Hybrid for another Head-Fi'er and know he's really looking forward to his amp for his Koss 950s too. 

 The Christmas season has probably slowed down many of the other builders, so I wouldn't take the lack of reviews to date as an indication of a lack of interest. I think we're all taking more time in the planning stage because it is higher voltage and we want to make sure we build it right the first time, with the best parts we can afford. 

 I know there are several who want to build their own and there are several who want the amps built for them because the HV has them concerned. 

 I'd put my name in the hat for another set of both boards, and I have interested buyers for two more complete Hybrids.


----------



## fierce_freak

Can anyone suggest a place to find stax extension cables at a good price (need to recable Koss)?


----------



## BoilermakerFan

Quote:


  Originally Posted by *fierce_freak* /img/forum/go_quote.gif 
_Can anyone suggest a place to find stax extension cables at a good price (need to recable Koss)?_

 

X2! I actually need (2) Stax cables...


----------



## pabbi1

HE-60 time. 

 Pity you guys aren't here. So sad to enjoy something, and not be able to share.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_HE-60 time. 

 Pity you guys aren't here. So sad to enjoy something, and not be able to share._

 

Once mine is up and running, I'll send you my address again.


----------



## Keithpgdrb

I'm absolutely in on the next run of boards. still waiting for some actual comparisons between the hybrid and ss to decide which I would attempt to build. although I may also be in the "have one built" camp.


----------



## Sathimas

About an Interest-Check-Thread:

 I'm also very interested in the eXStata, as I already said there are only few electrostatic DIY Amps out there for a smaller budget.
 The eXStata is an option for people who'd like to enjoy their music with electrostatic headphones, but have not so much money.

 I can only vaguely imagine how much work it is to find a good (and good sounding) design and bring it to the point where the eXStata is atm.
 I think the hours invested are beyond counting - just think of the support in this forum which is only *one *part of it all!



 I would also like to start an interest check but could hardly handle some kind of group buy since I live in Germany.
 (I think most of the possible buyers live in the US)
 I would definitely organize a group-buy for Germany - I would already have 3 people wanting a set of boards and I think there will be more.

 I would be willing to open and organize and IC-Thread - where should this thread be opened (which sub-forum)?


----------



## les_garten

I would think GlassJar would get into this if it were an option for them?

 How about this for a Transfo for the Hybrid? The R80-17 Model listed in the auction.

R-Core

 I was thinking of Paralleling the (2) 6.3v outputs to get up to the req. 2.5A?


----------



## Sathimas

I already wrote J.Rossel of glassjar and asked about the eXStata.

 He said that at the moment he is busy with the things he's selling and won't take the eXStata in his shop.

 Maybe if a lot of people ask him he'll change his opinion, but this is what he said about a week ago.


----------



## pabbi1

Well, let's get boards before there is discussion on kits... 
	

	
	
		
		

		
		
	


	




 I have opened an IC poll here.


----------



## luvdunhill

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Well, let's get boards before there is discussion on kits... 
	

	
	
		
		

		
		
	


	




 I have opened an IC poll here._

 

typically, this isn't allowed in this forum. I'd recommend talking with mod about the appropriate way to do this here at HF.


----------



## runeight

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_About an Interest-Check-Thread:

 I'm also very interested in the eXStata, as I already said there are only few electrostatic DIY Amps out there for a smaller budget.
 The eXStata is an option for people who'd like to enjoy their music with electrostatic headphones, but have not so much money.

 I can only vaguely imagine how much work it is to find a good (and good sounding) design and bring it to the point where the eXStata is atm.
 I think the hours invested are beyond counting - just think of the support in this forum which is only *one *part of it all!



 I would also like to start an interest check but could hardly handle some kind of group buy since I live in Germany.
 (I think most of the possible buyers live in the US)
 I would definitely organize a group-buy for Germany - I would already have 3 people wanting a set of boards and I think there will be more.

 I would be willing to open and organize and IC-Thread - where should this thread be opened (which sub-forum)?_

 

Gentlemen, thanks for the expressions of interest. Let's see how the beta group does. In the meantime, please don't start an IC thread without asking me first.


----------



## runeight

I see that one has already been started. I'm not sure what the next steps will be folks and I am reluctant to get people's hopes up too early.


----------



## runeight

And one more request, please don't pursue this any further with Jeff at Glass Jar. He has his hands full.


----------



## sergery

Well, thought I would check in. My PSU came up after I replaced a few parts, looking healthy and stable now though. Numbers look like this with a 369 JX, 291V zener string.

 Line voltage: 122.3 VAC
 Secondaries: ~268 VAC
 T1-T2: 360 mV
 T3-T4: 410 mV
 Positive Rail: +299.9 V DC
 Negative Rail: - 300.3 V DC
 T1 and T3 to ground ~340 VDC

 I have my amp board populated save Q11/Q12 which I need to scrounge up some mounting hardware for. After I get some hardware I will try for a setup.


----------



## pabbi1

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_typically, this isn't allowed in this forum. I'd recommend talking with mod about the appropriate way to do this here at HF._

 

Mods can yank it should they, or Alex, decide to do so. 

 I disagree that collecting data / opinions is not allowed in the DIY forum.

 EDIT: And though I disagree in the strongest terms, I have also asked that thread be closed, and deleted.


----------



## sumo-kun

Awww, no more boards would make me sad


----------



## les_garten

How about this for a Transfo for the Hybrid? The R80-17 Model listed in the auction.

R-Core


----------



## BoilermakerFan

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_How about this for a Transfo for the Hybrid? The R80-17 Model listed in the auction.

R-Core_

 

Those R-cores will work. Spritzer linked it many pages ago. The better model is the R80-36 using the 230V secondaries. The R80-17 would work, but would have to use a 300V Zener string instead of the 291V string.


----------



## les_garten

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Those R-cores will work. Spritzer linked it many pages ago. The better model is the R80-36 using the 230V secondaries. The R80-17 would work, but would have to use a 300V Zener string instead of the 291V string._

 

Hmmm, interesting. I was just trying to do a close match to the 269JX.


----------



## sergery

My amp came together fine too. I am waiting on my headphones - has been taking forever, that's ok. I was lucky enough to get loaned a pair of SR-303's with one driver that is only 60% for smoke testing. Even into the equivalent of 1.5 ears the sound is astonishing. This amp has phenomenal control. 

 I think people have been overly modest with respect to bass when discussing stats, but is could be this amp as I have found it to be satisfying in this respect - and I had my doubts! Picture getting punched in the face, but by a silk gloved hand. The sound is a combination of strength and finesse. I suppose it isn't a challenge for stats to adapt - that is change the direction of the diaphragm and accelerate it. That low end models reach to 35 KHz. Actually the sound of the system reminds me a little of K701, which also reaches very high. Maybe it is a coincidence though.

 The beta hybrid seems to sound very similar to the proto SS - at least to my memory. It is hard to pick out anything that sounds markedly different. I do think the hybrid sounds a little bit 'smoother', shall we say. The overall sound signature though is very much the same, perhaps side by side there would be obvious differences.

 I have listened to a few tracks with extensive percussion (Amon Tobin). The amp handles tons of voices REALLY well. I can't wait to be able to use both ears and listen to some orchestral music and live music.

 I will give some more impressions when I have listened both more thoroughly and with a fully functioning headset.


----------



## bidoux

Quote:


  Originally Posted by *sumo-kun* /img/forum/go_quote.gif 
_Awww, no more boards would make me sad 
	

	
	
		
		

		
		
	


	


_

 

Same here


----------



## Currawong

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Oh, and for you guys sitting on the sidelines _hoping_ Runeight does another board run, you might want to start an interest check thread to start collecting names, and versions desired (SS or Hybrid), as it will take some serious love (quite appallingly missing so far) to convince him this effort is worth continuing._

 






 Stax baby would like 2 please.


----------



## runeight

Several of you have written to me privately about my comments above. Re-reading them I can see why there is some confusion. 
	

	
	
		
		

		
		
	


	




 There also seems to be some background chatter about whether or not I am trying to commercialize this amp. The suggestion to do this was made by one or two individuals on the early team. I thought about it, but not that long ago I seriously looked into commercializing some of my other designs and a few that have not been made available to the diy community. As nearly all of you know the step from diy to commercial is large and the time committment and committment to customer service is significant. My consulting practice is not feast or famine, but it does have its slow periods and its very intense periods.

 I am about to enter, after the first of the year, a very intense period with several clients and critical deliverables. I will be out of town for much of the first two months. Hence some hesitancy on my part to another round of boards.

 The other reason that I didn't try to commercialize this amp is that I had signed up for ericj's request and there was, when we finally had a working amp, an obligation to return it back to this community. If I had intended to commercialize the amp at this time I would never have made the post that started this thread.

 But, I will make another round available if we can do it quickly and then after that things will have to wait.

 At this point it's hard to gauge interest, but I'm happy to make 10 more SS and 10 more hybrid sets. Price should be similar to before because these are re-do of the boards. Boards will be identical. To make the boards available to as many as possible, only one board set per builder. And new builders only for the same reason.

 When this buy is finished, because of the two week lag time, we will be into Jan. My response time then will be slower than it has been lately.

 PM me and we'll see how much sign up there is in the next week or two. If we can get 20 buyers then I will place the order.


----------



## wiatrob

Also, to help alleviate the crunch, I am going to release my beta Hybrid board set, still bare. (I am just keeping my Beta sand version). 

 And will soon interest check both my follower modded sand and beta amps as mostly complete but caseless, for parts cost (or less). I wanted to give this group a heads up before I post to the general thread. PM me with any questions or interest...


----------



## runeight

One thing I need to remind everyone about. The boards are paneled. There is one SS and one hybrid per panel. When I order 10 panels I will have 10 of each amp. I'd like to have all 20 (or very close) of these committed before the buy. This would mean that some of you will have to sign up for the SS amp.


----------



## pabbi1

Well, can you add one extra psu, as I have an extra set of (old) amp boards? And, I guess I need to look into breadboarding that ccs mod for them, and the living other Hybrid.

 That set of older hybrid boards is available, along with many parts toward a (REALLY) budget build.

 Oh, and I have just started the impressions thread. Maybe folks would care to add to it.


----------



## sachu

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Oh, and I have just started the impressions thread. Maybe folks would care to add to it._

 

Alex, probably sticky this in the first post of this thread and also link to it on your website perhaps.


----------



## luvdunhill

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Well, can you add one extra psu_

 

well, if they're panelized already as Alex said above, I'd guess not. 

 Good idea with the impressions thread


----------



## pabbi1

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_well, if they're panelized already as Alex said above, I'd guess not. 

 Good idea with the impressions thread 
	

	
	
		
		

		
		
	


	


_

 

I _think_ it is just the amp board, at least hope so. 

 And, we need to have you listening to the current version with the OII - Merry Christmas, indeed.

 Now, off to flip the switch on Vulcan after a lunch with my charming wife.


----------



## runeight

Gents, you guys have been very fast on filling up the hybrid order. I have 8 hybrid requests and 1 sand request. And more sand takers?


----------



## Keithpgdrb

Is one of these easier to build than the other?


----------



## sergery

Here is the beast, housed in some a defunct spectroscopy command unit - not the prettiest but it is functional. I still need to buy a drillbit for the stax jack. I have been considering getting a front panel made. How much would something basic run at FPE without engraving? Go easy, I haven't built many amps.


----------



## wiatrob

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Well, can you add one extra psu, as I have an extra set of (old) amp boards? And, I guess I need to look into breadboarding that ccs mod for them, and the living other Hybrid._

 

IMO, breadboarding the CCS isn't worth it. I have never really heard the lower volume distortion the CCS' were intended to mitigate, the follower mod would provide most of the performance increase with lower parts count...


----------



## wiatrob

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Also, to help alleviate the crunch, I am going to release my beta Hybrid board set, still bare. (I am just keeping my Beta sand version)...snip..._

 

All spoken for.


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Gents, you guys have been very fast on filling up the hybrid order. I have 8 hybrid requests and 1 sand request. And more sand takers? 
	

	
	
		
		

		
		
	


	


_

 

Lift the previous builder restriction and I'll take another sand board kit. 
	

	
	
		
		

		
		
	


	




 I'll build it for a HF'er wanting the amp, but not the DIY part.


----------



## runeight

Quote:


  Originally Posted by *Keithpgdrb* /img/forum/go_quote.gif 
_Is one of these easier to build than the other?_

 

I would say that they are very close to the same build complexity. The hybrid version replaces a pair of transistors on each amp section with a pair of tubes and sockets and six additional resistors not on the sand board. Same number of heatsinks, but the follower heatink gets smaller.


----------



## Keithpgdrb

I may be looking for a builder for the hybrid when the next run comes up. if you are available, please PM me some details. I would like to know if I can go this route, or if I will have to covet my board till I have more skill and/or money.


----------



## runeight

Gents, there is one of you interested in a sand amp. The rest the hybrid. Altogether that's 9 amps. I will contact the fab tomorrow to see if we can make just a run of 10 hybrids (splitting the panel). If the cost is reasonable and if the one of you might agree to take a hybrid, then I'll get a best guess on the cost. If none of you object then we'll move this along quickly.

 If we go this route then there is only one set of hybrid boards left to be claimed in this next run.


----------



## runeight

Correction. That makes 10 amps. So the order is full. I will PM the one builder who asked for the sand amp.


----------



## minivan

been listening to my hybrid for the last few night, sound extremely good. i only have one psu, so can't compare the ss and hybrid side by side. may be the hybrid sound a bit more smoother, sweeter and little bit more spacious?




 someone mentioned the o2 clipping on the prototype version, i can't hear it on my beta version. the o2 became so loud before i turn the volume to max,but i can't hear clipping on bass neither on treble.
 my only concern is about the heatsinks on q13r/q14r and q13l/q14l. they become so hot after running for half an hour i can't touch them for more then 3 seconds. 

 about using the neutrik d housing for the amphenol stax jack, it work very well, both the amphenol jack and the stax plug fit like a glove in those neutrik housing. just have to file the d-shape hole of the neutrik housing a bit for the amphenol jack to fit through.

 have to say thanks to frank again here for sending me those amphenol jack


----------



## runeight

This is happening for two reasons. Minivan's rails are about 320V and the tubes are heating the heatsinks.

 I'd like to recommend to all hybrid builders that, if you are going to use the 3x100V zener string in the PS then sub [Edit]KSC5027 for Q13/Q14 on the amp boards. They are higher wattage devices and will withstand the temperature better. I don't know for sure, but I don't think your SQ will be affected.


----------



## runeight

Gents, here is the beta 2 list. I'll wait another day for more sand orders. If we get 10 of each then we'll go with the double order.

 If not, and if the fab says they can split the panel, I will get 10 hybrid boards. cetoole has first dibs on the last hybrid. If he says no, then currawong gets the last hybrid.

 The rest will have to wait. Sorry. No doubling up on this round.


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I'd like to recommend to all hybrid builders that, if you are going to use the 3x100V zener string in the PS then sub KSC5042 for Q13/Q14 on the amp boards._

 

Q13/14 are KSC5042 anyway......?


----------



## runeight

Sorry. I meant KSC5027. Long night and too early. I'm going to edit the post.


----------



## runeight

The other condition that minivan has is high heater voltage. So what we've got on these transistors is:

 1. Heatinks in close proximity to the tubes
 2. Tubes running hotter than normal
 3. Transistors buring more power from 20V more rail

 Just enough to make the heatsinks hotter than we would like them to be.


----------



## wiatrob

Quote:


  Originally Posted by *minivan* /img/forum/go_quote.gif 
_...someone mentioned the o2 clipping on the prototype version, i can't hear it on my beta version. the o2 became so loud before i turn the volume to max,but i can't hear clipping on bass neither on treble..._

 

This is the same experience I had, I can get the amp to clip easily. I just have to sit across the room with the cans off to listen for it...


----------



## luvdunhill

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_This is the same experience I had, I can get the amp to clip easily. I just have to sit across the room with the cans off to listen for it..._

 

wiatrob/minivan: what is your source output?


----------



## bidoux

Come on, where are all the solid states snobs ?


----------



## Emooze

I love solid state. Just a fascinating technology.

 My lovely amp is currently at my apartment because i couldn't figure out a way to transport it home safely.


----------



## Beefy

Quote:


  Originally Posted by *bidoux* /img/forum/go_quote.gif 
_Come on, where are all the solid states snobs ?
	

	
	
		
		

		
		
	


	


_

 

Everybody loves teh toobs! 
	

	
	
		
		

		
		
	


	




 For me, the lower height requirements, lower heat output, easier wiring etc. etc. more than makes up for any questionable/marginal differences in sound quality.


----------



## wiatrob

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_wiatrob/minivan: what is your source output?_

 

Here's the list I've tested with:


 PS audio dac, unmoded (balanced) (too hot output = clipping) 
 PS audio dac, Cullen mods(balanced) (not too hot output = no clipping)

 Opus Dac (balanced)
 Cambridge Dacmagic (balanced)(SE)

 Marantz CD 5001 (SE)
 Denon DCD-330 (Balanced)

 I believe Tyler has used his Peachtree nova DAC single ended with the proto as well - don't know if he experienced that clipping.

 Too hot a voltage output from your source WILL drive the amp to clip sooner. This is a peculiarty of the source, and not the amp, IMO.

 I haven't repeated the test with the unmodded PS audio dac - Larry will have to comment when he gets his hybrid next weekend... But there was like 6V across the balanced output, have to look back at my notes from RMAF.


----------



## wiatrob

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Everybody loves teh toobs! 
	

	
	
		
		

		
		
	


	




 For me, the lower height requirements, lower heat output, easier wiring etc. etc. more than makes up for any questionable/marginal differences in sound quality._

 

Agreed. The amps have a very similar character. I'm keeping my Sand version cause it's cooler, even though "i LOVE tubes..."


----------



## luvdunhill

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I haven't repeated the test with the unmodded PS audio dac - Larry will have to comment when he gets his hybrid next weekend... But there was like 6V across the balanced output, have to look back at my notes from RMAF._

 

interesting. Have you ever listened to an amp while on an oscilliscope to see what various types of clipping sound like? For example, a single-ended output stage, versus a push pull? Some people say they cannot hear clipping at all, but once you see it and correlate this versus what you're hearing, I think it becomes easier. 

 I'd like to see some measurements of this amp, but that seems to be so far down on people's list for some strange reason, that I'll have to probably do it myself


----------



## bidoux

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_For me, the lower height requirements, lower heat output, easier wiring etc. etc. more than makes up for any questionable/marginal differences in sound quality._

 

I agree with this too. Keep it simple is the rule !


----------



## ChrisX

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_So the order is full._

 

One day I didn't look into head-fi, now I'm already too late. 
	

	
	
		
		

		
		
	


	



 So count me in for the third run, if there will be one. In the meantime I will keep on reading all your listening impressions and building experiences. 
	

	
	
		
		

		
		
	


	




 Chris


----------



## BoilermakerFan

Quote:


  Originally Posted by *ChrisX* /img/forum/go_quote.gif 
_One day I didn't look into head-fi, now I'm already too late. 
	

	
	
		
		

		
			




 So count me in for the third run, if there will be one. In the meantime I will keep on reading all your listening impressions and building experiences. 
	

	
	
		
		

		
		
	


	




 Chris_

 

Or add your name to the SS boards. Enough people have said that they are similar enough, plus the SS is a little lower cost to build...


----------



## Keithpgdrb

because I dont know.. I ask. between the two amps, is there more maintenance for the tube amp? how long does a tube last, and how expensive is it? I agree that easier is better, but I dont want to compromise sound in the least bit.


----------



## bidoux

Quote:


  Originally Posted by *Keithpgdrb* /img/forum/go_quote.gif 
_ but I dont want to compromise sound in the least bit._

 

I think Exstata is about compromise. If you want the absolute best stat amp, go for BH or T2...


----------



## runeight

I don't think that this is necessarily true. The exstata is specifically designed to be simpler and not to reach the same peak to peak voltages (to make it an easier build), but it is NOT at all certain that these other amps sound better.


----------



## Keithpgdrb

Quote:


  Originally Posted by *bidoux* /img/forum/go_quote.gif 
_I think Exstata is about compromise. If you want the absolute best stat amp, go for BH or T2..._

 

those two amps are inaccessible for me. the exstata seems the best compromise that can be had. I should have worded my post differently. its really just another ss vs hb question.


----------



## runeight

Quote:


 I think Exstata is about compromise. If you want the absolute best stat amp, go for BH or T2... 
 

Folks, let's straighten this out a bit. There is a difference between compromise and intelligent engineering choices. Sometimes you just have to make compromises for any number of reasons. Sometimes you can make engineering choices that don't or barely limit a design at all.

 The exstata was specifically designed to be comparatively inexpensive and to be within reach for builders who may not have felt comfortable building the more expensive amps. Its design includes very conscious engineering choices. And, BTW, more expensive does not always mean better.

 The engineering choices made in this amp may not "compromise" its behavior at all in the operating region for which it is designed. Furthermore, the amp is very robust against build errors as the proto and beta teams can attest. Furthermore, when built right ti ALWAYS comes up to a functional condition. Furthermore, the boards are specifically designed to be small (you try that with 600V HV between traces) and to surround the HV component leads (as much as possible) with heatsinks so that you can't accidentally reach in and touch anything that will kill you. Those of you who have built the amp can see how this has been done.

 This amp and its boards are not something that were just thrown together.

 In its operating regime this amp may provide just as much or better SQ as do other amps. We shall see as the comparisons are made. But don't make flip assumptions about this now.

 So, before you make comments as above pay more attention.

 Edit: I've added the quote above because Keith's and my post hit simultaneously.


----------



## Coreyk78

I wanted to post a brief update, I finally got around to finishing up my Buffalo 24 DAC and have had a couple days to play with it. To my ears it was a substantial improvement over my modded Zero DAC and my Exstata/404 combo sound even better.

 I can't say enough how awesome this setup really sounds, I've caught myself looking over my shoulder across the room for what made a noise behind me, only to realize that it was part of the music. Pretty amazing experience really, the definition of big soundstage. The buffalo is also my first balanced source and I've tried running SE and balanced into my Exstata and honestly, I can't hear a difference, both sound excellent.

 Also the SS version gets my vote, I don't see how the tube version could beat this, I would guess they are on the same level, just slightly different recipes for the same pie.


----------



## les_garten

Quote:


  Originally Posted by *bidoux* /img/forum/go_quote.gif 
_I think Exstata is about compromise. If you want the absolute best stat amp, go for BH or T2..._

 

Ok, Ok, who turned off the TROLL filter again!


----------



## wiatrob

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_
 I'd like to see some measurements of this amp, but that seems to be so far down on people's list for some strange reason, that I'll have to probably do it myself 
	

	
	
		
		

		
		
	


	


_

 

As I've stated in the past, I'm not opposed to measuring - if a fairly inexpensive (or loaned _hint hint_) SG were available to me.

 That said - I think measurements are of limited usefulness in the 'audiophile' world. Can you see the difference a $25K power cable makes to an amp on a scope? I doubt it. Yet there are those who claim that they can hear a difference in SQ. But I think that discussion is for another thread.

 I am certainly _not _trying to challenge that distortion was heard with OIIs on the proto design. Many ears are more senstitive than mine - I've just never heard it, or if I have, it's not been any sort of distraction from the overall superior SQ of this amp design.


----------



## wiatrob

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_Ok, Ok, who turned off the TROLL filter again!_

 


 So tempting, though, isn't it!


----------



## sachu

In my limited experience, the BH wasn't as good an amp for the Koss ESP950 as the eXStatA is. I am only referring to the ESP950 as that's the one I have the most listneing time on in electrostats. 
 The BH just lacked the bottom end. 
 With the BH they were just nice sounding phones. Once i had my eXStatA going they truly transformed the ESP950 into a different beast. My full impressions are in the first few pages of this thread.

 I still have two eXStatAs to test here. One sand and one hybrid, build no 4 and no 5 respectively. WIll get around to testing them before Chirstmas.


----------



## BoilermakerFan

Quote:


  Originally Posted by *Keithpgdrb* /img/forum/go_quote.gif 
_those two amps are inaccessible for me. the exstata seems the best compromise that can be had. I should have worded my post differently. its really just another ss vs hb question._

 

Keith

 The amps were designed to be very similar and eliminate as much influence of particular tube construction variations as possible. The tubes themselves are very inexpensive when you consider you can get a quad for $15 or less. My decision to go SS over Hybrid for my personal amp was only because I wanted it to be as physically robust and easy to transport as possible. My eXstata will have it's own frequent flier number. 
	

	
	
		
		

		
		
	


	




 If I wasn't planning to take it with me around the country on occasion, I probably would have kept the Hybrid, but only because I would window my chassis and watch the tubes glow. It would be a decision based on an aesthetic or "look", not SQ. 

 The SS can be built for less than the Hybrid too, or you can put that savings into a few select boutique or source upgrades that "might" make it a more enjoyable listening experience for you. A $100 savings on the SS amp really won't be noticed if you flip that $100 into a better phono cartridge improving the source feeding the amp, IMHO.


----------



## wiatrob

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_Also the SS version gets my vote, I don't see how the tube version could beat this, I would guess they are on the same level, just slightly different recipes for the same pie._

 

On paper (er well, in the sims) the hybrid outperforms the sand version. barely. 
	

	
	
		
		

		
		
	


	




 Perhaps we'll soon have some measurements as well.


----------



## luvdunhill

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_As I've stated in the past, I'm not opposed to measuring - if a fairly inexpensive (or loaned hint hint) SG were available to me._

 

Alex has some absolutely beautiful measurements (both simulated and with some very fancy Tek scope) for some of his other designs on his website. Pete Millet and Ti have measurements for nearly every design on their respective websites. I'd like to see something like that. Why? It has absolutely nothing to do with how it sounds, or the worth of the design. For me, measuring a project is like casing it up for some people. It's just part of the process. I'm obviously in the minority on this one, but that's cool 
	

	
	
		
		

		
		
	


	




 I'd go up and Dallas and measure Al's, but I'm not exactly sure if my probes are up for the task. When I measured my other 'stat amps, I had a different scope that I cared a lot less for (i.e. invested a lot less money in) 
	

	
	
		
		

		
		
	


	




 My current probes are 1:1 (150 Vrms CAT 1, 6Mhz, 110pF, 1M) or 10:1 (300 Vrms CAT 2, 200Mhz, 17pF, 10M) and I'm not sure they would do a very good job at measuring this or any stat amp. Any advise Alex?


----------



## Emooze

If there aren't any measurements by the time I go back to school. I'm sure I can use the lab equipment we have. I might have to scrounge up a 100x probe but it is possible.


----------



## sergery

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_I'd like to see some measurements of this amp, but that seems to be so far down on people's list for some strange reason, that I'll have to probably do it myself 
	

	
	
		
		

		
			



_

 

What would you like to see? I am not a pro at measuring amps, but I have a function generator, test tracks, a decent scope, the amp of course. How is the measurement performed? I don't suppose there is enough current to loop-back through a resistor to drop some V's. Then again maybe there is? I suppose, as you suggest the capacitance's will have to be accounted for.


----------



## pabbi1

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Alex has some absolutely beautiful measurements (both simulated and with some very fancy Tek scope) for some of his other designs on his website. Pete Millet and Ti have measurements for nearly every design on their respective websites. I'd like to see something like that. Why? It has absolutely nothing to do with how it sounds, or the worth of the design. For me, measuring a project is like casing it up for some people. It's just part of the process. I'm obviously in the minority on this one, but that's cool 
	

	
	
		
		

		
		
	


	




 I'd go up and Dallas and measure Al's, but I'm not exactly sure if my probes are up for the task. When I measured my other 'stat amps, I had a different scope that I cared a lot less for (i.e. invested a lot less money in) 
	

	
	
		
		

		
		
	


	




 My current probes are 1:1 (150 Vrms CAT 1, 6Mhz, 110pF, 1M) or 10:1 (300 Vrms CAT 2, 200Mhz, 17pF, 10M) and I'm not sure they would do a very good job at measuring this or any stat amp. Any advise Alex?_

 

If Mohammed can't make it to the mountain, well... 

 I'm off all next week, and have both generations of hybrids we can measure... oh, and Vulcan can tag along, after a bit more work. I can even build out another JUST to measure, if needed.


----------



## spritzer

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_In my limited experience, the BH wasn't as good an amp for the Koss ESP950 as the eXStatA is. I am only referring to the ESP950 as that's the one I have the most listneing time on in electrostats. 
 The BH just lacked the bottom end. 
 With the BH they were just nice sounding phones. Once i had my eXStatA going they truly transformed the ESP950 into a different beast. My full impressions are in the first few pages of this thread.

 I still have two eXStatAs to test here. One sand and one hybrid, build no 4 and no 5 respectively. WIll get around to testing them before Chirstmas._

 

A linear amp is never going to make the ESP950 a bass monster since they are lean in the bass. That's why they are so well regarded as they do not have the woolly bass of the Lambdas and are much cleaner over all.


----------



## sachu

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_A linear amp is never going to make the ESP950 a bass monster since they are lean in the bass. That's why they are so well regarded as they do not have the woolly bass of the Lambdas and are much cleaner over all._

 


 hah...the lambda Pro at least which I owned had no bass to speak of..highly tilted towards treble piercingly so. I had to compeltely undamp them to get any kind of bass out of them and then it was just muddy, loose and all over the place.
 The Koss is by no means a bass monster and i didn't indicate it as such. however its abilities were at full or as close as they get in the stock enclosure when driven by the eXStatA rather than the BH.

 And the main difference is not even the bass, overall the Koss just sounded much better and in its element on the exStatA than on the BH.


----------



## studeb

The current state of the art:

 I hope to have a Pabbi style case made up during the holidays.


----------



## runeight

Well, as it turns out, splitting the panel will only add cost. At this point I will just get both amps and assume that they all will go out.


----------



## Beefy

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_In addition to the 12V supply you guys are already using, you could take a 9V battery and strap a 10K trimmer across that and use it to vary Vgs. Then, adjust the trimmer until you get say 10mA Id then write down the Vgs measurement at that point. Then group by Vgs._

 

I'm at this stage now and flying blind, so I'll just post my best guess and ask for corrections......









 First is for Idss, using two 9V batteries and a 10k trimmer to produce a 12V supply. Idss is measured as 1/10th the voltage across the 10ohm resistor.

 Second is for Vgs using a 9V battery and a 10k trimmer, which is adjusted to produce 20mV across the 20ohm resistor (1mA). Voltage is measured on a second meter.


----------



## runeight

That looks about right to me.

 Here's the latest beta 2 list. Need more sand builders.


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_That looks about right to me._

 

...... really? I felt sure I had the location of the voltmeter wrong for the Vgs, but couldn't work out how else it could possibly be done.


----------



## runeight

You're right, it's wrong. 
	

	
	
		
		

		
		
	


	




 You need and additional variable voltage source to provide voltage for the GS in parallel with your meter. Set the V- for 12V and then adjust the Vgs until you get 1mA in the load resistor. Then measure the Vgs and match them.


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_You need and additional variable voltage source to provide voltage for the GS in parallel with your meter. Set the V- for 12V and then adjust the Vgs until you get 1mA in the load resistor. Then measure the Vgs and match them._

 


 .......?






 I think I'm well out of my depth......


----------



## runeight

Unfortunately, the additional supply needs to bias the gate positive with respect to the source. You're gonna need another battery.


----------



## Beefy

Ugh, can someone please put me out of my misery and post the right way to do it?


----------



## macm75

Alex,
 Don't forget to add macm75 to the beta 2 list 
 Again, if there is a tube board open, I'll take it. If not, I would LOVE to build the sand version. Regards, Joe

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Here's the latest beta 2 list. Need more sand builders._


----------



## Beefy

Alright, back from Xmas shopping, how about this then?






 Gate is now positive to source by a variable - and measurable - amount.


----------



## runeight

I believe this one is right.


----------



## FrankCooter

I'll sign up for a set of the "sand" boards. Normally, I'm a member of the "use a transistor go to jail" school of audio, but I'm looking forward to making an exception here! Really impressed with your work and commitment, Alex!


----------



## digger945

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Alright, back from Xmas shopping, how about this then?






 Gate is now positive to source by a variable - and measurable - amount._

 

Whatever your Idss measurement is(from your first test), then that is going to be about the lowest current measurement your going to get(with the gate and source shorted together). For example, if you have one with a Idss of say 11mA, then as you lower the Vgs from a point where both gate and source are the same to something where the gate is seeing less potential than the source, then the current is only going to increase.
 For the 271 jfet, the max current will be at 0v Vgs, and the lowest current that will be flowing from drain to source at about 3v Vgs or higher(The 3v number is from the datasheet, it will probably vary from device to device).


----------



## Beefy

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Whatever your Idss measurement is(from your first test), then that is going to be about the *lowest* current measurement your going to get(with the gate and source shorted together). For example, if you have one with a Idss of say 11mA, then as you lower the Vgs from a point where both gate and source are the same to something where the gate is seeing less potential than the source, then the current is only going to *increase*._

 

Isn't that *highest*? And current is only going to *decrease*?

 My extensive reading of, ahem, Wikipedia suggests that for a p-channel transistor, as the gate becomes more positive, current progressively decreases.

 *

 In any case, my little rig is having a problem. I can derive 12V just fine from the two 9V batteries, but the Idss measurement doesn't work when I do so. Nothing measures higher than about 5mA.

 I can get measurements just fine with 9V from one battery connected directly to the JFET, and fine with 18V from two batteries, but not with the trimmer in there. I think that the 10k value is restricting the current way too much...... to get the 12V out of the 'middle' of the trimmer, the 'top' resistance is ~3500 ohms. 18V at 3500ohms is - drum roll please - approx 5mA maximum current through the whole circuit.

 I may have to have stern words with somebody over this......


----------



## runeight

You got a 12V zener?


----------



## digger945

The 271 is not a transistor, it is a depletion mode fet. 
 For the P-channel, as the gate voltage increases with respect to the source, the flow of current decreases. 
 Perhaps this will help.




 This is for an N-channel device, so to test the P-channel j271 hook up the positive on one 9v to "-10" on the schematic, and ground to the point where the two 9v's connect, and the negative 9v to where it has "+10" on the schematic. Take the Vgs as noted on the diagram, take the current across the 10k or inline, whichever you prefer. I just built this and used 4x1M for the 5M on the diagram and it works fine. Matter of fact, you can play around with the numbers and do some calculations based on the exStata schematic and probably get this to look pretty close to actual "in amp" conditions.
 I haven't done the math.


----------



## digger945

Sorry, I posted at the same time Alex did.
 Carry on.


----------



## sumo-kun

Just a quick question about power transformers.

 What is the recommended secondary voltage spec for the hybrid? On site, it mentions 240VCT on the scematic but the BOM says to get a 250VCT. I remember a load of discussion a while back in the thread about the Hammond 270xxx and 269xxx and which one works/doesn't work but I can't remember. I seem to recall the 270 was supposedly too low in the current rating but it worked fine in practice and the 269 produced overheat problems, which resulted in the need for a 300V zener string instead of the 291?

 I will probably be getting a transformer locally because the voltage over here is 100V/50Hz. I found a candidate but I just want to make sure its OK. Its a 240VCT 100mA. Over specced in the current department but is the 240V OK? It also has 3 6.3V/2A taps. Is the 2A rating enough to run both heaters off of it?


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_You got a 12V zener?_

 

Unfortunately not, and I just don't trust the 12V supply I have here. I do have 1k and 2k resistors though, to create a fixed voltage divider that can supply enough current at ~12V.

  Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_The 271 is not a transistor, it is a depletion mode fet._

 

Brainfart 
	

	
	
		
		

		
		
	


	




  Quote:


 For the P-channel, as the gate voltage increases with respect to the source, the flow of current decreases. 
 

I'm pretty sure that's what I said! 
	

	
	
		
		

		
		
	


	




  Quote:


 Perhaps this will help. 
 

Ah, where were you six hours ago! In a round-about way, that seems to be exactly what I have done.

  Quote:


 I haven't done the math. 
 

Pretty sure Alex said earlier that 1mA current was the appropriate operating point. That is what I was aiming for anyway......


----------



## digger945

Well to be honest, I was thinking of another project(jfet amp
	

	
	
		
		

		
		
	


	




) so I am thinking along the lines of the current with a 10-ohm resistor in series and 12v. 1mA may very well be on target for your application. 
 Sure enough, with a 271 in the circuit I posted and 387mV Vgs, I get 1.17mA.
 I'm using the Placid with +-12v.

 Touche'. Flatulence flows from this direction as well.


----------



## BoilermakerFan

Quote:


  Originally Posted by *sumo-kun* /img/forum/go_quote.gif 
_Just a quick question about power transformers.

 What is the recommended secondary voltage spec for the hybrid? On site, it mentions 240VCT on the scematic but the BOM says to get a 250VCT. I remember a load of discussion a while back in the thread about the Hammond 270xxx and 269xxx and which one works/doesn't work but I can't remember. I seem to recall the 270 was supposedly too low in the current rating but it worked fine in practice and the 269 produced overheat problems, which resulted in the need for a 300V zener string instead of the 291?

 I will probably be getting a transformer locally because the voltage over here is 100V/50Hz. I found a candidate but I just want to make sure its OK. Its a 240VCT 100mA. Over specced in the current department but is the 240V OK? It also has 3 6.3V/2A taps. Is the 2A rating enough to run both heaters off of it?_

 

You want a 480VCT for 240V from each leg to the center tap. Parallel two 6.3V heater windings and your fine.


----------



## Beefy

Well, I did all of my JFET testing for Idss and Vgs@1mA using the final schematic I posted above...... the little rig worked nicely. My procedure was to put the JFET into a screw terminal, connect the batteries, measure Idss after 30 seconds at Vgs=0, then increase Vgs until Id dropped to 1mA. Repeat measures on an individual JFET were within 1%.

 Of the 25 I bought from Mouser, 16 were Idss <10mA....... not great. Four were between 10 and 12, but not making the 10% criteria. The five remainders were:
 13.65mA, 2.26V
 13.9mA, 2.26V
 14.15mA, 2.42V
 14.4mA, 2.55V
 14.4, 2.58V
 So pretty good for Idss, but Vgs? I really don't know.

 Thankfully, a magical fairy dropped some of their spare J271 in a package for me, and I got an absolutely perfect quad from three of those and one of mine - both Idss and Vgs are within 2%.


----------



## ChrisX

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Well, as it turns out, splitting the panel will only add cost. At this point I will just get both amps and assume that they all will go out._

 

Although I already have some tubes I would be in with a solid state amp in this case. 
	

	
	
		
		

		
		
	


	




 Alex please add me to the list. I will be on a vacation during X-Mas, so I hope it's not too late for payment next week.

 Chris


----------



## runeight

Latest list.


----------



## Beefy

In a stroke of luck, my custom SumR transformer arrived today - I walked into my building just as the postwoman was walking out. It is sitting on a CD for size reference. A touch scuffed on the encapsulation, but who the hell cares? 
	

	
	
		
		

		
		
	


	









 I now have absolutely everything I need to have my amp fully built and cased, except for Stax Jacks (in the mail) and FPE panels (99% designed, pending jacks), so assuming no failures or part oversights, its going to be a productive holiday season!


----------



## fierce_freak

I should get my case today, then I'll have everything I need for my amp except the LDR's for the lightspeed style attenuator I'm going to build for it (I'm just going rca inputs). I do have a stepper I can use in the meantime.

 Biggest problem I have is no headphone cable, lol.


----------



## pabbi1

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_In a stroke of luck, my custom SumR transformer arrived today - I walked into my building just as the postwoman was walking out. It is sitting on a CD for size reference. A touch scuffed on the encapsulation, but who the hell cares? 
	

	
	
		
		

		
			





 I now have absolutely everything I need to have my amp fully built and cased, except for Stax Jacks (in the mail) and FPE panels (99% designed, pending jacks), so assuming no failures or part oversights, its going to be a productive holiday season! 
	

	
	
		
		

		
		
	


	


_

 

Very nice - what was the final cost?


----------



## Beefy

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Very nice - what was the final cost?_

 

Canadian $67 for the transformer, an additional $13 for shipping within Canada, tax, PayPal...... CA$87.36 at my door.

 The proof will be in the pudding when I wire it up to a PSU - should be before the New Year.


----------



## les_garten

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_In a stroke of luck, my custom SumR transformer arrived today - I walked into my building just as the postwoman was walking out. It is sitting on a CD for size reference. A touch scuffed on the encapsulation, but who the hell cares? 
	

	
	
		
		

		
		
	


	






 I now have absolutely everything I need to have my amp fully built and cased, except for Stax Jacks (in the mail) and FPE panels (99% designed, pending jacks), so assuming no failures or part oversights, its going to be a productive holiday season! 
	

	
	
		
		

		
		
	


	


_

 

How are you mounting the STAX jack?


----------



## Beefy

My Stax jacks are coming from luvdunhill. I will screw them in from the back of the front panel with blind threaded holes.

 It adds approx $15 to the FPE work compared to just screw holes through from the front, but I think it will be worth it.


----------



## macm75

Are the pdf images on the "Before You Start" page 1:1 scale?
The eXStatA Electrostatic Amplifier
 Just trying to identify a good box size (given phase 3 is a go (couldn't find a praying smiley)).
 Thanks.


----------



## wiatrob

Yes, these should be 1:1 PDFs


----------



## luvdunhill

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Of the 25 I bought from Mouser, 16 were Idss <10mA....... not great._

 

you kididng? that's great 
	

	
	
		
		

		
		
	


	




 You're just not building the right amp. Sorry for not checking up, looks like digger945 took care of you though


----------



## Beefy

Yep, Idss were all quite low. And digger945 definitely saved my bacon for making a really good JFET quad.

 What is strange though is that all of his recorded Idss were all exactly 15% higher than what I measured. Someone's multimeter is off......


----------



## wiatrob

Here's what might be Sherwood's eXStata Beta (yah, it's just my proto case with the new PS and Hybrid board in it - I put it together so a 'certain individual' can have a listen). 

 Looking into getting a custom finish treatment on the front. Damn inconvenient these holidays.

 Listening to it now. Sounds fantastic. Needs a window so you can see the toobs. OH, there's CCS heatsinks in front of them. Nevermind!


----------



## fierce_freak

Anyone have a matched quad I could grab? I bought 30 with no dice =/


----------



## bidoux

Maybe you can use them even if they don't perfectly match. Post your values and ask someone who knows better than me.


----------



## digger945

Quote:


  Originally Posted by *fierce_freak* /img/forum/go_quote.gif 
_Anyone have a matched quad I could grab? I bought 30 with no dice =/_

 

Pm sent, my good man.


----------



## Keithpgdrb

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Here's what might be Sherwood's eXStata Beta (yah, it's just my proto case with the new PS and Hybrid board in it - I put it together so a 'certain individual' can have a listen). _


----------



## sachu

tested the first of the power supply boards.

 Came up right away.
 T1 and T3 measuring about 340V wrt G.
 Bias voltages are dialed in, 291V zener string. Using a 269JX for the transformer. Have a 369JX as well for the other power supply board and amp.

 Will now bring up the second board.


----------



## sachu

second board, the negative rail failed spectacularly on turn on. The regulator MOSFET burned out..took out R4 and R2 with it. Its possible I didn't have the load connected properly on the negative rail and was probably reading open.

 Already removed all the offending parts, R2, R4,R6, Protection zener, mosfet. Probably will replace Q2 as well while am at it.
 Unfortunately i don't have extra N channel mosfets with me..anyone got a spare? Need to scrounge up a 10R resistor as well..the others i have already replaced.


----------



## Beefy

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_second board, the negative rail failed spectacularly on turn on. The regulator MOSFET burned out..took out R4 and R2 with it. Its possible I didn't have the load connected properly on the negative rail and was probably reading open._

 

OUCH! But it don't think it will be the MOSFETs that burn up if the load isn't connected. It would probably be the shunt transistors; Q7 and 8 on the negative rail.

 Something else might be wrong on that side......


----------



## sachu

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_OUCH! But it don't think it will be the MOSFETs that burn up if the load isn't connected. It would probably be the shunt transistors; Q7 and 8 on the negative rail.

 Something else might be wrong on that side......_

 

hmm..well could it have been the trim pot being turned a bit too high up on turn on? in any case i need to rebuild that section.

 Wondering if it is safe to test the positive rail at least without the negative rail regulator mosfet in the loop.


----------



## runeight

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_hmm..well could it have been the trim pot being turned a bit too high up on turn on? in any case i need to rebuild that section.

 Wondering if it is safe to test the positive rail at least without the negative rail regulator mosfet in the loop._

 

Only if you want to risk more components. 
	

	
	
		
		

		
			





 Beefy is correct. If the NFET was in the right orientation and if its associated zener/bjt were also correct then without a load it will be the shunt devices that have been toasted. Certainly the MJEs, possibly the MPSAs.


----------



## Beefy

Well my power supply is up and checking out A-O-K. No smoke, and no need for CPR 
	

	
	
		
		

		
		
	


	




 Mains 122 VAC
 Transformer unloaded 282 VAC
 Transformer loaded 269 VAC

 T1-T2 ~360 mV
 T3-T4 ~ 410 mV

 T1-GND 340 VDC
 T3-GND 338 VDC

 + rail 308 VDC
 - rail 307.5 VDC

 Q3,4 heatsinks hot but can easily hold my fingers on them
 Q5,6 and 7,8 heatsinks just warm
 Load resistors HOT 
	

	
	
		
		

		
		
	


	




 My measured secondary voltage doesn't seem to make much sense relative to my post-cap voltage..... but I have confirmed it with two different multimeters and get the exact same result, so meh. The custom transformer seems to work perfectly though!


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_You know, the value for R23/R24 was calculated for the nominal filter voltage of around 325-330V. If you have much higher than that then these resistors will get quite a bit hotter than I had expected._

 

IMHO, the default value of R23/R24 has to go up - let alone for those with higher post-cap voltage.

 With 340V post-caps, my resistors are reading in excess of 120C - that is even hotter than the load resistors.. The resistors are not touching the PCB, but the PCB near the resistor legs is still getting much hotter than I am comfortable with.


----------



## runeight

I believe you are right. Would you have time/inclination to try 100k to see if that is a good value for LED brightness vs power dissipation?


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I believe you are right. Would you have time/inclination to try 100k to see if that is a good value for LED brightness vs power dissipation?_

 

It will probably be a long time before I place another Mouser order, but I will definitely grab something when I do.

 *

 Just a bit more of an update with respect to my SumR transformer. The secondary AC voltage and post-cap voltage posted above do drop slightly as the transformer heats up; everything settles at ~335V post-cap after an hour or so. Thus I can definitely recommend a 2x240VAC @ 62.5mA (30VA) toroid as an option for the SS builds.


----------



## fierce_freak

I'm actually very suspicious of my DMM, so I've ordered a new one and will retest IDSS on the J271's. Scott, I'll get ahold of you after I've had a chance with the new meter and send the <10mA ones your way.


----------



## BoilermakerFan

Quote:


  Originally Posted by *fierce_freak* /img/forum/go_quote.gif 
_I'm actually very suspicious of my DMM, so I've ordered a new one and will retest IDSS on the J271's. Scott, I'll get ahold of you after I've had a chance with the new meter and send the <10mA ones your way._

 

Can't speak highly enough of my Amprobe:

 The Amprobe 37XR-A. Made right next to Flukes in the same factory.
Amazon.com: Amprobe 37XR-A True RMS Digital Multimeter: Home Improvement

 Resistance, Impedance, Continuity, Capacitance, and Inductance as well as true RMS voltage...


----------



## runeight

There are still five open slots for SS boards on this next run. Are there any additional new builders who want to have one?


----------



## Keithpgdrb

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_There are still five open slots for SS boards on this next run. Are there any additional new builders who want to have one?_

 

what is the cost of the two boards together? I might just snatch up a sand as well for another build along the line.


----------



## runeight

The cost per set will probably be similar to before, about $25. However, I'd still like to limit the buys to one board set per builder. But, we'll see how this rolls out over the next week or so while we wait for the boards.


----------



## M3NTAL

runeight - please add me to the solid state board list!

 Cheers
 -M3NTAL-


----------



## runeight

Done.


----------



## luvdunhill

If anyone would be willing to match JFETs for the next board run, I have a whole host of devices that are > 10mA Idss that will make your job, much, much easier. I can check the exact numbers, but I'd be willing to trade them for another unmatched batch of parts. If you guys need 10 quads, that should definitely be doable. Any volunteers?


----------



## HeadphoneAddict

I was pretty sure Blutarsky wanted a set of boards, but he is out of town all last week/this week and probably doesn't know about the new sets.


----------



## studeb

After something like a month, i measured and set the PSU again.
 Here i what i have, its a SS amp with two triad transformers:

 Wall 118 VAC
 After T/F 255 VAC
 T1 - Gnd +324 VDC
 T3 - Gnd -318VDC
 T1 - T2 0.360 VDC
 T3 - T4 0.410 VDC
 Output +/- 303VDC

 This is with amp connected.

 Amp offsets were all still under 1 VDC.


----------



## minivan

finish casing my ss amp.
 2x u1 case at $17.5 aud each = $35aud
 mouser parts ~$150 aud
 pcb and transformer ~$150 aud
 powe switch $3 aud
 volume knob and aluminium rubber feet ~$12 aud
 recycled neutrick connector and canare cable from local dj store's bargain bin ~$15 aud
 alps rk27 4 gang pot $50 aud.
 fuse holder $2 aud

 total cost = $417 aud.


----------



## Sathimas

Could somebody give me a list of sources for stax pro jacks?

 @minivan

 Looks nice - I hope to read some sound impressions soon!


----------



## macm75

I realize there have been no complaints regarding the Hammond 269JX or 270AX but just wish to make sure before I order... 
 Does this transformer stay cool for the Hybrid use?
 Thanks, Joe


----------



## BoilermakerFan

Alex

 How many PSU boards are on a full board?

 Maybe you can run an extra PSU board?


----------



## bidoux

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_Could somebody give me a list of sources for stax pro jacks?_

 

I think these work. Maybe you can try emailing Franck Cooter too.


----------



## macm75

Quote:


  Originally Posted by *bidoux* /img/forum/go_quote.gif 
_I think these work. Maybe you can try emailing Franck Cooter too._

 

Same connector but different jacket...
New-Old-Stock Miscellaneous Brand Tube Sockets - Amphenol part number 78-S6S
 Same ones here too...
Cooper Interconnect - 78-S6S - Allied Electronics
 Also you can email Woo Audio. Woo sells the one he puts on his amps.
 BTW, that's FrankCooter. If you don't mind the amphenol type I think I have one or two you can have. I'll PM you later after I verify what I have.


----------



## n_maher

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_Also you can email Woo Audio. Woo sells the one he puts on his amps._

 

Just a point of clarification, no, he doesn't anymore. I spoke with Jack today about this very subject.


----------



## audionut

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_I realize there have been no complaints regarding the Hammond 269JX or 270AX but just wish to make sure before I order... 
 Does this transformer stay cool for the Hybrid use?
 Thanks, Joe_

 

The 270AX gets really hot to the touch in the hybrid, but Alex believes (I think), that it is still ok to use in the Hybrid. Not sure on the 269JX. I used the 270CAX, which has a higher current rating than the 270AX, but is about $20 bucks more at Mouser. It only gets good and warm to the touch, but not too hot to touch (like the AX) does. I also used the 300V zener string instead of the 291V. Not sure if the higher zener string contributes to transformer temp, though. Alex may want to chim in here.


----------



## BoilermakerFan

Can I parallel (3) power LEDs per channel? I need (6) for back lighting on my chassis faceplate.


----------



## Coreyk78

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Just a point of clarification, no, he doesn't anymore. I spoke with Jack today about this very subject._

 

Well then I guess the one I have just became pretty rare, because I just got one from him when I built my amp.


----------



## Emooze

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Can I parallel (3) power LEDs per channel? I need (6) for back lighting on my chassis faceplate._

 

What do you mean per channel? If you're using the provided points on the PS board, there's less than 5mA available so you'd have to get some really efficient LED's or change the resistors.


----------



## HeadphoneAddict

So, while wiatrob preps my amp case and Sherwood's case, this past weekend I borrowed his prototype case with the new tube boards and PSU installed. So, it has the same front/rear panels and attenuator as at RMAF in October, but new guts. I plugged it into my Apogee mini-DAC XLR with a pair of ALO SXC 18g IC, and a halfway decent tributaries power cable, feeding it from a Samsung DVD player via Synergistic Research Coax cable - and *the sound is out of this world* with my HE60 and O2 Mk1.

 The sound is rich and full and immersive, very fast and detailed, imaging is very precise, and timbre and tone is spot on. Soundstage is much better balanced, and at RMAF it was much bigger than with my old GES. But at RMAF the GES had much better timbre and tone and frequency response. This is now clearly better than the prototype at RMAF 3 months ago, and I don't know if the difference is better synergy with the Apogee than with the PS Audio DAC, or the design changes, or both. The eXStatA at RMAF was clearly better with wiatrob's OPUS DAC than with my stock PS Audio DLIII, but I don't remember it being this detailed and spacious as it is with the Apogee. The one at RMAF was also the sand version, not the tube version.

 Anyways - if this was a production amp it could command $1500, possibly even $2000 per unit. I was stunned as I was comparing it to my WES and figuring that the eXStatA could fit right between my GES and WES in sound quality and performance. I can think of no higher praise than this -> if the eXStatA was my only electrostatic amplifier, I could live happily with it and not be thinking about upgrading (for a while). The WES is still more euphonic with a more refined texture, a little more engaging in the mids, with a little less edge to the treble, but it's hard to believe you have to spend 10x as much for those small refinements.

 There is NO WAY we can let this die out and not see more being built for many years to come. *If there aren't more boards made after this next run and this is goes away, 5 years from now people will be selling these for the price of an HE60 and wondering why they aren't made anymore.* It would be just as bad as no more R10, HP-1000 and PS-1, or L3000 and K1000. There will always be a demand for an amp like this, just as there is for the vintage discontinued phones.

 ALEX, I don't care what the other naysayers and fanboys of other amp designs say, but we need to throw you a party and ship you another round of free headphones for designing this amp and seeing it through this far! Bravo! (I was so excited I had to call Bill 3 times to tell him how it sounded)

 PS: I've had a few PM with questions and want to clarify a couple of things. The GES is a great amp, and it pairs well with many kinds of Lambdas, SR-003, SR-5 gold, SR-80, Gamma Pro, ESP-950, Jade, HE60 and more - except for the O2 Mk1 or Mk2 where it could use more power to achieve live music volumes (not sure about HE90). The eXStatA has that extra power and opens up the soundstage a bit more as a balanced amp vs the SE GES. But that isn't to say the GES soundstage is too small, just the balanced eXStatA soundstage was larger. In comparing the eXStatA single ended to the WES the eXStatA soundstage is definitely smaller and probably closer to what I was hearing with the GES. I don't know if the difference is supposed to be that big between SE and balanced, but that's what I hear. I don't have a GES to compare to anymore, since I sold it after RMAF to buy the WES, so it's hard for me to answer more questions about the comparison except what I heard at RMAF, where the GES timbre and tone was superior, but the eXStatA soundstage and power was better. The extra power doesn't seem to be required with my other stats except for the O2, and I'm not listening to the eXStatA now with the volume past 1 o'clock.


----------



## sachu

Larry try to listen to the ESP950 on that eXStatA if you can borrow one.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_So true Larry...I've been calling for the latter for a while now.. should we start a thread then? I have had a couple or so PMs from folk who are willing to be on board. AM sure that would gro wto a sizeable number of folk once we have the thread going.

 edit:

 Larry try to listen to the ESP950 on that eXStatA if you can borrow one. 
	

	
	
		
		

		
		
	


	


_

 

That sounds good to me.

 Also, I think that Bill recently bought my old APS modded re-cabled ESP-950 from the guy that bought them from Blutarsky (I traded them for a PS Audio DLIII DAC), so I will be able to try them on the eXStatA at some point.

 I did also try the SR-Lambda (normal bias) on the eXStatA, and via single ended input they still sounded a little etched with a smiley face curve, but with balanced input they filled out and sounded even better. So, that is a good match too. I need to get new silicone tips for my SR-003 to try them, and I'll also be trying my Jade and my SR-5 Gold Edition (normal bias) with the eXStatA soon.


----------



## wiatrob

Yup, it's true, after a Hawaiian vacation, they are coming back to Colorado to roost. I wanted something similar to the unavailable and unaffordable (by me) HE-60s sound.


----------



## wiatrob

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_(I was so excited I had to call Bill 3 times to tell him how it sounded)_

 

Indeed! And thanks for not letting the entire DIY world know I forgot to bolt down the PS to the standofs, and it came loose and nearly electrocuted you! 
	

	
	
		
		

		
		
	


	




 Thought you'd like to hear it. Just to tide you over...


----------



## ChrisX

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Can I parallel (3) power LEDs per channel? I need (6) for back lighting on my chassis faceplate._

 

I would suggest connecting the LEDs in series, not in parallel. With the voltage available you can easily drive 100 of them.


----------



## BoilermakerFan

Quote:


  Originally Posted by *ChrisX* /img/forum/go_quote.gif 
_I would suggest connecting the LEDs in series, not in parallel. With the voltage available you can easily drive 100 of them._

 

Thanks. I should have said series, not parallel, or rather just use (3) per side. That is the most I'll need, it may only be two per side...


----------



## pabbi1

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Bravo! (I was so excited I had to call Bill 3 times to tell him how it sounded)_

 

Excited enough to post in the impressions thread? 
	

	
	
		
		

		
		
	


	




 The enduring problem we (all) have is that electrostats are such a small % of the population, they are obscured by the noise to signal ratio - but getting more attention to a really good design might help getting more signal - then, in turn, getting more actually heard. 

 This is crucial to getting better signal.

 Not sure we can repay our debt to runeight - except enjoying the gift he has given.

 Now, where are the other builders, and, impressions? Please, PLEASE put them in the impressions thread.


----------



## runeight

Current status. Need 4 more SS board builders.


----------



## digger945

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_The cost per set will probably be similar to before, about $25. However, I'd still like to limit the buys to one board set per builder. But, we'll see how this rolls out over the next week or so while we wait for the boards._

 

 Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Current status. Need 4 more SS board builders. 
	

	
	
		
		

		
		
	


	


_

 

Count me in for 1 set Alex. I can pay for 2 sets if you need to push the order through, then sell 1 set to a future builder, if it would help. If I should get some more 271's then I could also provide matched quads, or trade for sub-10mA parts like luvdunhill suggested before. People can check with Marc and I'm sure he will fix them up also.


----------



## bidoux

Nevermind, I really missed something...


----------



## luvdunhill

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_trade for sub-10mA parts like luvdunhill suggested before. People can check with Marc and I'm sure he will fix them up also._

 

Team-Extreme-JFET-Matching could consolidate all >10mA Idss parts into a single group that would probably be easiest. Unfortunately, I cannot really volunteer for the task of matching at the moment, but I'm happy to send them on.


----------



## runeight

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Count me in for 1 set Alex. I can pay for 2 sets if you need to push the order through, then sell 1 set to a future builder, if it would help. If I should get some more 271's then I could also provide matched quads, or trade for sub-10mA parts like luvdunhill suggested before. People can check with Marc and I'm sure he will fix them up also._

 

OK. On the list. 
	

	
	
		
		

		
		
	


	




 I'm expecting boards next week, probably late. When I get them I will ask you all for you shipping addresses. I can get them all out before things get intense.


----------



## digger945

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Team-Extreme-JFET-Matching could consolidate all >10mA Idss parts into a single group that would probably be easiest. Unfortunately, I cannot really volunteer for the task of matching at the moment, but I'm happy to send them on._

 

Yea, I didn't mean to volunteer you for the matching job there. 
 I don't mind doing matching for folks, but I'm actually low on parts at the moment. I just sold my last perfectly matched quad, and don't have anything coming in right now.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Excited enough to post in the impressions thread? 
	

	
	
		
		

		
		
	


	




 The enduring problem we (all) have is that electrostats are such a small % of the population, they are obscured by the noise to signal ratio - but getting more attention to a really good design might help getting more signal - then, in turn, getting more actually heard. 

 This is crucial to getting better signal.

 Not sure we can repay our debt to runeight - except enjoying the gift he has given.

 Now, where are the other builders, and, impressions? Please, PLEASE put them in the impressions thread._

 

I didn't know about the impressions thread so I posted them here. I'll go there and post it as well.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Excited enough to post in the impressions thread? 
	

	
	
		
		

		
		
	


	




 The enduring problem we (all) have is that electrostats are such a small % of the population, they are obscured by the noise to signal ratio - but getting more attention to a really good design might help getting more signal - then, in turn, getting more actually heard. 

 This is crucial to getting better signal.

 Not sure we can repay our debt to runeight - except enjoying the gift he has given.

 Now, where are the other builders, and, impressions? Please, PLEASE put them in the impressions thread._

 

I'm still gathering parts and waiting for my E-P iron for both amps. 

 I'm being very methodical and particular. I'm putting a lot of effort into the cases for both amps. I'm not going to rush the builds, but they are moving forward. As soon as the amps are done, I'll definitely post up my pics and impressions.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Indeed! And thanks for not letting the entire DIY world know I forgot to bolt down the PS to the standofs, and it came loose and nearly electrocuted you! 
	

	
	
		
		

		
			





 Thought you'd like to hear it. Just to tide you over...
	

	
	
		
		

		
		
	


	


_

 

Well, I didn't want to make you look bad, so I kept my mouth shut. 
	

	
	
		
		

		
		
	


	




 Fortunately you didn't send 600v through the case, and I was not in any danger. But when the headphones get no bias because the PS is floating around inside and ripping out wires, then there is no sound. 
	

	
	
		
		

		
		
	


	




 I'm just glad I was able to figure out which wires go where, after you wouldn't pick up your phone. 
	

	
	
		
		

		
		
	


	




 -----

 While we're being so open and honest - I do find the amp doesn't sound nearly as good single ended as it does balanced (regardless of the switches in the rear), and in SE mode the right channel is slightly louder than the left, while in balanced mode they are perfectly matched. This may have happened when the PS came lose, I don't know.


----------



## cyanoacry

Hi runeight,

 I'd like to grab a set of SS boards. Could you add me to the list?

 Thanks!
 cyanoacry


----------



## Sathimas

I am currently looking for a fitting transformer.

 Since I'm living in Germany and have 220V coming from the "wall" the 269JX doesn't work here.
 I'd need the 369AX - which costs about twice as much (85$).

 Although I've been following this thread I don't remember somebody mentioning more alternatives for the hybrid?
 Could I simply use two transformers - one with 250V and one with 6,3V for the heaters?


----------



## macm75

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_Could I simply use two transformers - one with 250V and one with 6,3V for the heaters?_

 

You mean one 500VCT or two identical 250V. That and a 6.3V@>3A would be fine.
 Be sure to check your German ebay, old radio shops, or custom transformer buiders too. Matter of fact, I would stay very clear of the Hammond given the report they get hot with the hybrid amp.


----------



## acmemr

Quote:


  Originally Posted by *cyanoacry* /img/forum/go_quote.gif 
_Hi runeight,

 I'd like to grab a set of SS boards. Could you add me to the list?

 Thanks!
 cyanoacry_

 

I would only say: Me too.


----------



## runeight

Quote:


  Originally Posted by *cyanoacry* /img/forum/go_quote.gif 
_Hi runeight,

 I'd like to grab a set of SS boards. Could you add me to the list?

 Thanks!
 cyanoacry_

 

On the list. 
	

	
	
		
		

		
		
	


	




 There are two SS boards remaining.


----------



## runeight

Quote:


  Originally Posted by *acmemr* /img/forum/go_quote.gif 
_I would only say: Me too. 
	

	
	
		
		

		
		
	


	


_

 

acmemr, I missed your post, so you're on the list now too.

 That leaves one SS board unspoken for.


----------



## WilCox

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_acmemr, I missed your post, so you're on the list now too.

 That leaves one SS board unspoken for._

 

I'll take the last SS board set! Let me know where to forward the payment.


----------



## runeight

OK, that makes 10 of each spoken for.

 List is attached and let me know if any of you change your minds.


----------



## runeight

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_I am currently looking for a fitting transformer.

 Since I'm living in Germany and have 220V coming from the "wall" the 269JX doesn't work here.
 I'd need the 369AX - which costs about twice as much (85$).

 Although I've been following this thread I don't remember somebody mentioning more alternatives for the hybrid?
 Could I simply use two transformers - one with 250V and one with 6,3V for the heaters?_

 

Yes, as macm75 points out, you can use two 250V transformers in series to make one 250-0-250 transformer and then a separate 6.3V heater transformer.

 There is information on the website about using the HV Triad transformers in series for just his purpose. Although the triads haven't had much discussion, they work perfectly alright and can be wired for 220V line.


----------



## spritzer

Most of the eBay R-core transformers can also be configured for either 117V or 230V.


----------



## fierce_freak

If anyone does some matching I'd like to grab a closely matched quad. If no one else is going to do some matching, I'll volunteer.


----------



## cat6man

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_OK, that makes 10 of each spoken for.

 List is attached and let me know if any of you change your minds. 
	

	
	
		
		

		
		
	


	


_

 

hi there,

 i'm interested in a tube version.........guess i'm on a waiting list if anyone changes their mind

 i have a stax lambda pro with an srm-t1s driver........driver input is xlr output of wadia 27ix fed aes/ubu by tact rcs2.0s digital room correction unit in feedthrough mode (no room equalization) but set to upscale to 96khz.........for some crazy synergy, the wadia sings with 96khz input over aes/ebu, all other inputs collapse the soundstage (even 96khz over spdif!)........it was like a new DAC when i found the aes/ebu/96khz setting.......and i'd love to know why 
	

	
	
		
		

		
		
	


	




 been listening to stax since i first got a pair of old ones in college long long ago............this unit sounds very exciting...............have to blame my first ever canjam in NJ this year for getting me back on the headphone upgrade trail...........i was positive going in that that would not happen 
	

	
	
		
		

		
		
	


	




 happy new year everyone


----------



## cat6man

followup: just discovered this 100+ page thread...........are there any key posts that summarize project?


----------



## runeight

go to Cavalli Audio


----------



## cat6man

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_go to Cavalli Audio_

 

thanks!
 this looks very interesting


----------



## luvdunhill

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Yea, I didn't mean to volunteer you for the matching job there. 
 I don't mind doing matching for folks, but I'm actually low on parts at the moment. I just sold my last perfectly matched quad, and don't have anything coming in right now._

 

I'll plan on sending you the >10 Idss parts then


----------



## srserl

Is anyone taking an eXStata to the norcal meet 2/27? If not, I will try, but it will be cutting it close to get all the parts and finish in time.


----------



## pabbi1

n/m


----------



## wiatrob

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_
 While we're being so open and honest - I do find the amp doesn't sound nearly as good single ended as it does balanced (regardless of the switches in the rear), and in SE mode the right channel is slightly louder than the left, while in balanced mode they are perfectly matched. This may have happened when the PS came lose, I don't know._

 

Well, I don't remember this symptom at RMAF, but we really weren't listening SE. And I pretty much never do. You do have those RK's in there.

 We'll see how the next builds sound SE vs. XLR. 

 Anybody out there with a build that accepts both? Notice any wide variance in SQ between input types?


----------



## spritzer

Uneven channels in SE mode points to gain issues as the high gain of the amp acts as the phase splitter. We had the same issue in the ES-1 when using low mu tubes.


----------



## Sathimas

I just got an offer for a custom built transformer from a german company - ~18€ instead of 60€.

 Since the hammond transformer seems to be a little "small" - what values should be higher in the custom built one?
 Maybe 50VA for some reserve?

 I also just ordered some tubes from ebay.

LOT OF 2-6S4A NOS - eBay (item 260521600635 end time Jan-09-10 11:11:32 PST)

 You can simply ask the seller and he'll send you an offer.
 I paid 15$ for 8 tubes - 4GE and 4Sylvania + 8$ shipping to Germany


----------



## Beefy

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_Since the hammond transformer seems to be a little "small"_

 

I don't get that impression at all.

  Quote:


 what values should be higher in the custom built one?
 Maybe 50VA for some reserve? 
 

I am powering a loaded PSU with a 2x240V 30VA transformer with no issues. If it was a bigger, less loaded transformer then the excess voltage burned by the PSU would be too high.


----------



## Sathimas

Ok, I just got the impression because somebody said that the hammond does get very hot.

 If the specs are fine I'll just leave them as they are.


----------



## Beefy

Personally, I'd much rather the transformer get hot than the PSU......


----------



## nattonrice

Since I was taking photo's of some cables I received I also snapped two pics of Marc's Stax Jack.
 I figure this is the most relevant place to post this with more and more people building a stat amp... 
	

	
	
		
		

		
		
	


	



 Machined Teflon is pure win.

 pabbi1 (I think) also posted some pics a good century ago~


----------



## Beefy

Nice to see pics - I'm still waiting for mine thanks to stupid Canada Post 
	

	
	
		
		

		
		
	


	




 I'm curious as to the best way to attach wires to those pins


----------



## jigster

Quote:


  Originally Posted by *nattonrice* /img/forum/go_quote.gif 
_Since I was taking photo's of some cables I received I also snapped two pics of Marc's Stax Jack.
 I figure this is the most relevant place to post this with more and more people building a stat amp... 
	

	
	
		
		

		
		
	


	



 Machined Teflon is pure win.

 pabbi1 (I think) also posted some pics a good century ago~
_

 

Wow, that's absolutely gorgeous! Where do I find one?


----------



## nattonrice

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Nice to see pics - I'm still waiting for mine thanks to stupid Canada Post 
	

	
	
		
		

		
		
	


	




 I'm curious as to the best way to attach wires to those pins 
	

	
	
		
		

		
		
	


	


_

 

Seems Canada post has lots of problems 
	

	
	
		
		

		
		
	


	



 Auspost surprised me by getting it to me so quick~

 I reckon the same way as the Connex tube sockets; a little semi-loop of wire and then solder.
 Perhaps others have a better idea?


----------



## HeadphoneAddict

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Well, I don't remember this symptom at RMAF, but we really weren't listening SE. And I pretty much never do. You do have those RK's in there.

 We'll see how the next builds sound SE vs. XLR. 

 Anybody out there with a build that accepts both? Notice any wide variance in SQ between input types?_

 

 Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_Uneven channels in SE mode points to gain issues as the high gain of the amp acts as the phase splitter. We had the same issue in the ES-1 when using low mu tubes._

 

Wiatrob is going to check and make sure there was nothing damaged when the PS board can loose and shorted against the case.


----------



## pabbi1

Quote:


  Originally Posted by *nattonrice* /img/forum/go_quote.gif 
_Seems Canada post has lots of problems 
	

	
	
		
		

		
			




 Auspost surprised me by getting it to me so quick~_

 

Hates me some Canada Post - it is a lifetime acheivement regarding my 'service' from them. Possibly the worst in the world.

  Quote:


  Originally Posted by *nattonrice* /img/forum/go_quote.gif 
_ I reckon the same way as the Connex tube sockets; a little semi-loop of wire and then solder. Perhaps others have a better idea?_

 

In the 2 I have used. I literally just soldered the straight wire to the pin, and then covered with heatshrink. The loop idea makes full heatshrink not as easy, when using 22awg wire. But, this is, by far, the best Stax connector - ever. Thanks Marc - it really completes the project - one worthy of a connector of this calibre.

 To attach the barrel to the screw-block, I just used 'super glue', which has not failed to date, probably never will due to the tight machining of the teflon. 

 Pure(st) win.


----------



## cat6man

good news:
 well, it took a couple of days and i've gone through the entire thread 
	

	
	
		
		

		
		
	


	




 bad news:
 i now see that the beta2 hybrid boards are all taken and i missed out (just recently found this thread) by about a week 
	

	
	
		
		

		
		
	


	




 guess i'll keep track of the thread going forward and see if anyone drops out or if a 3rd order of boards

 cheers and happy new year everyone


----------



## luvdunhill

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Hates me some Canada Post_

 

geez, that sucks Beefy. I've mailed a few to Australia *after* yours and they've already arrived.

 I've used solid core wire and wrapped it around the pins and then applied bit of solder. You can even remove the pins if that helps. Stranded wire is possible, but you'll have to just strip a bit and place it parallel to the pin and find a way to solder it.


----------



## Beefy

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_geez, that sucks Beefy. I've mailed a few to Australia *after* yours and they've already arrived._

 

And I always used to complain about shipping to Australia...... the ironing is delicious 
	

	
	
		
		

		
		
	


	




  Quote:


 You can even remove the pins if that helps 
 

...... that might be essential for the centre pin of the normal bias jacks.


----------



## HeadphoneAddict

I've had a few PM with questions (about GES, WES and eXStatA comparisons) and want to clarify a couple of things. The GES is a great amp, and it pairs well with many kinds of Lambdas, SR-003, SR-5 gold, SR-80, Gamma Pro, ESP-950, Jade, HE60 and more - except for the O2 Mk1 or Mk2 where it could use more power to achieve live music volumes (not sure about HE90). The eXStatA and WES have that extra power and opens up the soundstage a bit more as a balanced amp vs the single ended GES. 

 But that isn't to say the GES soundstage is too small, just that the balanced amps soundstages were larger. In comparing the eXStatA single ended to the WES the eXStatA soundstage is definitely smaller and probably closer to what I was hearing with the GES. I don't know if the difference is supposed to be that big between SE and balanced, but that's what I hear. I don't have a GES to compare to anymore, since I sold it after RMAF to buy the WES, so it's hard for me to answer more questions about the comparison except what I heard at RMAF, where the GES timbre and tone was superior and similar to the WES that was there, but the eXStatA soundstage and power was better. The extra power doesn't seem to be required with my other stats except for the O2 which demand it.

 I hope that helps.


----------



## macm75

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Personally, I'd much rather the transformer get hot than the PSU...... 
	

	
	
		
		

		
		
	


	


_

 

But wouldn't you want neither to be hot? 
 I'm sure Sathimas would have no intention of upping the delivered voltage - having more current capability is a good thing.


----------



## Beefy

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_But wouldn't you want neither to be hot? 
 I'm sure Sathimas would have no intention of upping the delivered voltage - having more current capability is a good thing._

 

But if you're not using the current, the transformer isn't fully loaded, and the voltage goes up whether you want it to or not.


----------



## runeight

Yes, this is right. 
	

	
	
		
		

		
		
	


	




 This amp does not benefit from transformers that are over spec'd, especially ones that can supply more current than it needs. You may ask why? 
	

	
	
		
		

		
		
	


	




 Since the amps are diff amps, if all the components were perfect, the amps would draw no dynamic current from the PS. Components are not perfect, but still the dynamic current draw will be very small. Hence, the amp does not need any current reserve in the PS and so it doesn't need any current reserve in the transformer.

 Furthermore, the load is 100pf or thereabouts. Only microamps are being pushed through the headphones.

 This is why we can use a shunt regulator where the shunt currents are not very large so that the power dissipation in the shunt devices is fairly small given the shunt voltage of >300V.

 It is best to use a transformer that keeps the first filter cap voltage in the range of 320-350VDC, keeping the power dissipation in the PS devices within reasonable limits.

 In this case bigger is not better and this amp was specifically designed to work without exotic transformers.


----------



## macm75

So I hear the 2 Triad VPS230-110's works nice and cool with the Hybrid. With 2 you would essentially have a 460VCT transformer with current capability of what? Would that be 110mA or 220mA given you have 2? Thanks.

VPS230-110 Triad Magnetics Transformers

 Edit: So I, like Sathimas, am trying to find a transformer that runs cool and within spec for this amp. So after reading Alex above, I wonder if the "issue" with the 270AX is the heater winding. But like you guys said, a higher current rating will provide more voltage but nothing a resistor cannot fix.


----------



## runeight

Since the Triads go in series they will be 100mA. Much more than is needed. However, they have bad regulation so I think they will pull down considerably.

 Yes, I think you're right about the 270ax. It is the heater current at the max that causes the transformer to cook. All I can say in response is that I have been running a 270ax drawing 2.8A heater and 50mA HV in my Bijou for a couple of years now. It still works and is not leaking any goo.


----------



## spritzer

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Wiatrob is going to check and make sure there was nothing damaged when the PS board can loose and shorted against the case._

 

Odds are the PSU is fine as they either work or blow up in a rather impressive fashion. I'd say your amp has gain issues, either from badly matched transistors or the design simply doesn't give enough gain to act as a phase splitter. That's why the WES is fitted with a phase splitting circuit for the SE inputs.


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Since the amps are diff amps, if all the components were perfect, the amps would draw no dynamic current from the PS. Components are not perfect, but still the dynamic current draw will be very small._

 

Just a quick question on non-perfect devices...... aside from matching the JFETs and using 1% resistors, is there anything else you can suggest that we can do to reduce dynamic current draw or otherwise improve the amp's performance?

 For example, I matched the BC550 transistors. I bought 25 (first price break), and managed to make made 3 matched quads (HFE within 10). A quad was used for both channels at Q9/10, Q6/7 and Q5/8. I also tested the KSA1156 for Q3,4. Of the six I bought five tested almost identically, one was notably lower and thus not used.

 So was this a worthwhile exercise, or just a waste of time and money?


----------



## runeight

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_Odds are the PSU is fine as they either work or blow up in a rather impressive fashion. I'd say your amp has gain issues, either from badly matched transistors or the design simply doesn't give enough gain to act as a phase splitter. That's why the WES is fitted with a phase splitting circuit for the SE inputs._

 

I don't really know what this means. The amp is a differential amp and it ALWAYS acts like a phase splitter. The only issue between SE and balanced is whether or not the two phases have the same amplitude and in this case they should be pretty close, not perfect, but close for either condition.

 Now if the input fets are badly matched then the amplitudes of the phases will be different. The only way I know to escape this is to either match very carefully for almost every component or apply much more NFB. And large NFB has its own issues, including introducing instabilities that have to be covered with compensation capacitors which this amp doesn't need, but many other stat amps almost certainly do.

 Using an additional phase splitter at the input is not a bad idea at all, but it simply adds more active components to the chain with whatever those components do to the signal. And it just preceeds one phase splitter with another phase splitter, two in a row.

 Now, to get the same volume level from SE you have to drive the single input to twice the excursion while the other input stays grounded. MHO is that there is an effect from this, but I don't know how much it is reflected in the SQ.


----------



## runeight

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Just a quick question on non-perfect devices...... aside from matching the JFETs and using 1% resistors, is there anything else you can suggest that we can do to reduce dynamic current draw or otherwise improve the amp's performance?

 For example, I matched the BC550 transistors. I bought 25 (first price break), and managed to make made 3 matched quads (HFE within 10). A quad was used for both channels at Q9/10, Q6/7 and Q5/8. I also tested the KSA1156 for Q3,4. Of the six I bought five tested almost identically, one was notably lower and thus not used.

 So was this a worthwhile exercise, or just a waste of time and money?_

 

It doesn't hurt to do any of this as it will tend to minimize the differences in gain for the current mirrors. At some point I'm sure there are diminishing returns for the SQ, I just don't know where and probably won't configure a dozen of these amps with different matches to listen for it. 
	

	
	
		
		

		
		
	


	




 I don't think there is need to worry about the dynamic current draw. It will be small and the PS will regulate to extent it was designed to do that.


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I don't think there is need to worry about the dynamic current draw. It will be small and the PS will regulate to extent it was designed to do that._

 

Oh, I'm not concerned 
	

	
	
		
		

		
		
	


	



 What I was hoping to do was measure actual static and dynamic current draw, and set the CCS current as low as possible for my specific scenario.


----------



## runeight

MHO is that you shoudn't try to minimize the CCS current too much. Give the PS some headroom to deal with changes that may occur over time. Besides, the current settings are really bare bones, putting on a couple of mA into the main shunt devices for typical operating conditions. Less than this and the regulator will start to starve the primary shunt devices.

 But, of course, no reason not to play around to see what you get. It is at least half the fun.


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_It doesn't hurt to do any of this as it will tend to minimize the differences in gain for the current mirrors. At some point I'm sure there are diminishing returns for the SQ, I just don't know where and probably won't configure a dozen of these amps with different matches to listen for it. 
	

	
	
		
		

		
		
	


	


_

 

Send the dozen boards to me Alex, I'll listen to them for you...


----------



## HeadphoneAddict

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I don't really know what this means. The amp is a differential amp and it ALWAYS acts like a phase splitter. The only issue between SE and balanced is whether or not the two phases have the same amplitude and in this case they should be pretty close, not perfect, but close for either condition.

 Now if the input fets are badly matched then the amplitudes of the phases will be different. The only way I know to escape this is to either match very carefully for almost every component or apply much more NFB. And large NFB has its own issues, including introducing instabilities that have to be covered with compensation capacitors which this amp doesn't need, but many other stat amps almost certainly do.

 Using an additional phase splitter at the input is not a bad idea at all, but it simply adds more active components to the chain with whatever those components do to the signal. And it just preceeds one phase splitter with another phase splitter, two in a row.

 Now, to get the same volume level from SE you have to drive the single input to twice the excursion while the other input stays grounded. MHO is that there is an effect from this, but I don't know how much it is reflected in the SQ._

 

This particular eXStatA is using one alps attenuator per channel (2 knobs), and with XLR input the two volume knob positions match perfectly - if both are set at 12 o'clock then the channels are perfectly balanced with the o2, HE60 or Lambda. 

 If I switch to RCA the left channel is slightly quieter, the mids are less full sounding, the treble is slightly brighter, the soundstage is smaller, and I have to turn the volume pot for the left channel up about 15-30 minutes higher on the clock to balance the two channels. 

 But, with XLR input I can find few flaws with the sound and it's at least as good as Dinan's modded SRM-717 or better. I PM'd him to see if he'd like to come down with his amp to compare sometime.


----------



## bidoux

I know it is a dumb question, but did you check your source ?


----------



## HeadphoneAddict

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I don't really know what this means. The amp is a differential amp and it ALWAYS acts like a phase splitter. The only issue between SE and balanced is whether or not the two phases have the same amplitude and in this case they should be pretty close, not perfect, but close for either condition.

 Now if the input fets are badly matched then the amplitudes of the phases will be different. The only way I know to escape this is to either match very carefully for almost every component or apply much more NFB. And large NFB has its own issues, including introducing instabilities that have to be covered with compensation capacitors which this amp doesn't need, but many other stat amps almost certainly do.

 Using an additional phase splitter at the input is not a bad idea at all, but it simply adds more active components to the chain with whatever those components do to the signal. And it just preceeds one phase splitter with another phase splitter, two in a row.

 Now, to get the same volume level from SE you have to drive the single input to twice the excursion while the other input stays grounded. MHO is that there is an effect from this, but I don't know how much it is reflected in the SQ._

 

 Quote:


  Originally Posted by *bidoux* /img/forum/go_quote.gif 
_I know it is a dumb question, but did you check your source ?_

 

Yes, it's the same Apogee mini-DAC single ended connection that I use with my ZDT, which doesn't have the issue. I simply unplugged my ZDT and WES from the source's SE and XLR and tried each with the eXStatA. 

 Although... I haven't listened to the ZDT since. I'd better go check and make sure the mini-RCA ALO SXC IC isn't coming loose out of the back of the Apogee after I unplugged it from the ZDT...


----------



## runeight

Boards are shipping today. Should be here by Thu. Time for you guys to start sending me your shipping addresses. Instead of PMs, please email me directly at:

 alex at cavalliaudio dot com

 I will give you your totals once the packages are in the mail along with my paypal email.

 I've attached the list so you can remember who you are.


----------



## wiatrob

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_Odds are the PSU is fine as they either work or blow up in a rather impressive fashion. I'd say your amp has gain issues, either from badly matched transistors or the design simply doesn't give enough gain to act as a phase splitter. That's why the WES is fitted with a phase splitting circuit for the SE inputs._

 

Unless the power supply crashed into one of the SE terminals, and fubared a solder joint. Unlikely, I know...

 The input devices are matched within 5%. Probably tighter. As for the design, I can't speak for EricJ and Runeight, but I believe that, unlike the ~$5000 WES, the original plan was for the amp to be run with fully differential inputs only, so dedicated phase-splitting would have been out of the scope of the amp's design requirements.


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_
 But, of course, no reason not to play around to see what you get. It is at least half the fun. 
	

	
	
		
		

		
		
	


	


_

 


 Or you could just replace each CCS with a BIG resistor!


----------



## wiatrob

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_But, with XLR input I can find few flaws with the sound and it's at least as good as Dinan's modded SRM-717 or better. I PM'd him to see if he'd like to come down with his amp to compare sometime._

 


 Larry, would you like me to take a look at the amp, or swap it with another hybrid while I finish yours? Then we can see if it's wiring, or I fubar'd the input device match (although there haven't been any other complaints about devices I matched).

 Here's something to try if you'd like:

 Use one of the shorting RCA -> XLR adapters (not the trafos) into the XLRs and see if you have the same issue as the RCAs. If you do, a device is suspect, if not, I bet there's an issue with the switch or wiring... As I only matched 25 sets, it MIGHT have happened!


----------



## luvdunhill

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_If you do, a device is suspect, if not, I bet there's an issue with the switch or wiring... As I only matched 25 sets, it MIGHT have happened! 
	

	
	
		
		

		
		
	


	


_

 

Perhaps also invert the phase and compare... so, try with pin 2 hot and pin 3 ground and then compare with pin 3 hot and pin 2 ground.


----------



## wiatrob

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Perhaps also invert the phase and compare... so, try with pin 2 hot and pin 3 ground and then compare with pin 3 hot and pin 2 ground._

 


 Thanks Marc, good tip...


----------



## HeadphoneAddict

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Larry, would you like me to take a look at the amp, or swap it with another hybrid while I finish yours? Then we can see if it's wiring, or I fubar'd the input device match (although there haven't been any other complaints about devices I matched).

 Here's something to try if you'd like:

 Use one of the shorting RCA -> XLR adapters (not the trafos) into the XLRs and see if you have the same issue as the RCAs. If you do, a device is suspect, if not, I bet there's an issue with the switch or wiring... As I only matched 25 sets, it MIGHT have happened! 
	

	
	
		
		

		
		
	


	


_

 

I will try my neutrik XLR > RCA female jack thingamabobs (not the Jensens Transformers) to feed SE into the XLR later tonight, and see what happens. I don't have an easy way to invert the phase (see below), unless I desolder the RCA jacks and switch the wires or take an RCA IC and cut it (I hate ruining cables). Wait a sec, do the RCA cables just screw into the boards, or are they connected to the XLR jacks (I think it is the later)? I suspect the internal cables got mucked up when the old boards were swapped for the new ones.

 I could return this loaner amp when I pick up that other stuff from you, and I am happy to wait for mine and won't need another loaner. I've heard enough to know it will be fantastic as my bedroom balanced amp.


----------



## luvdunhill

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_I don't have an easy way to invert the phase (see below), unless I desolder the RCA jacks and switch the wires or take an RCA IC and cut it (I hate ruining cables)_

 

you could do it at the amp boards. Easy as pie.


----------



## wiatrob

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_you could do it at the amp boards. Easy as pie._

 


 I think he's been exposed to enough HV with my power supply gaff. Stay out of the case, please!


----------



## wiatrob

Quick question for the Beta group; Has anyone implemented the RCA/XLR switch via 4PDT:

The eXStatA Electrostatic Amplifier


----------



## spritzer

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_The input devices are matched within 5%. Probably tighter. As for the design, I can't speak for EricJ and Runeight, but I believe that, unlike the ~$5000 WES, the original plan was for the amp to be run with fully differential inputs only, so dedicated phase-splitting would have been out of the scope of the amp's design requirements._

 

The goal here was to build a budget amp and limiting it to XLR sources only would have been utter nonsense and I know for a fact that this isn't the case. Besides, you can build a basic differential tube amp for 200$ that will handle the SE input just fine. 

  Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Quick question for the Beta group; Has anyone implemented the RCA/XLR switch via 4PDT:

The eXStatA Electrostatic Amplifier_

 

That's pretty much how I wired it up on my KGSS and it works perfectly in SE mode.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Larry, would you like me to take a look at the amp, or swap it with another hybrid while I finish yours? Then we can see if it's wiring, or I fubar'd the input device match (although there haven't been any other complaints about devices I matched).

 Here's something to try if you'd like:

 Use one of the shorting RCA -> XLR adapters (not the trafos) into the XLRs and see if you have the same issue as the RCAs. If you do, a device is suspect, if not, I bet there's an issue with the switch or wiring... As I only matched 25 sets, it MIGHT have happened! 
	

	
	
		
		

		
			



_

 

The problem being in the RCA wiring is corroborated by the fact that using Neutrik shorting RCA>XLR barrel connectors to plug the SE cable into the XLR jack makes NO difference in the channel balance when compared to using the XLR cables out of the Apogee. Both sound fine, just with a difference in overall volume levels being louder with balanced input vs single ended input. There is no imbalance when I feed the XLR an balanced or single ended signal.

 Also, your shorting switches on the back don't seem to work right. The one for the left channel does nothing, and the one for the right channel noticeably attenuates the sound with XLR or RCA input when it is switched on.


----------



## runeight

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_The goal here was to build a budget amp and limiting it to XLR sources only would have been utter nonsense and I know for a fact that this isn't the case. Besides, you can build a basic differential tube amp for 200$ that will handle the SE input just fine. 



 That's pretty much how I wired it up on my KGSS and it works perfectly in SE mode._

 

I don't think there is anything wrong with the way this amp handles SE inputs. Its input stage is no less a differential amp than would be the tube amp you are talking about or the KGSS or any of Andreas Rauenbuehler's amp designs.

 And the goal was indeed to build an amp that could be driven both SE and balanced and this one can.


----------



## spritzer

I was just talking about the basic differential tube amplifier, which Rudistor builds under the Egmont name. Tubecad also used the same circuit back in 1999. 

 Now if the switches aren't configured correctly then that could be the issue as you should get a drop in volume when switching from XLR to RCA. The easiest way to test this is with a continuity test of the input like from connectors and to the volume control.


----------



## wiatrob

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Also, your shorting switches on the back don't seem to work right. The one for the left channel does nothing, and the one for the right channel noticeably attenuates the sound with XLR or RCA input when it is switched on._

 


 Well, that was prototype case work! Something is going on with the switch/jack/ground wiring, as you recall at RMAF, both shorting switches were working. 

 Remind me never to give you any interim builds to tide you over until I finish building YOUR amp. For Free. Just razzing you... 
	

	
	
		
		

		
		
	


	




 On another note, I implemented the full RCA/XLR 4PDT switch per the website posted above on my SS version. I hear a gain difference but no channel imbalance on my SS board.


----------



## wiatrob

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_The goal here was to build a budget amp and limiting it to XLR sources only would have been utter nonsense and I know for a fact that this isn't the case. Besides, you can build a basic differential tube amp for 200$ that will handle the SE input just fine. _

 

I think HA's tests have shown it's a wiring issue due to the fact that the proto amp casework has been shuffled around quite a bit and or got damaged by my flopping power supply. You didn't see how the amp was delivered during our Xmas gift swap 
	

	
	
		
		

		
		
	


	




 As for budget, A $200 tube amp would have met EricJ's requirements even better than the eXStata. I must have missed that suggestion in the original design thread.

 One thing I am pleased with is how far Alex exceeded the original design goals ending up with something that's being compared to $5000 amps. For many head-fi'ers, 'Budget' could easily include a balanced source like a used DACmagic or a TP OPUS with full differential output. But, I think I'm veering off topic, as this is not the design thread anymore...


----------



## spritzer

You know it is always a good idea to screw down all those parts. 
	

	
	
		
		

		
		
	


	




 I did suggest the basic differential amp back in the day but never really pushed for it. I do have a PCB design ready for this amp (I designed it for my SRPP amp project where this circuit is the phase splitter/driver but with different tubes) but I've yet to order some PCB's and build it. Couple it with a simple CRC psu and a single bias supply (with a voltage divider for 230,500 and 540V) and it's an amp that anybody can build. Tube amps are also far more forgiving to noobs as a tube will take far more abuse then a transistor. Just see all those SP amps out there plus some other amps that shall remain nameless...


----------



## Beefy

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_For many head-fi'ers, 'Budget' could easily include a balanced source like a used DACmagic or a TP OPUS with full differential output. But, I think I'm veering off topic, as this is not the design thread anymore..._

 

That is a very good point though...... a balanced source doesn't have to be expensive, just like a good Stat amp doesn't have to be expensive.

  Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_Couple it with a simple CRC psu and a single bias supply (with a voltage divider for 230,500 and 540V) and it's an amp that anybody can build. Tube amps are also far more forgiving to noobs as a tube will take far more abuse then a transistor._

 

I, for one, am glad that this amp didn't go the _total_ noob route 
	

	
	
		
		

		
		
	


	




 I think Pabbi said it best when he said that anybody who can build an M3 can build this amp - and that is the perfect difficulty level for me. Complex enough to make it interesting and take a decent time to build, but without needing to source parts from several different vendors, and without a huge range of things that could go wrong.

 Just a few tubes on a board and a basic power supply holds a lot less interest to me. Similarly, I don't think I would have enjoyed building something that I perceive as being more difficult, like a KGSS.


----------



## runeight

Just an update gents, not prodding you in any way. So far I have addresses for:

 Keithpgdrb
 looser101
 tomytank
 srserl
 cetoole
 ChrisX
 digger945
 cyanoacry


----------



## wiatrob

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_You know it is always a good idea to screw down all those parts. 
	

	
	
		
		

		
		
	


	


_

 

And use thread locker! 
	

	
	
		
		

		
		
	


	




 My goal was to give HA something to listen to as I've been a little behind finishing up his amp. The most expedient way to do so was to use my proto case. Lesson learned to check all connections, inputs/outputs before turning gear over to anyone...


----------



## spritzer

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I, for one, am glad that this amp didn't go the total noob route 
	

	
	
		
		

		
		
	


	




 I think Pabbi said it best when he said that anybody who can build an M3 can build this amp - and that is the perfect difficulty level for me. Complex enough to make it interesting and take a decent time to build, but without needing to source parts from several different vendors, and without a huge range of things that could go wrong.

 Just a few tubes on a board and a basic power supply holds a lot less interest to me. Similarly, I don't think I would have enjoyed building something that I perceive as being more difficult, like a KGSS._

 

Nothing wrong with a simple tube amp and you can easily make the amp more complex by introducing a C- supply and put in bias adjustment for the tubes. Still making something complex just because is nonsense to me same as using those thick wires for what are basically line level signals. 

 I for one think the KGSS is easier to build then the exstata and just easy in general. Now the old PCB's were a giant PITA but the Headamp units are excellent and much easier to work with. No need to match to a certain value there and all the parts are easy to find. 

  Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_And use thread locker!
	

	
	
		
		

		
		
	


	


_

 

Locking shims FTW.


----------



## wiatrob

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_I for one think the KGSS is easier to build then the exstata and just easy in general. Now the old PCB's were a giant PITA but the Headamp units are excellent and much easier to work with. _

 

Of course, at $100 a board set, plus parts (and the time tracking them down - there's no published BoM or mouser project is there?) not in the same budget category. But I've yet to build one so I will defer to your experience. It is on my list as I'd like to compare the two amps someday.

  Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_Locking shims FTW._

 

Are these what we 'mericans call lock washers? 
	

	
	
		
		

		
		
	


	




 Probably use both in the future... I forget about all those audiophile 'locking' RCA clamp connectors out there putting lots of strain on the jack....


----------



## ericj

I think the simple differential tube amp got frowned on by me out of concerns over the use of popular out-of-production tubes. Not that i recall that it strictly used them. In retrospect a 6S4 version of that amp would be just fine, and i don't recall whether that's the default or not. 

 I also might have whined about the potential cost of iron - I'm a cheap person and $50 for an off-the-shelf hammond makes me wince. Even though i know that to be an irrational response. 

 One of my requirements was that it doesn't require an additional phase splitter, but i've come to understand that i needn't have worried. 

 Can't tell you how happy i am that this all came to be, though.


----------



## les_garten

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_


 Are these what we 'mericans call lock washers? 
	

	
	
		
		

		
		
	


	




 Probably use both in the future... I forget about all those audiophile 'locking' RCA clamp connectors out there putting lots of strain on the jack...._

 

Wave washers or Star washers.


----------



## les_garten

Bringing a Good Performing, Reasonably priced ES amp to the masses is a Noble endeavour!


----------



## HeadphoneAddict

Well, it's also nice to now know that one could build their eXStatA with XLR only, and simply use a $10 set of Neutrik adapters to connect an SE source to the amp, with no easily discernible degradation in the sound (when listening at 3:30AM instead of sleeping). I have a nice Jensens Transformers ISOmax box to convert RCA>XLR and visa versa, but it isn't needed.


----------



## les_garten

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Well, it's also nice to now know that one could build their eXStatA with XLR only, and simply use a $10 set of Neutrik adapters to connect an SE source to the amp, with no easily discernible degradation in the sound (when listening at 3:30AM instead of sleeping). I have a nice Jensens Transformers ISOmax box to convert RCA>XLR and visa versa, but it isn't needed._

 

This one?

Neutrik - Audio - Circular Adapters - NA2MPMF


----------



## spritzer

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Of course, at $100 a board set, plus parts (and the time tracking them down - there's no published BoM or mouser project is there?) not in the same budget category. But I've yet to build one so I will defer to your experience. It is on my list as I'd like to compare the two amps someday._

 

The BOM is printed on the board so no need for one. Just go to Mouser and search for RN60 and use the built in selector to pick out all the values needed. I always buy 100 at a time but it isn't really needed. Next step would be to buy the heatsinks (2") and find red led's with a 1.7V voltage drop (you can go higher but then you need larger sinks). Order the transistors from bdent and you are done. 

  Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_I think the simple differential tube amp got frowned on by me out of concerns over the use of popular out-of-production tubes. Not that i recall that it strictly used them. In retrospect a 6S4 version of that amp would be just fine, and i don't recall whether that's the default or not. 

 I also might have whined about the potential cost of iron - I'm a cheap person and $50 for an off-the-shelf hammond makes me wince. Even though i know that to be an irrational response. 

 One of my requirements was that it doesn't require an additional phase splitter, but i've come to understand that i needn't have worried. 

 Can't tell you how happy i am that this all came to be, though._

 

The cost of iron is a non issue (30$ R-core is what I'm using in my latest version of the amp) and new production tubes aren't a problem either. The PSU could easily use a center tapped HV winding so all the cheap transformers out there come into play. My newest amp will use ECC83's and 7N7's built on a Koss ESP10 chassis but 6SN7's would also work.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_This one?

Neutrik - Audio - Circular Adapters - NA2MPMF_

 







 That looks like it is what you want. However, after looking at that link I just noticed that with my having 4 different adapters, RCA jack to male XLR, RCA jack to female XLR, male-male XLR and female-female XLR, that all are Neutrik brand except for the "RCA jack to male" that I used for this experiment. See the one I used at the bottom of the next photo. I got both of the XLR>RCA connectors on ebay at the same time from 5150enterprises / webdealz at cox dot net, but I see that only the XLR female to RCA jack is the Neutrik brand, and the XLR male to RCA jack is some unknown brand.






 I also used the ones that came with my SAC KH1000 amp, intended for people who needed to feed the amp via single ended sources. It has their own logo on it, and looks unlike the Neutrik in the smaller details.


----------



## wiatrob

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_The BOM is printed on the board so no need for one. Just go to Mouser and search for RN60 and use the built in selector to pick out all the values needed. I always buy 100 at a time but it isn't really needed. Next step would be to buy the heatsinks (2") and find red led's with a 1.7V voltage drop (you can go higher but then you need larger sinks). Order the transistors from bdent and you are done._

 

I take it this is a different amp design than the one mentioned here:

http://www.head-fi.org/forums/1332600-post4.html

 I know that thread's 4.5 years old...


----------



## runeight

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_The BOM is printed on the board so no need for one. Just go to Mouser and search for RN60 and use the built in selector to pick out all the values needed. I always buy 100 at a time but it isn't really needed. Next step would be to buy the heatsinks (2") and find red led's with a 1.7V voltage drop (you can go higher but then you need larger sinks). Order the transistors from bdent and you are done. 

 The cost of iron is a non issue (30$ R-core is what I'm using in my latest version of the amp) and new production tubes aren't a problem either. The PSU could easily use a center tapped HV winding so all the cheap transformers out there come into play. My newest amp will use ECC83's and 7N7's built on a Koss ESP10 chassis but 6SN7's would also work._

 

If I may offer a thought or two. Hopefully they will be helpful.

 Regarding the KGSS, I happen to think (for what my opinion is worth) that the KGSS is a pretty cool amp and a really nice design. I'm pretty sure that I said this in the original thread when contemplating taking on designing a new stat amp. May have even said it on another occasion too. And, in fact, I mean it.

 I don't know how it performs in real life or how difficult/easy a build it is, but I imagine that it does perform very well and it has a nice high PP voltage capability, more than the eXStatA is designed to have.

 In fact, I think enough of this amp that I think, Spritzer, it deserves its own thread, if it doesn't already have one or even several, where its design features, its board features, its PS featuers, its bias supply features can be put forth (beyond the HW article) and its builders can talk about it. Perhaps now is a good time to start one for those who are interested in building one. 
	

	
	
		
		

		
		
	


	




 As for alternatives to the eXStatA, there are at least a handful of these, including all-tube amps and other possible SS designs or hybrids. I can't say which would be better or what individual diyers might prefer to build. I certainly don't expect that every diy stat builder would think that the eXStatA has a corner on the diy amp market. It certainly does not. It simply does what it was designed to do at a reasonable cost. It does not do any more than that. We had a bit of discussion about alternatives on ericj's original thread and perhaps it is also worthy of more discussion on an new thread to explore some of those other possibilities. Although, as I think I said in my first post on this thread, there is hardly anything new under the sun in analog audio. Every single subcircuit in the eXStatA has been done before. Maybe even the whole amp has been done before, I just simply could not find anything in the places where I could search. As nearly as I an tell from what I know, every subcircuit in the KGSS or the BH or Andreas' amps have been done before. Sometimes, these days, someone comes up with a new combination or a better refinement, but the fundamental building blocks haven't really changed much. Diff amps, current mirrors, Vbe multipliers, followers, splitters, CCSs, cascodes, etc. have been around the block many times. Some of them are older than I am and that makes them pretty ancient. 
	

	
	
		
		

		
		
	


	




 I certainly would enjoy reading those discussions and contributing if I had anything useful to add.

 In the meantime gents, keep sending me your addresses and I will get the boards out. Most of them should go in the mail before the week is out.

 Yours,
 Dr. Cavalli
 PhD, Plasma Physics
 Thermonuclear Fusion


----------



## wiatrob

OK, Dr. C, I will stop hijacking the thread with discussions of other amps... and look forward to exploring other designs in their appropriate venues.


----------



## macm75

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_I for one think the KGSS is easier to build then the exstata and just easy in general. Now the old PCB's were a giant PITA but the Headamp units are excellent and much easier to work with. No need to match to a certain value there and all the parts are easy to find. 
 Locking shims FTW._

 

Out of curiousity, is the KGSS Headamp board designed to accept the "old" 2SK389 or the "new" LSK389?

 Edit: sorry about the question. I did not see the top 2 posts while writing mine.


----------



## spritzer

If somebody wants to start a thread for a DIY KGSS then go ahead. I'm not going to (already built 3 and one more due soon) but I did want to correct the assumption that the KGSS is more complex then any of the AMB amps. Just because something doesn't have a BOM, doesn't make it complex. It's the same thought doesn't drive people to find subs for transistors that are OOP. 

 As for the other amp designs out there, most are easy to build and I'm a firm believer in people cutting their teeth on P-P wiring a circuit. 

 As for the circuits being used before, Andrea's amps do quite a bit more then just borrow from old Stax designs. I recently acquired a Stax schematic (yet to have it in my hands though) but from the pics it's clear where he got his SS design. Nothing wrong with it really until some bright spark decides to make it as a commercial model and then bad things happen. 

  Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I take it this is a different amp design than the one mentioned here:

http://www.head-fi.org/forums/1332600-post4.html

 I know that thread's 4.5 years old..._

 

Same one but the KGSS cost 1500 or even less back then. I also built a rather crazy version back in the day which has now been scrapped for parts, the top half now houses my BH amp section while the old PSU is now a complete KGSS. It would have made more sense to just buy one from Justin but I instead ordered the most expensive BH he built. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_Out of curiousity, is the KGSS Headamp board designed to accept the "old" 2SK389 or the "new" LSK389?_

 

2SK389's or matched singles. LSK389's can easily be used if you bend the pins on the metal can version or use the SMD version with the clever little adapter. It isn't really an issue since 2SK389's are still plentiful and I've more then once been offered to buy 1000+ units recently.


----------



## runeight

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_As for the circuits being used before, Andrea's amps do quite a bit more then just borrow from old Stax designs. I recently acquired a Stax schematic (yet to have it in my hands though) but from the pics it's clear where he got his SS design. Nothing wrong with it really until some bright spark decides to make it as a commercial model and then bad things happen. 
_

 

Well, it is most certainly my limitation, but I don't know where to find old stax design schematics and don't know how many have been published. But, I can guess that even the older stax amps use circuit topologies that are principally a re-use of fundamental building blocks, although perhaps put together in clever ways by the stax designers.

 I don't know Andreas personally, perhaps you do, but it is not certain to me that he simply derived his amp designs from stax designs. He may simply have come up with the ideas himself, but nonetheless made a similar design. Given the limited numbers of ways to do things, I think this is pretty common. How many power amplifiers use complementary output topologies? Millions. Yet when another designer uses one this does not make him a copy cat, he's just using proven design components. How many amps use constant current sources? Millions. Yet a new designer using one does not make him copy cat. And no commercial manufacturer is going to prevent someone from using a simple complementary O/P stage or a current source unless it includes particular and exclusively owned added features.

 In my very first post to this thread I indicated that I had looked for circuits similar to the exstata on the web and did not find any. But, I also suggested that those of you who are more familiar with these designs would certainly say if there were indeed prior amps with the same design. Please feel free to do so now. I, for one, would be pleased to know the facts that I may not know now.


----------



## Beefy

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_It's the same thought doesn't drive people to find subs for transistors that are OOP... 

 ...As for the other amp designs out there, most are easy to build and I'm a firm believer in people cutting their teeth on P-P wiring a circuit._

 

Wiring is my least favourite part of a build, and dredging through datasheets my least favourite part of planning. Why would I want to do a build where I specifically have to dredge through datasheets, and do lots more wiring?


----------



## ericj

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Wiring is my least favourite part of a build, and dredging through datasheets my least favourite part of planning. Why would I want to do a build where I specifically have to dredge through datasheets, and do lots more wiring? 
	

	
	
		
		

		
		
	


	


_

 

As i've said before, though, one of the reason i was looking for an amp with printed boards was that although I've built several amps with voltages mostly under 40v point-to-point, the potential for disaster building a complex point-to-point board with 1kv across it is just too great for most DIYers.


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_And no commercial manufacturer is going to prevent someone from using a simple complementary O/P stage or a current source unless it includes particular and exclusively owned added features._

 

one of the most amazing things I've seen was TI recant on using Nelson Pass's "super-symmetry" topology. You know TI has the lawyer power to win, but it was very sportsman of them to admit they were wrong.


----------



## runeight

Maybe Nelson had better lawyers.


----------



## Emooze

Nelson Pass has one hell of a mustache. You don't mess with a man of that caliber.


----------



## n_maher

Folks, let's try to keep this thread a bit more on topic, ok?


----------



## pabbi1

Really enjoying my hybrid - is anyone besides Bill and (hopefully) Larry enjoying theirs yet? Or, anyone NOT enjoying theirs?


----------



## Beefy

Everything on mine is soldered, PSU tested, and ready to go, except I am still waiting on my Stax jack and parts for my volume control before I can listen......


----------



## runeight

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Folks, let's try to keep this thread a bit more on topic, ok?_

 

Happy to do that Nate, but there is a backhanded implication in this statement by Spritzer:

  Quote:


 As for the circuits being used before, Andrea's amps do quite a bit more then just borrow from old Stax designs. 
 

that the eXStatA is a directy copy of a Stax amp. Now if it is a copy, I don't have any issues acknowledging that I happened to come up with a design that's already been done. We are all doing that all the time. And for this little diy community I rather suspect that Stax doesn't mind if its something no longer in production.

 If it is a copy then we'll fulfill the current board committments and then stop the diy availability.

 So if this is Spritzer's implication, that this is a direct copy of a stax amp, then I would like Spritzer to say which Stax amp it is and show the fact that it is a copy. If it is not then I want the backhanded innuendo to stop and I want you to enforce that.

 Your call.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Really enjoying my hybrid - is anyone besides Bill and (hopefully) Larry enjoying theirs yet? Or, anyone NOT enjoying theirs?_

 

I'm NOT enjoying waiting for my custom PS iron... But the end justifies the means, or this case, the wait.


----------



## Emooze

I left mine in my apartment over winter break because I have no case yet. Looking at the Nabu though, any more comments on it?


----------



## spritzer

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_that the eXStatA is a directy copy of a Stax amp. Now if it is a copy, I don't have any issues acknowledging that I happened to come up with a design that's already been done. We are all doing that all the time. And for this little diy community I rather suspect that Stax doesn't mind if its something no longer in production.

 If it is a copy then we'll fulfill the current board committments and then stop the diy availability.

 So if this is Spritzer's implication, that this is a direct copy of a stax amp, then I would like Spritzer to say which Stax amp it is and show the fact that it is a copy. If it is not then I want the backhanded innuendo to stop and I want you to enforce that.

 Your call._

 

You completely misunderstood my point there. Andreas SS amp is heavily based on the SRM-1 Mk2 but I clearly wasn't talking about the exstata as this was in the context of other 'stat amp designs, some being unique and others borrowing from one another. 

 As for this discussion, I'll ignore everything exstata related except I'll post the measurements of the amp when I have them.


----------



## BoilermakerFan

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_I left mine in my apartment over winter break because I have no case yet. Looking at the Nabu though, any more comments on it?_

 

NABU will work just fine though you may have to Dremel off the existing transformer mounting studs. That trafo is a 125VA frame so it's about 1" larger all round:


















 You'd even have room for an AudioSector DIY DAC or Phono Stage:


----------



## nattonrice

I spy another very sexy jack...


----------



## n_maher

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Everything on mine is soldered, PSU tested, and ready to go, except I am still waiting on my Stax jack and parts for my volume control before I can listen......_

 

I'm in the same boat.


----------



## luvdunhill

wow, that's a nice fit. Dressing the NABU up can be a bit hard though, but looks promising!


----------



## n_maher

Here are the basic ground rules for how this thread can remain open and members can avoid "trouble".

 1. Keep it civil. If you have something to say, say it nicely or it'll be removed regardless of its value.

 2. Keep it close to the topic. Obviously there's no hard and fast rule about discussing tangentially related projects in the same thread but let's try to keep it to the point where someone building this and looking for advice doesn't have to wade through 10 pages of rambling to find one useful tidbit.

 3. Accusations of design infringement, copying others work and so on are not helpful and don't belong here. I'm going leave what has been said up to this point but would appreciate it if this was not taken further in this thread. So far no part of the eXStata appears to be headed in the commercial direction and if Alex's design happens to resemble something Stax already did, well, I just don't care or see how it's relevant. If you'd like to discuss that with Alex I'm sure he'd read a PM about it. If you have concerns that the potential exists for legal issues as a result of this thread take it up with Jude. I don't see any so I see no reason to waste more time thinking about it.


----------



## runeight

Alright then, we shall move forward.

 I have addresses for the following:

 Keighpgdrb
 looser101
 tomytank
 Sathimas
 srserl
 cetoole
 sumo-kun
 macm75
 FrankCooter
 ChrisX
 m3ental
 digger945
 cyanoacry
 WilCox

 I still need:

 manaox
 carlseibert
 XXII
 currawong
 bidoux
 acmemr

 If I don't hear from you guys I will PM you one last time. 

 As it turns out, Fedex is really efficient. Boards will arrive today.


----------



## BoilermakerFan

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_wow, that's a nice fit. Dressing the NABU up can be a bit hard though, but looks promising!_

 

Plenty of room. That's my mule chassis. Everything gets test fitted in that one before I take a drill or punch to another one, hence all the extra holes and bits.

 The Nabu chassis is actually pretty easy to dress up if your willing to put the elbow grease into it and take it to a body shop to be bead or soda blasted, etched, primed, and painted. Then you can use dry transfer, decals, or paint on your labels, and have the whole thing clear coated. The top of the chassis is huge and is a pretty nice sized canvas for custom graphics or cut outs. 

 I have 3 neat designs for the ones I'm building. Then the lids go to the body shop for their paint, back to me for pin striping and labels, then clear coats and a bake at the body shop. Also have plans to really mod the top of one build. I'm actually going to bring the top down into the chassis with a lot of metal work, some extra sheet metal, and lead to fill the voids.

 You can use long standoffs to support things through the top deck too. I'm using a NABU to house my DIY CD transport which is a top loader.

 The front panel can be wood, metal, or plastic. I've seen all 3 done with great success. 

 I'm forever grateful to pabbi1 for pointed them out to me.


 That reminds me, I need to order 10 more...


----------



## TimJo

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Really enjoying my hybrid - is anyone besides Bill and (hopefully) Larry enjoying theirs yet? Or, anyone NOT enjoying theirs?_

 

My hybrid is ready and waiting and UPS delivers my SR-404LE's tomorrow. 
	

	
	
		
		

		
		
	


	




 I'll be sure to update the thread with my impressions this weekend. I can't wait...


----------



## audionut

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_My hybrid is ready and waiting and UPS delivers my SR-404LE's tomorrow. 
	

	
	
		
		

		
			





 I'll be sure to update the thread with my impressions this weekend. I can't wait..._

 

TimJo, Really looking forward to your impressions on the 404LE's. Really interested in these phones and they may be my next stat purchase. Have you by any chance heard the ESP-950's (my phones)? They sound fantastic with my exstata hybrid, but would like to know how they compare to the 404LE's after you've had the chance to listen to your new phones
	

	
	
		
		

		
		
	


	



 Thanks, Tommy


----------



## Emooze

Thanks boilermaker. though I'm using the two triads so it may end up just being the transformers in that space.

 And did any of the circuitry it came with work? I might have some ideas for it.


----------



## cat6man

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_My hybrid is ready and waiting and UPS delivers my SR-404LE's tomorrow. 
	

	
	
		
		

		
		
	


	




 I'll be sure to update the thread with my impressions this weekend. I can't wait..._

 

my 404LE's will arrive on friday.............if you send me your hybrid (i discovered this thread a couple of days too late to get in on the latest build), i'll be glad to evaluate the combo for you


----------



## luvdunhill

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_The Nabu chassis is actually *pretty easy* to dress up [size=x-large]if[/size] your willing to put the elbow grease into it and take it to a body shop to be bead or soda blasted, etched, primed, and painted. Then you can use dry transfer, decals, or paint on your labels, and have the whole thing clear coated. The top of the chassis is huge and is a pretty nice sized canvas for custom graphics or cut outs._

 

heh


----------



## Beefy

Well my Stax jack finally arrived, after three weeks. Priority mail indeed, Canada Post! 
	

	
	
		
		

		
		
	


	




 But I think it was worth the wait. The jack itself is gorgeous - a perfect fit, just snug enough to be secure on the plug without being difficult 
	

	
	
		
		

		
		
	


	




 The backing piece...... perhaps not as gorgeous. It might be an optical illusion, but the tapped screw holes don't seem very accurately placed, and I certainly wouldn't want to rely on that as my only method of attachment. I suspect I will have to drill out the thread on this piece to get everything to line up perfectly with the holes on my FPE panels.

 I can also finish my volume control now as well. With any luck, I might have sound over the weekend!


----------



## BoilermakerFan

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_heh_

 

I'd rather torture sheet metal than match transistors... 
	

	
	
		
		

		
		
	


	




 But then again, steel is in my blood and there is nothing like the burn from a hot metal chip embedding itself in your forearm when going to town with a Uni-Bit. 

 I just wish it would get above freezing so I can get out in the garage to make chips.


----------



## luvdunhill

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_The backing piece...... perhaps not as gorgeous. It might be an optical illusion, but the tapped screw holes don't seem very accurately placed, and I certainly wouldn't want to rely on that as my only method of attachment._

 

Believe it or not, the threads are very strong. As for alignment, measure between the two holes in one dimension and compare to the distance in the other dimension. They should be the same, with the hole being in the center. Now, whether or not the center of the hole is in the center of the backing piece, that could be off, but the above should be spot on. Let me know what you find!


----------



## bidoux

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_bidoux

 If I don't hear from you guys I will PM you one last time. 
_

 

I PM-ed you, I don't know if you received it or if you didn't have time to answer it. I am just wondering in which ways you want to be paid for the boards.


----------



## n_maher

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_The backing piece...... perhaps not as gorgeous._

 

It is the same way on the one that I have, definitely not symmetric.


----------



## TimJo

Quote:


  Originally Posted by *bidoux* /img/forum/go_quote.gif 
_I PM-ed you, I don't know if you received it or if you didn't have time to answer it. I am just wondering in which ways you want to be paid for the boards. 
	

	
	
		
		

		
		
	


	


_

 

Here are Alex's instructions a few pages back...

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Boards are shipping today. Should be here by Thu. Time for you guys to start sending me your shipping addresses. Instead of PMs, please email me directly at:

 alex at cavalliaudio dot com

 I will give you your totals once the packages are in the mail along with my paypal email._


----------



## Beefy

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Believe it or not, the threads are very strong. As for alignment, measure between the two holes in one dimension and compare to the distance in the other dimension. They should be the same, with the hole being in the center. Now, whether or not the center of the hole is in the center of the backing piece, that could be off, but the above should be spot on. Let me know what you find!_

 

I'll try and find some calipers at work tomorrow, and report back.


----------



## TimJo

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_TimJo, Really looking forward to your impressions on the 404LE's. Really interested in these phones and they may be my next stat purchase. Have you by any chance heard the ESP-950's (my phones)? They sound fantastic with my exstata hybrid, but would like to know how they compare to the 404LE's after you've had the chance to listen to your new phones
	

	
	
		
		

		
		
	


	



 Thanks, Tommy_

 

Yeah, I was trying to choose between those and the 404LE's, and decided on the later based on comments in various threads on the forum. I am hoping to hear the ESP-950's at some point. Who knows, maybe I'll own two pairs of stats before too long.


----------



## pabbi1

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_I left mine in my apartment over winter break because I have no case yet. Looking at the Nabu though, any more comments on it?_

 

This is what you can do with a Nabu, DAC, DAC psu, dual amp boards, and dual trannies. For $25 shipped, pretty decent. The psu, digital cable, and variety bits are just bonus.






 And, they don't look terrible, with minimal elbow grease. In fact, it is the closest thing to an off the shelf case NOT specifically designed into the project.






 Oh, and eBay has panels that just need to be cut to length... in a variety of woods.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_




_

 

I like the look with the top flipped 180 so it makes a hood. Hmmmm. Maybe I laid out my graphic "upside down." That's given me another idea or two. Thanks yet again Al. 
	

	
	
		
		

		
		
	


	










 Yeah, I owe you at least 3 beers if I ever make it down to Dallas again.


----------



## runeight

The following packages are going out today:

 Keighpgdrb
 looser101
 tomytank
 Sathimas
 srserl
 cetoole
 sumo-kun
 macm75
 FrankCooter
 ChrisX
 m3ental
 digger945
 cyanoacry
 WilCox
 carlseibert
 currawong
 manaox

 I still need:

 XXII
 bidoux
 acmemr

 bidoux, I know you are working on this.


----------



## runeight

All but three boards went out this morning. Those of you in the US should get them next week sometime. Those outside the US, I can't predict.

 But, please let me know if I sent you the wrong boards or, for you US guys, you don't have anything by end of next week.


----------



## Beefy

Due to a severe case of grant writing procrastination, I finally powered up my Exstata SS boards this morning for their initial setup. No listening impressions yet as I still need to wire up my Stax jack and volume control, but I do have a few comments on the build and set up......

 Xicon 273-1K-RC are not a good substitute for the previously out of stock Vishay 71-RN55D-F-1.0K at amp R21 and R22. They are too big, so they have to be mounted rather creatively so that they don't touch the nearby transistors. I doubt Mouser will ever be out of stock of such a common resistor again, but it is still worth mentioning. The Xicon are fine at power R5 and R6 though.

 If you are screw mounting your heatsinks, there are a couple of traces that get very close to the screw heads on the underside of the board. I used spare isolating washers from the mounting kits to make sure there is absolutely no possibility of the screw head shorting to the traces.

 Also for screw mounting heatsinks, even 4-40 screws are too big to fit through the holes on the board. I didn't have a drill handy, so I tapped the holes and they hold a thread surprisingly well. Much easier and cleaner to do with a blank board though, rather than discovering this after populating almost everything.

 The dummy load resistors get HOT. I would suggest sitting them on top of something that can act as a heatsink. I sat them on two front faceplates from HiFi2000 Pesante cases...... that is almost a kilo of solid aluminium soaking up the heat, and the resistors were still too hot to touch.

 The shunt transistors get warmer when connected to the amp than when they do connected to the dummy load. In a highly scientific test, with the dummy load they are cooler than the CCS sinks; with the amp they are warmer than the CCS sinks. So it seems the dummy load draws just a bit more current than an idle amp. I'm still planning on decreasing the current through the PS once I have a handle on dynamic current draw. I wonder if there is an easy way to measure the shunted current, rather than measuring amp draw? It would make tweaking this really easy.

 The heatsinks on amp Q11 and Q12 run a lot cooler than I expected.

 Amp Q3 and Q4 run a lot hotter than I expected. I'm tempted to see if I can add some sort of heatsink, but it will be pretty tight in there given the proximity to Z1

 Both balance and offset are very easy to get below - and keep below - ±1V. But they do seem to drift up and down alot in the 10s to 100s of mV range over time. Mind you, with a gain of ~1000 and the inputs floating, I'm not entirely surprised that there is a little movement.

 I split my boards apart, and plan to switch the positions of the two channels in my final layout. I figure it will keep the two sets of -300V and GND wires together, and allow better airflow between the boards.

 That is all I can think of for now. Cost, $0.02 - no refunds, store credit only.


----------



## scompton

I'm afraid to work on mine now because every time I touch something metal I get a static shock. I tried a grounding wrist strap from Radio Shack, but it didn't work very well and the cable was too short. Does anyone have suggestions on what I can use?


----------



## pabbi1

Static Guard? Pretty sure it is widely available... I have never crapped out anything with static, and only a few parts here would be suceptible anyway.

 WRT board splitting, I split on one build, which made for earier wiring, then didn't on the other two - no sound differences at all, so really just a build preference.


----------



## runeight

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_
 The shunt transistors get warmer when connected to the amp than when they do connected to the dummy load. In a highly scientific test, with the dummy load they are cooler than the CCS sinks; with the amp they are warmer than the CCS sinks. So it seems the dummy load draws just a bit more current than an idle amp. I'm still planning on decreasing the current through the PS once I have a handle on dynamic current draw. I wonder if there is an easy way to measure the shunted current, rather than measuring amp draw? It would make tweaking this really easy.
_

 

Thanks for all of the build guidance. I'm sure that the next group of folks will appreciate it. 
	

	
	
		
		

		
			





 I know that we've talked about this and I know that you intend to do it, but I don't recommend minimizing the shunt currents. Take a look at the PS schematic and you will see that there are many paths for the shunt currents. This includes the paths through R9/R12, the path through Q9-Q12, the paths through R15/R16 and the lastly the paths through the primary shunt devices. Each of the smaller paths consumes current and if you dial down the shunt currents you will set the regulator so that, while there is shunt current, none of it is going through the MJE devices and you will defeat the regulator to some degree. Furthermore, even if they are active they need some amount of idle current, somewhere around 2mA to get into a decent operating condition.

 To set all the paths with enough current for proper operation you need at least 5mA more than the load draws on each rail. 6-7mA won't hurt. More than this is not necessary.

 Just wanted to point out, one more time, that there is a reason why things are set the way they are.


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Furthermore, even if they are active they need some amount of idle current, somewhere around 2mA to get into a decent operating condition._

 

Ah, that is a useful little nugget. That will give me something to aim for if I can be bothered after the stern warnings...


----------



## runeight

LOL. You're just lucky that you are so far away from where I live.


----------



## ericj

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_I'm afraid to work on mine now because every time I touch something metal I get a static shock. I tried a grounding wrist strap from Radio Shack, but it didn't work very well and the cable was too short. Does anyone have suggestions on what I can use?_

 

Wait, anything metal at all or anything metal in your amp?


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_LOL. You're just lucky that you are so far away from where I live. 
	

	
	
		
		

		
		
	


	


_


----------



## scompton

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_Wait, anything metal at all or anything metal in your amp?_

 

My Klipcsh IEMs, the car body though my coat, door knobs, screws holding on light swith plates, etc, so any metal I touch this time of year gives me a static shock. I tend to get 2 or 3 just getting out of the car, on my triceps, though my coat.


----------



## Beefy

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_My Klipcsh IEMs, the car body though my coat, door knobs, screws holding on light swith plates, etc, so any metal I touch this time of year gives me a static shock. I tend to get 2 or 3 just getting out of the car, on my triceps, though my coat._

 

I would strongly suggest taking off your shoes and socks when working with electronics. A humidifier would help as well.


----------



## les_garten

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I would strongly suggest taking off your shoes and socks when working with electronics. A humidifier would help as well._

 

Yeah, you don't want't that HV wondering which direction to go!


----------



## BoilermakerFan

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_My Klipcsh IEMs, the car body though my coat, door knobs, screws holding on light swith plates, etc, so any metal I touch this time of year gives me a static shock. I tend to get 2 or 3 just getting out of the car, on my triceps, though my coat._

 

So do you always keep a micro Van Der Graph generator in your pocket?

 But, in all seriousness, I would get a small humidifier and take off any rubber soled shoes. Touch the metal chassis or grounding pad with the back of your hand to ground yourself out and then you should be fine to work. That is, unless your carpet is part of the issue and just shuffling your feet will generate enough charge...


----------



## scompton

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_So do you always keep a micro Van Der Graph generator in your pocket?

 But, in all seriousness, I would get a small humidifier and take off any rubber soled shoes. Touch the metal chassis or grounding pad with the back of your hand to ground yourself out and then you should be fine to work. That is, unless your carpet is part of the issue and just shuffling your feet will generate enough charge..._

 

LOL, I don't know what causes it but I get it this time of year. I went for a walk at lunch and I had my X5s in my ears and got a few static shocks from the barrel.

 I'll try a portable humidifier. We have a whole house humidifier but we have to keep it pretty low. The main level of our house is brick and terracotta block masonry, with plaster right on the block. The walls are pretty cold. If it gets too humid, we get condensation on the walls. You can really feel cold radiating off of the walls. The house leaks heat so much that I never have to scrape frost off the car parked next to it in the driveway.


----------



## pabbi1

Or, like I did and replace all the carpet with tile, travertine, or wood. One nasty shag carpet room remains, but it is a bedroom, and just seems wrong to not have carpet there.

 So, certainly TimJo has new phones, and someone else has _some_ listening impressions?


----------



## TimJo

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_So, certainly TimJo has new phones_

 

Just plugged them in for the first time. 
	

	
	
		
		

		
			





 Too soon to say much, other than they sound really nice, but very different compared to the CTH and DT 880 combo I've grown to love. I'm beginning to think that my ears may have gotten used to a more colored sound, and now I am hearing a truer representation of what is sitting in the record's groove.

 The amp is fantastic sounding (albeit only minutes into burn-in) and there is no shortage of bass extension with the 404LE's, so I am happy. 
	

	
	
		
		

		
		
	


	




 Thanks Alex for giving us an affordable, high end amp. I doubt I'd be listening to stats right now without your generosity to the head-fiers. Thanks!!!


----------



## XXII

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_
 I still need:

 XXII
 bidoux
 acmemr

 bidoux, I know you are working on this._

 

Hi Alex,

 I've sent you a pm regarding this.


----------



## runeight

Yes, got it now.


----------



## luvdunhill

Thinking more about a measurement jig... would a capacitive divider work? Say a 3pF capacitor with a 3000pF capacitor for the bottom of the attenuator. Perhaps add a voltage buffer... Result, dead 'scope? Dead amp? Dead people? Or.... ghetto wide frequency 1000:1 probe?


----------



## Beefy

Its alive! And making sweet, sweet music 
	

	
	
		
		

		
		
	


	









 Very early impressions are that it exceeds even the lofty expectations raised by Pabbi, headphoneaddict and others. Certainly superior to my previous t-amp SRD7-SB combo. Dead silent noise floor at normal listening volumes.

 Mounting everything in the case will commence this week, as will the FPE order.


----------



## luvdunhill




----------



## les_garten

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Its alive! And making sweet, sweet music 
	

	
	
		
		

		
		
	


	









 Very early impressions are that it exceeds even the lofty expectations raised by Pabbi, headphoneaddict and others. Certainly superior to my previous t-amp SRD7-SB combo. Dead silent noise floor at normal listening volumes.

 Mounting everything in the case will commence this week, as will the FPE order._

 

Nice! What Vol control is that?


----------



## Beefy

I'll let the person behind the volume control speak up if they so choose.

 Suffice to say, it is _freaking fantastic_. Well, once it is wired up correctly anyway....


----------



## digger945

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Its alive! And making sweet, sweet music 
	

	
	
		
		

		
		
	


	


_

 

 Quote:


 ...it exceeds even the lofty expectations... 
 

  Quote:


 Certainly superior... 
 

 Quote:


 Dead silent noise floor... 
 


 I'de say he's got the bug.
	

	
	
		
		

		
		
	


	




 Very nice, as usual, Beefy.


----------



## luvdunhill

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I'll let the person behind the volume control speak up if they so choose.

 Suffice to say, it is freaking fantastic. Well, once it is wired up correctly anyway.... 
	

	
	
		
		

		
		
	


	


_

 

Documentation has never been my strong suit 
	

	
	
		
		

		
		
	


	




 Haven't I hi-jacked this thread enough? I guess this is one of those things boiling in kitchen so to speak. Looks like magic, but it's functionally a balanced 192-step attenuator (down to -95.5dB) in the mode that Beefy has configured it in. 

 I'm not sure what Beefy spent on it, but I know he has the current record for cheapest build (not including power supply and random 0805 resistors that might have went flying in the process).


----------



## Beefy

I'll hijack it then 
	

	
	
		
		

		
		
	


	




 Its a balanced PGA2320 volume control, with rotary encoder. Usable rotation is much better than a pot, without having to turn way too many times to get volume. Encoder has a push switch shaft for mute. 

 Cost outlay was very low - _well_ under $50. But the PGA chips were obtained at a significant discount.


----------



## runeight

Well gents, I don't mind a little hijacking. How about some more information.


----------



## Beefy

Considering mine is only the second functional unit, I think it is a long way from prime time


----------



## luvdunhill

It's that pesky mod that hangs around here that I worry about 
	

	
	
		
		

		
		
	


	




 In this case, the devil is in the software, but the rest is fair game.

 The datasheet is here:

http://focus.ti.com/lit/ds/symlink/pga2320.pdf

 and the microcontroller I'm using:

http://www.atmel.com/dyn/resources/p...ts/doc8006.pdf

 My layout is here:











 Pretty straightforward and I tried to follow all the layout guidelines from the datasheet and what not. Trying to find time to work on developing the "companion" board in the next few weeks.

 Here is what it looks like in it's intended deployment:


----------



## dBel84

way too tangential, shouldn't be allowed I tell you. 

 Marc, have you got a thread dedicated to this? I would like to read more about it. Looks fantastic. Great work too Beefy , looking very neat ..dB


----------



## Beefy

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_Great work too Beefy , looking very neat ..dB_

 

Thanks, I'm pretty happy with it so far.

 I think I might be getting some occasional static in the right channel though. Could be anything along the chain; USB board, DAC, XLR cables, amp, volume control and phones are all new/untested or very recently reconfigured. Will try and chase it down in the morning......


----------



## runeight

That's very cool Marc. I agree with Don, more people will be interested when you get it solid enough and if you want to make it available at large.

 Beefy, looks like a really nice looking build is in the works.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_I was pretty sure Blutarsky wanted a set of boards, but he is out of town all last week/this week and probably doesn't know about the new sets._

 

Bummer - I posted that 12/28 and Bluto just got back in touch with me, after a family trip and then a ton of work keeping him away. He did indeed want a set of Hybrid boards and was sad when I told him was too late. This is the second run of beta boards he has missed out on because of his work demanding his time. If anyone has a set they can part with and can PM him about it (and can wait a few days to hear back) that would be great.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Its alive! And making sweet, sweet music 
	

	
	
		
		

		
		
	


	




 Very early impressions are that it exceeds even the lofty expectations raised by Pabbi, headphoneaddict and others. Certainly superior to my previous t-amp SRD7-SB combo. Dead silent noise floor at normal listening volumes.

 Mounting everything in the case will commence this week, as will the FPE order._

 

I'm so very glad you like the amp. And here I was worried that maybe I had set some unreasonably high expectations. It really shouldn't sound this good, but then I remember how good the CTH and EHHA sound and I'm not surprised (Bill's balanced EHHA is serious competition to my ZDT).


----------



## digger945

Alex,
 Would it be fairly accurate to say that the series "center section" of the amp that includes the 271s, from R29 to R9 is roughly 200k+, and that the current in this section is roughly 3mA?

 I'm guessing about 25k for P1. 
 I'm mainly just trying to get the current through this section to do some more calculations.


----------



## runeight

The tail current is designed to be about 2mA putting 1mA into each jfet all the way to the negative rail. The total tail resistor is around 150k which is what sets this current since this "resistor" spans from +300V to slightly less than ground.

 The current mirror multiplies this current by 3X putting about 3mA into the HV device whether it's the BJT or the triode.


----------



## digger945

I guessed 150k for the tail initially. 
 I got in a hurry in the post above. I should have said "through R29" instead of "from R29 to R9." 
 Thanks Dr. Cavalli.


----------



## TimJo

Well, I haven't had as much free time this weekend as I was hoping for, but I did listen quite a bit yesterday morning, and I can give you some impressions so far.

 The first thing is the amp is dead quiet. On my amp, I mounted the connectors for the heaters on the underside of the board, so the heater wiring is far from all of the other wiring. The casework is not ready, so actually the whole thing is currently only mounted on plywood, with the star grounds only connected to the ground wire on the ac input terminal block. Even with this temporary setup, it is dead quiet.

 As far as the boards go wrt heat dissipation, the power supply doesn't produce much heat at all. The amp heatsinks are also only warm - far from hot. The biggest source of heat that I am noticing is from the tube heaters to tell the truth.

 This is my first time listening to stats, and the whole listening experience is so different than dynamics that I'm not sure I'm the right person to judge the amp, but here's what I notice so far.

 The amp appears to have a great deal of speed with precise control. I started out with a few albums I know well, and what was apparent was the reproduction of echo and reverb is very realistic sounding. One album was David Crosby's _If Only I Could Remember My Name_, which was recorded at Wally Heider's. This studio had a very unique sound, and this amp does an amazing job of reproducing the subtleties of their echo chamber which to me points towards precision of the amp to keep each channel tightly in phase with the groove of the album. Anyway, not sure if that's true, but that's how it feels.

 The amp has tons of low end, which is great as well. I love bass guitar, and the amps really shines here. It's not hit you over the head bass power, instead its again very precise which means you can actually hear what the player is doing. It seems too that this presence and control is also there at low listening levels, which seems different than dynamics. I notice I can get all of the bass I want without the urge to turn up the volume.

 Beyond this, then things probably begin to become headphone dependent, and again the SR-404LE's are my first and only stats. My first impressions there is that the soundstage seems smaller as compared to my Beyer's, which is taking some adjustment in listening. Vocals are amazing on the 404's. I'm also thinking I like acoustic music better than electric on the stats, but I need to do more listening before I can judge. Let me rephrase that, it may end up being that I like listening to rock on dynamics better than stats, but like I said, I'll need more time to listen before I decide.

 Overall, I'm really impressed with this setup. I'm listening to Pavement's release _Crooked Rain_ right now, and it sounds great. The reproduction of the harmonics coming from Malkmus' jazzmaster is simply amazing...

 Thanks again Alex!


----------



## pabbi1

Ah, a playah... have a listen to Marcy Playground (mid 60's strats), Zappa (Joe's Garage or Sheik Yerbouti - 50's strats, and the Hendrix Monterrey strat), Neil Young (Martins and that 1956 Gibson LP), The Who (Tommy or Who's Next for a J200, Quadrophenia for Entwistle's Alembic), Rolling Stones (Sticky Fingers - a beautiful Gibson Hummingbird) - just definitive.

 For electronic, spin up some DEVO, Wall of Voodoo, or NIN (Pretty Hate Machine is like a mushroom induced haze).

 For an epiphany, Radiohead's "Packd like Sardines in a Crushed Tin Box" is not only euphonic, but utterly overwhelming with the detail and texture.

 This is not just an amp - it is it's own instrument, where you can listen, and, if so inclined, analyze - but while having fun. That is pretty rare, regardless of budget,


----------



## Emooze

If you don't mind trance music, get your hands on some Infected Mushroom. I found they sound exceptional with 'stats.


----------



## TimJo

Yes, I feel like I'll be busy listening to my whole record collection again over the coming months (well years) to discover the nuances hiding in the grooves. Thanks for all the suggestions Al. I can tell we have similar tastes in music. This will certainly be fun. 

 A quick question from a stats noob - I'm assuming its normal for there to be a crackle/pop sound when plugging in the connector to the amp, right?


----------



## TimJo

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_This is not just an amp - it is it's own instrument_

 

Just reread what you wrote - and that is a great way of describing this amp.


----------



## cat6man

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_
 The amp appears to have a great deal of speed with precise control. I started out with a few albums I know well, and what was apparent was the reproduction of echo and reverb is very realistic sounding. One album was David Crosby's If Only I Could Remember My Name, which was recorded at Wally Heider's. This studio had a very unique sound, and this amp does an amazing job of reproducing the subtleties of their echo chamber which to me points towards precision of the amp to keep each channel tightly in phase with the groove of the album. Anyway, not sure if that's true, but that's how it feels.

 Thanks again Alex! 
	

	
	
		
		

		
		
	


	


_

 

I also find Crosby's IOICRMN to be a disc I go back to all the time as a reference for evaluating equipment. In addition to the room acoustic where it was made, the mix of acoustic, electric and vocals and the separation between them has always been a key evaluation criteria for me.

 While I don't have the diy amp, just a srm-t1s, I also just received 404LEs and am starting to get to know them............holy *.?$ batman, Stax with bass???????


----------



## les_garten

I just posted some Exstata quads I'm selling in the FS forum.

http://www.head-fi.org/forums/f44/fs...8/#post6303731


----------



## Beefy

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I think I might be getting some occasional static in the right channel though. Could be anything along the chain; USB board, DAC, XLR cables, amp, volume control and phones are all new/untested or very recently reconfigured. Will try and chase it down in the morning......_

 

My static issue seems to be the phones themselves. Even after unplugging them from the amp, they give an occasional 'scratchiness' that seems to hang around as long as the bias is still up. It sounds like a rodent rummaging through the roof at night.

 At first I thought it could have been my slovenly week-plus without shaving rubbing on the pleather, but I'm all clean now and can still hear it. Doesn't seem to be cable microphonics either......


----------



## Beefy

Oh, and just some notes on DC offset behaviour. On power up, there is a tiny spike, but it behaves very well.

 On power down, there seems to be a lot more offset - it jumps up to ~30V before drifting down again. Is it because the negative rail with its higher current draw collapses before the other? Or is this unique to my build?


----------



## luvdunhill

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_My static issue seems to be the phones themselves. Even after unplugging them from the amp, they give an occasional 'scratchiness' that seems to hang around as long as the bias is still up. It sounds like a rodent rummaging through the roof at night._

 

That's very strange, I've never encountered anything like that *after* they've been powered off..

 oh, I cannot imagine DC offset of those magnitudes being an issue.... compared to the very large "DC offset" that you're intentionally applying to the drivers


----------



## runeight

Check the bias supply soldering on the board. I wonder if this is intermittent HV to the headphones??

 Yes, the shut-off swing is higher than the turn on. I haven't bothered to think about why, but your theory seems like a good working assumption. And, as Marc says, 30V is trivial to these headphones.


----------



## Beefy

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_That's very strange, I've never encountered anything like that *after* they've been powered off.._

 

 Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Check the bias supply soldering on the board. I wonder if this is intermittent HV to the headphones??_

 

I'll try them again with the SRD7-SB and see if it still happens.

 I doubt it is anything on the board, as both drivers are connected to the same terminal but only one is doing it. Poor wiring is a higher probability, but as Marc says it is really odd that they keep scratching after they have been disconnected.


----------



## Emooze

It wouldn't happen to have something to do with the fact that the drivers are essentially capacitors? Mine do this too after the amp is shut off, headphones unplugged.


----------



## sumo-kun

Regarding scratchyness, I have some SR303s that have never done that since I bought them. However I have bought an SR001 which does do it... kind of. I bought them new not too long ago and I was curious if the ear pieces could be modded with damping so I opened one side up to take a look inside. Of course, there is next to no space in those things  Anyway, I had them completely apart and put them back together the best I could. Afterwards, I noticed weird sounds coming from the earpiece. The reason came from there being an airtight seal from the phones to my ear and the (slight) change in air pressure seemed to make the diaphragm or something else in the earphone wobble ever so slightly and give a crackle/scratch noise. It didn't happen in the other ear. It also occasionally gave a farty type sound. Anyway, it really annoyed me so I took it apart again, checked it, there was some dust so I cleaned it and put it back together again and now it is perfect.
 Moral of the story? Well, maybe its dust but I guess you should first check if you still get weird sounds if you don't move at all. If you still do, get some cotton or something and wedge it between the pad and your head to create an air gap and see if that changes things. I also think it is very unlikely it is something to do with the amp. If the entire headphone is still storing charge, then maybe you could try draining the capacitor so to speak?


----------



## Beefy

Thanks for sharing your experience, sumo-kun 
	

	
	
		
		

		
		
	


	




 I have tried 'discharging' the bias and the effect does seem to lessen (but the humidity in here is so dreadfully low, I can't be sure everything has completely dissipated), so I don't think it is any sort of microphonics. Some advice I got elsewhere it that if dust gets in there I will get a screeching noise. I have been told it is possible that the dust cover is rattling, the stators are separating from the diaphragm, or that a small amount of arcing has left a deposit on the diaphragm.

 Still need to do more testing though, but I will keep at it......


----------



## sergery

Hey TimJo, how are you finding the volume levels with your setup? I am thinking about setting up a vinyl rig and considering various phono stages. I am concerned I will end up with a weak source though. I am not a maths pro, but I calculate u feed the exstata something like 150 mV, which seems low, but I didn't know all of the impedances so this could be way off.


----------



## runeight

Gents, I have PM'd acmemr and given him at least 48 hours to respond beyond the many posts to this thread asking for shipping information. It's hard for me to know what his circumstances might be or why he is not able to communicate. But, he has rights to the last SS board set. 

 Since I need to get this done before too much longer, I'm going to make this board set available to the first person who PMs or emails me. But the rule still applies. No doubling up and no one from the first beta team. 

 I hope that acmemr will forgive me for having to make this change in order to finish out this beta build. 
	

	
	
		
		

		
		
	


	




 As you all know I'll be out of town soon. I will, of course, still have internet access while plying my trade in other places, but I won't be contributing as much. I think there are enough seasoned eXStatA builders on this thread and the amp is sufficiently problem free that new builders should have no trouble getting their amps working.

 Hopefully those of you who DO have eXStatA builds are enjoying them because we don't know when we'll get back to this.


----------



## sumo-kun

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Some advice I got elsewhere it that if dust gets in there I will get a screeching noise._

 

I had that problem too when I put my SR001s back together the first time 
	

	
	
		
		

		
		
	


	



 Scared me pooless the first time turned it on because it was so loud.
 Big piece of dust/hair discovered when I opened it up but that wasn't the source of crackling. Have the phones been opened up in the past? It sounds more like a mechanical problem rather than an electrical one, due to the noise being present even when they are unplugged and probably discharged. As a last resort, maybe you could give them a good shake to dislodge any loose particles or maybe settle down the loose parts?


----------



## HeadphoneAddict

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Gents, I have PM'd acmemr and given him at least 48 hours to respond beyond the many posts to this thread asking for shipping information. It's hard for me to know what his circumstances might be or why he is not able to communicate. But, he has rights to the last SS board set. 

 Since I need to get this done before too much longer, I'm going to make this board set available to the first person who PMs or emails me. But the rule still applies. No doubling up and no one from the first beta team. 

 I hope that acmemr will forgive me for having to make this change in order to finish out this beta build. 
	

	
	
		
		

		
		
	


	




 As you all know I'll be out of town soon. I will, of course, still have internet access while plying my trade in other places, but I won't be contributing as much. I think there are enough seasoned eXStatA builders on this thread and the amp is sufficiently problem free that new builders should have no trouble getting their amps working.

 Hopefully those of you who DO have eXStatA builds are enjoying them because we don't know when we'll get back to this. 
	

	
	
		
		

		
		
	


	


_

 

I would still love to see you make these available to everyone and anyone soon, even as a PCB set and written BOM since kits wont be made available like the CTH had. We need more eXStatA, CTH and EHHA out in people's hands as they are all wonderful amps.


----------



## runeight

Thanks. I'll be back sometime, but things will change. The EHHA is obsolete unless someone puts the 6GM8s into current production. It will be replaced with the EHHA II. The CTH ... well there are things in the works. And the eXSTatA will be back sometime in some form. And then there are the amps that you guys don't know about yet. But I gotta take care of business first.


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Thanks. I'll be back sometime, but things will change. The EHHA is obsolete unless someone puts the 6GM8s into current production. It will be replaced with the EHHA II. The CTH ... well there are things in the works. And the eXSTatA will be back sometime in some form. And then there are the amps that you guys don't know about yet. But I gotta take care of business first. 
	

	
	
		
		

		
		
	


	


_

 

Hmmm. So I was planning to build my Aikido 24V as a HV mod with the other 500VCT trafo I bought. 
	

	
	
		
		

		
		
	


	




 Which means my NOS Amperex Holland 6GM8s have a new home. Booyah! 

 Which way to build them AC? BJT with 2238/968 or MOSFET IRF510/9510?

 I happen to have both in my stash.


----------



## pabbi1

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_I would still love to see you make these available to everyone and anyone soon, even as a PCB set and written BOM since kits wont be made available like the CTH had. We need more eXStatA, CTH and EHHA out in people's hands as they are all wonderful amps._

 

The BOM is available (if read the comment correctly).

 Agreed on more eXStatAs - that's why I built 4, and still have 3, though one is going to my brother over in the sandbox. Even Jarheads know a good amp when they hear it...


----------



## runeight

Actually gents, quite a few exstatas have been built now. The first beta run was 39 total board sets. The second will be 20. This doesn't include the few original proto amps that are circulating around.

 In this respect perhaps we can consider the project successful so far with at least 60 amps in use or about to be built. And, it would seem from the posts, quite a few folks were encouraged to try stats as a result of this amp's availability.


----------



## HeadphoneAddict

I didn't mean the BOM wasn't available, I just meant *PCB + BOM* vs *complete kits* (like the Spruce Canyon CTH kits).


----------



## pabbi1

Kinda what I thought... actually, this is one of the easiest builds to source, even without a pre-populated kit. Matching the FETs is probably the hardest part. As always, the really tough part is the case.


----------



## sergery

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_As always, the really tough part is the case._

 

Yeap. And the more I look at it, the more I realize I am probably going to give the amp a few coats of paint and get a custom front panel from FPE. Never done the latter, how much does something basic run, can someone give me a ballpark idea? I feel like the amp deserves a better home.


----------



## TimJo

Quote:


  Originally Posted by *sergery* /img/forum/go_quote.gif 
_Hey TimJo, how are you finding the volume levels with your setup? I am thinking about setting up a vinyl rig and considering various phono stages. I am concerned I will end up with a weak source though. I am not a maths pro, but I calculate u feed the exstata something like 150 mV, which seems low, but I didn't know all of the impedances so this could be way off._

 

I'm finding the volume level is not a problem. I have yet to get to 12 o'clock on the pot. A bit off topic, but I'm actually finding that you can listen to stats with good response at much lower listening levels as compared to dynamics anyway. 

 150 mV seems low. If you are running the turntable through a pre-amp, you'll be using the tape out. If you run it directly from the phono stage, then that would be dependent on the model, and the cartridge itself.

 My Linn Linto specs for the outputs are:

 Impedance: 100 ohms
 Gain: 64db @ 1kHz
 Max Out: 10.1 v p/p at 1kHz

 My cart spec says 0.3mV @ 3.54 cm/s

 I guess we need to know the input impedance of the eXStatA to get a ballpark for what kind of voltage my preamp is actually producing (at 1kHz & 3.54 cm/s anyway 
	

	
	
		
		

		
			





). 

 Main thing is, I wouldn't worry about it. Vinyl on headphones is really amazing.


----------



## TimJo

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Hopefully those of you who DO have eXStatA builds are enjoying them because we don't know when we'll get back to this. 
	

	
	
		
		

		
		
	


	


_

 

 Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_...it would seem from the posts, quite a few folks were encouraged to try stats as a result of this amp's availability._

 

Well, I can say I am loving mine, and I am certainly in the new stat owners camp. I never considered them before of the cost to get a decent setup, but this changed the equation, and I'm really happy to own one now. As I said in an earlier post, I'm going to be revisiting a lot of records through this setup over the coming months.

 It's kinda feeling like it is a reference amp in it's neutrality. But this also makes it a bit unforgiving, even to recording sessions. Well recorded and well mastered albums are better than I've heard them, but on the other hand, poorly recorded or poorly mastered recordings are now much more obvious. Not a bad thing. It just makes you better appreciate the good stuff.

 Thanks again Alex for devoting so much time to this, especially when it comes to explaining the design, and the design choices, and the tradeoffs. It is a great education at a very affordable price. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_...actually, this is one of the easiest builds to source, even without a pre-populated kit. Matching the FETs is probably the hardest part. As always, the really tough part is the case._

 

Agreed. And as Alex has said, as long as you put the right part in the right place with the right orientation, it's probably going to just work.

 My casework has turned into a bigger project as well. This is too good of an amp to not give it a good case, so I'm taking the time for it. But that isn't stopping me from listening. Just don't let kids or pets wander through if your going to attempt this at home.


----------



## n_maher

Quote:


  Originally Posted by *sergery* /img/forum/go_quote.gif 
_Yeap. And the more I look at it, the more I realize I am probably going to give the amp a few coats of paint and get a custom front panel from FPE. Never done the latter, how much does something basic run, can someone give me a ballpark idea? I feel like the amp deserves a better home._

 

Rough ballpark, FPE panels are going to run $60 to $80 each + shipping both ways. It could be less if you do things like not having the engraving infilled with color and if you use your own material. If you use FPE's it'll probably run you another $10 on each panel. The amp I'm working on right now will use custom front and back panels which I should be ordering in a week or so now that I finally have the chassis.


----------



## Beefy

Quote:


  Originally Posted by *sergery* /img/forum/go_quote.gif 
_Yeap. And the more I look at it, the more I realize I am probably going to give the amp a few coats of paint and get a custom front panel from FPE. Never done the latter, how much does something basic run, can someone give me a ballpark idea? I feel like the amp deserves a better home._

 

Just download the design software, make something, and it tells you how much it costs 
	

	
	
		
		

		
		
	


	




 The prices varies wildly depending on options - for example, my Exstata front panel is going to run at ~$100. But I am going with a large 450*90*6mm panel, infilled engravings, countersunk holes, and tapped holes on the _back_ of the panel which are all very expensive to do. But I could do it for only about $60 if I wanted something much more basic.


----------



## pabbi1

You guys make me feel like such a slacker using wood, so, maybe I can get motivated to do something about that... and no stinking FPE either. Real men gring their own aluminum... even if we can't weld it.


----------



## cfcubed

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_It's kinda feeling like it is a reference amp in it's neutrality. But this also makes it a bit unforgiving, even to recording sessions. Well recorded and well mastered albums are better than I've heard them, but on the other hand, poorly recorded or poorly mastered recordings are now much more obvious. Not a bad thing. It just makes you better appreciate the good stuff._

 

Dude, deja vu for me WRT b22/HF-2s - see OT: Forte comment.
 A bit OT, but would not be without a fun/forgiving combo & a reference combo. Perhaps other stats would get you closer to having both in one.


----------



## luvdunhill

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Just download the design software, make something, and it tells you how much it costs 
	

	
	
		
		

		
		
	


	


_

 

Has anyone tried Cam Expert's new design software?

Front Panel Design and Fabrication Custom Front Panels


----------



## Beefy

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Has anyone tried Cam Expert's new design software?

Front Panel Design and Fabrication Custom Front Panels_

 

For Apple?!? *vomit* 
	

	
	
		
		

		
		
	


	




 *

 Actually, while we're on the subject...... for anyone who has luvdunhill's Stax jack, you will know that you can either glue the jack barrel into the back piece, or 'sandwich' the jack between a cavity in the front panel and the back piece. I am very tempted to try the latter; I think it will give a better fit and a better look.

 But I am unsure of how much of a 'ridge' I will need on the cavity in order to hold the jack in place and have good integrity in the front panel. It looks like the most gap you could get away with around the Stax plug is 1.5mm around the radius and 1.5mm depth. MAYBE 2mm in either dimension if you push it?

 I would be interested to hear other people's thoughts on this......


----------



## studeb

Quote:


  Originally Posted by *sergery* /img/forum/go_quote.gif 
_Hey TimJo, how are you finding the volume levels with your setup? I am thinking about setting up a vinyl rig and considering various phono stages. I am concerned I will end up with a weak source though. I am not a maths pro, but I calculate u feed the exstata something like 150 mV, which seems low, but I didn't know all of the impedances so this could be way off._

 

As a ball park, the phono stage of my Dyna Pas 3 has 40db gain @ 1k Hz. With a 5mV cart that is enough gain to go straight to the eXStatA amp. With a 0.5mV output cart it is not enough. Most phono stages these days seem to have 50+db gain, so unless you go to a lo output MC you are likely okay. If you can decide on the cart then you can figure out how much gain you will need in the phono section.


----------



## luvdunhill

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_It looks like the most gap you could get away with around the Stax plug is 1.5mm around the radius and 1.5mm depth. MAYBE 2mm in either dimension if you push it?

 I would be interested to hear other people's thoughts on this......_

 

Looking at my notes, I was planning 1.5mm radius. I'm not sure why the depth would be limited, so I'll have to think about that. I'll remeasure tonite though.


----------



## TimJo

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_Dude, deja vu for me WRT b22/HF-2s - see OT: Forte comment.
 A bit OT, but would not be without a fun/forgiving combo & a reference combo. Perhaps other stats would get you closer to having both in one._

 

That makes sense you found the same thing with the b22 based on all of the comments i've read about it. One of these days i'll have to get to a meet and have a listen. I'm happy to have both kinds as well, depending on the mood and the record. Tube rolling on the CTH provides plenty of choices which is quite a luxury.

 Right now i'm listening to Van Morrison - Moondance. This is the reissue that was remastered/recut by Steve Hoffmann and Kevin Gray. It is a great example of how a good recording can shine on this amp.


----------



## Beefy

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Looking at my notes, I was planning 1.5mm radius. I'm not sure why the depth would be limited, so I'll have to think about that. I'll remeasure tonite though._

 

I don't have accurate measuring equipment, so I just wasn't sure whether the plug would still clear the ridge. But if the whole Stax plug will fit into the hole if the ridge radius is 1.5mm, then the depth can be whatever I want in order to get a nice looking recess for the jack.

 Oh, and I guess I have no idea whether there are third-party jacks that are a different size/shape that might not fit. I'm still very new to this whole Stax game......


----------



## TimJo

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_As a ball park, the phono stage of my Dyna Pas 3 has 40db gain @ 1k Hz. With a 5mV cart that is enough gain to go straight to the eXStatA amp. With a 0.5mV output cart it is not enough. Most phono stages these days seem to have 50+db gain, so unless you go to a lo output MC you are likely okay. If you can decide on the cart then you can figure out how much gain you will need in the phono section._

 

That's a good reference point then for moving magnet carts, since they tend to run around 5mV, like the Grado's (which are actually moving iron carts).

 My cart is a moving coil, thus the low output at 0.3mV, which is why my phono stage has 64db of gain.


----------



## Sathimas

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_.... And, it would seem from the posts, quite a few folks were encouraged to try stats as a result of this amp's availability._

 

Exectly my case - I always dreamed of stats but always had the price in mind.
 Even a used mid-class stat-amp + phones is very expensive compared to a dynamic setup.

 As I heard of a affordable DIY-stat amp the dream of electrostatic headphones immediately lived up.
 Although my exstata will surely cost more than 400€ I think its a very very good deal.
 The cheapest stax amp costs about 500€ here in Germay - 500€ for a small, ugly and cheap-looking box...

 Of course it could have been built for less money but since this is (hopefully  ) my last headphone-amp ...


----------



## scompton

I've never understood why people don't try vintage Stax. For my wallet, all new Stax except the SR-003 are too expensive. Yet a complete normal bias Lambda setup can easily be had for $250.


----------



## Beefy

Quote:


  Originally Posted by *sergery* /img/forum/go_quote.gif 
_Never done the latter, how much does something basic run, can someone give me a ballpark idea? I feel like the amp deserves a better home._

 

 Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_The prices varies wildly depending on options..._

 

 Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_'sandwich' the jack between a cavity in the front panel and the back piece..._

 

HEH! It will cost me an extra $5.16 to do the cavities for a jack sandwich. I love Front Panel Designer...... 
	

	
	
		
		

		
			





  Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_I've never understood why people don't try vintage Stax. For my wallet, all new Stax except the SR-003 are too expensive. Yet a complete *normal bias Lambda* setup can easily be had for $250._

 

That is the way I went. But I would much rather have new gear, assuming the cost/sound ratio is there. If anything goes wrong with the Lambdas (and something maybe already has), what can I do about it? Fixing a DIY amp myself is easy, fixing a mylar diaphragm...... well, not so much.


----------



## scompton

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_That is the way I went. But I would much rather have new gear, assuming the cost/sound ratio is there. If anything goes wrong with the Lambdas (and something maybe already has), what can I do about it? Fixing a DIY amp myself is easy, fixing a mylar diaphragm...... well, not so much._

 

Yeah, but new has the same problem once it's out of warranty.


----------



## Beefy

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_Yeah, but new has the same problem once it's out of warranty._

 

At least with something newer, you can still buy the spare parts......


----------



## runeight

Still no takes on the last SS board set? If not, that's ok. I'll just set it aside on the workbench until I return.


----------



## sergery

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_That's a good reference point then for moving magnet carts, since they tend to run around 5mV, like the Grado's (which are actually moving iron carts).

 My cart is a moving coil, thus the low output at 0.3mV, which is why my phono stage has 64db of gain._

 

ok, cool. Thanks for your replys. It sounds like you both hit about 500mV, which you are reporting is working well. I will aim for this output level when I am calculating gain of whatever stage I choose to feed exstata.

 Thanks also to those who gave info re. FPE, I may just buy some Aluminum stock and cut/paint/drill myself. I guess I will make a panel design using the software to get an estimate either way.


----------



## manaox2

Got my boards yesterday, they look great. Thanks Alex!


----------



## ericj

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_HEH! It will cost me an extra $5.16 to do the cavities for a jack sandwich. I love Front Panel Designer...... 
	

	
	
		
		

		
		
	


	






 That is the way I went. But I would much rather have new gear, assuming the cost/sound ratio is there. If anything goes wrong with the Lambdas (and something maybe already has), what can I do about it? Fixing a DIY amp myself is easy, fixing a mylar diaphragm...... well, not so much._

 

Unusual for something to go wrong with lambdas. 

 There are legions of damaged SR-X, SR-5 and SR-Gamma out there, but that's a different driver design.


----------



## sumo-kun

Regarding stax plug sizes, the older and lower end cables have the usual round plug, where the high end cables like on the SR404 LE have wider wire and they stick out a bit from the sides of the plug making it a kind of old school flying saucer type shape. Those sticky out bits might get in the way of your jack recess if you ever plan on getting phones with the fat cable.


----------



## runeight

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Got my boards yesterday, they look great. Thanks Alex!_

 

Good. Now build.


----------



## Beefy

Quote:


  Originally Posted by *sumo-kun* /img/forum/go_quote.gif 
_Regarding stax plug sizes, the older and lower end cables have the usual round plug, where the high end cables like on the SR404 LE have wider wire and they stick out a bit from the sides of the plug making it a kind of old school flying saucer type shape. Those sticky out bits might get in the way of your jack recess if you ever plan on getting phones with the fat cable._

 

Hmmmm, this is good to know. Thanks again


----------



## TimJo

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Oh, and just some notes on DC offset behaviour. On power up, there is a tiny spike, but it behaves very well.

 On power down, there seems to be a lot more offset - it jumps up to ~30V before drifting down again_

 

 Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_oh, I cannot imagine DC offset of those magnitudes being an issue.... compared to the very large "DC offset" that you're intentionally applying to the drivers 
	

	
	
		
		

		
		
	


	


_

 

So does this mean that with this amp it is safe to always leave your stats plugged in, and you can simply turn the amp on and off without worries?


----------



## Beefy

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_So does this mean that with this amp it is safe to always leave your stats plugged in, and you can simply turn the amp on and off without worries?_

 

Yeah, it should be fine. I wasn't ever actually concerned about the offset, just reporting my findings


----------



## TimJo

Being that these are my first stats, I wasn't really sure if it was okay. 
	

	
	
		
		

		
			





 I always plug my dynamic phones in once the amp is warmed up, and then unplug them before power off, even if the board has a protection circuit on it.


----------



## Beefy

Nothing is stopping you doing that, but nothing will blow up if you don't


----------



## Beefy

Quote:


  Originally Posted by *sumo-kun* /img/forum/go_quote.gif 
_Regarding stax plug sizes, the older and lower end cables have the usual round plug, where the high end cables like on the SR404 LE have wider wire and they stick out a bit from the sides of the plug making it a kind of old school flying saucer type shape. Those sticky out bits might get in the way of your jack recess if you ever plan on getting phones with the fat cable._

 

Somebody was able to help me dimension the 404LE plug. It comes out a little something like this:






 So if you are 'sandwiching' luvdunhill's Stax jack, you need a hole at least 18.5mm in diameter, and a 'ridge' no more than 3mm deep in order to fully insert the biggest Stax plugs.

 For the balance between strength and clearance, I plan to use a 19mm hole (3.2mm less than the 22.2mm jack, equivalent to 1.6mm all around), and a 2-2.5mm thick ridge.


----------



## TimJo

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Nothing is stopping you doing that, but nothing will blow up if you don't 
	

	
	
		
		

		
		
	


	


_

 

Okay, good to know. With the 5 pin connector, my preference to to leave them plugged in all the time anyway. I guess I just didn't want to blow up my brand new stats. 

 As a side note: I'm really loving this amp. I continue to be amazed with the clarity of the bass. The other thing I notice is that on vocals, the clarity has improved because of the absence of sibilance. I guess I need to do some kind of a/b test with a given vocal and see if this is true, but I am hearing details in the vocals I haven't noticed before, and I'm thinking it's because nothing is getting smeared.


----------



## pabbi1

There are bunches of bits that this amp reveals - I rather think of them as inside jokes by the musicians and producers (especially Zappa), where he knows, as it were, what was buried in a mix that usually only folks with studio playback reproduction would hear, and that it might well disturb the .001% of listeners that might catch it just on the corner of their ear.

 Now the most interesting bits are those engineered to sound a certain, familiar way on lo-fi or radio production, with more interest in mid-upper fi, then just outright disturbing on the highest fi. In Sheik Yerbouti (iirc, on 'I'm So Cute'), for instance, there are some really sharp inserted electrical snaps included that just sound like percussion emphasis elsewhere (no, this is not a clip - I can get that on almost all the Tool CDs). 

 Driving me nuts to see what other people think about this amp, and, how to improve it (ok, other than my Tool issue).


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_There are bunches of bits that this amp reveals - I rather think of them as inside jokes by the musicians and producers (especially Zappa), where he knows, as it were, what was buried in a mix that usually only folks with studio playback reproduction would hear, and that it might well disturb the .001% of listeners that might catch it just on the corner of their ear.

 Now the most interesting bits are those engineered to sound a certain, familiar way on lo-fi or radio production, with more interest in mid-upper fi, then just outright disturbing on the highest fi. In Sheik Yerbouti (iirc, on 'I'm So Cute'), for instance, there are some really sharp inserted electrical snaps included that just sound like percussion emphasis elsewhere (no, this is not a clip - I can get that on almost all the Tool CDs). 

 Driving me nuts to see what other people think about this amp, and, how to improve it (ok, other than my Tool issue)._

 

Perhaps the cure for your clipping Tool CDs is this?
Amazon.com: tool vinyl: Music

 That is assuming the vinyl was mastered differently with less compression. 

 I know that Red Hot Chili Peppers and most Foo Fighters sound better and are specifically remastered for the vinyl editions. Unfortunately I haven't heard if the new Foo Fighter's Greatest Hits album sounds better on vinyl and I'm not willing to risk it for $30.


----------



## pabbi1

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Perhaps the cure for your clipping Tool CDs is this?
Amazon.com: tool vinyl: Music

 That is assuming the vinyl was mastered differently with less compression. 

 I know that Red Hot Chili Peppers and most Foo Fighters sound better and are specifically remastered for the vinyl editions. Unfortunately I haven't heard if the new Foo Fighter's Greatest Hits album sounds better on vinyl and I'm not willing to risk it for $30._

 


 Oy! Satan get thee hence... Vinyl mastering might have merit, but no needle drops for me, thanks. My goal is for simplification going forward... 

 Maybe Vulcan will cure all my woes for Tool (geez, just that one group), if my psu(s) will hold. And, I've never heard 'Aenima' on the BH - but no chance of paying $110 for the vinyl. Or any vinyl, ever again. Certified vinyl-phobe.

 Now, that does raise the question - is Vpp the end all discussion regarding clipping? Would swinging 1400Vpp vs the current 1000Vpp cure the issue?


----------



## luvdunhill

Theoretically, clipping could take place in three places in your chain.

 The original track (BMF's suggestion), your CD player, your amp. I think it's worth investigating them in that order


----------



## runeight

Well, it could be that you need another 400V. You know anyone up there with a scope and a 10x probe?

 Or you could build a +/- 350V PS for the exstata and swing a few hundred more volts, albeit with somewhat higher THD on the high dynamic peaks.


----------



## pabbi1

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Well, it could be that you need another 400V. You know anyone up there with a scope and a 10x probe?

 Or you could build a +/- 350V PS for the exstata and swing a few hundred more volts, albeit with somewhat higher THD on the high dynamic peaks. 
	

	
	
		
		

		
		
	


	


_

 

Interestingly enough, I do have a 350v+ adjustable supply, but it doesn't have bias built in, though I do have a seperate bias only board... been down this road already. Maybe it will even work, though hasn't to date, to the best of my knowledge.

 I am first going to see if it is the source next week when the BH is back - if it clips there (at theoretical maximum of 1800Vpp), it's the source - player or material. I'll also be checking the discs first thing against some far better sources and the BHSE at the DFW meet - we'll see then what is what wrt source.

 Maybe Marc has the right probe, and will drag up a scope? If not, maybe Pete will still allow us to hook this up on his test rig.


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Well, it could be that you need another 400V. You know anyone up there with a scope and a 10x probe?

 Or you could build a +/- 350V PS for the exstata and swing a few hundred more volts, albeit with somewhat higher THD on the high dynamic peaks. 
	

	
	
		
		

		
		
	


	


_

 

I still don't think a 10x probe is safe. Let's say 1000 Vpp, that's 354 Vrms. In 10x mode, my Tek probe will support 300V CAT II for example.

 I did have a suggestion a few pages back though that got lost in Beefy's success


----------



## runeight

Ah, I see what's on your mind. Even in diff mode it won't matter. I guess I'll back track a few pages.


----------



## Beefy

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_I did have a suggestion a few pages back though that got lost in Beefy's success 
	

	
	
		
		

		
		
	


	


_

 

Ooops, I'll ease up on the attention whoring, shall I?


----------



## runeight

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_I still don't think a 10x probe is safe. Let's say 1000 Vpp, that's 354 Vrms. In 10x mode, my Tek probe will support 300V CAT II for example.

 I did have a suggestion a few pages back though that got lost in Beefy's success 
	

	
	
		
		

		
		
	


	


_

 

I don't see why a series pair of caps wouldn't work for the measurement that Al needs. I might use 47p in series with 4700p to provide a more typical load. The small cap will need to stand off most of the voltage and needs to be 1200V.


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I don't see why a series pair of caps wouldn't work for the measurement that Al needs. I might use 47p in series with 4700p to provide a more typical load. The small cap will need to stand off most of the voltage and needs to be 1200V._

 

Well, I was thinking the divider would be nice, as it would scale the voltage. I could maybe tell my 'scope I was using a (10x, 100x, 1000x) whatever it turned out to be (there's an option for this) and it would scale the voltage and display it properly. Granted, that's aesthetic. But, as you said, I'd have to calculate the proper load after the divider, I'm not sure how to do that, as doesn't the capacitance of the probe itself come into play here (or would that be frequency dependent?)? So, would this measurement be from the junction of the two 47pF + 4700pF capacitors referenced to ground, and either side of the two "load" capacitors would be connected to + and - output?


----------



## runeight

The way I see it is that you will connect the O/P of the amp to the two outside leads of the capacitor pair. Then take the signal from across the 4700p cap using two 1X probes and the scope in differential mode for its two inputs. Since the probe capacitance is generally small and will be in parallel with the 4700p cap its effect should be negligible and calculable.


----------



## runeight

But, now that I think more this won't solve the standoff problem.


----------



## runeight

You know, we are making this harder than it really is because this is a differential amp.

 The rails on this amp are +/-300V. Neither ouput can go past its rails so if you connect two probes from the scope in differential mode neither probe will see more than 300V with respect to ground. There could be 600V between the probes but then there is twice the insulation between them.


----------



## sumo-kun

So I got home from work just now and the boards arrived! Yippee! They look as stunning as everyone says 
	

	
	
		
		

		
			




 Now I just got to scrounge together the parts and put it together 
	

	
	
		
		

		
		
	


	




 Just a quick question. Regarding transformers, I will probably need to get a custom one made since there seem to be no off the shelf and reasonably priced ones around here. I looked around and I found that an EI trans will cost only a little less than an R-core and an EI orient core is about the same or a tiny bit more. Also there are R-core toroids available. Not sure how much they are though. They're made by the same company that invented R-core transformers. So with the minimal price difference between all these types, which would be the "best" one? My case will be as compact as I can manage so I'm leaning towards R-cores right now... Any suggestions?


----------



## Beefy

sumo-kun - are you doing the hybrid or solid state? I got a custom toroid for my solid state build and it works a treat.


----------



## paxeaxe23

Hi! I am considering building from this design, sounds really good. However I am not clear as to which STAX I could use with this. I own a pair of SR-5's and these are the so called normal bias which as far as I can see are 230v . Is it possible to adjust the Amplifier to work with these Headphones?


----------



## scompton

There can be outputs for both normal and pro biases


----------



## paxeaxe23

Yes, I have been spending the last hour reading the whole thread and managed to work that out. Nice to have something like that confirmed though, its a lot of voltage to be playing with!

 Thankyou


----------



## BoilermakerFan

Quote:


  Originally Posted by *sumo-kun* /img/forum/go_quote.gif 
_So I got home from work just now and the boards arrived! Yippee! They look as stunning as everyone says 
	

	
	
		
		

		
		
	


	



 Now I just got to scrounge together the parts and put it together 
	

	
	
		
		

		
		
	


	




 Just a quick question. Regarding transformers, I will probably need to get a custom one made since there seem to be no off the shelf and reasonably priced ones around here. I looked around and I found that an EI trans will cost only a little less than an R-core and an EI orient core is about the same or a tiny bit more. Also there are R-core toroids available. Not sure how much they are though. They're made by the same company that invented R-core transformers. So with the minimal price difference between all these types, which would be the "best" one? My case will be as compact as I can manage so I'm leaning towards R-cores right now... Any suggestions?
	

	
	
		
		

		
		
	


	


_

 

As it was explained to me by a custom E-I transformer manufacture, the R-Cores are unique transformers in respect that they have a compact, flat profile like a toroid, but the they have the better noise rejection properties of a E-I type core. If they were not so expensive to ship here from HK, I would have used R-cores in my builds. 

 I have custom E-Is from a US company for my eXStatas and I'm ordering custom shielded and potted toroids for another 3 projects from the same vendor Beefy ordered his from.


----------



## macm75

I'm sure it was discussed or thought of during the design of the hybrid pcb, but just in case, for next project consider designing so the tubes mount on the opposite side of the pcb. Shame to see tubes inside boxes. BUT I do realize I can mount the tubes on "chassis" sockets, mount the pcb's upside down to the top plate, and solder wire from sockets to pcb.
 Top plate with power transformer centered on back side and a line of 6S4A's in the front would be nice presentation. Think about it Hybriders.


----------



## pabbi1

Boring, Sydney... boring.






 This was prototyped, but could not get to the biasing pots. The boards are small to minimize the signal path, but this is how I am going on a new experimental build. Let's just say I have a burning desire.


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_You know, we are making this harder than it really is because this is a differential amp_

 






 ...


----------



## macm75

Would you use this resistor? It's R1, 1M, on the amp board. It still reads 1M.
 Maybe just put some heat shrink around it?


----------



## macm75

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_new experimental build_

 

Nice - top plate above the socket plate - no screws visible


----------



## les_garten

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_Would you use this resistor? It's R1, 1M, on the amp board. It still reads 1M.
 Maybe just put some heat shrink around it?
_

 

I hate trick questions like this...


----------



## tomytank

My hybrid boards turned up Thursday, so far I've completed the resistors, diodes and small signal transistors. I'm going carefully and methodically through the build.

 Like sumo-kun says the boards are stunning, much smaller in person than I thought they would be. As I get time, I'll keep working.


----------



## paxeaxe23

I'm looking forward to building my SS amp and have ordered the parts from mouser and sent a PM to runeight about getting the board/s. In the meantime I have a question about the power supply. So far I haven't found much information on the PSU but I live in Germany where we have 240v supply. Has anyone got a schematics and/or board for use with this amplifier. Thanks


----------



## macm75

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_I hate trick questions like this..._

 

I got the point. Actually, I appreciate it.


----------



## sumo-kun

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_sumo-kun - are you doing the hybrid or solid state? I got a custom toroid for my solid state build and it works a treat._

 

I'm doing the hybrid build. Looks like the R-core looks like a good way to go since small and the minimal flux leakage are good things for my planned small case. I'm curious about the R-core toroids though... sounds like it would be the ultimate transformer haha.


----------



## Beefy

Quote:


  Originally Posted by *sumo-kun* /img/forum/go_quote.gif 
_I'm doing the hybrid build. Looks like the R-core looks like a good way to go since small and the minimal flux leakage are good things for my planned small case._

 

Probably. The single toroid I used makes more sense when you don't have the heater windings.

 *

 After listening to my Lambda with my SRD7-SB, my current theory for the 'scratchiness' I am getting is that the noise is coming from the glue on the pads. Sometimes when I move my head slightly , the glue sticks, then separates. I suspect that the reason I wasn't hearing it after the bias was shorted is that I was holding so incredibly still to be able to hear any slight noise.

 Though I still need to listen some more with my Exstata to confirm that this is the case, and not something wrong with my bias circuit/wiring. Unfortunately, it in is pieces right now as I will be drilling the bottom of my case today......


----------



## BoilermakerFan

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_I got the point. Actually, I appreciate it._

 

Yep, when in doubt, throw it out. A $0.50 resistor could have taken out 100X it's cost in other parts or more.


----------



## BoilermakerFan

Quote:


  Originally Posted by *sumo-kun* /img/forum/go_quote.gif 
_I'm doing the hybrid build. Looks like the R-core looks like a good way to go since small and the minimal flux leakage are good things for my planned small case. I'm curious about the R-core toroids though... sounds like it would be the ultimate transformer haha._

 

They would be if they were easy to get world-wide and in higher VAs. Custom multi-windings in 200-700VA size offer sure would be handy!


----------



## pabbi1

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_Would you use this resistor? It's R1, 1M, on the amp board. It still reads 1M.
 Maybe just put some heat shrink around it?





_

 

Those who forget the PAST are doomed to repeat it.


----------



## macm75

So for C6 on the PS, .1uf - 1kV, I bought the 27mm lead spaced cap instead of the 22mm spaced. Although it will not fit in the spot, I'd like to drill into the board, put it parallel with R23, between the corner hole and Test Point 3. 
 I just drilled thru a couple junk pcb's and it went thru with ease. Not sure if the eXStata board is the same material as my junk boards and wish to take precautionary measures... is it OK drilling into these boards?


----------



## digger945

I've got a board here in hand, and while it doesn't appear to have a layer in the middle, that would best be answered by Alex. 
 Looks like the inboard pad of C6 has a trace beneath the mask(on top, connected to 0V), and this is pretty close to another trace on the other side of the board. 
 The outboard pad for C6 is indeed connected to other traces on the bottom of the board(ultimately ends up connected to "High Bias"). If you drilled one hole about 5mm off center you would have to wire it back to the pad anyway, so why not try to bend each lead of the cap inward about 2.5mm and see if you can make it fit?

 What kinda cap, Wima?


----------



## tomytank

I had the same problem with C6 on the PSU and bought the 27mm lead spacing Wima and had to do what Digger945 describes, I bent the legs slight inwards and then downwards. It does fit. Reaches just to the edge of the diode d3 on one side and has a couple of mil on the R23 side.


----------



## macm75

It's a Wima. The cap is also a little wider than the C6 ink outline on the board. I'd have to press fit the cap between the hi bias diodes and the 'lytic. 
 But thanks, you're right! I can mount it over the diodes, extend the leads a little, and, for extra security, tie wrap the the cap to the 'lytic.
 All is well but I'll still check with Alex on the drilling.

 Edit: Thanks tomytank!


----------



## runeight

Drilling???? I hate these trick questions.


----------



## macm75

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Drilling???? I hate these trick questions. 
	

	
	
		
		

		
		
	


	


_

 

Tough Crowd


----------



## BoilermakerFan

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_Tough Crowd 
	

	
	
		
		

		
		
	


	


_

 

They're just trying to help because you have one of about 60 sets of boards, and in reality one of 35 or sets of hybrid boards. New boards are not going to be available again for some undetermined length of time. So, if you toast a board, you're out of luck unless you built one channel P2P on proto board or buy a complete populated prototype amp from from the builders on the Alpha team...


----------



## tomytank

I managed to get my PS running yesterday 
	

	
	
		
		

		
			





. Came up exactly like Alex said. It was a bit worrying at first, since on power on, only one of the LEDs was on, but as soon as I dialled P1 to 360 and P2 to 410, the second LED came on. 

 Everything seems fine so far. Measurements to follow later.


----------



## tomytank

Left it running for about 30-40 mins didn't seem to fluctuate much at all.

 T1 to Gnd : 348
 T3 to Gnd : 345
 -ve rail: 300
 +ve rail: 298


----------



## paxeaxe23

Hi!

 Can anyone tell me the pinout for the STAX 230V (normal bias).

 There is nice picture for the Pro in this thread, but none for the normal

 Thanks

 Frank


----------



## Beefy

The extra pin (centre) is a bias pin. Everything else is the same.

http://wiki.faust3d.com/wiki//index....Connectors.jpg


----------



## Currawong

My boards arrived today, thanks Alex. I found Beefy's Mouser project too, so I'll double-check that, get everything and start building and case-hunting shortly.


----------



## paxeaxe23

Great! Thanks a lot. I spent half the night googling on that one

 Cheers!
	

	
	
		
		

		
		
	


	





  Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_The extra pin (centre) is a bias pin. Everything else is the same.

Image:Stax Headphone Cable Connectors.jpg - Wikiphonia_


----------



## Beefy

Quote:


  Originally Posted by *Currawong* /img/forum/go_quote.gif 
_My boards arrived today, thanks Alex. I found Beefy's Mouser project too, so I'll double-check that, get everything and start building and case-hunting shortly._

 

That all worked out well too, but I would still make some changes. RN55D 1kohm back in stock, extra BC550 to allow for matching. Let me see if I have some time later today......


----------



## Beefy

I've double-checked my Mouser projects, and they are good to go for the power supply and solid state amps. Can't help with the tube amp, unfortunately 
	

	
	
		
		

		
		
	


	




 Some items are currently OOS...... insulating pads for double-mount devices can be solved with extra whole kits, and the big 1kV cap for the high-bias should be in stock in a couple of days. The only real problem item is the load resistors, which are currently out of stock until May 
	

	
	
		
		

		
		
	


	




 So for anybody who wants them and missed the previous post, here they are:
Exstata PS (maxed/CRD version)
Exstata SS

 [EDIT] Oh, just one more thing I should point out. There are extra 91 and 100V zeners to allow for 282/291/300V zener strings in the PS. This was because I wasn't 100% sure about how my custom transformer would work out, and wanted to be able to tweak up or down as necessary. Thankfully, the transformer and default 291V was perfect for me, but they are really handy spares to have.


----------



## bidoux

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_
 So for anybody who wants them and missed the previous post, here they are:
Exstata PS (maxed/CRD version)
Exstata SS_

 

I'm sure it will help for many of us. Is there absolutely everything excet casing, connectors and the transformers ? (of course I'll double check if use it)


----------



## Beefy

Yeah, it is everything that goes in the PCBs.

 I'm also more than happy to supply my options for audio and power connectors, standoffs, terminal blocks, and components for a ground breaker. They aren't in a Mouser project though, so I can't link the lot easily like I did for the PS and SS amp.


----------



## runeight

Gents, the last SS board set has been shipped. On this round all boards went to new builders (so far as I can tell) giving quite a few of you a chance to build this amp.

 I'm going to drift away for a while now, but there is plenty of build expertise on this thread for anyone who might need help. Besides, if you build it right it will work (or something like that).


----------



## HeadphoneAddict

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Gents, the last SS board set has been shipped. On this round all boards went to new builders (so far as I can tell) giving quite a few of you a chance to build this amp.

 I'm going to drift away for a while now, but there is plenty of build expertise on this thread for anyone who might need help. Besides, if you build it right it will work (or something like that). 
	

	
	
		
		

		
		
	


	


_

 

You will make these PCB available for others in the future right?


----------



## minivan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Oh, just one more thing I should point out. There are extra 91 and 100V zeners to allow for 282/291/300V zener strings in the PS. This was because I wasn't 100% sure about how my custom transformer would work out, and wanted to be able to tweak up or down as necessary. Thankfully, the transformer and default 291V was perfect for me, but they are really handy spares to have._

 

x2 with that, i made the mistake of not ordering some extra zeners and now i have to suffer the consequences of 4x 100v 1 w zeners short.

 i will be most grateful if anyone can help me out with their spares 4x100v 1w zeners, or order some extra 100v 1w zeners when they are making order from mousers. 

 i had my hybrid amp ,psu assembled and cased up a age ago by still short of those 100v zeners to power up lol

 one member suppose to send me with those spares zeners but he never get back to me, i assume he must be very busy with work or preoccupied with something else in life. so i dont want to trouble him again


----------



## macm75

Quote:


  Originally Posted by *minivan* /img/forum/go_quote.gif 
_x2 with that, i made the mistake of not ordering some extra zeners and now i have to suffer the consequences of 4x 100v 1 w zeners short.

 i will be most grateful if anyone can help me out with their spares 4x100v 1w zeners, or order some extra 100v 1w zeners when they are making order from mousers. _

 

Why from Mouser? Ebay, local electronics store, service shop, etc. Call around - 100V zeners can't be that hard to find.


----------



## Currawong

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I've double-checked my Mouser projects, and they are good to go for the power supply and solid state amps. Can't help with the tube amp, unfortunately 
	

	
	
		
		

		
		
	


	




 Some items are currently OOS...... insulating pads for double-mount devices can be solved with extra whole kits, and the big 1kV cap for the high-bias should be in stock in a couple of days. The only real problem item is the load resistors, which are currently out of stock until May 
	

	
	
		
		

		
		
	


	




 So for anybody who wants them and missed the previous post, here they are:
Exstata PS (maxed/CRD version)
Exstata SS

 [EDIT] Oh, just one more thing I should point out. There are extra 91 and 100V zeners to allow for 282/291/300V zener strings in the PS. This was because I wasn't 100% sure about how my custom transformer would work out, and wanted to be able to tweak up or down as necessary. Thankfully, the transformer and default 291V was perfect for me, but they are really handy spares to have._

 

Thanks for setting those up again. I have to go into the city to get some parts tomorrow anyway, so I'll see if I can't find suitable substitutes for the OOS parts, a case and other bits and pieces.


----------



## tomytank

Quote:


  Originally Posted by *paxeaxe23* /img/forum/go_quote.gif 
_ So far I haven't found much information on the PSU but I live in Germany where we have 240v supply._

 

@paxeaxe23

 You have different options for a transformer. I live across the border from you and we have 230VAC. I'm successfully using the 369JX from Hammond. Alternatively you can look up the R-Cores on ebay. Although with import duty and postage they cost almost the same as the 369JX. Or you could have it custom built.

 If you haven't done your mouser order yet, they have one 369JX in stock. Also, if you need a matched quad of J271, pm me.


----------



## manaox2

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I've double-checked my Mouser projects, and they are good to go for the power supply and solid state amps. Can't help with the tube amp, unfortunately 
	

	
	
		
		

		
			





 Some items are currently OOS...... insulating pads for double-mount devices can be solved with extra whole kits, and the big 1kV cap for the high-bias should be in stock in a couple of days. The only real problem item is the load resistors, which are currently out of stock until May 
	

	
	
		
		

		
		
	


	




 So for anybody who wants them and missed the previous post, here they are:
Exstata PS (maxed/CRD version)
Exstata SS

 [EDIT] Oh, just one more thing I should point out. There are extra 91 and 100V zeners to allow for 282/291/300V zener strings in the PS. This was because I wasn't 100% sure about how my custom transformer would work out, and wanted to be able to tweak up or down as necessary. Thankfully, the transformer and default 291V was perfect for me, but they are really handy spares to have._

 

Your the man Beefy, thanks!


----------



## ChrisX

My Boards arrived today. 
	

	
	
		
		

		
		
	


	




 Great Work! Thanks Alex!

 Most of the parts are already here, but I won't have much time in the next weeks. I think I can start building in February, until then I should be able to get the remaining stuff.


----------



## bidoux

Quote:


  Originally Posted by *paxeaxe23* /img/forum/go_quote.gif 
_ In the meantime I have a question about the power supply. So far I haven't found much information on the PSU but I live in Germany where we have 240v supply._

 

I live in France and we have around 220V but I thought the transformer for the solid state version was dual primairy (correct me if I'm wrong).
 You could do the exact same build and add a 220 --> 130 transformer but it is a lot of transformers...


----------



## Sathimas

My boards also arrived today - they look really great.
 Also 2 sets of tubes arrived today.

 All the other parts are still missing but I can not start building before february anyway.

 I am also a bit confused about the transformer ...
 Shematic on the website says 240V input on the PS, but the boards are labeled 250V.


----------



## paxeaxe23

I'm searching for a suitable POT. and see elswhere in this thread that people are using an ALPS 4 gang model. 

 Is this any good to me?

ALPS Quad Potentiometer RK27114 Pot RK27 10K o 5K Audio bei eBay.de: Audio (endet 27.01.10 15:35:49 MEZ)

 Thanks


----------



## pabbi1

I have used basically that one (except motorized), but *think* it was 50k. It is certainly acceptable, though there are better options, at a price.


----------



## Sathimas

pabbi1, what other options would you propose?


----------



## TimJo

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_I am also a bit confused about the transformer ...
 Shematic on the website says 240V input on the PS, but the boards are labeled 250V._

 

You must be referring to the wiring diagram, which does show a 240-0-240 transformer. I think this is because in the prototype phase of the project, it was originally 240, but it should be 250. 

 The actual power supply schematic is correct, which shows 250-0-250.

 If you are building a hybrid, and you use a 300 series Hammond transformer, they have wires to allow inputs of 220vac or 240vac. I used the 369JX, and a 300v zener string in my power supply. It works perfectly.


----------



## Sathimas

I have ordered a custom transformer with 230V input and 250V output - so thats ok now.


----------



## BoilermakerFan

Actually the 480VCT transformer is ideal with the 291V standard Zener. You will need the 300V Zener string with a 500VCT transformer.


----------



## pabbi1

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_pabbi1, what other options would you propose?_

 

In dual pots, TKD 2p2511 or Noble, or steppers, the usual Asian origin, or pricey as in Goldpoint (who also have quad).

 In quad, I have used DACT (~$175 from Headamp once upon a time), the Asian steppers, or the 41 step from Acoustic-Dimension, high-end audio and components for tube audio , which I have in the current eXStatA, though did NOT have to pay the price listed (gracias, Marc).

 Attenuation and I have a rather sordid past, as there has been a different selection on almost every project, and as they say, water finds it's own level.


----------



## les_garten

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_In dual pots, TKD 2p2511 or Noble, or steppers, the usual Asian origin, or pricey as in Goldpoint (who also have quad).

 In quad, I have used DACT (~$175 from Headamp once upon a time), the Asian steppers, or the 41 step from Acoustic-Dimension, high-end audio and components for tube audio , which I have in the current eXStatA, though did NOT have to pay the price listed (gracias, Marc).

 Attenuation and I have a rather sordid past, as there has been a different selection on almost every project, and as they say, water finds it's own level._

 

Attenuator Fetishes...

 They only worsen if not immediately addressed...


----------



## macm75

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_Attenuator Fetishes...
 They only worsen if not immediately addressed..._

 

Other interesting options...
DIY Lightspeed Passive Attenuator (audio optocouplers)
intact audio


----------



## digger945

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_intact audio_

 

I would really like to try this.


----------



## Sathimas

I thought you where speaking of options in the same price range 


 Even the quad alps pot is already quite expensive for me (will be the most expensive single part in my amp 
	

	
	
		
		

		
			





 )

 ______________

 Something different now:
 I just got a call from the company how did the transformer for me and it turned
 out that there was a misunderstanding and the transformer I ordered only has
 one secondary 250V output - not as needed two. But it has the 6,3V winding and 40VA ...

 So - what should I do now ...
 I could simply add a second transformer mit only one 250V output.
 What VA-rating should that second one have?

 The other option would be to simply order a new one with all
 correct values and sell the "wrong" one.

 What would be better - technically?


----------



## macm75

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_I thought you where speaking of options in the same price range 
 Even the quad alps pot is already quite expensive for me (will be the most expensive single part in my amp 
	

	
	
		
		

		
		
	


	




 )_

 

I posted this before...
DUAL MONO VOLUME
http://cgi.ebay.com/_W0QQitemZ320456036248
 It took me 2 nights to build. Recommended if you like to solder (just under 200 points). Not sure how it sounds yet but I expect better than a pot.


----------



## macm75

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_Something different now:
 I just got a call from the company how did the transformer for me and it turned
 out that there was a misunderstanding and the transformer I ordered only has
 one secondary 250V output - not as needed two. But it has the 6,3V winding and 40VA ...

 So - what should I do now ...
 I could simply add a second transformer mit only one 250V output.
 What VA-rating should that second one have?

 The other option would be to simply order a new one with all
 correct values and sell the "wrong" one.

 What would be better - technically?_

 

You can buy a dupe of the one you bought and wire like this (ignore the not used windings on the secondaries). Wire 2 6S4A heaters off of each transformer. Work with the winder for total assurance.
eXStatA with Triads
 or ask the winder to build one like the Hammond 270AX (I would ask for a 4A capable 6.3 winding for cooler operation).
 I think the decision is just a matter of cost and space.


----------



## BoilermakerFan

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_I thought you where speaking of options in the same price range 


 Even the quad alps pot is already quite expensive for me (will be the most expensive single part in my amp 
	

	
	
		
		

		
		
	


	




 )

 ______________

 Something different now:
 I just got a call from the company how did the transformer for me and it turned
 out that there was a misunderstanding and the transformer I ordered only has
 one secondary 250V output - not as needed two. But it has the 6,3V winding and 40VA ...

 So - what should I do now ...
 I could simply add a second transformer mit only one 250V output.
 What VA-rating should that second one have?

 The other option would be to simply order a new one with all
 correct values and sell the "wrong" one.

 What would be better - technically?_

 

A simple shunted pot should be fine. A 50K pot with two 47K resistors for each leg. Simple, and cheap.

 They won't hold off shipment and send the correct transformer? Or did you not order it as (2) 250V or 500VCT? If you ordered it as (2) 250V secondaries, they should replace it with the correct transformer.

 You should be able to sell the incorrect one as it is a nice transformer for a HV Aikido preamp build. The 250V will rectify to 354V just like the eXStata, and regulate down to 350V-351V and each tube in an Aikido would see 175V which is a pretty nice spot for 6922 series tubes and others. Heck, you could order an Aikido preamp kit and use it in your system if you have a speaker system. The gain would be too high for an eXStata, even on SE inputs. That's actually what I'm doing with a 500VCT custom, except I have to use FW rectification since mine is a CT transformer.


----------



## pabbi1

Taking a current version and proto to the DFW meet today for impressions and comparisons, against the following:

 BHSE
 BH
 KGSS (max version)
 SRM T1 (the original comparitive target)
 Stax 313
 Vulcan - BH derivative (BIG maybe)

 So, anyone esle have impressions, or updates? Jeez, I feel so isolated.


----------



## Beefy

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_So, anyone esle have impressions, or updates? Jeez, I feel so isolated._

 

I'm trying, honest! 
	

	
	
		
		

		
		
	


	




 I drilled my base plate last weekend, and everything is mounted on it and wired up. Still waiting for some dimensions and info before I place my FPE order. I can't do any serious listening until I get those panels, because I just don't have anywhere to sit and listen to an open chassis 
	

	
	
		
		

		
		
	


	




 I also want to do some work on my Lambdas...... cable, pads, foam etc. before they are ready for prime time listening.


----------



## TimJo

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Taking a current version and proto to the DFW meet today for impressions and comparisons, against the following:

 BHSE
 BH
 KGSS (max version)
 SRM T1 (the original comparitive target)
 Stax 313
 Vulcan - BH derivative (BIG maybe)

 So, anyone esle have impressions, or updates? Jeez, I feel so isolated._

 

I continue to listen to mine every day and I'm loving it. I'm quite happy with the combo of the SR-404LE and the eXStatA. Listening to the bass continues to blow me away. I feel lucky to own one of these. 
	

	
	
		
		

		
		
	


	




 Thus far I've been using the GE grey plate quad I got from you, but I also have a set of RCA's with black plates. I think I'm going to swap them out and see if I can tell a difference, now that I'm pretty familiar with the sound. I'm a little skeptical that I'm going to notice a difference, based on the circuit, but why not try since I have them.

 It'll be interesting to see what folks think at the meet...


----------



## macm75

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Thus far I've been using the GE grey plate quad I got from you, but I also have a set of RCA's with black plates. I think I'm going to swap them out and see if I can tell a difference, now that I'm pretty familiar with the sound. I'm a little skeptical that I'm going to notice a difference, based on the circuit, but why not try since I have them._

 

Yes, Please do and report back!!


----------



## les_garten

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_Yes, Please do and report back!! 
	

	
	
		
		

		
		
	


	


_

 

I thought I remembered early on that there is really no opportunity for tube rolling here because of the circuit design?


----------



## Beefy

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_I thought I remembered early on that there is really no opportunity for tube rolling here because of the circuit design?_

 

Yeah, like _that_ is going to stop the diehards......


----------



## les_garten

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Yeah, like that is going to stop the diehards...... 
	

	
	
		
		

		
		
	


	


_

 


 Heh, yeah you're rite there!


----------



## orkney

Hi all,

 I'm very interested in this project but am a relative newbie to the world of DIY -- would this build be prohibitively difficult for a beginner? I'd have some help from an EE friend, but would want to rely on that sparingly. Any advice welcome and thanks,

 o


----------



## orkney

doublepost doublepost


----------



## cyanoacry

Hey all,

 I just got my boards up and running, but I'm running into a problem:

 One of my boards has huge DC offsets, with Out- at +47V and Out+ at -23V. The inputs were tied together to ground. No smoke, double-checked connections, and the rails are at +/- 300V.

 The other board is just fine, with offsets in the 100mV range.

 Anything I can check?

 Thanks,
 cyanoacry


----------



## Beefy

Quote:


  Originally Posted by *orkney* /img/forum/go_quote.gif 
_I'm very interested in this project but am a relative newbie to the world of DIY -- would this build be prohibitively difficult for a beginner? I'd have some help from an EE friend, but would want to rely on that sparingly. Any advice welcome and thanks,_

 

I wouldn't recommend it to a beginner. It isn't difficult per se, but there are a LOT of potential gotchas from the shunt power supply, high voltages, matching JFETs, etc. An EE friend isn't going to help with these key construction issues, unless they build it for you.

 Start with something simpler, and work your way up.


----------



## Sathimas

@ macm75 & boilermakerfan

 thanks for the advice - I just sent an email to top-print how big the transformer actually is.
 If a was able to sell the "wrong" transformer ordering a new one would be cheaper.

 Anyway I'm lucky to hear that I could still use the transformer.
 The mistake was on my side by the way.

 Thank you also for the tip with the aikiko preamp - but if I can only use
 it with my speaker setup its not useful for me since my headphone- and 
 speaker- setup are combined - only one CDP and turntable.


----------



## marcus1

I've almost got all the components to start assembly on my tube hybrid and have after rechecking the components (I have received) I find I've ordered the wrong resistors 
	

	
	
		
		

		
			





. 
 For the power supply resistors at R17, R18, R20 and R21, instead of 249K, 1/2 watt resistors, I've ordered 249K, 1/4 watt resistors (from the datasheet, these have a maximum working voltage V≅ ≤ 200 - http://www.vishay.com/docs/31018/cmfind.pdf).
 Are these 1/4 watters OK to use instead of the recommended 1/2 watt?

 I've also been reading about volume controls but am thinking about using my AKSA GK-1 preamp as opposed to something like the kit-set 24 step ladder type going cheap on ebay (VOLUME CONTROL TO 12AX7 6SN7 ECC88 ECC82 ECC81 EL34 6V6 - eBay (item 320456036248 end time Jan-29-10 04:58:14 PST), as discussed earlier. 
 Will the eXStata be a good match for my preamp or are there be gain issues to think about? 

 Thanks


----------



## paxeaxe23

Just been trying to work out the best way to have Balanced and unbalanced inputs. Would a combi Jack/XLR Female connector work? I can't find any pin diagrams for these sort of connectors.


----------



## orkney

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I wouldn't recommend it to a beginner. It isn't difficult per se, but there are a LOT of potential gotchas from the shunt power supply, high voltages, matching JFETs, etc. An EE friend isn't going to help with these key construction issues, unless they build it for you.

 Start with something simpler, and work your way up._

 

Thanks for the advice -- I'll start with a simpler build and keep this one in mind. Better my kids should have their fadda, as they say.

 best,

 o


----------



## Emooze

boilermaker, pabbi, did you end up putting any holes in the nabu case for ventilation or is the space inside good enough?


----------



## cyanoacry

Hi all,

 Figured out my issue: if the input JFETs aren't matched, then the trim pots won't be able to get the offset down to zero. Turns out I probably mismeasured or miswrote the Idss when I was testing all of them, so I matched another quad and went for it.

 On another note, it took me 60 JFETs to get three good quads. The first batch of 30 that I ordered had one half of a quad---nearly all the JFETs had Idss < 10mA.

 Anyway, the amp's working now; I'm waiting for it to warm up so I can adjust the offset. (Currently =<+/-1V)

 Thanks,
 cyanoacry


----------



## BoilermakerFan

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_@ macm75 & boilermakerfan

 thanks for the advice - I just sent an email to top-print how big the transformer actually is.
 If a was able to sell the "wrong" transformer ordering a new one would be cheaper.

 Anyway I'm lucky to hear that I could still use the transformer.
 The mistake was on my side by the way.

 Thank you also for the tip with the aikiko preamp - but if I can only use
 it with my speaker setup its not useful for me since my headphone- and 
 speaker- setup are combined - only one CDP and turntable._

 

Not a big deal actually, just use a selector switch for balanced or 4PDT switch for SE inputs... Send the signal straight through to eXStata, or send the signal to the Aikido to the speaker amp... The volume potentiometer can be in the circuit before the switch so you have one volume control for both options. 


  Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_boilermaker, pabbi, did you end up putting any holes in the nabu case for ventilation or is the space inside good enough?_

 

A lot of ventilation... Over the amp boards, nice big cut outs in artistic shapes on the top. You'll have to wait to see the results. The PS section will be perforated with small holes to vent heat above the heatsinks. The bottom chassis will be perforated under the board at the heatsink areas too, to allow cool air in. I'll probably add additional vents on the bottom in other areas too. Screen will put over all the openings.


----------



## pabbi1

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Yeah, like that is going to stop the diehards...... 
	

	
	
		
		

		
		
	


	


_

 

Exactly - I have some black plate CBS in the production build, and Tungsol in the proto - but, since they aren't the same to begin with, no real observation there. But, I also have some Amperex, and bought the Telefunkens off eBay - I just had to.

 Ok, so what did I hear? The actual participants were the two hybrid eXStatA, a Stax 313, Stax SRM T1, and the Headamp KGBH. Since we did NOT use the same source, there is no ceteris paribus, but...

 I remembered within 30 seconds why I long ago sold the SRM-T1 - simply not enough power. Oh they do well for the first half of knob travel, you know, ok, but lose steam after 12 o'clock. same with the 313 - servieable, but leaving you really wanting more.

 Caveat: I just don't like the OII, and listened to unmodded and modded versions today - just not for me.

 So, using the HE60, I compared the 5 amps. The BHSE is a REALLY nice amp. Radiohead's 'Subterranean Homesick Alien' was as etherial as anything I have ever heard, from the midrange up. Just transported me to a different place - almost astral projection. 

 The eXStatA (prod), on the same material is just a tad less lush, but far tighter in the nether regions - a firm bottom, with no jiggle. The midrange is just as lush, but not *quite* the same air, though a crisper presentation.

 Same experience with the Tool test - here we used Aenima, where the result was more of the same. The two amps are comparable, and really are tradeoff for what is more important to the listener.

 I do NOT know what the tubes are in the KGBH SE, but the bass was a bit flabby, an experience I live with on BH (even with Mullard xf2, circa 1961), well, or did (it is now dead to me, even if it lives).

 Also tried the 404LE on my prod version, and like them a lot, but there is a bit of what I'll call etch - something up around (WAG) 15k or so that is just a tad harsh - not sure what it is, but, enough to keep me from getting a pair (though several other factors intersect with that decision as well). This was on eXStatA and the BHSE

 Net-net, you guys are building a really good amp. Really.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Exactly - I have some black plate CBS in the production build, and Tungsol in the proto - but, since they aren't the same to begin with, no real observation there. But, I also have some Amperex, and bought the Telefunkens off eBay - I just had to.

 Ok, so what did I hear? The actual participants were the two hybrid eXStatA, a Stax 313, Stax SRM T1, and the Headamp KGBH. Since we did NOT use the same source, there is no ceteris paribus, but...

 I remembered within 30 seconds why I long ago sold the SRM-T1 - simply not enough power. Oh they do well for the first half of knob travel, you know, ok, but lose steam after 12 o'clock. same with the 313 - servieable, but leaving you really wanting more.

 Caveat: I just don't like the OII, and listened to unmodded and modded versions today - just not for me.

 So, using the HE60, I compared the 5 amps. The BHSE is a REALLY nice amp. Radiohead's 'Subterranean Homesick Alien' was as etherial as anything I have ever heard, from the midrange up. Just transported me to a different place - almost astral projection. 

 The eXStatA (prod), on the same material is just a tad less lush, but far tighter in the nether regions - a firm bottom, with no jiggle. The midrange is just as lush, but not *quite* the same air, though a crisper presentation.

 Same experience with the Tool test - here we used Aenima, where the result was more of the same. The two amps are comparable, and really are tradeoff for what is more important to the listener.

 I do NOT know what the tubes are in the KGBH SE, but the bass was a bit flabby, an experience I live with on BH (even with Mullard xf2, circa 1961), well, or did (it is now dead to me, even if it lives).

 Also tried the 404LE on my prod version, and like them a lot, but there is a bit of what I'll call etch - something up around (WAG) 15k or so that is just a tad harsh - not sure what it is, but, enough to keep me from getting a pair (though several other factors intersect with that decision as well). This was on eXStatA and the BHSE

 Net-net, you guys are building a really good amp. Really._

 

Thanks Al, really glad to hear that because, for me... Bass FTW!


----------



## gilency

Pabbi, what is the ppv on the proto SS you sold me? Enjoying it a lot with my Sigma Pro!


----------



## pabbi1

I am guessing 900v, but AC will have to verify, as we also did a follower mod to squeeze out some extra Vpp.


----------



## sergery

Quote:


  Originally Posted by *marcus1* /img/forum/go_quote.gif 
_Are these 1/4 watters OK to use instead of the recommended 1/2 watt?_

 

not sure 

  Quote:


  Originally Posted by *marcus1* /img/forum/go_quote.gif 
_I've also been reading about volume controls but am thinking about using my AKSA GK-1 preamp as opposed to something like the kit-set 24 step ladder type going cheap on ebay (VOLUME CONTROL TO 12AX7 6SN7 ECC88 ECC82 ECC81 EL34 6V6 - eBay (item 320456036248 end time Jan-29-10 04:58:14 PST), as discussed earlier. 
 Will the eXStata be a good match for my preamp or are there be gain issues to think about? 

 Thanks_

 

that would work. I found 50k is fine, maybe even overkill. If you want to save yourself assembly you could get something like this, I got the balanced version.

  Quote:


  Originally Posted by *paxeaxe23* /img/forum/go_quote.gif 
_Just been trying to work out the best way to have Balanced and unbalanced inputs. Would a combi Jack/XLR Female connector work? I can't find any pin diagrams for these sort of connectors._

 

There is a diagram on the website for wiring a switch, I think that is the preferred method. I plan to implement it. I suppose a combo jack would work though. personally I would rather have signal paths that are either in use or out of the way so I can leave multiple sources plugged in.

  Quote:


  Originally Posted by *gilency* /img/forum/go_quote.gif 
_Pabbi, what is the ppv on the proto SS you sold me? Enjoying it a lot with my Sigma Pro!_

 

Should be pretty close to 1kV p-p, I think it was follower modded. I can tell you it is no less loud/dynamic than my beta.


----------



## Hopstretch

Looking forward to giving the Exstata a shot with the O2s. Their midrange is sweet with the 007t but the lower end is notably floppy.


----------



## TimJo

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_Yes, Please do and report back!! 
	

	
	
		
		

		
		
	


	


_

 

Well, I am running the black plates now, and I can't say there is an obvious difference. There's part of me that thinks there may be a slight improvement in the low end (if that's even possible?), but I'm also thinking that my headphones are just breaking in and improving with every album I play. Bottom line is that it is sounding amazing. I haven't listened to my Beyers for weeks now. 

  Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_So, using the HE60, I compared the 5 amps. The BHSE is a REALLY nice amp. Radiohead's 'Subterranean Homesick Alien' was as etherial as anything I have ever heard, from the midrange up. Just transported me to a different place - almost astral projection. 

 The eXStatA (prod), on the same material is just a tad less lush, but far tighter in the nether regions - a firm bottom, with no jiggle. The midrange is just as lush, but not *quite* the same air, though a crisper presentation.

 Same experience with the Tool test - here we used Aenima, where the result was more of the same. The two amps are comparable, and really are tradeoff for what is more important to the listener.

 I do NOT know what the tubes are in the KGBH SE, but the bass was a bit flabby, an experience I live with on BH (even with Mullard xf2, circa 1961), well, or did (it is now dead to me, even if it lives).

 Also tried the 404LE on my prod version, and like them a lot, but there is a bit of what I'll call etch - something up around (WAG) 15k or so that is just a tad harsh - not sure what it is, but, enough to keep me from getting a pair (though several other factors intersect with that decision as well). This was on eXStatA and the BHSE

 Net-net, you guys are building a really good amp. Really._

 

I'm beginning to realize what a great amp this really is, and a fun build at that. I can't wait to get the enclosure finished. 

 Interesting to hear about the flabby bass on the KGBH - I'm glad I have an eXStatA because I do prefer '_a firm bottom, with no jiggle_.' 
	

	
	
		
		

		
		
	


	




 I keep reading about the etch that folks talk about on the 404LE's, but I guess I'm not hearing this. I need to get to a meet and do some side by side comparisons...

 So Al, how do the HE60's compare to the 404LE's in terms of bass response?


----------



## pabbi1

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_WellInteresting to hear about the flabby bass on the KGBH - I'm glad I have an eXStatA because I do prefer 'a firm bottom, with no jiggle.' 
	

	
	
		
		

		
		
	


	




 I keep reading about the etch that folks talk about on the 404LE's, but I guess I'm not hearing this. I need to get to a meet and do some side by side comparisons...

 So Al, how do the HE60's compare to the 404LE's in terms of bass response?_

 

That is one reason I settled on the he60 - I think it has better bass than the Stax - you will get virulent disagreement amongst the Mafia, who will fight to the death claiming the OII has better bass, but the issue is in how one defines bass. As a bass player (as it were), I listen to the QUALITY of the notes, moreso than QUANTITY, which the he60 has more of both over the 404LE, and the debate is left up to the reader about he60 vs OII, ESPECIALLY on the eXStatA.

 You will NOT be left for wanting bass on eXStatA, regardless of phones, though it is NOT a mushy below the bottom mess rattling your earpads, and, not for everyone - like guys bouncing their cars with megawatt subwoofers.

 My bias, my rig, my preference and all that. I do think the jury is out on eXStatA and the OII. Marc listened a bit, as did ASR, with their respective OII. Maybe they will post in the DFW meet impressions.


----------



## TimJo

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_I listen to the QUALITY of the notes, moreso than QUANTITY, which the he60 has more of both over the 404LE, and the debate is left up to the reader about he60 vs OII, ESPECIALLY on the eXStatA._

 

Well it sounds like we have similar tastes. I also tend to listen at lower levels, and one thing I'm liking about the eXStatA and stats is that the quality of the bass note has presence at lower listening levels. I'm listening to Jack Casady right now on an original RCA Victor pressing of _Crown Of Creation_ and it sounds amazing. It's funny to because when I first began to use this amp I wasn't sure I was going to like rock on stats, but I see I've begun to change my mind.

 I'm going to have to look into the he60's...


----------



## Sathimas

I am just about to order the new transformer and want to double check this time:

 I hope these values are ok:

 primary: 
 - 230V (I live in Germany)

 secondary: 
 - 500V*CT* @69mA
 - 6,3V*AC* @4A

 50VA rating in total


----------



## BoilermakerFan

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_I am just about to order the new transformer and want to double check this time:

 I hope these values are ok:

 primary: 
 - 230V (I live in Germany)

 secondary: 
 - 500V*CT* @69mA
 - 6,3V*AC* @4A

 50VA rating in total_

 

480VCT @ 65mA will be more than enough power with the 291V zener string. If you keep the 500VCT you will need a 300V (three 100V zeners) zener string.


  Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_That is one reason I settled on the he60 - I think it has better bass than the Stax - you will get virulent disagreement amongst the Mafia, who will fight to the death claiming the OII has better bass, but the issue is in how one defines bass. As a bass player (as it were), I listen to the QUALITY of the notes, moreso than QUANTITY, which the he60 has more of both over the 404LE, and the debate is left up to the reader about he60 vs OII, ESPECIALLY on the eXStatA.

 You will NOT be left for wanting bass on eXStatA, regardless of phones, though it is NOT a mushy below the bottom mess rattling your earpads, and, not for everyone - like guys bouncing their cars with megawatt subwoofers.

 My bias, my rig, my preference and all that. I do think the jury is out on eXStatA and the OII. Marc listened a bit, as did ASR, with their respective OII. Maybe they will post in the DFW meet impressions._

 

Man, Al, you're killing me. The HE60 is even more expensive than an O2 and double a 404LE. I'll be fortunate (and now highly motivated) to get a custom headband built for a member's HE60s drivers with a Stax cable and hopefully custom J$ HE90 pads if they get the design sorted out. May have to use Koss ESP/950 pads initially.


----------



## pabbi1

I hope the leather he60 pads happen, but, you are going to be a happy camper. Once I clean out all my riff-raff, I am looking for a 2nd set of he60, and thinking again about, well, you know. Maybe Wayne will loan me his to see if they are worth it.

 Nick, did you get the rest of your he60?


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_I hope the leather he60 pads happen, but, you are going to be a happy camper. Once I clean out all my riff-raff, I am looking for a 2nd set of he60, and thinking again about, well, you know. Maybe Wayne will loan me his to see if they are worth it.

 Nick, did you get the rest of your he60?_

 

I'll only be a happy camper for the brief length of time I have them here for custom work, then they ship off to Japan...


----------



## sergery

Man, HE60 party! maybe I will come one of these days. I have a pair but I am waiting for ze Germans to send me the rest of the goods so I can them in working order. Occasionally I listen in mono and try and use my imagination, lol :'( 

 I talked with Senn btw, they said HE60 earpads are officially a thing of the past. I too hope J$ pads workout.

 I still can't get over how smooth and lush this amp is!


----------



## sergery

crap, doublepost...


----------



## HeadphoneAddict

Quote:


  Originally Posted by *sergery* /img/forum/go_quote.gif 
_Man, HE60 party! maybe I will come one of these days. I have a pair but I am waiting for ze Germans to send me the rest of the goods so I can them in working order. Occasionally I listen in mono and try and use my imagination, lol :'( 

 I talked with Senn btw, they said HE60 earpads are officially a thing of the past. I too hope J$ pads workout.

 I still can't get over how smooth and lush this amp is!_

 

The new pad situation sucks. The pads on my HE60 look new after 18 months, and I have one new spare set laying around here somewhere but haven't seen them in a while (hid them somewhere too safe). And then I'm on the list for a J$ earpads as well. If I knew supplies were getting low I would have bought another 1-2 sets.


----------



## macm75

Alex's directions state to just power up the transformer at initial power supply start up. I'm using an old stock 480VCT (tested no load) transformer but wish to be cautious. Is slow variac controlled start up OK for this supply?


----------



## paxeaxe23

OK! I'm ready to go. Boards arrived today. Albeit the SS boards. (I was expecting the Hybrid ones, so ordered from Mouser accordingly) so my nice new Tubes and Transformer will have to sit there until Alex orders some more, but its still going to be fun I hope!

 Now, where did I put my Weller!

 Francis


----------



## pabbi1

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_Alex's directions state to just power up the transformer at initial power supply start up. I'm using an old stock 480VCT (tested no load) transformer but wish to be cautious. Is slow variac controlled start up OK for this supply?_

 

Can't see why not - it really should not matter - what value fuse are you using? I think 1a is sufficient, but make sure you have the resistor load on the psu before power up, or, you will be changing components.


----------



## macm75

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Can't see why not - it really should not matter - what value fuse are you using? I think 1a is sufficient, but make sure you have the resistor load on the psu before power up, or, you will be changing components._

 

Yikes. Thanks for the fuse reminder for the initial setup.


----------



## TimJo

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_Alex's directions state to just power up the transformer at initial power supply start up. I'm using an old stock 480VCT (tested no load) transformer but wish to be cautious. Is slow variac controlled start up OK for this supply?_

 

That's a good question. I'm not sure with a shunt supply. 

 I'm not sure it is necessary though, if you follow Alex's startup instructions with the trimpots preset to the halfway position. The main thing is to be sure to have the load resistors connected when you do power up.

 edit: I see pabbi and i posted at the same time.


----------



## studeb

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_Alex's directions state to just power up the transformer at initial power supply start up. I'm using an old stock 480VCT (tested no load) transformer but wish to be cautious. Is slow variac controlled start up OK for this supply?_

 

Just to add to everyone else
 I used a 1A fuse
 Make sure load resistors are correctly wired
 Trim pots down
 Plug in, watch for smoke. I had a hand ready to kill power.
 start playing with trim pots

 No variac needed. I think if there is an issue, it will smoke right away, and you will know right away,


----------



## TimJo

So how many folks out there are listening to the eXStatA at this point? I'm curious to hear more impressions from others.

 I just can't get enough of mine. At first I wasn't sure I was going to like stats and rock, but now I have totally changed my mind. I've been listening to a lot of Pavement lately, and the tonality of the guitars, and the clean detail of the bass, continues to blow me away. Listening to the 4 LP reissue of _Brighten The Corners_ right now and a tune like _Type Slowly_ sounds better on this system than any other I have heard so far. It's a very lush sound, but with incredible detail. Sometimes this much detail has the tendency to sound too clinical to me, but on this setup it sounds very dreamlike and I just want the song to keep going. I guess that's it - I get drawn into the music, rather than feeling the need to dissect it or get sidetracked with the details. This is an amazing amp, and the 404LE's aren't bad either. 
	

	
	
		
		

		
		
	


	




 Thanks again Alex for gifting us this great amp!


----------



## pabbi1

What I find so amazing is that when you actually hear all the microdetail, it really changes your opinion of musicians, not just in what they can do musically, but the attention to detail, and how complete the canvas can be. Or, other long held favorites tend to rather wilt in how flat and rushed the effort is compared to someone with the studio time (budget) to really get something right. Well, or just tacking crap on to make something sound more robust without any other real purpose.

 Oasis tends to be in my first group, and early AC/DC tends to be in my latter, but, it's hard to kill that 1961 Les Paul (that looks like a SG) or Malcolm's Gretsch.

 Yeah, it would be nice to hear more impressions, as this really is a small club, and not that difficult a build.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_What I find so amazing is that when you actually hear all the microdetail, it really changes your opinion of musicians, not just in what they can do musically, but the attention to detail, and how complete the canvas can be. Or, other long held favorites tend to rather wilt in how flat and rushed the effort is compared to someone with the studio time (budget) to really get something right. Well, or just tacking crap on to make something sound more robust without any other real purpose.

 Oasis tends to be in my first group, and early AC/DC tends to be in my latter, but, it's hard to kill that 1961 Les Paul (that looks like a SG) or Malcolm's Gretsch.

 Yeah, it would be nice to hear more impressions, as this really is a small club, and not that difficult a build._

 

Time has not been my friend as of late and one of the suppliers I need to order from took forever to confirm an order and I'm not sure when it's going to show up...

 But once I can start building, there will be two more eXstatas reporting in, one will be my SS and the Hybrid goes to a member who will post his own experiences. 


 If we have a PS transformer that has the heater windings, is there any reason why it can't be used for a SS amp? I'm assuming it can be used without damage as long as the leads do not short out, correct?


----------



## pabbi1

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_If we have a PS transformer that has the heater windings, is there any reason why it can't be used for a SS amp? I'm assuming it can be used without damage as long as the leads do not short out, correct?_

 

Yes, that is my experience, though mine is normally that the heater windings are 6.3v and 5v, where the 5v just gets clipped, or tied off, with the liquid electrical tape applied to the ends.


----------



## macm75

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_If we have a PS transformer that has the heater windings, is there any reason why it can't be used for a SS amp? I'm assuming it can be used without damage as long as the leads do not short out, correct?_

 

I know Pabbi1 already reported but just wished to confirm. No problem with not using a winding what-so-ever. And like you said, electrical tape the unused ends. Matter of fact, I picked up a old/unmarked transformer for this project and pretty sure (or assume to be safe) the 6.3V winding will not be able to deliver 2.5+ A. They will go unused and I'll have a separate filament transformer for 6.3VAC (on the hybrid).


----------



## luvdunhill

you might see higher voltages if all the windings are not utilized, depending on the specs of the transformer.


----------



## Beefy

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Yes, that is my experience, though mine is normally that the heater windings are 6.3v and 5v, where the 5v just gets clipped, or tied off, with the liquid electrical tape applied to the ends._

 

I would use a terminal block personally......


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I would use a terminal block personally......_

 

That was my plan. I have those sweet miniature 15mm DIN rail terminal blocks.


----------



## macm75

Guys,
 Just powered the PS with dummy load minutes ago. I get 238-0-238VAC in and adjusted P1 and P2 to get the desired 360mV and 410mV respectively. I do not get greater than +320V and -320V at T1 and T3. I measured +298V and -298V (same as the output at the dummy loads) - can I move forward or is this an issue?
 Thanks, Joe


----------



## Beefy

Well, it would say to me that you are essentially getting no regulation. Far from ideal.

 Refresh my memory...... what transformer are you using?


----------



## macm75

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Well, it would say to me that you are essentially getting no regulation. Far from ideal.

 Refresh my memory...... what transformer are you using?_

 

Transformer comes out of an old tape recorder. I have another to use but cannot see why transformer would be the issue.
 I powered it up again and found another issue. New concern is T1-T2 and T3-T4 only sit at there desired voltage for moments. After about 30 seconds, they start drifting lower and LED's go out.
 At first I'd ask what transistors do I need to replace but the issue is with both sides. Rats - transformer is the only thing that is common to both sides but all the while the PT continues to hold at 238-0-238VAC.


----------



## Beefy

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_Transformer comes out of an old tape recorder. I have another to use but cannot see why transformer would be the issue.
 I powered it up again and found another issue. New concern is T1-T2 and T3-T4 only sit at there desired voltage for moments. After about 30 seconds, they start drifting lower and LED's go out.
 At first I'd ask what transistors do I need to replace but the issue is with both sides. Rats - transformer is the only thing that is common to both sides but all the while the PT continues to hold at 238-0-238VAC._

 

No, I think it is definitely the transformer.

 While the amp is cold, and the zener string is cold, the voltage reference is close to the 'proper' value of 291V. As long as the T1-T3 voltage is higher than this, current will flow through the shunt transistors and the LEDs lighting them up.

 But as the PSU/zener string warms up, the voltage reference gets higher due to the zener's positive tempco - it rises into the 300-310V range. If this is higher than the T1-T3 voltage, no current flows through the shunt transistors or LEDs.


----------



## macm75

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Well, it would say to me that you are essentially getting no regulation. Far from ideal.

 Refresh my memory...... what transformer are you using?_

 

OK Beefy, transformer is the issue. Way back I remember Alex saying we need (if I remember correctly) between 320V and 350V at the caps. I'm short - I only get 295 - I obviously need some overhead to regulate.
 I'm getting the other transformer out - I believe it supplies more voltage. 
 These transformers are free so I cannot complain so far.

 Edit, I wrote mine as while you posted. As I said, you're on the money. Thanks.


----------



## macm75

New PT is in. Better but still not at the specified T1/T3 values. I now have 315V on T1 and 312V on T3. T1-T2 and T3-T4 are steady at 360/410mV. 
 I'm assuming I'm out of luck with my free-bee's but... 
 instead of replacing a PT, can I replace my 91V zeners with say ~80V and run B+ at -290V and +290V. Surely the circuit does not care about 10V difference in supply voltage.


----------



## Beefy

Yeah, you could do that and it wouldn't hurt too much. Just a few less volts maximum swing...... or a little bit less permanent deafness, if you prefer to look at it that way


----------



## macm75

Thanks for the support Beefy. Luckily I found an ebay seller with 75 and 82 volters located less than an hour from my house. Wait (although not easy) will not be long.


----------



## pabbi1

Man, nothing like having a local guy with an aisle full of zeners, and an 60' wall with bins full of resistors and caps - EXCEPT he is closed on Sunday.


----------



## Beefy

You should still be able to fire it up, do the initial setup etc. without any problems. Your offset might just drift around if one rail drops out of regulation, and it might not sound as good. I really doubt you'll break anything......


----------



## pabbi1

Speaking of sound, anyone else with comments?


----------



## Beefy

I'm thinking that the majority of builders electrocuted themselves.


----------



## les_garten

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I'm thinking that the majority of builders electrocuted themselves._

 

Here's an actual photograph of an eXStata listener!


----------



## pabbi1

One design, so many Darwin Award candidates... sigh.


----------



## Sathimas

I ordered the parts from mouser yesterday and will hopefully start to solder next weekend.

 The main problem is that I ordered the transformer with wrong values so it'll take some more time for the new one...
 Hope to get him until mid of February.

 Maybe the problem why many builders don't post their impressions is that they have nothing to compare to?
 I also will have no possibility to compare the amp to any other stat-amp.


----------



## TimJo

Here's an update on my eXStatA. I ended up going back to the GE grey plates that I got from pabbi1. The RCA's sounded fine, but they exhibited a strange behavior on one channel. I didn't spend too much time trying to figure it out, and instead went back to the GE's since there is probably little to no difference in sq based on the tubes. 

 With the RCA's I have, I could dial in the offset and balance on the left channel, but then in a manner of hours, the balance would drift about 4 volts in one direction, and the offset around 2 volts. I would then get them dialed in again, and then they would drift again. I tried both sides of zero (i.e. setting the balance slightly positive or slightly negative) but it would then drift in either direction, away from 0 volts. It seems like one of the tubes must be bad, but I only have the four of them. Anyway, putting the GE's back in, they dial in nicely, and remain stable.

 Man, I am really loving this amp. Can't get enough listening time on it...


----------



## cyanoacry

Hey all,

 I've been listening to my SS amp for a while now, and here are some initial impressions. My previous setup was a Stax 2020 combo---SRM-252A + SR-202, with stock Stax cables and a gamma-2 source. Only thing that's changed is the upgrade to an eXStata.

 - detail is incredible!

 The amp really does reveal microdetails---down to the point where I could hear SMPS noise in several TV episodes I had. Sure, I thought it might've been placebo or noise coming from the amp, until a friend of mine ran a spectrogram on the audio:






 That 16KHz peak is audible, and I don't think I would've noticed it with my previous setup. (The audio is lossless from the Blu-ray version of K-ON! 14.)

 Other tracks showed similar revelation in detail. Small orchestral pieces are suddenly filled with breathing and scraping; the soundstage is huge on any well-recorded classical track. One particular track that stood out to me was "Shin'en" from the first Mushishi OST. It's a track consisting solely of bells, and you can tell that post-recording modification is small if non-existent. The reverberation is incredible, and you can hear the movement of the bell-players' feet if you listen carefully.

 Detail's always a dual-edged sword, though. MP3 drums and cymbals sound notably terrible, but it's possible to enjoy music that's at 128Kb/s anyway, if only because the musicality is there. Dynamic compression shows equally well---you -will- know when your music has been passed through a blender, and you'll be yelling at the studio forever.

 - the amp is dead quiet

 Before I installed the attenuator, I couldn't see anything out of the amp. I have a Fluke 115 meter, and the mV scale AC didn't show anything either with the inputs grounded/hooked up. Without any connections, the amp seems to like to oscillate---this isn't a problem, though, since it's always hooked up. No noise, even though it's currently sitting on my desk without any shielding whatsoever.

 Connecting a Joshua Tree attenuator caused some problems; there's a slight buzz on the left channel that I've isolated to the transformer running the JT inducing noise in the lines, but the amp itself is sound.

 - bass is extended, full, and tight

 Listening to trance tracks on the eXStata is amazing. I live in a dorm with a roommate, and I have the gamma-1 portion of the gamma-2 feeding speakers. The first time I listened to Cascada, I had to make sure the speakers were off---the bass is considerably better than I remember.

 This amp is worth its weight in gold. There's really no reason to complain---HeadphoneAddict's review was pretty much spot on. If people hear this amp, there's no going back.

 I'd like to do some quantitative analysis on the amp, just to make sure there's no bias involved. Once I get it cased up, we'll see---I have access to some nice lab equipment here at college, and hopefully a lab won't mind me borrowing stuff for a weekend.

 cyanoacry


----------



## TimJo

For anyone who hasn't checked out the Dallas meet impressions, you should take a quick look since pabbi1 had the eXStatA there. Here are some comments.

  Quote:


  Originally Posted by *ktm* /img/forum/go_quote.gif 
_The big draw for me was the exstata. And it didn't disappoint.
 It beat both my current units, the srm-313, and srm1mkII.
 The srm-313 has too much high end and the srm1mkII too little.
 The srm1 seems to roll off very early in the highs.
 The exstata covers the whole range very well with good bass
 and wide soundstage. I tested it with stock 404's. 
 I could live with that combo very well.

 Goal for this year: get a set of boards and build an exstata.
 If that fails, stake out pabbi1's house and wait for him to thin 
 out his collection!!!!_

 


  Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Listening to the Cavalli amps, I immediately noticed that the current version is a vast improvement over older iterations. I couldn't get that strange clipping to happen and it never seemed to run out of steam. However, in the back of my mind the analogy went like this: Gen1 SS > Gen1 tubes && Gen2 tubes >> Gen1 tubes so, does Gen2 SS >> Gen2 tubes? 
	

	
	
		
		

		
		
	


	




 If you don't follow, I'm very excited to hear the newest solid state version. The frequency response relatively even to me, with perhaps a slight dip in the midrange. I felt there was some artificial detail in the highs that I more or less attributed to the upsampling source. The bass was pretty even I though, extending very low but without as much midbass impact as the Blue Hawaii. I listened mostly to the Stax and didn't really bother with a HE60 comparison. I felt that the overall sound was a bit better with the 404LE, with my "fit adjustment" outlined above. I think the HE60 / 404LE was a better comparison than either with the SR-007mk1. They were in fact rather similar, and at the price point I think I'd take the 404LE over the HE60. Anyways, I enjoyed the Cavalli amp and cannot wait to hear the new solid state revision, as I have high hopes for it._

 


  Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_...Anyways, someone who was listening pointed some sibilance out on a recording or two, and when we compared that same track on the Cavalli 'stat amp, that particular track was much smoother._

 

This is what I have found as well. I commented on this a week or so ago, because when listening to vinyl, sibilance can be an issue. This amp connected to the phono pre amp creates a very clean yet smooth sound.


----------



## pabbi1

I believe Marc will be taking measurements, and find him a pretty even handed reviewer, even if he is misguided on the hybrid vs SS thing... 

 But, this amp has caused me to completely rethink my source. 

 Oh, and the proto WITH the follower mod (which we did not have in place at the Houston nor DFW meets narrows the gap in differences between versions.
 Just finished that last night (replecing resistor strings), and plan to see what those differences are - since I have a production unit, a completed proto, and a set of proto boards waiting to be built.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_One design, so many Darwin Award candidates... sigh._

 

My DMM died, so I just licked the pads to see if it had voltage...

 Now my tongue is numb, but I think it's about 340V and it made my face look like this:


----------



## Beefy

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_Maybe the problem why many builders don't post their impressions is that they have nothing to compare to?
 I also will have no possibility to compare the amp to any other stat-amp._

 

I'm in this boat. My only comparison is a SRD7-SB powered from a T-amp, and the chances of me listening on any other Stax or 3rd party amp are slim to none.


----------



## pabbi1

Well, you could still say if you like or don't like... and just that it really is working... Not everyone has the opportunity to roll out the entire armory of the Stax mafia. 
	

	
	
		
		

		
		
	


	




 And, pictures of builds are always, well, fun.


----------



## Beefy

I'm pretty sure I have already said it is much better than my previous combo


----------



## LingLing1337

I may want to give this one a shot. When is the next PCB group buy?


----------



## luvdunhill

Hey guys, cranked out another batch of teflon Stax jacks this weekend and have 6 jacks left over. If anyone is interested, PM me and I can get them out pretty much immediately.


----------



## Blutarsky

PM to luvdunhill!


----------



## Sathimas

Quote:


  Originally Posted by *LingLing1337* /img/forum/go_quote.gif 
_I may want to give this one a shot. When is the next PCB group buy?_

 

This is not determined yet - I think there will be another group buy but not in the coming two or three months if I got runeight right.


----------



## bidoux

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I'm thinking that the majority of builders electrocuted themselves._

 

No risk, I havn't even ordered the parts yet.


----------



## n_maher

For anyone gathering parts, I ended up with a spare 4ch Alps RK27 pot which I've listed for sale. [/shameless plug]


----------



## n_maher

For anyone gathering parts, I ended up with a spare 4ch Alps RK27 pot which I've listed for sale. [/shameless plug]


----------



## ChrisX

I just matched the J-FETs for my sand build. Out of a batch of 60 I found 21 with an Idss > 10 mA and out of these I could gather three quads. So statistically the recommended 20 J-FETs for one quad should turn out, but I wouldn't be sure if always.

 My three quads have Idss values of 10.0/10.0/10.2/10.5 12.4/12.5/12.6/13.0 13.9/14.1/14.3/14.3 mA.

 So which quad is to prefer? The higher Idss the better? Or better be close from above to the specified 10 mA minimum? Or the middle one as compromise?


----------



## Beefy

The highest looks like the best quad, as it would be the lowest % difference between them.


----------



## luvdunhill

The highest looks the best. Also, 0.1-0.2mA is probably within the realm of error, even if you have the most accurate meter in the world. For example, if you pick the JFETs up with your fingers and place them in a test jig, you may notice slightly different readings then if you used a pair of pliers.


----------



## Emooze

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I'm thinking that the majority of builders electrocuted themselves._

 

The PS caps carry quite a punch....

 I can't get enough of this setup. It's going to be at the Boston/MA meet in early March for more diverse impressions, potentially next to n_maher's.

 I do however think the driver is loose in my Lambdas. I'm gonna have to look into that.


----------



## ChrisX

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Also, 0.1-0.2mA is probably within the realm of error, even if you have the most accurate meter in the world. For example, if you pick the JFETs up with your fingers and place them in a test jig, you may notice slightly different readings then if you used a pair of pliers._

 

I don't expect the absolute error of my measurement to be within 0.1-0.2 mA, but worse. Relative to each other what is important here I believe to be within about 0.1 mA. Quick measurement was only done as first step to sort out the low Idss j-fets. As second step for the matching I waited for the multimeter reading to be stable up to the third digit what happened after approx. one minute. So my fingers' temperature shouldn't have been of any influence any more.

 So I will go with my high-Idss j-fets.


----------



## digger945

The longer you leave them in the test circuit, the more they will settle/drop. Mine usually drop .1mA within the first 30 seconds, and then possibly another .1 in the next minute or two. I have not seen one yet that dropped any more after 5 minutes.
 Given my meter(low end Fluke) and the circuit used(voltage drop across 10R, using 12V PS), max resolution is .1mA.


----------



## MrMajestic2

Ok, its official, I wont have time to build this 
	

	
	
		
		

		
		
	


	




 My kit is up for sale if anyone is interested here: http://www.head-fi.org/forums/f44/ca...7/#post6370967

 I don't have stats either and my wallet is like "Dude, I'm hungry"


----------



## marcus1

I'm currently building the a hybrid version of the eXStata but still haven't decided on a volume control. The Lightspeed Passive Attenuator here DIY Lightspeed Passive Attenuator (audio optocouplers) sounds interesting but I'm not sure if it will suit the eXStata - the criteria for using it are:
 Low output impedance sources and high impedance amplifiers:
 1: Low source impedence (cd player) <50ohms
*2: High input impedence (amplifier) > 50k.*

 Will this suit the eXStata?

 Thanks


----------



## srserl

The lightspeed, as is, does not attenuate a balanced signal, so you would need 2. I have ideas to try with respect to a balanced ldr attenuator based on the lightspeed, but have only built an unbalanced one on perfboard. I plan to later put it in a Pass Labs B1 buffer preamp.
 For a lot more info on the Lightspeed and buying matched sets of ldrs, see the thread on DIYAudio.com.


----------



## minivan

a local is generous enough to give me a commerical version of kgss from headamp for a week to compare with the exstata. 

 setup for comparison is:

 buffalo dac balance out to exstata
 buffalo dac single end out to kgss
 (did comparison first between buffalo balance/single end out to kgss to make sure there's not difference between the two)
 headphone is o2.

 listen to one track first on one amp, switch over to the other amp, repeat the the track.


 one most obvious different when switching over from kgss to exstata is: exstata little better resolution. imaging is crisper, sharper, better focus, better defined.

 soundstage is a bit wider with the exstata, there 's a bit more space
 between instruments.

 kgss sound warmer, laid back, exstata has faster attack and transient response.

 vocal is more forward in kgss, vocal in exstata sound a rew row further back but without lost of detail and focus.

 can't tell much different on bass between the two, may be bass in exstata is a bit leaner and tigher with better texture and definiton.

 treble has better extension on the exstata, revelation of micro detail in this area is better.


 i like to say thanks again to the indiviual who let me borrow his kgss for a week.when i first built the exstata i thought it's very good, but have no idea how good it is in compare to other well known electrostatic amp ( the only full size eletrostatia amp i had heard at the time is the little known chinese diy 8ps amp mr he built for me)
 the kgss enbale me to set a benchmark and compare the exstata with.

 i am extremely happy with my exstata, it only cost me $450 aud all up ( about $400 usd at the time of currency exchange), a Significance saving. thanks alex for bringing us this amp.


 some obseration of the kgss, it run very hot, i can feel the heat on my hand through the vent on the case. dc offset is over 8v on startup and it take over 20 minutes for the dc offset to drop below 1v.


----------



## les_garten

You might want to edit your post as to which exstata you compared?

 EDIT: Solved with the pic added!


----------



## fierce_freak

Nice impressions, minivan.

 I managed to get my eXStata power supply up and running the other night, so the rest shouldn't be too far behind. I've been super busy with house renovations and certification studying leaving electronics on the back burner.


----------



## fierce_freak

double post O.O


----------



## audionut

some obseration of the kgss, it run very hot, i can feel the heat on my hand through the vent on the case. dc offset is over 8v on startup and it take over 20 minutes for the dc offset to drop below 1v. 
 __________________
 Yes, my P2P KGSS runs very hot as well, and I had a hard time getting enough heatsinking to cope with the heat. Also, my offset takes at least 20 minutes to drop below 1V too. I recently had a Blue Hawaii to repair for another headfier, and the offsets also took forever to stabilize. Not sure why this is. On my eXStata hybrid, offsets go below 1v within a few seconds after power up, if I remember right.
 I have not been able to post any impressions between my KGSS and eXStata, due to my KGSS being down for repair (resistor opened up in output stage), and my ESP950's having to go to Koss for lifetime warranyt repair. Hopefully get some impressions soon, as my phones are back and the KGSS is up and running again.


----------



## pabbi1

Hopefully a few more of you guys are getting closer... sitting here listening to The Verve Pipe "Villains"... just feel guilty, like 'flying private' on a Gulfstream - sure more people could come along, but somehow, only a couple could make it.

 Now to dump this crappy source, and get my new tube output stage source in by next weekend, then we'll really see what's what. One of these days, I'll get around to tube rolling - CBS black plates (that I have in now) vs Tung Sol vs Amperex vs Telefunken, so, yes, I am still acquiring tubes, because this ain't my only electrostatic amp that uses 6s4a.


----------



## WilCox

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Hopefully a few more of you guys are getting closer..._

 

I should be joining you in your Gulfsteam soon.
	

	
	
		
		

		
		
	


	




 My backordered parts from Mouser arrived this week and I now have completed PS and amp boards for my SS eXStatA. My Hammond case is here and a four-gang Alps is on the way thanks to Nate. Hope to find time in the next few days to get her up and running.


----------



## pabbi1

I am REALLY curious if you SS guys like yours as much as I am the hybrid.


----------



## Keithpgdrb

sure would like to see some more pics of the builds I'm reading about.. I need case ideas for the future.


----------



## Lou Erickson

I am finally getting all the last parts together to build this.

 I think the last stumper for me is a volume pot. I'd really prefer a four-gang pot or stepped attenuator, but am not finding anything I'm thrilled by. Suggestions would be welcome for something reliable and not too expensive.

 I've also noticed a quirk with a couple of things on the power supply BOM. I got the part numbers listed, but the wattages of a couple of the resistors are lower. For instance the part number for R9-R12 is listed as 71-CCF55-150K, for 1/2W 150Kohm resistors. The parts I have have the same part number, and are 150Kohm, but are only 1/4 watt. The order detail says "Metal Film Resistors 1/4watt 150Kohms 1%
 Rated to 1/2watt".

 Similar situation with R17, R18, R20, R21. BOM says 1/2 watt, part from Mouser says 1/4 watt, but the order detail says "1/4watt... Rated to 1/2watt".

 Are these the right ones, or should I order higher wattage? (My instinct is to order larger.)

 So far, so good... =)


----------



## runeight

Hey boys. I have a few early morning minutes to check in on you. I've tried to read the last several pages.

 There was one comment by one of you about how the amp likes to oscillate. I don't remember who this was but please see the website about grounding the heatsinks. This will stop the oscillation.

 One of you lives in Italy (Trieste), but I don't remember who you are. My wife emailed me saying that the package has been returned. I don't know why and won't know until I return home. My apologies for this as I might have messed up the address. Please email me and when I return I'll send the boards again.

 Resistors in the PS are ok. CCF55 can handle the wattage requirements for the intended use.

 Have I missed anything important? If not, thanks for all of the nice reviews/comments. I'll go back to other business, which at the moment is in Wash, DC where we are having a blizzard with at least 15" of snow on the ground with another foot at least to come. I just want to go back to Texas where the skies are bright and I can see from horizon to horizon.


----------



## digger945

Quote:


  Originally Posted by *Lou Erickson* /img/forum/go_quote.gif 
_
 I've also noticed a quirk with a couple of things on the power supply BOM. I got the part numbers listed, but the wattages of a couple of the resistors are lower. For instance the part number for R9-R12 is listed as 71-CCF55-150K, for 1/2W 150Kohm resistors. The parts I have have the same part number, and are 150Kohm, but are only 1/4 watt. The order detail says "Metal Film Resistors 1/4watt 150Kohms 1%
 Rated to 1/2watt".

 Similar situation with R17, R18, R20, R21. BOM says 1/2 watt, part from Mouser says 1/4 watt, but the order detail says "1/4watt... Rated to 1/2watt".

 Are these the right ones, or should I order higher wattage? (My instinct is to order larger.)

 So far, so good... =)_

 

I'm not sure you have the right parts per the BOM as I have not had time to look at it lately, but the Vishay Dale CCF resistor, according to the data sheet, is dual rated. If you look at the first bullet under "Features" at the top of the data sheet, it gives % stability at a given wattage rating. Ultimately they are rated for ½ watt at ≤250V. The CCF60 is rated up to 1 watt and ≤ 500V (see "Technical Specifications" on both data sheets).
 On a similar note, if you look at the data sheets for RN and CMF series resistors, you will see remarks that they are exactly the same part. The only difference is the rating and the markings, with military RN series parts being rated lower than the equivalent CMF part.

Resistors, fixed discrete - Vishay

 EDIT: Also note Alex's remarks above.


----------



## bgcgreality

Недвижимость в Болгарии очень прибыльное и выгодное вложение, для покупателя. Приобретая недвижимость в Болгарии Вы надежно вкладываете свои денежные средства и, кроме того, получаете квартиру или дом на берегу моря. Для граждан России покупка квартиры в Болгарии проблем не составляет. Вид на жительство получает каждый, кто открывает бизнес или приобретает недвижимость в Болгарии. Недвижимость в Болгарии обойдется Вам намного дешевле, чем в России на Черноморском побережье. цена недвижимость болгария


----------



## marcus1

Hi Alex

 I posted a query a few days ago about using the Lightspeed Attenuator with the eXStata (hybrid) but didn't get an answer. The criteria for using it are:

 1: Low source impedence (cd player) <50ohms
*2: High input impedence (amplifier) > 50k. *

 What is the eXStata input impedence?

 Thanks

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Hey boys. I have a few early morning minutes to check in on you. I've tried to read the last several pages.

 There was one comment by one of you about how the amp likes to oscillate. I don't remember who this was but please see the website about grounding the heatsinks. This will stop the oscillation.

 One of you lives in Italy (Trieste), but I don't remember who you are. My wife emailed me saying that the package has been returned. I don't know why and won't know until I return home. My apologies for this as I might have messed up the address. Please email me and when I return I'll send the boards again.

 Resistors in the PS are ok. CCF55 can handle the wattage requirements for the intended use.

 Have I missed anything important? If not, thanks for all of the nice reviews/comments. I'll go back to other business, which at the moment is in Wash, DC where we are having a blizzard with at least 15" of snow on the ground with another foot at least to come. I just want to go back to Texas where the skies are bright and I can see from horizon to horizon. 
	

	
	
		
		

		
		
	


	


_


----------



## manaox2

Quote:


  Originally Posted by *minivan* /img/forum/go_quote.gif 
_


 a local is generous enough to give me a commerical version of kgss from headamp for a week to compare with the exstata._

 

Thank you so much for the review. Man, I need to get on this.


----------



## Scooba

Greetings everyone, I have spent my last 4 days reading this thread . Thanks everyone for their input (and especially the design team) .
 I am very interested in building the SS version and maybe even the hybrid. Please count me in for the next batch of boards (or if anyone has some unused spare boards please PM me).


----------



## les_garten

Quote:


  Originally Posted by *marcus1* /img/forum/go_quote.gif 
_Hi Alex

 I posted a query a few days ago about using the Lightspeed Attenuator with the eXStata (hybrid) but didn't get an answer. The criteria for using it are:

 1: Low source impedence (cd player) <50ohms
*2: High input impedence (amplifier) > 50k. *

 What is the eXStata input impedence?

 Thanks_

 

You seem to be on the Lightspeed thing and nobody else has really chimed in on it. So, I'll give you what I found and why I'm not interested in it.

 1) You have to match the devices closely, this gets expensive with each added device. So balanced setups become high dollar.
 2) These devices drift their performance relatively quickly. So you have 4 devices that may all drift at different rates. Expect frequent tweaking, measuring, replacement and maintenance. You into that? I wasn't.

 I found a balanced setup on ebay, "cheap" and started asking questions and looking into it on DIYAudio.

 Of course everyone has to make their own path. The Lightspeed option was booted out of my path.

 The quest continues, I thing we need a really good, flexible, cheap, relay/resistor based attenuation system.


----------



## studeb

Quote:


  Originally Posted by *marcus1* /img/forum/go_quote.gif 
_Hi Alex

 I posted a query a few days ago about using the Lightspeed Attenuator with the eXStata (hybrid) but didn't get an answer. The criteria for using it are:

 1: Low source impedence (cd player) <50ohms
*2: High input impedence (amplifier) > 50k. *

 What is the eXStata input impedence?

 Thanks_

 

See post #965 from the master

 i do not think the Zin has ever been measured or hypothesized


----------



## digger945

Input impedance will be dominated by, and ever so slightly less than(in most cases), the input attenuator chosen.


----------



## Lou Erickson

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Resistors in the PS are ok. CCF55 can handle the wattage requirements for the intended use._

 

Excellent! Thanks runeight! Hope your trip goes smoothly and you make it back to where you want to be.

 Now... if I can just find what I did with those other parts... 
	

	
	
		
		

		
		
	


	




 Hey! I found them. Also, ordered a couple of nabu cases to make sure they're in a box of some sort.

 Now I can match some JFETs... whee!


----------



## studeb

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Input impedance will be dominated by, and ever so slightly less than(in most cases), the input attenuator chosen._

 

right, but what is the Zin of the amp? The poster was saying the lightspeed (input attenuator) will want to see an Zin of at least 50k.
 So what is the Zin of the PCB?


----------



## Beefy

A JFET input stage should have a very high impedance.


----------



## macm75

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_1) You have to match the devices closely, this gets expensive with each added device. So balanced setups become high dollar._

 

We have ears! Balance for free!


----------



## ericj

Took my eXStata SS prototype to the Salt Lake City mini-meet today, along with my ESP/950 and SR-Lambda. 

 Seemed to be very well received with the ESP/950 the big hit - but i was the sole attendee with any experience with 'stats, and all we had to compare them with was the E/90 and SRD-7 (SRD-7 powered by my Hitachi HMA-6500 mosfet power amp, with my old SOHA 1 with lm4562 doing preamp duty). 

 I also had my Sony ECR-500 powered off the same speaker amp as the SRD-7, and about three dozen misc orthos and dynamics (mostly AKG studio stuff).


----------



## runeight

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_right, but what is the Zin of the amp? The poster was saying the lightspeed (input attenuator) will want to see an Zin of at least 50k.
 So what is the Zin of the PCB?_

 

1M


----------



## jcx

I hate to see so much mental energy and money wasted on balanced input for the exstata - having a high impedance differential front end it can accept single ended signals and still give the same output performance - up to the limitations of its low loop gain and consequent sensitivity to matching just about all of its components

 it is unlikely that enough have been built that that even one exits (by statistical chance) that actually would give a "better balanced" output with balanced input vs single-ended input given device and component parameter distributions - that are not being measured/matched/trimmed

 even with balanced source you could save money with dual attenuators with little to worry about in loss of "sound quality"


----------



## pabbi1

I believed the discussion was more the relative QUALITY of attenuation, not how to get there, but, hey, I am so oblivious to all that anyway.

 What I detest is using an ALPS rk27, regardless of the number of decks. This amp deserves better.

 Now, the SOURCE might be a crisis, and require much mental anguish, not to mention peer validation. But, heck, that is almost every DIY build discussion... 
	

	
	
		
		

		
		
	


	




 In other news, I did the follower mod to the 'red board proto'. and really can't tell any difference with the 'black board prod'. So, Marc, I think the ccs, the only remaing difference, really is not audible. Maybe using the WPS/Amphenol jack instead of your jack is a more likely difference.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_I believed the discussion was more the relative QUALITY of attenuation, not how to get there, but, hey, I am so oblivious to all that anyway.

 What I detest is using an ALPS rk27, regardless of the number of decks. This amp deserves better.

 Now, the SOURCE might be a crisis, and require much mental anguish, not to mention peer validation. But, heck, that is almost every DIY build discussion... 
	

	
	
		
		

		
		
	


	




 In other news, I did the follower mod to the 'red board proto'. and really can't tell any difference with the 'black board prod'. So, Marc, I think the ccs, the only remaing difference, really is not audible. Maybe using the WPS/Amphenol jack instead of your jack is a more likely difference._

 

I haven't spent enough time sorting the switches, but I think I'm going to use a PVA with 1:2 trafos and basically a shunted pot behind it. Nobel 10K for the pot. I don't have any balanced sources yet, so most of the time it will be fed by SE, when a Balanced source is available, I'll just bypass the trafos. They'll actually be part of a pre-amp that will also feed my F5(s). 

 For guys using the eXstata with electrets like the SR-30 and SR-40, how far are you pushing the volume? Are you concerned about over-voltage? I have ATH7s (SR-30s) on the way with eyes on another 'tret and AT-706s and KH-82s already in the house. The AT-706s are playing very quietly relative to the volume on my CR-620 compared to the KH-82s and SR-Lamda through a SRD6. I used Deoxit in the AT transformer box switches and contacts on the socket/plug and that helped, but they distort and clip pretty quickly after getting to a listenable level. I knew they were quiet cans when I bought them and did so mainly for the transformer box to use with the KH-82s after mods to Stax jacks and a recable on the KH-82... 

 I'm tempted to reterminate the 706 cable to a Stax plug and try them through the SRD6 before I mod the AT box...


----------



## ericj

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_For guys using the eXstata with electrets like the SR-30 and SR-40, how far are you pushing the volume? Are you concerned about over-voltage? I have ATH7s (SR-30s) on the way with eyes on another 'tret and AT-706s and KH-82s already in the house. The AT-706s are playing very quietly relative to the volume on my CR-620 compared to the KH-82s and SR-Lamda through a SRD6. I used Deoxit in the AT transformer box switches and contacts on the socket/plug and that helped, but they distort and clip pretty quickly after getting to a listenable level. I knew they were quiet cans when I bought them and did so mainly for the transformer box to use with the KH-82s after mods to Stax jacks and a recable on the KH-82... 

 I'm tempted to reterminate the 706 cable to a Stax plug and try them through the SRD6 before I mod the AT box..._

 

I have SR-30 and SR-80 'trets but i haven't listened to them with the eXStata prototypes. I can give it a try. 

 Last year or so there were some pics of the inside of a Signet electret that make it appear that Stax and Audio-Technica were sourcing electret drivers from the same production line, so, there's a good chance the AT-706 can be driven just fine by the eXStata.


----------



## jpancier

I'm also interested in trying my hand at this. I'm in love with my stats, and this would be a good complement to my setup. Where do we get in line for the boards?


----------



## pabbi1

WRT SR-40, that is what I use to test my builds, and had them at the DFW meet. Through the proto, I think I've taken it to about half attenuation without any issues, but haven't noticed anything nasty.

 Cranked up Audioslave, AC/DC 'Powerage', and Velvet Revolver last night on the he60 - no clip. So, just Tool and Monster Magnet are my problem children, but not on every cut.

 Now, to build the new mini-rack for the new source.


----------



## luvdunhill

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Now, to build the new mini-rack for the new source._

 

sweet, and sweet! what are your plans for the rack? is the dovetail jig involved?


----------



## bidoux

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_I have SR-30 and SR-80 'trets but i haven't listened to them with the eXStata prototypes. I can give it a try. _

 

It would be really sweet as I only have a SR-30 which is waiting for its exstata.


----------



## pabbi1

No, the dovetails are for the new Vulcan case... gotta resize that koa... 

 Actually, it really is a shame, as the surface now is granite, and I'm of two minds - either find scrap granite (the sink or stove cutouts from countertops are GREAT for this, and many are to be found on CL), or go old school. Taking inspiration from Nate, so, getting some 8/4 mahogany or walnut for the base, and using 7/8 allthread 12" rods, attach a matching 1" shelf, neting 8.5" clearance. 

 Total size is 21" x 16", the same base as now. The nuts and bolts were ~$25, and the wood will be about $50ish. Now there is a guy locally that has some 11/4 21" x 60" Mesquite that would be a killer - tools, back, you name it. There are some really nice flame maple boards on the bay, but maybe WoodWorld will have something more fun, like cocobolo, bocote or even some more birdseye maple. Depending on material, this will add about 30-40lbs of mass to the structure. 

 The only DIY sickness more intoxocating than electronics is the woodshop, not to mention shopping for exotic lumber.

 Which reminds me, Dr Wood was gonna instruct me in the ways of a failproof box joint (nudging me toward dovetail nirvana)... perhaps he realized the futility.


----------



## luvdunhill

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Which reminds me, Dr Wood was gonna instruct me in the ways of a failproof box joint (nudging me toward dovetail nirvana)... perhaps he realized the futility._

 

nah, I reminded him of a project that he's been working on for me for... 2 years almost to the day 
	

	
	
		
		

		
			





 That should keep him busy for a little while. After cutting him a sizable check for a large lot of solid Maple lumber, we'll see how it turns out


----------



## BoilermakerFan

Man, this talk of granite, maple, and walnut has to stop! I can't think of a better combo than maple, walnut, and green granite. 

 I need to finish other projects including the eXstatas before I even think about building a DIY rack and turntable. But no, I also had to see the turntable.it site on 6moons with their relatively simple to mill tone arm design. Then wualta had to mention modding platters from old idler wheel mastering TTs in the ortho forum a few weeks ago... All the missing pieces are in place, except the final design. The TT was the last remaining piece to design for my DIY or highly modded system. 

 Hey Pabbi, how about Mopani for the shelves? That has got to be the heaviest 2x6x6 block of wood I've picked up! Might be too heavy even for ortho cups. I'll definitely have to use it for the inner plinth on my TT.


----------



## pabbi1

Just got back from the wood store with 70 lbs of jatoba... for.the.win. Almost as heavy as rosewood, but nowhere near as oily. Pictures this evening.

 If the sound doesn't motivate people, maybe the pretty wood cases will...


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Just got back from the wood store with 70 lbs of jatoba... for.the.win. Almost as heavy as rosewood, but nowhere near as oily. Pictures this evening.

 If the sound doesn't motivate people, maybe the pretty wood cases will... 
	

	
	
		
		

		
		
	


	


_

 

Jatoba is 56 pounds per cubic foot, S.A. Rosewood is 44 pounds per cubic foot. Mopani is 77 pounds per cubic foot... 
	

	
	
		
		

		
		
	


	




 EDIT: The Madrone and rosewood are for dry wood at 12% M.C. I didn't see if the Jatoba was green or 12%.


----------



## cfcubed

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_What I detest is using an ALPS rk27, regardless of the number of decks. This amp deserves better._

 

OT & no need to dive in, but I guess you'd detest most all of my builds
	

	
	
		
		

		
		
	


	



 In particular, the balanced/4-ch b22 I've stumbled into completing... Can't yet bring myself to spend $250 USD or so on balanced volume control (yet) 
	

	
	
		
		

		
		
	


	




 But attenuation is a whole 'nother ball of wax.


----------



## pabbi1

I'll try to phrase in a more positive manner - the first upgrade opportunity in any build is when you have used a rk27. Just a preference that I have developed after using a dozen rk27 flavors over the years. 

 Anyone with more impressions? Nick, get your he60 bits?

 If I calc right, my mini rack will be .7 ft³, so with thread and bolts, it will be a svelt 45lbs... OY!


----------



## studeb

Quote:


  Originally Posted by *bidoux* /img/forum/go_quote.gif 
_It would be really sweet as I only have a SR-30 whiwh is waiting for its exstata._

 

I have used the SR-60 with the amp, it is fine.
 i did notice lower sound pressure with the SR-60 compared to the SR-X

 you should be fine


----------



## M3NTAL

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_I'll try to phrase in a more positive manner - the first upgrade opportunity in any build is when you have used a rk27. Just a preference that I have developed after using a dozen rk27 flavors over the years._

 

It is unfortunate that the Rk27 is one of the only sub $100 pots available in 4 channel configuration that is "easy" to get a hold of as a normal consumer.

 I really love the feel of an analog pot with some heavy weight on it. A joshua tree or optivol are other options, but still end up costing more in money and time.


----------



## pabbi1

Yes, sad that Khozmo could not get their act together. The market for really good attenuators really is hungry for a nice solution.


----------



## cfcubed

Quote:


  Originally Posted by *M3NTAL* /img/forum/go_quote.gif 
_It is unfortunate that the Rk27 is one of the only sub $100 pots available in 4 channel configuration that is "easy" to get a hold of as a normal consumer._

 

The Attenuator talk thread might be a good place to bring this.. But yes, after some recent googling (& nearly trying RelVol3 before hearing about possible click/mute issues), I've sortof come around to using 4-ch RK27 w/possible/pricey upgrade to HeadAmp offering.


----------



## manaox2

I've been eyeballing the goldpoint mini-v stepped attenuator over the DACt CT-4 quad.


----------



## jcx

the point of my previous post was that there is little reason to want/need 4-channel attn with eXstata - with balanced or se source

  Quote:


  Originally Posted by *jcx* /img/forum/go_quote.gif 
_I hate to see so much mental energy and money wasted on balanced input for the exstata - having a high impedance differential front end it can accept single ended signals and still give the same output performance - up to the limitations of its low loop gain and consequent sensitivity to matching just about all of its components

 it is unlikely that enough have been built that that even one exits (by statistical chance) that actually would give a "better balanced" output with balanced input vs single-ended input given device and component parameter distributions - that are not being measured/matched/trimmed

 even with balanced source you could save money with dual attenuators with little to worry about in loss of "sound quality"_

 

and earlier:

  Quote:


  Originally Posted by *jcx* /img/forum/go_quote.gif 
_Some wrong and misleading info being tossed around this thread re gain and balanced/single ended here

 The amp is a true differential amp, there is a single gain # applied to Vin difference – it doesn’t matter whether the input is SE or dual polarity/balanced with respect to gnd

 With 500:1 feedback resistor ratio the differential gain would be 1001 (assuming high enough loop gain - which the circuit doesn't have)

 There is also a small common mode gain of ~1x

 With “balanced” input the a,b stator drive signals would be +,-500.5x 

 With SE signal, - input gnded, stator a would see +501x, b –500x

 The trivial gain imbalance w/SE drive is much smaller than component tolerances – you’d need better than 0.1% tolerance feedback R and > 1e6 open loop gain for these errors to become the same order of magnitude – you could buy or match the feedback resistors but you need more active devices to get the open loop gain

 Just to spell it out in small words - - this amp doesn’t need/won’t benefit from balanced vs SE input signal -- worrying about balanced input is completely myopic audiophilia nervosa_


----------



## les_garten

Heard ya the first time. 

 No real need to make a post quoting yourself


----------



## BoilermakerFan

So why not just use an SE OptiVol or Nobel in a shunted Pot config? Use nice boutique resistors of your choice, Rikens, Caddocks, Dales, Holcos and you're still under $50 and can get that down to under $30 with Holcos... 

 Going with a lower R value puts less input impedance variance on the amp and the PVA transformers are optional if you don't want the gain (and we don't need it on the eXStata), but they let the source see a constant load. The catch with the OptiVol is it needs a power source, but it draws 100mA or less. Can't really steal the power form the standard transformers in either eXStata build, but a tiny Hammond or similar would work.


----------



## pabbi1

N/m


----------



## jcx

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_Heard ya the first time. 

 No real need to make a post quoting yourself_

 

3 posters looking for 4 channel atten on the previous page seemed reason enough for me to reiterate and bring to the fore a buried (>1500 posts ago) technical argument

 I'm trying to initiate a discussion of the technical issues - how about your not worrying about someone else's posting style, particularly those with less than 0.2% of the thread's post count




 when the project goal is a cost effective amp it seems valuable to examine an option that does not appear to have a obvious/predictable (deleterious) effect on sound quality and that does reduce cost, increases builders' options and eases part availability


----------



## pabbi1

Quote:


  Originally Posted by *jcx* /img/forum/go_quote.gif 
_3 posters looking for 4 channel atten on the previous page seemed reason enough for me to reiterate and bring to the fore a buried technical argument

 I'm trying to initiate a discussion of the technical issues - how about your not worrying about some else's posting style, particularly those with less than 1% of the thread's post count


 When the project goal is a cost effective amp it seems valuable to examine an option that does not appear to have a obvious/predictable (deleterious) effect on sound quality and that does reduce cost, increases builders' options and eases part availability_

 


 Yawn - open your own thread. And, I don't see anything in your post regarding eXStata that you couldn't tilt in virtually any balanced / differential thread. Your desire to 'initiate' something seems fairly hostile and counterproductive to the 20 or so rather experienced builders here, with a few rookies.


----------



## les_garten

Quote:


  Originally Posted by *jcx* /img/forum/go_quote.gif 
_3 posters looking for 4 channel atten on the previous page seemed reason enough for me to reiterate and bring to the fore a buried (>1500 posts ago) technical argument

 I'm trying to initiate a discussion of the technical issues - how about your not worrying about someone else's posting style, particularly those with less than 0.2% of the thread's post count




 when the project goal is a cost effective amp it seems valuable to examine an option that does not appear to have a obvious/predictable (deleterious) effect on sound quality and that does reduce cost, increases builders' options and eases part availability_

 

You made your point the first time. Sorry you were ignored. That's no reason to bring it up again. Starting your own thread seems like a great idea. You've made your point twice now.


----------



## Beefy

Quote:


  Originally Posted by *jcx* /img/forum/go_quote.gif 
_3 posters looking for 4 channel atten on the previous page seemed reason enough for me to reiterate and bring to the fore a buried (>1500 posts ago) technical argument

 I'm trying to initiate a discussion of the technical issues - how about your not worrying about someone else's posting style, particularly those with less than 0.2% of the thread's post count_

 

The solution to the problem isn't to just give up on balanced attenuation, but to find a better option for balanced attenuation.

 And the assumption that everybody is just going after balanced for some audio-peen is silly. My DAC has 1 set of balanced and 1 set of unbalanced outputs. The unbalanced outputs feed my M3, the balanced outputs remain unused...... why would I _not_ use these for the Exstata?

 *

 So back the to the original discussion.

 For my money - less than $50 - a dual PGA2320 controller is just perfect. Excellent channel matching, no drift over time, no mechanical connections. Some people would be afraid of the fact that it is essentially an OPAMP in the signal path...... but considering everything of mine is solid state, I couldn't care less


----------



## cfcubed

We should leave this, but as one of the attenuator "tangentors" I side w/jcx here. Certainly attenuators were more OT than the points he's trying to make, even if other threads may be best for both. Can see how it seemed the topic/value of his recent posts was lost in a largely OT tangent. There's detailed, relevant info in those posts.

 Having tried to keep CTH threads on-topic; it's a difficult & worth-while thing to do.
 I'll exit here as I've no eXStata-specific stuff to discuss


----------



## pabbi1

Moving way on, anyone else have observations OR, mod ideas?


----------



## minivan

is dual mono power supply possible? can the amp handle that much power?


----------



## digger945

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_So why not just use an SE OptiVol or Nobel in a shunted Pot config? Use nice boutique resistors of your choice, Rikens, Caddocks, Dales, Holcos and you're still under $50 and can get that down to under $30 with Holcos... 

 Going with a lower R value puts less input impedance variance on the amp and the PVA transformers are optional if you don't want the gain (and we don't need it on the eXStata), but they let the source see a constant load. The catch with the OptiVol is it needs a power source, but it draws 100mA or less. Can't really steal the power form the standard transformers in either eXStata build, but a tiny Hammond or similar would work._

 

Could I trouble you for a link to those PVA transformers you are referring to, please sir?
 I'm interested. Thanks kindly.


----------



## luvdunhill

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Could I trouble you for a link to those PVA transformers you are referring to, please sir?
 I'm interested. Thanks kindly._

 

Don't you have another attenuator to be building 
	

	
	
		
		

		
		
	


	




 Anyways, I'll take a shot:

Electra-Print.com PVA Passive Audio Pre-Amplifier

 but, there are others out there:

intact audio

 My favorite are bifilar wound TVC for use in balanced applications. Basically two of the above on a single core. But as far as I know, the only real options are customs, which is the route I went.


----------



## digger945

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Don't you have another attenuator to be building 
	

	
	
		
		

		
		
	


	


_

 

Um, yea, I need to get cracking on that don't I.

  Quote:


 Anyways, I'll take a shot:

Electra-Print.com PVA Passive Audio Pre-Amplifier 
 

Oh, yea. That's the one that is mentioned earlier in the thread I believe. Thought it was something new.

  Quote:


 but, there are others out there:

intact audio 
 

Yea, I go there and eyeball those every so often.
 The pics of the Slagleformers have been removed from the bentaudio site, so I need some pron from time to time. You know.
  Quote:


 My favorite are bifilar wound TVC for use in balanced applications. Basically two of the above on a single core. But as far as I know, the only real options are customs, which is the route I went.





 

I've seen these somewhere else before. hmm.


----------



## BoilermakerFan

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Don't you have another attenuator to be building 
	

	
	
		
		

		
			





 Anyways, I'll take a shot:

Electra-Print.com PVA Passive Audio Pre-Amplifier
_

 

Yes, Marc, those are the ones I will be using, but only in a 1:2 for the F5s. Haven't decided if I'll do 1:1 for the eXStata, or just bypass the transformers for the eXStata. 

 In the past two weeks or so my electret collection has swelled to four and I have the SR-Lamdas. All the electrets are being reterminated to Stax plugs so I can use the SRD6 and eXStata for them. Still need to finish my DIY SRD7 with the huge E-P iron too, just to have one more route to compare the eXStata with. Balanced F5s feeding the DIY SRD7 should be interesting, though I know it will still be no match for the eXStata. I'll build it and give it to my dad with one of the electrets after I do the listening comparos.


----------



## Emooze

Quote:


  Originally Posted by *minivan* /img/forum/go_quote.gif 
_is dual mono power supply possible? can the amp handle that much power?_

 

Because the dynamic current draw is so low and that the PS is a shunt type, I'm not sure if the amp would benefit or the power supply would like the decreased load.


----------



## runeight

Checking in on you boys again.

 All seems to be going well for everyone except that some of you are taking forever to actually build the amp. 
	

	
	
		
		

		
		
	


	




 Dual mono supplies won't help for the reason emooze stated. There is little dynamic current draw and the shunt regulators are pretty good and keeping the rails steady and you'll probably overload the shunt devices with too much current.


----------



## bidoux

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_All seems to be going well for everyone except that some of you are taking forever to actually build the amp. 
	

	
	
		
		

		
		
	


	


_

 

Holydays begins tomorrow, I should start to build it on Monday but I'm not sure if it will be finished before summer. 
	

	
	
		
		

		
		
	


	




 Also, I was wondering if it is possible to solder phoenix terminal connectors for power TO-220 transistors. Anyone have a clue ?


----------



## BoilermakerFan

Quote:


  Originally Posted by *bidoux* /img/forum/go_quote.gif 
_Holydays begins tomorrow, I should start to build it on Monday but I'm not sure if it will be finished before summer. 
	

	
	
		
		

		
		
	


	




 Also, I was wondering if it is possible to solder phoenix terminal connectors for power TO-220 transistors. Anyone have a clue ?_

 

They make specialty sockets for the TO-220s. Personally, I wouldn't use screw terminal blocks for the TO-220s.


----------



## Beefy

Personally, I wouldn't socket them at all. Not with these high voltages anyway. What would you hope to achieve?


----------



## bidoux

Having to desolder a burnt transistor and solder a new one is one of my fears, espeacially because I could destroy the PCB this way.


----------



## adamus

cut the legs off and pull them out individually = no pain.


----------



## Sathimas

I just finished soldering the power supply - really great feeling 
	

	
	
		
		

		
		
	


	




 Amp board is next ...

 The only problem is that neither the transformer nor the stax-jack have arrived yet but I'm full of hope to get the first tunes out of this amp before March.


----------



## macm75

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_New PT is in. Better but still not at the specified T1/T3 values. I now have 315V on T1 and 312V on T3. T1-T2 and T3-T4 are steady at 360/410mV. 
 I'm assuming I'm out of luck with my free-bee's but... 
 instead of replacing a PT, can I replace my 91V zeners with say ~80V and run B+ at -290V and +290V. Surely the circuit does not care about 10V difference in supply voltage._

 

So after couple weeks my new zeners, the ones that had to travel 20 miles, finally arrived. Given the lower voltage on the front PS caps, I replaced the 91V zeners with 75V. 
 Question is do I have to go back and perform P1 and P2 adjustments? With a lower zener string should I still be looking for 360mV at T1-T2 and 410mV at T3-T4? If I have to make the adjustments again can I do this with the real circuit or go back to dummy load?
 Thank You!

 Progress (actually started the real case yesterday during the snowfall - we had over 3 foot in the last week):


----------



## Beefy

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_cut the legs off and pull them out individually = no pain._

 

This.

 And resistors and capacitors are just as capable of failing catastrophically, but you wouldn't try and socket these.


----------



## manaox2

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_All seems to be going well for everyone except that some of you are taking forever to actually build the amp. 
	

	
	
		
		

		
		
	


	


_

 

Mouser order will ship on 3/10 by part arrival estimate, should have all parts ordered and finally be able to build this as soon as they arrive; still need to decide upon an enclosure and attenuator.


----------



## Emooze

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_All seems to be going well for everyone except that some of you are taking forever to actually build the amp. 
	

	
	
		
		

		
		
	


	


_

 

Mine has been finished but un-presentable since Thanksgiving:






 Should finally have my case in hand tomorrow so I can bring it to the Massachusetts area meet.


----------



## tomytank

I've had mine running for a few weeks, but it's still in the basement, until I can finally finish the case. 

 Having never built an amp case before, I didn't realise how long it takes.....plus I had some bad luck and will have to pick up some more supplies to complete it. 

 The base is done though.


----------



## paxeaxe23

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Checking in on you boys again.

 All seems to be going well for everyone except that some of you are taking forever to actually build the amp. 
	

	
	
		
		

		
		
	


	




 Dual mono supplies won't help for the reason emooze stated. There is little dynamic current draw and the shunt regulators are pretty good and keeping the rails steady and you'll probably overload the shunt devices with too much current._

 

I have started to build, but am still waiting for a my Alps Pot and a few components to arrive before I can finish it. Still, its Karnival here in Germany, so I now have 4 days of peace - not quiet - to get on, so lets hope I get a couple of packages in the post in the morning!


----------



## Beefy

I know that a lot of people in this thread bought Stax jacks from luvdunhill......

 I'm measuring the diameter of the jack as 22.32-22.34mm. Can anybody confirm this measurement of jacks in the wild?


----------



## pabbi1

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I know that a lot of people in this thread bought Stax jacks from luvdunhill......

 I'm measuring the diameter of the jack as 22.32-22.34mm. Can anybody confirm this measurement of jacks in the wild?_

 

Yes mine fit snugly in the hole drilled with my 7/8" forstner, so that sounds dead on - 22.25 + wobble...


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Yes mine fit snugly in the hole drilled with my 7/8" forstner, so that sounds dead on - 22.25 + wobble... _

 

Nice I have a 7/8" stepper Uni-Bit and a 7/8" knock-out punch. I'll see which one works best.


----------



## Lou Erickson

I believe I have all the parts ordered for the solid state, and almost all the parts for the hybrid. My NABUs arrived today, and pots are on the way. Hopefully I'll be able to do a little assembly on Monday!


----------



## Michgelsen

Quote:


  Originally Posted by *tomytank* /img/forum/go_quote.gif 
_I've had mine running for a few weeks, but it's still in the basement, until I can finally finish the case. 

 Having never built an amp case before, I didn't realise how long it takes.....plus I had some bad luck and will have to pick up some more supplies to complete it. 

 The base is done though. 
	

	
	
		
		

		
			



_

 

Looks great! I like it that the layout is similar to a Stax amp.


----------



## macm75

It's running - finished initial amplifier offset and balancing. I'm on the first half hour waiting step - so far so good!!!


----------



## pabbi1

Welcome to the club - hope you enjoy the stay.


----------



## tomytank

More bad luck. Second perspex top has broken. I think bending it at the sides introduces too much stress, and any additional working causes it to crack.

 Or I need more experience, or more skill. (Or more Perspex! 
	

	
	
		
		

		
		
	


	




 ) 

 Maybe I should go all wood? (Wood is good. I've got lots of it, and it's easier to work with.)


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomytank* /img/forum/go_quote.gif 
_More bad luck. Second perspex top has broken. I think bending it at the sides introduces too much stress, and any additional working causes it to crack.

 Or I need more experience, or more skill. (Or more Perspex! 
	

	
	
		
		

		
		
	


	




 ) 

 Maybe I should go all wood? (Wood is good. I've got lots of it, and it's easier to work with.)_

 

How are you trying to bend it? The best way is to heat it evenly in a oven over a wood shaped form. Or you can use a big space heater that flows enough hot air, but most of them now have safety shut-offs if they tilt beyone 15degrees from upright. 

 That's a really thick piece too, looks to be 6mm or more, that will take some time to heat, soften and then finally bend.


----------



## les_garten

Quote:


  Originally Posted by *tomytank* /img/forum/go_quote.gif 
_More bad luck. Second perspex top has broken. I think bending it at the sides introduces too much stress, and any additional working causes it to crack.

 Or I need more experience, or more skill. (Or more Perspex! 
	

	
	
		
		

		
		
	


	




 ) 

 Maybe I should go all wood? (Wood is good. I've got lots of it, and it's easier to work with.)_

 

I think it looks sharp. Fall Back, Regroup!

 Don't change horses yet. Wood and Plexi, nice combo!


----------



## Lou Erickson

Time for me to ask a dumb question.

 I'm trying to match the jfets (Q1 and Q2). I've got a pile of J271s, a DMM, and a 12v wall wart.

 I'm trying to follow the directions at The eXStatA Electrostatic Amplifier which looked simple enough.

 I never get a reading on the DMM, though. I've got to be doing something wrong.

 Here's my understanding:

 According to the package, the J271 is a P Channel transistor. So, I need to use the diagram on the right. G and S, which are the two outside pins, go to +12. D, the middle pin, goes to + on the meter. - on the meter goes to ground.

 My idea of which pin is which came from a document at Fairchild. Have I read that right?

 Can someone confirm I'm doing this right, or what I might be doing wrong?


----------



## tomytank

@BoilermakerFan

 It's 3mm perspex. I'm using only what I've got, unfortunately, a hot gun with the perspex clamped upright into a wood bench. Measure, mark, secure. 
 Being very careful with the distribution of the heat from the nozzle. I heat and wait for the perspex to sag, then bend and clamp with an additional wood brace, until cool.

 @les_garten

 So far, I have a bunch of offcuts and scraps, and a final sheet of perspex to try once more. 

 I may give it another go!

 @Lou Erickson

 If you get no meter reading at all: check your DMM fuse. This happened to me, and it was baffling. 
 Made me go out and buy a 'proper' DMM with a reset-able fuse.


----------



## runeight

Quote:


  Originally Posted by *Lou Erickson* /img/forum/go_quote.gif 
_Time for me to ask a dumb question.

 I'm trying to match the jfets (Q1 and Q2). I've got a pile of J271s, a DMM, and a 12v wall wart.

 I'm trying to follow the directions at The eXStatA Electrostatic Amplifier which looked simple enough.

 I never get a reading on the DMM, though. I've got to be doing something wrong.

 Here's my understanding:

 According to the package, the J271 is a P Channel transistor. So, I need to use the diagram on the right. G and S, which are the two outside pins, go to +12. D, the middle pin, goes to + on the meter. - on the meter goes to ground.

 My idea of which pin is which came from a document at Fairchild. Have I read that right?

 Can someone confirm I'm doing this right, or what I might be doing wrong?_

 

If you meant what you said about the pins, please check the data sheet for the pinouts. If not, make sure that your meter is not in diode mode when trying to read the current.

 Yes, I know, a voice from the darkness......


----------



## paxeaxe23

OK, another Dumb question. On Alex's site the instructions say to mount all vertical diodes with cathodes up and anodes down. The diagram shows the painted ring which marks the cathode as the upper end. However as far as I read it on the boards (Power supply is what I'm doing right now) the thick white line (which I assume is the cathode), appears to be on the white circle (which I assume is the hole for the diode) so I would have ordinarily mounted the diodes with the cathode (Black or grey ring) down.

 Can someone clarify this for me. Maybe I'm just reading the board wrong. I certainly don't want to make a mistake at this stage of my first big (for me anyway) project.

 Thanks


----------



## Beefy

The round marking on the board is where the 'body' of the diode goes. The thick line points to the adjacent hole where the bent leg goes. Ring on the diode/cathode goes up.


----------



## paxeaxe23

Thanks Beefy, after taking a second look, I see what you mean.

 Before I mount the zener strings, I have another question. I'm going to use two Triad transformers as from the BOM for the SS version. There has been some discussion on needing to have 300V Zener string for the 250-0-250 Transformers. I do have a few extra 100V zeners. I sthere any advantage/disadvantage of using 3 x100V zeners instead of the 2 x100V and 1 x 91V Zeners for me. 

 Thanks again


----------



## BoilermakerFan

Quote:


  Originally Posted by *tomytank* /img/forum/go_quote.gif 
_@BoilermakerFan

 It's 3mm perspex. I'm using only what I've got, unfortunately, a hot gun with the perspex clamped upright into a wood bench. Measure, mark, secure. 
 Being very careful with the distribution of the heat from the nozzle. I heat and wait for the perspex to sag, then bend and clamp with an additional wood brace, until cool._

 

No option to put it in the oven at 300degF-350degF (150-175degC)? You could probably take it up higher from there, but start lower, around 200degF and slowly bring it up. You can then move it quickly to the workbench and add more heat to the bend area, but you've pushing it too much at a time when it's cold. 3mm is actually really easy to bend if you take it slowly. Clamp it horizontally on the bench. If you don't want a 90deg. bend, lift up or raise the back side with spacers to get to your approximate angle when the piece drops vertically down off the bench by gravity. Heat the piece as evenly as you can, but have the approximate bend line a little over the edge of the bench. Then heat it evenly and let it drop 1-3cm at a time, and heat a wider area of the Perspex in order to relieve the build up stress risers in the plastic. You have to relieve the stress further to each side of the bend than you think otherwise it will keep cracking as it cools or as soon as you handle it which causes the slightest stress to the material.


----------



## Lou Erickson

@tommytank:

 Good call! After all my screwing around, I had managed to blow the fuse in my meter. There's a spare, and I'll have to get some more.

 @runeight:

 I was so careful when reading the pages, and still got it entirely wrong. A google search for the pinout, or to use the sheet off Mouser instead of the more complex (and apparently irrelevant) one from Fairchild themselves finds a very different pinout, which reads sensibly.

 When measuring, I get a value which starts in and then begins dropping... should I use the initial value, or wait for it to stabilize? (Will it stabilize?)


----------



## fierce_freak

Does anyone have a cheap pair of pro bias stats for testing that they'd be willing to let go of?


----------



## pabbi1

I always use electrets (SR-40) just to keep bias out of the initial equation - and, very cost effective.


----------



## TimJo

After careful measurements from the DMM, I just plugged my 404LE's in, putting trust in the design. It worked. 
	

	
	
		
		

		
			





 But maybe that's foolish, I'm not sure... It's true I always test a dynamic amp with apple earbuds. Hmmm...


----------



## Emooze

Quote:


  Originally Posted by *paxeaxe23* /img/forum/go_quote.gif 
_Thanks Beefy, after taking a second look, I see what you mean.

 Before I mount the zener strings, I have another question. I'm going to use two Triad transformers as from the BOM for the SS version. There has been some discussion on needing to have 300V Zener string for the 250-0-250 Transformers. I do have a few extra 100V zeners. I sthere any advantage/disadvantage of using 3 x100V zeners instead of the 2 x100V and 1 x 91V Zeners for me. 

 Thanks again_

 

If you are using the Triads, you don't need to do the 300V zener string. My SS is working perfectly with the Triads and a 291V string. I'm not sure if there is any benefit for doing one over the other though.


----------



## runeight

Quote:


  Originally Posted by *Lou Erickson* /img/forum/go_quote.gif 
_@tommytank:

 Good call! After all my screwing around, I had managed to blow the fuse in my meter. There's a spare, and I'll have to get some more.

 @runeight:

 I was so careful when reading the pages, and still got it entirely wrong. A google search for the pinout, or to use the sheet off Mouser instead of the more complex (and apparently irrelevant) one from Fairchild themselves finds a very different pinout, which reads sensibly.

 When measuring, I get a value which starts in and then begins dropping... should I use the initial value, or wait for it to stabilize? (Will it stabilize?)_

 

Use the initial value as soon as you get the reading. Try not to heat the devices by grabbing them with your fingers.


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Use the initial value as soon as you get the reading. Try not to heat the devices by grabbing them with your fingers._

 

This is definitely the way to go about it. It's possible to pick up, and plug the device into a protoboard without using your fingers, it just takes some practice. Also, avoid sitting under an HVAC duct in your house


----------



## Sathimas

The boards 99% finished, only the matched transistors are still missing.
 (A friend does this for my as he has all the equipment at work)

 Now everything could be ready for testing by tomorrow or so - but the company where I ordered the transformer called today to tell me they made a mistake and forgot the center tap.
 So now its only a 500V transformer...

 The customer service will call me later this day to set the next steps ...

 Whish me good luck that the third try to get a fitting transformer will be the last!






 I put the boards there to make them familiar with some of my favourite records :-D


----------



## fierce_freak

lol, nice


----------



## Beefy

Well I ordered my FPE panels last night...... should have them in just over two weeks. So in a three week time frame my Exstata should be 100% done!


----------



## Scooba

I hate to intrerupt again. Does anyone have a spare set of PCB's ? Please ?
 (I have already asked Alex, and he does not have any left).


----------



## macm75

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Welcome to the club - hope you enjoy the stay. 
	

	
	
		
		

		
		
	


	


_

 

It's officially alive!! I listened for about an hour and very much like what I hear. Like many of you and audio, I'm not easy to please but right off the bat the eXStata is proving to be a fantastic amplifier. I'll admit I've had these SR-303's for three years now and they have been played for merely hours. I've built 3 versions of Andrea Ciuffoli amp design and was never really pleased. Thought about selling them (303's) many times, would have taken too big a $ hit and kept them. Alex's amp saves them (although Alex's amp also kept me from completing my Gilmore "All-Triode" amp - should have a comparison soon). 
 No matter what I give it, I find the soundstage, instrument separation, air, and, in particular, layering of sounds to be absolutely superb. Amp is dead quiet and provides a black background for the music. I'm also pleased with the weight of the notes, dynamics, and detail from top to bottom - given the 303's, hard to believe one could get more out of them. For better sound, a source or headphone upgrade would be required - this amplifier is the strong link.
 I'll have more to say in the upcoming weeks. Real case is in progress and my All-Triode amp (it actually ran for an hour before a part blew up on the PS) will be complete soon. For now I cannot thank Alex enough for the design, documentation, and PCB’s - a tremendous effort and a pure gift for our enjoyment.


----------



## pabbi1

Welcome aboard! I have found it really raises the lower Stax models (considerably), and takes nothing away from the upper ones, well, the ones I can comment on somewhat objectively.

 Congratulations - looks like I'm sending the proto to yet another person to join the club, so maybe he'll chime in with some impressions this weekend.

 Oh, and I'll have a new source by then...


----------



## macm75

Think there is point to adding extra holes on the base of box for ventilation? You can see the existing holes on the base. For the top, I simply plan on taking a piece of plexiglass (or acrylic if I can ever find a piece cheap enough) and raising it above the top of box by a 1/4" or so using 4 spacers - lots of ventilation for top.


----------



## digger945

Are you related to Al?
 That looks very nice.
 Home Depot or Lowes will cut plexy to your size at no charge. The stuff aint cheap at those places but it is (almost) instant gratification. I have used one of those plexy knives from Ace hardware with so-so results. I think I should have scored the stuff some more before trying to break it.


----------



## macm75

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Are you related to Al?_

 





 So I glanced back at Al's amp and see a bit of what you mean. Although he used prettier wood. Actually, thanks for the reference because I also see Al did not drill holes to his base plate.


----------



## ktm

After scrounging local sources, I have soldered in everything I have here.
 I just finished ordering all the other parts I need and ordered a Nabu case.
 I guess I'll have to drill a lot of holes for airflow. The front will be a tough call
 how to finish it out. Wood or metal? I have waited on the jack. At this point 
 I'm looking at salvaging a 6 pin Stax jack out of my srd-4, and plugging the center
 pin. The 40's will become test cans. Time for some hybrid goodness to
 join my collection. Maybe in the next month or so the other Stax amps will be 
 finding a new home.
 Thanks again, Al, for hooking me up!


----------



## macm75

Quote:


  Originally Posted by *ktm* /img/forum/go_quote.gif 
_Wood or metal?_

 

Do a search in this thread for Nabu and I believe you will find a recommendation by Al for exotic woods to cover your metal front panel. Wood is always better looking and more interesting than metal if you ask me.

 Edit: Found it... http://www.head-fi.org/forums/6292717-post1963.html


----------



## pabbi1

Yeah, how can you beat something like this, or perhaps a better fit, or almost perfect size.

 The greatest thing about the Nabu is that the plastic face doubles duty as a perfect drill template for a wood panel. 1/4" is really too thick for pots and such, but, Dremel cures all.

 Now I do take offense to the notion that I'd use a domestic wood (other than to prove a point, but I do have some scrap English brown oak left over from my dart board, which would make an awesome case... if only I could conquer some form of corner jointery (dovetail, boxjoint, etc). Damnit, time to take a class. 
	

	
	
		
		

		
		
	


	




 So, any further listening impressions ya'll? Nick, the suspense is killing me...

 Edit: If you can't find the jacks at Allied, Alex (APS) still has some Amphenol jacks, or did at last check.


----------



## sergery

What is the new source you are waiting on Al? The suspense is killing me too... I may just deal direct with Sennheiser in Germany if Customs doesn't turn over the goods soon.


----------



## awpagan

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_It's officially alive!! Alex's amp saves them (although Alex's amp also kept me from completing my Gilmore "All-Triode" amp - should have a comparison soon). 
 ._

 

I now have the transistor version working now,been listening for about a day.
 Well done Alex, very sweet sounding amp
	

	
	
		
		

		
		
	


	





 Had the Gilmore triode for a while now, it sat in the background for a far while.
 Female voices with instruments were fantastic on it but the lows/bass were always fluffy.
 I,ve abandoned the Gilmore "All-Triode" amp now

 Now to do the tube/Hybrid version.
 Also waiting for a pot to run balanced, SE at present.
 Stax Lambda low bis version, "very old"


----------



## pabbi1

Quote:


  Originally Posted by *sergery* /img/forum/go_quote.gif 
_What is the new source you are waiting on Al? The suspense is killing me too... I may just deal direct with Sennheiser in Germany if Customs doesn't turn over the goods soon._

 

Edit: Actually an Ayon CD-1... just didn't need any complications on Agon until the deal was completed. of course, it is not actually completed until it's actually sitting on the new jatoba plexi rack...


----------



## macm75

Quote:


  Originally Posted by *awpagan* /img/forum/go_quote.gif 
_Had the Gilmore triode for a while now, it sat in the background for a far while.
 Female voices with instruments were fantastic on it but the lows/bass were always fluffy.
 I,ve abandoned the Gilmore "All-Triode" amp now_

 

This concerns me too - man a lot of time and effort went into it (luckily it was built with virtually all spare parts). In my above post I mentioned it ran for only an hour before I saw a bright flash on my back wall (PS issues). I hate to say it but I heard the same thing. Thought maybe it was the PS or the vitamin Q caps but it sounds like, based on your confirmation, maybe not.
 I was on the beta 1 team and dropped out due to the All-Triode build. I had a lot of PS issues with it, lost confidence, and joined the beta 2 team. Looks like I made a good decision.


----------



## FrankCooter

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_.. if only I could conquer some form of corner jointery (dovetail, boxjoint, etc). ._

 

Try a spline miter. Use 1/8" ply for the splines. Cut the pieces a little larger than necessary. Make the angle on your saw a little more than 45 degees so the outside of the joints close up. Do small adjustment cuts if necessary. Use a canvas band clamp for assembly. Clean, attractive, easy, and plenty strong enough for an application like this. Al, I love your enthusiasm, but as an ex cabinet maker, I can't help but cringe a bit when I see ragged holes or raw screw heads in the middle of a piece of beautiful imported hardwood.


----------



## pabbi1

Quote:


  Originally Posted by *FrankCooter* /img/forum/go_quote.gif 
_Try a spline miter. Use 1/8" ply for the splines. Cut the pieces a little larger than necessary. Make the angle on your saw a little more than 45 degees so the outside of the joints close up. Do small adjustment cuts if necessary. Use a canvas band clamp for assembly. Clean, attractive, easy, and plenty strong enough for an application like this. Al, I love your enthusiasm, but as an ex cabinet maker, I can't help but cringe a bit when I see ragged holes or raw screw heads in the middle of a piece of beautiful imported hardwood._

 

Yeah, that bugs me too, but it was necessary due to the design goal... I need a removeable front plate. And agree, I need some schooling...

 I thought about doing the 45 degree and biscuit thing, but there is just magic with dovetails and box joints. And, my FIL/BIL are both cabinet makers, doing far more than cringing about my "mixed media".

 You do bring up an excellent point - this amp needs a real case design...


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Yeah, that bugs me too, but it was necessary due to the design goal... I need a removeable front plate. And agree, I need some schooling...

 I thought about doing the 45 degree and biscuit thing, but there is just magic with dovetails and box joints. And, my FIL/BIL are both cabinet makers, doing far more than cringing about my "mixed media".

 You do bring up an excellent point - this amp needs a real case design..._

 


 Drill the plugs from the front panel material just a little past each end, then use a T-Nut. The plug will match the wood about as good as it gets. Then you can screw on the faceplate from inside the amp. Brass inserts work too, but you have t o use thicker wood then. 

 The other option is to use a complementary colored wood and make it a design feature, but I like to do square plugs for that look so it doesn't look like a cheap ass dowel rod plug. Custom cut tear drop plugs look cool too. Lots of options for plugs over T-nuts. Just use sharp chisels and X-Acto blades.


----------



## M3NTAL

What kind of bias voltage are you guys using for the Stax SR-007 and Koss 950?


----------



## ericj

Quote:


  Originally Posted by *M3NTAL* /img/forum/go_quote.gif 
_What kind of bias voltage are you guys using for the Stax SR-007 and Koss 950?_

 

No SR-007 here but Stax pro bias is 580v and Koss 950 bias is 600v - this isn't that big of a difference. Just set it to 580v.


----------



## M3NTAL

Thanks Eric,

 I had thought the Koss was higher - something like 620-630v.


----------



## ericj

A few people have experimentally bumped up the bias voltage for the 950 but that's a dangerous game where you risk arcing and perforating the membrane.


----------



## manaox2

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_A few people have experimentally bumped up the bias voltage for the 950 but that's a dangerous game where you risk arcing and perforating the membrane._

 

Yeah, thought 620V is what the ESP950 was designed for. 600V seems might be a good compromise, shouldn't be too much for pro Stax like later model Lambdas. The O2 seems like it can withstand quite a bit higher bias according to reports. 40V doesn't makes as big of a danger it seems on top of 580V like it would on 240V normal bias I would think. So I honestly don't think 620V is going to arc a pro Stax, but don't hold me responsible for what happens, so thats a YMMV. Unless you have a 950, no real reason to bump it higher anyway I feel.


----------



## ericj

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Yeah, thought 620V is what the ESP950 was designed for. 600V seems might be a good compromise, shouldn't be too much for pro Stax like later model Lambdas. The O2 seems like it can withstand quite a bit higher bias according to reports, I honestly don't think 620V is going to arc a pro Stax, but don't hold me responsible for what happens, so thats a YMMV. Unless you have a 950, no real reason to bump it higher anyway._

 

The manual that came with my 950 specifies 600v. Not saying it wasn't designed with 620v as a target, but if it was, i haven't seen anything to document it.


----------



## Hottuna_

Damn it took a long while to read all of this thread.
 I am however pretty pumped to get a SS version up and running.

 Fingers are getting twitchy already.... finished my balanced B22 in December... starting to see early signs of DIY addiction....

 Anyway, I am up for PSU+SS amp boards whenever the next run occurs.
 Want to give electrostats a go.


----------



## awpagan

What is the "Stax" recommended bias voltage for the normal bias SR Lambda?
 6 Pin plug version.
 I think I remember reading somewhere 230v.

 Gilmore says 280v

 Anyone tried different bias voltages, and any thoughts?


----------



## Michgelsen

Normal bias is 230V.


----------



## ericj

Quote:


  Originally Posted by *awpagan* /img/forum/go_quote.gif 
_What is the "Stax" recommended bias voltage for the normal bias SR Lambda?
 6 Pin plug version.
 I think I remember reading somewhere 230v.

 Gilmore says 280v

 Anyone tried different bias voltages, and any thoughts?_

 

If gilmore said 280v it was a typo. normal bias are 230v.

 If your bias is too low, the sensitivity drops and it doesn't sound right. 

 If your bias is too high, there is an increase in sensitivity and an increased risk of damage to the drivers. 

 So i have to recommend staying close to the designed bias voltages.


----------



## runeight

Gents, one of the packages that went overseas has returned to me because of an addressing problem. The recipient has agreed that, since he can't readily get components, I can make these boards available to other builders.

 There is one SS and one Hybrid board set with matched jfets. Same cost as before. Only new builders and only one board set per person.

 Email me at alex@cavalliaudio.com

 The first two emails win. But I ask that you buy these with intent to build and use the amp and not to just sell it off to someone else. You may wind up owning a collector's item.


----------



## runeight

The hybrid is taken. Only the SS left.


----------



## runeight

Gone.


----------



## M3NTAL

wow! Lucky SOB's


----------



## Postal_Blue

Quote:


  Originally Posted by *M3NTAL* /img/forum/go_quote.gif 
_wow! Lucky SOB's 
	

	
	
		
		

		
		
	


	


_


----------



## pabbi1

No more impressions for 6 weeks?

 C'mon...

 New source lands tomorrow or Monday, so I'll see if this scales up past the $2k level player to something more substantial.


----------



## TimJo

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_No more impressions for 6 weeks?

 C'mon..._

 

Didn't know we had an impressions thread in the amp section. I'll certainly add some comments this weekend because I have really grown to love this amp...

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I ask that you buy these with intent to build and use the amp and not to just sell it off to someone else. You may wind up owning a collector's item. 
	

	
	
		
		

		
		
	


	


_

 

Wow, a limited edition amp driving limited edition stats... I'm feeling very lucky.


----------



## awpagan

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_If gilmore said 280v it was a typo. normal bias are 230v.

 If your bias is too low, the sensitivity drops and it doesn't sound right. 

 If your bias is too high, there is an increase in sensitivity and an increased risk of damage to the drivers. 

 So i have to recommend staying close to the designed bias voltages._

 




 From here--- HeadWize - Project: Blue Hawaii Hybrid Electrostatic Amplifier for Stax Omega II Headphones by Kevin Gilmore

 bottom of page.

 "If the bias supply is reduced to 280V, the amplifier will drive all electrostatic headphones. I tried it last night on a pair of SRX's. I never ever heard them sound so good."

 And from here--- HeadWize - Project: All-Triode Direct-Drive Amps for Electrostatic and Electret Headphones by Kevin Gilmore

 a bit more......
 bottom of page
 "Biasing the headphone diaphragms: The diaphragm bias network for the AC-coupled amp is shown in figure 5. The AC-coupled amps will work with any electrostatic headphone, if the bias voltage is correctly set. Older Stax units are low-voltage bias (~330V). Most of the newer Stax are high-bias (560V)."


 Who's going to tell him??

 Typo not only once.
 How many people fried their Phones?


----------



## runeight

If you guys will give me the recommended bias voltages for various headphones I'll make a page on the website. Then we won't need to get distracted with old information nor will any of you feel compelled to contact Gilmore regarding possibly incorrect bias voltages.


----------



## awpagan

That's a good idea Alex.

 I'd prefer to see manufacturers bias voltages.


----------



## Hottuna_

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Gone._

 

Oh man, so much for not checking up on head-fi at work... damn....

 Thats alright i guess, I am not in too huge a rush, don't have a electrostat headphone yet anyway.

 Will jump on the next board run.


----------



## Michgelsen

Common bias voltages:
 Stax Normal Bias: 230 V
 Stax Pro Bias: 580 V
 Sennheiser HE60: 540 V
 Sennheiser HE90: 500 V
 Koss ESP-950: 600 V
 HE Audio Jade: 600 V / 580 V, they even don't know themselves.


----------



## runeight

First cut at the table is done. Send more if these are needed.


----------



## luvdunhill

Guys, I'll be doing one last run of sockets. In the beginning I had a restriction of one per person, and since then I've lifted that. I just have a lot going on and need to direct my free time elsewhere. Plus, this will use up the remaining material, and after this there would be a significant reinvestment in time to do anymore. I think I will have 10 or so left. PM me and we can go from there. Looks like people are enjoying them, which is a success in my book!


----------



## pabbi1

Easily the best Stax jack ever created - gracias, Marc!

 Ok, for the more enlightened among us, there is a sleve and a Canadian quad available on eBay.


----------



## les_garten

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Guys, I'll be doing one last run of sockets. In the beginning I had a restriction of one per person, and since then I've lifted that. I just have a lot going on and need to direct my free time elsewhere. Plus, this will use up the remaining material, and after this there would be a significant reinvestment in time to do anymore. I think I will have 10 or so left. PM me and we can go from there. Looks like people are enjoying them, which is a success in my book!_

 

I got my Jack from Marc. True work or Art!


----------



## awpagan

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Guys, I'll be doing one last run of sockets. In the beginning I had a restriction of one per person, and since then I've lifted that. I just have a lot going on and need to direct my free time elsewhere. Plus, this will use up the remaining material, and after this there would be a significant reinvestment in time to do anymore. I think I will have 10 or so left. PM me and we can go from there. Looks like people are enjoying them, which is a success in my book!_

 

PM sent...


 Also Alex
 A bit of info
Stax Earspeakers Summary


----------



## Beefy

Quote:


  Originally Posted by *awpagan* /img/forum/go_quote.gif 
_Also Alex
 A bit of info
Stax Earspeakers Summary_

 

That page is a blatant copy and paste from Wikipedia. The Wikipedia entries are more up to date as well:

Stax Earspeakers - Wikipedia, the free encyclopedia
List of Stax products - Wikipedia, the free encyclopedia


----------



## Keithpgdrb

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Guys, I'll be doing one last run of sockets. In the beginning I had a restriction of one per person, and since then I've lifted that. I just have a lot going on and need to direct my free time elsewhere. Plus, this will use up the remaining material, and after this there would be a significant reinvestment in time to do anymore. I think I will have 10 or so left. PM me and we can go from there. Looks like people are enjoying them, which is a success in my book!_

 

PM sent as well


----------



## sergery

gggrEAT success!!! I have finally secured a pair of stats to call my own. I need a little time to get used to them before I start making tall claims. Right away I will say that the sound is gorgeous, although I think I need to burn in the lesser used driver a bit to catch it up. Music is creepy, impactfull, precise but still beautiful and musical. more to come.


----------



## Keithpgdrb

would anyone be interested in a thread that featured pictures of the completed exstata builds? a pic thread really. It sounds like a nice idea to me, as we could use it as samples of how people case the amp. I know I'll need that. just an idea, let me know, and maybe I'll start collecting pics from people.


----------



## Postal_Blue

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Guys, I'll be doing one last run of sockets. In the beginning I had a restriction of one per person, and since then I've lifted that. I just have a lot going on and need to direct my free time elsewhere. Plus, this will use up the remaining material, and after this there would be a significant reinvestment in time to do anymore. I think I will have 10 or so left. PM me and we can go from there. Looks like people are enjoying them, which is a success in my book!_

 

PM Sent, Thanks!


----------



## cat6man

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Guys, I'll be doing one last run of sockets. In the beginning I had a restriction of one per person, and since then I've lifted that. I just have a lot going on and need to direct my free time elsewhere. Plus, this will use up the remaining material, and after this there would be a significant reinvestment in time to do anymore. I think I will have 10 or so left. PM me and we can go from there. Looks like people are enjoying them, which is a success in my book!_

 

thanks..........also PM'd

 cheers


----------



## pabbi1

Quote:


  Originally Posted by *sergery* /img/forum/go_quote.gif 
_gggrEAT success!!! I have finally secured a pair of stats to call my own. I need a little time to get used to them before I start making tall claims. Right away I will say that the sound is gorgeous, although I think I need to burn in the lesser used driver a bit to catch it up. Music is creepy, impactfull, precise but still beautiful and musical. more to come.
	

	
	
		
		

		
			












_

 

You, sir, are truly on the path to enlightenment. Impressions will absolutely be required in the proper thread. I am just glad Runeight was able to hear on of the (early proto) eXStatA with the he60 and OII. Seemed like he liked them... 

 Oh, and maybe some mercury vapor will add the final touch of magic dust...


----------



## runeight

I did get to do this. The amp/headphone combination was better than anything I've heard so far. The designer does get a perk from time to time.


----------



## Emooze

Quote:


  Originally Posted by *Keithpgdrb* /img/forum/go_quote.gif 
_would anyone be interested in a thread that featured pictures of the completed exstata builds? a pic thread really. It sounds like a nice idea to me, as we could use it as samples of how people case the amp. I know I'll need that. just an idea, let me know, and maybe I'll start collecting pics from people._

 






 Went with the easy route and got a Nabu case. Nothing's even drilled yet. Though it's quite spacious.

 Also you have my interest in a mercury rectifier supply.


----------



## Lou Erickson

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Guys, I'll be doing one last run of sockets. In the beginning I had a restriction of one per person, and since then I've lifted that. I just have a lot going on and need to direct my free time elsewhere. Plus, this will use up the remaining material, and after this there would be a significant reinvestment in time to do anymore. I think I will have 10 or so left. PM me and we can go from there. Looks like people are enjoying them, which is a success in my book!_

 


 My sockets just arrived yesterday and they sure are lovely things. I don't think you could go wrong with these.


----------



## paxeaxe23

Hi!

 I'mhavingtrouble getting the QStax sockets here in Germany, can you send them here? I 'll obviously gulp hard and ignore how expensive the postage is. I'm lookng for a set (1 x 6pin and 1 x5 pins). 

 Hope you have some left and are happy to post to me here. I can pay paypal as soon as you let me know.

 Thanks


 Francis


  Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Guys, I'll be doing one last run of sockets. In the beginning I had a restriction of one per person, and since then I've lifted that. I just have a lot going on and need to direct my free time elsewhere. Plus, this will use up the remaining material, and after this there would be a significant reinvestment in time to do anymore. I think I will have 10 or so left. PM me and we can go from there. Looks like people are enjoying them, which is a success in my book!_


----------



## paxeaxe23

sorry Guys, that was supposed to be a PM!


----------



## Beefy

Some of you may remember that I was having a 'crackling' issue in one of the drivers of my normal bias Lambda? Well as of today, the story gets really weird......

 I bought a whole heap of parts to refurbish these phones, which I have been doing over the last couple of days. Hooked them back up to my Exstata after the recable today and they were unlistenable, with loud and intermittent buzzing and crackling. Now I've done lots of troubleshooting for this issue. Only one of the drivers is having problems. It isn't specific to one amp channel, because the problem goes with the affected driver when I switch the channel that the bad driver is hooked up to. Still there when a source isn't connected. Still there when I disconnect the power supply to luvdunhill's digital volume control. Doesn't seem to show up on my SRD7-SB, but I need to do more tests to confirm this tonight.

 But just by chance I touched one of the Q11 heatsinks, and the buzzing suddenly stopped. Removed my fingers, it started again. I could hold my fingers on there for about a minute, before it started to progressively have no effect and the buzzing started again. And yes, before anybody asks, the heatsinks are properly grounded as per the Exstata website.

 So What could possibly be going on? The amp seems to be going into some sort of oscillation, but only on the channel that this one particular driver is connected to. I wonder if whatever component is connected 'across' the stators at the cable connection is going bad? Could there be an intermittent short inside the driver? I've gone through this very logically, but it is confusing the crap out of me and I _really_ don't want to effectively throw away the $1000+++ that I have invested in these phones and amp, so any and all suggestions are welcome......


----------



## studeb

so which Q11 do you touch, bad channel, either or other channel?
 i would check your solder joints

  Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Some of you may remember that I was having a 'crackling' issue in one of the drivers of my normal bias Lambda? Well as of today, the story gets really weird......

 But just by chance I touched one of the Q11 heatsinks, and the buzzing suddenly stopped. Removed my fingers, it started again. I could hold my fingers on there for about a minute, before it started to progressively have no effect and the buzzing started again. And yes, before anybody asks, the heatsinks are properly grounded as per the Exstata website......._


----------



## Beefy

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_so which Q11 do you touch, bad channel, either or other channel?
 i would check your solder joints_

 

Touching the heatsinks of either channel was 'fixing' it temporarily. But only the channel with the 'bad' driver connected ever has audible problems.

 I'm stumped.


----------



## runeight

This is a though one. Do you have another pair of headphones? It would be helpful to know if any load causes this problem or if it is specific to the one set of headphones. Also, do you know if there is oscillation when no headphones are connected?

 Do you have a scope available? If you can get to one it would be helpful to know what the oscillation looks like.

 Try grounding the other heatsinks. Unlikely, but possible. Check the values of all components if you have the patience and do have one more look at the soldering, just in case.

 Then, finally, try just putting 100pf caps across the outputs of each channel to see if the amp oscillates. You'll need 1200V units. And, of course, a scope.


----------



## luvdunhill

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Removed my fingers, it started again. I could hold my fingers on there for about a minute, before it started to progressively have no effect and the buzzing started again._

 

that's the strangest part in my opinion...


----------



## Beefy

Thanks for the reply 
	

	
	
		
		

		
		
	


	




 Unfortunately no other headphones, and no scope. But I am in a biomedical engineering department, so hopefully somebody will have a scope I can borrow. FWIW I just tested again a few minutes ago, and my results are completely repeatable. After things warm up, crackling and buzzing commences, touching any of the four Q11/Q12 heatsinks makes it go away.

 Some random musings......

 I haven't yet tested with just the bias connected, but not the stators to the amp. Might prove whether it is just the bias, or just 'half' the amp. 

 I was wondering whether I have a grounding issue that may be contributing as well, but I think everything is pretty well covered there. The grounds/shields from my incoming balanced connection connects to the input G terminals, SG on the amp boards and G from the power supply connect to a star ground, and the star ground is connected to IEC earth (and chassis) through a ground loop breaker consisting of a 10 ohm 5W resistor in parallel with a 0.1µF capacitor. I can try disconnecting the IEC and chassis from the star ground; I can try adding the vol control supply and the incoming signal ground to the star ground (although vol control ground is directly connected to incoming signal ground anyway).

 I have some options to try with respect to the headphones...... I am told I can safely remove the components across the stators, which are apparently just protection diodes. I can also try with a lower bias, in case previous arcing has left carbon deposits on the membrane. I can remove the backing in case something is shorting inside the phones.

 The amp chassis is still open, so perhaps a lack of shielding is contributing. My panels should arrive early next week.

 ....... and that's all I've got for now


----------



## Beefy

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_that's the strangest part in my opinion..._

 

I haven't yet tried to repeat the specific effect of the touching heatsinks losing effectiveness. Perhaps it is more a case of things getting worse as the amp heats up?


----------



## runeight

If there is any way you can attach another set of headphones that will really help. We need to have some kind of control in the testing. What we don't is: is it the headphones? is it the amp? or is it the combination? If we can eliminate any one of these ...


----------



## Beefy

First things first, once the amp is fully warmed up, touching the sinks doesn't do anything. Only seems to help when the amp is cold.

 But now for the interesting part. The buzzing is definitely present when the back grille is installed, and _seems_ to stop soon after the grille is removed. I say _seems_ to, because the hockey is on the TV, and it is hard to tell for sure with the background noise...... 
	

	
	
		
		

		
			





 Perhaps there is a slight short from the bias to one of the stators when the back grille is installed? Now this is obviously a bad thing, but it doesn't seem to follow that the heatsinks could relate to this in any way.

 [EDIT] No, still some small crackling with the back grille removed, but it is an improvement. This is driving me nuts!


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_If there is any way you can attach another set of headphones that will really help. We need to have some kind of control in the testing. What we don't is: is it the headphones? is it the amp? or is it the combination? If we can eliminate any one of these ..._

 

agreed. Beefy did state: "Doesn't seem to show up on my SRD7-SB, but I need to do more tests to confirm this tonight." Perhaps he'll have a second to give this a quick whirl...


----------



## studeb

i would double check the grounding, and ground all *four* heatsinks. I soldered resistor wires to the heatsink pins, and have had trouble with those breaking, as well i had to ground all four heatsinks on each amp.

  Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I haven't yet tried to repeat the specific effect of the touching heatsinks losing effectiveness. Perhaps it is more a case of things getting worse as the amp heats up?_


----------



## Beefy

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_agreed. Beefy did state: "Doesn't seem to show up on my SRD7-SB, but I need to do more tests to confirm this tonight." Perhaps he'll have a second to give this a quick whirl..._

 

I'll hook it up now.


----------



## Beefy

Now it is not even doing it with the Exstata, let alone the SRD7. I absolutely _hate_ troubleshooting intermittent problems 
	

	
	
		
		

		
		
	


	




 Will sleep on it and do some more testing tomorrow night.......


----------



## Sathimas

Got the measured jfets back from my friend today.

 The best (and only) quad I have is:

 10,44mA
 10,16mA
 10,86mA
 9,86mA

 Would this be good enough? Or is it strictly necessary that the value does not drop under 10mA?


----------



## runeight

Probably good enough.


----------



## Beefy

Doing more testing, and the Lambdas are dead silent tonight......


----------



## Postal_Blue

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_



_

 

LOL, I a terribly sorry you are struggling with your amp, honest I am. But. holy smokes that gif got me giggling.


----------



## pabbi1

Well, I'll chime in with a different observation while we await additional data points... 

 One question folks might have about this amp is how well it scales. Admittedly I am fanboi numero zero, but through the Cambridge 840c I always had the question about how much was the player / DAC and how much was amp? And I had this nasty clip on a few Tool cuts (a daily dietary item), so I changed sources.

 Now, the Cambridge is definitely a nice player, but quite mid-fi, good above it's cost, but still limited by it's manufacturing budget. I am also an even harmonic guy, not too much interested in the 3rd order 'horrormonics'. So, I got a tube output stage source.

 The CD-1 is quite different from the Azur in a pretty dramatic, but quite good, way... psychoacou$tics aside. The main point here, for purposes of this design, is that eXStatA scales right with it. Perfectly. There is NO wonder if the amp is holding the player back, at all. 

 Off to Tool 'Aemina', then Monster Magnet, with a full compliment of Radiohead tomorrow night. So far the 'poor man's' stat amp is keeping up with the $4k source, far better than others we might mention. The adjustment once again is to listen for what is presented, not what we remember former presentations to be like, from sound staging, instrument placement, and just the overall mix.

 Oh, yes, useless without pics.

 Edit: And, yes my damn black oxide threads and bolts will be here tomorrow... oy.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Well, I'll chime in with a different observation while we await additional data points... 

 One question folks might have about this amp is how well it scales. Admittedly I am fanboi numero zero, but through the Cambridge 840c I always had the question about how much was the player / DAC and how much was amp? And I had this nasty clip on a few Tool cuts (a daily dietary item), so I changed sources.

 Now, the Cambridge is definitely a nice player, but quite mid-fi, good above it's cost, but still limited by it's manufacturing budget. I am also an even harmonic guy, not too much interested in the 3rd order 'horrormonics'. So, I got a tube output stage source.

 The CD-1 is quite different from the Azur in a pretty dramatic, but quite good, way... psychoacou$tics aside. The main point here, for purposes of this design, is that eXStatA scales right with it. Perfectly. There is NO wonder if the amp is holding the player back, at all. 

 Off to Tool 'Aemina', then Monster Magnet, with a full compliment of Radiohead tomorrow night. So far the 'poor man's' stat amp is keeping up with the $4k source, far better than others we might mention. The adjustment once again is to listen for what is presented, not what we remember former presentations to be like, from sound staging, instrument placement, and just the overall mix.

 Oh, yes, useless without pics.

 Edit: And, yes my damn black oxide threads and bolts will be here tomorrow... oy._

 

Al, I know you just got it an all, but can you please disassemble it in order to take very good pictures and full dimensions of the top disc ring and the lid? 
	

	
	
		
		

		
		
	


	




 I need that setup for my Shigaclone!


----------



## pabbi1

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Al, I know you just got it an all, but can you please disassemble it in order to take very good pictures and full dimensions of the top disc ring and the lid? 
	

	
	
		
		

		
		
	


	




 I need that setup for my Shigaclone!_

 

Manana when I have to disassemble the rack for the new parts. I'm actually still warming it up from shipment, as it is still cold to the touch.

 Oh, and here is a pic of the insides... I'll be taking an exhaustive series this weekend just to see how many ways I can violate the warranty.


----------



## macm75

Have not listened to my eXStata for a week. It's been apart waiting for a permanent box. Finally finished minutes ago (forgot to put the knob on). I tested the voltages again - look good. Now I can finally start listening.


----------



## macm75

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_CD-1_

 

Congrats! Must be a wonderful experience particularly with those HE60's.


----------



## gilency

I love the proto I bought from Alex, and when more boards are available, would love to jump in and build one myself. In the meantime, as soon as time permits, I may look for a nicer case.
 Haven't been able to buy the O2's for financial reasons (kids going through college and burning money like crazy) but I will, eventually.
 This amplifier is wonderful and makes my Sigma Pro sing.
 I just hope there is another run soon......


----------



## sergery

Very nice! That is one sexy beast, congrats Al! I thought I would post my musings over in the headphone amp area. Actually it was a somewhat organized review. 
 I suppose I could add a few more thoughts here though. In short I have been listening to this amp non-stop since I put the headphones on last friday, it is unhealthy. 
	

	
	
		
		

		
			





 My favorite parts of this setup are... EVERYTHING, heck I am greedy! The sound to me is exactly what I am looking for, not lacking in any area whatsoever. I am addicted to the echoes, the textures, the around the head sound. Anyway, it has my attention
	

	
	
		
		

		
		
	


	




 Thanks Alex!

*Edit:* Very nice casework Mac! Looking good!


----------



## HeadphoneAddict

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_Have not listened to my eXStata for a week. It's been apart waiting for a permanent box. Finally finished minutes ago (forgot to put the knob on). I tested the voltages again - look good. Now I can finally start listening._

 

That's a pretty case, but I'm curious why did you decide to put the inputs on the front?


----------



## pidesd

probably to put low level signal as far away from transfo as possible? the board signal input is also at the front. dont know though if this amp is really sensitive to external noise...


----------



## pabbi1

Yes, finding a better case for that proto won't be hard, and that ends me making points about recycling computer gear for casing. You can always get a NABU, which is a self contained potty training for DIY casing.

 Glad some folks are catching up - there are a few more usual suspects out there, along with another proto I sent to a good home... just a matter of time.

 Of course, waiting for the big guns (Nate, Marc), who have other priorities in the shorter term, but seems like we are rounding out this group pretty well.

 eXStatA for the win. Thank you, Dr. Cavalli.


----------



## n_maher

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Of course, waiting for the big guns (Nate, Marc), who have other priorities in the shorter term, but seems like we are rounding out this group pretty well._

 

I'll get there dangnabbit, getting close now, just fighting through the complexities of trying to do a world voltage capable amp which is probably going to end up not happening. 
	

	
	
		
		

		
		
	


	




 I'll be heavy into chassis fab this week and hopefully ordering panels tomorrow.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Manana when I have to disassemble the rack for the new parts. I'm actually still warming it up from shipment, as it is still cold to the touch.

 Oh, and here is a pic of the insides... I'll be taking an exhaustive series this weekend just to see how many ways I can violate the warranty. 
	

	
	
		
		

		
		
	


	


_

 

Thanks Al. Is it just a lift off top, or is it more complicated than that? Mine on the Shigaclone will have to be different since I need to use the magnetic puck that comes with the transport, but I'd like to get close to a cross between the Ayon and Mitchell Engineering's prototype CDP from years ago.


----------



## macm75

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_That's a pretty case, but I'm curious why did you decide to put the inputs on the front?_

 

It is a combination to keep the wires short and the physical location of my amp/CD on/under my nightstand/bed wrt the cable I have. Actually, and I just thought of it due to your question, best would have been right side panel.


----------



## macm75

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_eXStatA for the win. Thank you, Dr. Cavalli._

 

Hear, Hear!!


----------



## Emooze

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_eXStatA for the win. Thank you, Dr. Cavalli._

 

Same goes for me. Exceptional job!


----------



## ktm

C1/C2 450v 220uF caps are on backorder for 3 months.
 LKX2W221MESA at similar ratings a good alternate?


----------



## runeight

The two important things are the pitch and diameter.

 Diameter should be 25mm or smaller.

 The pitch can be either 10mm or 12.5mm because there are two sets of pads on the board in an attempt to accomodate this very problem.


----------



## Beefy

Quote:


  Originally Posted by *ktm* /img/forum/go_quote.gif 
_C1/C2 450v 220uF caps are on backorder for 3 months.
 LKX2W221MESA at similar ratings a good alternate?_

 

Why not try the Nichicon UVY series? Same as the VK, but rated for higher temperatures for less than a dollar more......

https://ca.mouser.com/Search/Product...47-UVY2W221MRD


----------



## ktm

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Why not try the Nichicon UVY series? Same as the VK, but rated for higher temperatures for less than a dollar more......

https://ca.mouser.com/Search/Product...47-UVY2W221MRD_

 

in stock, I think we have a winner! Thanks.


----------



## macm75

Quote:


  Originally Posted by *ktm* /img/forum/go_quote.gif 
_in stock, I think we have a winner! Thanks._

 

Hold up - way too much! Why not this ($4 - it's what I used)...
 search 647-LKX2W221MESA45


----------



## Beefy

I wasn't sure that the snap in model would fit, and I figure Alex chose the cap he did for a good reason.

 What do the data sheets say with respect to leakage, ESR and ripple rejection?


----------



## runeight

Well, I'd like to say I had a good reason, but I just prefer leaded units.

 Most of the caps at 220u/450V from reputable manuf will be ok in this position. They are not heavily stressed if the transformer secondary voltage is not too high.

 So I think that almost anything you could pick from CD, Nichicon, Xicon, United Chemicon, etc. would be suitable. And the holes should be big enough for snap-in units.


----------



## pabbi1

You _can_ also undermount... like so:







 Should have used better caps if I was going that way, but, what the heck.


----------



## macm75

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Should have used better caps if I was going that way, but, what the heck._

 

Yup, no worries. No room for 2.5"x6" asc oil cans anyway.


----------



## paxeaxe23

Well! Just been adding all my costs up and I really wish parts would have been easily available locally in Germany, but with all mouser orders and a nice case Ordered from Italy (plus most of the extra components including Tubes for the Hybrid I wan't to build once Alex makes another order for boards) will have cost me around 700 Euros! I calculate that as long as I actually do build a Hybrid as well as the Sand version, each will have cost int he region of 400 euros. I'm not unhappy about that, although myBank account will need a nice long rest. Just as well its the season of Lent!

 Anyone else want to admit how much they have paid out for their builds?


----------



## marcus1

There are some build estimates here: http://www.head-fi.org/forums/f6/exs...ml#post6179679

  Quote:


  Originally Posted by *paxeaxe23* /img/forum/go_quote.gif 
_Well! Just been adding all my costs up and I really wish parts would have been easily available locally in Germany, but with all mouser orders and a nice case Ordered from Italy (plus most of the extra components including Tubes for the Hybrid I wan't to build once Alex makes another order for boards) will have cost me around 700 Euros! I calculate that as long as I actually do build a Hybrid as well as the Sand version, each will have cost int he region of 400 euros. I'm not unhappy about that, although myBank account will need a nice long rest. Just as well its the season of Lent!

 Anyone else want to admit how much they have paid out for their builds?_


----------



## Beefy

Quote:


  Originally Posted by *paxeaxe23* /img/forum/go_quote.gif 
_Anyone else want to admit how much they have paid out for their builds?_

 

Not really..... I'm always afraid the missus will find some of my posts on this forum! 
	

	
	
		
		

		
		
	


	




 The actual electronic components didn't cost me a lot, but for the rest of the build I have nickel and dimed myself to death. Custom transformer, HV wire, jacks, casework, panels, tools...... it has all added up to well beyond my initial budget.

 Hopefully it will all be worth it in the end though


----------



## n_maher

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Not really..... I'm always afraid the missus will find some of my posts on this forum! 
	

	
	
		
		

		
		
	


	


_

 

Roger that, I'm very much a "she doesn't ask, I don't tell" type of guy.


----------



## Emooze

Hmmm electronics and boards: ~$250 shipped
 Nabu case: ~$30 shipped

 Adding in all the jacks, wire and other hardware, right around $300 USD


----------



## pabbi1

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Roger that, I'm very much a "she doesn't ask, I don't tell" type of guy. 
	

	
	
		
		

		
		
	


	


_

 

Mine asks, but nothing good can come from being completely forthcoming. So long as more (and bigger) boxes go out than come in, life is good, and, somehow, the small boxes with tubes now have a blanket exemption (just in time for the incoming 1979 & 1986 pairs of 6h30-DR).

 Never to worry, lads - HF is a naturally cultivated 'better half' repellant - strongest known to man. Mine just asks me how much life insurance I have every time a new project (or major gear acquisition) gets discussed.


----------



## les_garten

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Mine asks, but nothing good can come from being completely forthcoming._

 

A Truer statement has never been uttered!


----------



## paxeaxe23

I suppose I should count myself lucky then, my ex "she who must be obeyed" lives several thousand Miles away in Kansas so I only have to answer to my Bank balance!


----------



## studeb

i do not know if you have given up yet but, i was looking at some bent plexi and the manufacturer cut down along the bend line before bending. The cut was quite deep.

 You could try that.

  Quote:


  Originally Posted by *tomytank* /img/forum/go_quote.gif 
_More bad luck. Second perspex top has broken. I think bending it at the sides introduces too much stress, and any additional working causes it to crack.

 Or I need more experience, or more skill. (Or more Perspex! 
	

	
	
		
		

		
		
	


	




 ) 

 Maybe I should go all wood? (Wood is good. I've got lots of it, and it's easier to work with.)_


----------



## tomytank

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_i do not know if you have given up yet but, i was looking at some bent plexi and the manufacturer cut down along the bend line before bending. The cut was quite deep.

 You could try that._

 

I haven't given up, just other things getting in the way. This is useful-thanks I'll give it a try at a later date. Boilermakers comments (thank you!) about handling helped as well, but I'd already started on an alternative route before I'd read them.

 As Michgelsen said earlier, it's very à la Stax. Still need to do some tidying up. Looks good, but it doesn't have the bling factor a single bent plexi piece had, IMO. This amp puts out a fair amount of heat, especially around the valves and Q13 and Q14. For the last week I've been testing the heat dissipation. Up to now, the heat issue looks fine.


----------



## pabbi1

Very nice - question is, how is the sound?


----------



## Sathimas

The exstata is the first project where I exactly listed my costs 
	

	
	
		
		

		
		
	


	



 Never did that before.

 Tubes (2 sets!): 17€
 Tubesockets and "spacer" 17,50€
 Boards: 22€
 Transformer: ~40€
 Parts from Mouser: 137€
 More parts(wires, pot etc.): 64€

 Case: 106€
 Casework/cnc: 60€

 In Total:
 463€
 (all prices contain shipping/tax and so on)

 The case/casework became more expansive than I thought, but since the case was one of my christmas presents ... 
 I always hoped to keep that amp under 500€ which is definitely sucessful.

 The smallest STAX-amp costs about 500€ new here in Germany ...

 Btw, here's what it's gonna look like:


----------



## sergery

Off the top of my head estimate:
 Mouser: ~180
 Angela: ~80
 Boards: ~40
 Attenuator: 60
 total: ~360

 There were probably odds and ends that I used but had already.


----------



## sergery

Off the top of my head estimate:
 Mouser: ~180
 Angela: ~80
 Boards: ~40
 Attenuator: 60
 total: ~360

 There were probably odds and ends that I used but had already.


----------



## pabbi1

IIRC, and excluding initial 'trial run' expense, I think my 3 were $325 - $400 (Noble pots, and teflon sockets) - $475 (with a $125 attenuator). All had minimal chasis expense, either reclaimed SCSI case or something from on-hand wood and aluminum in my garage.


----------



## luvdunhill

Al: Any updates with the new source?!


----------



## pabbi1

Of course - last night was 'Get the KnacK" (a tribute to the departed Doug Feiger), Zappa 'Joe's Garage', and Monster Magnet... no clipping!!! Now, I am still acclimating, but this is the most analog source ever, yet with about 10% more microdetail than the Cambridge, which just mates perfectly with eXStatA. Radiohead tonight, and all Tool tomorrow night. Oh, and that other bit came in the post yesterday, so, after changing a couple of diodes, and wiring things up (yes, testiing stage by stage), there will finally be something to compare the eXStatA to.

 I did listen to 'Aemina' on Tuesday, and though WAY more involving, Tool also has this nasty habit of intentionally making congested music - I can hear it all, but not sure I like it all, as presented with the Ayon, but, it is a different distaste than presented by the Cambridge - views through opposite ends of the sphere.

 Verge Pipe 'Villains' was just complete absorption rapture, as was 'Get the Knack' - anything with guitars is golden, and I can now hear the true tone in bass (Precision vs Jazz vs Alembic vs well, everything else). There is also an extra timbre on the droms, especially the mounted toms and floor tom, with no cymbal sibilance (in fact, a brilliant shimmer in the decay).

 All to say, i think you will hate my source... well, at least through the hybrid... 

 PS: If anyone needs more 6s4a, I have a quad of Westinghouse that came along with something I was really interested in... 
	

	
	
		
		

		
			





 We REALLY need a mini-meet, but I am a little reluctant to throw this bad boy in the trunk, even for the shortest of trips.


----------



## cyanoacry

I finished casing my amp up a while ago but never got around to taking pictures:

 Went the standard Nabu case way and didn't worry about looks too much, I don't have a lot of tools here to make the cuts etc. properly. 











 Everything still sounds great with the gamma-2 as a source. I need to sit down and have a good critical listening session, then I'll post a review to the other thread. In any case, still leaps and bounds better than the SRM-252 I had.


----------



## les_garten

Quote:


  Originally Posted by *cyanoacry* /img/forum/go_quote.gif 
_I finished casing my amp up a while ago but never got around to taking pictures:

 Went the standard Nabu case way and didn't worry about looks too much, I don't have a lot of tools here to make the cuts etc. properly. 











 Everything still sounds great with the gamma-2 as a source. I need to sit down and have a good critical listening session, then I'll post a review to the other thread. In any case, still leaps and bounds better than the SRM-252 I had. 
	

	
	
		
		

		
		
	


	


_

 

Is that a TP attenuator? Hows it working with the EXStata, like it?


----------



## BoilermakerFan

I picked up a new source today too:


----------



## les_garten

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I picked up a new source today too:









_

 

It looks like it might be a touch strident and etched in it's presentation...


----------



## BoilermakerFan

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_It looks like it might be a touch strident and etched in it's presentation..._

 

What? ROK, Rega, and Thorens got nothin' on my TT man! It even has tripod feet. 



 You can't see it? 



 It's the future chassis of my Shigaclone. The DAC is going to be stuffed in the base too. It will sit on my PC credenza shelf above my monitor, right next to my HAM radio and Sylvania TV camera. USB DAC is going in the camera along with a hybrid amp TBD. It will be able to feed the eXStata in the HAM radio chassis. The ultimate stealth system. Heck, I keep my cans in the storage area of the 1954 Magnavox console. Looking for the "right" pieces of vintage Art Deco gear to repurpose for the F5 cases. 

 I just need to find vintage looking or real vintage cotton sleeving for all the cables. 

 I was probably born 70 years too late... or rather, I'm just realizing I was born in 1902 in a past life.


----------



## ktm

So how many vent holes are you Nabu case guys using to keep things cool?


----------



## BoilermakerFan

Quote:


  Originally Posted by *ktm* /img/forum/go_quote.gif 
_So how many vent holes are you Nabu case guys using to keep things cool?_

 

How I have laid out my NABUs is I stagger the vent holes on the bottom, under the boards so there isn't a straight line from the chassis hole to the PCB hole. I drill 3/16" or 1/4" holes and usually match the number of holes in the PCBs. 

 Here is an example. The chassis is actually drilled for a MHM, gainclones, and a few other things, but you can see the basic idea. I was test fitting the layout of the eXStata and a AudioSector phono stage. 










 For the top, try to have open vents above the heat sinks, but get creative. That is a huge blank canvas. 

 This is being cut out of one NABU top:






 I will add fine hex mesh under it after the top has been soda blasted, primed, and painted with the base color, then the aluminum mesh will be epoxy bonded to the top where I masked off areas to ensure a good bond. I'll pin stripe the top to highlight the Om, add my signature in the lower right via pin striping or air brush with a stencil, and then have it hit with 3 coats of clear coat. 

 If I can find a local shop that still has a louver press, the PS side will be louvered (as well as the right side to bring it back in balance). Heck, if you can find a local shop that can louver sheet metal, have the whole top done in 4 or 5 rows. Then get it powder coated.


----------



## pabbi1

I used 1/4" holes with 1" spacing just over the psu and the tubes. Might want a bottom or side hole as well, depending on your sense of asthetics, but my top plate is .20" aluminum, so it is additional heatsink itself, which NABU doesn't have.


----------



## cat6man

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_The exstata is the first project where I exactly listed my costs 
	

	
	
		
		

		
		
	


	



 Never did that before.

 Tubes (2 sets!): 17€
 Tubesockets and "spacer" 17,50€
 Boards: 22€
 Transformer: ~40€
 Parts from Mouser: 137€
 More parts(wires, pot etc.): 64€

 Case: 106€
 Casework/cnc: 60€

 In Total:
 463€
 (all prices contain shipping/tax and so on)

 The case/casework became more expansive than I thought, but since the case was one of my christmas presents ... 
 I always hoped to keep that amp under 500€ which is definitely sucessful.

 The smallest STAX-amp costs about 500€ new here in Germany ...

 Btw, here's what it's gonna look like:



_

 

very nice looking.
 can you tell us what the multiple knobs on the front are for and how you create the cool red backlighting?


----------



## WilCox

One of the sand amp slackers here looking for some help.

 Finally found some time to get the boards into a case and do the power up. Power supply came up without any problems. So did the first channel. However, I cannot adjust the balance in the second channel below about 6 volts and I am at the end of the pot rotation.

 I assume 6 volts offset may be excessive, right?

 What are the suggested remedies?

 Thanks,

 Wil


----------



## Beefy

Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_What are the suggested remedies?_

 

Start from scratch.

 But seriously, I would check that R29/30 and P1 are all the correct values, as well as R11/R12. They seem to be what 'balance' the input stage between the positive versus negative rails.


----------



## Beefy

Oh, and an update on the weird problems I have been having with my Lambda/Exstata......

 The unpleasant noises I am getting seem to be two separate phenomena. The squealing fixed by touching the heatsinks appears to have been a grounding issues that I have sorted out for the time being. The fault with the 'crackling' lies squarely with one dodgy driver.

 I've finished the re-cable with a 5-pin cable, so both the left and right driver are now connected to the same bias pin. But only the right driver crackles (and only intermittently) ruling out the socket and bias supply as the source of the problem. Interestingly, if it is crackling it suddenly gets worse immediately after being disconnected from the amp, and seems to stick around until the bias drops off. I am investigating further, but still think it might be the front dust cover coming loose.

 But in all of this testing, another oddity has popped up. When I turn on the amp, something in the power supply physically buzzes. It sounds like the noise a switching power supply makes, but lower frequency. Sometimes it lasts a fraction of a second, sometimes several seconds. I can't work out which component is making the noise, but sometimes I can clearly hear the buzzing on one rail stop before the other. The voltage seems to behave well during this buzzing and have never hiccuped in normal operation, so I'm just wondering how concerned I should be? And whether anyone else experiences the same thing?


----------



## WilCox

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Start from scratch.

 But seriously, I would check that R29/30 and P1 are all the correct values, as well as R11/R12. They seem to be what 'balance' the input stage between the positive versus negative rails._

 

Unfortunately, all parts are the correct value -- at least according to their markings. I also measured each resistor while building the boards so they were at least the correct value when I did the board build.

 Not sure I want to start over from scratch. 
	

	
	
		
		

		
			





 So close and yet so far.


----------



## Beefy

Didn't mix up P1 and P2? I _almost_ did that.


----------



## WilCox

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Didn't mix up P1 and P2? I almost did that._

 

Nah, P1 = "W503" and P2 = "W101" exactly as specified. It couldn't be that easy.


----------



## Sathimas

Quote:


  Originally Posted by *cat6man* /img/forum/go_quote.gif 
_very nice looking.
 can you tell us what the multiple knobs on the front are for and how you create the cool red backlighting?_

 

Knobs from left to right:

 - Power (turn-knob, always wanted to "turn" on power someday 
	

	
	
		
		

		
		
	


	




 )
 - Source (3 Inputs)
 - Volume
 - Switchable Loop-Out/in - I'd like to build an external croosfeed someday.

 The backlight is a rather simple thing:
 The holes for the knobs are drilled through the frontplate.
 Behind each knob there's a thick pieces of sanded plexiglass.
 Right in that piece of plexiglass I stick some LEDs.
 Since the plexiglass is sanded the light gets diffused and creates a nice backlight-effect.

 I already did that in my M³ - I'll take some pictures sunday evening.


----------



## runeight

Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_One of the sand amp slackers here looking for some help.

 Finally found some time to get the boards into a case and do the power up. Power supply came up without any problems. So did the first channel. However, I cannot adjust the balance in the second channel below about 6 volts and I am at the end of the pot rotation.

 I assume 6 volts offset may be excessive, right?

 What are the suggested remedies?

 Thanks,

 Wil_

 

If all of the components are correct values and if all the transistors are working properly then the most likely candidates are the jfets on that channel and their matching. I'm sure you matched them or maybe got a matched set with the boards, but they still might be off.


----------



## studeb

Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_One of the sand amp slackers here looking for some help.

 Finally found some time to get the boards into a case and do the power up. Power supply came up without any problems. So did the first channel. However, I cannot adjust the balance in the second channel below about 6 volts and I am at the end of the pot rotation.

 I assume 6 volts offset may be excessive, right?

 What are the suggested remedies?

 Thanks,

 Wil_

 

how long has it been idling?
 check the value of that pot, it may not be what it should be
 any bad resistors in that channel?
 any super hot heatsinks?


----------



## WilCox

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_If all of the components are correct values and if all the transistors are working properly then the most likely candidates are the jfets on that channel and their matching. I'm sure you matched them or maybe got a matched set with the boards, but they still might be off._

 

That's what I'm thinking/fearing. Matched quad that are in there are 11.2/10.8 and 11.3/10.8 so I thought I'd be fine. Of the remaining 16 JFETs, only 5 are above 10mA and all are too far off for another quad. (just checked them all again to make sure)

 I guess I'll need to order more J271s!


----------



## WilCox

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_how long has it been idling?
 check the value of that pot, it may not be what it should be
 any bad resistors in that channel?
 any super hot heatsinks?_

 

I let it idle for more than two hours. Both channels are very stable.
 Pot values are correct.
 Resistors are fine (as far as I can tell with in-circuit measurement)
 Heatsinks warm but not hot. (no difference between "good" and "bad" channels)
 I'm guessing the JFETs are the culprit but was hoping for something easier.


----------



## runeight

Perhaps there was an error in the matching? It's really hard to know now.

 It might be worth one more shot at making sure all the resistors are right, although it's pretty hard to make a mistake with this simple circuit.

 It is remotely possible that all of the tolerances on enough of the components have all lined up in just the right way to overcome even balanced jfets. This is possible in this amp because the balance/offset are set at the input stage putting nearly all of the components into the balance/offset loop. I knew this at the start which is why we've had some extensive testing periods. But yours would be the first, if this is happening, to fall out of range because of the statistics on the parts.


----------



## runeight

Oh, another question. What are the rail voltages?


----------



## BoilermakerFan

One quick question.

 With a 460VCT, would I be better off using a 282V Zener string?


----------



## luvdunhill

Did you start with P1 and P2 in the center, then do P2 next, then P1? It's possible the order here and initial conditions might help you out. Otherwise, with everything in the center, what is current through R35 and R36? Perhaps one of your FETs died? Is the 20V zener properly oriented and the proper value? Eh.. I dunno what else to check, perhaps Alex does


----------



## WilCox

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Oh, another question. What are the rail voltages?_

 

Rails are almost precisely +/-300V.


----------



## digger945

Pictures go a long way to helping troubleshoot.


----------



## WilCox

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Pictures go a long way to helping troubleshoot._

 

Not sure how useful these will be, given the camera and the Head-Fi small picture rules, but here goes:













 Board is actually much cleaner than the flash shows.


----------



## macm75

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_One quick question.

 With a 460VCT, would I be better off using a 282V Zener string?_

 

Can't tell. Only way to know is voltage on caps given the dependance on PT current capability, line voltage, and primary voltage spec'd to get the 460 rating. Posted way back, for the designed 291V string, 320-350 is desirable. I only had 307-312V on the caps and used a 275V string.


----------



## digger945

Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_That's what I'm thinking/fearing. Matched quad that are in there are 11.2/10.8 and 11.3/10.8 so I thought I'd be fine. Of the remaining 16 JFETs, only 5 are above 10mA and all are too far off for another quad. (just checked them all again to make sure)

 I guess I'll need to order more J271s! 
	

	
	
		
		

		
		
	


	


_

 

You used 11.2/10.8 for one channel and 11.3/10.8 for the other? 
 I would have paired the 11.2 with the 11.3 for one channel and the 10s together for the other.
 I can send you a couple of mine that would better match a pair of yours, but I would first want to know exactly how you did the matching. Did you use the diagram on the Cavalli website, and did you leave each device in the test jig for the same amount of time?


----------



## WilCox

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_You used 11.2/10.8 for one channel and 11.3/10.8 for the other? 
 I would have paired the 11.2 with the 11.3 for one channel and the 10s together for the other.
 I can send you a couple of mine that would better match a pair of yours, but I would first want to know exactly how you did the matching. Did you use the diagram on the Cavalli website, and did you leave each device in the test jig for the same amount of time?_

 

Yep, I paired 11.2/10.8 for one channel and 11.3/10.8 for the other. Seemed like a good idea at the time -- within the 10% tolerance and balanced from channel to channel.

 I just pulled out the two JFETs from the "bad" channel and measured them again: 11.3 and 10.8mA. I am using the Cavalli diagram. I mount the JFETs face down on double sided tape with their source and gate leads together, then allow about 15 seconds for the reading to settle. I re-measured all 16 unused JFETs and they all measure within 0.1mA of the numbers I got when I initially sorted them back in January, so I think I have validated my test jig.

 I'm thinking of putting the 11.3/10.8 pair back in, but reversing their positions 10.8/11.3. As Alex implied, maybe there is an accumulation of tolerance issue here that reversing may help alleviate.


----------



## TimJo

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_When I turn on the amp, something in the power supply physically buzzes. It sounds like the noise a switching power supply makes, but lower frequency. Sometimes it lasts a fraction of a second, sometimes several seconds. I can't work out which component is making the noise, but sometimes I can clearly hear the buzzing on one rail stop before the other. The voltage seems to behave well during this buzzing and have never hiccuped in normal operation, so I'm just wondering how concerned I should be? And whether anyone else experiences the same thing?_

 

I've noticed this as well. I wondered if it was a harmonic of the diode switching becoming audible as the capacitors are first charging. 
	

	
	
		
		

		
		
	


	




 I wouldn't worry about it.


----------



## digger945

Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_Yep, I paired 11.2/10.8 for one channel and 11.3/10.8 for the other. Seemed like a good idea at the time -- within the 10% tolerance and balanced from channel to channel.

 I just pulled out the two JFETs from the "bad" channel and measured them again: 11.3 and 10.8mA. I am using the Cavalli diagram. I mount the JFETs face down on double sided tape with their source and gate leads together, then allow about 15 seconds for the reading to settle. I re-measured all 16 unused JFETs and they all measure within 0.1mA of the numbers I got when I initially sorted them back in January, so I think I have validated my test jig.

 I'm thinking of putting the 11.3/10.8 pair back in, but reversing their positions 10.8/11.3. As Alex implied, maybe there is an accumulation of tolerance issue here that reversing may help alleviate._

 

You can try what Alex recommended and see if you can get closer to zero on the offset by chance. I still hold to the recommendation that the pairs be closely matched for each respective channel, rather than trying to compensate for unevenly matched channel pairs. If things don't work out by swapping devices then I can send you some jfets measuring 11.1/11.2/11.4 that you're more than welcome to use if you want.

  Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_I've noticed this as well. I wondered if it was a harmonic of the diode switching becoming audible as the capacitors are first charging. 
	

	
	
		
		

		
		
	


	




 I wouldn't worry about it._

 

I've had this happen several times and it was always(for me) the transformer not secured or isolated from the chassis/mounting hardware properly. 

 The caps should be fully charged the instant you hit the power switch.


----------



## TimJo

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_I've had this happen several times and it was always(for me) the transformer not secured or isolated from the chassis/mounting hardware properly. 

 The caps should be fully charged the instant you hit the power switch._

 

Well, my setup is still in the uncased mode, so its entirely possible that it could be the transformer. I'll try to pay more attention the next time I fire it up.

 Even if it is the transformer vibrating, why does it damp out almost immediately after power on? It just seemed possible that those first few cycles as power is switched on and the reservoir caps are being charged is what sets up the vibration that is heard.


----------



## Beefy

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_I've had this happen several times and it was always(for me) the transformer not secured or isolated from the chassis/mounting hardware properly. 

 The caps should be fully charged the instant you hit the power switch._

 

 Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Well, my setup is still in the uncased mode, so its entirely possible that it could be the transformer. I'll try to pay more attention the next time I fire it up._

 

No, it is definitely not the transformer, which is a fully encapsulated unit from SumR that is very securely mounted. The noise definitely comes from the PSU board itself...... but the PSU seems to work perfectly otherwise.

 I realised the other day that the engineering blokes in my lab have a Fluke Industrial Scopemeter, 25mHz sampling. I will try and bring that home next weekend to see what the voltages do while it is buzzing.

 *

 Something interesting I did this morning...... I received a whole heap of fasteners the other day, and on a whim replaced my el cheapo zinc plated heatsink screws with some much nicer stainless steel jobbies. It reduced the resistance of the heatsinks to ground from up to 1.5ohms down to essentially zero. So don't cheap out on your heatsink mounting and grounding!


----------



## digger945

The truth is, I dunno
	

	
	
		
		

		
		
	


	



 I have zero experience with HV shunt regulators or power supplies. Only pass through stuff on the HV side and little more on the LV side.

 You're right that there will be a high initial current inrush to the PS caps when you first turn on the amp to empty caps, so maybe that's the situation here. I guess if it doesn't last for more than a second or two then, like you said, no worries.

 If I ever, ever get around to actually building mine then I will do some measuring and stuff to maybe see what's going on.

  Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_No, it is definitely not the transformer, which is a fully encapsulated unit from SumR that is very securely mounted. The noise definitely comes from the PSU board itself...... but the PSU seems to work perfectly otherwise.

 I realised the other day that the engineering blokes in my lab have a Fluke Industrial Scopemeter, 25mHz sampling. I will try and bring that home next weekend to see what the voltages do while it is buzzing.

 *

 Something interesting I did this morning...... I received a whole heap of fasteners the other day, and on a whim replaced my el cheapo zinc plated heatsink screws with some much nicer stainless steel jobbies. It reduced the resistance of the heatsinks to ground from up to 1.5ohms down to essentially zero. So don't cheap out on your heatsink mounting and grounding!_

 

Maybe the Fluke has datalogging and you can hook it up and record the event.


----------



## Beefy

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Maybe the Fluke has datalogging and you can hook it up and record the event._

 

That's the plan 
	

	
	
		
		

		
		
	


	




 [EDIT] I wonder if there is anything in the amp that could cause the test points to vibrate? I was just disconnecting my PSU to replace the heatsink screws, and the plastic part of the testpoints can definitely make noise......


----------



## Beefy

Interesting point on the buzzing. I can make the PSU buzz for a fraction of a second by making 'rough' intermittent contact at the DC output with my multimeter probes. Maybe it only buzzes during sudden/large changes in regulation, as would be expected during amp power up and suddenly adding the load of a multimeter?


----------



## studeb

i cased up my amp this week, and i now can hear this noise.
 i did not notice it uncased, if i have a chance i will try to track it down this weekend.
 Like yours sometimes a sec sometimes a few seconds.
 Does not come through the headphones.

  Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_But in all of this testing, another oddity has popped up. When I turn on the amp, something in the power supply physically buzzes. It sounds like the noise a switching power supply makes, but lower frequency. Sometimes it lasts a fraction of a second, sometimes several seconds. I'm just wondering how concerned I should be? And whether anyone else experiences the same thing?_


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Something interesting I did this morning...... I received a whole heap of fasteners the other day, and on a whim replaced my el cheapo zinc plated heatsink screws with some much nicer stainless steel jobbies. It reduced the resistance of the heatsinks to ground from up to 1.5ohms down to essentially zero. So don't cheap out on your heatsink mounting and grounding!_

 

Zinc plated fasteners there are definitely bad. But you need to watch the SS too. SS thermal heat transfer properties are about 1/200th of aluminum, so there is a slight chance the heat sinks could crack over time because the aluminum will expand quicker, but it also cools quicker, so if you have the screws really tight and the amp on long enough to fully saturate the SS screws so they're both at the same temperature, the heat sink will cool much faster than the screw even with it tightly connect to draw out the heat from the screw. Not a guarantee that it will happen, but just watch them and check that first if you start getting oscillations that would mimic ungrounded heat sinks. 

 I had that same scenario occur on a zinc galvanized 1/2" oil drain pipe that was used to replace a plug on the lower crankcase of my cheap "7HP" cast aluminum air compressor. I had added the pipe and ball valve to make oil changes in it easy during break-in and regular maintenance. One weekend it was pretty cold and I had run the compressor like crazy with the die grinder on a few lawn mower blades, ax, etc. Next day I had oil all over the tank and floor of the garage. The crankcase split right at the union of the pipe and the crankcase port. Had to clean it all up, clean the crankcase and JB Weld / Magnum Steel epoxy the whole area to reinforce it. Secretly hoped it would crap out again so I could upgrade to a massive true 10HP Ingersoll-Rand Fully Packaged Unit, but the darn thing has been running solid for 7 years now.


----------



## Beefy

I feel like I'm clogging up the thread with my ramblings......

 ...... but I can confirm that the Exstata PSU can handle partial short circuits. I just copped 340V through my hand by brushing against the top of C2. Still tingles. I've accidentally touched the tops of electrolytics before, but never on a negative rail. I thought the cap was faulty, but the caps on the negative rail on my volume control supply is exactly the same. Makes sense when you think about it!


----------



## WilCox

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_You can try what Alex recommended and see if you can get closer to zero on the offset by chance. I still hold to the recommendation that the pairs be closely matched for each respective channel, rather than trying to compensate for unevenly matched channel pairs. If things don't work out by swapping devices then I can send you some jfets measuring 11.1/11.2/11.4 that you're more than welcome to use if you want._

 

Well, I swapped the positions of Q1R and Q2R (now 10.8mA/11.3mA) and the problem is still there but reversed, confirming that matching is the problem. Previously, I couldn't get below about 6V for balance adjustment with P2R fully clockwise. After swapping, I can't get below 2V with P2R fully counter-clockwise. I let the amp cook for several hours and the balance is drifting between 0.9 and 1.6V so I may go forward later to connect the inputs and outputs and give it a listen.

 I've just ordered 40 more JFETs from Mouser so I can get a closer match and not have the pot maxed.

 Thanks to all for your help and suggestions. The Head-Fi community is fantastic.


----------



## runeight

I hate to say this so late, but those jfets are close enough to not be causing the problem assuming that you are measuring them correctly. It must be something else.


----------



## macm75

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I just copped 340V through my hand by brushing against the top of C2. Still tingles._

 

Yikes. Glad you are OK.


----------



## runeight

Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_Yep, I paired 11.2/10.8 for one channel and 11.3/10.8 for the other. Seemed like a good idea at the time -- within the 10% tolerance and balanced from channel to channel.

 I just pulled out the two JFETs from the "bad" channel and measured them again: 11.3 and 10.8mA. I am using the Cavalli diagram. I mount the JFETs face down on double sided tape with their source and gate leads together, then allow about 15 seconds for the reading to settle. I re-measured all 16 unused JFETs and they all measure within 0.1mA of the numbers I got when I initially sorted them back in January, so I think I have validated my test jig.

 I'm thinking of putting the 11.3/10.8 pair back in, but reversing their positions 10.8/11.3. As Alex implied, maybe there is an accumulation of tolerance issue here that reversing may help alleviate._

 

Wilcox, if you'd like to do a bit of troubleshooting, please measure the voltages across R7, R8, R9 and R10.


----------



## ktm

Ok, I'm using the old red hybrid amp boards. 
 My version of the amp BOM doesn't show R37 and R38. 
 100 ohm 1% 1/8 watt???????


----------



## WilCox

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Wilcox, if you'd like to do a bit of troubleshooting, please measure the voltages across R7, R8, R9 and R10._

 

R7 = 0.67V
 R8 = 0.69V
 R9 = 0.70V
 R10 = 0.68V


----------



## pabbi1

Quote:


  Originally Posted by *ktm* /img/forum/go_quote.gif 
_Ok, I'm using the old red hybrid amp boards. 
 My version of the amp BOM doesn't show R37 and R38. 
 100 ohm 1% 1/8 watt???????_

 

Wow, what kind of jerk would sell you a board with an incomplete BOM? 
	

	
	
		
		

		
			





 Yes, you are correct - 100ohm, 1/8w, 7mm - 71-RN55D-F-100

 Also, be sure to use one 68k 3w across r13-r15 and r16-18, as opposed to the 27k for r13, 14, 15, 16, 17, & 18. That is the 'follower mod', which will all but make yours identical to the black boards.

 Of course, AC should verify...


----------



## ktm

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Wow, what kind of jerk would sell you a board with an incomplete BOM? 
	

	
	
		
		

		
		
	


	




 Yes, you are correct - 100ohm, 1/8w, 7mm - 71-RN55D-F-100

 Also, be sure to use one 68k 3w across r13-r15 and r16-18, as opposed to the 27k for r13, 14, 15, 16, 17, & 18. That is the 'follower mod', which will all but make yours identical to the black boards.

 Of course, AC should verify..._

 

I've already got the 68kohms in there. The 100 ohm resistors were almost a given, but asking is free! 
 I did not to order q5-q8. I had them on my sheet as having them already, but now I can't locate them. 
 My luck I'll buy them and find the others the next day. I'm going to verify matching values on my 
 2sj74 quad from AMB and add them today. I also hope to get the PS up and adjusted today. 
 I checked wall voltage, 123.7vac. Looks Like I'll be using the 125v tap of the 269jx


----------



## TimJo

Quote:


  Originally Posted by *ktm* /img/forum/go_quote.gif 
_I did not to order q5-q8. I had them on my sheet as having them already, but now I can't locate them. 
 My luck I'll buy them and find the others the next day._

 

I have a bunch of these. I'd be happy to send you some if you want. Send me a PM and I'll drop them in the mail tomorrow morning...


----------



## runeight

Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_R7 = 0.67V
 R8 = 0.69V
 R9 = 0.70V
 R10 = 0.68V_

 

I assume this is with your balance all to one side? Even so these values are very well matched. So now how about R23-R28?? What are the values there? And the voltage drops across them?


----------



## WilCox

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I assume this is with your balance all to one side? Even so these values are very well matched. So now how about R23-R28?? What are the values there? And the voltage drops across them?_

 

Thanks for your patience, Alex. Yep, balance all the way counter-clockwise. R23-R28 are 33Kohm 1 Watt Vishay purchased from Mouser as per Excel BOM. Here's the voltage drop after warm-up:

 R23 = 100.4V
 R24 = 100.4V
 R25 = 100.3V
 R26 = 100.5V
 R27 = 100.5V
 R28 = 100.5V

 I'm guessing I have one bad JFET that doesn't show problems while in the test jig but for some reason is not behaving correctly in this circuit.


----------



## runeight

Well, Idss matching is not the same as Vgs matching so you might have good Idss matches but bad Vgs matches requiring the kind of imbalance at the sources that you seeing. Perhaps another set will do the trick.

 However, if the rail is 300V then given the voltages across R23-R28 you should be getting less than 1V balance adjustment. So I am a bit puzzled although it could just be the meter and its resolution.


----------



## WilCox

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_However, if the rail is 300V then given the voltages across R23-R28 you should be getting less than 1V balance adjustment. So I am a bit puzzled although it could just be the meter and its resolution._

 

I should clarify that when I put the top on the case and allow it to warm up for an hour or more, the balance can drift down further and wander between 500mV and 1.5V. I believe I took the readings above after a full warm up, so I was probably on the inside edge of the <1V spec. 

 Problem is it takes up to 1/2 hour for the "bad" channel to get down to <2V balance. The "good" channel gets to <1V very quickly and stays there.

 I'm hoping a new matched pair of JFETs will set things straight. 
	

	
	
		
		

		
		
	


	




 Thanks again for your help.


----------



## ktm

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_I have a bunch of these. I'd be happy to send you some if you want. Send me a PM and I'll drop them in the mail tomorrow morning..._

 

Thanks for the offer, but I just added it to a few last items waiting to ship at Mouser. It will be finished up next weekend one way or another.


----------



## Beefy

Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_I'm hoping a new matched pair of JFETs will set things straight. 
	

	
	
		
		

		
		
	


	


_

 

This is something I discussed with Alex earlier in the thread, but I'll ask it again here.

 Assuming the JFETs aren't that far off matched, could other transistors in the amp cause this problem? In particular, I discarded a KSA1156 because its HFE was way off compared to the others I bought. Obviously a multimeter HFE reading has little relation to the HV operating point in the amp, but still......


----------



## luvdunhill

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Obviously a multimeter HFE reading has little relation to the HV operating point in the amp, but still......_

 

actually, it's not the voltage operating point that matters (as much), but the current. (am I being obnoxiously pedant?) One way to get an idea how valid the hfe measurement that your meter does is to look at the hfe versus collector current graph on the datasheet. The Fairchild datasheet has the Ic scale in A, which might very well be a typo. The NEC datasheet has the scale in mA, which makes a bit more sense 
	

	
	
		
		

		
			





 Point being, your meter uses a Ic in the uA. This shows you how well that translates to values in the mA range, for example.

 It's fun to compare the "old" and "new" devices. Perhaps the process wasn't sourced from NEC and Fairchild developed their own process?


----------



## digger945

Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_ I am using the Cavalli diagram. I mount the JFETs face down on double sided tape with their source and gate leads together, then allow about 15 seconds for the reading to settle. I re-measured all 16 unused JFETs and they all measure within 0.1mA of the numbers I got when I initially sorted them back in January, so I think I have validated my test jig._

 

 While testing a few of these devices I have noticed that some of them drop a little and stop about 15 to 30 seconds later, and some of them keep dropping for about 2 minutes. I would recommend that anyone testing these allow at least 3 minutes in the test jig to make absolutely sure you have a stable and accurate reading.
 The ones that I have matched for builders here are done this way, and the same amount of time is allotted to Vgs matching also.

  Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_I'm guessing I have one bad JFET that doesn't show problems while in the test jig but for some reason is not behaving correctly in this circuit._

 

Could be, although they won't see much difference in the amp than in the test jig.

 I don't suppose you could take a measurement of the AC at the output of the amp to see if there is anything going on there.


----------



## runeight

The other transistors should not have any control over the currents except the mirror devices themselves. The KSAs are in series with the jfets and must pass the jfet currents exactly except for the uA of base current. The KSCs in the Wilson must pass what their control devices pass.

 However, if the mirror transistors (BC550 or 2N5550) are way mismatched this will affect the accuracy of the mirrors. However, looking at the measurements the mirror currents seem almost perfectly ... mirrored.


----------



## pabbi1

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_(am I being obnoxiously pedant?)_

 

Only wrt how long it's taking you to build...


----------



## WilCox

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_I don't suppose you could take a measurement of the AC at the output of the amp to see if there is anything going on there._

 

I forgot to mention that earlier! The "bad" channel has about 56mV RMS of AC noise at the output while the "good" channel has about 16mV RMS at the output.


----------



## BoilermakerFan

*luvdunhill*

 Did you get my PMs wrt the jacks?


----------



## digger945

Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_I forgot to mention that earlier! The "bad" channel has about 56mV RMS of AC noise at the output while the "good" channel has about 16mV RMS at the output._

 

I'll assume you have the inputs grounded before you power up and test.


----------



## paxeaxe23

I'm coming to the end of my build and am left with a couple of questions before I can continue.

 1. I don't have enough installation kits for the heatsinks, and therefore am short 4 insulator pads on the Power supply. I have mounted Q3 which is the only one with an obvious metal casing with the last pads but wonder if its OK to mount Q5,6,7 and 8 without the insulator as the casings seems to be made of plastic.

 2. I am getting a bit confused by an earlier discussion on matching the jfets q1,2 on the Amp board. I assume things are still likely to be OK if I just measure the Idss using my multimeter? this is what I did: I soldered an IC socket onto a piece of proto board and "jumped" gain and source. I connected +12V to the jumper and -12V to "-"DMM and connected the drain pin to a wire (soldered a wire to the relevant pin of the IC socket). I placed the jfets in the relevant IC socket pins then connected the wire from the drain to "+"DMM and took readings at the moment I the circuit was complete.

 I had aroud 80 jfets to choose from and got almost 75% well under the 10mA, as well as few almost 20mA. I have 3 sets 

 10.1, 10.1, 10.4, 10.7

 11.1, 11.3, 11.7, 11.8

 14.1, 14.4, 14,7, 14.9

 Assuming I have done this correctly, which set would is most likely to be the best one?

 Thanks for you help


----------



## Beefy

Quote:


  Originally Posted by *paxeaxe23* /img/forum/go_quote.gif 
_1. I don't have enough installation kits for the heatsinks, and therefore am short 4 insulator pads on the Power supply. I have mounted Q3 which is the only one with an obvious metal casing with the last pads but wonder if its OK to mount Q5,6,7 and 8 without the insulator as the casings seems to be made of plastic._

 

Should be OK, though I will defer to others for a definitive answer. Though I will say that the BOM suggested thermasil pads also function as a facilitator for heat transfer. So if you don't use these pads, then you should at the very least use a tiny dab of silicone heat transfer compound.


----------



## runeight

Quote:


  Originally Posted by *paxeaxe23* /img/forum/go_quote.gif 
_I'm coming to the end of my build and am left with a couple of questions before I can continue.

 1. I don't have enough installation kits for the heatsinks, and therefore am short 4 insulator pads on the Power supply. I have mounted Q3 which is the only one with an obvious metal casing with the last pads but wonder if its OK to mount Q5,6,7 and 8 without the insulator as the casings seems to be made of plastic.

 2. I am getting a bit confused by an earlier discussion on matching the jfets q1,2 on the Amp board. I assume things are still likely to be OK if I just measure the Idss using my multimeter? this is what I did: I soldered an IC socket onto a piece of proto board and "jumped" gain and source. I connected +12V to the jumper and -12V to "-"DMM and connected the drain pin to a wire (soldered a wire to the relevant pin of the IC socket). I placed the jfets in the relevant IC socket pins then connected the wire from the drain to "+"DMM and took readings at the moment I the circuit was complete.

 I had aroud 80 jfets to choose from and got almost 75% well under the 10mA, as well as few almost 20mA. I have 3 sets 

 10.1, 10.1, 10.4, 10.7

 11.1, 11.3, 11.7, 11.8

 14.1, 14.4, 14,7, 14.9

 Assuming I have done this correctly, which set would is most likely to be the best one?

 Thanks for you help_

 

Use the 14s. 14.1/14.4 and 14.7/14.9 as pairs.

 paxeaxe23, as beefy says, you can put use all plastic packages without the pad as long as you use some thermal grease. I do this quite a lot on plastic devices. It saves the cost of the heatsink kits and IMHO makes better heat transfer if the grease is applied correctly.


----------



## pabbi1

Sleves of (5) 6s4a - $3.39 per, shipped.

Vacuum Tubes - 6S4 A RCA (5) NOS/NIB - eBay (item 330408961202 end time Mar-03-10 13:33:19 PST)


----------



## paxeaxe23

OK, getting nearer now, but yet another dumb question. I now want to mount Q3 and Q4 on the amp board. does the circle opposite the thicker white line on the silkscreen denote where pin 1 or pin 3?


----------



## Beefy

To anyone following my story, I think I managed to find out what the 'crackling' issue was with my Lambda normal bias......

 The crackling noise doesn't happen on my SRD7-SB. But I'm quite sure it isn't the amplifier, because the crackling only ever happens when the bias is up and the rear stator of the bad driver is connected to the amp. I have recabled, removed the protection diodes, get no apparent continuity between this stator and the bias wire, but still it crackles away when connected.

 My idea was that perhaps the bias on the SRD7-SB is much lower than the Exstata. At the higher bias, perhaps something is shorting or arcing? So I progressively dropped the bias on the Exstata from 230 to 140V while listening carefully. The lower the bias, the more intermittent and quieter the crackling, until it seems to disappear somewhere between 150-170V. It comes back as the bias hits 180-190V.

 I am 100% sure that I am measuring correctly at the test point rather than the screw terminal, and 99% sure that my meter isn't bogging down the voltage in the first fraction of a second - I have used two separate meters, both with 10Mohm input impedance and set at the appropriate range. I also figure if was just a case of the bias actually being much higher than I am measuring, the crackling noise would be in both drivers - or at the very least, in both stators on the same driver.

 So while I am not going to call it just yet considering the intermittent nature of the problem, I am going to assume that my phones are just a bit dodgy at the 'proper' 230V bias, and running at a lower bias will have to do.

 But the 1% possibility remains...... perhaps the bias on the Exstata is actually much higher than I am able to measure?


----------



## tomytank

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Very nice - question is, how is the sound? _

 

It's excellent!

 So far, I haven't said anything about the sound of this amp 
	

	
	
		
		

		
		
	


	




, but I like this amp a lot.

 I know I'm a newbie at Head-fi, but I'll say what I can: It's a very musical amp. Very engaging. Listening to only 'one' track is an exercise in self-discipline-the sound is mesmerizing IMO.

 The stax sound is there, and it's detailed (lots of clarity on backgrounds/noises and definition on instruments) and balanced (nothing sounds overemphasized, the sound 'appears to be' just what the amp has been given) with all tracks and music styles I've listened to so far. 

 I can only compare it with what I've heard, and I prefer it over the 006t (Kimik), SRM-Xh and SRD-X. It sounds better than all of these-IMO.

 Tested with two setups: 
 Marantz CD65DXII - SE GAC-1 cables - eXStata - L Pro Classic/L 404 Sig
 SBR - Dacmagic - XLR Chord Chameleon S+ - eXStata - L Pro Classic/L 404 Sig

 I prefer the LPro Classics to the sigs and the eXStata sounds brilliant on both setups.

 For the price in parts, time to build, and excellent sound quality, this amp is a no-brainer-thanks to everyone involved. And to Runeight for designing it. We need more boards! I'd like to replace the SRM-Xh with an SS eXStata version.


----------



## spritzer

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_But the 1% possibility remains...... perhaps the bias on the Exstata is actually much higher than I am able to measure?_

 

Might as well reply to this here, this would be my guess. Take a picture of the SB circuit board (and try to read the value of the transient suppressor) and I can tell you what is going on.


----------



## runeight

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_But the 1% possibility remains...... perhaps the bias on the Exstata is actually much higher than I am able to measure?_

 

For the LV bias supply and with 10M DMM at the test point the steady state voltage should be in the neighborhood of 15-20V higher than the measurement. Steady state meaning that you leave the probe on the TP for a second or two to let it pull down the bias supply.

 Also, if there is an consequential current draw at the headphones the 4M7 resistor will pull the actual bias significantly lower than the TP along with pulling TP itself down. You won't be able to measure the effect on the real bias voltage without a completely different test rig.


----------



## paxeaxe23

Quote:


  Originally Posted by *paxeaxe23* /img/forum/go_quote.gif 
_OK, getting nearer now, but yet another dumb question. I now want to mount Q3 and Q4 on the amp board. does the circle opposite the thicker white line on the silkscreen denote where pin 1 or pin 3?_

 

i see there are a few more folks online now, so in case this one got lost i quote my question.
 I would appreciate some advise! Sorry to bother folks with newbie questions, but its better to ask than to guess!


----------



## Beefy

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_Might as well reply to this here, this would be my guess. Take a picture of the SB circuit board (and try to read the value of the transient suppressor) and I can tell you what is going on._

 

 Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_For the LV bias supply and with 10M DMM at the test point the steady state voltage should be in the neighborhood of 15-20V higher than the measurement. Steady state meaning that you leave the probe on the TP for a second or two to let it pull down the bias supply._

 

Well the way I look at it, even if the Exstata is measuring a generous 30V high, my multimeter target should be 200V. I'm getting best 'crackling' results at 150V. So any way we try and slice it, something is wrong with the phones.

 So for now, I'll leave it as is, and I just have to hope that long-term I can find a new driver somewhere to get the most out of my current setup.

 *

 My FPE panels arrived today. Dead sexy, if I may say so myself


----------



## Emooze

Got my SS all boxed up on Friday. Planning on getting some nicer mesh for the top, painting the case and getting a front panel but this will do for now.


















 I have to readjust the bias before I form any solid conclusions but it's still an amazing sound. I'll have some comparisons to other amps, both from myself and others, hopefully this weekend at the Boston area meet.


----------



## runeight

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Well the way I look at it, even if the Exstata is measuring a generous 30V high, my multimeter target should be 200V. I'm getting best 'crackling' results at 150V. So any way we try and slice it, something is wrong with the phones.

 So for now, I'll leave it as is, and I just have to hope that long-term I can find a new driver somewhere to get the most out of my current setup.

 *

 My FPE panels arrived today. Dead sexy, if I may say so myself 
	

	
	
		
		

		
		
	


	


_

 

I should have added one more important assumption that I made, namely, that the bias leakage currents in the bias lines and headphones amount to the eqiuvalent of 100G to ground. Others may know a more accurate number for this equivalent resistance. If the resistance is smaller than this then the voltage difference will be higher. If the resitance is higher then the voltage difference will be lower. If the resistance is perfectly infinite then the voltages will, obviously, be the same. But the difference between say 100G and 1G should only amount to a few volts difference in the difference.


----------



## runeight

Quote:


  Originally Posted by *paxeaxe23* /img/forum/go_quote.gif 
_i see there are a few more folks online now, so in case this one got lost i quote my question.
 I would appreciate some advise! Sorry to bother folks with newbie questions, but its better to ask than to guess!_

 

If you look at the devices from the top you will see that along the long axis one face (the front) is shorter than the other face (the back). The silkscreen outline also has a shape like this. Just orient the shorter face to the shorter silkscreen face and you'll have it. When you get it right the transistors will be facing in opposite directions. Q3's front face will be towards the input jacks and Q4's front face will be towards the back of the board


----------



## digger945

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_ So any way we try and slice it, something is wrong with the phones._

 

I wonder if you could try to recreate the problem and then have a look at the phones up close in a completely dark room and see if you can see anything arcing. I do that with cars sometimes when troubleshooting ignition problems.
  Quote:


 ... Dead sexy... 
 

Do you say that like Austin Powers
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_For the LV bias supply and with 10M DMM at the test point the steady state voltage should be in the neighborhood of 15-20V higher than the measurement. Steady state meaning that you leave the probe on the TP for a second or two to let it pull down the bias supply.

 Also, if there is an consequential current draw at the headphones the 4M7 resistor will pull the actual bias significantly lower than the TP along with pulling TP itself down. *You won't be able to measure the effect on the real bias voltage without a completely different test rig*._

 

VTVM?


----------



## paxeaxe23

Alex!

 Its quite hard to see the difference in length, but on what I think is the BACK (long side) there is a small 3 printed top left, which would make sense. since looking at it with the front (shorter) side the legs would read 1,2,3 left to right.

 i'll wait till the morning to mount them (its already too late to start that anyway) and check here just in case!

 Talking of case, My case just arrived. I ordered a "Galaxy Maggiorato" a Hi-fi 2000 case from Italy, it got here in 2 days! and my Stax sockets arrived today as well. My friend Horst is coming over Wed. to supervise setting up and testing the Power supply and will hopefully fix any glaring solder mistakes I may have made. All being well, I'll post pictures and impressions by the week-end as long as the one condenser I am missing arrives tomorrow!

 Thanks for all your help. 

 I went out and bought a nice Weller solder station today as well! 

 I think I'm hooked 

 Good night


----------



## WilCox

Wired up the inputs and outputs this afternoon and connected my 404LE. Wow! This amp can run with the big dogs. A bit of Pink Floyd, Sibelius, Tchaikovsky, Porcupine Tree, Diana Krall and the Radiators to get a sense of what this amp could do and I was most impressed. Connected the O2 MKII and found that this amp has balls!

 Great first impression! The balance problem doesn't seem to hold it back, as far as I can tell, but looking forward to a new batch of JFETs later this week to get the right channel within specs.

 Great job Alex and team!


----------



## les_garten

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_

 VTVM?_

 

Vacuum Tube Volt Meter

 From the good old days...


----------



## sergery

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_Got my SS all boxed up on Friday. Planning on getting some nicer mesh for the top, painting the case and getting a front panel but this will do for now.

 I have to readjust the bias before I form any solid conclusions but it's still an amazing sound. I'll have some comparisons to other amps, both from myself and others, hopefully this weekend at the Boston area meet._

 

Very nice Emooze! Maybe some hexmesh might really round it out. Looking forward to hearing what some outsiders have to say about the amp, although I think we can guess it won't be too negative.
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_Wired up the inputs and outputs this afternoon and connected my 404LE. Wow! This amp can run with the big dogs. A bit of Pink Floyd, Sibelius, Tchaikovsky, Porcupine Tree, Diana Krall and the Radiators to get a sense of what this amp could do and I was most impressed. Connected the O2 MKII and found that this amp has balls!

 Great first impression! The balance problem doesn't seem to hold it back, as far as I can tell, but looking forward to a new batch of JFETs later this week to get the right channel within specs.

 Great job Alex and team!_

 

It does have some balls doesn't it? I have been listening with my volume set to about 1/3 on the slider in foobar. That it wails with O2's is a further testament. 
	

	
	
		
		

		
		
	


	




 Keep us updated as you all get a better feel for the system!

 -Serge


----------



## pabbi1

One negative folks often talk about is that stats seem anemic on rock... well, I whipped out 'Highway to Hell', specifically 'Touch Too Much' and 'Night Prowler'. This is simply as good as I ever heard them, and at about 1 o'clock - the '61 Les Paul (or '63 SG Standard) has overtones to kill for, and Bonn Scott's wailing is simply unparalleled.

 In human terms, I think Bon Scott describes eXStatA best - "She has a face of an angel, smile just like sin, the body of Venus _with arms_." 

 Yes, I am curious what the wider, non-invested audience thinks.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Yes, I am curious what the wider, non-invested audience thinks._

 

On the flip side, does it really matter? We have our boards, our builds, or our amps depending on our progress. We can just enjoy them. I have my boards here on my desk and I just look at them daily as the parts are coming in. I have also invested in amps and cans that were supposed to be great and was completely let down by them. So far, not one person has been disappointed that I recall. A few may not have loved the the O2s on it only because the lower 'stats sounded so good in a side-by-side comparison, but to me that is just awesome. I also remember a certain TOOL fan was having some clipping issues off his old source, but he went "digital vinyl" and seems to be happy now too. 
	

	
	
		
		

		
		
	


	




 I love the idea of mercury vapor in the PS, but if it jeopardizes the sound, it would be yanked out. I really just want the vapor tube so I can put it front and center in the little round window of my Halllicrafter S-95 chassis with some custom surrounding sheet metal. 

 Only thing I'm waiting for is for somebody to drop in the thread that didn't get PCBs, but builds an eXStata P-2-P! Surely somebody has thought about it already, right?


----------



## pabbi1

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_On the flip side, does it really matter? We have our boards, our builds, or our amps depending on our progress. We can just enjoy them. I have my boards here on my desk and I just look at them daily as the parts are coming in. I have also invested in amps and cans that were supposed to be great and was completely let down by them. So far, not one person has been disappointed that I recall. A few may not have loved the the O2s on it only because the lower 'stats sounded so good in a side-by-side comparison, but to me that is just awesome. I also remember a certain TOOL fan was having some clipping issues off his old source, but he went "digital vinyl" and seems to be happy now too. 
	

	
	
		
		

		
		
	


	


_

 

I just want the community to be aware of what is available, and how many missed the boat, at least for now.

  Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I love the idea of mercury vapor in the PS, but if it jeopardizes the sound, it would be yanked out. I really just want the vapor tube so I can put it front and center in the little round window of my Halllicrafter S-95 chassis with some custom surrounding sheet metal._

 

Nick has a box of tubes AND another box of caps - maybe we'll have some reports coming shortly, but I don't see how it could have a negative impact. After all, the amp designed for intermediate builders might well benefit from a psu made by, and for, the illuminati. He also has Lord Mercury Vapor (Frank) close, so, I'm thinking there is only upside - and, why I 'invested' in the research... 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Only thing I'm waiting for is for somebody to drop in the thread that didn't get PCBs, but builds an eXStata P-2-P! Surely somebody has thought about it already, right?_

 

There are a couple of candidates I can think of, along with some changes in design, which I think is inevitable (certainly someone will prefer el34/6ca7, or different resistor / zener values), just to, perhaps, voice for a particular phone. No me, cause I'm done, well, pending MV research.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_I just want the community to be aware of what is available, and how many missed the boat, at least for now.



 Nick has a box of tubes AND another box of caps - maybe we'll have some reports coming shortly, but I don't see how it could have a negative impact. After all, the amp designed for intermediate builders might well benefit from a psu made by, and for, the illuminati. He also has Lord Mercury Vapor (Frank) close, so, I'm thinking there is only upside - and, why I 'invested' in the research... 
	

	
	
		
		

		
		
	


	






 There are a couple of candidates I can think of, along with some changes in design, which I think is inevitable (certainly someone will prefer el34/6ca7, or different resistor / zener values), just to, perhaps, voice for a particular phone. No me, cause I'm done, well, pending MV research._

 

Muhahahahahahahahaaaa....

 Alrighty then, I'm in for MV glow too, might as well tack it on to the tail end of the HE60 project. Then we can decide how much tweaking is really necessary to voice the amp for the HE60s.


----------



## luvdunhill

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Only thing I'm waiting for is for somebody to drop in the thread that didn't get PCBs, but builds an eXStata P-2-P! Surely somebody has thought about it already, right?_

 

... or make your own PCBs. Not much different from an IP standpoint as doing a P2P build. Just do a clean room design from the schematic and make it a one off.


----------



## les_garten

What are you guys yakkin' about?


----------



## pabbi1

Just poking AC in the eye with a sharp stick... you know, I think I have almost enough parts to consider a p2p - straight up or down, if I get a viable uber psu. 

 I mean, how hard can it be? Oy!

 La terra trema (such a great movie)...


----------



## BoilermakerFan

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_... or make your own PCBs. Not much different from an IP standpoint as doing a P2P build. Just do a clean room design from the schematic and make it a one off._

 

I'm a sheet metal and wood guy. I do casework, not PCBs. I rely on AC for the PCBs. I just try to case them up really pretty. 
	

	
	
		
		

		
			





 But, I also think there is an amazing elegance to P2P when it's done well. Of course, it can also look like an amp built by "ol' you know who" who is still AWOL.


----------



## BoilermakerFan

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_What are you guys yakkin' about?_

 

That you need to do a P2P eXStata.


  Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Just poking AC in the eye with a sharp stick... you know, I think I have almost enough parts to consider a p2p - straight up or down, if I get a viable uber psu. 

 I mean, how hard can it be? Oy!

 La terra trema (such a great movie)..._

 

Don't poke him in the eye, poke him in the... Ask me no more questions and I'll tell you no more lies... Isn't that how the old kids jingle goes?


----------



## luvdunhill

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_What are you guys yakkin' about?_

 

the good 'ole days mostly...


----------



## les_garten

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_That you need to do a P2P eXStata.



_

 

I was referring to the Mercury Vapor stuff?


----------



## Sathimas

I finally received my transformer today and am now thinking about the wire-routing and so on.

 Do I have to/can I connect the circuit to the groundpin of my ac-inlet?
 I mean the fuses of my flat react faster than the fuses in the amp...

 Unfortunately I won't be able to finish the amp this week although I have all the parts here...
 Just not enogh time


----------



## audionut

(Quote Boilermakerfan) Only thing I'm waiting for is for somebody to drop in the thread that didn't get PCBs, but builds an eXStata P-2-P! Surely somebody has thought about it already, right? 

 I'm planning on doing a P2P build in the near future. Probably going to do the SS version, since I already did the hybrid with the PC boards. Kinda' gettin' bored and need something to keep me busy, so, a P2P SS eXstata might just be the ticket!!


----------



## BoilermakerFan

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_I was referring to the Mercury Vapor stuff?_

 

Taking higher voltage tubes and making it even more dangerous! 
	

	
	
		
		

		
		
	


	




https://www.tubeworld.com/866a.htm

 Mercury vapor half-wave rectifier tubes for the PS.


----------



## les_garten

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Taking higher voltage tubes and making it even more dangerous! 
	

	
	
		
		

		
		
	


	




https://www.tubeworld.com/866a.htm

 Mercury vapor half-wave rectifier tubes for the PS._

 

Ahhh, Crazy man Crazy!


----------



## runeight

Despite the pokes in the eye and elsewhere it is IMHO that a p2p version will be detrimental to the amp. And also, very probably, a difficult build.


----------



## studeb

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Taking higher voltage tubes and making it even more dangerous! 
	

	
	
		
		

		
		
	


	




https://www.tubeworld.com/866a.htm

 Mercury vapor half-wave rectifier tubes for the PS._

 

Hi voltage?

 have a pair of beveridge speakers in the garage, if they were working the OTL amps would swing 6KV p2p


----------



## pabbi1

I sent Nick a couple of TWO RCA 83 MERCURY VAPOR RECTIFIER TUBES - eBay (item 170450683539 end time Mar-02-10 19:47:21 PST), and a couple of 1 NOS New In Box 1970's RCA 866A 866-A tube - eBay (item 270526443310 end time Mar-06-10 15:33:52 PST) - with sockets and tube caps. We'll see what happens, especially since I couldn't GIVE it away to anyone else, much less sell them at about 1/3 of what I paid. Shipped. 

 Seems like more folks are at least coming along.


----------



## runeight

You guys are nuts.


----------



## pabbi1

It took you how long to come to that conclusion?

 **Ok, I can't use emoteicons with the proxy (razorthought), but, certainly, all in jest. 

 Don't mind us, we're just all bored at work.

 I am going to roll in some of mid 1980 Russian goodness to my source, and out the crappy ElectroHarmonix tubes (creating all kinds of angst in Austria saying it so isn't necessary)... the insanity ain't just about amps.


----------



## BoilermakerFan

Hey Beefy,

 What is the spec of your SumR transformer again? Also, can you measure it's installed height? It just might fit under the sub-chassis in the Hallicrafters radios and if it does, then I'll use that instead of a R-Core.


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Despite the pokes in the eye and elsewhere it is IMHO that a p2p version will be detrimental to the amp. And also, very probably, a difficult build._

 

The pokes were not for a comment on P2P, but for a MV tube rectifier PS board. 
	

	
	
		
		

		
			





 I don't "have" to have the MV tube, a 0C3 (VR105) or 0D3 (VR150) would suit me just fine and look great behind the window:






  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_You guys are nuts._

 

Have to agree with pabbi1. You know, there are guys that take perfectly good exotic sports cars and tune them for even more insane performance, right? Just because they can. That's kind of how I see my eXStata evolving.


----------



## Beefy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Hey Beefy,

 What is the spec of your SumR transformer again? Also, can you measure it's installed height? It just might fit under the sub-chassis in the Hallicrafters radios and if it does, then I'll use that instead of a R-Core._

 

Primary: 115+115V at 50/60Hz.
 Secondary: 2x 240V at 62.5mA = 2x15VA

 Pre reg voltage varies between 325 and 345 depending on line voltage, which drops at 'peak' times of the day.

 Height is difficult for me to measure, but stated as 50mm. Allow a couple of extra mm for the foam damping.


----------



## les_garten

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_The pokes were not for a comment on P2P, but for a MV tube rectifier PS board. 
	

	
	
		
		

		
		
	


	




 I don't "have" to have the MV tube, a 0C3 (VR105) or 0D3 (VR150) would suit me just fine and look great behind the window:








 Have to agree with pabbi1. You know, there are guys that take perfectly good exotic sports cars and tune them for even more insane performance, right? Just because they can. That's kind of how I see my eXStata evolving. 
	

	
	
		
		

		
		
	


	


_

 

Are you tuning for more performance or putting on some of those spinner hubcaps on your sportscar?!


----------



## runeight

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_It took you how long to come to that conclusion?

 **Ok, I can't use emoteicons with the proxy (razorthought), but, certainly, all in jest. 

 Don't mind us, we're just all bored at work.

 I am going to roll in some of mid 1980 Russian goodness to my source, and out the crappy ElectroHarmonix tubes (creating all kinds of angst in Austria saying it so isn't necessary)... the insanity ain't just about amps._

 

I am, admittedly, a bit slow. But I'm thinking I should steer clear of you all for a while.

 Whenever I see you talking about gas regulator tubes I get nervous ...


----------



## BoilermakerFan

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_Are you tuning for more performance or putting on some of those spinner hubcaps on your sportscar?!_

 

Moar Powaar! Better brakes, stiffer suspension for better handling, and aftermarket stereo for better tunes! The usual quartet of improvements.

 Edit: How does that correspond to eXStata upgrades? No clue.


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I am, admittedly, a bit slow. But I'm thinking I should steer clear of you all for a while.

 Whenever I see you talking about gas regulator tubes I get nervous ..._

 

So we shouldn't ask for the GM70 output buffer at 700V? Say, we could use 6S4As to feed the GM70s then run 'em through 800V transistors...


----------



## runeight

&%*$*^(#@&^@!


----------



## Sathimas

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_I finally received my transformer today and am now thinking about the wire-routing and so on.

 Do I have to/can I connect the circuit to the groundpin of my ac-inlet?
 I mean the fuses of my flat react faster than the fuses in the amp...

 Unfortunately I won't be able to finish the amp this week although I have all the parts here...
 Just not enogh time_

 

Ah, sorry to interrupt you about shining tubes and so on but ... 
 I'd just like to repeat my question about the ground issue


----------



## BoilermakerFan

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_Ah, sorry to interrupt you about shining tubes and so on but ... 
 I'd just like to repeat my question about the ground issue_

 

Fuse the amp. Your flat fuse may be faster, but it's sized for a 15A load, so it will let well over 150A pass for 3 seconds before it even starts to really heat up to blow.


----------



## Sathimas

The amp will be fused in any way (one 300mA Fuse P and N each at the moment) , just wondering if/how I have to connect anything to the ground pin of the ac-inlet?


----------



## digger945

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_The amp will be fused in any way (one 300mA Fuse P and N each at the moment) , just wondering if/how I have to connect anything to the ground pin of the ac-inlet?_

 

If you are referring to the earth ground, over here it is used to ground the case of your project so that if a live wire were to contact the metal case it would have a path to follow back to the fuse box and then earth. 
 You might want to do some checking on your home wiring. First thing I would check is to see if ground and neutral are common. They are connected together inside the fuse box over here(in modern homes that I have wired.)
 This will tell you if you actually have a ground to work with, or if there has been a modern plug installed in your home and the ground pin left unconnected to anything.
 I will do some research and we can go from there.


----------



## macm75

Quote:


  Originally Posted by *paxeaxe23* /img/forum/go_quote.gif 
_OK, getting nearer now, but yet another dumb question. I now want to mount Q3 and Q4 on the amp board. does the circle opposite the thicker white line on the silkscreen denote where pin 1 or pin 3?_

 

Always remember datasheets exist. First, match picture on datasheet with device. Now you have the pins. Next, get out the schematic and see which device each pin is connected to. Lastly, the board shows the devices so just line up the proper pin.


----------



## ktm

Power supply is up and alive. So far, so good. 
 Case has been drilled for anything I can think up. Now it's time for 
 amp board wiring. I've got some 2 pair shielded 20ga I'm going to use for the heaters, 
 grounding the shield at the PS end. I have no idea how I want to
 wire out the rca jacks through to the pot. Normal wire, or should I butcher 
 some old mid level patch cables for the job?


----------



## Emooze

You need to have at least 600V rated wire if you want to route them anywhere near each other. PTFE/Teflon wire is pretty good stuff and can be had for a decently low price. Got mine off of ebay.


----------



## ktm

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_You need to have at least 600V rated wire if you want to route them anywhere near each other. PTFE/Teflon wire is pretty good stuff and can be had for a decently low price. Got mine off of ebay._

 

The input from the RCA's and into the board input will be on their own side of the case. The middle is where all the higher voltages will be at. I'll be working on that stuff tonight.


----------



## FrankCooter

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_So we shouldn't ask for the GM70 output buffer at 700V? Say, we could use 6S4As to feed the GM70s then run 'em through 800V transistors..._

 

So, are we going to see an eXStata "Extreme" at some point? A good start might be junking the 6s4's and substituting a dht output. Something like an Eimac 3c24 would do nicely. Of course you'd need to "man up" on the power supply. Get some Mercury in there and get that voltage UP! Might just "kick sand" in the face of a well known but slightly indolent high dollar amp!

 Seriously, I should finally have enough time in the next month or so to build my amp. Looking forward to showcasing it at the next NorCal meet.


----------



## sachu

man you guys are nuts...I think you all should first build the exstata in its current form and listen to it. WHile an extreme exstata is a mouth watering but quite deadly prospective, you guys surely are underestimating this amp without even listening to it.


----------



## les_garten

Quote:


  Originally Posted by *FrankCooter* /img/forum/go_quote.gif 
_So, are we going to see an eXStata "Extreme" at some point? A good start might be junking the 6s4's and substituting a dht output. Something like an Eimac 3c24 would do nicely. Of course you'd need to "man up" on the power supply. Get some Mercury in there and get that voltage UP! Might just "kick sand" in the face of a well known but slightly indolent high dollar amp!

 Seriously, I should finally have enough time in the next month or so to build my amp. Looking forward to showcasing it at the next NorCal meet._

 


 Don't tease me....


----------



## BoilermakerFan

Quote:


  Originally Posted by *FrankCooter* /img/forum/go_quote.gif 
_So, are we going to see an eXStata "Extreme" at some point? A good start might be junking the 6s4's and substituting a dht output. Something like an Eimac 3c24 would do nicely. Of course you'd need to "man up" on the power supply. Get some Mercury in there and get that voltage UP! Might just "kick sand" in the face of a well known but slightly indolent high dollar amp!

 Seriously, I should finally have enough time in the next month or so to build my amp. Looking forward to showcasing it at the next NorCal meet._

 

Hah hah haha, no the voltages on the eXStata are fine where they are. The 6S4As could be setup to split the load and be at 350V while the GM70 was at a "reasonable" 700V. I do like the look of mercury tubes, but they are a big hazard and not one that I would bring in my house while my kids are still young. The extent that I would go with it is to play with a tube rectified PS, but I wouldn't change the voltages or the rest of the eXStata.

 It was more of a "board at work, let's run with Al" post...

 EDIT: Sorry for the distracting siding, let's get the train back on the mainline.


----------



## audionut

Can anyone tell me if this socket from Allied is the correct one to use on Stax 404's? I know it's not a great quality socket, but I just need it for temporary testing. Cooper Interconnect - 78-S6S - Allied Electronics

 Thanks, Tommy


----------



## sachu

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Can anyone tell me if this socket from Allied is the correct one to use on Stax 404's? I know it's not a great quality socket, but I just need it for temporary testing. Cooper Interconnect - 78-S6S - Allied Electronics

 Thanks, Tommy_

 

Yes...that is it. It works quite well honestly. Just remove the middle pin using needle nose pliers.


----------



## audionut

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Yes...that is it. It works quite well honestly. Just remove the middle pin using needle nose pliers._

 

Thanks, Sachu. Glad to see you back!


----------



## macm75

Quote:


  Originally Posted by *ktm* /img/forum/go_quote.gif 
_I've got some 2 pair shielded 20ga I'm going to use for the heaters, 
 grounding the shield at the PS end. I have no idea how I want to
 wire out the rca jacks through to the pot. Normal wire, or should I butcher 
 some old mid level patch cables for the job?_

 

FWIW, shielded wire for the heaters is not necessary - I just twisted them - dead quiet amp.
 Input to RCA - twisted CAT6 wires works good - easy to get for free. Or any free substitute works too


----------



## les_garten

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_FWIW, shielded wire for the heaters is not necessary - I just twisted them - dead quiet amp.
 Input to RCA - twisted CAT6 wires works good - easy to get for free. Or any free substitute works too _

 

CAT6 seems a bit small for that?


----------



## paxeaxe23

OK I think I'm getting somewhere. After discovering that a 100V zener was the wrong way round (Oops) and of course correcting this I got the following readings after adjusting P1 and P2 respectively.

 T1 T2 302V
 T3 T4 298V

 T1 and T3 to ground only 309V and -309V respectively.

 I'm using the Triads and get 240 - 248V and my house is a bit low for the region at 224V AC

 Alex does say that T1 T3 relative to ground should be more than 320V -320V. It looks as if I've still got something wrong. 

 I would appreciate a bit of advise on what to check or do next!

 Thanks everyone for your help so far!


----------



## paxeaxe23

I should also add that the lo bias is set to 230V and the High to 580V no problem (except the slightly alarming arcing I got because I didn't put a test point pin on the high Bias


----------



## Emooze

Quote:


  Originally Posted by *ktm* /img/forum/go_quote.gif 
_The input from the RCA's and into the board input will be on their own side of the case. The middle is where all the higher voltages will be at. I'll be working on that stuff tonight._

 

My bad then.

 Also an eXStatA extreme is extremely tempting right now. Looking for summer projects anyways. I was going to put together a mercury power supply just to get my hands dirty.


----------



## Beefy

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_Also an eXStatA extreme is extremely tempting right now._

 

...... why on earth people would think this is a good idea, versus just building, say, a Blue Hawaii


----------



## sachu

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_...... why on earth people would think this is a good idea, versus just building, say, a Blue Hawaii 
	

	
	
		
		

		
			



_

 

haha what makes you think the exstata in its current form doesn't out perform/ match the BH. The BH can not even come close to the low end freq response that the exstata can deliver IME. The BH does have a touch sweeter midrange.

 The deal breaker ( not that i was ever interested in building one) with the BH personally has always been the lack of an authoritative low end freq response. Best way to put it is the BH is a more softer sounding amp as against the exstata which is an in your face, grab you by the nut sack kind of amp. 

 What I am impressed with is that the amp has responded very favorably to the CCS on the output. Having built both the versions it is immediately apparent that the current one is a hands over fist improvement over the prototype.


----------



## Beefy

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_haha what makes you think the exstata in its current form doesn't out perform/ match the BH. The BH can not even come close to the low end freq response that the exstata can deliver IME. The BH does have a touch sweeter midrange._

 

On the flipside, what makes you think a souped-up Exstata is going to sound better?


----------



## sachu

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_On the flipside, what makes you think a souped-up Exstata is going to sound better?_

 

i don't...that's why i was questioning the rationale in souping it up in the first place in my previous post. People haven't even built it let alone listened to it and are already taking about possible improvements.

 I wonder if even half the beta boards have seen completion thus far..


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_...... why on earth people would think this is a good idea, versus just building, say, a Blue Hawaii 
	

	
	
		
		

		
		
	


	


_

 

Never said it was a good idea. Just having a little fun with a Tim "The Toolman" Taylor'esque Moar Powaa moment while board at work yesterday. 

 As far as why I won't build a BH, it all comes down to personalities and designers. Some folks like Chevys, I prefer Fords. Is Chevy's fastest current production car a better performing vehicle than Ford's? Yes, yes it is. Would I keep a Corvette ZR-1 if given one? No, no I wouldn't. I'd sell it and wait for a new Saleen Mustang 5.0 GT and pocket the rest which would easily be 2/3s the cost of a $100K Corvette. Even within Ford tuners, I prefer Saleen over Shelby. 
	

	
	
		
		

		
		
	


	




 Car references make this easy.

  Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_On the flipside, what makes you think a souped-up Exstata is going to sound better?_

 

I don't think we believe that the eXStata needs to be improved or that all the side tack talk indicates anyone feels there is a need or room for improvement, especially at it's price point. I know I certainly don't think that and I haven't finished mine to even hold such an opinion. A tube rectified PS could make the eXStata sound muddy and slow, or just add noise. But, until it's built and auditioned, it's all just theory and fantasy talk as I want a bright purple glowing tube in the window of my chassis.


----------



## runeight

Given that this is mostly dreaming, I guess the question is, what is the real design goal? 2000Vpp. And why?

 Also, I agree with Saachu. Don't assume that the either BH or KGSS are better amps even though they most certainly can swing higher voltages or because they may cost more to build. I don't think enough square comparisons have been made yet.


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Given that this is mostly dreaming, I guess the question is, what is the real design goal? 2000Vpp. And why?

 Also, I agree with Saachu. Don't assume that the either BH or KGSS are better amps even though they most certainly can swing higher voltages or because they may cost more to build. I don't think enough square comparisons have been made yet._

 

Yeah, I just realized my car analogy falls apart on the performance comparisons. I guess that the eXStata vs. others would be comparable to a $45K SVT Mustang Cobra keeping up with a ZR-1. Man, why, o why, can't the automotive world parallel DIY Audio?

 EDIT: My only design goal was an aesthetic of a glowing rectifier tube. BUT, I'm not willing to sacrifice performance for the aesthetic look.


----------



## pabbi1

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_...... why on earth people would think this is a good idea, versus just building, say, a Blue Hawaii 
	

	
	
		
		

		
		
	


	


_

 

Let's remember, I _gave_ away a Blue Hawaii in deferrence to eXStatA and another design (Vulcan), both 6s4a based. This is not about trashing BH, but a choice based on LIVING WITH the beast after you build it. That is another thread, and no doubt, will be bloody, resulting in the ban stick for more than one party, so, I'll stop here. Period. Not even in PM.

 And, yes, I have heard the BHSE, in as good a rig as is available. My opinion stands. 

 I have lived with 3 different eXStatA for a while, and can be happy there, but, something keeps nagging me (not my wife) that it can be better, if not the "best, unquestioned" (to me, IMHO, with he60, yada) stat amp possible. THAT is what drives me, and, well, tortures Alex.

 Maybe it should stop here, but, the closed mouth never gets fed. Let's also remember THIS version would not exist had someone not recruited AC, and someone else decided to throw out a 'reasonable' product definition.

 My (personal) problem is that 'reasonable' is relative, and, more importantly, AC does NOT have to do *all* the heavy lifting, as we have seen in other designs as they have evolved. Since the base eXStatA came into existance with a pretty similar set of musings, what's the harm in talking about it? Obviously, more designers are reading along than meet the thread, or so I *believe*.

 Now, back to completing my new Vulcan psu, and see what's what. eXStatA might already have a little competition. Or, maybe a nap would be better - home with the flu - what better day to be working with 700v?

 Better turn off my phone, since AC might remember my number.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Let's remember, I _gave_ away a Blue Hawaii in deferrence to eXStatA and another design (Vulcan), both 6s4a based. This is not about trashing BH, but a choice based on LIVING WITH the beast after you build it. That is another thread, and no doubt, will be bloody, resulting in the ban stick for more than one party, so, I'll stop here. Period. Not even in PM.

 And, yes, I have heard the BHSE, in as good a rig as is available. My opinion stands. 
_

 

ARRRRRRGGGGGGGGHHHHHHHH! Al, I almost had the damn train back on the mainline again!


----------



## Beefy

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_I have lived with 3 different eXStatA for a while, and can be happy there, but, something keeps nagging me (not my wife) that it can be better, if not the "best, unquestioned" (to me, IMHO, with he60, yada) stat amp possible. THAT is what drives me, and, well, tortures Alex._

 

So its an OCD thing then.

 Look, I'm all for getting the most out of something, but the Exstata still isn't technically out of Beta. Nothing is served by turning discussion of the amp for intermediate DIY'ers into the amp for advanced madmen.

 *sigh* Its a real worry when the normally level-headed DIY sub-forum makes me just as frustrated as the other forums. We're supposed to be the sensible ones......


----------



## sachu

^^^
 Agreed..no harm in it..but i think we need to give the other builders an opportunity to build their amps and listen to it. Talking of further improvements to a design in beta could probbaly be done on another thread so this can be focussed on the beta builds.

 Anyone have a rough idea how many beta builds have seen fruition?


----------



## pabbi1

Like I said, I have the flu... 
	

	
	
		
		

		
		
	


	




 Probably more like impetuous than OCD. And, no one has ever considered me rational, nor sensible. Passion for music makes that improbable.


----------



## pabbi1

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_^^^
 Agreed..no harm in it..but i think we need to give the other builders an opportunity to build their amps and listen to it. Talking of further improvements to a design in beta could probbaly be done on another thread so this can be focussed on the beta builds.

 Anyone have a rough idea how many beta builds have seen fruition?_

 

I think Bill built 5, I built 3, you built 3(?), and I think we have another 10 or so done? Maybe we need a post for taking count of who is 'up', on each version?


----------



## sachu

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_I think Bill built 5, I built 3, you built 3(?), and I think we have another 10 or so done? Maybe we need a post for taking count of who is 'up', on each version?_

 

I have 4 completed...5th one is awaiting a power supply..it is giving me too many problems. Better to start afresh as rinse and repeat just isn't working.


----------



## macm75

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_CAT6 seems a bit small for that?_

 

Why would it that seem small to you? Plenty of builders out there that believe in extreme small guage wire is best for signals. 30 AWG - no problem.


----------



## ktm

Quote:


  Originally Posted by *Emooze* /img/forum/go_quote.gif 
_My bad then.

 Also an eXStatA extreme is extremely tempting right now. Looking for summer projects anyways. I was going to put together a mercury power supply just to get my hands dirty._

 


 No bad at all. Good advice never hurts. I've got some wire ready to go, and 
 I may hack up some the the I/C's I've got sitting around after the fact if I get
 an urge to look for improvement. That seems to be a common theme in this thread.


----------



## macm75

Quote:


  Originally Posted by *paxeaxe23* /img/forum/go_quote.gif 
_OK I think I'm getting somewhere. After discovering that a 100V zener was the wrong way round (Oops) and of course correcting this I got the following readings after adjusting P1 and P2 respectively.

 T1 T2 302V
 T3 T4 298V

 T1 and T3 to ground only 309V and -309V respectively.

 I'm using the Triads and get 240 - 248V and my house is a bit low for the region at 224V AC

 Alex does say that T1 T3 relative to ground should be more than 320V -320V. It looks as if I've still got something wrong. 

 I would appreciate a bit of advise on what to check or do next!

 Thanks everyone for your help so far!_

 

In previous posts I reported the exact same issue. I'm using a different PT than you but voltage results were the same. You will not properly regulate at 309V at the caps - after a minute my LED's went out. Need to change your diode string. I replaced my 91Vers with 75Vers - perfect after the change.


----------



## paxeaxe23

Quote:


  Originally Posted by *paxeaxe23* /img/forum/go_quote.gif 
_OK I think I'm getting somewhere. After discovering that a 100V zener was the wrong way round (Oops) and of course correcting this I got the following readings after adjusting P1 and P2 respectively.

 T1 T2 302V
 T3 T4 298V

 T1 and T3 to ground only 309V and -309V respectively.

 I'm using the Triads and get 240 - 248V and my house is a bit low for the region at 224V AC

 Alex does say that T1 T3 relative to ground should be more than 320V -320V. It looks as if I've still got something wrong. 

 I would appreciate a bit of advise on what to check or do next!

 Thanks everyone for your help so far!_

 

If I understand correctly, T1 and T3 are measuring at the CAPS. How can I troubleshoot and get the reading to go above 320V? I notice that the LEDs are only just lit up.

 Where now?

 Thanks


----------



## ktm

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_Why would it that seem small to you? Plenty of builders out there that believe in extreme small guage wire is best for signals. 30 AWG - no problem._

 


 Doubling up pairs would put it at 21ga. effectively. Everyone should have a box of cat 5/6 laying around! But for right now, I'm sticking with stranded.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_I think Bill built 5, I built 3, you built 3(?), and I think we have another 10 or so done? Maybe we need a post for taking count of who is 'up', on each version?_

 

I have one of Bill's on loan until mine is done, and it worked great from Xmas until a couple of weeks ago. But then recently it started sounding fuzzy (like a dirty record needle) during the first 10-15 minutes or so of warm up. And now the right channel doesn't clear up with warm up but the left does, although it only seems to sound fuzzy in the right channel on transients or peaks. It actually sounded clean the first 30-45 seconds of running from a cold start the last time I ran it. I've tried different sources and power/IC cables, different phones, turning down the input levels from a pre-amp, and moving it to another room.

 Bill is going to check it out this weekend, but I was wondering if any of you recognize the symptoms from my description and have any idea of what is up with it? The amp runs warm but not too hot to leave a hand on the top cover, and there is no burning smell. Inspecting the boards by eye reveals nothing unusual.


----------



## macm75

Quote:


  Originally Posted by *paxeaxe23* /img/forum/go_quote.gif 
_If I understand correctly, T1 and T3 are measuring at the CAPS. How can I troubleshoot and get the reading to go above 320V? I notice that the LEDs are only just lit up.

 Where now?

 Thanks_

 

I just posted behind you - read a few posts back. #2580


----------



## paxeaxe23

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_I just posted behind you - read a few posts back._

 

Yes, lots of posts all at once. I'll take a look back right now!


----------



## paxeaxe23

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_In previous posts I reported the exact same issue. I'm using a different PT than you but voltage results were the same. You will not properly regulate at 309V at the caps - after a minute my LED's went out. Need to change your diode string. I replaced one my 91Vers with 75Vers - perfect after the change._

 

Do I have to change the rail voltage down or can they stay at 300V if I change the zeners? and if so by how much?


----------



## pabbi1

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_I have one of Bill's on loan until mine is done, and it worked great from Xmas until a couple of weeks ago. But then recently it started sounding fuzzy (like a dirty record needle) during the first 10-15 minutes or so of warm up. And now the right channel doesn't clear up with warm up but the left does, although it only seems to sound fuzzy in the right channel on transients or peaks. It actually sounded clean the first 30-45 seconds of running from a cold start the last time I ran it. I've tried different sources and power/IC cables, different phones, turning down the input levels from a pre-amp, and moving it to another room.

 Bill is going to check it out this weekend, but I was wondering if any of you recognize the symptoms from my description and have any idea of what is up with it? The amp runs warm but not too hot to leave a hand on the top cover, and there is no burning smell. Inspecting the boards by eye reveals nothing unusual._

 

Sand or hybrid? Nothing like that on any of mine. If hybrid, maybe a tube... from experiences in the past, though these are many thousand hour rated.


----------



## macm75

Quote:


  Originally Posted by *paxeaxe23* /img/forum/go_quote.gif 
_Do I have to change the rail voltage down or can they stay at 300V if I change the zeners? and if so by how much?_

 

The zeners define the rail. If you change the string, the rail will change accordingly. You need a certain amount of voltage overhead for the regulator to work. Alex said you need at least 20V more at the caps to regulate at the 291V string (which gives 300V because the zeners are not perfect). If you have 308V at the caps, i would reduce the string by at least 12V. Remember that you might run at lower line voltage (relative to the last time you checked) so if your PT primary is low, the secondary will go lower (per transformer ratio). If secondary lower then lower volt at caps. Anyway, you should be fine at 275V string instead of 291V.
 The only other option is to get a different transformer to arrive at 320V at the caps. I think the 10 cent option is better. And the tubes and circuit does not care if it sees 280V instead of 300V. You will not hear a difference.


----------



## les_garten

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_Why would it that seem small to you? Plenty of builders out there that believe in extreme small guage wire is best for signals. 30 AWG - no problem._

 

My Mistake! I went back and re-read your post. I thought you were wiring the Heaters with CAT6! Hence my post...


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Sand or hybrid? Nothing like that on any of mine. If hybrid, maybe a tube... from experiences in the past, though these are many thousand hour rated._

 

Yeah, that would appear to be a tube or tubes issue if it's a hybrid.


----------



## Beefy

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Do you say that like Austin Powers
	

	
	
		
		

		
			



_

 

I do now. Here's a sneak peak......


----------



## Beefy

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_I have one of Bill's on loan until mine is done, and it worked great from Xmas until a couple of weeks ago. But then recently it started sounding fuzzy (like a dirty record needle) during the first 10-15 minutes or so of warm up._

 

Deja vu. Does it sounds a bit crackly even when no music is playing? What phones?


----------



## les_garten

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I do now. Here's a sneak peak......




_

 

Marc's Jacks look killer!


----------



## BoilermakerFan

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_Marc's Jacks look killer!_

 

And if white isn't your color, they can be dyed.


----------



## Beefy

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_Marc's Jacks look killer!_

 

Yes they do 
	

	
	
		
		

		
			





 I'm so glad I spent the extra money to have them recessed......


----------



## HeadphoneAddict

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Sand or hybrid? Nothing like that on any of mine. If hybrid, maybe a tube... from experiences in the past, though these are many thousand hour rated._

 

Hybrid - I did order the last of the RCA 6S4A set of 5 off eBay the other day, just in case.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Deja vu. Does it sounds a bit crackly even when no music is playing? What phones?_

 

No, it's quiet when I'm not playing any music. I've tried SR-003, Jade, woodied SR-Gamma Pro, and SR-Lambda normal bias.

 I may have some spare tubes from Pabbi1 that aren't matched, laying around here somewhere. And I ordered those RCA sets of 5 off eBay (got the last set out of several). So I will look around and try different tubes, or at least try moving them from one channel to the other to see if the problem moves with them.


----------



## paxeaxe23

Quote:


  Originally Posted by *macm75* /img/forum/go_quote.gif 
_The zeners define the rail. If you change the string, the rail will change accordingly. You need a certain amount of voltage overhead for the regulator to work. Alex said you need at least 20V more at the caps to regulate at the 291V string (which gives 300V because the zeners are not perfect). If you have 308V at the caps, i would reduce the string by at least 12V. Remember that you might run at lower line voltage (relative to the last time you checked) so if your PT primary is low, the secondary will go lower (per transformer ratio). If secondary lower then lower volt at caps. Anyway, you should be fine at 275V string instead of 291V.
 The only other option is to get a different transformer to arrive at 320V at the caps. I think the 10 cent option is better. And the tubes and circuit does not care if it sees 280V instead of 300V. You will not hear a difference._

 

Thanks very much. I'll take that on board. I actually have a big bag if 91V zeners here, so I might just swap out both 100V's for 91's which will give me 273V which will be easier than buying (and waiting for them to be sent!!!) some more zeners!

 Thanks again!


----------



## runeight

If you all will kindly remember that the exstata was designed to be a good amp at a reasonable price and seems to have exceeded those design goals. I really did think about this when designing the second version. The parts choices reflect this as does the topology, low OL gain, small NFB, biasing at the tail of the input stage, shunt regulated supply, etc.

 To try to stretch its design past a certain limit will not make sense. For example, if I were designing an amp to swing 1500Vpp or more it would use a different design for both the amp and probably the PS. Not that I have one in mind, I don't. But this amp is really targeted for its current operating point or maybe a little higher.

 However, it would be nice if some of you really slooooooooooooooow beta builders would get your butts in gear.


----------



## luvdunhill

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_*sigh* Its a real worry when the normally level-headed DIY sub-forum makes me just as frustrated as the other forums. We're supposed to be the sensible ones......_

 

this


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_However, it would be nice if some of you really slooooooooooooooow beta builders would get your butts in gear. 
	

	
	
		
		

		
		
	


	


_

 

99% there, Alex. I just need to do a touch more drilling into the base plate to secure my E24 and volume control PSU, and its all done 
	

	
	
		
		

		
		
	


	




 I'm 100% convinced that my crackling issues are my phones...... but I'm still getting occasional 'buzzing' from the power supply on power up. Any thoughts on that issue?


----------



## studeb

HeadphoneAddict;6449039 said:
			
		

> then recently it started sounding fuzzy (like a dirty record needle) during the first 10-15 minutes or so of warm up. And now the right channel doesn't clear up with warm up but the left does, although it only seems to sound fuzzy in the right channel on transients or peaks. It actually sounded clean the first 30-45 seconds of running from a cold start the last time I ran it. I've tried different sources and power/IC cables, different phones, turning down the input levels from a pre-amp, and moving it to another room.
> 
> 
> > after swapping tubes i would check the grounding on the heat sinks
> > and ground all four of them, not just the two on Alex's web page.


----------



## runeight

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_99% there, Alex. I just need to do a touch more drilling into the base plate to secure my E24 and volume control PSU, and its all done 
	

	
	
		
		

		
		
	


	




 I'm 100% convinced that my crackling issues are my phones...... but I'm still getting occasional 'buzzing' from the power supply on power up. Any thoughts on that issue?_

 

I've been thinking about this since it was first noticed. I never heard it in any of the proto or beta builds, but I'm sure its there.

 It is not charging the filter caps because they will charge within ms. I don't think its the shunt supplies either so I am wondering what the bias supplies are doing. Maybe the HV is skipping to a close ground point or some other component is vibrating in the HV swings? 

 It's also possible that the CCSs in the PS are oscillating. The fets have big gate stoppers and shouldn't do this, but fets are finicky.

 I don't have a good idea yet. What would be really helpful is if someone could identify the frequency and waveform of the buzz.


----------



## paxeaxe23

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_However, it would be nice if some of you really slooooooooooooooow beta builders would get your butts in gear. 
	

	
	
		
		

		
		
	


	


_

 

HOPEFULLY I'll be there by the week-end if I don't find any more reversed components or fried Transistors on the Amp board!


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I don't have a good idea yet. What would be really helpful is if someone could identify the frequency and waveform of the buzz._

 

It is difficult to get it to do it when hot, so I will let it cool down and see whether I can get a worthwhile recording with my webcam microphone.


----------



## WilCox

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_However, it would be nice if some of you really slooooooooooooooow beta builders would get your butts in gear. 
	

	
	
		
		

		
		
	


	


_

 

I've been listening to my SS eXStatA for the last few nights and I am most impressed. While I have never heard a KGSS, the eXStatA is doing to my phones exactly what I imagined a KGSS would do. That is, alleviate the laid-back quality of the O2 and wake them up. I have never enjoyed my O2s so much. Strangely, this is not a frequency response difference when compared to the SRM-717 or SRM-007, rather just more real power, control and extension.

 If it were a frequency response issue, then I would hear it in my 404LE which, while not as peaky as the standard 404, can get irritating with recording having overly hot mixes. Fact is the 404LE sound wonderful through the eXStatA.

 All in all, a most wonderful amp.


----------



## macm75

Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_alleviate the laid-back quality of the O2 and wake them up._

 

I wish to do the opposite with the SR-303's. I still think they sound too analytical but there are so many other very good attributes that the eXStata brings out that I cannot complain. I have enjoyed this amp every night for the past week. I find the sound fantastic but I do not soak in the notes - I imagine one gets more of that sweet luscious sound from the O2's.


----------



## pabbi1

Build count:

 Wiatrob: 5 
HeadphoneAddict - Hybrid
 sachu: 4
 ericj SS and Hybrid
 pabbi1: 3
 Hybrid 
 SS:Gliency
 Hybrid: jp11801
 audionut Hybrid
 TimJo Hybrid
 Sergery Hybrid
 Wilcox SS
 Beefy SS
 macm75 Hybrid
 emooze SS
 tommytank SS
 cyanoacry SS
 minivan Hybrid
 studeb SS
 ktm Hybrid
 padam Hybrid
 scooba SS
 paxeaxe SS
 Sathimas SS


 So, I get 30 up and running, pending Bill getting Larry sorted.

 Close: n_maher (for Hopstretch).

 And, the impressions thread can still use some entries.


----------



## sachu

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I'm 100% convinced that my crackling issues are my phones...... but I'm still getting occasional 'buzzing' from the power supply on power up. Any thoughts on that issue?_

 

I have had this on a couple of my proto builds and in the last beta build i did. However in the beta build, sometimes there is a buzzing, not always from the PSU on power on.


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_*sigh* Its a real worry when the normally level-headed DIY sub-forum makes me just as frustrated as the other forums. We're supposed to be the sensible ones......_

 

What? Who said we were supposed to be sensible? I know I did not receive that memo. 

 I build DIY so I can have over-the-top custom amps at a fraction of what their higher production commercial counter-parts cost. It may be a big fraction, but it's still a fraction. 
	

	
	
		
		

		
			





 And I know I'm one of the slow ass builders AC was referring too, and I'm ok with that. I'll get the Hybrid done a little faster than the SS. So new 
	

	
	
		
		

		
		
	


	




 ideas came to me this morning. No crazy changes to the BOM, just adding a carbon comp in the signal path after the gain stage to see if I like the little kiss of second harmonic sweetness, then a little eye candy customization.


----------



## Beefy

The top of my case went on for the first time tonight. Bias and offset are a lot more stable over both the short and long term which is great, but power supply voltage creeps as high as 310V with the added heat. That drops me down as low as 15V for regulation when my line voltage is at its minimum, so I'll have to keep a close eye on this......

  Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_I have had this on a couple of my proto builds and in the last beta build i did. However in the beta build, sometimes there is a buzzing, not always from the PSU on power on._

 

I wonder if it is 'max' versus regular versions? Mine is the 'max', if that helps us work this out......


----------



## HeadphoneAddict

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_I have one of Bill's on loan until mine is done, and it worked great from Xmas until a couple of weeks ago. But then recently it started sounding fuzzy (like a dirty record needle) during the first 10-15 minutes or so of warm up. And now the right channel doesn't clear up with warm up but the left does, although it only seems to sound fuzzy in the right channel on transients or peaks. It actually sounded clean the first 30-45 seconds of running from a cold start the last time I ran it. I've tried different sources and power/IC cables, different phones, turning down the input levels from a pre-amp, and moving it to another room.

 Bill is going to check it out this weekend, but I was wondering if any of you recognize the symptoms from my description and have any idea of what is up with it? The amp runs warm but not too hot to leave a hand on the top cover, and there is no burning smell. Inspecting the boards by eye reveals nothing unusual._

 

 Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_No, it's quiet when I'm not playing any music. I've tried SR-003, Jade, woodied SR-Gamma Pro, and SR-Lambda normal bias.

 I may have some spare tubes from Pabbi1 that aren't matched, laying around here somewhere. And I ordered those RCA sets of 5 off eBay (got the last set out of several). So I will look around and try different tubes, or at least try moving them from one channel to the other to see if the problem moves with them._

 

 Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_ Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
then recently it started sounding fuzzy (like a dirty record needle) during the first 10-15 minutes or so of warm up. And now the right channel doesn't clear up with warm up but the left does, although it only seems to sound fuzzy in the right channel on transients or peaks. It actually sounded clean the first 30-45 seconds of running from a cold start the last time I ran it. I've tried different sources and power/IC cables, different phones, turning down the input levels from a pre-amp, and moving it to another room.


 after swapping tubes i would check the grounding on the heat sinks
 and ground all four of them, not just the two on Alex's web page.

 

_

 

I typed this once before, and hit send and it disappeared, and I just can't spend another 30 minutes typing it again to be as good as it was before. 
	

	
	
		
		

		
		
	


	




 1) I'll have to get Bill to help with additional heatsink grounding if that is the issue. 

 2) Swapping the tubes between left and right channel made no difference.

 I have new information, that I hope might help diagnose the problem. This is an eXStatA with two volume pots, one for right and one for left. 

 1) If I turn down the right channel to zero and play music in the left, then the music sounds fine in the one channel, even when played loudly. 

 2) If I turn down the left channel to zero, and play music in the right, the distortion is heard in BOTH the left and the right. Somehow the distortion is coming through BOTH channels, despite the left volume being all the way down. If no music is making it through the off volume pot, I don't understand how the noise is getting into the left channel. 

 This is why I initially thought the distortion was in both channels, then changed my mind and thought it was only in the right, and then changed my mind again. The distortion almost sounds like something is clipping (input or output), which is weird to hear it in the left when the volume is all the way down. I am going to try disconnecting the left and right input interconnect cable, instead of turning down the volume, although common sense says the distortion is being introduced after the volume pot.

 3) The distortion seems related to the input volume. If I feed the the eXStatA from a DAC/preamp (Apogee mini-DAC or Nuforce HDP) or from iPod headphone out and I lower the input volume, then it seems to become less distorted. This results in very quiet listening levels below what someone would normally listen. I am going to try listening tonight with my fixed volume output Digital Link III again, and see how far I can turn up the amp before it distorts.


----------



## studeb

i know i am not a hardcore poster but i have a SS running
 and a hybrid on the way

  Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Build count:

 Wiatrob: 5 
HeadphoneAddict - Hybrid
 Saachu: 4
 ericj SS
 Pabbi1: 3
 Hybrid 
 SS:Gliency
 Hybrid: jp11801
 audionut Hybrid
 TimJo Hybrid
 Sergery Hybrid
 Wilcox SS
 Beefy SS
 macm75 Hybrid
 emooze SS
 tommytank SS
 cyanoacry SS
 minivan Hybrid


 So, I get 23 up and running, pending Bill getting Larry sorted.

 And, the impressions thread can use some entries._


----------



## sachu

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I wonder if it is 'max' versus regular versions? Mine is the 'max', if that helps us work this out......_

 

yes..all the ones i have built have been the max version.


----------



## runeight

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_I typed this once before, and hit send and it disappeared, and I just can't spend another 30 minutes typing it again to be as good as it was before. 
	

	
	
		
		

		
		
	


	




 1) I'll have to get Bill to help with additional heatsink grounding if that is the issue. 

 2) Swapping the tubes between left and right channel made no difference.

 I have new information, that I hope might help diagnose the problem. This is an eXStatA with two volume pots, one for right and one for left. 

 1) If I turn down the right channel to zero and play music in the left, then the music sounds fine in the one channel, even when played loudly. 

 2) If I turn down the left channel to zero, and play music in the right, the distortion is heard in BOTH the left and the right. Somehow the distortion is coming through BOTH channels, despite the left volume being all the way down. If no music is making it through the off volume pot, I don't understand how the noise is getting into the left channel. 

 This is why I initially thought the distortion was in both channels, then changed my mind and thought it was only in the right, and then changed my mind again. The distortion almost sounds like something is clipping (input or output), which is weird to hear it in the left when the volume is all the way down. I am going to try disconnecting the left and right input interconnect cable, instead of turning down the volume, although common sense says the distortion is being introduced after the volume pot.

 3) The distortion seems related to the input volume. If I feed the the eXStatA from a DAC/preamp (Apogee mini-DAC or Nuforce HDP) or from iPod headphone out and I lower the input volume, then it seems to become less distorted. This results in very quiet listening levels below what someone would normally listen. I am going to try listening tonight with my fixed volume output Digital Link III again, and see how far I can turn up the amp before it distorts._

 

This is another tough problem. My first thought is oscillation on the bad channel. This would be one way it would translate itself to the other channel (through the ps). Or a grounding problem or mixed up wiring.

 Other than this, it's hard for one channel to influence the other channel.


----------



## studeb

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_I have new information, that I hope might help diagnose the problem. This is an eXStatA with two volume pots, one for right and one for left. 

 1) If I turn down the right channel to zero and play music in the left, then the music sounds fine in the one channel, even when played loudly. 

 2) If I turn down the left channel to zero, and play music in the right, the distortion is heard in BOTH the left and the right. Somehow the distortion is coming through BOTH channels, despite the left volume being all the way down. If no music is making it through the off volume pot, I don't understand how the noise is getting into the left channel. The distortion almost sounds like something is clipping (input or output), which is weird to hear it in the left when the volume is all the way down. I am going to try disconnecting the left and right input interconnect cable, instead of turning down the volume, although common sense says the distortion is being introduced after the volume pot.

 3) The distortion seems related to the input volume. If I feed the the eXStatA from a DAC/preamp (Apogee mini-DAC or Nuforce HDP) or from iPod headphone out and I lower the input volume, then it seems to become less distorted. This results in very quiet listening levels below what someone would normally listen. I am going to try listening tonight with my fixed volume output Digital Link III again, and see how far I can turn up the amp before it distorts._

 

So i guess this is a single ended build, RCA jacks? They will share a common ground. As you have tried several sources, its not them, and likely not the cables.
 Any chance you can bypass the vol pots? It sounds like the problem is the right pot. What kind of pots are they?


----------



## BoilermakerFan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_This is another tough problem. My first thought is oscillation on the bad channel. This would be one way it would translate itself to the other channel (through the ps). Or a grounding problem or mixed up wiring.

 Other than this, it's hard for one channel to influence the other channel._

 

Was this the amp that arrived rearranged by UPS or USPS do to a loose screw? Perhaps damage was done in transit and it has just taken a while for the wound to bleed.


----------



## ericj

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Build count:

 Wiatrob: 5 
HeadphoneAddict - Hybrid
 Saachu: 4
 ericj SS
 Pabbi1: 3
 Hybrid 
 SS:Gliency
 Hybrid: jp11801
 audionut Hybrid
 TimJo Hybrid
 Sergery Hybrid
 Wilcox SS
 Beefy SS
 macm75 Hybrid
 emooze SS
 tommytank SS
 cyanoacry SS
 minivan Hybrid
 studeb SS


 So, I get 24 up and running, pending Bill getting Larry sorted.

 Close: studeb, ktm, paxeaxe23.

 And, the impressions thread can still use some entries._

 


 I have both SS and hybrid versions up and running - just neither fully enclosed. 

 The SS needs me to drill the faceplate. The hybrid needs me to get down to the actual business of enclosing it (and find metal for the faceplate). I've got the enclosure, I think i have the layout, haven't drilled to mount the boards yet or anything.


----------



## ktm

After the PS, I had high hopes. Not to be the case. No smoke, but problems.
 I'm running the older red hybrid boards. I'm getting 90 volts to ground from left + and -, and 105 volts to ground from right + and -.
 I used a matched set of 2sj74's and double checked them.
 Pretty close, and over 10(but not by much). I noticed the schematics
 seem to flop back and forth between using BC550c and 2n5550's.
 My version is using the BC550C's. I've looked over my wiring , and will go back through the boards tommorrow night.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_This is another tough problem. My first thought is oscillation on the bad channel. This would be one way it would translate itself to the other channel (through the ps). Or a grounding problem or mixed up wiring.

 Other than this, it's hard for one channel to influence the other channel._

 

That's what Bill was thinking. He's gonna check the grounding, and make sure the heat-sinks are all grounded.

  Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_So i guess this is a single ended build, RCA jacks? They will share a common ground. As you have tried several sources, its not them, and likely not the cables.
 Any chance you can bypass the vol pots? It sounds like the problem is the right pot. What kind of pots are they?_

 

I am using an RCA to XLR input adapter right now. The RCA jacks are wired to the XLR +/- but can be changed to common ground with a switch for each RCA if desired. And if something is plugged into the XLR jacks the RCA are also disabled.

 I think these are pretty decent alps pots. But with one pot per channel keeping the 2 from mixing at the pot, the noise has the getting into the system after the pots.

  Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Was this the amp that arrived rearranged by UPS or USPS do to a loose screw? Perhaps damage was done in transit and it has just taken a while for the wound to bleed._

 

Yes, this was the amp that didn't have nuts holding the PSU PCB in place, and so the PCB made a journey around the inside of the case and the underside was touching the case when I fired it up the first time. The bias wires had also gotten loose. I quickly discovered the problem and fixed it, but it could be coming back to haunt us now. It wasn't actually shipped, but it was put in a shopping bag sideways for my drive down from Denver, and it rattled loose during the ride. I'm trying to make arrangements now to drive the amp back up to Bill to sort it out. He's been really good to work with, and seems very knowledgeable.


----------



## runeight

Quote:


  Originally Posted by *ktm* /img/forum/go_quote.gif 
_After the PS, I had high hopes. Not to be the case. No smoke, but problems.
 I'm running the older red hybrid boards. I'm getting 90 volts to ground from left + and -, and 105 volts to ground from right + and -.
 I used a matched set of 2sj74's and double checked them.
 Pretty close, and over 10(but not by much). I noticed the schematics
 seem to flop back and forth between using BC550c and 2n5550's.
 My version is using the BC550C's. I've looked over my wiring , and will go back through the boards tommorrow night._

 

If you are building the red hybrid amp then you must use 2N5550s. The BC550s have a different pinout and lower voltage ratings and they, at this point, are probably toast. Other devices may have been taken out too, but first replace these transistors.


----------



## ktm

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_If you are building the red hybrid amp then you must use 2N5550s. The BC550s have a different pinout and lower voltage ratings and they, at this point, are probably toast. Other devices may have been taken out too, but first replace these transistors._

 

Thanks. That would explain it. I've got the 2n5550's here. I run a quick 
 check of the ksa1156's with the diode range of the meter while I'm at it.


----------



## bidoux

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_However, it would be nice if some of you really slooooooooooooooow beta builders would get your butts in gear. 
	

	
	
		
		

		
		
	


	


_

 

I'm not dead, still reading this thread quite often. I hope I can start as soon as possible and do that mouser order.


----------



## ktm

Wow. That is a pretty robust design. I changed out the BC550c's for the 2N550's,
 and did a quick check of the KSA1156's, and went for it.
 It's alive!. The ranges are now down where they should be. Not bad for a lunch hour swap out. 
 I will burn in and final adjust tonight. Next time, I should be asking these questions up front, 
 instead of blindly walking into the wall. Thank you sir for your help.


----------



## runeight

Quote:


  Originally Posted by *ktm* /img/forum/go_quote.gif 
_Wow. That is a pretty robust design. I changed out the BC550c's for the 2N550's,
 and did a quick check of the KSA1156's, and went for it.
 It's alive!. The ranges are now down where they should be. Not bad for a lunch hour swap out. 
 I will burn in and final adjust tonight. Next time, I should be asking these questions up front, 
 instead of blindly walking into the wall. Thank you sir for your help._

 

Happy to hear that it's alive. If I may remind you that the website does explain why the 2N5550 is used in the hybrid and why the BC550 is used in the SS version. That is, the schematics are not interchangeable for a reason.


----------



## ktm

ok, quick report. 
 Power supply- set t1/t2 at .360vdc and t3/t4 to .410 vdc.
 Showing 298.3/298.1 out and 314.7 and 312.7 at t1/t3.
 I'm able to set up the amp boards balance/ground reference,
 but they do drift around alot. Holding you hand close to them
 seems to cause them to drift with the heat increase, and go 
 back down when you pull away.
 I had both lights lit and the rails just up over 320 with 
 the resistor loads, but after my little oops,the rails are a bit lower,
 and re-adjusting the p1 to proper range causes the P1 side LED 
 to go off. If set a bit higher than 360, say 370, it lights. 
 I just had to fire it up for a test with the sr-40. It sounds good, 
 with a barely detectable bit of hum.
 I will watch it to see if any real ugliness pops up after today's mishap.
 Is there a old style sikscreen diagrams out there for the red board hybrid?
 I think I have a copy of the old schematic.


----------



## pabbi1

IIRC, the T1-T2 goes to 380mV, but wait on confirmation. I know the web page still has 360mV.


----------



## ktm

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_IIRC, the T1-T2 goes to 380mV, but wait on confirmation. I know the web page still has 360mV._

 

Thanks. That might be the ticket. So far, so good. I broke out the
 sr-202's and ran through the Tool test. At sane listening volumes, 
 it passes that test easy. I'm going to have to come up with a very
 open case top to keep this thing cool. It hits the low end hard and clean. 
 I'll try the sr-404's this weekend. 
 I really like Luvdunhill's jack. Worth every penny.


----------



## pabbi1

OUtstanding - and yes, that jack ought to be an industry standard.

 Hoping that turns out as well or better than what you heard at the Dallas meet.


----------



## studeb

An update on the screeching on power up. This is a SS build cased in a 20 port switchbox.

 played with some vairables tonite:
 remove the top, no screeching
 replace top - screeches
 remove ground replace top- screeches
 swap hot and neutral to trannies replace top - screeches

 any other ideas?
 as it only screeches with the top on, i do not think i can get a probe on it to measure or watch anything


----------



## padam

Updated with me:

 Wiatrob: 5 
 HeadphoneAddict - Hybrid
 Saachu: 4
 ericj SS
 Pabbi1: 3
 Hybrid 
 SS:Gliency
 Hybrid: jp11801
 audionut Hybrid
 TimJo Hybrid
 Sergery Hybrid
 Wilcox SS
 Beefy SS
 macm75 Hybrid
 emooze SS
 tommytank SS
 cyanoacry SS
 minivan Hybrid
 studeb SS
 padam Hybrid


----------



## WilCox

Got a new batch of J271s yesterday and sorted though them to get a closely matched pair at 11mA to replace those in the right channel which wouldn't balance correctly. Problem gone, balance now good --> sonic bliss!


----------



## runeight

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_An update on the screeching on power up. This is a SS build cased in a 20 port switchbox.

 played with some vairables tonite:
 remove the top, no screeching
 replace top - screeches
 remove ground replace top- screeches
 swap hot and neutral to trannies replace top - screeches

 any other ideas?
 as it only screeches with the top on, i do not think i can get a probe on it to measure or watch anything_

 

Can you please post some photos of the entire rig with some additional closeups?


----------



## audionut

Alex, Is the + rail adjusted to 360mV or 380mV? Mine was adjusted to 360mV per the website, and has run fine for over 3 months. Can readjust to 380 if that's what the recommendation is now. Thanks.


----------



## runeight

360mV/410mV are the correct values for the beta builds with the O/P CCS. Higher voltages(currents) were needed on proto boards with certain follower mods.

 However, if your rail voltages are running a lot higher than 300V then you may need to tweak the currents up by 1 or 2mA. This is because higher voltages will cause the amps to draw more current requiring more shunt current in the regs.

 If the LEDS are well lit and stay lit you are ok.


----------



## askforwhy

Quite a LONG thread.
 I really have lots to catch up on.


----------



## studeb

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Can you please post some photos of the entire rig with some additional closeups?_

 

that was all done with no input, and no phones connected

 will be done tonite, i knew you would want that.
 what closeups would you like?


----------



## runeight

just general closeups of your wiring, grounding, jacking, etc. And then in particular the area around the CCS heatsinks (the ones that are grounded).


----------



## luvdunhill

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_that was all done with no input, and no phones connected

 will be done tonite, i knew you would want that.
 what closeups would you like?_

 

what do you mean by "no input"? Do you have a pot connected, or if not, are the inputs shorted?


----------



## studeb

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_what do you mean by "no input"? Do you have a pot connected, or if not, are the inputs shorted?_

 

um, yeah no pot, inputs not shorted.
 i had to disconect from the rest for this experiement.
 dare i ask why?


----------



## Hottuna_

Just received luvdunhill's stax jack in the mail.
 Very nicely made I have to say.
 First step in my potential build.


----------



## studeb

i tested adding a load to the input (Sony discman) and it will still make the noise.
 pics of my casing, they should be clickable thumbnails:


----------



## les_garten

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_i tested adding a load to the input (Sony discman) and it will still make the noise.
 pics of my casing, they should be clickable thumbnails:



















_

 

Looks like an old terminal server box you have it in.

 Hope it's not a Portmaster


----------



## ericj

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_i tested adding a load to the input (Sony discman) and it will still make the noise.
 pics of my casing, they should be clickable thumbnails:_

 

Is the enclosure earthed? I can't tell from the pictures.


----------



## studeb

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_Is the enclosure earthed? I can't tell from the pictures._

 

Yes the encosure is earthed. From one of the transformer mounting screws.
 The boards are not grounded green wire to the plug.

 And it was an Inova MREM 16. i can ge another one for you.....


----------



## ktm

How much drift is normal?
 The amp board out + and - seem to move around in balance.
 We are talking about a couple of volts at times, and then come back?
 Putting a book over the part of the case over the amp boards so they 
 stay heated up seems to keep them closer to setting. T1/t2 as well as t3/t4
 also tend to drop down in value as the amp warms. I've seen it drop 
 down to 368/399 when it really gets warmed up.


----------



## Beefy

Quote:


  Originally Posted by *ktm* /img/forum/go_quote.gif 
_How much drift is normal?
 The amp board out + and - seem to move around in balance.
 We are talking about a couple of volts at times, and then come back?_

 

My offset is usually centered around ±500mV, but sometimes drifts up to ±1V. It is entirely related to temperature changes as the amp warms up, and settles down once everything is evenly 'hot'. Only one channel sees balance drift - the 'cool' one away from the PSU - but it also settles down when hot.

  Quote:


 T1/t2 as well as t3/t4 also tend to drop down in value as the amp warms. I've seen it drop down to 368/399 when it really gets warmed up. 
 

Yes, I've seen this as well - mine drops by up to 10mV lower with the case lid on compared to open for testing. But the LEDS stay brightly lit and the shunt BJT heatsinks are still very warm so I figure that I'm still getting good regulation.

 My biggest concern is still my PSU voltage drifting up to 310V. I'm seriously considering switching out a 100V zener for a 91V on each rail to bring it down just a bit to give better headroom for voltage regulation and to decrease heat output a touch.


----------



## ktm

My concern is because of the stress I created when I put the wrong transistors 
 in. I think I'll have to break out , GASP,test equipment and dust off what little
 skills I've got. I still have a scope around here somewhere and a tube tester.
 I'm going to check the tubes and see if they are in the ballpark with each other, 
 and poke around a bit. I may even go back to running the PS on 
 the test load to make sure it stays put for a while. Nothing worse than 
 having just enough skills to be dangerous.


----------



## ktm

ok, there's a problem. I ran tests on all for tubes on the old Hickok.
 Minimum is a rating of 3000, I've got 3600, 3300,3200, 2200.
 Average should be 4150. I really must of drove them hard after
 that screw up. That would explaing my trouble with stability.
 Time to order a new set.


----------



## pabbi1

I have a set, or two...


----------



## Postal_Blue

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_I have a set, or two... _

 

Any chance I could snag a set? I was gonna grab one from the last ebay deal, until you posted it here before I pulled the trigger hehe!


----------



## Tachikoma

Erm, any chance that this project is going to go out of "beta" soon? Would love to order a kit (as this would also be my first DIY amp <_<)


----------



## pabbi1

Keith, that is really odd, that tubes could be chewed up that bad... ping me if you want a tested quad.

 Assuming 2 quads test out, Postal the second set is yours. But, that is all I have extra.


----------



## ktm

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Keith, that is really odd, that tubes could be chewed up that bad... ping me if you want a tested quad.

 Assuming 2 quads test out, Postal the second set is yours. But, that is all I have extra. 
	

	
	
		
		

		
		
	


	


_

 

I really should of read through better before firing up the amps. 
 Most likely that was the problem cause. You have a pm.


----------



## luvdunhill

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_But, that is all I have *"*extra*"*. 
	

	
	
		
		

		
			



_

 

FTFY


----------



## runeight

Quote:


  Originally Posted by *ktm* /img/forum/go_quote.gif 
_ok, there's a problem. I ran tests on all for tubes on the old Hickok.
 Minimum is a rating of 3000, I've got 3600, 3300,3200, 2200.
 Average should be 4150. I really must of drove them hard after
 that screw up. That would explaing my trouble with stability.
 Time to order a new set._

 

I also doubt that the tubes are causing your problems. Could you please remind me of the problem.

 Thanks.


----------



## ktm

Power supply is set at 380/410. + and - are running 298.
 I set the balance and ground reference, and I'm getting a ton of drift.
 The t1/t1 and t3/t4 drop. T1 and t3 to ground go to 313.
 The + and - left and right drift a lot, often going over a couple of
 volt when I measure each channel output. Just getting my hand
 over p1/p2 with my adjustment tool changes the readings.
 Pulling to test, the bad tube under test slowly drops in value. The other
 three drift slightly higher under test. The Hickok tester shows the bad 
 tube testing firmly under "replace". The other three test in the green. 
 The tester is older than dirt, but seems to function well enough. 
 Either way, the one tube needs to be addressed. There could very well be 
 other problems. But strangely enough, the sound of the amp is very good. 
 I do have 67K 3w resistors in place of R13,14,15,16,17,18.
 I was going to dig my scope out of storage, but when I found the tube,
 I stopped. I decided to address the obvious first. I spent the afternoon 
 whipping up the front panel and drilling holes in the cover.
 I have been running without a cover for testing.
 I think on Sunday I will go back to the test loads on the power supply to make
 sure it will stay stable. Then it's off into the amp boards.
 I may also change out the 2js74's and the ksa1156's if the problem persists.


----------



## pabbi1

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_FTFY 
	

	
	
		
		

		
		
	


	


_

 

Very accurate - I continue to be VERY active in the 6s4a market. Let's say I just really like this tube.

 Oh, and guys, if you see a deal (quad or sleve of 5), don't hesitate, especially if they are <$5 each shipped. That is what TubeDepot charges, $3.95 + ship, so about $5.25 shipped CONUS.


----------



## paxeaxe23

We have changed the Zener string to 3x 91V 273V and get the following readings:
 after adjusting T1-T2 and T3 - T4 to 360mV and 410mV respectively.

 T1 to Ground and T3 to ground 309V (+/- 0.5V)
 279V -279V (+/- 0.5V) at the Rails

 Still no LED's but Horst reckons it is Regulating because he made readings of the "Brumspannung" (Which I just translated as Ripple Voltage) and said it is negligible. [I'm not sure if this is a red Herring or not]

 If I understand the criterion correctly, a voltage difference of nearly 30V should be fine, [too large a difference?] but why don't the LED's light up?

 Regardless we attached the Amp and after following the instructions on Alex's site got the offset and Balance readings to well under 1VDC.

 What should I look at next to get the LED's to light up?

 Thanks


----------



## macm75

Quote:


  Originally Posted by *paxeaxe23* /img/forum/go_quote.gif 
_We have changed the Zener string to 3x 91V 273V and get the following readings:
 after adjusting T1-T2 and T3 - T4 to 360mV and 410mV respectively.

 T1 to Ground and T3 to ground 309V (+/- 0.5V)
 279V -279V (+/- 0.5V) at the Rails

 Still no LED's but Horst reckons it is Regulating because he made readings of the "Brumspannung" (Which I just translated as Ripple Voltage) and said it is negligible. [I'm not sure if this is a red Herring or not]

 If I understand the criterion correctly, a voltage difference of nearly 30V should be fine, [too large a difference?] but why don't the LED's light up?

 Regardless we attached the Amp and after following the instructions on Alex's site got the offset and Balance readings to well under 1VDC.

 What should I look at next to get the LED's to light up?

 Thanks_

 

Alex specified 320-350 at the caps for 300V rail. You're good there.
 When I did not have enough overhead voltage my 350mA and 410mA did not hold. After a minute's time it started to drop. Sound like your regulating fine.
 Why LED's not on? Sorry I cannot help.


----------



## Beefy

My Exstata is now done. More pics and details here in the build thread......


----------



## jp11801

While I did not build mine, I have the one that Pabbi1 built I must say this is an outstanding amp. I have mine powering a pair of 404 LE earspeakers and I am in audio heaven. 

 I've owned a bunch of gear over the past 6 years here on headfi and this set up is right up there with the best of them. Kudo's to the design team and to Al for building this outstanding amp. Great clarity, extension, tone and dynamics.


----------



## pabbi1

Welcome to the club, and ever so glad you are enjoying it. The design holds a LOT of promise. I am continually amazed by things like 'Subterranean Homesick Alien' - just ethereal. It is also fun to cycle through my 400 discs just to see what jumps out

 To answer a previous question, that extra Vpp may now solve my clipping on Monster Magnet... 

 Oh, and guys, we all owe Dr Cavalli at least some input to the impressions thread... por favor... maybe I'll look a little less like the lone fanboi, since there are 27 up and running.

 Beefy, that is just sweet, well, except for your, like, missing tubes.


----------



## Beefy

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Beefy, that is just sweet, well, except for your, like, missing tubes. 
	

	
	
		
		

		
		
	


	


_

 

BAH! Because of the height I would have had to spoil that gorgeous black top plate.....


----------



## luvdunhill

damn Beefy... that's fantastic looking!


----------



## Beefy

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_damn Beefy... that's fantastic looking!_

 

As I said in the build thread, the look was only possible with your awesome Stax jacks...... and I wouldn't enjoy using the amp nearly as much with any other volume control. So thanks for the help, and for the kind words


----------



## sachu

Sweet build Beefy...I could take some notes from your build for my own future builds..Well planned and laid out.


----------



## pabbi1

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_As I said in the build thread, the look was only possible with your awesome Stax jacks...... and I wouldn't enjoy using the amp nearly as much with any other volume control. So thanks for the help, and for the kind words 
	

	
	
		
		

		
		
	


	


_

 

Well, yours is only cool until we see Nate's... 
	

	
	
		
		

		
		
	


	




 And Marc's jacks really should be the standard Stax jack for all time. Heck, I bought one (I have 3 now) just to have around and look at - or, you know, for some future build.

 Listening to Verve Pipe 'Veneer' - just magnificent beauty. Where is my Oasis 'Stop the Clocks'?

 This amp just keeps on giving.


----------



## runeight

Really nice work Beefy, all the way around.

 And you couldn't find a place to put the word eXStatA in teeny tiny letters anywhere on that beautiful box?? I am hurt.


----------



## luvdunhill

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Really nice work Beefy, all the way around.

 And you couldn't find a place to put the word eXStatA in teeny tiny letters anywhere on that beautiful box?? I am hurt. 
	

	
	
		
		

		
			






_

 

perhaps he wasn't sure if the name would change, or is only the color of the boards that change each time


----------



## HeadphoneAddict

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_My Exstata is now done. More pics and details here in the build thread......




_

 

Wow beefy, that looks great! I love the front panel, even if "eXStatA" is missing from it. 
	

	
	
		
		

		
		
	


	




 Can we get a shot of the rear panel?


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Really nice work Beefy, all the way around.

 And you couldn't find a place to put the word eXStatA in teeny tiny letters anywhere on that beautiful box?? I am hurt. 
	

	
	
		
		

		
		
	


	





_

 

 Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_perhaps he wasn't sure if the name would change, or is only the color of the boards that change each time 
	

	
	
		
		

		
		
	


	


_

 


 Still an omission that could/should have been avoided especially when going with custom engraved panels.


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Really nice work Beefy, all the way around.

 And you couldn't find a place to put the word eXStatA in teeny tiny letters anywhere on that beautiful box?? I am hurt. 
	

	
	
		
		

		
		
	


	





_

 

Thanks Alex, I'm really happy you like it 
	

	
	
		
		

		
		
	


	




 I was soooo close to calling it the Exstata SS instead, but I made a vow when I built my Buffalo DAC - before I was committed to building an Exstata - that I wouldn't put any specific project names on any of my panels. Silly distinction I know, but that was my design rule. Also, no personalized logos, and no unnecessary engraving or pieces of metal.

 Rest assured, everybody who asks will know exactly what she is! 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Wow beefy, that looks great! I love the front panel, even if "eXStatA" is missing from it. 
	

	
	
		
		

		
		
	


	




 Can we get a shot of the rear panel?_

 

I linked to a bigger post above. Check it out here: http://www.head-fi.org/forums/6462917-post6539.html


----------



## TimJo

Quote:


  Originally Posted by *jp11801* /img/forum/go_quote.gif 
_While I did not build mine, I have the one that Pabbi1 built I must say this is an outstanding amp. I have mine powering a pair of 404 LE earspeakers and I am in audio heaven. 

 I've owned a bunch of gear over the past 6 years here on headfi and this set up is right up there with the best of them. Kudo's to the design team and to Al for building this outstanding amp. Great clarity, extension, tone and dynamics._

 

This is the setup I have as well, and it is good to know that someone with a greater exposure to headphone systems agrees that the eXStatA/404LE combo is simply amazing...


----------



## ericj

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Wow beefy, that looks great! I love the front panel, even if "eXStatA" is missing from it. 
	

	
	
		
		

		
		
	


	




 Can we get a shot of the rear panel?_

 

huh. I just realized that, since i have access to a vinyl cutter, i should be able to stencil something real nice onto my amps . . . .


----------



## HeadphoneAddict

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_huh. I just realized that, since i have access to a vinyl cutter, i should be able to stencil something real nice onto my amps . . . ._

 

Good thing you used wood instead of metal.


----------



## ericj

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Good thing you used wood instead of metal. 
	

	
	
		
		

		
		
	


	


_

 

eh? I'm using metal, I just can't stomach the cost of FPE panels.


----------



## Sathimas

Things are taking shape ...





 (Got the panels from schaeffer ("FPE") today, hope to get the amp working arround next week)


----------



## BoilermakerFan

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_Things are taking shape ...





 (Got the panels from schaeffer ("FPE") today, hope to get the amp working arround next week)_

 

Sathimas - 

 I get large pop-ups that launch and block your pics every time I try to view your image in a larger size. No way to close it, it just blocks your image.


----------



## pabbi1

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_Things are taking shape ...

 (Got the panels from schaeffer ("FPE") today, hope to get the amp working arround next week)_

 

Looks very nice - and even I get the photos, but I go through a proxy.


----------



## les_garten

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_Things are taking shape ...





 (Got the panels from schaeffer ("FPE") today, hope to get the amp working arround next week)_

 


 I thought FPE had the edges silver on their black anodized stuff?


----------



## adamus

looks silver to me


----------



## Sathimas

What do you mean when you talk about "edges" ?

 The case is made bei hifi 2000 in Italy, I only sent the panels to schaeffer to get the holes drilled and so on.

 So the parts are black anodized, where material was removed of course the silver aluminium can be seen.


----------



## les_garten

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_What do you mean when you talk about "edges" ?

 The case is made bei hifi 2000 in Italy, I only sent the panels to schaeffer to get the holes drilled and so on.

 So the parts are black anodized, where material was removed of course the silver aluminium can be seen._

 

Hmmm, OK. The pic is a little strange to look at, the holes look like they are anodized. I also didn't understand who shaeffer is, you had FPE in parentheses. Basically don't sweat it.


----------



## Lil' Knight

Schaeffer is a branch of FPE in Europe.


----------



## les_garten

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_Schaeffer is a branch of FPE in Europe._

 


 Ahhhh...


----------



## ktm

After re-reading the thread, a question about the 269jx.
 Do you have three input leads, white, Black(125volt in) and gray(115v in)?
 And if so, which one did you use? The specs say it was a production mod,
 so not all of them have it. My wall power was close to 125VAC, so 
 I used the black lead. I tried the gray lead while up on the test loads,
 and the t1/t3 voltages jump up to 348 volts. That would require me to
 go to all 100 volt zeners? Good idea or bad idea? The other lead gave me 
 just over 320 volts at t1/t3. Both give me about 299 vdc at the rails.
 If I ever go somewhere that the voltage is down to 115vac, The t1/t3
 wouldn't have much overhead to feed the rails.
 I've been working on the front plate while working out my tube issues. 
 The front and top look presentable now. I'll never be another "Dr. Wood".
 Not even close!


----------



## Sathimas

The picture was taken with my mobile phone, thats why the colors are so strange.


----------



## luvdunhill

I've gotten a few questions about the volume board that Beefy used in his build. I'm considering making a few more boards, but would like a few beta builders who are comfortable with SMD and willing to actually build the board in a reasonable time frame and offer feedback. I won't be able to build this version any time soon and there are are a few changes this go around that need to be tested. I'd be willing to provide a preprogrammed microcontroller, two PGA chips, and the board itself. If anyone would like to help, please PM me. Thanks!


----------



## BoilermakerFan

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_I've gotten a few questions about the volume board that Beefy used in his build. I'm considering making a few more boards, but would like a few beta builders who are comfortable with SMD and willing to actually build the board in a reasonable time frame and offer feedback. I won't be able to build this version any time soon and there are are a few changes this go around that need to be tested. I'd be willing to provide a preprogrammed microcontroller, two PGA chips, and the board itself. If anyone would like to help, please PM me. Thanks!_

 

I'll send you a PM too, but I'm setting up a reflow oven.


----------



## luvdunhill

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_I'll send you a PM too, but I'm setting up a reflow oven. 
	

	
	
		
		

		
		
	


	


_

 

unfortunately, this is a two sided board (I find the hot plate technique to work better than a toaster oven).. but it's easy enough to solder. I've extended the pads quite a bit on the SOIC devices which makes it easier. I wouldn't say this is any harder than any of amb's projects, if not easier.


----------



## BoilermakerFan

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_unfortunately, this is a two sided board (I find the hot plate technique to work better than a toaster oven).. but it's easy enough to solder. I've extended the pads quite a bit on the SOIC devices which makes it easier. I wouldn't say this is any harder than any of amb's projects, if not easier._

 

No worries. The oven I'm using is IR on top and I can use just the top element, so you solder one side, flip it, and surface tension plus lower heat holds the chips on the bottom while the top reflows.


----------



## Beefy

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_unfortunately, this is a two sided board (I find the hot plate technique to work better than a toaster oven).. but it's easy enough to solder. I've extended the pads quite a bit on the SOIC devices which makes it easier. I wouldn't say this is any harder than any of amb's projects, if not easier._

 

Can't say much for the documentation though...... 
	

	
	
		
		

		
		
	


	




 But seriously, I had few troubles putting one together, even with a standard 1.6mm Hakko tip and fairly coarse solder. Better tweezers would be the one thing I would invest in before doing another, because the resistors are tiny - but the chips were indeed very easy.


----------



## spritzer

Same here, very easy to assemble with a 2mm Metcal chisel tip and .031" solder. Both of mine would beup and running now if Mouser wasn't holding the capacitors I ordered hostage.


----------



## jpancier

Ok, so I'm new to DIY amp's, but I was wondering if its possible to build an eXStatA without a printed circuit board? They seem to be pretty tough to get a hold of. Can I point to point wire it from the available diagrams? I'll be building another couple of amps first, but I'd like to order the parts all together if possible.


----------



## runeight

It is my opinion that this will be a difficult p2p build because of the care needed to keep high voltages apart while keeping components as close together as possible. But, I know that someday someone will do this.


----------



## cat6man

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_It is my opinion that this will be a difficult p2p build because of the care needed to keep high voltages apart while keeping components as close together as possible. But, I know that someday someone will do this. 
	

	
	
		
		

		
		
	


	


_

 

Hi,
 Is there any plan to have another run of boards anytime soon?


----------



## runeight

Well...right now I am going through a major transition from one important and dependable client to two new ones because the old one is going away. I'm going to have to pay serious attention to this for a while. So I don't know at the moment.


----------



## The Monkey

I heard an eXStata today at the NYC Meet. I was very impressed.


----------



## ktm

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Well...right now I am going through a major transition from one important and dependable client to two new ones because the old one is going away. I'm going to have to pay serious attention to this for a while. So I don't know at the moment._

 

I know how hard business can be right now. Take care of it.
 You have helped many of us out with this project, and I for 
 one have to thank you. Good luck with the new accounts.


----------



## ktm

Here's a quick shot of mine.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *The Monkey* /img/forum/go_quote.gif 
_I heard an eXStata today at the NYC Meet. I was very impressed._

 

That's cool. I'm curious who's build was it? Hybrid or Solid State?


----------



## pabbi1

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_That's cool. I'm curious who's build was it? Hybrid or Solid State?_

 

THINK it's mine - a red board proto hybrid. I'm waiting on Kerry's observation, comparing that with his from-scratch Blue Hawaii build. Maybe JP will weigh in as well... btw, this will all hopefully show in the NY meet impressions thread (I am watching). 

 Edit: Understood Ari had one as well - Nate???

 Keith, is everything sorted on yours? And, NABU for the win.


----------



## ktm

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_
 Keith, is everything sorted on yours? And, NABU for the win. 
	

	
	
		
		

		
		
	


	


_

 

I've go a quad of 6s4a's coming in. I think moving over to the 115vac
 lead of the transformer seems to be better. The rails hold steady just under 300vdc.
 I still get drift on the outputs and to ground, but I'm hoping
 the new tubes help. Either way, it sounds good. I may still change out
 the 91 volt zeners for 100volt zeners. There is enough extra to do it now.
 Before, the +/- sometimes went down to 313vdc, and the rails dropped
 a volt or two. I think it's safe to say there may be a couple of my other
 Stax amps for sale soon.


----------



## cetoole

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_THINK it's mine - a red board proto hybrid. I'm waiting on Kerry's observation, comparing that with his from-scratch Blue Hawaii build. Maybe JP will weigh in as well... btw, this will all hopefully show in the NY meet impressions thread (I am watching). 

 Edit: Understood Ari had one as well - Nate???

 Keith, is everything sorted on yours? And, NABU for the win. 
	

	
	
		
		

		
		
	


	


_

 

Yeah Al, it was your ExStata at the meet, and she was sounding mighty fine with JP's SR404ltd and Ari's DEQ2496. Really looking forward to getting the few bits I still need for my SS build. Sure was hot though.


----------



## pabbi1

Thanks, Colin... you and Nate need to get it in gear... and let me know if I can help with those bits... 
	

	
	
		
		

		
		
	


	




 Going old school tonight with Depeche Mode (pre Violator), The Smiths, Mighty Lemon Drops, Echo & The BunnyMen, Smithereens, and a little Styx. Nothing throws this amp, especially with the better source.

 Ok, except the stupid clips on Monster Magnet...


----------



## Scooba

Well, thanks to Anthony, I've joined the build team 
	

	
	
		
		

		
		
	


	




 .
 I already have all the components for the amp (SS), but I still have to order the ones for the power source (except transformer) . 
 Which brigs me one problem: I can not find FQP3P50 . It seems that nobody has it on stock . Can it be replaced with something else ?

 After some digging, I found MTP2P50EG - are these ok (75W max, 2A) ?


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Thanks, Colin... you and Nate need to get it in gear... and let me know if I can help with those bits... 
	

	
	
		
		

		
		
	


	


_

 






 He's waiting on bits from me... Long running trade for his old RP18s. 

 They'll be in next week and flipped quickly so he'll be ready to build in a week.

 EDIT:He might be waiting on jacks from Marc too, yeah, that's it!


----------



## cat6man

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Well...right now I am going through a major transition from one important and dependable client to two new ones because the old one is going away. I'm going to have to pay serious attention to this for a while. So I don't know at the moment._

 

understand........good luck with your work!


----------



## wkumar

Hello all. I've read this thread with great interest. I really want one of these amps, but don't have the skills to build it completely myself. I've only done passive circuits like crossovers and filters. It's hard to start with a 600V one!

 Anyone here interested in building a hybrid ExStatA? Otherwise, anyone know someone in the New York area who I can lean from? I know it's a long shot, but I thought I'd try.


----------



## Beefy

Finally got around to making a sound recording of the buzz my PSU makes on power up. The file attached is the best I can do with a webcam mike and Head-Fi's file size limit - hope it is acceptable to give an idea of what is going on.

 I still can't find anything else wrong, the PSU works as normal when the buzzing stops, and the buzzing doesn't happen when the PSU is warm......


----------



## runeight

This is helpful. If you can try listening to the bias section near the power inlet and see if the noise is coming from there.


----------



## runeight

I mean the power inlet terminal on the PS board.


----------



## les_garten

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Finally got around to making a sound recording of the buzz my PSU makes on power up. The file attached is the best I can do with a webcam mike and Head-Fi's file size limit - hope it is acceptable to give an idea of what is going on.

 I still can't find anything else wrong, the PSU works as normal when the buzzing stops, and the buzzing doesn't happen when the PSU is warm......_

 

I couldn't get the MP3 to extract for some reason.


----------



## studeb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Finally got around to making a sound recording of the buzz my PSU makes on power up. The file attached is the best I can do with a webcam mike and Head-Fi's file size limit - hope it is acceptable to give an idea of what is going on.

 I still can't find anything else wrong, the PSU works as normal when the buzzing stops, and the buzzing doesn't happen when the PSU is warm......_

 

i can not extract it either


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I mean the power inlet terminal on the PS board._

 

No, definitely coming from somewhere between the caps and the heatsinks. And it is two separate noises, seeming to come from each rail. The negative rail almost always stops buzzing first; in the file I posted it was a rare case when they stopped together.

 Also, getting up so close and personal with the amp, I just noticed that the LEDs on a particular rail are a touch brighter while the noise is happening on that rail.

  Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_I couldn't get the MP3 to extract for some reason._

 

Sorry, re-done with legacy compression.


----------



## WilCox

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_This is helpful. If you can try listening to the bias section near the power inlet and see if the noise is coming from there._

 

A piece of surgical tubing or even a straw makes a nice makeshift stethoscope to find noisy components. 
	

	
	
		
		

		
			





 Speaking of problems, I am curious how much offset Stax headphones can tolerate. My eXStatA SS has about a 12-15V balance missalignment in one channel upon power-up the settles to less than 1V after 20-30 minutes. (The other channel is <1V from the start.)

 Will this harm my phones?


----------



## studeb

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_ Sorry, re-done with legacy compression._

 

That works, same sound as mine.
 i played with the lid, as long as the lid is within one inch it will buzz.
 and when that buzzing stops, i can hear the transformers buzz. not sure if they buzz the whole time not.


----------



## les_garten

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_No, definitely coming from somewhere between the caps and the heatsinks. And it is two separate noises, seeming to come from each rail. The negative rail almost always stops buzzing first; in the file I posted it was a rare case when they stopped together.

 Also, getting up so close and personal with the amp, I just noticed that the LEDs on a particular rail are a touch brighter while the noise is happening on that rail.



 Sorry, re-done with legacy compression._

 

WOW! That's quite a buzz you got there!


----------



## Beefy

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_WOW! That's quite a buzz you got there!_

 

That file is plus 24dB 
	

	
	
		
		

		
		
	


	




 It is _just_ loud enough to hear with the lid on.


----------



## runeight

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_No, definitely coming from somewhere between the caps and the heatsinks. And it is two separate noises, seeming to come from each rail. The negative rail almost always stops buzzing first; in the file I posted it was a rare case when they stopped together.

 Also, getting up so close and personal with the amp, I just noticed that the LEDs on a particular rail are a touch brighter while the noise is happening on that rail.

 Sorry, re-done with legacy compression._

 

And I think you said that you've tried grounding all of the heatsinks? 

 The difference in LED brightness is a normal variation because the CCS settings are inexact, but close enough.

 This is, obviously, an oscillation, but it is an audio frequency oscillation which is, in itself, peculiar.

 The fets could be oscillating (even with the gate stoppers), but their freqs are usually much higher.

 The shunt regs themselves could be unstable for some reason, but their gain is not that high and there really isn't any global nfb as there would be if there were a differential error amplifier. There is gain, but not a huge amount relative to other types of regs.

 Furthermore, there are 1u caps on the outputs to stop oscillation.

 Etc. etc. etc.

 So my only useful thought is, if it changes when the top cover is moved closer/farther then the only things on the board that could have any significant capacitative coupling to the top are the heatsinks and, therefore, grounding these should stop the problem.


----------



## gilency

I have a question for Mr Cavalli:
 Glass Jar Audio sells some of your designs as a kit. Do you think it would be possible for them or somebody else to eventually sell them that way?
 There are plenty of people who would love to get the eXStata. 
 Would that be a way to increase the availability of this wonderful amp?


----------



## sachu

Quote:


  Originally Posted by *gilency* /img/forum/go_quote.gif 
_I have a question for Mr Cavalli:
 Glass Jar Audio sells some of your designs as a kit. Do you think it would be possible for them or somebody else to eventually sell them that way?
 There are plenty of people who would love to get the eXStata. 
 Would that be a way to increase the availability of this wonderful amp?_

 

I think it has been talked about before and that Jeff from glass jar has indicated that he would not be able to take on more kits at this point.


----------



## runeight

I have been in touch with GJA recently because of the other of my amps that Jeff carries. Without speaking for Jeff, I would guess the GJA is saturated with the products that it now sells.

 Given all of my other committments at this moment I am thinking it may be a while before these boards come out again. Furthermore, I have been working on determining if other of my amps designs which have not been made available on this forum are good candidates for commercial products. Taking this step would be a significant undertaking. Thus, any free time that I have now, which is slim, will probably go into this investigation and, obviously, cannot be discussed on the diy part of headfi.

 However, in the original thread posted by ericj there were other ideas proposed for stat amps. Maybe someone else can come up with a good, cheap design in the meantime? 
	

	
	
		
		

		
		
	


	




 Edit: I see that Sachu beat me to a reply. He usually does.


----------



## Keithpgdrb

Sachu, you may want to re-word your signature about commissioned builds. I dont even know you, and it rubbed me the wrong way. I'm sure your a great guy, but that signature is pretty harsh. Just trying to keep the Karma good.


----------



## gilency

Thank you Sachu and runeight. I look forward for any other electrostatic ventures Mr Cavalli may have. Either DIY or commercially available.


----------



## sachu

Quote:


  Originally Posted by *Keithpgdrb* /img/forum/go_quote.gif 
_Sachu, you may want to re-word your signature about commissioned builds. I dont even know you, and it rubbed me the wrong way. I'm sure your a great guy, but that signature is pretty harsh. Just trying to keep the Karma good._

 

I will consider it...but I have good reason to keep it strongly worded.


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_And I think you said that you've tried grounding all of the heatsinks?_

 

That was someone else, but I can ground the PSU heatsinks easily enough.

  Quote:


 The difference in LED brightness is a normal variation because the CCS settings are inexact, but close enough. 
 

Just focusing on a single rail though, the LED is brighter while the buzzing is happening. It dulls a touch when the buzzing stops. So perhaps the buzzing indicates extra current moving through the shunt. Though I suppose this could be an issue with regulation, or the FETs supplying extra current.

  Quote:


 The shunt regs themselves could be unstable for some reason, but their gain is not that high and there really isn't any global nfb as there would be if there were a differential error amplifier. There is gain, but not a huge amount relative to other types of regs. 
 

I recall reading that the 'Max' modification increases gain at some point. Could this be unique to Max builds?

  Quote:


 So my only useful thought is, if it changes when the top cover is moved closer/farther then the only things on the board that could have any significant capacitative coupling to the top are the heatsinks and, therefore, grounding these should stop the problem. 
 

That was somebody else; lid on or off doesn't seem to bother my build. But I will ground the heatsinks to see if this helps.


----------



## pabbi1

Quote:


  Originally Posted by *Keithpgdrb* /img/forum/go_quote.gif 
_Sachu, you may want to re-word your signature about commissioned builds._

 

Sadly, his wording is appropriate, and might could be stated even stronger. It is what it is, to keep everyone in 'good standing'.

 For you hybrid guys, there are 3 five tube sleves of matched construction on eBay. Price has increased a wee bit.


----------



## Beefy

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_That was somebody else; lid on or off doesn't seem to bother my build._

 

You know, I might need to retract this......

 The amp was sitting with the top panel open this morning, I powered it up and there was no buzz. This wasn't that unusual, because it doesn't buzz every single time. But thinking back to studeb's issue I put the lid back on, powered it up, and it did buzz. Lid off, amp on, no buzz. Lid on, amp on, buzz. Very reproducible, until the amp warmed up enough such that the buzz with lid on stopped.

 It has definitely buzzed in the past with the lid off - the recording I made yesterday was lid off - so there is more to it that _just_ that. But it is certainly an interesting phenomenon. I will ground the heatsinks tonight.


----------



## runeight

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_That was someone else, but I can ground the PSU heatsinks easily enough.



 Just focusing on a single rail though, the LED is brighter while the buzzing is happening. It dulls a touch when the buzzing stops. So perhaps the buzzing indicates extra current moving through the shunt. Though I suppose this could be an issue with regulation, or the FETs supplying extra current.



 I recall reading that the 'Max' modification increases gain at some point. Could this be unique to Max builds?



 That was somebody else; lid on or off doesn't seem to bother my build. But I will ground the heatsinks to see if this helps._

 

Thanks. Could you guys please remind me whether the buzzing builds are hybrids or SS. Or one of each.

 Just to eliminate possibilities, in the hybrid, before the tubes conduct there will be different current relationships among the parts and less current draw from the PS which means more shunt current until the tubes warmup. Although there is no reason for this to be a problem since the bjts can handle amps.


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Thanks. Could you guys please remind me whether the buzzing builds are hybrids or SS. Or one of each._

 

Ah, crosspost....... as I said just seconds ago, the case lid does have an effect.

 Mine is solid state.


----------



## runeight

Then it can't be the warmup period, so I'm back to suspecting heatsink coupling issues. If can find time to ground them all that would be the next step. If your output G from the PS terminal block goes to the star ground then wire the heatsinks to that point on the board.


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Then it can't be the warmup period, so I'm back to suspecting heatsink coupling issues. If can find time to ground them all that would be the next step. If your output G from the PS terminal block goes to the star ground then wire the heatsinks to that point on the board._

 

Sounds like a plan!


----------



## Beefy

Well grounding the heatsinks didn't seem to help...... but I didn't get much testing done after something sparked/popped on power up 
	

	
	
		
		

		
		
	


	




 It was something in the area of R1, R3, R5, R9, Z1 and Q1. In-circuit resistances of the resistors checks out and since nothing is in parallel they should be good. For Q1, C-B resistance is >10Mohm, C-E resistance is >10Mohm, B-E resistance is 118ohm (P1 + R1 +R3, so no dead short). The only thing I can't test is the zener.

 LEDs still light, output voltage seems stable, but the voltage across T1-T2 was unstable. I wasn't game to try keep it going for any length of time though, just in case.

 Any additional suggestions before I continue?


----------



## WilCox

Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_Speaking of problems, I am curious how much offset Stax headphones can tolerate. My eXStatA SS has about a 12-15V balance misalignment in one channel upon power-up the settles to less than 1V after 20-30 minutes. (The other channel is <1V from the start.)

 Will this harm my phones?_

 

Just asking this again in case someone here has some experience or insights they could share.

 Thanks!


----------



## Beefy

Well I checked everything on the PSU very closely, and could not find a single fault, no burnt up components, nothing. So I gave it a clean up with isopropanol, wired it back and, and every reading was A-O-K. So I don't know what sparked... maybe a hair or piece of dust?

 In any case, I'm a bit frazzled tonight, so will re-test the heatsink grounding tomorrow.


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Well I checked everything on the PSU very closely, and could not find a single fault, no burnt up components, nothing. So I gave it a clean up with isopropanol, wired it back and, and every reading was A-O-K. So I don't know what sparked... maybe a hair or piece of dust?

 In any case, I'm a bit frazzled tonight, so will re-test the heatsink grounding tomorrow._

 

No buzz after the reassembly?


----------



## Beefy

Yes, still buzz.


----------



## runeight

Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_Just asking this again in case someone here has some experience or insights they could share.

 Thanks!_

 

I am not a stat headphone expert but it seems to me that we have headphones that are designed to handle 1000V or more between the stators so 15V for a few minutes seems harmless to me.

 Beefy, probably right, a piece of something or maybe solder flux. Spacing can be close on these boards, even though all spacing conforms to the recommended values for coated PCBS.

 I really don't know what the deal is with your PS. I wish I could offer you better help.


----------



## BoilermakerFan

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Yes, still buzz._

 

Just to rule it out completely, can you turn your trafo 90 degrees or remove it from the chassis all together and patch on extensions? Your transformer is just a hair undersized and that would only be an issue at start up during the inrush and while everything settle down, but mechanical vibration and larger EMI fields occur when a trafo is fully loaded or overloaded. It's a shielded and potted unit, but that doesn't completely eliminate EMI. Turning it should matter since it's a toroid, but that may be easier than removing it initially. 

 It's a low probability, but might as well eliminate it.


----------



## spritzer

Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_Just asking this again in case someone here has some experience or insights they could share.

 Thanks!_

 

DC has almost no effect on the cans besides lowering their efficiency and in the grand scope of things 15V is nothing. All the Single Power ES amps shipped with a fixed offset of -100VDC or more and some designs have a rather high offset but compensate by increasing the bias voltage. Just look at the DC-coupled sibling of the GES which sits at +200V.


----------



## runeight

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Yes, still buzz._

 

Have you tried firing up in the dark to see if you can see any arcing? You may need to look at both top and bottom of the board.


----------



## WilCox

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I am not a stat headphone expert but it seems to me that we have headphones that are designed to handle 1000V or more between the stators so 15V for a few minutes seems harmless to me.

 Beefy, probably right, a piece of something or maybe solder flux. Spacing can be close on these boards, even though all spacing conforms to the recommended values for coated PCBS.

 I really don't know what the deal is with your PS. I wish I could offer you better help._

 

 Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_DC has almost no effect on the cans besides lowering their efficiency and in the grand scope of things 15V is nothing. All the Single Power ES amps shipped with a fixed offset of -100VDC or more and some designs have a rather high offset but compensate by increasing the bias voltage. Just look at the DC-coupled sibling of the GES which sits at +200V._

 

Thanks guys! You are confirming what I hoped/expected. 
	

	
	
		
		

		
		
	


	




 I really enjoy this amp and its performance with both 404LE and O2 is outstanding in view of its meager cost.


----------



## Beefy

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_It's a low probability, but might as well eliminate it._

 

I recall it buzzing when uncased, while the toroid was a decent distance from the PSU. I really doubt this is it.

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Have you tried firing up in the dark to see if you can see any arcing? You may need to look at both top and bottom of the board._

 

I can certainly try it.


----------



## pabbi1

Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_Thanks guys! You are confirming what I hoped/expected. 
	

	
	
		
		

		
			





 I really enjoy this amp and its performance with both 404LE and O2 is outstanding._

 

FTFU.

 Grrrrrrrrr - performance should be completely seperated from cost.


----------



## sachu

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_FTFU.

 Grrrrrrrrr - performance should be completely seperated from cost._

 

soo true...have noticed that very few people in this hobby have had this revelation in the relatively short period of 7 years I have been doing this. In this hobby meaning DIY audio in general. 

 All credit goes to the designer. 
	

	
	
		
		

		
		
	


	




 Easily the total cost can exceed 1000$ even for this design based on what kind of casing and boutique parts, if any you opt for.


----------



## audionut

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_soo true...have noticed that very few people in this hobby have had this revelation in the relatively short period of 7 years I have been doing this. In this hobby meaning DIY audio in general. 

 All credit goes to the designer. 
	

	
	
		
		

		
		
	


	




 Easily the total cost can exceed 1000$ even for this design based on what kind of casing and boutique parts, if any you opt for._

 

Totally agree!
	

	
	
		
		

		
		
	


	




 This amp still amazes me more everyday, and I still can't believe the level of performance this amp achieves. Not to mention how easy it is to build! Glad I got in on this one, and hope it will still be offered to others in the future at some point.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_DC has almost no effect on the cans besides lowering their efficiency and in the grand scope of things 15V is nothing. All the Single Power ES amps shipped with a fixed offset of -100VDC or more and some designs have a rather high offset but compensate by increasing the bias voltage. * Just look at the DC-coupled sibling of the GES which sits at +200V.*_

 

What amp is that?


----------



## WilCox

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_FTFU.

 Grrrrrrrrr - performance should be completely seperated from cost._

 

Agreed! I'm listening more to my eXStatA SS than my 007tA or 717 and enjoying every minute of it!


----------



## nattonrice

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_What amp is that?_

 

HeadWize - Project: All-Triode Direct-Drive Amps for Electrostatic and Electret Headphones by Kevin Gilmore

 Everything sits at 300v and swings around it.
 Bias is lifted to 860v to give 560v relative to the stators.


----------



## spritzer

Ahh it was 300V. 
	

	
	
		
		

		
		
	


	




 Crazy expensive to build though with the high voltage Apex opamps. There is also another Gilmore all tube DC amp but I don't think anybody except the good doctor has built a functional unit yet. Rather cool design with a lot of tubes and needs at least 3 different filament supplies to work correctly. It's been on my to-do list for a while now but I just need to order some 6h30pi's.


----------



## manaox2

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_FTFU.

 Grrrrrrrrr - performance should be completely seperated from cost._

 

I'm banking on it being a great amp and certainly a value one, but I think I would want people keep in mind how much was accomplished for so little when giving credit to the designer. This design isn't the end all be all, for more money projected in adding to the circuit I think the design itself could possibly be improved. Its the bang for the buck for me when I judge performance which is how equipment should be judged IMO. I don't think anyone should judge it as being on the low end because it doesn't quite measure up to a BHSE without taking into consideration that the BHSE costs 10x as much.


----------



## pabbi1

You know, I happen to have several 6h30pi laying around (yanked the wretched EH gold pins out of the Ayon for some 1985 mil marked Reflektors), but dayum, even the mid 80s are $100, and I found some 1978 for $150 each. Were one of my Russian friends would do some buying when they visit the homeland.

 Certainly more builds are close to coming online?

 Oh, I do think it is in the conversation with the BHSE, and ASR did also at the Dallas meet, who owns a BHSE. At the NY meet, a BH judged as a 10 compared to my red board proto as an 8. While we can all disagree over scale, and if/how much better final is over proto, price really isn't all that relevant.

 I would like to see the comparison with a 350v psu - to wit, if anyone wants to let me buy a set of boards for the express purpose of bumping the psu to 350v, and modding the amp accordingly (if needed), ping me. There is one such effort afoot, albeit at a leisurely pace...


----------



## n_maher

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_I don't think anyone should judge it as being on the low end because it doesn't quite measure up to a BHSE without taking into consideration that the BHSE costs 10x as much._

 

These comparisons never work, like Al said it's best to just leave them out of it. If the Exstata was ever built commercially it would cost many multiples of its own part's cost and so on. So compare sonics all you want, but leave the dollars out as it only muddies the water. That's my 2¢ anyway.

 Oh, and I thought the hybrid Exstata I heard in Boston sounded very nice.


----------



## manaox2

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_These comparisons never work, like Al said it's best to just leave them out of it. If the Exstata was ever built commercially it would cost many multiples of its own part's cost and so on. So compare sonics all you want, but leave the dollars out as it only muddies the water. That's my 2¢ anyway.

 Oh, and I thought the hybrid Exstata I heard in Boston sounded very nice._

 

Oh, I think I get what your saying now, comparing sonics and leaving price out would be best. 
	

	
	
		
		

		
		
	


	




 So easier said then done.


----------



## spritzer

With the BH and T2 designs so much money is spent on utter overkill that is is hard to compare on price alone. There are certainly cheaper ways to make the same designs both in terms of parts used and the sheer number of parts but we like overkill. 
	

	
	
		
		

		
		
	


	




 Even the Vulcan has a lot of parts for a simpler version... 

 In terms of price/performance I do think the ESX is the hardest to beat though as it can be built for peanuts and sounds damn close to the modern CCS filled monsters. With 7f7's/EL34's it sounds very clean and controlled even if I running it a tad out of spec. All point-to-point though but pretty easy to do. I also did one on a perfboard (mini ESX) which was even easier to to. 

  Quote:


  Originally Posted by *pabbi1* 
_You know, I happen to have several 6h30pi laying around (yanked the wretched EH gold pins out of the Ayon for some 1985 mil marked Reflektors), but dayum, even the mid 80s are $100, and I found some 1978 for $150 each. Were one of my Russian friends would do some buying when they visit the homeland._

 

Crazy prices indeed. Might be better to just drop some ECC99's into that KG design...


----------



## sachu

Quote:


  Originally Posted by *spritzer* /img/forum/go_quote.gif 
_With the BH and T2 designs so much money is spent on utter overkill that is is hard to compare on price alone. There are certainly cheaper ways to make the same designs both in terms of parts used and the sheer number of parts but we like overkill. 
	

	
	
		
		

		
		
	


	




 Even the Vulcan has a lot of parts for a simpler version... _

 

overkill doesn't necessarily translate into sonic goodness..

 The true genius is in making it sound great while keeping it simple..the great doctor Cavalli manages this in each of his designs.

 This is the reason his works translate into actual working amps.

 Can we get back to the builds and more impressions on the exstata now?


----------



## spritzer

As usual you have no idea what you are talking about.


----------



## n_maher

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Can we get back to the builds and more impressions on the exstata now?_

 

Let's try this, I don't really want to start deleting posts.


----------



## pabbi1

Which proto was in Boston? And, when will Hop's Nugget Audio eXStatA get some love from the public at large?

 Off topic, but yes, my Vulcan now has one of Kerry's BH 350v psu, so the cross pollinization continues. Evolution always finds the best answer.


----------



## n_maher

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Which proto was in Boston? And, when will Hop's Nugget Audio eXStatA get some love from the public at large?_

 

It was your prototype (jp#s). And Hop's amp is back on the bench so at least he'll get to hear it "soon". I think we're on front panel #6 design wise but I think we're done tweaking now and can move to production.


----------



## WilCox

Here's my eXStatA:













 Pretty much a standard build. I've got a GoldPoint attenuator and Luvdunhill 
 Stax jacks on the way for the next build!

 Thanks to Alex for this wonderful design and thanks to Nate for the Alps.


----------



## audionut

Wilcox, Very nice looking build
	

	
	
		
		

		
		
	


	




 Could you possibly give me the info or link for the case you used? Thanks, Tommy.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_
 I would like to see the comparison with a 350v psu - to wit, if anyone wants to let me buy a set of boards for the express purpose of bumping the psu to 350v, and modding the amp accordingly (if needed), ping me. There is one such effort afoot, albeit at a leisurely pace... _

 

I was fairly sure Bill has a 350 or 400v PSU at home. I don't know more than that.

  Quote:


  Originally Posted by *WilCox* /img/forum/go_quote.gif 
_Here's my eXStatA:





 Pretty much a standard build. I've got a GoldPoint attenuator and Luvdunhill 
 Stax jacks on the way for the next build!

 Thanks to Alex for this wonderful design and thanks to Nate for the Alps. 
	

	
	
		
		

		
		
	


	


_

 

Nice build. How is the Alps working for you, and can you tell me what model and price it is?


----------



## WilCox

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Wilcox, Very nice looking build
	

	
	
		
		

		
		
	


	




 Could you possibly give me the info or link for the case you used? Thanks, Tommy._

 

Thanks! It's a Hammond RMCV190313BK1 available from Mouser RMCV190313BK1 Hammond Racks & Cabinets
  Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Nice build. How is the Alps working for you, and can you tell me what model and price it is?_

 

It's a 10K 4-gang RK27 that I purchased from Nate, since he had a spare. I believe he ordered them from a German seller on eBay and they go for ~$50.


----------



## audionut

I have a working 350V supply also that I have for my KGSS. It would be easy to hook up to my exstata hybrid, but not sure if that's a good idea and whether it could possibly damage my amp. Maybe Alex or someone else could shed some light on whether this is ok to try and whether it might benefit from 350V rails vs the 300V originals.:bigsmile_face


----------



## WilCox

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Nice build. How is the Alps working for you, and can you tell me what model and price it is?_

 

Well Larry, the Alps is working out very well! I purchased a GoldPoint 50K attenuator for the eXStatA, but I put the Alps in to just to get the amp up and running. I am happy enough with the excellent tracking of the pot and the great performance of the amp that I'm not even thinking about replacing the Alps with the GoldPoint at this point, but will save it for the next build.


----------



## luvdunhill

I have a few more spots for people willing to try the balanced attenuator mentioned in this thread. It's mostly SMD, so fair warning there. For those willing to get cracking on it immediately, I'm discounting the parts by 50% and throwing in the board.

 Also, for those waiting on jacks they'll go out on Monday. Sorry again for the delay.


----------



## cat6man

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_I have a few more spots for people willing to try the balanced attenuator mentioned in this thread. It's mostly SMD, so fair warning there. For those willing to get cracking on it immediately, I'm discounting the parts by 50% and throwing in the board.

 Also, for those waiting on jacks they'll go out on Monday. Sorry again for the delay._

 

i'll go for one. 
 sent email

 thanks


----------



## Beefy

Has anybody measured the actual current draw of their amps?

 I took my PSU out to switch in an extra pair of 91V zeners to drop the output voltage with no troubles*, and things are now sitting nicely at 295-300V. But in stress testing and checking, I noted again that my CCS current drops as low as 38mA on the negative rail and 32mA on the positive rail...... but the shunt transistor heatsinks are still stinking hot.

 I would measure it myself, but don't have any way of securing the multimeter in series that will handle the voltage......

 [size=xx-small]* But bloody hell, physical access was tough![/size]


----------



## luvdunhill

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I would measure it myself, but don't have any way of securing the multimeter in series that will handle the voltage......_

 

perhaps measure the current draw on the primary side, then do a bit of math?


----------



## Beefy

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_perhaps measure the current draw on the primary side, then do a bit of math?_

 

That wouldn't really help...... the current draw will be what I set it to at the CCS, and I'll still be none the wiser as to how much current goes through the amp versus the current that is shunted for regulation.


----------



## studeb

Beefy,

 Did you ground the PS heatsinks, and did that stop the buzzing?


----------



## Beefy

Quote:


  Originally Posted by *studeb* /img/forum/go_quote.gif 
_Did you ground the PS heatsinks, and did that stop the buzzing?_

 

I only had them grounded for a short time, due to something sparking - probably a shaving of aluminium from the tapped heatsinks.

 But it didn't help.


----------



## Scooba

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_I have a few more spots for people willing to try the balanced attenuator mentioned in this thread. It's mostly SMD, so fair warning there. For those willing to get cracking on it immediately, I'm discounting the parts by 50% and throwing in the board.

 Also, for those waiting on jacks they'll go out on Monday. Sorry again for the delay._

 

May I join the attenuator team ?

 I've received my Mouser order Friday. I've finished mounting both the PS and amp (SS), but I am still waiting for the teflon wire 
	

	
	
		
		

		
			





 . Damn local postal services...
 I'll try to get a Stax female connector, or I'll have to cannibalize a friend's amp and extract the non-pro connector (he never uses it anyway) .


----------



## luvdunhill

Unfortunately I only burned 5 microcontrollers and those are taken. Once we get some feedback and I get some information up and what not, I'll let the rest go. Sorry about that. 

 They are also color-coordinated for no extra charge:


----------



## pabbi1

Just looking at those boards makes me queasy, and actually induce vertigo...


----------



## nattonrice

Very sexy Marc!
 Can't wait to get stuffing =)


----------



## Scooba

It looks very nice, Marc ! I'll wait for the microcontrollers to become available then 
	

	
	
		
		

		
		
	


	




 . Count me in, it seems an easy enough job .

 P.S. the teflon wire just arrived while I was typing this 
	

	
	
		
		

		
		
	


	




 . USPS priority + local post = 20 days 
	

	
	
		
		

		
		
	


	




 .


----------



## ktm

New tubes are in, and I'm off and running. I got a total of 6.
 Three different brands. In testing, they vary quite a bit by brand. 
 CBS(?) branded tubes tested highest, and GE the lowest.
 But they tend to be close in the same brand. I matched up 
 tubes in each channel, leaving two existing in place. One of the
 new tubes had some hum, so it came out, now it's back to dead quiet.
 It's all buttoned up. There still is some heat drift, but it follows a 
 predictable pattern, and stays reasonably in range. I'm calling this one "done"!
 I've got 4 spare, but I'd like to get 2 more tubes so I can be sure to 
 have a good set down the road. It's about time for the other stax amps to
 head out the door. Thanks everyone for your assistance. And thank
 you Al for hooking me up with the boards.


----------



## gilency

luvdunhill, what board is that?


----------



## Scooba

I've got the PS running today. 
 T1-T2 = 360mV ; T1->342V ; V+ = 300V 
 T3-T4 = 420mV ; T3 -> -342V ; V- = -298V 

 Is this ok ?


----------



## spritzer

Quote:


  Originally Posted by *gilency* /img/forum/go_quote.gif 
_luvdunhill, what board is that?_

 

It's a digital volume control based on Burr Brown chips.


----------



## pabbi1

Quote:


  Originally Posted by *ktm* /img/forum/go_quote.gif 
_New tubes are in, and I'm off and running. I got a total of 6.
 Three different brands. In testing, they vary quite a bit by brand. 
 CBS(?) branded tubes tested highest, and GE the lowest.
 But they tend to be close in the same brand. I matched up 
 tubes in each channel, leaving two existing in place. One of the
 new tubes had some hum, so it came out, now it's back to dead quiet.
 It's all buttoned up. There still is some heat drift, but it follows a 
 predictable pattern, and stays reasonably in range. I'm calling this one "done"!
 I've got 4 spare, but I'd like to get 2 more tubes so I can be sure to 
 have a good set down the road. It's about time for the other stax amps to
 head out the door. Thanks everyone for your assistance. And thank
 you Al for hooking me up with the boards._

 

So, how does it sound? 

 I have a couple of spares if you need.


----------



## ktm

It does everything the other two Stax amps don't.
 Good low end, good highs and detail without being grating.
 And that's with a sr404! The srm1 mkII didn't grate, 
 but it did noticeably roll off the high end. The sr404's and
 the srm313 were awful. Not enough low end, and the high end
 was way too much. The sr202's and the srm313 were a better match, 
 but far from perfect. I will try the sr202's with this amp again tonight.
 Overall, well with the time and money. It's my first real DIY amp.
 The Millett SS and minimax were other people's projects that had problems.
 All I had to do was find and fix them. I've got a couple of Bantams
 here I need to finish. Mouser was out of some parts for such a lot time 
 that I just shelved them. One is missing two parts, the other has just 
 the DAC soldered on. I guess it's time to finish them. Then it's off to build 
 a Nelson Pass f5 clone(I wish!).


----------



## paxeaxe23

Tomorrow I will be testing my Build! I still haven't got an answer as to why my LED's are not lighting up but everything measures up as expected otherwise so I will go ahead and try it out once I've mounted everything provisionally in its case.

 If anyone has any thoughts on the LED problem, please speak now


----------



## luvdunhill

Quote:


  Originally Posted by *paxeaxe23* /img/forum/go_quote.gif 
_I still haven't got an answer as to why my LED's are not lighting up but everything measures up as expected otherwise so I will go ahead and try it out once I've mounted everything provisionally in its case._

 

I would think the Hail Mary isn't quite the best idea.


----------



## studeb

Quote:


  Originally Posted by *paxeaxe23* /img/forum/go_quote.gif 
_ If anyone has any thoughts on the LED problem, please speak now _

 

Did you reverse the orientation when you installed them?


----------



## runeight

This is the most likely problem, but if the LEDS still don't light under normal operation then crank up the current until they do.


----------



## Scooba

Alex, my leds light up only when I am increasing the current then they fade out, or if I am ventilating the heatsinks 
	

	
	
		
		

		
		
	


	




 .

 T1-T2 = 360mV ; T1->342V ; V+ = 300V
 T3-T4 = 420mV ; T3 -> -342V ; V- = -298V 

 Is this normal ?


----------



## Beefy

Quote:


  Originally Posted by *Scooba* /img/forum/go_quote.gif 
_Alex, my leds light up only when I am increasing the current then they fade out, or if I am ventilating the heatsinks 
	

	
	
		
		

		
		
	


	




 .

 T1-T2 = 360mV ; T1->342V ; V+ = 300V
 T3-T4 = 420mV ; T3 -> -342V ; V- = -298V 

 Is this normal ?_

 

As the amp heats up, the current drops. Re-check it when hot, and you will find the current much lower than those initial readings you posted.


----------



## runeight

Quote:


  Originally Posted by *Scooba* /img/forum/go_quote.gif 
_Alex, my leds light up only when I am increasing the current then they fade out, or if I am ventilating the heatsinks 
	

	
	
		
		

		
		
	


	




 .

 T1-T2 = 360mV ; T1->342V ; V+ = 300V
 T3-T4 = 420mV ; T3 -> -342V ; V- = -298V 

 Is this normal ?_

 

So if you increase the T1/T2 and T3/T4 voltages your LEDs will not stay lit no matter what?? If this is true then there is something wrong in the PS somewhere. If the shunt transistors are conducting the LEDs must also pass the shunt current and it hardly takes any current to light them.

 If the LEDs will not light up at all (or light and then fade no matter what you d) then the primary shunt devices are not active and this means that something is not right.

 Can you verify exactly the behavior. Thanks.


----------



## Scooba

Unfortunately my local time is PST + 10 hours (I wrote post #2791 at 2:11 local time , and went straight to bed after that) .

 The LEDs faded out quite quickly after the increase of the current . 
 The values I posted were taken after ~10 minutes. 

 @Beefy: I'll let it run more time and see how it stabilizes. The PS load was the dummy one (10k on the + rail, 10k +51k on the - rail) .


 Edit: I increased the current, and the LEDs stay lit now. I have +/- 303V on the load. 
 T1-T2 = 375 mV , T3-T4 = 445 mV .


----------



## runeight

Then you're probably ok. Your particular amp may draw slightly more current than the normal. You don't need to have the LEDS super bright but just to the point where they turn bright. Your current measurements, are really not bad.


----------



## Scooba

Thanks for the info. I was wondering how bright they should be ...
 Incidentally, this is how I adjusted them: just below the point where they turn bright .


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Then you're probably ok. Your particular amp may draw slightly more current than the normal. You don't need to have the LEDS super bright but just to the point where they turn bright. Your current measurements, are really not bad._

 

That is a big difference to mine. As noted above, when fully warmed up my PSU is putting out 32/38mA, and the LEDs are still nice and bright. That is a whole 5-6mA less than scooba, or 20-25%!

 Which part differences/tolerances could result in such a big discrepancy? I must admit, I still don't fully understand how the current mirror works......


----------



## paxeaxe23

OK. I'll check and see if the LED's are in the right orientation, then if they still don't light up we will crank up the current as suggested and see what happens then. Its such a nice day here in Germany (21°C and sunny!) so I may delay tests till later,but thanks for the advice everyone.


----------



## paxeaxe23

OK, as suspected I did have the LED's in the wrong way. The Boards are now wired up provisionally in my case and I'll get a photo up tomorrow if the weather is not as nice as today!


----------



## Beefy

Good to hear!


----------



## Scooba

Today I've just got the time to disconnect the dummy load and connect the amp boards. Everything went smooth . I managed to adjust the offsets - it is ok , too. Unfortunately I did not had the time to connect the headphones (I have to improvise a female STAX connector using socket pins, until the ones from Marc will arrive) . Quite frustrating being so close: everything is ready and running fine but missing a damn connector. Anyway, tomorrow I'll be listening to it for sure, no matter what 
	

	
	
		
		

		
		
	


	




 .

 Edit:
 I've managed to listen to it today.
 With the amp heated, I have: T1-T2 = 368mV, T3-T4 = 432mV .

 For the moment all I can say is that it is very promising. I've used an Edirol UA1-EX as source, and a pair of SR-303 for the preliminary test. I won't say anything about the sound yet, except that I think that it has great potential. 
 I'll post impressions after I'll take it home, and test it with EmmLabs DCC2 and SR-404 Limited.


----------



## audionut

Anyone know of another source for the P-Channel PS mosfets 512-FQP3P50? Mouser is out of them until sometime in June. Digikey no go, too. Thanks for any info. 
	

	
	
		
		

		
		
	


	




 Tommy


----------



## pabbi1

N/m - no stock at Arrow either


----------



## ericj

Looks like Farnell UK may be the only distributor with stock. 

 Newark will get you some from there, for just $20.


----------



## Scooba

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Anyone know of another source for the P-Channel PS mosfets 512-FQP3P50? Mouser is out of them until sometime in June. Digikey no go, too. Thanks for any info. 
	

	
	
		
		

		
			





 Tommy_

 

I have used MTP2P50EG as a replacement - Mouser part 863-MTP2P50EG . It works perfectly, and has the same pin assignment. 
 Or you can try here P-Channel Power MOSFET 3P50 500V 2.7A 85W 9.5pF (x4) - eBay (item 220437061984 end time Apr-13-10 17:43:13 PDT)


----------



## audionut

Quote:


  Originally Posted by *Scooba* /img/forum/go_quote.gif 
_I have used MTP2P50EG as a replacement - Mouser part 863-MTP2P50EG . It works perfectly, and has the same pin assignment. 
 Or you can try here P-Channel Power MOSFET 3P50 500V 2.7A 85W 9.5pF (x4) - eBay (item 220437061984 end time Apr-13-10 17:43:13 PDT)_

 


 Thanks, Scooba. Those should work, like you said, as they have similar specs. Don't need 1 for my eXSTata, which is running fine, but I need one for that "other amp". It uses the same one in the - rail.


----------



## Scooba

You're welcome, audionut 
	

	
	
		
		

		
		
	


	




 .

 As for the eXStatA, I've managed to make a quick listening session last evening at home, and I was not very impressed. But I think that my 404LE's need some burn-in (they have under 40 hours) . I don't know how much they will change in sound, but I hope they will 
	

	
	
		
		

		
		
	


	




 . For now, the sound is very fast and dynamic, but it lacks staging and depth .


----------



## TimJo

At bit off topic, but...

  Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_I've gotten a few questions about the volume board that Beefy used in his build. I'm considering making a few more boards, but would like a few beta builders who are comfortable with SMD and willing to actually build the board in a reasonable time frame and offer feedback. I won't be able to build this version any time soon and there are are a few changes this go around that need to be tested. I'd be willing to provide a preprogrammed microcontroller, two PGA chips, and the board itself. If anyone would like to help, please PM me. Thanks!_

 

I got my board and chips yesterday. Thanks Marc! 

 So now I just need a bom and a schematic, and I'll get started. Are those coming from you Marc, or is this BoilermakerFan?


----------



## audionut

Quote:


  Originally Posted by *Scooba* /img/forum/go_quote.gif 
_You're welcome, audionut 
	

	
	
		
		

		
		
	


	




 .

 As for the eXStatA, I've managed to make a quick listening session last evening at home, and I was not very impressed. But I think that my 404LE's need some burn-in (they have under 40 hours) . I don't know how much they will change in sound, but I hope they will 
	

	
	
		
		

		
		
	


	




 . For now, the sound is very fast and dynamic, but it lacks staging and depth ._

 

Scooba, is this your first set of stats? Just curious, as my 404LE's have about the same amount of hours, and sound fantastic. Not sure how much stats need to burn in, compared to dynamics, but I do feel the amp needs a bit of time to settle in. Is yours the hybrid or SS?


----------



## BoilermakerFan

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_At bit off topic, but...



 I got my board and chips yesterday. Thanks Marc! 

 So now I just need a bom and a schematic, and I'll get started. Are those coming from you Marc, or is this BoilermakerFan?_

 

Hopefully my board and chips show up today. 

 I have a partial BOM. I need to sort it out and make sure it's complete.

 EDIT: My board and chip showed up.


----------



## Scooba

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Scooba, is this your first set of stats? Just curious, as my 404LE's have about the same amount of hours, and sound fantastic. Not sure how much stats need to burn in, compared to dynamics, but I do feel the amp needs a bit of time to settle in. Is yours the hybrid or SS?_

 

I had for a while a SR404 + SRM-006T II combo, sold it some time ago and bought the SR404 Limited . I also have a SR303 + SRM313 combo, borrowed from a friend, for testing purposes .
 I'll try to explain what seems odd to me: if I compare the sound of individual instruments, the eXStatA + SR-404LE is by far the most detailed, dynamic and fast combo I've ever heard. But the spatial positioning of the instruments and singers is very weird (the guitars from "Krushevo" record form MA seem clearly positioned behind me) , and not very clearly delimitated .
 I'll make more tests, and I've already identified a potential issue: I've forgot to connect the ground from the power-line in to the star ground point .

 To be continued 
	

	
	
		
		

		
		
	


	




 !


----------



## manaox2

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Hopefully my board and chips show up today. 

 I have a partial BOM. I need to sort it out and make sure it's complete._

 

I updated an old project list, but since then there are some revisions with this new board I believe, i will wait for luvdunhill to reply. One item is also back ordered and haven't found a suitable replacement for sure yet.

http://www.mouser.com/ProjectManager...sID=2782BA7937

 EDIT: I also received my own board and chips! Thanks for the lightspeed shipping!


----------



## Scooba

Quote:


  Originally Posted by *audionut* /img/forum/go_quote.gif 
_Is yours the hybrid or SS?_

 

I missed this question, sorry . My amp is the SS version.

 I can say that the ground solved the staging/delimitation problem 
	

	
	
		
		

		
		
	


	




 . 
 Beside that, it seems that I have used a higher value for the BIAS. I lowered it, and lost the bright top end. I definitely need a meter with higher impedance 
	

	
	
		
		

		
		
	


	




 .

 At this point the sound is excellent: fast, detailed, dynamic, yet rich and smooth. The timbres and textures of the instruments are very well presented. This is the first combo I heard that has this kind of performance. 
	

	
	
		
		

		
		
	


	




 Thanks to Alex for the design and support, and to Scott for the boards 
	

	
	
		
		

		
		
	


	




 .


----------



## pabbi1

Ok, I get 29 working builds.

 Larry, did Bill get you sorted?

 Beefy, any further enlightenment or mystery?


----------



## Beefy

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Beefy, any further enlightenment or mystery?_

 

Power supply still buzzes for a few seconds on startup, but works perfectly after that. One driver my Lambdas still does funny things occasionally, but I have a set of NOS drivers incoming to fix this.

 On the balance of things, it could have been easier...... a perfect storm of silly little intermittent issues is never fun. But I'm still very happy with the results


----------



## HeadphoneAddict

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Ok, I get 29 working builds.

 Larry, did Bill get you sorted?

 Beefy, any further enlightenment or mystery?_

 

Not yet. Bill has been very busy lately.


----------



## sachu

Any builds here without a maxxed power supply?, i.e one with resistors instead of the CRDs in it?


----------



## ericj

Yeah, one of my power supplies lacks CRDs.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Any builds here without a maxxed power supply?, i.e one with resistors instead of the CRDs in it?_

 

 Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_Yeah, one of my power supplies lacks CRDs._

 

Do you think maybe he wanted to also know more about how you liked it vs maxed, even if he didn't come right out and ask? 
	

	
	
		
		

		
		
	


	



 At least I am curious.


----------



## Sathimas

Guys ... I'm damn excited ...

 Just begun testing my exstata - power supply runs !!

 Next step is bias setting, then I'll test the amplifiers.

 Just writing here to calm down and lower my pulse 

 The only bad thing is that even when everything works and the amp comes alive properly I won't be able to enjoy the sound.
 I visited a much too loud concert yesterday evening and my ears are still a little numb and the left one gives me a constant *peeeeeeeeeep*.
 It already got better and will disappear completely I think but it really gets to me at the moment ...


----------



## cosmopragma

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_I visited a much too loud concert yesterday evening and my ears are still a little numb and the left one gives me a constant *peeeeeeeeeep*.
 It already got better and will disappear completely I think but it really gets to me at the moment ..._

 

No, this will never disappear completely.
 Symptoms a day later means permanent damage, that's for sure.
 Let's hope the end result will not be a permanent tinnitus but only a minor hearing loss.
 In any case, investing in high end gear and attending loud shows like the average knowledgeless bum without being protected by hearing protection (e.g. Etymotics ER-20 or similar) doesn't mix well.
 Be careful .......


----------



## Keithpgdrb

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_Guys ... I'm damn excited ...

 Just begun testing my exstata - power supply runs !!

 Next step is bias setting, then I'll test the amplifiers.

 Just writing here to calm down and lower my pulse 

 The only bad thing is that even when everything works and the amp comes alive properly I won't be able to enjoy the sound.
 I visited a much too loud concert yesterday evening and my ears are still a little numb and the left one gives me a constant *peeeeeeeeeep*.
 It already got better and will disappear completely I think but it really gets to me at the moment ..._

 

I remember thinking that it would go away. that was a long time ago. Invest in some good ear protection now, and always have those foam earplugs stuffed in every pocket of every jacket. availability is the key. I've even resorted to stuffing TP in my ears at a show. was worth it. Anyway, back to the ExStatA!!!


----------



## Sathimas

Well ... a good hearing protection is something I wanted to buy since the beginning of that year and will definitely buy this week.

 About disappearing or not:
 I am studying medicine and have just made an internship at a doctor who treats tinitus/hearing loss and so on.
 The chances for those things to disappear are'nt that low at all.

 I already had that once very bad - hearing loss (heights) and tinitus on both ears for 3 or 4 days after my first big concert at all (AC/DC).
 Disappeared afterwards.
 I also experienced something like this when working in very loud places but it always went away.

 The last years I always use hearing protection in loud places, even if it is only for seconds.
 But yesterday I just had nothing there...

 Just be optimistic with me!

 For the exstata:

 It just burned one of the two fuses as I switched him off, seems that they are to "small".
 All the rest seems to work good.


----------



## Beefy

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_Well ... a good hearing protection is something I wanted to buy since the beginning of that year and will definitely buy this week._

 

_Every_ music lover should have a set of these.


----------



## Sathimas

Ok - problems:

 I can not get the offset stable on one channel, the other one seems to work just fine.

 When I remember correctly that problem can occur if the jfets are not "good" enough and my quad was like 9.86, 10.14, 10.5, 10.8 ...

 Could that be my problem?


----------



## les_garten

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Every music lover should have a set of these._

 

Thanx for that link!

 Motorcycles and open pipe Porsche's have had a few go rounds with my Hair Cells, so I try to be a little more responsible now.


----------



## Sathimas

Some measurements:

*Power supply:*

 - T1-T2: 360mV
 - T3-T4: 410mV
 - Rails are 317 and 312V
 - T1/T3 against ground are ~330V

 Transformer output voltage is 252V, I am using a 300V zener string.

*Amp Boards:*

 Left channel:
 - Across out +/ out - drifts very little arround 50 to 60mV
 - out - to ground: drifts around ~500mV, down to 100mV and up to 700mV
 - out + to ground: arround 180mV, relatively stable

 right channel:
 - across out + / out - drifts arround 10mV
 - out - to ground and out + to ground is the strange thing:
 I can only get one output close to 0VDC, the other one (either plus or minus) is arround 20V then
 But its not possible to get those values stable

 I also checked the power consumption of the whole amp - initial is about 50watts,
 after about 5 minutes it stabilizes at about 46watts. (I just remember asking someone about that some pages ago...)


----------



## runeight

The amp will naturally drift. Even 1 or 2V is ok although most of the amps do much better than this. Hundreds of mV drift is actually very good for an amp than has no control circuitry for this. So no sweat on this item.

 However, are you also not able to adjust either the offset or balance to 0 on one of the channels? If this is so then it probably is a jfet matching issue.


----------



## Sathimas

Just to clarify:

*right channel:*
 - across out + / out - drifts arround 10mV (*absolutely ok then*)

 - out - to ground and out + to ground is *the strange thing*:
 I can only get one output close to 0VDC, the other one (either plus or minus) is arround 20V then
 But its not possible to get those values stable

 So if attach the probes to out+ and ground and adjust the voltage close to 0VDC and then attach the probes to out- and ground the reading will be at least 20V.
 When I then adjust out- to ground close to 0VDC out+ will rise up again.

 It is the board with the one jfet that only had a 9,86mA reading ...

 (The other board shows no problems, offset and balance are ok.)



 I just knew it, my DIY-career seems star-crossed 

 But those glowing tubes are worth it, really really worth it.
 I also built a SOHA I and a SOHA II yet (which worked immediately!) and liked them very much but the exstata is my first amp with
 tubes that do not have to lighted with LEDs to shine ^^

 Thanks for giving this amp to the community and your great support !


----------



## Beefy

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_Just to clarify:

*right channel:*
 - across out + / out - drifts arround 10mV (*absolutely ok then*)_

 

...... only drifting 10mV? I find that very hard to believe. Are you sure that you are measuring correctly?


----------



## Sathimas

it is drifting around the center of 10mV - not +/- 10mV

 But my DMM isn't the best anyway - when I have new jfets I will ask a friend to bring a professional one from his work.


----------



## paxeaxe23

FINALLY!

 Its all done. I'm sitting here listening to Simon and Garfunkel, E.L.P., Chicago Symphony with Reiner (R. Strauss) as well as some home recorded Horn quartets and a few recordings of my Orchestra to hear myself. Moody Blues, and Michael Buble. just to name a few. No doubt I'll be sitting here in a week still listening.

 This is really an excellent Amplifier, very transparent, very clear High's and a surprisingly tight and definable bass line too. The mids are also very balanced and acoustics of the recordings come through as if I were there myself.

 I am listening on my SR5's and will now probably have to go out and get a pair of 404's so this isn't really a budget build 

 Thanks to everyone who helped me through this my first BIG (and definitely NOT my last either, I'm hooked!) project, I'll post a more thoughtful piece on the first impressions thread once I have made a final judgement, but wanted to let you all know I got there and say thanks to you all, but especially to Alex. This design is a great contribution Alex, thank you from the bottom of my heart.

 Francis


----------



## pabbi1

I made a 1970's run over the weekend through E.L.P., Golden Earring, 10 Years After, Alice Cooper, Uriah Heep, Joe Cocker, and a couple of compilations - this amp really shows what we missed all those years on the radio, and the quality and care of the recording industry at the time. 

 It continually amazes me the number of things I can now listen to and really LIKE, that had been completely run over with terrestrial radio - like 'Freebird', 'Highway Star', 'Stairway', and all number of obscurities. It really is fun to run through a compilation, especially full of junk I'd never put on as a seperate selection, and see what pops out.

 The genius of this amp is that it makes stats FUN, in addition to being fast, detailed, precise and balanced. That is a very unusual convergence.


----------



## BoilermakerFan

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_I made a 1970's run over the weekend through E.L.P., Golden Earring, 10 Years After, Alice Cooper, Uriah Heep, Joe Cocker, and a couple of compilations - this amp really shows what we missed all those years on the radio, and the quality and care of the recording industry at the time. 

 It continually amazes me the number of things I can now listen to and really LIKE, that had been completely run over with terrestrial radio - like 'Freebird', 'Highway Star', 'Stairway', and all number of obscurities. It really is fun to run through a compilation, especially full of junk I'd never put on as a seperate selection, and see what pops out.

 The genius of this amp is that it makes stats FUN, in addition to being fast, detailed, precise and balanced. That is a very unusual convergence._

 

And you're not even listening to it properly, which is of course, on vinyl as that was the preferred medium in the '70s. Just imagine how good it would sound on vinyl via a Grado Gold or Denon DL103 cartridge on a modded RB250 tone arm in a modded Planar 3 TT through an AudioSector, TubeCAD Tetra, or Pass DIY Pearl2 phono stage. 
	

	
	
		
		

		
			





 EDIT: I'll let you know after I get all three of those phono stages built, then purchase and mod the TT. 
	

	
	
		
		

		
		
	


	




 Figure I need to test a great Op-Amp, tube, and discrete SS phono stage, so I'll have to build all three.


----------



## pabbi1

Yeah, probably... 
	

	
	
		
		

		
			





 BTW, anyone have an extra matched quad of fets? Might need them to help another build come online.


----------



## sachu

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Yeah, probably... 
	

	
	
		
		

		
		
	


	




 BTW, anyone have an extra matched quad of fets? Might need them to help another build come online._

 

I know i had atleast a couple of quads of the J271 but gf "cleaned" up the desk..so will have to match again. How soon do you need it?


----------



## pabbi1

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_I know i had atleast a couple of quads of the J271 but gf "cleaned" up the desk..so will have to match again. How soon do you need it?_

 

Couple of weeks out. Thank goodness my office is a 'no clean' zone. Once a year is plenty...


----------



## luvdunhill

I'm back.. I'll get this sorted later this week and open a thread and what not for the attenuator.


----------



## Sathimas

I just wired my LEDs and to my surprise they did not light up ...

 I have unfortunately used two different kinds of LED, 2 superbright and 10 standard LEDs.
 (I wanted it the other way round but messed up the two bags with the LEDs...
 But even the superbright LEDs are not bright enough.)
 The standard LEDs need 10mA to light, so the power supply does'nt give enough current.

 Could I increase simply that current with a parallel resistor? (parallel to the 75kOhms)
 I don't want to remove the power supply again from the case.

 Would that work with a standard resistor or would that also have to be a 5W resistor?


----------



## runeight

Most LEDs will light at the 4-5mA passed through this circuit. Not as bright as at 10mA but still pretty bright.


----------



## Sathimas

Well mine don't ...

 All LEDs are connected in series - the first and the last one are the superbright ones - which light up, all the others don't.

 I just checked the data and the normal LEDs I am using here only have a brightness of 3mcd @ 10mA.
 The superbright ones are made for 20mA operation and are really much brighter, think they are above 100mcd.

 So I'll have to rise the current or replace all the LEDs.
 Since installing and wiring took me about 2 and a half hour I'd like to try rising the current first


----------



## Beefy

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_So I'll have to rise the current or replace all the LEDs.
 Since installing and wiring took me about 2 and a half hour I'd like to try rising the current first _

 

Raising the current is going to generate an _extraordinary_ amount of heat in the LED resistors.


----------



## Sathimas

Well, if my (very dusty) physics knowlegde is right I'd have to lower the resistorvalue down to arround 30KOhms to get approx 10mA.

 If thats not possible I'll have to do all the LED wiring again


----------



## Beefy

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_Well, if my (very dusty) physics knowlegde is right I'd have to lower the resistorvalue down to arround 30KOhms to get approx 10mA._

 

That will be a massive 3 watts dissipated by each resistor. Sure, a 5W resistor could possibly handle that heat...... but can the PCB underneath it?

 When I was running the original 1.2W through the suggested 75kohm resistors, my PCB was hitting 120C. Not good.


----------



## runeight

Sathimas, sorry about this, but in addition pulling 10mA from the PS at the filter caps will drop the voltage at the input to the regulator. I don't know how much offhand but you'll have to watch for thiss too.

 I am surprised that your leds don't light at all at 4-5mA. Really surprised unless you are using super high current leds.


----------



## Sathimas

I just checked the temperature (by finger) and the PCB is already quiet hot - so I'll just leave things as they are.
 Thanks for your advice!

 Those LEDs are just really cheap ones, I had to search a while to find the datasheet.

 Something else - much more joyful: I just gave the offset/balance adjustment another try and this time it seems to work.
 Maybe I just forgot to recheck the offset yesterday - i don't know...

 Both channels are below 1V now since about one hour, I'll wait another one to be sure...


----------



## Sathimas

Short notice 
	

	
	
		
		

		
		
	


	




 It's alive !!!!!

 From this point one there will be only down and sidegrades in headphones :-D

 Thanks again everyone here, especially Alex!

 (I just somehow managed to bypass my pot with my loop-in/out circuit, I really have to rethink that wiring ^^)


----------



## swt61

Quote:


  Originally Posted by *BoilermakerFan* /img/forum/go_quote.gif 
_Just imagine how good it would sound on vinyl via a Grado Gold or Denon DL103 cartridge on a modded RB250 tone arm in a modded Planar 3 TT through an AudioSector, TubeCAD Tetra, or Pass DIY Pearl2 phono stage. 
	

	
	
		
		

		
		
	


	


_

 

Or a 'Colossus' TT w/highly modded RB-300, Zu DL103 and Pass DIY Pearl.


----------



## M3NTAL

Darn you analog guys! All I have is digital and a very small selection of cassettes that are from my pre-teens that are mostly garbage! Praise high end DAC's


----------



## pabbi1

Those who forget the past are doomed to repeat it. It makes me all warm, and fuzzy like... until I drop that needle, and it hits that cat hair... or dust clot... or POP from that scratch right where some sweet high note is.

 When I get that temptation, I put on one of the CDs I had created from a favorite album and remember all that other great stuff about vinyl.

 So, we have one more member... with several big guns out - Nate, Marc, Brian, Frank (coming, I know)... and a few others. Updates?

 Need more impressions, good, bad and ugly - causing anyone to buy different phones or sources?

 Finally starting to see a few more WTB for eXStatA in the FS forums as well. just remember, we are part of a fairly exclusive club.


----------



## sachu

I still have one SS eXStatA build here that is needing a new PSU, have half the new board populated but need to put in a small order before i can complete it..


----------



## Sathimas

I spent the evening listening to two of my favourite CDs and the sound is just amazing.

 I can not compare the exstata to any other stax-amp because I have none and never owned one.

 First CD to listen with new gear is always: Metallica - S&M
 I know that CD since it came out and must have listened to it many hundred times with real concentration.
 I did not expect it but again I hear new details, the overall sound is just perfect with my Lambda Pro (Also have a new 303 here for testing).

 I think for the time beeing and much further on I am at the end of my way concerning headphones and headphoneamps.

 Thanks you very much everybody here.
 ______________________

 There's still a problem that troubles me very much - the volume pot has no effect!
 (I just managed to listen yesterday because my cd player has variable outputs)

 It is clearly in the signalway - I get a reading of 10,4KOhms between the jack and the input minus post, changing to near 0 Ohms when turned fully clockwise.
 I have a 10K RK27 2gang, wiring is unbalanced then of cause.

 Any ideas?


----------



## paxeaxe23

I've just uploaded a few pictures of my Build. YOu can see more in my Albumn but here are two.


----------



## runeight

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_I spent the evening listening to two of my favourite CDs and the sound is just amazing.

 I can not compare the exstata to any other stax-amp because I have none and never owned one.

 First CD to listen with new gear is always: Metallica - S&M
 I know that CD since it came out and must have listened to it many hundred times with real concentration.
 I did not expect it but again I hear new details, the overall sound is just perfect with my Lambda Pro (Also have a new 303 here for testing).

 I think for the time beeing and much further on I am at the end of my way concerning headphones and headphoneamps.

 Thanks you very much everybody here.
 ______________________

 There's still a problem that troubles me very much - the volume pot has no effect!
 (I just managed to listen yesterday because my cd player has variable outputs)

 It is clearly in the signalway - I get a reading of 10,4KOhms between the jack and the input minus post, changing to near 0 Ohms when turned fully clockwise.
 I have a 10K RK27 2gang, wiring is unbalanced then of cause.

 Any ideas?_

 

We can be pretty sure that the pot is wired wrong. Post some pics and the other guys on this thread will be able to help you.


----------



## pabbi1

Well, I am the last person on earth to comment about wiring pots... but, IMHO, the overall quality of builds on this design rank top of any DIY design. Good work guys - you should all be proud, and I am embarrassed enough to recase mine.


----------



## BoilermakerFan

Quote:


  Originally Posted by *swt61* /img/forum/go_quote.gif 
_Or a 'Colossus' TT w/highly modded RB-300, Zu DL103 and Pass DIY Pearl. 
	

	
	
		
		

		
		
	


	


_

 

I was trying to keep Al on a budget. 
	

	
	
		
		

		
		
	


	




 My custom TT will be based on a broadcasting TT with the Pabst hysteresis motor, mounted separately, belt driving the milled and balanced platter in a custom plinth sitting in thrust bearings so it can't drift or float. The RB-250 is actually a better tone arm once modded, and prices out around the same or less than a new RB-301. The Zu DL103 is supposed to awesome and it will be my next high end cartridge once everything else is finished, but initially, I'll just keep my Grado Gold. As much as I dislike the cans, I love the sound sig of the Grado cartridges. 

  Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Those who forget the past are doomed to repeat it. It makes me all warm, and fuzzy like... until I drop that needle, and it hits that cat hair... or dust clot... or POP from that scratch right where some sweet high note is.

 When I get that temptation, I put on one of the CDs I had created from a favorite album and remember all that other great stuff about vinyl.

 So, we have one more member... with several big guns out - Nate, Marc, Brian, Frank (coming, I know)... and a few others. Updates?

 Need more impressions, good, bad and ugly - causing anyone to buy different phones or sources?

 Finally starting to see a few more WTB for eXStatA in the FS forums as well. just remember, we are part of a fairly exclusive club. _

 

Al, I play almost all used vinyl. I've had a few dogs, but usually they are just dirty as hell. A good cleaning, then Gruv Glide before spinning them and all is great. No pops unless it's a damaged record or one of my parents old Beatles or Beach Boys albums that are just worn out. Yeah, it's a lot of work if you buy 10-30 used albums at a pop, but for one, two, or three used records, it's an enjoyable part of the process to me. Kind of like panning for gold or cracking open geodes, but with much better odds of finding gems. 

 I have 3 eXStatas in the works. Two commissioned, one is mine. Work has ramped up to insane levels which is just awesome for my company and the economy, but doesn't leave me with much free time. I've been logging my usually 8-10 hours for work during "regular" hours for the boring hydraulics stuff, then doing more enjoyable, full custom stuff for my company at night during the week too. Should have things squared away soon and one NABU is on it's way back from Steve with an awesome front panel for one of the commissioned builds.


----------



## Scooba

Quote:


 I get a reading of 10,4KOhms between the jack and the input minus post, changing to near 0 Ohms when turned fully clockwise. 
 

That would suggest that the end of the potentiometer or the cursor is connected to the ground. Can you post a picture of the potentiometer (including wires) ?


----------



## Sathimas

Posting a picture is possible - but you'd see nothing since that place is very stuffed.

 Indeed if I have the pot fully clockwise and measure directly between In ground and In minus theres 0 Ohms.

 I'll just recheck my wiring, I just can not imagine where that connection to ground cames from.

 I wired the pot after that picture:
How to Wire Panel Components

 The ground pins of the pot are not connected at all.


----------



## Beefy

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_The ground pins of the pot are not connected at all._

 

You MUST connect the ground on the pot to the signal ground.


----------



## padam

I couldn't spend enough time with mine yet (current version of the hybrid) since it still needs casework and stuff but this amp sounds Very promising so far.
 I only had a fully restored vintage SRA-3S to compare it with which I think is as good as the SRM-T1 (if not better) and this outperforms it by quite a margin, especially in the low end.

 Once my system is fully ready (now this could take a while...) I will be able to do a full shoot-out against the SRM-717 so hopefully some objective comparisons can be made but for now I would that it definitely sounds very nice.


----------



## spritzer

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_You MUST connect the ground on the pot to the signal ground._

 

Yeah, this is a voltage divider and it won't work without ground. 

  Quote:


  Originally Posted by *padam* /img/forum/go_quote.gif 
_I only had a fully restored vintage SRA-3S to compare it with which I think is as good as the SRM-T1 (if not better) and this outperforms it by quite a margin, especially in the low end._

 

I rebuilt a SRA-3S and it had far less control then a T1 (recapped as well) which causes the bass to be over blown but far from accurate. I do quite like the SRA-3S with the older cans but it isn't ideal for anything past the SR-5 IMO. 

 Ohh and since this is the Exstata thread, my P2P version is 95% done, just missing the input transistors since I don't want to risk any of my dual's. Some small changes to the components used but nothing major and I didn't use the KSC5042 since they are on their last legs (as in Fairchild will stop production soon) and the Sanyo parts are a better. Not sure what PSU I'll use but I've been thinking about doing a version of the T2DIY PSU since it is already all P2P. +/-350V is given since I have some spare 280V/140ma transformers.


----------



## gilency

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Well, I am the last person on earth to comment about wiring pots... but, IMHO, the overall quality of builds on this design rank top of any DIY design. Good work guys - you should all be proud, and I am embarrassed enough to recase mine._

 

Pabbi:
 I am getting brave enough and thinking about re casing mine (your SS Proto build). Any ideas on a suitable metal case? Dimensions would be appreciated!


----------



## pabbi1

Paxeaxe23 has a really nice case above, but looks like the Italian case (Galaxy)? Since I do all 'custom' cases, other than the infamous NABU, I'd be at a loss to recommend something. I am sure others have input as to what some of the Hammond or one of the ParMetals 20 series (Par-Metal), though their rep has taken a hit over the years for spotty delivery, quality and customer service.

 It looks like Chassis Boxes, Enclosures, Project Boxes. Aluminum Boxes and Plastic Boxes would be really close to you.


----------



## paxeaxe23

Yes its the Galaxy case, I live in Germany so it was easy to order from Italy. I got it here modu

  Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Paxeaxe23 has a really nice case above, but looks like the Italian case (Galaxy)? Since I do all 'custom' cases, other than the infamous NABU, I'd be at a loss to recommend something. I am sure others have input as to what some of the Hammond or one of the ParMetals 20 series (Par-Metal), though their rep has taken a hit over the years for spotty delivery, quality and customer service.

 It looks like Chassis Boxes, Enclosures, Project Boxes. Aluminum Boxes and Plastic Boxes would be really close to you._


----------



## gilency

Quote:


  Originally Posted by *paxeaxe23* /img/forum/go_quote.gif 
_Yes its the Galaxy case, I live in Germany so it was easy to order from Italy. I got it here modu_

 

which size did you get?


----------



## Sathimas

I think it's the same size as mine, 330x280mm (80mm height)

 Those cases are really high quality, the only problem is that they all look the same as long as you don't put some more effort in making them look unique.

 Is there still some exstata builder in this thread without headphone?

 I have a only 5 year old like new SR303 here for sale


----------



## Beefy

Well, these came in the mail yesterday - minty fresh NOS SR-Lambda normal bias drivers - and I installed them today.......






 All of the problems with my Lambdas are now gone, and I can finally enjoy my Exstata to the best of its abilities. Suffice to say, it sounds really freaking good 
	

	
	
		
		

		
		
	


	




 The bias is still set at the low 140V that I was using for the previous dodgy driver, so I will look to increasing it tomorrow up to the proper value and see what happens.


----------



## les_garten

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Well, these came in the mail yesterday - minty fresh NOS SR-Lambda normal bias drivers - and I installed them today.......






 All of the problems with my Lambdas are now gone, and I can finally enjoy my Exstata to the best of its abilities. Suffice to say, it sounds really freaking good 
	

	
	
		
		

		
		
	


	




 The bias is still set at the low 140V that I was using for the previous dodgy driver, so I will look to increasing it tomorrow up to the proper value and see what happens._

 

Clean as a Hound's Tooth!


----------



## paxeaxe23

Yes thats the one I bought. I realy don't mind it looking the same as other ones as my skills at metal and woodwork are really non-existant. I do actually have a nice 10mm Black front panel that I wlll have someone drill for me when I have time to draw a nice layout which will help, although I was really hoping to kee it for my Hybrid build and am keeping my fingers crossed that I can get started on that one sometime in the next months if Alex does some more boards or anyone has a spare set of Hybrid boards of course (Happy Easter alex 
	

	
	
		
		

		
		
	


	




) 

 Francis

  Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_I think it's the same size as mine, 330x280mm (80mm height)

 Those cases are really high quality, the only problem is that they all look the same as long as you don't put some more effort in making them look unique.

 Is there still some exstata builder in this thread without headphone?

 I have a only 5 year old like new SR303 here for sale 
	

	
	
		
		

		
		
	


	


_


----------



## runeight

Quote:


  Originally Posted by *paxeaxe23* /img/forum/go_quote.gif 
_(Happy Easter alex 
	

	
	
		
		

		
		
	


	




) 

 Francis_

 

Thanks. I was actually on an airplane on Easter coming home, but I still had a happy day.


----------



## mideel

I have most of the parts in the mail for an eXStata solid state build, but I need some help in selecting the last 2 parts of my build: Transformer and stax jack.
 The Triad Magnetics VPS230-110 as specified in the BOM for the SS build is 2x115VAC (25VA), but in the triad wiring page is described 240-0-240 
	

	
	
		
		

		
		
	


	



 So can I replace the Triad for a "50 VA 115 VAC (2x), AA-53129"? This transformer is being SOLD as 2x115VAC, but in the datasheet its specified as
 "U=110V , Uo = 133,1V (25VA)" for one secondary. Calculating 220V*sqr(2) gives 311V so is the 11V enough headroom for voltage fluctuations etc.?

 And what type of jack is the stax jack? I know there is one at alliedelec (Cooper Interconnect 78-S6S), but where can I find a vendor that sells those in europe? Or will I just have to scrap a bunch of molex connectors and just make one myself


----------



## Sathimas

rs components sells them (the stax- jack) in Germany, part number 2508709806

 Unfortunately you need to order as a company, but a friend that gives you adress and tax-number of his company should be easy to find.

 For the transformer you could also have a look a custom transformers, top-print makes really nice ones.


----------



## Beefy

Quote:


  Originally Posted by *mideel* /img/forum/go_quote.gif 
_The Triad Magnetics VPS230-110 as specified in the BOM for the SS build is 2x115VAC (25VA), but in the triad wiring page is described 240-0-240 
	

	
	
		
		

		
		
	


	


_

 

I think you are confused. Are you looking at the specs of the primary or the secondary when you see 2x115VAC?

 [EDIT] Perhaps that isn't it. Do you realise you actually need two of the Triads?

  Quote:


 So can I replace the Triad for a "50 VA 115 VAC (2x), AA-53129"? This transformer is being SOLD as 2x115VAC, but in the datasheet its specified as
 "U=110V , Uo = 133,1V (25VA)" for one secondary. Calculating 220V*sqr(2) gives 311V so is the 11V enough headroom for voltage fluctuations etc.? 
 

Again, is the 2x115VAC for the primary or secondary? I don't think that will be sufficient.


----------



## runeight

Quote:


  Originally Posted by *mideel* /img/forum/go_quote.gif 
_I have most of the parts in the mail for an eXStata solid state build, but I need some help in selecting the last 2 parts of my build: Transformer and stax jack.
 The Triad Magnetics VPS230-110 as specified in the BOM for the SS build is 2x115VAC (25VA), but in the triad wiring page is described 240-0-240 
	

	
	
		
		

		
		
	


	



 So can I replace the Triad for a "50 VA 115 VAC (2x), AA-53129"? This transformer is being SOLD as 2x115VAC, but in the datasheet its specified as
 "U=110V , Uo = 133,1V (25VA)" for one secondary. Calculating 220V*sqr(2) gives 311V so is the 11V enough headroom for voltage fluctuations etc.?

 And what type of jack is the stax jack? I know there is one at alliedelec (Cooper Interconnect 78-S6S), but where can I find a vendor that sells those in europe? Or will I just have to scrap a bunch of molex connectors and just make one myself 
	

	
	
		
		

		
		
	


	


_

 

mideel, the transformer you want to use will not work. As beefy says, if you use the triad you need two of them. The transformer specs vary a bit depending on manuf. Some of them specify 115V (230V) for the primary and some specify 117V (234V) for the primary. Similarly for the secondary.

 The important feature of the triad is that it is a 1:1 or a 1:2 ratio of voltages depending on its wiring.

 In the 1:2 case whatever the mains voltage is will be doubled at the secondary. So if the actual mains is, say, 121V the secondary will be 242V.

 For the 1:1 case (Europa) if the primary is 237V the secondary will be 237V.

 Using 240V as the secondary spec is a convenient number which is pretty accurate where I live because the mains is 120V and so the secondary will be 240V.

 All this to say that I think in Deutschland you need a 1:1 ratio with a 100mA secondary. This would be 230V primary and 230V secondary however that is actually configured. EDIT: And you will need two of these.

 Does this help?


----------



## mideel

Ah, yeah I was confused, sorry about that 
	

	
	
		
		

		
		
	


	



 I was confused about the 250-0-250 since thats just away of saying 500V CT.
 Using two 110V secondaries would be 110-0-110 or 220V CT. So if I connect two 230V primary windings parallel, and four 110V secondaries in series that gives me 220-0-220 or 440V CT, but my original question still stands is that enough? given that the transformers are only rated at U=110V , Uo = 133,1V (Voltage unloaded?), or should I pay €15 more for a 250-0-250 Hammond?


----------



## runeight

No, 440VCT will not work. Sorry. If you have a SS amp the triads will work very well. Can you not get these? Or their equivalent?


----------



## BoilermakerFan

Worst case he can get the model R80-36 R-core and use the 230-0-230 taps and lower the zener strings to 282V or so, which had been discussed many pages ago.

115V/230V Hi-Fi Grade 100W R-Core Tranformer for DIYer - eBay (item 110506443693 end time Apr-12-10 08:38:37 PDT)


----------



## Postal_Blue

I would like to apologize to Alex and the proto team. When I asked for one of two sets of boards that became available I did not realize that you guys were still in proto, otherwise i would have held off. After coming to this realization I began shifting funds and selling gears to fund the build. I had come up with the money to make my final order, but unfortunately the Item i sold was fubar'd by the Currier so needless to say I will be refunding that money. 

 All this to say I have not completed the build and will not likely do so until the end of May when I am expecting some funds to surface. I am sorry for holding up progress, I would certainly like to complete the build but If Alex would prefer it I can send the boards to someone who can build it more quickly. I have partially stuffed the power supply (all but the caps and large transistors) and I have tubes, tube sockets, xformer, Luvdunhill Stax Jack, and all of the PS transistors. 

 William


----------



## Postal_Blue

and double post


----------



## pabbi1

Sorry to have been overly aggressive getting after folks to build. Take your time, as it really will be worth the effort. Enough are running to have determined any serious flaws by now.

 But, some guys (Nate, Marc) are further along and are just shy.


----------



## mideel

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_No, 440VCT will not work. Sorry. If you have a SS amp the triads will work very well. Can you not get these? Or their equivalent?_

 

It's not a matter of get its the postage, import fees and VAT hassle I'm more concerned about. 

 So 460VCT is the bare minimium (since that is what the two triads are rated for 4x 115 = 460VCT), for an SS build. So I can replace Triad VPS230-110 for a Triad VPT230-110 (same ratings but its a torroid) or another equivalent? 
 The reason I asked about the 230V (primary) 2x110V (secondary) rated transformer, was because it is being listed and sold as a 2x115V and I went over to the shop and asked about it in person and I was told it was 2x115V


----------



## runeight

Well, there is a bit of trickery involved here using the Triads.

 These transformers have really bad regulation. In your case the 1:1 ratio would normally generate 460VCT with two transformers in series. However, the 110mA rating is about twice as high as needed. This means that the partially loaded transformers will actually generate more than 460VCT in operation. And this is why they will work.

 But if your transformer, when loaded, only generates 460VCT then it will not work and you'll have find one that legimiately makes 500VCT.

 Part of the original goal with this amp was no special transformers and so this little trick was used so that cheap triads could power the sand amp.

 You can run a simple test. Wire up one of the transformers and measure the secondary voltage without any load. If it is way higher than 230VAC you're probably ok.


----------



## mideel

Thank you for the clarification, that made alot more sense. The VPS230-110 regulation is: "25% TYP @ full load to no load", so typically it will generate 125%*230V~288V with no load and since the eXStata is only drawing ~50% of the rated current you get alot more than the rated 230V. 
 I think it would be good to state this on the eXStata site or in the BOM, so that people in the future won't go "Oh, the triad is out of stock, but its rated 230V so I can replace it with another 230V transformer" (like I did 
	

	
	
		
		

		
		
	


	




).


----------



## runeight

Good idea. I'll try to do that soon.

 I hope that you've got enough accurate information now to find a transformer. It only took about 5 or 6 questions to get here.


----------



## mideel

I placed an order for two triads (hard to beat the price) other parts are already on the way so I will be starting the build in a few days (customs willing 
	

	
	
		
		

		
		
	


	




).


----------



## bidoux

I finally did a Mouser order with the help of Beefy's project and Runeight's BOM, both were really hlepful. Now I'm waiting for it, anyone have a clue how long it will take to arrive in France (using Fedex) ?

 I know I have been quite long to get starting, at the time I thought I'd helped completing the order but now lots of people want to build an ExStata, so I apologize for this.


----------



## Sathimas

shipping time should be under one week, they are really fast.

 Btw. I: remove that "sorry for my bad English" from your signature 
 Your English is far to good to apologize for it.

 Btw. II: Still someone here without headphone? My SR303 is still for sale


----------



## bidoux

Thanks for your answer, I hope I will be able to start it during my holydays.
 As for my signature, sometimes my speaking is correct, sometimes it gets really awfull so I guess I'll leave it.


----------



## mideel

I placed my latest order on the 7th and reading from the FedEx tracking site:
 Apr 8, 2010 20:38 - Left FedEx origin facility - MANSFIELD, TX
 Apr 9, 2010 22:42 - At local FedEx facility - PARIS FR

 So yeah, Mouser orders seem to ship really fast (although the Estimated delivery date is still Apr 16, 2010).

 I still need some 600V hookup wire for this build though, I don't feel comfortable using generic computer 300V PSU wire or CAT6, although I will be using CAT6 for my other builds, its hard to beat something you get for free 
	

	
	
		
		

		
		
	


	



 Its unbelievable how much perfectly usable CAT6 wire (meaning Ethernet or LAN cable) and old electronics get thrown into the trash bin everyday.


----------



## paxeaxe23

I sent you a PM a fews days ago now about the Headphone. Let me know if it didn't get to you 
	

	
	
		
		

		
		
	


	





  Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_Btw. II: Still someone here without headphone? My SR303 is still for sale_


----------



## bidoux

Quote:


  Originally Posted by *mideel* /img/forum/go_quote.gif 
_I placed my latest order on the 7th and reading from the FedEx tracking site:
 Apr 8, 2010 20:38 - Left FedEx origin facility - MANSFIELD, TX
 Apr 9, 2010 22:42 - At local FedEx facility - *PARIS *FR_

 

Are you a French ExStata builder ?


----------



## paxeaxe23

There seem to be quite a few Europeans here, maybe we should all club together and pay for Alex to come over and drink beer with us sometime!


----------



## runeight

I like this idea.


----------



## bidoux

So I got a mail from Mouser. It seems I will get the P channel mosfets in June 29, 2010, the MPSA42 in JUN 14, 2010 and a red Led in May.

 I could have delete the MPSA42 and LED from the order as they are available in the local shop bbut the mos aren't. I guess I will wait until this summer.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *bidoux* /img/forum/go_quote.gif 
_So I got a mail from Mouser. It seems I will get the P channel mosfets in June 29, 2010, the MPSA42 in JUN 14, 2010 and a red Led in May.

 I could have delete the MPSA42 and LED from the order as they are available in the local shop bbut the mos aren't. I guess I will wait until this summer.
	

	
	
		
		

		
			



_

 

Ask them to change the order.


----------



## runeight

And. any P and N mosfets will work if they are 400-500V in a TO220 package.

 You might find the MPSA42 from another manufacturer on Mouser.


----------



## bidoux

Thank you HeadphoneAddict and runeight for your answers.

 I am going to try to change the order of the MPSA transistors and the LED, it seems that I ordered the only kind of MPSA42 that are out of stock 
	

	
	
		
		

		
		
	


	




 I found this mosfet to replace the FQP3P50: *726-IPA50R399CP* (IPA50R399CP) (among a lot of others), it is rated at 500V and 9A and has the same pinout.

 Edit : I sent an email to Mouser, I hope they will modify my order as soon as possible.


----------



## sachu

Been trying to get this new exstata PSU board to come up right this morning. 

 So far, the negative rail seems to be working perfectly. Dials up to -292V on power up with T3-T4 at 360-365mV. LED comes on okay..the rail starts moving towards -300V quickly

 The positive rail however starts up at 292V..and moves to 296V quickly and then slows down a bit. I have T1-T2 at 370mV. 

 But the LED doesn't come on on the positive rails. I checked the LED with my meter and it lights up (albeit very dim). Anyone have any ideas as to what might be happening on the positive rails? Why isn't the LED coming on?

 Is it okay to proceed regardless? I am using the basic PSU with the resistors in lieu of the CRDs.


----------



## Beefy

Are the heatsinks for the shunt BJTs getting warm?


----------



## sachu

*facepalm* Nevermind..I had the load resistors switched. Everything checks out fine now. 

 This is why I shouldn't be working on HV stuff after having my first smoke.


----------



## Beefy

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Will test and see if my 5th build works or not in a little bit. There is still a 6th build that needs testing as well this weekend 
	

	
	
		
		

		
		
	


	


_

 

Who are you building all of these for? There were plenty of DIYers who would have loved to build one of these


----------



## sachu

Don't believe I needed to answer to that question.


----------



## gilency

Sachu, you indeed are amazing. Don't you have a real job?


----------



## sachu

Quote:


  Originally Posted by *gilency* /img/forum/go_quote.gif 
_Sachu, you indeed are amazing. Don't you have a real job? 
	

	
	
		
		

		
		
	


	


_

 

Heh...am graduating soon..so have started looking for a real job actively. Last term stuff, job hunting.. that itself is like a bloody full time job and more


----------



## gilency

Good luck to you, man. I am sure you will find it, even if it takes time.
 The economy is slowly improving and hopefully jobs will follow. My apologies. Poor choice of words.


----------



## HeadphoneAddict

In regards to Beefy's inquiry above, Sachu is helping by casing up my SS eXStatA and completing my luvdunhill attenuator that had missing parts. At first he refused to consider this if it would jeopardize his standing at head-fi, and he wanted to consult with Jude about what he needed to do to stay safe first (whatever was decided was between them). I got the stuffed SS boards that Alex Cavalli built for testing, since Wiatrob has been working on my hybrid for 5 months and may not be able to finish. I don't know what I would do without his help in acquiring the parts for me that I was missing and casing it up. He's been very generous with his time and I thank him.


----------



## paxeaxe23

Well I'm really hapy with my SS build. Does anyone have a spare set of Hybrid boards they would be willing sell me? I have the components for it and am VERY curious to compare the two different versions.


----------



## pabbi1

Nate, anything on Hopstretch's unit?

 Frank, Mouser order will be in tomorrow (about 75% complete)... if I could only find that bag if Thermasil pads <grrrrrr>.

 Larry, what all needs to be done on your Hybrid?


----------



## n_maher

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Nate, anything on Hopstretch's unit?_

 

I finished the design of the back panel today, no kidding. Panels will be ordered before the end of the week and it is priority #1 on the bench right now. Knee surgery in late March (coupled with the injury that necessitated surgery) set me back a good 6 weeks on this.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Larry, what all needs to be done on your Hybrid?_

 

I don't know exactly what is left to be done. I haven't heard from Bill since 4/8/10, at which point he said he can't finish any of my projects for me because he's too busy at work now. He said he wants his loaner hybrid back (bad right channel) and will return my "exstata amp & PS boards stuffed, parmetal case, balanced attenuator, jacks", along with other gear of mine. I offered to buy the loaner case if he would put my working boards in it, and he declined.

 As far as I know, the Hybrid is not cased up and I don't know if the face plates are drilled (last I checked they weren't). I emailed him that I could meet him in person and return the loaner eXStatA with bad right channel, in return for my stuff. He also has my Sq Wave amp with broken Sigma 22 that he built, and some crossfeed kits of mine. So, I'm just waiting to hear back and see if he's changed his mind, or wants to meet for the exchange.

 I think that Bill's loaner hybrid which I have here may have originally sustained damage when the PSU board came loose on the way to my home. When the amp was 1st turned on, the PSU board was loose and shorted against the case and the bias wires were loose, so there was no sound. I had gotten things connected again, and it worked for several weeks before the right channel started making static noise under the music (and the right channel noise is in both channels, so it might be the ground is messed up).

 At this point I don't know what to do.


----------



## pabbi1

Anyone (else) taking their eXStatA to CanJam? 

 Any further updates, or observations after living with these for a few months?

 Larry: let me know when you talk to Bill - I can ping him as well, and, most certainly can help get you sorted. Not sure I can help much on Bill's proto if it was damaged, but one at a time.

 Oh, and if anyone still needs tubes... or Amphenol sockets...


----------



## Beefy

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Any further updates, or observations after living with these for a few months?_

 

After confirming that new drivers fixed all of the problems I was having with my SR-Lambda, I haven't listened to my Exstata since. Work sucks


----------



## HeadphoneAddict

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Anyone (else) taking their eXStatA to CanJam? 

 Any further updates, or observations after living with these for a few months?

 Larry: let me know when you talk to Bill - I can ping him as well, and, most certainly can help get you sorted. Not sure I can help much on Bill's proto if it was damaged, but one at a time._

 

Al, I certainly will be likely to contact you. I'd like to give the hybrid to my son to use with his SR-Lambda and SR-003 when it is done. If you are able to sort out the final completion in time then you'd be welcome to take it to CanJam for people to hear as well. I'll give Bill a call tonight, but I don't know when he'll be able to meet me so we can hand over each other's gear.


----------



## macm75

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Any further updates, or observations after living with these for a few months?
_

 

Yeah, one of these days I'll write a little something in the official impressions thread. I do very much enjoy my SR-303 / eXStata setup. I have built a bunch of headphone amps for the Stax and dynamic phones and this setup, by far, is the best I've owned. I know better is out there but for once I do not care, I sit back and simply enjoy.
 The strange thing is either I got completely past the bright upper mids of the 303's or they actually calmed down - I do not notice it anymore. The phones also used to give me fatigue - I can now listen in delight for any length of time. The credit goes to the eXStata. Lastly, and this is a huge issue for me, I feel no need to look further particularly given the music I listen to 90%+ of the time (electroacoustic improv).


----------



## HeadphoneAddict

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Anyone (else) taking their eXStatA to CanJam? 

 Any further updates, or observations after living with these for a few months?

 Larry: let me know when you talk to Bill - I can ping him as well, and, most certainly can help get you sorted. Not sure I can help much on Bill's proto if it was damaged, but one at a time._

 

I just want to clarify a little bit with what has happened with my hybrid eXStatA. Wiatrob has been very helpful for only the cost of parts, with no labor charges at all. He stuffed my hybrid boards and collected the entire sum of parts needed to assemble a complete amp. He's just too busy at work now to complete all my projects, and I understand. He was also working on a Sigma 22 PSU and a Meier Corda Cross kit that I picked up. That was just too much extra work when his hours at work increased as much as they did. There is not a problem with wiatrob, and I wish him the best with his busy job.

 It was also unreasonable of me to ask him to trade my loose parts for his completed personal amp, which he has been without for 4 months. He and I are working closely now, and it looks like we'll be able to work something out. I think he will keep my par metal case, attenuator, transformer and other odd parts while I will put my good hybrid boards into the loaner case and keep it. 

 I believe that I can swap the boards out myself, following the current wiring, or with some help from a few friends here have a working hybrid amp very soon. I also found a broken wire on the left RCA jack that was causing problems as posted in the impressions thread, and I can fix that. I believe it was damaged when the PSU board came loose in transport, and I initially missed it and had to resort to only using the XLR inputs. So, Bill did wire up the RCA right after all.

 Wiatrob is a good guy, and I wasn't intending to stir up trouble for him, but rather was just fishing for help myself.


----------



## pabbi1

Yes, we all owe thanks to Bill for the prototyping he did on eXStatA, and even fixed my first hybrid. Sad that he has no time to hang out, but, maybe, things will rotate to some well deserved leisure time for him, and he can drop in from time to time.

 Glad things are on the right track, and keep us posted.

 I'm feeling some pics from Nate?


----------



## sachu

Well, Larry's SS eXStatA is nearly complete. I am a bit nervous cause thisis the first time I am using a digital volume control (luvdunhill's). I am hoping the build of the digital control is ok when i throw the switch..maybe later tonight if I feel like it, else might delay it till tomorrow.

 I did have a question, Larry wanted a SE to balanced switch, so the one PGA chip is being wired up for the hot terminal (of both left and right as inputs) while the other is wired up for the return terminal. When in SE mode, the chip that handles the return signals have their inputs shorted to ground. This is alright I am thinking. Am I wrong in this assumption?


----------



## Beefy

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Well, Larry's SS eXStatA is nearly complete. I am a bit nervous cause thisis the first time I am using a digital volume control (luvdunhill's). I am hoping the build of the digital control is ok when i throw the switch..maybe later tonight if I feel like it, else might delay it till tomorrow._

 

Test the volume control separately then. Feed it a 0dBFS 60Hz sine wave from a DAC, and test the input and output voltage of the volume control with a multimeter in VAC mode. If you disallow gain, it will start from close to 0VAC and rise up to whatever the input is as you turn the encoder. If you allow gain, you will get up to approx 28VAC, assuming ±15V power supply.

 Or do the initial tests of the amp with both phases of both inputs shorted to ground.


----------



## sachu

SOmething's not quite right. The amp is working in perfect condition, power supplies are fine, no smoke nothing, J1 and J2 both jumpers are sorted, I don't see the output varying at all. It stays at near 0VAC.


----------



## Beefy

The only problem I had was connecting the encoder incorrectly. But I believe that the new board version has a different pin out to mine, so I can't really help you debug it unfortunately.


----------



## sachu

The one that larry's uses is the same one in your amp i believe beefy.

 Can you go over the encoder connections for me? I am using this one.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_The only problem I had was connecting the encoder incorrectly. But I believe that the new board version has a different pin out to mine, so I can't really help you debug it unfortunately._

 

 Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_The one that larry's uses is the same one in your amp i believe beefy.

 Can you go over the encoder connections for me? I am using this one._

 

It should be the same attenuator board as Beefy's, and this board/IC's was acquired back in January. And the Bourns encoder should be the same too I think.


----------



## Beefy

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_The one that larry's uses is the same one in your amp i believe beefy.

 Can you go over the encoder connections for me? I am using this one._

 

Take a couple of photos, and I'll tell you if it looks right.


----------



## Beefy

Ah, its easier if I just type it out......

 Check your digital voltages first. Should be 5V from each 78L05. Should be 5V across one of the LED terminals, 0V across the other.

 Check the encoder terminal block. Top three pins on the outside of the board are grounds. If you have the push-button switch, one of these goes to one half of the switch, another goes to the common (middle pin) on the encoder, one spare.

 The pin with the arrow at the encoder terminals (PA0/pin13 on the ATTiny) goes to the other half of the switch. There is a good chance to troubleshoot here...... if you switch across PA0 and ground correctly, mute will switch on/off. You can measure voltage across the LED terminals to see if mute comes on and goes off with switch presses.

 The other two encoder terminals (PA1/pin12 and PA2/pin11) connect to channel A and channel B on the encoder respectively.


----------



## HeadphoneAddict

Beefy, this is the same board, right?


----------



## Beefy

Yeah, that's the one. I thought this early revision only went to Fet-tastic builders. In any case, you can easily see the encoder block, arrow and LED points I am referring to.

 Only other important point I can think of is that you need to run five power wires on this board version; positive and negative _for each half_, and one ground.


----------



## sachu

Thanks for that Beefy. 
 I had the pins of the encoder switched. Figured PA0 was channel A, PA1 B and PA3 was the switch. 
 I switched it around right now, but still nothing. 
 Also I installed the two LEDs on the board and one led is on all the time while the other LED stays off regardless of what i do. Both the cathode terminals of the leds are soldered down to DGND pin that is between the two LED terminals.

 I am trying to see if the output is varying or not and it is still the same. 

 As for how I am measuring the output, I am using the meter in VAC mode and the hot probe on the output pin and the cold probe on GND.

 Inputs read 310mV wrt GND.

 Feeding a 60 Hz signal at 0dB.


----------



## Beefy

Are you getting 5V from each regulator? Photos will help.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_Are you getting 5V from each regulator? Photos will help._

 

Yeah, Pics. We want pics!


----------



## BoilermakerFan

Hey guys. I had custom r-core PS transformers made for me here in the States. There was a misunderstanding and they made me 4 units instead of 2 units. I don't have to buy the other units, but I had use for the extra SS R-core, however, I do not have a use for the second Hybrid R-core.

 The specs are: 120/240 Primaries/ 480V CT @ 70mA, and (2) 6.3V @ 1.3A Secondaries

 Cost is $95 plus USPS Priority Shipping. I have to let them know if I want the others and I have to pay for them up front, so I'll need funds up front to cover it. The good news is, they are ready to ship on Friday. 

 LMK if you're interested, otherwise I call and only take 3 on Wednesday.


----------



## sachu

oh man...wish I hadn't bought my transformer for the Aikido.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_oh man...wish I hadn't bought my transformer for the Aikido. 
	

	
	
		
		

		
		
	


	


_

 

Any progress with the volume control? Have you PM luvdunhill who supplied it, for trouble shooting tips? Thanks!


----------



## sachu

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Any progress with the volume control? Have you PM luvdunhill who supplied it, for trouble shooting tips? Thanks!_

 

not yet. But will do soon here, been a bit busy with school work..


----------



## HeadphoneAddict

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_not yet. But will do soon here, been a bit busy with school work.._

 

Okay thanks. I appreciate it.


----------



## BoilermakerFan

Man, I'm bummed.  I thought one of my unkown Stax cables was for the SR-003s, but it's not.  Oh well, I'll order a SR-003 cable to go with my SR-001s...


----------



## FrankCooter

One more (solid state) eXStata up and running!  Listening with a pair of Koss ESP950's. Wow! First impression is that this little amp is hitting way above pay grade. Thanks Alex, for a tremendous gift to the community. This is too good not to take commercial, as it puts the high-end electrostatic world withen reach of a much broader group of listeners than ever before.
   
  I also want to thank pabbi1 for stuffing my boards and his contagious enthusiasm for the project. I threw him some junk tube components in exchange, But I certinly got the better end of the deal. My eyes thank you too. Color codes on 1/8w resistors are no fun any more.


----------



## spritzer

Quote: 





boilermakerfan said:


> Man, I'm bummed.  I thought one of my unkown Stax cables was for the SR-003s, but it's not.  Oh well, I'll order a SR-003 cable to go with my SR-001s...


 

 It shouldn't be too hard to make an adapter from some old PC card.


----------



## BoilermakerFan

Quote: 





spritzer said:


> It shouldn't be too hard to make an adapter from some old PC card.


 
  Yeah, I saw that mod and I'll do that as an interim fix, but I do plan to buy a new SR-003 cable too.


----------



## studeb

As there is not a thread for the luvdunhill attenuator, i am asking this here as there should be some builders here.
  Mouser is out of the 0.1uF 50V smd cap LDECB3100KA0N00, and they do not seem to have an identical sub.
  Does any one have three extra to spare? How much larger can this cap go, is 3.2 x 4.5 x 2.4 okay?
  i do not have board with me to check, i have a black one if that matters.


----------



## runeight

Quote: 





frankcooter said:


> One more (solid state) eXStata up and running!  Listening with a pair of Koss ESP950's. Wow! First impression is that this little amp is hitting way above pay grade. Thanks Alex, for a tremendous gift to the community. This is too good not to take commercial, as it puts the high-end electrostatic world withen reach of a much broader group of listeners than ever before.
> 
> I also want to thank pabbi1 for stuffing my boards and his contagious enthusiasm for the project. I threw him some junk tube components in exchange, But I certinly got the better end of the deal. My eyes thank you too. Color codes on 1/8w resistors are no fun any more.


 

 Good news Frank. Glad you like it.  I too thank pabbi1 for all kinds of help.


----------



## graben

So is anyone making eXStata for other people?


----------



## Sathimas

At the moment there are no boards available - otherwise you might find someone who'd build one for you.
  When or if new boards will be made is not certain yet.


----------



## n_maher

Just for Al, finally making some progress...


----------



## pabbi1

Sweet, Nate... too bad you're having to change the input voltage, huh?      Will she make it to CJ?
   
  Anyone else have impressions??


----------



## n_maher

Sadly she won't make CJ but it'll be because she's halfway around the world.  And it'll be world-voltage capable so Stretch can spread the love wherever he goes.
  
  Quote: 





pabbi1 said:


> Sweet, Nate... too bad you're having to change the input voltage, huh?      Will she make it to CJ?
> 
> Anyone else have impressions??


----------



## padam

Quote: 





pabbi1 said:


> Anyone else have impressions??


 

 Just got it today (finally!)
  Drives the Sigma Pro very well if XLR input is used, the usual roll-off problems are there but the muddiness has gone away and the mid-bass hump has been reduced as well. With unbalanced input it seems to struggle a bit but the Sigmas are not easy to drive and balanced seems to work very well.


----------



## FrankCooter

Quote: 





pabbi1 said:


> Anyone else have impressions??


 


 Got about six hours on my solid state. Pairing it with "new to me" Koss ESP950's. The exSTata drives the 950's with a very dynamic, tight, and articulate presentation that energizes rock music in a way that my SRD-7/Lambda system never did. I've got Van Halen blowing my brains out with power and ease at 40% volume. Reminds me more of the HE-5 orthos than the Stax Lambdas. I haven't played much besides rock music yet. I keep daring this little amp to run out of steam, but it's taking everything I throw at it. As both headphones and amp are new to me, I'm not sure how to parcel out the credit. I do know however, that this is one killer combination. I'm having a blast.
   
  If any more boards are made, I definitely want a pair of the hybrids.


----------



## sachu

^^ that's an amazing pairing IMO. The ESP950 never impressed me on the Stax amps or the BHSE.  With the eXStatA..a whole new ballgame.


----------



## Frihed89

Can someone confirm this, or not?
   
  1.  There is no one selling an exstata kit
   
  2.  There is no exstata kit
   
  3.  There is no main board for the exstata
   
  4.   There are no plans to do 1 through 4.
   
  What happened?


----------



## pabbi1

The is not (and never was) a kit nor plans for a kit. Strictly boards and a published BOM.
   
  Edit: Not my place to speak about this design, as it does not belong to me.


----------



## sachu

^^^ Nice!!


----------



## HeadphoneAddict

I'd love to see a commercial version.  There is a definite need for an amp that doesn't break the bank, and where people aren't forced to buy vintage amps in order to drive the O2 on a tight budget.


----------



## padam

Here is how mine looks like:
   

   
Submit


----------



## Sathimas

A little update - looks much cleaner now, that MDPC-X sleeve is just amazing


----------



## n_maher

We've gotta get you guys to start flush mounting your IECs.


----------



## les_garten

Show-Off!


----------



## sachu

That is sweet Nate..I am all ears as to how to get that look. 
	

	
	
		
		

		
			




   
  Is it just that you need a cavity on the other side?


----------



## runeight

Quote: 





frihed89 said:


> Can someone confirm this, or not?
> 
> 1.  There is no one selling an exstata kit
> 
> ...


 

 The exstata was never planned as a kit, but only as diy board sets. No one is selling any that I know of. The last run of boards was in early 2010. There is not currently another board run planned although I am thinking about it.
   
  So nothing really happened. That is, nothing went wrong but everything went right. All the exstatas that have been built properly are working the way they are designed to. Including some of the early alpha amps that worked well and have flowed out from builders to others I estimate that 60 board sets have gone out and been built.
   
  If I may ask, what's on your mind?


----------



## HeadphoneAddict

Quote: 





runeight said:


> The exstata was never planned as a kit, but only as diy board sets. No one is selling any that I know of. The last run of boards was in early 2010. There is not currently another board run planned although I am thinking about it.
> 
> So nothing really happened. That is, nothing went wrong but everything went right. All the exstatas that have been built properly are working the way they are designed to. Including some of the early alpha amps that worked well and have flowed out from builders to others I estimate that 60 board sets have gone out and been built.
> 
> If I may ask, what's on your mind?


 

 He wants to buy or build one, that's what's on his mind.


----------



## n_maher

Quote: 





les_garten said:


> Show-Off!


 
   
  Quote: 





sachu said:


> That is sweet Nate..I am all ears as to how to get that look.
> 
> 
> 
> ...


 
   
  It is not hard (with CNC machined panels) but both dependent on the panel thickness that you're working with and an IEC module that has a sufficient projection to extend through the panel.  This one just sort of happened to work this way, I honestly didn't plan on doing it this time but when I saw that it did work I took advantage.   I'm not sure that I would try it if the panel was too thick, back side recesses are very expensive.  And doing it by hand would be almost impossible to have it look really good, although once I have my mill I may give it a shot.


----------



## runeight

It does really look good though even if you weren't planning on it.


----------



## pabbi1

When an engineer tells me something just worked out, well... me hate you long time. Can't tell you how many times I heard that in my 11 years at TI (Texas Insolence) - no one believed it there either.   
   
  Ok, guys, real pretty, but HOW DO THEY SOUND? Nate, that includes you...
   
  Master has me listening to hd800 again. Those of you at CanJam will see why.


----------



## sachu

Quote: 





pabbi1 said:


> Master has me listening to hd800 again. Those of you at CanJam will see why.


 

 Master and you should listen to the LCD-2.....look forward to impressions on that pairing. Don't miss it Al!


----------



## pabbi1

Brian has some scheduled to be there - wouldn't miss it.


----------



## awpagan

Quote: 





runeight said:


> The exstata was never planned as a kit, but only as diy board sets. No one is selling any that I know of. The last run of boards was in early 2010. There is not currently another board run planned although I am thinking about it.
> 
> So nothing really happened. That is, nothing went wrong but everything went right. All the exstatas that have been built properly are working the way they are designed to. Including some of the early alpha amps that worked well and have flowed out from builders to others I estimate that 60 board sets have gone out and been built.
> 
> If I may ask, what's on your mind?


 

 Runeight
  So the next question is...............
  Is there anything needed to be changed/modified on the board layout? So the boardsets can be made commercially available.
  At present the heatsinks need to be earthed.(SS version) but is easy to workaround.
  Is there any suggestions from yourself or ones who have built them?
   
  This amp deserves to be made available to the larger community.


----------



## padam

Very nice, the low end is excellent. The output at the high frequencies might be a bit limited so it might be a better match with brighter headphones. Or the Sigma Pro as well since it is rolled-off at the top anyway but the usual Sigma "fogginess" has completely gone, it has the power to drive if balanced input is used.
  I will soon have something moar interesting to test it out with 
	

	
	
		
		

		
		
	


	



  
  Quote: 





> Originally Posted by *pabbi1* /img/forum/go_quote.gif
> But HOW DO THEY SOUND?


----------



## sachu

Looks like I might be in need of a quad of JFETs. Anyone got a spare set.


----------



## n_maher

I have spoken with Alex about his intention to take the eXStatA project in a commercial direction and about how that decision affects this thread.  Until that matter is resolved (between Alex, Jude and the moderation staff) and since there are currently no more boards available I'm going to lock this thread.  It's a complex issue and I would ask for you patience in dealing with it.
   
  If other members (like myself) wish to continue discussing this project and the various builds that are still under construction I would ask that you start another build thread to do so.  Odds are I'll be starting one myself since I just started wiring the power supply of mine today. 
   
  Nate
  Head-Fi Moderator


----------

