# Wow!  Inexpensive tube amp kit for newbies



## Wodgy

I just ran across this _*very*_ inexpensive tube integrated amp kit. Looks almost like the perfect kit for people wanting to take baby steps into tube DIY (almost like a tube version of the CMOY)... everything's included and there's a PCB so very little point-to-point wiring is needed:
http://www.web-tronics.com/sterintubamk.html

 Plus more info here:
http://s5electronics.com/gpage1.html

 8 watts for only $139, and you also get a free multimeter, so the cost is probably really only around $100. Not bad. I'm sure it doesn't sound incredibly wonderful, but I'm going to try it out just for fun, and I'll let you guys know how it sounds with both speakers and headphones.


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## Sol_Zhen

That's pretty cool. I'm interested in a report. The kit looks pretty easy to follow.


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## Toe

8 watts? Sounds like a candidate for the K1000s. Anyone care to give it a shot?


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## aeberbach

It looks nice, but a beginner's kit without a case? Tubes run on dangerous voltages and I don't think it's a good idea to have everything out in the open like that, PCB or not. The instructions available for download don't have much in the way of warnings.

 The tube used is "11MS8". It isn't one I know and there is no mention of it in usenet archives except in "for sale" listings. 
 It's not a lot of money to waste if it turns out to be junk, but I wouldn't be hoping for any miracles.

 A better picture with more specs is here:

http://www.tubeaudio.com/page23.html

 Oh yeah, and it's push-pull. That means you need carefully matched tubes to minimize crossover distortion - I bet you don't get matched tubes for $139.


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## Wodgy

Yeah, I'm not expecting miracles, or anything much really. But I haven't built anything electronic for about 10 years now, and for around $100 (I don't have a multimeter, so I like that aspect too) it seems like a neat baby steps project, and if I make mistakes or fry it by replacing the bridge rectifier with four FREDs I really won't mind. It's sort of like the CMOY/META42 thing. Everyone recommends starting with a CMOY with cheap parts before attempting a META.

 As for the 11MS8, you might be surprised. Unpopular tubes are very easy and cheap to buy NOS and closely matched. I've bought a bunch of replacement pairs of 12SN7's for my Mapletree Line2m and the whole slew of them haven't cost me more than $25 total.

 And with push-pull you tend to get better bass stability than some of the cheaper single-ended designs.

 I love how the web page Aeberbach mentioned has a quote that says "Good bye Krell, hello S-5". Laughed out loud at that


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## Budgie

Looks like a good canidate for tweeking.


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## ofb

i don't know what i'm talking about, but perhaps someone here can point out the difference.

 the foreplay preamp is an audiophile quality kit for only $10 more.

http://www.bottlehead.com/et/adobesp..._stage_kit.htm

 i realize that's not quite the same thing, but i'm wondering if the foreplay could be easily modified into a good starter tube headphone amp, rather than trying to upgrade the web-tronics.

 just a thought.


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## Wodgy

I think the Foreplay primarily does voltage gain; it probably doesn't produce enough current to power any headphones. Everyone says it's a good preamp though, especially with all the upgrades. I think the best deal for a DIY tube headphone amp is probably the Mapletree Ear at $275, plus it apparently drives Grados really well, and has a preamp out to boot.


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## Nick Dangerous

(it's worth the extra $50 to get the Mapletree Ear+)


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## andrzejpw

Hmmm, anyone want to take the plunge?


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## Wodgy

Quote:


 _Originally posted by andrzejpw _
*Hmmm, anyone want to take the plunge? * 
 

I just ordered a kit today. Might have time to assemble it by the middle of next week, hopefully. They not only threw in the digital multimeter, but also a free set of screwdrivers. Don't know why, it didn't say anything about the screwdrivers on the website.


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## Serow

Check out the thread at Headwize about this amp. PRR mentioned that you can "simply break the traces to Pins 7 and strap 7 to 6. Instant Triode." You will be down to 3-4 Watts, but everyone likes triodes, right
	

	
	
		
		

		
		
	


	




 .


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## Wodgy

The nice UPS lady delivered the kit to my door earlier today. It looks great for something so inexpensive. The parts don't seem to be chintzy -- the power transformers weigh about 15 lbs, the caps are by Samsung, and the RCA jacks are gold plated.

 The tubes are NOS Japan, and the base is 3/4 inch solid wood. The kit also came with a free multimeter, with _batteries included_ -- nice touch. The guys at Web-tronics also threw in a set of free screwdrivers.

 Here's a picture of the kit contents, in case anyone's interested:


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## Wodgy

Finished building the kit! Total construction time was just under six hours. The PCB makes it very easy for a beginner.

 Looks absolutely gorgeous in the dark:


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## andrzejpw

So, how does it sound?


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## Wodgy

Quote:


 _Originally posted by andrzejpw _
*So, how does it sound? 
	

	
	
		
		

		
			



* 
 

Very, very good. I'll post detailed listening impressions once I've had some more time to evaluate it, but I can say a couple of things right now:
 - For an 8-watt unit, it plays LOUD; I have a fairly large apartment and the volume knob hasn't been beyond 12 o'clock. It's definitely good enough for most reasonable rooms and ordinary speakers. The push-pull design (as opposed to single-ended) might have something to do with it being able to handle ordinary speakers so well.
 - It sounds very good. It does some things better than my Fisher 400 (not everything though), and it definitely sounds better across the board than the solid state NAD C350 I used to have.
 - With an added headphone jack, it drives Grados _much_ better than the MG Head. On the other hand, my first impressions with the Etymotic 4S weren't as good; the MG Head bested it there.

 I'm going to take the unit to a friend's place today and see how it plays on Paradigm Monitor 3s, which are more demanding than my PSB Alpha B bookshelf speakers.

 I can wholeheartedly recommend this kit to someone who would like a good tubed speaker amp that can also be used as a headphone amp for Grados. If I was a freshman in college, this plus a set of reasonable speakers would make a killer dorm stereo system. I honestly like the unit so much that I'm going to mount it in a nice enclosure and give it to a friend of mine who's studying opera and normally listens through a cheap boombox.


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## andrzejpw

Hmmm, if this amp is good for grados(all low impedance phones?), maybe it could turn into a poor-man's mapletree. . .


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## Wodgy

The Mapletree Ear kit isn't very expensive either. It's about 100 dollars more than this kit, I think (can't remember the exact price). Though I'd definitely go with the Mapletree if all I wanted was a headphone amp, since that's what it was designed for.


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## Budgie

http://hollowstate.netfirms.com/

 (Mapletree)


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## ofb

For amusement I did a search on the designer, George H. Fathauer, author of Electron Tube Locator, and came up with a nice shot of him with an earlier project.

http://www.earlytelevision.org/georgefathauer.html


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## Wodgy

That is so neat! Thanks for the link ofb.


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## mekanoplastik

is there an easy way to transform this amp into a headphone amp.. ??


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## Joe Lau

Quote:


 _Originally posted by mekanoplastik _
*is there an easy way to transform this amp into a headphone amp.. ?? * 
 

 I think it can change to headphone amp by : 

 1. connect it to triode mode.

 2. Change nfb resistor to lower the gain to avoide over power on headphone.

 3. It may be can even lower the gain by remove some by pass capacitor on cathode of driver tubes.


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## ofb

wodgy, so how does the little enconovalve amp sound now that you've lived with it a while?

 i just mean to encourage, not to poke. i'm sure you're busy.


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## Wodgy

I've had this inexpensive amp for about three weeks now, so I'm fairly sure it's been well burned in. I thought I should post an updated set of impressions about it...

 (I've actually spent quite a lot of time listening to this amp because one of the output coupling caps on my Fisher 400 fried itself a couple weeks ago, leaving me with only this little amp.)

 I'm using it with PSB Alpha B bookshelf speakers and a PSB SubZero subwoofer (hooked up to the speaker outputs of the little tube amp, along with the bookshelf speakers). The room is medium size, and the amp can play louder than I'd ever want it to in this room. (Sorry that I can't comment too much on how this amp sounds with headphones because I haven't had much more of a chance to use it with headphones over the last couple of weeks.)

 Anyway, I still think this amp sounds great. It's fast, not soupy or slow like some vintage tube amps. It is definitely faster than the Fisher 400 (though the Fisher trades speed for more of a lush tubeyness), and I think it wouldn't disappoint solid state fans. The midrange has the trademark tube realism and presence, and the highs are solid and not rolled off, while at the same time not at all harsh (and, believe me, the Alpha Bs can sound _harsh_ with a badly matched amp). The little amp may be slighly rolled off in the very lowest frequencies, but any roll off is relatively minor. I watched "The Cell" on DVD tonight and there's a ton of low-frequency energy in that movie, and it came through very nicely. Also, I suspect this amp runs in class A (I haven't heard any crossover distortion).

 Also, this little amp is also pretty easy to tweak, but I'm really in no hurry to make any mods. The stock NOS tubes sound good to me, and I haven't rolled them yet.

 I definitely do recommend this amp. It's inexpensive, but it doesn't sound cheap. Plus, it was fun to build. If I had to choose between a low-cost NAD solid-state integrated like the C350, or this kit, I'd choose this kit. It just sounds better.

 (If you'd like a remote control, you can always get a remote controlled preamp and hook this thing up as a power amp.)


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## Nick Dangerous

Are you running it as SET?


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## Wodgy

It can be modded to run in pure triode, but not in SET [single-ended triode, for newbies]. This is a push-pull amp, not a single-ended amp, which might explain the solid bass for such an inexpensive price. The designer was clever -- normally a push-pull amp would need more than four tubes, but the 11MS8 have a power section and a completely separate preamp section. They're weird looking tubes (I pretty much guarantee you haven't seen anything like them -- I hadn't), but that's part of their appeal.

 I'm haven't modded it to run in triode yet. I believe that it would still be loud enough for me (in triode, it would produce about 4 watts), but it probably wouldn't be loud enough for party levels, or Carmina Burana, so I'd probably want to mod it with a triode/pentode switch, rather than make the mod permanent. Of course, if I had more efficient speakers, it could probably be permanent. I'll probably play around with triode eventually, but I'm busy in the short term, so probably not for a month or so.


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## Wodgy

A suggestion for anyone who's building this amp: add a resistor to reduce the filament voltage from 12V to 11V.

 I had a tube burn out on me last night, and looking at the schematic I realized that the filament voltage is 12V, even though the optimal voltage for 11MS8s is 11V. This reduces the tube lifespan, especially if the power in your house is as dirty and variable as mine. 11MS8's aren't expensive, but they should last at least a couple of years.


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## ofb

I was just doing a search for new info on this little amp, and google's cache shows it was reviewed in the November issue of audioXpress.

 Did anyone here catch that article? Was it just a thumbnail sketch or did it have fresh observations?

 --

 For others who are curious, there's not much out there beyond retailer blurbs and a few low signal threads on Audio Asylum.

 Here's a couple of links to people who got playful with cases.

http://www.tubeaudio.com/page8.html

http://www.andix.co.jp/kit1.htm

 --

 How's your project going, Wodgy? And what's that pretty little amp you're using for your member photo? Looks like a padauk frame.


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## Wodgy

Ofb, thanks for the pictures... I'm impressed you managed to find that Japanese page!

 The amp in my member photo is the wood and steel Meta42:
http://www.head-fi.org/forums/showth...threadid=19177


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## ofb

Quote:


 _Originally posted by Wodgy _
 The amp in my member photo is the wood and steel Meta42 [/B] 
 

my goodness. that is very nice.

  Quote:


 I'm impressed you managed to find that Japanese page! 
 

google is the surfer's friend. also with this amp you can get somewhere by searching for its unusual tube.

 i still haven't seen the audioXpress article, but have a second hand report from a non tech friend. he said it was a multipage review with a number of charts, and under criticisms it noted trouble with the tube sockets failing from heat. writer said the company was considering going to ceramic.


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## PinkFloyd

Certainly seems good for the money... that's about £70 sterling? At that price it's nothing short of a miracle!

 Pinkie


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## aerius

Quote:


 _Originally posted by Wodgy _
*A suggestion for anyone who's building this amp: add a resistor to reduce the filament voltage from 12V to 11V.
* 
 

I can solder with the best of them but I can't read electrical diagrams if my life depended on it. Where would I stick a resistor to drop the voltage down, and what kind & value of resistor would I need? I ordered the kit a few days ago and I'm expecting delivery any day now. Help me please?


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## zowie

I found the amp in a monoblock version at www.tubesandmore.com Only $85 each!

Fathauer monoblock


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## Gariver

Aerius:

 You should get this book: Beginner's Guide to Reading Schematics, 2nd Edition, by Robert J. Traister and Anna L. Lisk. With it, you will be able understand all the schematics and diagrams of electronic circuits. You can get it at Amazon.com or at BarnesandNoble.com.

 Good luck to you!


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## aerius

Gariver: I eventually figured out most of the circuit for the amp after looking through my old electronics textbook and playing with the amp a bit. There's still some stuff I'm a bit iffy on but I'll get it figured out in time. I'll see if my local libraries have a copy of that book since I'm too broke right now to buy it. Damn you Head-fi, damn you!


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## Gariver

Aerius: I understand. So how about the internet? You can do a Google.com search for "schematic symbols." Here's one site I found...

http://webhome.idirect.com/~jadams/e...nics/schem.htm


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## Gariver

ofb mentioned that Audio Xpress did a review of this Fathauer PP amp. So I went over there to check, and I found something interesting. AX now has its back issues in CD Rom...

http://www.audioxpress.com/bksprods/newitems.htm

 I bet these CDs are loaded with interesting projects. Maybe too many. Ha!

 Wodgy: Good luck with your amp! It sure looks interesting to me!!!


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## aerius

Update. I've had this amp for a bit over a month now and it's getting pretty tweaked out. The latest upgrades were doubling the size of the electrolytic caps and putting in an Alps Blue pot in place of the stock one. This is in addition to the Wima film caps, 1% metal film resitors and a couple Vishay-Dale resistors I put in there when I first built it.

 The reason I put an Alps pot in was because the original one tracked really poorly at low volumes, and the right channel would fade and cut out way before the left. Normally I wouldn't care but recently I've been using my 'phones more for quiet background music while reading and the imbalance was really bugging me. Going by the "buy quality and only cry once" motto I splurged on the Alps pot which fixed the volume imbalance and cleaned up the sound a bit too. Now that both sides match properly in volume, stereo imaging is better and I'm noticing more subtle details in the music. It also got rid of the transformer hum problem I was having before, I don't know how or why but it did.

 I was also thinking that the electrolytic caps for the power supply section were too small, it was just a gut feeling, nothing else. The amp had a grand total of about 340uf worth of caps on it which seemed kind of inadequate seeing that other DIY designs had at least 5-10 times as much. So I got the largest caps I could fit on the board, which about doubled what I had before. I also put film bypass caps for the electrolytics in case the larger values were too slow. End result? The sharp snare drum "thwack" in Hendrix's _Machinegun_ from the _Live at the Fillmore East_ had more impact and literally knocks me back when played at high volume. I was expecting improved bass which I might have gotten, but what I did get was unexpected and good.

 I'm really liking this amp, it sounds good and there's definitely lots of room for tweaking and improving the stock design.


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## Voodoochile

"The sharp snare drum "thwack" in Hendrix's Machinegun from the Live at the Fillmore East had more impact and literally knocks me back when played at high volume."

 That's a nice piece, eh? 
	

	
	
		
		

		
		
	


	




 I might have to get one of these kits, it sure sounds tempting.


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## Wodgy

aerius, thanks for posting your mods. Keep us posted on your experiments!

 Have you thought about converting the tube heaters to DC? This would be a fairly easy mod. Just get a 12V wall wart (preferably regulated, since an unregulated one might not be a big improvement and might lower the tube lifetime) and hook it up in place of the current AC heating.

 Also, I've found that this amp really moves to another level entirely if you use a preamp with it. I've been using my Meta42 as a preamp and it's quite satisfying.

 Even completely stock, though, I still think this kit is really awesome.


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## Ohoen

> _Originally posted by aerius _
> "I was also thinking that the electrolytic caps for the power supply section were too small, it was just a gut feeling, nothing else. The amp had a grand total of about 340uf worth of caps on it which seemed kind of inadequate seeing that other DIY designs had at least 5-10 times as much. So I got the largest caps I could fit on the board, which about doubled what I had before. I also put film bypass caps for the electrolytics in case the larger values were too slow. End result? The sharp snare drum "thwack" in Hendrix's Machinegun from the Live at the Fillmore East had more impact and literally knocks me back when played at high volume. I was expecting improved bass which I might have gotten, but what I did get was unexpected and good."
> 
> What value power caps did you use? I just ordered this kit so I'll probably be putting it together this weekend if it gets here and I thought I might use bigger caps right off the bat. I'll have to order them though. Thanks.


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## 2 channel

Has anyone used this amp w/ any type of preamp? Could it be built w/out the volume pot as a power amp and then a preamp used?

 Sorry if this is a basic question, I am a total DIY newb!


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## Wodgy

Yes, I've used this with a preamp to good results. Right now I'm using it with my Meta42 doing double-duty as a preamp/headphone amp. I haven't removed the volume pot, I just set it to the midpoint, but if you would like to make this into a pure power amp, just leave out the volume pot and put jumper wires from the ends of C1 and C4 to the grids of the first tube stages. By the way, here's a schematic of the low-cost tube amp:
http://www.circuitspecialists.com/products/km12sch.jpg

 If you also have the schematic to your preamp and know that it has input coupling caps, you can also leave out C1 and C4 when building the amp, and just connect the inputs directly to the grids. This would likely improve the bass response of the amp.

 (You may also want to put a 50K resistor in series in place of the potentiometer, but you'd have to experiment with this. The best bet would be to put in a SIP socket so you could experiment with using a resistor or just using a jumper wire.)

 Another advantage of using a preamp is that you can use a powered subwoofer in conjunction with this tube amp. This is what I do.


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## aerius

Quote:


 _Originally posted by Ohoen _
*What value power caps did you use? I just ordered this kit so I'll probably be putting it together this weekend if it gets here and I thought I might use bigger caps right off the bat. I'll have to order them though. Thanks. * 
 

I ended up with a 470uf, 220uf, and 47uf caps in place of the stock ones. I can't remember what value of film caps I used as the bypass caps, and those ones are soldered on the bottomside of the board so I can't exactly read off the values. I think they're about 0.33-0.5uf caps, but I'm not 100% sure. 

 Thankfully I didn't have to order anything, as there's a nice electronics store in my city that stocks Wima caps, Alps pots, and a few other goodies in addition to tons of normal caps and resistors. My city is filled with electronics supply stores, it's a DIY shopping paradise!


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## earthling

Quote:


 _Originally posted by aerius _
*I ended up with a 470uf, 220uf, and 47uf caps in place of the stock ones. I can't remember what value of film caps I used as the bypass caps, and those ones are soldered on the bottomside of the board so I can't exactly read off the values. I think they're about 0.33-0.5uf caps, but I'm not 100% sure. 

 Thankfully I didn't have to order anything, as there's a nice electronics store in my city that stocks Wima caps, Alps pots, and a few other goodies in addition to tons of normal caps and resistors. My city is filled with electronics supply stores, it's a DIY shopping paradise! 
	

	
	
		
		

		
			



* 
 

Where in TO are you finding this paradise? I am in the North east side, North of 401, east of 404.


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## aerius

Quote:


 _Originally posted by earthling _
*Where in TO are you finding this paradise? I am in the North east side, North of 401, east of 404. * 
 

Supremetronics on Queen St. just a bit west of the City TV building, they have Alps pots, Wima caps, and lots of transistors. They also have some spiffy looking jacks for interconnects.

 Edit: Did I also mention that they also have regular and toroidal transformers as well as sheilded OFC and silver wire?


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## Voodoochile

I'd be sooooo broke if I lived in Toronto!


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## earthling

Quote:


 _Originally posted by aerius _
*Supremetronics on Queen St. just a bit west of the City TV building, they have Alps pots, Wima caps, and lots of transistors. They also have some spiffy looking jacks for interconnects.

 Edit: Did I also mention that they also have regular and toroidal transformers as well as sheilded OFC and silver wire? * 
 

Thanks. I am somewhat alergic to downtown (no offense) especially when its this cold out but I do make it down there once in awhile and I will have to check this place out.


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## Ohoen

Thanks aerius! The kit got here today so assembly starts tomorrow night.


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## kevin_irene

Hi Wodgy, I'm interested in getting this kit but over here my power supply is 230vac 50Hz. So could you give me more detail information of the power transformer T1?

 cheers,
 kevin


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## aerius

It just happens that I took voltage readings on the power transformer since I was thinking about replacing it. With a 115-120V input which is what we have in Canada, it gives a 12V output that powers the tube heaters, and a 175V output that gets rectified and fed to the tube plates. The 12V output has a centertap on it, while the 175V one does not.

 I've looked around all the electronic supply stores in my area and I couldn't find a similar transformer, so I'm thinking the transformer is probably custom made. The easiest way I can think of to get around this problem is to get 230V to 115V transformer and put it in front of the power tranformer to feed it the correct voltage. There's probably other ways to do it but that's the one that comes to mind right now.


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## kevin_irene

hi aerius, is there anyway i can find out the current ratings too? i know that the tubes need 0.45ma each for the other and this works out to 1.8A for the 12Vac secondary output. What about the current rating for the 175Vac ouput? Thanks! where did you solder the bypass cap??

 anyway, what speakers did you guys use?


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## aerius

I can't take current readings for the 175V output since everything's soldered together and I'd have to unsolder a wire or 2 to get the current meter in there. Anyways, I took a reading of the rectified DC voltage which is about 200V. According to the spec sheets each tube uses a maximum of 8W at the high voltage plates, which works out to 32W max, giving a max current of 0.16A DC, or about 0.18A AC at the transformer secondary. It's been a while since I last took an electronics class so my math might be off.

 The bypass caps I just soldered to the "legs" of the electrolytic caps on the bottomside of the board.

 As for speakers, none for me. I'm using the amp to drive my Sennheiser HD-580 headphones through a homemade version of the headphone adaptor shown about halfway down the page on this thread.


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## Wodgy

I've been using it with PSB Alpha Bs (91dB sensitivity) and some DIY speakers using unknown full-range single drivers. Hopefully I'm going to try it with Marble nOrh 3.0s next week.


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## ofb

Quote:


 _Originally posted by aerius _
*I've looked around all the electronic supply stores in my area and I couldn't find a similar transformer, so I'm thinking the transformer is probably custom made.* 
 

i was wondering about the origins of this amp myself. since mr. fathauer is an 'old hand' and also seems to reside in arizona, which seems to be the source of these amps, i've been thinking what it may be is something designed to use up surplus stock, and not necessarily from audio applications.

 i'm not suggesting this is bad in any way. someone with mr. fathauer's deep experience certainly knows what he's doing. it'd be quite wonderful to hear directly what his choices were based on.

 and it could as easily be custom iron; no doubt mr. fathauer knows a great many sources.

 ... oh and aerius, please don't gloat again about the availability of things in toronto. 
	

	
	
		
		

		
		
	


	




 so many times i've thought things would be easy if i could only wander down to queen st again. 3000 miles away now, and i'm glad i moved, but there's sure nothing like that out here.


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## kevin_irene

thanks everyone for their comments. hi aerius would you be so kind to show me the website of the 11ms8 data spec sheet if there's any. i cant seem to find anything more except this here 

  Quote:


 _Originally posted by aerius _
*I can't take current readings for the 175V output since everything's soldered together and I'd have to unsolder a wire or 2 to get the current meter in there. Anyways, I took a reading of the rectified DC voltage which is about 200V. According to the spec sheets each tube uses a maximum of 8W at the high voltage plates, which works out to 32W max, giving a max current of 0.16A DC, or about 0.18A AC at the transformer secondary. It's been a while since I last took an electronics class so my math might be off.

 The bypass caps I just soldered to the "legs" of the electrolytic caps on the bottomside of the board.

 As for speakers, none for me. I'm using the amp to drive my Sennheiser HD-580 headphones through a homemade version of the headphone adaptor shown about halfway down the page on this thread. *


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## aerius

Quote:


 _Originally posted by kevin_irene _
*thanks everyone for their comments. hi aerius would you be so kind to show me the website of the 11ms8 data spec sheet if there's any. i cant seem to find anything more except this here * 
 


 That's the same one I got the wattage figures from. I do remember seeing a similar one somewhere but I can't find it anymore.


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## Ohoen

Ok, so we built the thing. It was really easy, really fun, and sounded good right away. It's totally stock. I'll be giving it to my girlfriend cause I don't have speakers efficient enough for it. However, I like it enough to consider building two more as bridged monoblocks to use with a preamp (Bottlehead Foreplay?). I'm new to electronics and all this, though. Anyone know what it would take to build a bridged version of these? What does everyone think of this idea?


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## Wodgy

A couple updates on this kit...

 I've noticed that they're now selling a new pre-built, optional case to go with the amp. The case isn't quite as good a deal as the amp itself, but it is nice-looking, sort of like the tube amplifiers of the early 50's. More info and pictures here:
http://www.s5electronics.com/tube6.html

 The manufacturers are also offering to supply _for free_, plastic grommets that eliminate the socket "scorching" effect some have observed. More info here:
http://www.s5electronics.com/tube4a.html

 Also, lately I've been using this kit with marble nOrh 3.0 speakers. These are substantially less efficient (87 dB) than my previous PSB Alpha Bs (91 dB), but the amplifier still drives them more than loud enough for me in my medium-sized living room. The amp is slightly slower with this setup, but that's probably fair considering that it has to put out more than twice as much power to drive these speakers. I probably wouldn't choose speakers much less efficient than this with this amp, but 87 dB efficiency seems to be okay. Note that I'm using this amp with a Meta42 as a preamp.

 I'm liking this amp so much that I'll probably do some of the mods Aerius tried (hopefully this will improve the speed just a bit with the more demanding nOrhs), plus add a regulated DC power supply. Must also think about a cool case design...


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## aerius

Latest update in my ongoing mods to this kit. I've just converted the tube heaters to DC and stuck a 1/2 ohm resistor in series with the 12V supply to drop the voltage down a tad. The amp is now a bit quieter and the transformer runs a lot cooler now that it has it's workload cut in half. With a quieter amp I played around with the resistor values in my headphone adaptor doohickey so the amp sounds a bit more lively now.

 I've also gone to an off-board capacitor setup so I can experiment with different cap values without worrying about damaging the board from soldering and de-soldering parts all the time. I went nuts with the caps and ended up with almost 5000uf worth of them on the board compared to the original 342uf. I don't think there's any gains to be made once you go past about 4X the original values, but hey, someone had to try it. I also learned that 3000uf at ~200V will vaporize test probes with a blinding flash and deafening bang if one accidentally shorts out the caps. Scared the **** out of me! Note to self, don't do electronics work when tired.


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## ofb

there's an article on tweaking this interesting budget amp over at VoltSecond. includes scope pics.


----------



## jeffreyj

Quote:


 _Originally posted by aerius _
*Latest update in my ongoing mods to this kit....
 I've also gone to an off-board capacitor setup so I can experiment with different cap values without worrying about damaging the board from soldering and de-soldering parts all the time. I went nuts with the caps and ended up with almost 5000uf worth of them on the board compared to the original 342uf. I don't think there's any gains to be made once you go past about 4X the original values, but hey, someone had to try it... * 
 

There's definitely a dimishing returns effect here. The amount of energy a capacitor can store is directly proportional to the capacitance, but proportional to the square of the voltage. To put this into perspective, a 100uF capacitor charged to 100V stores just as much energy (1 joule) as a 10,000uF capacitor charged to 10V. Put that in your pipe and smoke it


----------



## aerius

Quote:


 _Originally posted by ofb _
*there's an article on tweaking this interesting budget amp over at VoltSecond. includes scope pics. * 
 

Just when I thought I had it perfect...guess I'll be rebuilding the high-voltage part of the power supply when I get a bit of time.

 On to my latest tweak, Tuberolling! I got myself a set Sylvania tubes just because I could. These ones have gold lettering and are made in Japan (according to the lettering). These babies filled in the bass quite nicely, and with my craptacular Panasonic CD/DVD player it's almost indistinguishable from my Gilmore. The Gilmore's running of a +-15V PSU instead of the spec'd 16.4V so its not at its full potential. The Gilmore gives metal a bit more aggression and headbanging goodness but that's about it with my setup.

 Before the tube swap I could hear the opening bass notes to Tori Amos's "Liquid Diamonds", now I can hear and feel them. Crank the volume up and I can feel the headphones (Senn 580's) vibrating my head, which it never really did before. As far as I can tell these new tubes do everything else just as well as the original ones, the "Trinity Sessions" CD by the Cowboy Junkies sounds just as sweet, the cymbals still have that nice shimmer and I can still hear every little detail.

 If I didn't have a Gilmore or do the switch I don't think I'd have noticed the missing bass with the original tubes. But since I do I don't think I'll be going back.


----------



## Voodoochile

Quote:


 _Originally posted by aerius _
*As far as I can tell these new tubes do everything else just as well as the original ones, the "Trinity Sessions" CD by the Cowboy Junkies sounds just as sweet, the cymbals still have that nice shimmer and I can still hear every little detail.* 
 

I love that disc. Nice update, too, aerius.


----------



## BPRJam

The discussion on this thread has me interested, but I'm a little concerned about what I'd use it for.

 The spec says 8 watts per channel. Correct me if I'm wrong, but you can really only drive small bookshelf speakers with this power output, and 8 watts would be HUGE for a headphone amp.

 Or, am I completely wrong in this?

 That being said, is the only real use of this amp (at least un-modded) to drive small bookshelf speakers?


 BPRJam


----------



## Voodoochile

It's all about efficiency. If your speakers are very efficient, even one watt can provide plenty of volume.

 Many speakers are not very efficient, though.


----------



## BPRJam

I understand about the efficiency of the speaker, but most larger bookshelf speakers have a minumum power requirements on their spec sheet.

 For instance, the Klipsch RB-75 has a effeciency of about 97dB, but has a minimum power requirement of 20Watts (if memory serves). This effectively rules out use of this amp if you are concerned with preserving your speakers. I know that Polk speakers, while much less efficient (i.e. usually around 89 dB) have similar minimum power handling requirements.

 I guess what I'm really asking is what this tube amp is meant to drive, since it seems designed for neither larger bookshelves, nor for headphones. Is it really only meant for smaller bookshelves, or am I missing the point completely?


 BPRJam


----------



## aerius

As long as your speakers are decently efficient (>87dB/W) and have a harmless impedance curve that stays around 8 Ohms or so you'll be fine. My family has full range floorstanding speakers that are rated at 88dB/W with a nominal 8 Ohm impedance, and the amp was able to drive them just fine even before I started modding it. It won't play _Metallica_ loud enough for the police to come bust down my door and drag me off, but I'll damage my hearing if I listen that loud for more than a couple songs anyways.

 After the mods it doesn't play any louder, it just sounds better. The Alps pot fixed up the channel imbalance at low volumes, and the capacitor mods give it a bit more bass and speed. After the mods I have the volume knob set to about 10-11 o'clock for my preferred listening volume, and I crank it up a bit if I feel like headbanging to metal. It should be noted that there's absolutely no hum or buzz at all from the speakers when using this amp, it's dead quiet.

 And when I use it as a headphone amp, I use an adaptor thingy that drops the output a lot so I don't blow out my 'phones.


----------



## Wodgy

8 watts is plenty to drive many large speakers. This amp can drive my PSB Century 500is to loud levels without breaking a sweat.

 Speaker manufacturers advertise "Minimum Power" ratings because they want to avoid someone running their speakers into clipping with underpowered solid state gear. When overdriven, solid state gear clips violently and can damage tweeters. Tube gear clips gently when overdriven and generally doesn't risk speaker damage.


----------



## BPRJam

Quote:


 Speaker manufacturers advertise "Minimum Power" ratings because they want to avoid someone running their speakers into clipping with underpowered solid state gear. When overdriven, solid state gear clips violently and can damage tweeters. Tube gear clips gently when overdriven and generally doesn't risk speaker damage. 
 

This was my main concern. I'm pretty familiar with solid state electronics, but not tube technology. I was not aware that tubes "clip gently". Maybe I'll get this amp and do some electrical tests to see what it does when it is overdriven.

 Thanks for the input!


 BPRJam


----------



## MERTON

so is this amp safe for my ms2's? oh.. and can you just plop any ole tube set in there you want?


----------



## Todd R

Quote:


 _Originally posted by Gariver _
*Aerius: I understand. So how about the internet? You can do a Google.com search for "schematic symbols." Here's one site I found...

http://webhome.idirect.com/~jadams/e...nics/schem.htm * 
 

This is the kind of page I have been looking for except for one thing..........
 I need this kind of information for tubes. Where can I find the schematics for tubes, so I know which symbol is what?


----------



## ofb

Quote:


 _Originally posted by Todd R _ Where can I find the schematics for tubes, so I know which symbol is what? [/B] 
 

 like this?


----------



## Todd R

Quote:


 _Originally posted by ofb _
*like this? * 
 

Sort of........
 I was actually wondering about the meanings of the symbols on a tube schematic.

 Like this:
	

	
	
		
		

		
		
	


	



 What are "A" "G" "f,k" pointing to? What do those symbols stand for?


----------



## 10SNE1

a: Anode or plate
 g: grid 
 f,k: heater/cathode

An Introduction to Vacuum Tube audio electronics


----------



## Todd R

Quote:


 _Originally posted by 10SNE1 _
*a: Anode or plate
 g: grid 
 f,k: heater/cathode

An Introduction to Vacuum Tube audio electronics * 
 

Thanks a lot, that's what I was looking for.


----------



## Onix

Quote:


 _Originally posted by aerius _
*And when I use it as a headphone amp, I use an adaptor thingy that drops the output a lot so I don't blow out my 'phones. * 
 

Hey aerius, what's that "adaptor thingy?". Care to elaborate on that please? Thanks.


----------



## aerius

Quote:


 _Originally posted by Onix _
*Hey aerius, what's that "adaptor thingy?". Care to elaborate on that please? Thanks. * 
 

One of these things. Of course mine is a complete hack job and has different resistor values as well as being unshielded. It also looks quite ugly but it works and sounds good.

 I've also just gotten another set of tubes off ebay and they're burning in right now. Nothing special so far but I'll give them a while longer to settle in.


----------



## Onix

Quote:


 _Originally posted by aerius _
*One of these things. Of course mine is a complete hack job and has different resistor values as well as being unshielded. It also looks quite ugly but it works and sounds good.

 I've also just gotten another set of tubes off ebay and they're burning in right now. Nothing special so far but I'll give them a while longer to settle in. * 
 

Yep, I've seen it before. Thank you. But I am wondering how you can translate that to RCA outs instead of those plugs. And, how do you like this amps as a heaphone driver compared to the Gilmore? Is it more euophonic than detailed perhaps?


----------



## brschmid

Quote:


 I also learned that 3000uf at ~200V will vaporize test probes with a blinding flash and deafening bang 
 

i did that with my 1 fared cap for my car stereo and a screwdriver. i jumped about 3 feet and teh screwdriver has a nice scar( divot??)


----------



## Halide

I'm interested in this kit...my dad has some new speakers that are 91 dB sensitivity, full range (no subwoofer) 
 He thinks it probably isn't very good since it's cheap. Right now he has a pretty old Sony "ES" series receiver that doesn't have preouts... I'm pretty sure this amp would probably sound better than the sony receiver, but what do you think?


----------



## Wodgy

For what it's worth, I prefer the sound of this amp to my NAD C320BEE, so who knows, it may sound better than your Sony ES receiver. It almost certainly sounds better than regular (non-ES) Sonys, given the right speakers. (I've owned one of those cheezy non-ES Sony receivers and it sounded terrible.)

 The parts in this amp aren't particularly cheap, even though the overall price is very inexpensive. You're just not paying for extras like an LCD display, remote control, digital volume knob, etc. In fact I'd venture that the amp section of the Sony contains a couple LM integrated amp ICs and a basic op-amp gain stage, and that all the parts in the amp section cost less than the parts used in this amp kit.

 It's a nice kit. Not high end but way better than cheap solid-state gear. The print review of this amp in AudioXPress is worth checking out; the reviewers liked it a lot.


----------



## aerius

Quote:


 _Originally posted by Onix _
*Yep, I've seen it before. Thank you. But I am wondering how you can translate that to RCA outs instead of those plugs. And, how do you like this amps as a heaphone driver compared to the Gilmore? Is it more euophonic than detailed perhaps? * 
 

Hmmm...I'm not sure how I'd convert the output to RCA outs. I'm guessing a variation of the headphone adaptor where each channel gets hooked to it's own RCA jack might work, but I'm not sure at all.

 Soundwise the 2 amps are hard to tell apart on most of my CDs given my craptacular source. The tube amp does female vocals a bit nicer and has a wider and more spacious soundstage, while the Gilmore seems to go down a tad deeper in the bass. Everything else seems pretty much the same. I'll have a better idea of how they measure up after the 20th when I hook both of them up to better sources at the Toronto Head-fi meet.

  Quote:


 _Originally posted by Halide _
*I'm interested in this kit...my dad has some new speakers that are 91 dB sensitivity, full range (no subwoofer) 
 He thinks it probably isn't very good since it's cheap. Right now he has a pretty old Sony "ES" series receiver that doesn't have preouts... I'm pretty sure this amp would probably sound better than the sony receiver, but what do you think? * 
 

I'm not familiar at all with Sony's receivers so it's hard for me to say. I can only compare it to my family's 70's vintage Telefunken 7050 receiver and 8 Ohm 88dB sensitive Braun speakers. That receiver was worth well over $1000 in 1970's money according to my dad. The tube amp (*after* my extensive mods) can match or beat it in soundstaging, detail and midrange & treble goodness, but it loses out in everthing else. It doesn't have the same dynamics, it can't play as loud (8W vs. 50W), bass doesn't go down as deep, and sharp sounds like hard snaredrum "thwacks" don't have quite as much impact. I'd have to say that my Senn 580s with the Gilmore amp sounds quite a bit like the Telefunken/Braun system. I'm not sure if that'll help with forming an idea of how my stuff sounds.

 It still sounds pretty good but it's not as good driving my speakers as it is driving my Senn 580 headphones.

 Latest update, new tubes and swapping all the caps in the signal path. Got a set of tubes off ebay and burned them in. They have the same sound balance and everything as the Sylvanias but with a bit more detail to them. I think I'm done with swapping tubes. In a quest for more bass, I swapped out the .22uF input caps and went to 1uF ones, and changed the .22uF coupling caps to .47uF ones. There's now only 2 songs in my entire CD collection where the Gilmore's bass is better, there were about 5 songs I knew of before this latest cap mod. The 1uF caps are generic film caps while the .47uF ones are Wima caps. Other than the slightly improved bass I haven't noticed any other changes in the sound.

 I also switched the tube heaters back to AC after getting myself an isolation transformer from the local surplus store, and I wired a switch in so I can shut off the high voltage section of the tubes while keeping the tube heaters on. I think I'm done playing with it so my next step will be to make a case for it. That will have to wait till my exams are over.


----------



## Halide

Quote:


 _Originally posted by aerius _
 I'm not familiar at all with Sony's receivers so it's hard for me to say. I can only compare it to my family's 70's vintage Telefunken 7050 receiver and 8 Ohm 88dB sensitive Braun speakers. That receiver was worth well over $1000 in 1970's money according to my dad. The tube amp (*after* my extensive mods) can match or beat it in soundstaging, detail and midrange & treble goodness, but it loses out in everthing else. It doesn't have the same dynamics, it can't play as loud (8W vs. 50W), bass doesn't go down as deep, and sharp sounds like hard snaredrum "thwacks" don't have quite as much impact. I'd have to say that my Senn 580s with the Gilmore amp sounds quite a bit like the Telefunken/Braun system. I'm not sure if that'll help with forming an idea of how my stuff sounds.

 It still sounds pretty good but it's not as good driving my speakers as it is driving my Senn 580 headphones. 
 

I think this would definately be worth the cost just for the fun of building it, then 
	

	
	
		
		

		
			





  Quote:


 _Originally posted by aerius _
 Latest update, new tubes and swapping all the caps in the signal path. Got a set of tubes off ebay and burned them in. They have the same sound balance and everything as the Sylvanias but with a bit more detail to them. I think I'm done with swapping tubes. In a quest for more bass, I swapped out the .22uF input caps and went to 1uF ones, and changed the .22uF coupling caps to .47uF ones. There's now only 2 songs in my entire CD collection where the Gilmore's bass is better, there were about 5 songs I knew of before this latest cap mod. The 1uF caps are generic film caps while the .47uF ones are Wima caps. Other than the slightly improved bass I haven't noticed any other changes in the sound. 
 

What mods would you suggest I order before assembling the kit? Just those 2 cap upgrades?

  Quote:


 _Originally posted by aerius _
 I also switched the tube heaters back to AC after getting myself an isolation transformer from the local surplus store, and I wired a switch in so I can shut off the high voltage section of the tubes while keeping the tube heaters on. I think I'm done playing with it so my next step will be to make a case for it. That will have to wait till my exams are over. 
 

I don't plan on buying their case, so if you have any inexpensive ideas let us know


----------



## aerius

Quote:


 _Originally posted by Halide _*What mods would you suggest I order before assembling the kit? Just those 2 cap upgrades? * 
 

Hmm...that's a tough call. I think upgrading to the Alps Blue pot gave me the biggest single improvement. The power supply and signal path cap upgrades are kinda hard to judge for me due to the order in which I upgraded stuff. My first upgrade was to change the signal path caps from generic film caps to Wimas, then I did the pot upgrade, followed by the power supply caps. I also built mine up with 1% metal film resistors from the very start so I don't know how it sounds with the original 5% ones.

 I'd say do the pot upgrade and swap all the generic signal path film caps to Wima caps of the same value and then double the value of all the electrolytic caps. That takes care of most of the improvements to be had and everything else (other than tuberolling) is just fine tuning and squeezing out every last bit of performance.


----------



## aerius

After hearing how the amp sounded at the Toronto Head-fi meet I came to a few conclusions.

 1) A low-end Panasonic CD/DVD player is not a good enough source for evaluating amps.

 2) There's some harshness in the treble and a couple other things that need work.

 3) The only way left that might improve things is to mod it into triode mode.

 The source problem was solved by borrowing a nice Naim CDP from a co-worker who was going away for the holidays. I spent a couple days familiarizing myself with the player and then I followed the Headwize instructions for modding the amp to run as a triode.

 It's probably the single largest improvement I've gotten from any of the mods I've done to date, but there's a compromise. The bass doesn't go down quite as deep anymore and deep bass tones won't vibrate my headphones (and head) as much. This is clearly noticeable on Sarah McLachlan's "I Love You" and "Liquid Diamonds" by Tori Amos.

 Now, to the good parts. The midrange has filled in a bit and the sound is more solid and has more weight to it even though the bass doesn't go as low. Drums sound so much nicer now, I'm having an all day Led Zeppelin session right now just because of how much I'm enjoying John Bonham wailing away on his drum kit. Instrument placement is better & more stable, and the separation between instruments seems to be as well. It's hard to explain but everything just sounds more "right". It's going to be some time before I get full impression of it, I'm trying to listen to as much music as I can before I have to give the Naim CDP back.

 The gain is dropped a bunch so I can open up the volume knob a lot more and it's easier to set the volume level. If you're using this amp with speakers you probably won't have enough gain left to drive them unless you have really sensitive speakers.


----------



## ixeo

anybody figured to get this to work with 220V-240V AC? looks like a really great beginner tube amplifier... which is exactly what i need 
	

	
	
		
		

		
		
	


	




 edit: without using a step down transformer that is


----------



## flecom

Quote:


  Originally Posted by *Wodgy* 
_In fact I'd venture that the amp section of the Sony contains a couple LM integrated amp ICs and a basic op-amp gain stage, and that all the parts in the amp section cost less than the parts used in this amp kit._

 

you would be suprised what you can do with those cheap parts, google "gainclone" if you dont believe me


----------



## pho_boi

very very interested in purchasing one. has anyone else listened to this amp? and would you say this amp is like a cmoy to a pimeta in the tube world?


----------



## brschmid

Quote:


  Originally Posted by *pho_boi* 
_very very interested in purchasing one. has anyone else listened to this amp? and would you say this amp is like a cmoy to a pimeta in the tube world?_

 


 says so in the first post. 

 and this amp is for speakers i do believe, not head phones.


----------



## ilikemonkeys

I just got mine in the mail. I haven't opened it yet.

 I have no idea how to read schematics....wish me luck!

 BILL


----------



## ilikemonkeys

I just built it.

 Followed the instructions.

 Tubes light up.

 No sound.

 Nothing....nada....

 I wanna play with my new toy!

 Anyone care to suggest how to troubleshoot this?

 BILL


----------



## aerius

1) make sure you put all the parts in the right place
 2) make sure everything is connected properly
 3) make sure the CD player or source is working & playing
 4) wait 15-30 seconds after turning the amp on for the tubes to warm up. You won't get sound with cold tubes.


----------



## Wodgy

Nothing in either channel?

 Do you have a voltmeter?

 First thing to do is visually double check that all the solder joints are good. They should be shiny and smooth, not cloudy and rough.

 Whatever you do, be sure to observe basic safety precautions. This is a relatively safe amp (~175v B+ instead of 300v or more), but all high voltages can easily be deadly. Here's a good page to familiarize yourself with safety precautions:
http://www.bottlehead.com/loosep/Safety.htm


----------



## Sovkiller

I'm getting it right, or you are saying that an amp with around 1% of THD at 1 watt sounds good???? Is not that value a little too high for such an small amp, IMO this is a terrific bad figure on the THD at least, 1% at 1Watt is IMO unacceptable for any amp nowadays...but who knows maybe it sounds good even though...?????


----------



## Wodgy

If you're a solid state guy, anything above 0.02% THD at 1kHz is probably unacceptable to you. That's fine. Some of us prefer to listen. 1% THD for a tube amp at 1w is par for the course for many low powered tube amps. I've said it many times before: this cheap kit amp outperforms the NAD C320BEE, which has far better advertised specs. I no longer own the C320BEE, but I still own this amp.

 For anyone interested in an independent review of this amp's sound quality, check out the review on the AudioXPress website.


----------



## Sovkiller

Quote:


  Originally Posted by *Wodgy* 
_If you're a solid state guy, anything above 0.02% THD at 1kHz is probably unacceptable to you. That's fine. Some of us prefer to listen. 1% THD for a tube amp at 1w is par for the course for many low powered tube amps. I've said it many times before: this cheap kit amp outperforms the NAD C320BEE, which has far better advertised specs. I no longer own the C320BEE, but I still own this amp.

 For anyone interested in an independent review of this amp's sound quality, check out the review on the AudioXPress website._

 

Well I'm confused now, is the tube amps THD so different form the SS ones? Or distortion is just that THD distortion??? It may sound good, but at the end the distortion is still there....or am I wrong??? Which are the main differences between both cases, tubes and SS?

 OTOH I'm not familiar wit hthat NAD as many members here, and maybe the NAD is not so good amp at the end. BTW distortion is not the only parameter to consider in an amp, and even though, IMO after good parameters, the ear is the finest instrument at the end...I have seen a lot of good amps (in specs) to sound terrible....But is this one of the cases of the opposite?...IMO for 139.00 I think that you could get a much better SS comercial used amp (or evne new) if choosen wisely, honestly....unless you were looking absolutelly for a tube amp....


----------



## Sean H

Sorry. EDIT


----------



## aerius

Quote:


  Originally Posted by *Sovkiller* 
_IMO for 139.00 I think that you could get a much better SS comercial used amp (or evne new) if choosen wisely, honestly....unless you were looking absolutelly for a tube amp...._

 

I'll leave the technical details for someone else to explain since I'm not as clear on them as I'd like to be.

 However, I'd say that unless you have speakers which are pretty inefficient or have a low impedance, it would be very hard to find an amp for $139 that can match this one. Entry level Sonys, Pioneers, etc. don't even come close, and it takes a used midrange Rotel before you start getting anywhere. The only amp I know of in the price range that can match or beat it is the Teac Tripath amp which retails for $99 IIRC, and it still needs a preamp for volume control.


----------



## Wodgy

Quote:


  Originally Posted by *Sovkiller* 
_Well I'm confused now, is the tube amps THD so different form the SS ones? Or distortion is just that THD distortion??? It may sound good, but at the end the distortion is still there....or am I wrong??? Which are the main differences between both cases, tubes and SS?_

 

I don't really know why you're choosing this thread to bring up the age-old tubes versus solid state debate. (I'm assuming you're asking the question in earnest, not trying to thread crap.) Briefly: tubes tend to generate a clean, natural distortion profile (2nd harmonic > 3rd > 4rd > 5th, etc.). Single ended triodes with no feedback in particular have a beautiful distortion profile, with virtually no higher order harmonics. Push-pull pentodes compromise this somewhat in order to achieve more power (and often lower total distortion levels). Solid state amps tend to generate an unnatural distortion profile, dominated by odd harmonics as well as higher-order harmonics. Even at very small levels, the ear finds higher order harmonics irritating. We can't hear very large levels (~8%) of 2nd harmonic distortion at all, but we can easily hear very small levels of 5th harmonic distortion. That's just how our ears work.

 I'm not interested in starting an engineering debate about whether tubes are colored or not. That's something for another thread, which should go in the amps forum. In fact, there was a recent thread about this.

  Quote:


 I have seen a lot of good amps (in specs) to sound terrible.... 
 

That's right. I agree with you there.

  Quote:


 IMO for 139.00 I think that you could get a much better SS comercial used amp (or evne new) if choosen wisely 
 

Perhaps, but it wouldn't have the tube sound. Depends on your taste in sound. For $139 you'd be able to afford one of the older NAD models on eBay (not recommended, personally), a Pioneer A-35R (good for the price, not great, but not bad), or one of the vintage Marantz (best option). None of these get you the tube sound, but they do get you a decent amp.

 However, I doubt that if you were planning on doing that you'd be hanging around the DIY forum, which tends to appeal to people interested in building DIY amps, of which this kit is a good starter point. There are a couple of people over at diyAudio who are now regulars in the Tube forum who started out building one of these kits.


----------



## ilikemonkeys

when I turn the colume up high I can hear the music in the tubes, but not through thte speakers.

 The solder joints are good. All the tubes light up and get real warm real quick.

 I have to admitt that I am a bit confused by step #5

  Quote:


 Solder each black wire to sircut board to the pads between the output transformers and secondary pads. 
 

I think I did this correctly.

 Positive really.

 I'm lost.

 And no, I don't have a voltmeter.

 BILL


----------



## Sovkiller

Quote:


  Originally Posted by *Wodgy* 
_I don't really know why you're choosing this thread to bring up the age-old tubes versus solid state debate. (I'm assuming you're asking the question in earnest, not trying to thread crap.) Briefly: tubes tend to generate a clean, natural distortion profile (2nd harmonic > 3rd > 4rd > 5th, etc.). Single ended triodes with no feedback in particular have a beautiful distortion profile, with virtually no higher order harmonics. Push-pull pentodes compromise this somewhat in order to achieve more power (and often lower total distortion levels). Solid state amps tend to generate an unnatural distortion profile, dominated by odd harmonics as well as higher-order harmonics. Even at very small levels, the ear finds higher order harmonics irritating. We can't hear very large levels (~8%) of 2nd harmonic distortion at all, but we can easily hear very small levels of 5th harmonic distortion. That's just how our ears work.

 I'm not interested in starting an engineering debate about whether tubes are colored or not. That's something for another thread, which should go in the amps forum. In fact, there was a recent thread about this.



 That's right. I agree with you there.



 Perhaps, but it wouldn't have the tube sound. Depends on your taste in sound. For $139 you'd be able to afford one of the older NAD models on eBay (not recommended, personally), a Pioneer A-35R (good for the price, not great, but not bad), or one of the vintage Marantz (best option). None of these get you the tube sound, but they do get you a decent amp.

 However, I doubt that if you were planning on doing that you'd be hanging around the DIY forum, which tends to appeal to people interested in building DIY amps, of which this kit is a good starter point. There are a couple of people over at diyAudio who are now regulars in the Tube forum who started out building one of these kits._

 

I was not trying to thread crap honestly Wodgy, and thanks for the reply, I was just browsing the new threads of the day, and this comes as one of the firsts, and I was curious, thinking that it was a headphone amp, as I have a friend that is looking for one headphone amp and he is a tube lover, so I got into it, and later looking at the numbers I saw that odd number for the THD and I was curious, just that....

 BTW there are another options for SS amps, a lot more for around that price used, even those legendary Pioneer, Technics, Sansui, vintage amps, but as you say it is not the purpose of this thread, so I will leave the tube nuts with that amp now...LOL...


----------



## ilikemonkeys

I figured it out!

 The banana plugs are too shielded with the rubber washers in place. I thought they were tight enough to fit.....THey were not. A little solder fixed that.

 THanks for the ear Head-fi.

 B


----------



## Sean H

Sorry. EDIT


----------



## ilikemonkeys

I love this amp!

 B


----------



## blackie

just check the schematic on this little guy and i must say there is some def koolness there. direct coupled front end! nice. i'm a fan.

 didn't have time to read all the posts, so some if not all of this has surely been mentioned b4 but if i was building this guy...on the cheap...i would...in this order of importance...if anyone gives a rat's axx...

 omit c1 and c4. unnecessary

 cut trace to pins 7 of all power tubes and strap a 100 ohm wirewound resistor between pins 6 and 7 of each power tube. REMOVE R5 feedback resistor...yuck

 replace diodes with leetle hexfreds or if you are a real cheepskate bypass diodes with some high voltage ceramic caps. kindas yucky but still better than plain ol diodes and cheep

 better quality anything, starting with plate load resistors and ps caps, which to me means...in this case...probably...carbon film resistors, panasonic tshb electrolytics, polypropylene film non-metalized coupling caps like orange drops. cheap good stuff.

 re: bypassing ps caps or increasing values...i am NOT a fan. better you should increase quality and reduce value of ps caps. but since this ps lacks a choke you may get more noise from smaller caps, so...cut and try, cut and try.

 keep 'em heated, ninjas

 -blackie.


----------



## Wodgy

Quote:


  Originally Posted by *blackie* 
_just check the schematic on this little guy and i must say there is some def koolness there. direct coupled front end! nice. i'm a fan.

 didn't have time to read all the posts, so some if not all of this has surely been mentioned b4 but if i was building this guy...on the cheap...i would...in this order of importance...if anyone gives a rat's axx...

 omit c1 and c4. unnecessary

 cut trace to pins 7 of all power tubes and strap a 100 ohm wirewound resistor between pins 6 and 7 of each power tube. REMOVE R5 feedback resistor...yuck

 replace diodes with leetle hexfreds or if you are a real cheepskate bypass diodes with some high voltage ceramic caps. kindas yucky but still better than plain ol diodes and cheep

 better quality anything, starting with plate load resistors and ps caps, which to me means...in this case...probably...carbon film resistors, panasonic tshb electrolytics, polypropylene film non-metalized coupling caps like orange drops. cheap good stuff.

 re: bypassing ps caps or increasing values...i am NOT a fan. better you should increase quality and reduce value of ps caps. but since this ps lacks a choke you may get more noise from smaller caps, so...cut and try, cut and try._

 

Good suggestions. People should be aware that the triode conversion you suggest will drop the amp's output to about 3 watts, but as long as people are aware of that it's a worthwhile mod to try.

 Voltsecond also has a great page with mods to this kit:
http://www.siteswithstyle.com/VoltSe...Push_Pull.html
 Apparently newer versions of the kit PCB already have many of these mods incorporated, so check before proceeding.


----------



## blackie

yes indeedy, power output, one of the most insignificant specs in all ampdom, will be cut in half.

 contrary to popular belief, thanks to the shameless marketing people in the audio industry, this is not the same as having your manhood cut in half.

 the removal of that feedback resistor and those pentode screens, which is made possible by triode conversion, will improve the sound so dramatically, you will loudly exclaim:

 Power Output Be Damned!


----------



## Wodgy

Blackie, what kind of amp do you use at home? Are you a SET guy or a push-pull triode guy?


----------



## blackie

i am an everything guy.

 i basically design with the application in mind. i subscribe to no dogmas. just use my ears and work with the specific case.

 i believe in no limits. physics...maybe.

 with this nice little amp, triode mode into headphones will make your ears very happy. maybe. your mileage may vary.

 audio is very subjective. you like what you like 
	

	
	
		
		

		
			





 -blackie.


----------



## aerius

Quote:


  Originally Posted by *blackie* 
_omit c1 and c4. unnecessary_

 

Definitely, when I got rid of them the sound was noticeably better, not revolutionary or anything, but it was noticeable.

  Quote:


 replace diodes with leetle hexfreds or if you are a real cheepskate bypass diodes with some high voltage ceramic caps. kindas yucky but still better than plain ol diodes and cheep 
 

I forgot to mention this one, it really does work. It got rid of an annoying buzzing noise (my headphones are now directly connected to the output instead of going through resistors to drop things down) and turned it into a soft harmless background hiss. I used hexfreds on my amp.

  Quote:


 re: bypassing ps caps or increasing values...i am NOT a fan. better you should increase quality and reduce value of ps caps. but since this ps lacks a choke you may get more noise from smaller caps, so...cut and try, cut and try. 
 

I did end up working a choke into the power supply, and also replaced the 22uF electrolytic with a 20uF film cap I found in the local surplus store. That got rid of a bit more noise & might've made the sound a bit better.


----------



## ilikemonkeys

so just jumper the c1 and c4, or snip them off completely?


----------



## blackie

if you want revolutionary, you'll have to go for the open-loop triode conversion. that change will be revolutionary indeed but you will have to lose 40 years of hype from your brain. not your fault. it's been sold as fact by dudes who wanted everyone to buy new stuff. maybe they believed it themselves.

 simply remove the unnecessary caps and replace them with wire.

 depending on source impedance they are probably large enough to not restrict the low frequency response, but they are pretty dang pointless...and they are in series with your whole source...ew.

 chopper building 101. remove all superflous chrome prior to radical performance mods hehe


----------



## ilikemonkeys

any suggestions on how to not SSHHOOCCKK myself again?

 other than unplugging it?

 BILL


----------



## blackie

hahaha welcome to the wonderful world of high voltage electronics. cowboy up, fella, you only took 175v.

 i took 660AC once and had to be hospitalized. couldn't breathe.

 i find it enhances your mood temporarily.


----------



## ilikemonkeys

I just did it. There is a considerable difference. Is it me, or is it louder now?

 I think I'm gonna buy another and monoblock them. I can, can't i?

 B


----------



## blackie

it's louder. open loop...no negative feedback. did you tie the plate and screen w/ 100 ohms?


----------



## ilikemonkeys

Quote:


 did you tie the plate and screen w/ 100 ohms? 
 

huh?

 edit to add: I'm a microbiologist.


----------



## blackie

do the pin 6/pin 7/ 100 ohm resistor remove r5 thingie i mentioned in prev post and report back to me soldier!

 oh yes and turn it off first...maybe ven rain the caps if you have kids or somthing heheh


----------



## gavinbirss

Hello, 

 The kit looked good so I did some googling on it and found the following : http://www.siteswithstyle.com/VoltSe...Push_Pull.html 

 Enjoy ...


----------



## gavinbirss

Dam looks like my text search did not reveal that I Woody already posted this link. 

 Sorry.

 Gavin


----------



## bg4533

I just got my amp put together. I have mixed opinions of it so far, but it might have some problems too. Compared to my Denon AVR1200 the highs seem a bit rolled and bass is not as impactful. Compared to my Pimeta and HD650s well...it sucks. The midrange on the amp seems very nice though. 

 My first problem is that with the volume all the way up or all the way down I get a bit of radio playing through the speakers.

 Problem 2 is a bit of hiss through the amp. Mainly through the tweeters. With a set of old speakers it isn't much, but with my Mission M73s it is significant.

 Also, is it normal for a bit of the music to play through the tubes?

 I have some MUR860s here, can I replace the rectifier with them?

 Eventually I want to take out the volume control and use a PPA as a preamp. I am placing an order with Mouser and will order some Vishay RN60s to replace most of the resistors with.


----------



## ilikemonkeys

I get no radio playing from mine, and I live next to a tower. I get radio in my electric razor. THe bass is not impactful, but I have noticed did get much much better over time. The modifications I made offered a dramatic improvement in static, although i really never heard much to begin with.

 Good luck. I love this little amp. Its really all I ever use anymore. Its just so easy to play with.

 BILL


----------



## Wodgy

Quote:


  Originally Posted by *bg4533* 
_I just got my amp put together. I have mixed opinions of it so far, but it might have some problems too. Compared to my Denon AVR1200 the highs seem a bit rolled and bass is not as impactful. Compared to my Pimeta and HD650s well...it sucks. The midrange on the amp seems very nice though._

 

It is definitely a different sound. I personally don't really like the PIMETA with many headphones, though it is a very nice combo with the Senns, because of the slightly aggressive presentation. This tube amp has more of a laid back presentation, but with an organic midrange. I agree with you on the bass impact comment, though to some extent that is relative. I would rate it on par with one of the digiamps that are now popular, but not as good as a NAD C370.

  Quote:


 My first problem is that with the volume all the way up or all the way down I get a bit of radio playing through the speakers. 
 

I didn't notice this on mine, but try replacing the stock 100k potentiometer with a 10k pot, e.g. one of the low cost Panasonics. Lower impedance pots are less prone to interference.

  Quote:


 Also, is it normal for a bit of the music to play through the tubes? 
 

If you're hearing music emanating from the amp, it's coming from the output transformers. All tube power amps do this, though it should be very quiet.

  Quote:


 Eventually I want to take out the volume control and use a PPA as a preamp. I am placing an order with Mouser and will order some Vishay RN60s to replace most of the resistors with. 
 

The preamp idea will work well. My amp is in storage right now, so I can't check, but if there are carbon or carbon film resistors I wouldn't replace them with metal film types. It could change the voicing of the amp and remove some of the warmth. That might be what you're looking for though.


----------



## aerius

Latest update. Scored some polypropylene film & foil capacitors on ebay and replaced the Wima caps I had before. Marginal improvement if any, treble might be a tiny bit clearer but it's hard to tell.

 Then seeing how getting rid of the small 22uf electrolytic capacitor in the power supply helped with noise, I thought to myself, what if I got rid of all the electrolytics and replaced them with film caps? Problem, I had to find some large film caps. So I went to check out the local surplus stores and found these things called motor run capacitors, and I did some research on them and found out they were actually large film caps. Bingo! I bought a few of them and stuck them into the power supply.

 Result? Whoa, well, I got a lot more than I expected. Besides getting rid of almost every last bit of noise, the amp is now noticeably faster and more detailed, especially in the bass & lower midrange. Piano & electric bass notes which used to blend together are now distinct & separate, and I'm hearing details & textures in the bass which I've never heard before. I'd say the difference is almost as big as going from the Senn 600 to the 650 on a PPA, Gilmore Lite, or the previous version of my tube amp.

 Note. These capacitors are _huge_, each of them is size of a beercan and I'm using 4 of them. They have to be mounted off the board.


----------



## bhd812

how easy and safe is this kit for a beginner?

 I am good at soding but I have never built a amp before


----------



## Syzygies

Quote:


  Originally Posted by *bhd812* 
_how easy and safe is this kit for a beginner?
 I am good at soding but I have never built a amp before_

 

From their web page:

_1. This project deals with lethal 115V line voltage and higher voltages_

 Build a PIMETA. You'll love it. When you no longer need to ask the above question, you're ready to work with such voltages. It's more than conceptually understanding what to do; this hobby keeps you up till dawn sometimes, which is when people make mistakes.

 I met someone recently (he noticed my amp on a plane) who works on vintage tube guitar amps. He talks about it like he was keeping a wild cat at home. Like, go to India and practice eating with one hand, before even thinking of handling such voltages. He _doesn't_ work on his amps tired.


----------



## Wodgy

This is as safe as kits get for a beginner. It's much safer than an equivalent kit from Bottlehead.

 Don't bother with a PIMETA; it just doesn't sound anywhere near as good. I've built both.


----------



## bhd812

I ordered one..hehe you headfi people

 I was going to order a jolida 102 today but I am in my cheap mood, well I will let you know it turns out.


----------



## strogg

Quote:


  Originally Posted by *aerius* 
_Then seeing how getting rid of the small 22uf electrolytic capacitor in the power supply helped with noise, I thought to myself, what if I got rid of all the electrolytics and replaced them with film caps? Problem, I had to find some large film caps. So I went to check out the local surplus stores and found these things called motor run capacitors, and I did some research on them and found out they were actually large film caps. Bingo! I bought a few of them and stuck them into the power supply.

 Result? Whoa, well, I got a lot more than I expected. Besides getting rid of almost every last bit of noise, the amp is now noticeably faster and more detailed, especially in the bass & lower midrange. Piano & electric bass notes which used to blend together are now distinct & separate, and I'm hearing details & textures in the bass which I've never heard before. I'd say the difference is almost as big as going from the Senn 600 to the 650 on a PPA, Gilmore Lite, or the previous version of my tube amp._

 

what values did you get? any more details on this you can shed? 

 anyway, an update for me!!:

 first, i replaced the tubes with ge tubes from ebay. well, they made a noticeable change. change to the good, i don't know. but i think i hear more detail (which is head-fi speak for it probably didn't do anythign).

 next
 i replaced all the resistors with vishay's (except for 4 koa spears since mouser didn't have vishay's with that particular value). i also replaced the 4 film caps with wima polyfilm. i then added the cap across the hv line and the 6 snubber caps for the filament line (both suggested by the siteswithstyle site). i also put a uf4007 on the dc+ line right after the bridge rectifier (i was too cheap to replace the whole bridge). 

 anyway, the sound was... much much much different afterwards. it lost the warm fuzzy feeling. i now have an amp that sounds much more forward, much more detailed. the mids are starting to lack a little, but the highs are strong and hard without any noise. the lows are... different. i'm not sure if it's better or not, but it's just different for now. The biggest difference i hear, though, is the soundstage. the soundstage for my k501's completely changed. with almost every source/amp i've tried the k501's on, i always hear the sound coming from behind me, like at the back of my head. now, it's froming from almost in FRONT. the vocals, though, come from front and up, like from my forehead. i don't know why, but it does. it's really weird. i believe the component upgrade has to be the absolute best $20 i've ever spent on this amp. 

 so the following is the list of mods i personally did:
 pentode->triode
 replace resistors with vishay dale mil grade
 remove c1 and c4
 replaced film caps with wima polyfilms
 add a 5 ohm across both output signals (required, really)
 doubled electrolytic cap values and put .33uf caps across those
 put a .01uf monolithic cap across hv
 put 6 1uf caps across the filament line
 replace volume pot with stepped attenuator (with vishay dale rn60d's)
 replaced tubes with ge tubes
 shielded output and power transformers
 put ultrafast uf4007 diode on dc+
 emi filter on power line (i don't know if that does anything at all)


----------



## aerius

Quote:


  Originally Posted by *strogg* 
_what values did you get? any more details on this you can shed?_

 

Kinda hard to describe since my power supply doesn't look _anything_ like the stock one. The power supply is completely off-board, though it does connect into the board where the electrolytic capacitors used to go.






 It's basically as pictured in the rough sketch I did above, it's been 5 years since I've taken an electronics course so I hope I drew everything right. The power comes off the rectifier and goes in from the left. The point marked (1) is where it connects into where the 220uF cap used to go, (2) is where it connects to where the 100uF cap was, and (3) is the connection for where the 22uF cap was in the original. The 2.2k resistor is already part of the board so you don't need to worry about that. The 2H choke between (1) & (2) replaces the 470 ohm resistor (R18) on the original. As I mentioned, they're all 240V(AC) motor run polypropylene film capacitors, and they are huge.

 One of these days I need to sit down and write out everything I've done to my kit.


----------



## strogg

Quote:


  Originally Posted by *aerius* 
_One of these days I need to sit down and write out everything I've done to my kit._

 

that'll probably take you a couple months
	

	
	
		
		

		
		
	


	




 but yeah, although the schematic could improve, i understand exactly what you're saying (somehow!). thanks
	

	
	
		
		

		
		
	


	




 ps: if i do what you do, this is what my power supply would look like: 






 just to make things clearer. tell me if i goofed somewhere


----------



## dsavitsk

Quote:


  Originally Posted by *Wodgy* 
_This is as safe as kits get for a beginner. It's much safer than an equivalent kit from Bottlehead.

 Don't bother with a PIMETA; it just doesn't sound anywhere near as good. I've built both._

 

But read this first http://www.diyaudio.com/forums/showt...threadid=30172


----------



## aerius

New & improved drawing of my current power supply and how it connects into the amp.






 The 30uF cap is a direct replacement of the 22uF one, the circled 2H choke replaces the 470 ohm resistor (R18), and the 75uF cap to the right of the circled choke replaces the 100uF cap in the original. Hope that makes things a bit clearer.


----------



## strogg

Quote:


  Originally Posted by *aerius* 
_New & improved drawing of my current power supply and how it connects into the amp.







 The 30uF cap is a direct replacement of the 22uF one, the circled 2H choke replaces the 470 ohm resistor (R18), and the 75uF cap to the right of the circled choke replaces the 100uF cap in the original. Hope that makes things a bit clearer._

 

crystal clear
	

	
	
		
		

		
		
	


	




 so are the 2h inductors the only option? cuz i don't feel like spending $40 on a couple 2h inductors...


----------



## aerius

Quote:


  Originally Posted by *strogg* 
_so are the 2h inductors the only option? cuz i don't feel like spending $40 on a couple 2h inductors..._

 

To be honest, I don't know. I found them for cheap at a local used surplus store so I picked them up and stuck them into the circuit.


----------



## bhd812

she came in today, I havent got a chance yet to turn her up but she sounds soooo nice...I think she may beat out my sonic t amp!

 I am going to give her a good long listen in the mourning and I will report back to you all how she does.

 my gear I am using her with are the following


 Meridian g08>mit term3>the amp in thread>cardas ref speaker cable>norh 6.6 floor standing speakers....

 I love having effecient speakers...my norh's are 93 so haaaaaa!
 wish me good luck, I hope she sound sooo nice tomorrow mourning


----------



## killerfishes

I should get my kit today and my speakers soon 
	

	
	
		
		

		
		
	


	




 All i need now is the bloodwood for the cabinets.


----------



## bhd812

Ok so I had so time with the amp and my speakers..

 first off for the cost I must say if anyone is looking into a cheap small powered tube amp...this is so for you.

 I have spent alot of time with her and usually Thats odd I listen to my speakers over my headphones but I cant turn her off...so nice.

 two probelms in my setup now...

 no low end bass, the amp cant power the norh 6.6 down to low.
 messing with room acoustics to get the norh's low end bass somewhat is not fun....I think I got it where I like it.

 Frank sinatra type music the amp is amazing, any music thats really alot of stuff init then it gets messy.

 I wanna put her in a case now, and of course some mods must be done.


----------



## killerfishes

I got it and its done and looks, and sounds good.
 The one thing i have not seen a how to on this amp is straping it to use it as a mono block
http://www.tubeaudio.com/page23.html
 That link says you can but i dont see where it tells how. any input?


----------



## killerfishes

confused on triode conversion. The old HeadWize page "still in google cache" just says to connect pin 6 and 7. is this right or do i use the 100 ohm resistor.

 I cant belive that it can sound better than it dose. This has got to be the best thing iv done since i got the Stanton 881.


----------



## aerius

Quote:


  Originally Posted by *killerfishes* 
_confused on triode conversion. The old HeadWize page "still in google cache" just says to connect pin 6 and 7. is this right or do i use the 100 ohm resistor._

 

Either way works, just remember to cut the traces going to pin 7 first. Note that this mod is pretty much non-reversible, once the traces are cut that's it. You can't go back to pentode mode without some really creative wiring.


----------



## bhd812

What would this mod do?

 sound quality? more power...I forgot which one does more power.

 if its more power (louder) then I will do it for sure


----------



## aerius

The triode mod impoves sound quality but drops power to something like 3 watts or so. Recommended only if your speakers have an efficiency better than 95dB/W or you're using them to drive headphones.

 The monoblock conversion doubles power, but no one's done it yet and you also need a 2nd kit for the other channel. No idea how it sounds either.


----------



## bhd812

Quote:


  Originally Posted by *aerius* 
_The triode mod impoves sound quality but drops power to something like 3 watts or so. Recommended only if your speakers have an efficiency better than 95dB/W or you're using them to drive headphones.

 The monoblock conversion doubles power, but no one's done it yet and you also need a 2nd kit for the other channel. No idea how it sounds either._

 


 hey now!
 monoblock?
 where do I get the info on doing this mod? Does it double the power in each amp? like 16watts of power in each amp?

 if so I will order a second kit monday...woot woot


----------



## Frank M

Quote:


  Originally Posted by *bhd812* 
_hey now!
 monoblock?
 where do I get the info on doing this mod? Does it double the power in each amp? like 16watts of power in each amp?

 if so I will order a second kit monday...woot woot_

 

In monoblock mode, you use one kit for one channel, and the other for the other channel. Dual mono. But it involves some mods, that noone has done (or at least posted about) so far.


----------



## bhd812

Quote:


  Originally Posted by *Frank M* 
_In monoblock mode, you use one kit for one channel, and the other for the other channel. Dual mono. But it involves some mods, that noone has done (or at least posted about) so far._

 

My question is how do I mod it to be a mono?


----------



## Frank M

Quote:


  Originally Posted by *bhd812* 
_My question is how do I mod it to be a mono?_

 

Well, for that, I have no idea, and i don't even recall seeing any of those... though I have definately read it somewhere in the thread - or maybe it was another tube amp thread... or another forum... 
	

	
	
		
		

		
		
	


	




 I don't know, sorry.


----------



## bhd812

[size=large]*here is how you mono-block the amp*[/size]


 run the rca's and the speaker output's in parallel

 take either a adapter or hard wire one rca input to the two rca's on the amp

 take the positive on both sides connect then to a single positive
 take the negative on both sides connect them to a single negative

 the single neg and the single pos connect your speakers...

 I tried this and it works.
 I ordered another amp, and I am building two cases..
 should be done by the end of this month

 16watts of power baby...woot woot


----------



## killerfishes

Quote:


  Originally Posted by *aerius* 
_Either way works, just remember to cut the traces going to pin 7 first. Note that this mod is pretty much non-reversible, once the traces are cut that's it. You can't go back to pentode mode without some really creative wiring._

 

So what is the advantige of using the resistor Vs. not? I don't need 8W for my speakers I would like to know how, to mono block for a sub, but I may just order a set of tubes and point to point a mono 8w for the sub.


----------



## bhd812

Quote:


  Originally Posted by *killerfishes* 
_So what is the advantige of using the resistor Vs. not? I don't need 8W for my speakers I would like to know how, to mono block for a sub, but I may just order a set of tubes and point to point a mono 8w for the sub._

 


 it helps to look at the post above yours...

  Quote:


  Originally Posted by *bhd812* 
_[size=large]*here is how you mono-block the amp*[/size]


 run the rca's and the speaker output's in parallel

 take either a adapter or hard wire one rca input to the two rca's on the amp

 take the positive on both sides connect then to a single positive
 take the negative on both sides connect them to a single negative

 the single neg and the single pos connect your speakers...

 I tried this and it works.
 I ordered another amp, and I am building two cases..
 should be done by the end of this month

 16watts of power baby...woot woot_


----------



## Zunqiu

Looks good! Any one tried it with HD650 yet?
 Full review?


----------



## Voodoochile

AES sells this kit (Fathauer amp), but they also sell a monoblock kit designed by George... it does use different tubes, but includes twice the iron and is pretty reasonable. Alternative to ASL Waves?

 Search there for K-501 (monoblock) and K-502 (stereo)


----------



## ilikemonkeys

I'm using these with Paradigms and it sounds absolutly fantastic. 

 Could I do the SET mod on this and still use it to drive my Paradigms?

 BILL


----------



## killerfishes

I don't think there is a SET mod.


----------



## bhd812

so i was thinking...

 thats not a real way to mono the amp, its a 5th grader way, or a salesmen way to sell another amp...


 i am happy with what i got now anyway


----------



## killerfishes

Quote:


  Originally Posted by *bhd812* 
_so i was thinking...

 thats not a real way to mono the amp_

 

so im not the only one thinking that.


----------



## bg4533

I am currently trying to sell my already built S5 amp. There is a link with details in my signature. It is less than the price of the kit if you want it.


----------



## killerfishes

Got an E-Mail from the place that says it can be run as a mono block. They said paralleling the in and outputs. then they also told me it can not be run in triode mode


----------



## killerfishes

is there any way to use a tube rectifier for this amp? what would be better direct/inderect heated?


----------



## aerius

Quote:


  Originally Posted by *killerfishes* 
_is there any way to use a tube rectifier for this amp? what would be better direct/inderect heated?_

 

Yes, but you'll have to redesign & rebuild the entire power supply section off-board and I'm pretty sure you'll need a new power transformer as well.


----------



## killerfishes

If some one would look this over for me I would be thankfull
 Tubes == 5u4-g or 274b
 transformer == VA: 176, Secondary RMS: 275-0-275, DC mA: 200, Fil. #1 Rectifier: 5.0V/3A CT, Fil. #2 Heater: 6.3V/6.0A CT.
 R1 == 2.5k ;R2 == 5k
 L1 == 15H, 411Ohm
 C1 == 80uF ;C2 == 220uF


----------



## nikongod

weeee.

 i ordered my kit, and it came.

 i also ordered diferent resistors for all of the various positions (same vaues, better tollerance) to see how that goes.

 tube sockets and the bridge rectifyer are ont he board, i await parts from supliers...


----------



## nikongod

hello headfi.

 amp is assembled, and running.

 every resistor has been replaced with a similar value vishay/dale 1/2W 1% (rn65 i think) or 1/3 in the 2 necessary positions.

 the 4 0.22uf caps were replaced with orange drop 0.22uf 400v caps. these are huge. i was concerned that they may not fit when i first opened the package...

 the 0.22uf input caps were replaced with 0.47uf caps. 

 this thing wounds SWEET. im playing it through some old cheap speakers that came with my sisters "comes in 1 big box" system. simply amazing. not superb quality, but at lest they didnt cost much.

 edit: what value of resistor is reccomended for placing in series witht eh 12V line to make the heaters last longer? i read that this was reccomended, but no specfic value was given.


----------



## ppl

Quote:


  Originally Posted by *blackie* 
_chopper building 101. remove all superflous chrome prior to radical performance mods hehe_

 

I for one Love tasteful chrome appointments on a Tube Amp Just like on Vintage Gear. I also Like Chrome on vintage cars and never found the Need to paint Nice chrome Bumper Black. These are simply my personal preferences on the use of chrome Y.M.M.V.

http://www.jolida.com/catalogue/images/JD3000B_big.jpg Real bad photo but a Beautiful Chrome Front panel on this Jolida JD3000B Tube Stereo Preamp

 I am also quite fond of Chrome on black two tone as tastefully represented in this antique sound labs model AQ-1001-DT http://www.soundscapeav.com/antique/aq1001dt.jpg and The 2tt Unisys Tube Amp http://www.exoticaudio.org/PAGE_2tt_unisis_TUBE_AMp.jpg A nice mix of Chrome and black with wood accents (Very nice) http://www.exoticaudio.org/PAGE_2Unison_sr1WOOD.jpg

 The All wood Chassis like this one is like I used to house my early Tube amps in my youth prior to cutting metal http://img.audioasylum.com/cgi/i.pl?...pMusic300B.jpg
 The ultimate expression in Tube amp manifestation in my view is this beauty right hear http://www.exoticaudio.org/AWESOME__...oblock_68k.jpg

 Ill leave you with that masterpiece to ponder.
http://www.welbornelabs.com/images/nycwestern.jpg
http://www.welbornelabs.com/images/nycwestern2.jpg


----------



## drewd

Quote:


  Originally Posted by *ppl* 
_ The ultimate expression in Tube amp manifestation in my view is this beauty right hear http://www.exoticaudio.org/AWESOME__...oblock_68k.jpg

 Ill leave you with that masterpiece to ponder.
http://www.welbornelabs.com/images/nycwestern.jpg
http://www.welbornelabs.com/images/nycwestern2.jpg_

 

Beauty is in the eye of the beholder, but I have to say that when I saw a picture of that Western Electric amp a few month ago, I was almost drooling. No, I take that back. I drooled. Even to a practical, form-follows-function, just-the-facts guy like me, whenever I see tubes, I think wood and chrome.

 -Drew


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## nikongod

update: 

 i replaced the r-18 resistor (480 ohms) with a 100 microhenry inductor.

 sound has improved slightly. i may add a smallish resistor (150ohms) in series with the coil as i think this resistor was both intended for current limiting, and a weak attempt at reducing line fluctuations. 

 the amp runs well without the resistor in place. i tested by shorting across it with aligator leads first...

 a larger (much larger) coil will replace the 2.2K ohm resistor later on. 

 parts are on the way for an improved high voltage psu (hexfreds, and im using the 0.22uf caps included wit the kit) and film&foil motor run caps have been ordered second hand off of ebay.

 the amp sounds quite nice (asside fromt eh psu hum/clicking) driving grado's directly or through a 100ohm cable. i could not decide weatehr to make a 75 (ety-style), or a 120ohm cable (everyone else's style) so i split the difference... i think i will solder the 100 ohm resistors inline with the 1/4" jack when i get about to mounting it.


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## nikongod

alps 50k ohm blue velvet pot is mounted on the board. stock pin's dont line up, they are too wide. gentle bending solved that well.

 upgraded psu has not been assembled yet. still awaiting some parts.


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## ilikemonkeys

can you post some pics please.

 I love my little amp.

 I use it almost everyday.

 B


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## nikongod

i think it is aereus that has hte more impressive setup... but here is my humble tube amp.

click for pic

 i think you can see a little of the heater glow in that pictar.


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## ilikemonkeys

why haven't you bridged those two output caps?

 It really helped add bass to my setup.

 I'd sugest it.


 How does the new volume pot help the sound?

 B


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## nikongod

Quote:


  Originally Posted by *ilikemonkeys* 
_why haven't you bridged those two output caps?
 It really helped add bass to my setup.
 I'd sugest it._

 

 how do you mean? put a "better" cap in parallel, or tie them together with something? i guess i could put a small crazy fast cap in parallel to them, but i really dont fiond bass lacking on this setup. i may change from my orange drop 0.22uf to 0.33uf though. im not totally sure thay will fit above the boad, these are almost touching the tubes.
  Quote:


 How does the new volume pot help the sound? 
 

 a "random" volume knob buzz i was having is gone (it was somewhat linked to knob position and would float from ear to ear,) psu noise is still present but smaller. overall i think a worthwhile change. chanel imbalance at low volumes is also nominal now.


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## ilikemonkeys

sorry man, I'm a microbiologist. I cant talk in EE language.

 On mine, I took the caps out and replaced them with wires. I have no idea how to say this in EE speak.

 I noticed a considerable increase in volume and midrange. Why? I have not idea. try it. It looks like you'd be able to replace them after you took them off.

 Riddle me this batman.....what are those gold looking things in the back of the amp? One's sitting on a trasnsformer... 

 B


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## aerius

Quote:


  Originally Posted by *ilikemonkeys* 
_Riddle me this batman.....what are those gold looking things in the back of the amp? One's sitting on a trasnsformer..._

 

Looks like a metal-bodied Vishay-Dale resistor, I have a couple of those in my amp as well.

 Ah yes, picture of my fully tweaked out amp, which has since been upgraded even more. Now have silver mica caps to bypass all those large polypropylene caps instead of the Wima MKP-10 caps you see in the picture. Makes the background quieter.


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## ilikemonkeys

I'm guessing that only the tubes are original.


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## nikongod

Quote:


  Originally Posted by *ilikemonkeys* 
_I'm guessing that only the tubes are original._

 

nope, he posted a while back that he got 2 diferent brands of tubed from the ones which came with the kit.

 i am envious.

 the resistors i have (as guessed correctly by aerius) are so that when changine headphones the amp dosnt "see" an open circuit on the output of the transofrmers. the little inctruction manual said this was bad. they are 10 ohm, 25W. they are WAY oversized, they were leftover from an automotive project. i cant hear a diference with them in or out, so they stay in for safety.

 edit: 
 bridge rectifier made with hexfred diodes "paralled" by the 0.22uf 250V film caps (which came with the kit, i try not to waste) is installed. backround noise is still present, which makes sense cause i havent attacked my psu caps too hard yet (the other 2 0.22uf film caps are bypassing 2 of the psu caps, i doubt they will do much in such a size diference, but i try, and i dont waste...). the noise seems more pleasant though. i guess i would call it a "lesser" evil. better caps will arrive shortly. larger chokes than aerius's will have to be sourced. i have to do SOMETHING to 1-up him here, my manhood is challanged.


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## nikongod

today i converted to triode, and removed the feedback resistor/cap set.

 OMG, it is awsome.

 sound quality is improved, and psu noise has decreased further still. i was actually ok with the stock sound quality, but it was "overshadowed" by the facking psu noise. now the psu noise is only present in the quietest of musical passages. im quite happy.

 motor run caps are in the mail, chokes have not yet been found appropriately priced for this amp and my budget.


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## nikongod

wooot

 a 26uF film cap has been wired in parallel with the dc side of my hexfred assy, and a similar cap (26uF) has been used to replace the stock 22uf electrolytic.

 im going to go play music. yaay.


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## nikongod

weeee.

 another 26uf film cap has been added in parallel to the largest electrolytic. sound is excelent.

 i now have a new problem how can i reduce the noise that comes throught the transformers? i have noise "seeping" out of my power input transformern into the coils of my output transformers. 

 i was thinking of building little boxes out of steel wire mesh (window screan) to contain the various transformers, and reduce the emf going from one to the other. would solid boxes/covers be better? anyone know of a CHEAP source of one?


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## bg4533

The problem is most likely the magnetic field from your transformers. You could add a bit of distance between them. For shielding be sure to use steel instead of aluminum. How concerned about aesthetics are you? Big hardware stores usually sell rolls of steel for cheap. You could build yourself an enclosure.


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## dwc

side question:
 - can this amp be easily converted to run 4-ohm speakers?


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## nikongod

you can always add a ballast resistor. not the cleanest option, but an EASY and fast one...


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## nikongod

UPDATE:

 i seperated the last section of the psu. YAAAAY. OMG, this is a HUGE improvement. 

 each tube (umm, is is the plate?) has aits own 26uf cap to ground, and a 2.21k resistor to the bigger half of the psu.

 before, there was some hardcore crosstalk. if you unpluged one of the inputs, the both chanels would play the "active" side equally (more or less) now, corsstalk is almost ZERO. i dont have appropriate tools to measure seperation, but its beyond my audible range at normal listening volumes. 

 im very happy.


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## nikongod

update:

 the 100uf cap has been replaced by 6X 28uf film caps (in parallel dunh) the whole "mess of bits" has been moved fromt eh small bit of wood to a larger one.

 a 5H choke has also been added between a single 28uf cap and the first electrolutic (220uf) 

 output transformers have been moved further from the power transformer. 

 sound is HOT. zero audible hum with my grados (no added resistance) or my senn's. 

 a dedicated pre-amp is in the works to make the thing run my k1000's better with my mp3 player. nothing too fancy maybee bass-boost.


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## chicken

I apologise if I am jacking this thread. (If so, please ignore me.)
 I had the opportunity to hear this amp in AZ at a store where I believe they designed the amp, and let me say, boy I was very impressed. I ended up getting a sweet deal on another product, so I didn't purchase one, but I was definately tempted. If you are in the market for a low-power DIY tube amp, give it a try. The price definately can't be beat.


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## nikongod

in a fit of what may best be described as "obvious stupidty" i hooked my ety er4-p's up to the toob amp. no resistance was added inline because i cant find my 100 ohm cable...

 they sound pretty sweet. they are cleaner than my grado's were before i started to mod the amp. 

 im soooo tempted to use up my 10 remaining film caps to make a 280uf film cap to replace the only electrolytic left on this amp. argh, i wish it wasnt as much work as it is to do that.

 maybee i will buy another inductor too.


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## bhjazz

Quote:


  Originally Posted by *ofb* 
_i don't know what i'm talking about, but perhaps someone here can point out the difference.

 the foreplay preamp is an audiophile quality kit for only $10 more.

http://www.bottlehead.com/et/adobesp..._stage_kit.htm

 i realize that's not quite the same thing, but i'm wondering if the foreplay could be easily modified into a good starter tube headphone amp, rather than trying to upgrade the web-tronics.

 just a thought._

 

Nope. This has been around on the Bottlehead website for quite some time, but it can't be done...and that comes from the designer! Instead, try the SEX amp, which has a nice headphone output that was part of the original design. And it can easily function as an integrated amp to drive efficient speakers as well.

http://www.bottlehead.com/et/adobespc/S.E.X./SEX.htm

 The current price is $369.


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## motherone

Has anyone seen this? (sorry if it was posted before on this thread -- I didn't see it when I read through it):

http://store.tubedepot.com/diy-k11m.html

 Looks to be the monoblock version of this amp.. A little more expensive, but it might be worth it since you can build it up a bit beefier...


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## flecom

anyone know if this amp would be ok for a K1k... cause im thinking those output transformers are designed for 8 ohms, and presenting them with 120ohms might lead to undesirable results?


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## bg4533

Quote:


  Originally Posted by *flecom* 
_anyone know if this amp would be ok for a K1k... cause im thinking those output transformers are designed for 8 ohms, and presenting them with 120ohms might lead to undesirable results?_

 

People have been using this amp with various headphones and don't seem to have problems. Most claim nice results. If you don't plan on doing any mods I would skip this. If you do it might be a nice option.


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## nikongod

i run mine into my k-1000's.

 it runs very well, but is mildly moded (mostly cap alterations, and similar easy stuff) so ymmmv...

 the amp drives the k-1000 to thunderous volumes when asked, but may require a pre-amp for higher volume output with a "low voltage source." my mp3 player is almost hopeless without a preamp.... my cd player rocks.


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## aerius

Quote:


  Originally Posted by *flecom* 
_anyone know if this amp would be ok for a K1k... cause im thinking those output transformers are designed for 8 ohms, and presenting them with 120ohms might lead to undesirable results?_

 

You could, but you'll have to make modifications to it for best results. At the very least you'll have to change the feedback resistors (R5 & R11) to higher values or else the amp will sound harsh and may run out of gain and become unstable. Best option is to do the triode conversion and remove the feedback resistors altogether, sound is improved and you don't have to worry about driving a 100 Ohm load. In my case I'm driving my K340 (400 ohm) right off the transformers with no resistors or anything to drop the impedance, works great.

 Which brings me to my last couple mods. The two 1.5k resistors on the input tubes set the gain on the amp. Because of all the mods I've done, the amp is far more sensitive to slight mis-matching in the tubes, and I don't have matched tubes here. As a result the sound is a bit off to one side depending on which tube I put where.

 So I replaced each 1.5k resistor with a 5k resistor in parallel with a 5k trimpot (20 turn). I can now dial in exactly how much gain I want on each side and get nicely centered stereo imaging. 

 Also added a couple 50uf cathode bypass caps to the input tubes. These are 50uf motor run caps that are wired in parallel with the 5k resistor/trimpot assembly. Gives a fair bit more gain to the amp since as I understand it, it removes the local feedback around the tube. Other than that it adds a bit more depth to the soundstage and the sounds seems to surround me more and feels more involving.


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## nikongod

woot.

 new tubes have FINALLLY been found!!!
 i got 4sylvanias, and 4 ge's. im psyched. im currently burning in the sylvanias into about 6 ohms, through the cable i braided up for my akg k-340's 
	

	
	
		
		

		
			




 i should probably go to aerius's house and just hijack his audi rig, it would save me the trouble of getting a cd player like he has...

 also, class-a bias resistors on power triodes have been bypassed with 470uf elna tonerex caps. they were leftovers from my millet project. the sound makes me happy in the pants.


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## aerius

Quote:


  Originally Posted by *nikongod* 
_i should probably go to aerius's house and just hijack his audi rig, it would save me the trouble of getting a cd player like he has..._

 

Seeing how you have the K340 now, you should pilfer the transformers from the kit and use them for the Objective Interim 6SN7 Headphone Amp. Gives more gain & headroom with less distortion, brings out the midrange, and improves the soundstage & imaging quite a bit.


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## nikongod

i probably will in a while. unless i build the "hybrid" i have had burning a hole in my mind. eeh, whatever works.


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## KevC

Sorry for reviving an old thread, but I'm interested in giving some life to some old dusty monitors lying around in my basement. These are from the early 90s, JBL Pro IIIs. I figured I needed some music (aside from headphones) in my room so I'm considering purchasing this kit and hooking up the speakers.

 Thoughts? (probably going to get preassembled since I'm short on time and don't trust myself with soldering)


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## bhjazz

Quote:


  Originally Posted by *KevC* 
_ I figured I needed some music (aside from headphones) in my room so I'm considering purchasing this kit and hooking up the speakers._

 

Which kit? !!


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## splaz

Sorry if this sounds stupid but I don't know that much about tubes.

 Could you substitute the tubes in this kit with others ?


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## nikongod

Quote:


  Originally Posted by *splaz* 
_Sorry if this sounds stupid but I don't know that much about tubes.

 Could you substitute the tubes in this kit with others ?_

 

you can use other 11ms8 tubes, btu there are no other drop in replacements or close approximations.


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## mrandychen

what's the difference between this and the monoblock design?


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## KevC

Quote:


  Originally Posted by *bhjazz* 
_Which kit? !!_

 

The first poster's...


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## motherone

Quote:


  Originally Posted by *KevC* 
_Sorry for reviving an old thread, but I'm interested in giving some life to some old dusty monitors lying around in my basement. These are from the early 90s, JBL Pro IIIs. I figured I needed some music (aside from headphones) in my room so I'm considering purchasing this kit and hooking up the speakers.

 Thoughts? (probably going to get preassembled since I'm short on time and don't trust myself with soldering)_

 

Well, I bought bg4533's a few months ago, tore it apart and tweaked it. Untweaked, I think it'll be fine for your needs. To get the most out of it, you really do need to beef up the power supply, swap the coupling caps, and add the ultrafast soft-recovery diode in the high-voltage PSU. 

 If you're really short on time, and want something cheap to power your JBL's, maybe you should look at one of the S-5 Sonic Impact T-amps. They're comparable in power, sound great, and only cost $25ish. Then you could pick this kit up when you have the time.. After all, making it yourself is more fun!


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## nikongod

i ran my amp the other day, and its awsome.

 that is all.

 then my sister made me "turn it down." crikey. it wasnt even that loud.

 edited/added:
 would the 10gv8 be anb acceptable substitute for the 11ms8?


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## imported_farmer_rob

anyone interested in one of these ASSEMBLED- I'm thinking of selling mine...

 lemme know


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## nikongod

i saw from the FS thread that you have the 10gv8 variant.

 could you please post some part values so that i may mod my amp to use these tubes? the pinouts look similar.

 thanks.


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## Canuck57

I recently purchased this amplifier used and I'm having a problem with it. It appears to have been undamaged during shipment.

 Here's the problem:

 When i turn the volume knob clockwise there is a VERY loud humming noise coming through the speakers. When the volume control is at maximum (all the way clockwise) the music is loud and clear with no hum at all (sounds great). There is also no humming noise with the volume knob turned all the way to the left (counter clockwise).

 Is this simply a problem with the volume pot?

 I have very efficient Cerwin Vega speakers hooked up to the amp and I've tried two different sources.

 Any help/suggestions you can offer would be appreciated.

 By the way I have no experience/knowledge with respect to soldering/wiring etc.


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## Canuck57

^^


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## nikongod

who built it?

 what mods does it have?


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## Canuck57

It was working properly before I received it and it doesn't have any mods.


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## Canuck57

Any ideas?


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## nikongod

After a brief stint being amp-less after plugging my E90 into a 24V wallwart (oops) I decided it was time to get off my lazy bumm and get cracking on my ESP-950. more on that in a moment.

 For some time I have been dreaming of an amp to run electrostatics and dynamics. Think of the singlepower concerto, but less likely to explode. and making use of stuff I already have on hand.

 A long time ago I saw a post (maybe it was an article) that a tube push-pull speaker amp can be used as a STAX amp with the addition of output caps to drive the headphones off the plates of the tubes and a bias supply. I still have this amp and it seems to fit the bill well. It is a fairly little guy, at only 4W/ch (triode strapped) but it sounds quite nice with all the mods I have in it so why not?

 Anyways, a bit of searching on the web found the appropriate part nnumbers for the various stax connectors. I suppose now is a good time to say that if you take the center pin out of the female one the hole can be tapped for an 8-32 screw and a setscrew put in with a little windo-weld. A bias supply was easy enough to build with a voltage multiplier. The voltage on the bias is a little hot for stax at 580V but that should be easy enough to fix when I get bored with my ESP-950 and find motivation. The amp is kind of sort of in the "permanent protoype" phase, on a plank of wood with wires running willy-nilly all over the place.

 So I first modified the amp. put in all the junk to drive the electrostatics off the plate of the tubes, and wired up the dynamic outputs.

 Next up I rewired the ESP-950 and this is where it gets good. seeing as how I had never done this before I tested them first on my SRM-212. to say that I was shocked would be an understatement!

 The difference in the bass depth and overall quality as well as overall presentation compared to my cloudy memory of my E90 was a HUGE step! wow wow wow Anyone who has not reterminated their ESP-950 should do it!

 The tweaked amp is no slouch either, although my ESP-950 are acting up as they often do. The brief moments of pure music they do give are outstandingly nice.

 Ok so after that I hit the dynamic outputs with my D5000 because they were handy. Yeppo, the dynamic outputs still work really well with great bass and balance. the treble has a nice edge to it that is not quite irritating, but demands attention. yummy.


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## sachu

holy christ Ari... this is friggin exciting news..

 I am going to have to clear up funds to build one now...ecstatic you got it going last night...pics when you can please..even if it is only on a wooden plank.


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## FrankCooter

I've done similar "experiments" with very positive results. Early in the "Poor Man's Stax Amp" thread I advocated such an approach. There are a lot of interesting possibilities here. You could use a pair of cheap 2a3s for the outputs. Because of the relative insensitivity of electrostats, you might even get away with AC heating. If you don't like the cap output and were willing to invest a little money, you could use a 1:1 push-pull to push-pull interstage transformer for the output. You could possibly even go all DHT by using something like a push-pull pair of choke-loaded 3c24 as outputs driven by a 3c24 as a voltage amp/phase splitter. Lots of food for thought here.


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## nikongod

Quote:


  Originally Posted by *FrankCooter* /img/forum/go_quote.gif 
_I've done similar "experiments" with very positive results. Early in the "Poor Man's Stax Amp" thread I advocated such an approach. There are a lot of interesting possibilities here._

 

Yepp, I saw the posts and they were part of the inspiration to get this thing runing. Thanks 
	

	
	
		
		

		
		
	


	



  Quote:


 You could use a pair of cheap 2a3s for the outputs. Because of the relative insensitivity of electrostats, you might even get away with AC heating. 
 

I have plans for "version 2" (evil laugh) with a differntial gain/input stage: this amp has a Williamson style front end and it was a big PITA to get it to run headphone quiet. 

 As it sits this one only outputs about 50vrms stator to stator which is inadequate according to most 
	

	
	
		
		

		
		
	


	




 but for my average 60dB listening level and a grand total of about $275 in parts ($225 of which was sitting idle on a shelf) it does quite well. I think I take a bit too much pleasure building stuff that nobody thinks will work (lol only 50v, heh, some dynamic amps can do that!) and saying look! 

  Quote:


 If you don't like the cap output and were willing to invest a little money, you could use a 1:1 push-pull to push-pull interstage transformer for the output. You could possibly even go all DHT by using something like a push-pull pair of choke-loaded 3c24 as outputs driven by a 3c24 as a voltage amp/phase splitter. Lots of food for thought here. 
 

how does this sound:
 I have a SP extreme (simple cathode follower output with both sections of 6as7/5998 paralleled) on the way. After fixing the obvious flaws:
 600:15K(ct) output transformer to get the electrostatic drive. Nice and cheap from edcor


----------



## FrankCooter

I think I take a bit too much pleasure building stuff that nobody thinks will work [/QUOTE said:
			
		

> As you've probably guessed by now, I'm the same way, probably worse! Who else would be stupid enough to build headphone amps with HV transmitting tubes! Lots and lots of failures, but every once in a while you get on to something good that others have bypassed.
> 
> Your cheap Edcor idea is creative and interesting, but I see some issues:
> 
> ...


----------



## nikongod

Quote:


  Originally Posted by *FrankCooter* /img/forum/go_quote.gif 
_ Your cheap Edcor idea is creative and interesting, but I see some issues:

 1) The secondary isn't built for any signifigant DC. I assume you're going to para-feed?_

 

yes, parafeed except using the transformer as a step up. The coolness is that I plan to use a switched headphone jack so that when a 1/4" plug goes in the electrostatics mute and the transformers switch out of the amp like they are not even there.

 The max voltage swing will still be somewhat limited as you say, but I think from the amp now that Im OK with that. I only need 10vrms out of the extreme to get more voltage out of the amp than what I have now. A big monster cathode follower should be able to put 10v into 600ohms reasonably cleanly.

 I measured my "voltage use" stator to stator, heh, 6vrms max: Im a lightweight.
  Quote:


 2) Designed for small signal use, the secondary won't like HV AC either. You'll have to try it,but make sure if it "goes" it doesn't take anything else with it. 
 

They make a 600:15K transformer rated for 2.5W which I think should be good enough (assuming they are serious about the 2.5W bit) but I will ask them if there is a max AC voltage on the secondary. I had not thought that bit through, thanks 
	

	
	
		
		

		
		
	


	



  Quote:


 3) Your SP "Extreme" probably has a net gain of 6-12db. Wired backward, your Edcor should have about a 1:5 step-up. You're going to be way short in gain. You could plate load the 6as7 outputs, eliminate any global feedback, and para-feed the Edcor off the plate rather than the cathode. This is what I'd try. Fun and cheap project even if it doesn't work! 
 

yeppo, fun and really cheap. Edcor makes the power transformer I want to use to make the extreme more reliable so all the iron from 1 place should save shipping.

 I like the idea of running the transformer off the plate of the 6as7, but I think it will be too much work to implement in the extreme. I think that converting the gain stage from plate resistor&cathode resistor+cap to CCS/LED will buy enough gain to compensate. Even if I dont need the extra gain/voltage swing I like the improvements to distortions it brings along so thats pretty certain to change when the PCB is out.


----------

