# The Dynahi Construction Related Questions Thread



## rsaavedra

I thought would be a good idea to start a thread that will compile all or most Dynahi construction related questions. There are and will be many such questions along the way. Some people are posting some already in the Elma Attenuator Groupbuy Thread, and some others are posting questions in the Dynahi Boards Groupbuy Thread.

 I have one question myself. Related to populating the Elma attenuator. How do I know what's best for me, whether a 25k vs 50k configuration??? Is that more or less equivalent to fixing the attenuator to a Hi-gain (25k) vs a Low-gain (50k)?


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## Jack Head

on the boards the SK389 show as two seperate (DQ 2) transistors yet it is a dual J-Fet with 7 pins also the 2SJ209 is a dual (DQ 3) how are these being used ?


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## kevin gilmore

On the fets you don't connect the middle pin, either bend it up
 or cut it off.


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## Edwood

Post some pr0n when you can, guys. 
	

	
	
		
		

		
			





 -Ed


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## pooooo

How are you guys going to deal with the power supply?


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## TrevorNetwork

Was there ever a group buy for the heatsink(s)? Also, I am unable to find the OP27 opamp. Does a substitution exist? Will any opamp do?


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## strohmie

Trevor, the op-amp I'm going to try out first for this amp is the OP177GP, which someone had mentioned in a previous thread.

 Just to be thorough, I'm going to repost my board propagation quasi-guide in this thread (I had posted it in the Dynahi pics board earlier today)...







 On the right in this picture on top and bottom are spaces for resistors -- these can be recognized by the long rectangular shapes with leads coming out each end. Resistor orientation isn't really specific, but for continuity you should orient it so that the letters on the board and resistor are going in the same direction. Pull the leads in from each side of the resistor so that it is close to the board itself.

 To the left on top and bottom are transistor slots -- the transistors themselves have three leads that all eventually bend inward. You want to push the leads through until you reach those bends. You should feel resistance when you get there. Orient the transistor so that the curved side lines up with the curved image on the board.






 Here we have a transistor slot with a heat sink attached, as shown in the image. Again, line the heat sink (the silver part of this type of transistor) up as it is shown on the board.






 Here you can see a slot for a capacitor -- note the + next to one of the holes. This indicates that the capacitor is a polarised one, and the positive lead goes in the plus side. You should be able to identify the positive lead because it should be longer than the negative lead.






 Here is an image of the op-amp slot on the board. Again, the indent seen on the left side of the op amp should line up with the indent (or sometimes simply a mark or small hole) on the op-amp. You might want to first install a socket for the op amp so that you can easily replace it if it goes dead or you want to do some op-rolling. ^_^






 This is a picture of the rectangular capacitor that's near the bottom towards the middle-left of the board. This is a non-polarised capacitor, but you may as well orient it so that the text on the cap sits the same way as the text on the board.


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## hadron

I haven't gotten the transistors yet and was wondering if the package on the 2SC3421 and 2SA1358 is all plastic or metal backed? Will they need to be electrically isolated from the heatsink?


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## djwkjp

if i remember from my brief look at the transistors i have, they are all plastic, although i seem to remember kevin saying that silicon washers are needed to insulate them from their mounting screws. i could be wrong, though.
 i am also wondering about the heatsink group buy. kevin posted what heatsinks he used and said they were relatively cheap if purchased in bulk. i would imagine that somebody could start to organize the group buy relatively soon. i would volunteer, but i am too busy with school and i am afraid i dont have the patience or resources that raul does. if someone searches through one of the threads related to the dynahi, they can find a link to the heatsinks.

 peace
 dan


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## hadron

I got my heatsinks from here: http://www.surplussales.com/Heatsinks/HeatSink1.html

 TrevorNetwork, try looking for the OPA27, the OPA177 will work as well. The latter is cheaper with slightly better offset and drift specs, though a bit noisier.


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## djwkjp

hadron-
 which one did you get? do you have any specs to know it will work for the dynahi?


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## kevin gilmore

The HS-TWS will work fine. In fact i just ordered a dozen.
 Much easier than the $72 i paid for the first 2.

 The silicon wafers are to make sure there is real good contact
 between the transistors and the heatsink. No electrical isolation
 is needed.

 I'm getting too old to deal with messy thermal glue. Peel and stick.
 mouser part number 532-53-77-9ac


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## TrevorNetwork

Kevin,

 Regarding the heatsinks; how many of the HS-TWS are needed? Has anyone purchased more than a few, that is willing to sell me what's needed?

 Trevor


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## kevin gilmore

1 heatsink per audio channel. Plus an angled piece of aluminum cut
 to shape and punched or drilled per channel.

 You could use a 3rd heatsink for the pass transistors for the 
 (yet to be designed) power supply. 

 There just aren't enough hours in the day...


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## TrevorNetwork

Thanks Kevin!


 So does anyone have a couple of HS-TWS and the appropriate angled aluminum to spare? 

 /has PayPal


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## TrevorNetwork

Does anyone have or know where to get the angled aluminum?

 Kevin:

 Will the power supply you're designing for the Dynahi be superior or more economical than the original reference supplies? When do you expect it to be finished?

 Sorry for all the questions!


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## hadron

A warning about the HS-TWS, turns out the web page dimensions have a typo, the fin height is 29/32" not 2-9/32". My rough calculations give about 2.5 °C/W, should still be plenty for 15W, so I think I'll keep them without complaint.

 I snapped a photo to give a sense of the size, the heat sink is just over 4-1/2" wide.

 For thermal compound, ordered some paraffin based phase-change interface material, kinda pricey at $17, but I can't stand using that other goopy stuff either. Digi-Key part HS243-ND.

 For the PS, I've made a few further refinements (adding pre-regs, a couple more caps, and opamp protection diodes) to Kevin's tracking version of the Didden-Jung circuit, from my previous post on the subject. Should have all the parts soon if I can remember to order the transformer tomorrow 
	

	
	
		
		

		
		
	


	




 I can draw up a new schematic when I get the chance if anyone is interested (PM me rather than cluttering up this thread).


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## pooooo

The transistor looks like this. 





 As you can see, electrical isolation between transistors and heatsinks are not necessary. However, some soft material between them might improve the thermal coupling in case the surface of the heatsink is not that smooth.

 I think I'll stick with Dr. Gilmore's opamp-based power supply. I will power-up the 317/337 with darlington power transistors so that they won't get fried.


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## hadron

pooooo, why did you include the darlingtons? A LT1085/1185 reg pair will do 3A each. [Edit] and should have better ripple rejection and lower noise, important since the final stage opamps are supplied from this.


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## pooooo

Quote:


  Originally Posted by *hadron* 
_pooooo, why did you include the darlingtons? A LT1085/1185 reg pair will do 3A each. [Edit] and should have better ripple rejection and lower noise, important since the final stage opamps are supplied from this._

 

I found all the parts I need in my drawer while I was trying to build this, so some of the part values are a little bit different from Dr. Gilmore's original schematic. That's also a reason why the current through each transistor became 150ma instead of Kevin's 100ma. What makes things worse is that when I built this monster amp, I was thinking about using it also as a low power amplifier for my speaker. So I used 6 pairs of transistors per channel in the output stage instead of two, and my power transformer is a 300VA one. Well, different goal from most of you.


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## sft

I suggest that you can build a balaced bridge dynahi to drive your speaker for more power and control.

 From My "Gilmore experience", balanced bridge version sounds great !


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## pooooo

Quote:


  Originally Posted by *sft* 
_I suggest that you can build a balaced bridge dynahi to drive your speaker for more power and control.

 From My "Gilmore experience", balanced bridge version sounds great !_

 

Yeah, that will be great. Thanks for you advice, 
 However, this is only for my bookshelf speakers in my bedroom, so I don't think I'm going to need that much power. And I don't have a pre-amp with balanced output. This is also a problem. 
 The speakers of my main system is not a suitable load for dynahi, I guess. The impedance is less than 1ohm.


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## sft

Quote:


  Originally Posted by *pooooo* 
_How are you guys going to deal with the power supply?_

 

Simple Dynahi PSU(output 30V) or Pre-regulator part(output 39V) using LT1085, 1033


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## sft

Quote:


  Originally Posted by *kevin gilmore* 
_...

 opa541's work as the whole thing. 2 of them plus a 5 volt reference.
 just like original power supply.

 way busy, hope to get to this by the end of 2004._

 

According to Dr.Gilmore's thought, I've built this and it works.

 Space is ready for two large heatsinks.













 Some close-up photos:

 OPA541




 two large heatsinks:




 Current limit resistor:FUKUSHIMA's 0.22R/5W


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## chillysalsa

I think I went overboard.. I ordered 2 of these GFC Tectrol 28V, 4A  power supplies. They hum/vibrate a bit, so I think I will make a remote / separate enclosure for these puppies. 

 I'm hoping it's worth it, looking at their specs:





 Is that any good??? Seems better than the PowerOne / Condor supplies that were suggested...


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## Edwood

Quote:


  Originally Posted by *TrevorNetwork* 
_Does anyone have or know where to get the angled aluminum?

 Kevin:

 Will the power supply you're designing for the Dynahi be superior or more economical than the original reference supplies? When do you expect it to be finished?

 Sorry for all the questions! 
	

	
	
		
		

		
		
	


	





_

 

www.onlinemetals.com ?

 -Ed


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## hadron

My (hopefully) final draft of the Gilmore-Didden-Jung tracking regulator. R15 & C13 may not be necessary, I included them for equal opamp input impedance and symmetry. Shouldn't be too difficult to convert back to a more standard (non-tracking) Jung super-regulator, if that is your preference. Also hoping the D44H11 Hfe is a bit more than the 20 min spec, otherwise might need to reduce the R9 value.

 The transformer is not stocked by anyone I've found, put an order in to Parts Connexion but it will be at least a week...


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## steel

Quote:


  Originally Posted by *sft* 
_According to Dr.Gilmore's thought, I've built this and it works._

 

It's great
 I'll to try it...

 where to buy the Pre-regulator's PCB ?


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## sft

Sorry, I've forgot where to buy. 
	

	
	
		
		

		
		
	


	



 I found them in my drawer, then cut and collect.
 Three terminal regulator kit is common and easily to get.


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## kevin gilmore

Here is how i make the angle brackets for the surplus sales heatsinks.
 I realize most of you will not have this equipment, but for future reference
 this is how i do it.

 (Regular size pictures from my old camera, refuse to leave good camera
 at work)

 1) cut the stock aluminum pieces to 5 x 4.4 inch with one of these
http://gilmore.chem.northwestern.edu/heatsink3.jpg
 I use 3/4 hard 1.8 thick aluminum sheet

 2) Layout and centerpunch the holes
http://gilmore.chem.northwestern.edu/heatsink7.jpg

 3) Punch the holes
http://gilmore.chem.northwestern.edu/heatsink2.jpg

 4) Drill the heatsink holes with a #28 drill and tap with 8-32
http://gilmore.chem.northwestern.edu/heatsink5.jpg
 large cup of coffee absolutely required, the resultant shaking
 keeps the tap from binding.

 Result
http://gilmore.chem.northwestern.edu/heatsink1.jpg
http://gilmore.chem.northwestern.edu/heatsink6.jpg

 Total construction time about 45 minutes.
 (includes making a pot of coffee)


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## eric343

Why do you punch the holes as opposed to drilling them?


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## kevin gilmore

perfect holes with no problems on the reverse side.


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## strohmie

Just checking to see how everyone's going with the Dynahi. Only missing one part for mine, the large caps (I bought some Nichicon MUSE caps but didn't pay close enough attention to the diameter -- anyone have a good cap they can recommend?):







 I had some trouble finding Vishay-Dale RN60C resistors at 300 ohms, so I went with some others I found elsewhere (RN60D instead). Figured it would be better to use 300s just to make sure there wouldn't be too much overheating of the resistors. I've got a couple extra Jung regulator boards that I might use for this purpose, though it might be fun to breadboard the Gilmore-Didden-Jung instead (and it actually might be less expensive than propagating two separate standard Jungs).

 Anyone have it complete?


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## hadron

Quote:


  Originally Posted by *strohmie* 
_Only missing one part for mine, the large caps (I bought some Nichicon MUSE caps but didn't pay close enough attention to the diameter -- anyone have a good cap they can recommend?):_

 

I used Panasonic FC 50V 120uF, DigiKey part P11255-ND; 10mm diameter, 12.5mm height. Got quite a few of them, mostly for my power supply.

 Still waiting for my heatsink angle Al and PS transformer to arrive. After that it's just a matter of picking a box to put it in... (assuming the GDJ reg works out according to plan, but how often does that happen?).


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## chillysalsa

couple questions:

 Is Mouser the best place to get Vishay-Dale resistors in Canada?

 Do the LEDs have to be RED or is any with 1.7V drop ok?


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## sft

Yes, any with 1.7V drop is OK.(ex: yellow, orange)

 ---------------------------------------------------------

 This is my solution for heatsink.

 1)Get a heatsink for TO-3 Power Transisitor(about 60VA) like this:




 large photo


 2)Cut it into two pieces(the scroll saw is not necessary, hand saw+patience works also)







 large photo______  large photo


 3)Drill 8 3mm holes(Many tools are capable of drilling 3mm hole)







 large photo______  large photo

 4)Lock it to the bottom of the case such that the whole case is your heatsink.




 large photo

 5)Have a cup of good oolong tea !


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## aos

That's a great photo-guide there. Too bad most people don't have any kind of machine saw that could do that...


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## kevin gilmore

Great job. For people with limited tools, a hand made jig of the
 proper dimensions, that heatsink or one similar, and a dremel
 tool with a tiny machine bit will work to put a significant score
 in the heatsink. Then if you are careful with a fine handsaw or
 hand scroll saw you can make a very clean cut. And finish it
 off with a fine file to make it look pretty.


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## rsaavedra

Went the easy route, just ordered two Condor power supplies from Alliedelec.com. Also, ordered all the board components (digikey, mouser) and the heat sinks (surplussales). Now I have to get the resistors for the Elma. 

 Anybody has suggestions for RCA connectors, power switch, input switch, headphone jack?


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## RickP

Quote:


 4)Lock it to the bottom of the case such that the whole case is your heatsink. 
 

 Wouldn't you want to consider NOT anchoring the board tightly due to the thermal expansion and contraction of the heatsink/angle assembly? This might lead to fatigue and failure of the output transistor bodies. Perhaps using flexible fasteners (spring, nylon) to allow for the side of the circuit board away from the output transistors to 'float' might be worthwhile.


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## sft

Shure.
 Every contact needs proper washer and spring.
 I'll post more photos to show this later.


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## hadron

Quote:


  Originally Posted by *RickP* 
_Wouldn't you want to consider NOT anchoring the board tightly due to the thermal expansion and contraction of the heatsink/angle assembly? This might lead to fatigue and failure of the output transistor bodies. Perhaps using flexible fasteners (spring, nylon) to allow for the side of the circuit board away from the output transistors to 'float' might be worthwhile._

 

Attaching the heatsink to the chassis is a good thing, as it will increase the heat dissipation area; though it is advisable to drill slightly oversized holes and use Belleville (conical) or wave washers that will allow for some movement. Same applies to the power transistors.

 ON Semi has a good App Note on this subject, it's rather technical but there's still plenty to be learned by just looking at the diagrams.


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## sft

Thanks for hadron's link. 
 My method is almost the same as the Note.






 large photo

 Another view:
 As the arrow point, distance between HS and transisor's leg is about 1mm to avoid shorting.




 large photo



 Temperature of HS is about 60~65℃, and DC-offset is within ±3mV even though without DC-Servo.


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## kevin gilmore

The start of the dynomite power supply

http://gilmore.chem.northwestern.edu/dynomiteps.jpg

 +/-40 volts first stage power supply at 4 amperes each.
 In a 17 x 14 x 5 chassis. Already weighs in at 25 lbs...


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## intlplby

wow that is big....... any guesses as to when it will be finalized

 so many DIY projects on here 

 phils new tube project and M^2

 btw next you can change it to Monsieur Stax or Signore Stax


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## kevin gilmore

Thats just the power supply. The amp is in another box.

 Many parts have not come in yet. Especially the amphenol umbilical
 connectors and the techflex. WBT chassis mount connectors not
 here yet either.

 Wait till you see the blue laser diode that will be used to light the
 glass power button. Very retro.


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## eric343

Quote:


  Originally Posted by *kevin gilmore* 
_Wait till you see the blue laser diode that will be used to light the
 glass power button. Very retro._

 

I didn't know blue laser diodes were available, especially usable ones. How did you get your hands on one?!


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## sft




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## strohmie

Is that reddish rectangular cap a Wima MKP10? I was thinking about replacing the ones I have on the board now with one of those just for the sake of emptying my wallet a bit more.


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## sft

It's WIMA MKS4.


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## sft

Hi! Kevin, 

 I can't decide which version is "better" for dynomite(or dynamite; dynamight 
	

	
	
		
		

		
		
	


	




 )

 1)similar to Headwize project
 2)four all the same amp ckt. (I've XLR source)

 Can you give me any suggesion?

 Thanks in advance.


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## kevin gilmore

Since i have an all balanced system, i'm building #2.


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## TrevorNetwork

A bit OT, but does anyone have any impressions of this amplifier versus a (maxed) PPA?


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## hadron

Not the best photo, being on the bench, but now that I finally got the transformer this project is coming together nicely...






 On the top is the unregulated stage of the power supply (the part outside the box in my schematic), fits perfectly on a RadioShack 4-1/2 x 6" perfboard. The bottom shows the breadboarded positive leg of the GDJ reg, this hasn't been plugged in yet, just showing it for a sense of size. Will test as time permits.


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## kevin gilmore

Now those are a pair of real angle brackets


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## rsaavedra

Man those brackets are so big, they *are* heatsinks themselves 
	

	
	
		
		

		
		
	


	




 Mine are in transit, Condors and some parts have arrived from Mouser and Digikey already. Haven't started though, most likely this coming weekend.

 Kevin btw, you know I got charged taxes for the condor supplies from AlliedElec, even though I ordered them online. Is this normal? I have called them and it seems they have to charge taxes unless I'm going to resell them charging taxes myself. In any case, this is the first time I purchase anything online and I get charged taxes for it.


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## gastro54

That's strange about the taxes... You would only be charged if the seller is in the same state as you. (I don't even think FL has retail taxes)


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## rsaavedra

Quote:


  Originally Posted by *gastro54* 
_That's strange about the taxes... You would only be charged if the seller is in the same state as you. (I don't even think FL has retail taxes)_

 

Btw the package wasn't even shipped from FL, came from TX.


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## Pars

If Allied has any operations in your state (which I am sure they do, sales office, etc.) you have to pay taxes. I believe that is the general rule, but am sure I will be corrected if it is not


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## TrevorNetwork

Where did you get those brackets? Are they compatible with the HS-TWS heatsinks?

 Also,

 Which is the better PSU; Condor or PowerOne?


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## rsaavedra

Quote:


  Originally Posted by *TrevorNetwork* 
_Which is the better PSU; Condor or PowerOne?_

 

Kevin might answer better for sure, he told me either one would do fine as long as you get the two amp version (one amp would get too hot). I went for the Condor because that's the one Kevin had used in his prototype, but also, it has three years warranty, while the other has just two. The Condor is only a couple bucks more expensive, $57.96 vs. $55.0.

 Late Edit: checking the pictures Kevin had posted, the power supplies in his Dynahi were "PMC Powermate Corr".


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## TrevorNetwork

Can someone give me a digikey part numbers for the DC terminals, 10k trimpots and Wima capacitors used on the Dynahi board?

 Hadron:

 Where did you obtain the brackets?


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## rsaavedra

Quote:


  Originally Posted by *Pars* 
_If Allied has any operations in your state (which I am sure they do, sales office, etc.) you have to pay taxes._

 

Got back home and had a message in the answering machine from Alliedelec, explaining that they indeed do have offices in FL, so they had to charge the taxes even with orders placed online if they are going to FL. All was in order then.


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## rsaavedra

Quote:


  Originally Posted by *TrevorNetwork* 
_Can someone give me a digikey part numbers for the DC terminals, 10k trimpots and Wima capacitors used on the Dynahi board?_

 

Trevor, so far I've placed orders using the part #'s suggested by BCBill:
http://www5.head-fi.org/forums/showp...&postcount=205


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## hadron

Got the 1/4x3x3" angle Al from speedymetal on eBay. S&H is kinda high, but I really don't need 8' of the stuff, otherwise I would have gotten it from McMaster-Carr.

 Here's a better pic of the heatsink assembly.







 The conical washers have a bonded rubber part, might remove this, also need longer bolts since I added these.


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## rsaavedra

I wonder if some large enough aluminum angles in Home Depot or Lowes are good alternatives to these angles.

 Btw, now that we are all sharing pics, here's the condor power supplies:


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## hadron

Trevor, DigiKey doesn't stock Wima, but the BC MKP metallized polypropylene is almost as good, part BC2083-ND. The 10k pot is CT9W103-ND. Also, I used a silver-mica 33pF, 338-1047-ND.


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## TrevorNetwork

Hadron:

 Edit again! 
	

	
	
		
		

		
		
	


	




 What length did you use for each angle?

 All:

 Does anyone have a part number for the appropriate DC terminals for the PCBs?

 Regarding the Condor PSU, does it use bare wire inputs and outputs? Or does it have an IEC input jack, and bare wire outputs?


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## hadron

Measuring along the outer edge of the bracket: the transistor leg is 1.1", the heatsink side is 2.8". The width is 5.6", the extra inch over the HS-TWS width is to allow for chassis attachment, though I haven't drilled the holes for this yet.


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## intlplby

also.... what parts can be maxxed out.... for example what is the best capacitor to use in this project..... for this application does it make a difference what brand it is?


 found the transistors at B&D


 since i have 12 boards the bulk rates really help me out.....

 total cost per board is about $40..... $80 per amp

 not including heatsink or L-bracket

 i might consider letting a few people piggy back on my orders, but i don't want to coordinate a whole group buy right now since it is so time consuming


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## rsaavedra

Quote:


  Originally Posted by *TrevorNetwork* 
_Regarding the Condor PSU, does it use bare wire inputs and outputs? Or does it have an IEC input jack, and bare wire outputs?_

 

No IEC on the Condor. Check out some white circles I added to the photo of the Condors above. The circled pins on the bottom left are the DC outputs, the circled tabs on top/right of the transformer are the AC inputs. The Condors can have 100, 120, 215, and 230 AC volts as inputs, so there are several possible input connectivity configurations, that's why so many input tabs.

 Definitely these power supplies are not a good choice for groupbuys, these things are heavy. Including tax and shipping, total I paid for both was actually $140.31. TX to FL shipping was $14.60.


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## strohmie

I e-mailed those aluminum people on eBay Hadron ordered from to see if they could custom cut one of those 1/4" by 3" by 3" by 13 1/4" pieces into two 1/4" by 1" by 2.75" by 5" pieces (seems like reasonable proportions)...I'll let you guys know if/when I hear back. They have a note in the auction that says "no cutting charges," so here's to hoping.


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## rsaavedra

Anyone knows who carries headphone jacks like those in this amp. How about that volume knob as well? Thanks a lot!


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## Jupiter

The headphone jack could be a Neutrik NMJ6HC-S, available from Mouser and Farnell.


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## sft

I think another Neutrik Jack is fine, too.


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## jerry1130

The knob is made by Eagle Palstic, here is the Mouser link:

http://www.mouser.com/index.cfm?hand..._pcodeid=04511


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## rsaavedra

Thanks for the help guys. Have yet another question, where are you getting those teflon washers from? Online I've only seen these ones, which seem too thin. Should I definitely use teflon, e.g. nylon won't tolerate the high temperatures so well?

 Btw I want to use them not so much between the bolt heads and the transistors, but between the aluminum angle and the boards. Can probably just use some stripes of punched-through plumber's teflon there, but would rather have nice washers.


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## intlplby

it shouldn't get so hot that nylon starts melting.

 The only common polymer that really melts at a fairly low temperature is polypropelyne, which has a glass transition temperature at around 170 F... i don't remember the melting point but I am sure it is less than the bioiling point of water.


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## TrevorNetwork

Do we have a guide for drilling holes in the bracket? Positioning, spacing, etc.


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## strohmie

To anyone thinking of getting those aluminum pieces off eBay -- they can cut the aluminum pieces down in length but can't cut one of the 3" legs down to 1" because of clamping issues. So basically what you'd have to do (and what I'm planning to do, and what I assume Hadron did) is cut the metal down yourself and then sand to a nice finish.


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## hadron

I have access to a machine shop, so the brackets were roughed out on a bandsaw and cleaned up on a mill, though a coping saw and sandpaper or a file would also work if hand tools are all that's available. Also, flattened the mating surfaces on the bracket and heatsink using a beltsander and finished with a bit of lapping by hand.

 On another note, I'm enjoying listening to the dynahi as I type this 
	

	
	
		
		

		
			





 Haven't had a chance to work on the power supply yet, just using a cheap bench supply, along with an iPod (since no volume control and line out levels are way too loud) and some beat-up Grado SR-325s (not gonna use the good phones until I'm sure the DC level is stable). Not the best for testing what this amp can do but so far it sounds at least as good as my HeadAmp V2, even with all the alligator clip connections.

 Here's a photo of it on the work table. As you can see from the PS readout, both channels together draw about 0.9A@30V, a little over 50W. The heatsinks are hot enough that I can only touch them for a second or two.


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## kevin gilmore

current draw should be 300ma per channel, 600ma total. 
 900ma is a bit much, should work fine with enough heatsink.

 You can lower the resistance of the 100 ohm resistor in the
 second stage to lower the bias.


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## sft

del.


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## hadron

I don't know if lowering the 100 ohm is a good idea, won't that increase the current through the second stage transistors? They are fairly warm as it is. 

 Would increasing the current source 500 ohm resistors help? I notice that if both trimpots are lowered the current shoots way up, should work in the opposite direction as well. What is the ideal voltage across the bias LEDs?


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## rsaavedra

Here's the teflon tape treatment I'm applying to the boards, 3 layers. In the middle the aluminum angle with the holes, will attach both boards to just one long angle rail. To the right the HS-TWS heat sink:





 Some advice wanted though, this aluminum angle (from Home Depot) is just 3/4 x 3/4 x 1/8". Should the leg that is in contact with the heat sinks better be much larger, or does it look like enough for sufficient contact and heat dissipation?

 Here a couple more pics:


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## kevin gilmore

Increasing the 500 ohm resistors also works. You can make them 1000
 ohms each and put in both trimpots, then set the bias at what you want.
 Either way works. Yes the transistors in the 2nd stage run warm. I've
 had my unit on continuously since i built it, so evidently there is no problem.

 You would be very surprised how nice it sounds into efficient speakers.
 Klipshorns for example.


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## rsaavedra

The items I got for 7815 and 7915 are the following:

 7815: LM78L15ACZ
 7915: LM320LZ-15

 I noticed from Strohmie's and Hadron's pictures that it seems the orientation of 7915 can be reversed with respect to 7815. I have no idea how these ones I got should be oriented, any help is highly appreciated. Thanks a bunch!
 Cheers,
 Raul


----------



## strohmie

You have 78L15s and 79L15s, which are what the two of us have as well.

 See the attachment for a view of the pin-out on the 7815, 78L15, 7915, and 79L15 for a better idea of why the orientation is changed for the 78L15s on our boards. You can see that the 79L15 vs. 7915 have the same pinout, while the 78L15 has to be reversed from its standard orientation to work on the board.


----------



## rsaavedra

Thanks a lot Jason!!! I see then, using TO-92 packages 7915 definitely has to go reversed with respect to 7815.


----------



## kevin gilmore

some quick pics

http://gilmore.chem.northwestern.edu/dynofront.jpg

http://gilmore.chem.northwestern.edu/dynoback.jpg

http://gilmore.chem.northwestern.edu/dynomiteps2.jpg


----------



## sft

some pics, too 
	

	
	
		
		

		
			





http://home.pchome.com.tw/home/sunsh...7/dynahi01.JPG
http://home.pchome.com.tw/home/sunsh...7/dynahi02.JPG

 Next: make two 24mm holes on front panel.
 Such work let me 
	

	
	
		
		

		
		
	


	




!


----------



## ahmose

sft, that looks mighty impressive, very nice work indeed. 
 Is that a parmetals case ?


----------



## chillysalsa

SFT: where did you get such nice casework?

 Is that that the Elma stepped attenuator?


----------



## kevin gilmore

The volume knob showed up today...

http://gilmore.chem.northwestern.edu/pg1.jpg
http://gilmore.chem.northwestern.edu/pg2.jpg


----------



## TrevorNetwork

Well, to those that have finished it. How does it compare to the original gilmore amplifier? DynaLo I believe. Has anyone compared it to a maxed PPA, with the diamond buffer, etc?


----------



## chillysalsa

KG: Regarding that potentiometer,
 What is that?
 Where did you get it?
 How does it compare with an Alps Blue? Ie: If it has a flatter impedance curve, where can I get one?


----------



## sft

I bought the case on a local DIY web. It's sold out. 
	

	
	
		
		

		
		
	


	




 Kevin, I want to know your opinion about PennyGiles VR and steppted attenuator. Which one(about souund character) do you prefer? Thanks in advance


----------



## intlplby

where can i find online information on making cases a lot like larocco's cases

 the ones that are custom sized alluminum panels on all four sides and are joined by tapped out aluminum corner blocks


 like the one here
http://www.quantum-thought.com/viewtopic.php?t=33


----------



## eric343

You really need proper machining equipment to make them; preferably a CNC mill.

 The cheapest way to get them is probably to custom-order one from LaRocco.


----------



## TrevorNetwork

Agreed. Larry will make custom panels, and enclosures. He's a great guy, and very good with his CNC. I do recommend calling him however.

 Cheers!

 Trevor


----------



## kevin gilmore

quote
 KG: Regarding that potentiometer,
 What is that?
 Where did you get it?
 How does it compare with an Alps Blue? Ie: If it has a flatter impedance curve, where can I get one? 


 Its a penny and giles conductive film pot with 24k gold wipers.
 I got it from a friend in britan.
 It blows away any of the standard pots.
 The price blows away any of the standard pots too.
 I will have a usa quote in a few days.
 About $400 each.


----------



## sft

Quote:


  Originally Posted by *TrevorNetwork* 
_Well, to those that have finished it. How does it compare to the original gilmore amplifier? DynaLo I believe. Has anyone compared it to a maxed PPA, with the diamond buffer, etc?_

 

Since I've not finished my dynahi and dynomite, I just say i prefer Dynamid(Balaced Bridged Gilmore) to maxed PPA. My wife too.

 source: TASCAM, Modded CardDeluxe, Benchmark DAC-1
 maxed ppa: steps, DB(PPL,GM), laddered stepped attenuator.
 headphone: HD650/w balanced Zu, OEHLBACH(for PPA)


----------



## rsaavedra

Where did you guys order your 2sc2705's? Having trouble finding them now.


----------



## Jupiter

MCM and bdent have 2sc2705 in stock.


----------



## hadron

$400 for a pot, ouch. The 40 step TKD stereo attenuator that I got for $250 from Percy Audio a while back, and never got around to using until now, seems like a good deal suddenly.

 Kevin, how good is that pot in comparison to a stepped attenuator, esp. one with a large number of steps like the TKD?


----------



## intlplby

so what value did every determine was best for the elna stepped attenuators

 10k, 25k or 50k?


----------



## TrevorNetwork

Sweet! I just ordered the two PowerOne PSU's, and it turns out that allied's warehouse is in Manitoba! I got 2 day purolator courier shipping for $12 CAD. 
	

	
	
		
		

		
			








 Oh, and can someone mail me a single 2SA1358? My source only had 7 (d'oh!) 
	

	
	
		
		

		
		
	


	




 If so, please PM me.


----------



## rsaavedra

Quote:


  Originally Posted by *Jupiter* 
_MCM and bdent have 2sc2705 in stock._

 

Thanks Jupiter, placed the order in MCM.


----------



## rsaavedra

Quote:


  Originally Posted by *intlplby* 
_so what value did every determine was best for the elna stepped attenuators

 10k, 25k or 50k?_

 

I went ahead and purchased all the resistors for the Elna Ladder using 50k, whether that's best I really can't say.


----------



## kevin gilmore

quote
 Kevin, how good is that pot in comparison to a stepped attenuator

 It is unbelieveably good. Besides which it has infinite resolution. I find
 that for headphone use 32 or 24 step attenuators are not enough.
 40 is better, 64 would be good, what i really want is 128 or more, can't
 do that with a knob, you have to do it with sealed reed relays and
 a microprocessor. The P&G is absolutely the best thing you can get
 in a reasonable size. This is as good or better, price is way out of line.

http://gilmore.chem.northwestern.edu/volume1.jpg


----------



## sft

128 with 0.5dB resolution is great!
 Another solution requiers two knobs.(24 * 6 or 5)


----------



## rsaavedra

Quote:


  Originally Posted by *kevin gilmore* 
_I find that for headphone use 32 or 24 step attenuators are not enough. 40 is better, 64 would be good_

 

I'll first try the Elna alone and will see. If the resolution seems too coarse, then I'll add a gain switch. The Elna (24 steps) + a gain switch should correspond to 48 steps.


----------



## sft

A gain switch is helpful since the dynahi is capable of driving K1000.


----------



## intlplby

what would be the best way to go about wiring in a gain switch

 which resistor would be the one that would be switched and what values should be used

 if i have 2 elnas... would it be worth combining the two?


 would it be possible to get a group buy on the P&Gs


----------



## kevin gilmore

group buy?? 

 Contact this person who is the distributor for the usa.

 He has 7 of the 10k units left at a special price of $250 each.

 Dale Manquen at MANCO
 1694 Calle Zocalo
 Thousand Oaks, CA 91360
 (805) 529-2496
dmanquen@email.msn.com www.manquen.net


----------



## eric343

Quote:


  Originally Posted by *kevin gilmore* 
_The P&G is absolutely the best thing you can get
 in a reasonable size. This is as good or better, price is way out of line.

http://gilmore.chem.northwestern.edu/volume1.jpg_

 

So the wirewound is better than the P&G?

 ...at twice the price, it should be!


----------



## kevin gilmore

Every high quality amplifer needs a trendy knob.

 Here is mine.
http://gilmore.chem.northwestern.edu/dynaknob.jpg

 Been saving scraps of 24k gold from vapor dep. chamber for quite
 some time now. Melted and pour'd into a mold. This is as is right
 out of the mold, no polishing whatever. I'll probably leave it this
 way as i like the looks of it. 108.2 grams.

 Handling liquid gold at 1100 C is quite fun.


----------



## eric343

Leave it to Kevin to use a knob that's worth more than three times the value of the pot... ($1391.48) That is truly insane. I mean, wow...

 First amplifier that needs to be stored in a safe?

 Hmm... at first I thought the finish on the front wouldn't go, but you're right -- it probably works well with the similar finish of the paint on the chassis. Maybe turn some grooves into the sides on a lathe, to give it some shine? Mill or cut a pointer into the front surface?

 Or polish all of it, sand off the paint from the faceplate of the amp, and drip molten gold down over the surface...


----------



## kevin gilmore

I just spent 3 hours on this after casting it yesterday.

 When the professional machinists at work told me i had to anneal the
 gold after casting otherwise it would be absolutely hard as h*ll i figured
 they were kidding. Gold is soft right? Bend it with your hands right?
 Took 15 minutes on the lathe to put the main hole in, took 20 minutes
 to put the 4/40 hole in. Took 30 minutes to tap the hole. And the tap
 really did want to bind like crazy. With the recovery system i lost
 less than .25 gram of gold in the process.

http://gilmore.chem.northwestern.edu/dynaknob2.jpg

 damm 105 with no depth of field

http://gilmore.chem.northwestern.edu/dynaknob3.jpg

 now do i really want to spend a couple of hours making the gold screw
 or should i decide enough is enough and use a standard steel one.

 Finished weight 101.3 grams. Was aiming at 100 grams even.

 Still have about 150 grams of gold, 29 grams of platinum and over
 500 grams of silver to play with.


----------



## Iron_Dreamer

Kevin gilmore, ladies and gents, the grand master of audio overkill, but do we ever love him for it! 
	

	
	
		
		

		
		
	


	




 And I remember people going nuts over the $500 wooden knob, just wait 'till they get a load of the $1800 knob/pot combo on display here.


----------



## strohmie

I really have only one thing to say.

 Ri
 dic
 u
 lous

 Maybe try stocking up on that platinum, make yourself a chassis to match.


----------



## kevin gilmore

quote
 Mill or cut a pointer into the front surface

 Thats a great idea, i don't know why i did not think of that.
 Drill a hole and drop in a .25 carat diamond...
 Maybe a ruby.


----------



## chillysalsa

Sheesh, if you have so much of that gold and platinum laying around, you can send me some! Something tells me if Kevin built cars it would be like a Bugatti Veyron ($1million+, 1001 hp, and has a diamond imbedded on the speedo needle).

 I'm still trying to decide on a potentiometer, how would people compare the three in terms of sound & build quality:

 Alps Blue Velvet
 Alps Black Beauty
 TKD P2500 series

 I also like the infinite steps a pot offers...


----------



## kevin gilmore

http://gilmore.chem.northwestern.edu/dynaknobj.jpg

 which you like more, the ruby (.125 carat) or the diamond (.25 or slightly 
 bigger). The only emerald i have is way to small.

 Yeah i'm nuts. No reason to leave all this stuff laying around in a drawer
 someplace...


----------



## ipodstudio

Quote:


  Originally Posted by *kevin gilmore* 
_http://gilmore.chem.northwestern.edu/dynaknobj.jpg

 which you like more, the ruby (.125 carat) or the diamond (.25 or slightly 
 bigger). The only emerald i have is way to small.

 Yeah i'm nuts. No reason to leave all this stuff laying around in a drawer
 someplace..._

 

Hmm...you know that ruby would make a very cool LED type light....


----------



## intlplby

anyone else find it frustrating having to scroll and seek just to find what KG took a photo of.... i have no problems with preferring high resolution..... just crop out the extra space at least

 lol



 what did you use to cast the knob and did you pop it out before it was cool or did you wait for it to fully cool


 i think if you pop it out early and water shock it you get a much higher luster


----------



## kevin gilmore

coor's ceramic vessels. Poured from the main vessel in the oven into
 the form vessel, then cooled a fair amount, then into cold water where
 the vessel shatters away from the gold. I would have loved to have a
 centrifuge for this, which would have removed all the bubbles. Still it
 looks really neat.

 Just in case someone else out there is also nuts enough to try this
 I would like to say that doing stuff like this is very dangerous in many
 different and exotic ways. Unless of course you are a steel foundry worker, a
 dentist, or work for the us mint. Which is why i do stuff like this on
 the weekends when no one is around to argue with my safety methods
 (or lack there of). In the 35 years of doing insane things i have never
 been hurt, nor have i hurt someone else.


----------



## chillysalsa

One could have also just gold plated a cheap knob... but then... you wouldn't have the same sound quality. 
	

	
	
		
		

		
		
	


	




 Dr. Gilmore: 

 Have you noticed any sonic differences in running on the extremes of the class-A bias? Right now I have budgeted for a big heatsink to allow me to run a high current, it's worth it, right?

 Is a 50K pot suitable for running Grados with the amp?


----------



## intlplby

i think you should have made the mold with a signature KG on the front.... make it look like the face of a gold coin


----------



## kevin gilmore

I think the 18 watts of class A bias should be more than plenty for anything
 you would want to do. Certainly plenty for k1000's.

 The impedance of the input pot has nothing to do with the headphones
 you are going to hook it to. The P&G are 10k. Now if you have a cd player
 or preamp with tube outputs, the 10k may be a bit low. In which case
 50k or 100k is fine.

 I would love to make something that looks like an american eagle
 (the gold coin). There is a 250 ton press at work, but i would have to use quite a few favors to get the die made.

 I'm going to make at least one more knob, then maybe send it to larry for engraving. His mill might not have enough power for this however.


----------



## pabbi1

Well, if you are getting outrageous.... courtesy of the US mint.


----------



## sft

Quote:


  Originally Posted by *intlplby* 
_what would be the best way to go about wiring in a gain switch

 which resistor would be the one that would be switched and what values should be used

 if i have 2 elnas... would it be worth combining the two?

_

 

1)Rf, it's below output pad on the silkscreen.(parallel resisitor to change it's original value, if you use on-off-on switch, you get 3 different gains even.)
 2)No. In most situation, 24 steps is enough.
 K.G.'s 128 steps is an ultimate in stepped attenuator. 
 In fact, 24 steps with 1~1.5 dB resolution is very enough for a diyer.


----------



## ayt999

I stop reading this thread for a few days and now gilmore's made a pure gold volume knob. 
	

	
	
		
		

		
		
	


	




 nice.

 I think I like the diamond better than the ruby, seems to match the knob more.


----------



## strohmie

So if the Perreaux had the "dinky knob," what in the heck do we call this?


----------



## ayt999

Quote:


  Originally Posted by *strohmie* 
_So if the Perreaux had the "dinky knob," what in the heck do we call this?_

 

my vote goes for the "pimp knob."


----------



## Iron_Dreamer

Quote:


  Originally Posted by *ayt999* 
_I think I like the diamond better than the ruby, seems to match the knob more._

 

I agree, alex!


----------



## strohmie

Quote:


  Originally Posted by *ayt999* 
_my vote goes for the "pimp knob." 
	

	
	
		
		

		
			



_

 

It's gotta flow right with the "dinky"...how bout "pimpy" instead?


----------



## ayt999

Quote:


  Originally Posted by *strohmie* 
_It's gotta flow right with the "dinky"...how bout "pimpy" instead?_

 

I was thinking of that, but I thought it wasn't as smooth as the "dinky knob." might work though?


----------



## kevin gilmore

Its finished (except for the gem in the knob) and burning in now.
 Real pictures today when i get the whole thing home.

 Man have i turned into a slob
http://gilmore.chem.northwestern.edu/slob1.jpg


----------



## kevin gilmore

here you go, warning huge as usual


http://gilmore.chem.northwestern.edu/dynafront.jpg
http://gilmore.chem.northwestern.edu/dynaback.jpg
http://gilmore.chem.northwestern.edu/dynaamp.jpg
http://gilmore.chem.northwestern.edu/dynapower.jpg


----------



## TrevorNetwork

Hi Kevin,

 Great pics!


----------



## TrevorNetwork

More importantly, how does it sound? How does it compare with the original Gilmore dynamic dubbed Dynalo?


----------



## kevin gilmore

I promised myself i would not listen to it until after 72 hours of burnin.
 That did not last long. It sounds quite amazing. Noise floor very low.
 Have to wait till later tonight when things are quiet.


----------



## Edwood

Quote:


  Originally Posted by *kevin gilmore* 
_Its finished (except for the gem in the knob) and burning in now.
 Real pictures today when i get the whole thing home.

 Man have i turned into a slob
http://gilmore.chem.northwestern.edu/slob1.jpg_

 

LOL, a messy workstation is a productive one. 

 But yes, wouldn't we all prefer to be neat and tidy?
 Of course, the easiest way to keep things neat and tidy is to never use them.

 -Ed


----------



## TrevorNetwork

What are the best caps that can be used for the two electrolytics? It seems that the 50V/470uF blackgate standard is 16mm in diameter. I am not sure that would fit correctly. Should I be using a different series? Different brand? What is the best?


----------



## eric343

Quote:


  Originally Posted by *kevin gilmore* 
_Just in case someone else out there is also nuts enough to try this
 I would like to say that doing stuff like this is very dangerous in many
 different and exotic ways. Unless of course you are a steel foundry worker, a
 dentist, or work for the us mint. Which is why i do stuff like this on
 the weekends when no one is around to argue with my safety methods
 (or lack there of). In the 35 years of doing insane things i have never
 been hurt, nor have i hurt someone else._

 

A dentist?

 I'm curious, though... beyond the obvious danger of molten metal that can splash or pop, what are you referring to?


----------



## sft

Quote:


  Originally Posted by *kevin gilmore* 
_here you go, warning huge as usual

http://gilmore.chem.northwestern.edu/dynaamp.jpg_

 

Where to buy these emitter resistors ?
 I'm interested in the datasheet also.

 I always learn form your pics. Thanks.


----------



## kevin gilmore

The black gate caps should fit, but it might be tight. I already do not
 remember what i used. What is the pin to pin on the BG?

 dentist... How do you think they cast gold inlays and bridges...
 I have an old time dentist that still does that kind of thing in his
 office. Although many these days just take the mold and ship it out.

 Safety? Lets just say that my definition of safety may be different
 from others, especially the research safety boys which have been
 on my case a number of times. As long as i don't get hurt, or hurt
 someone else, or burn the building down... And believe me, liquid
 gold really likes to start a fire. Melts right thru transite.

 Those are titanium emitter resistors. As far as i know you are not
 going to find them anywhere. They are part of my personal stash,
 more than 30 years old, better than .1% and very quiet.

 So i should have got some sleep last night from working (ahem) all
 weekend. That is not what happened. All i got to say is SWEET.

 I've decided to build an anechoic chamber in the basement. Want
 to remove all outside noise. Say 6 foot cube on the inside with
 a comfy chair.


----------



## philodox

Quote:


  Originally Posted by *kevin gilmore* 
_I've decided to build an anechoic chamber in the basement. Want to remove all outside noise. Say 6 foot cube on the inside with a comfy chair._

 

Lol, taking it to the next level yet again.


----------



## TrevorNetwork

I have received the power supplies, and such for my dynahi, however I am lacking two things; one of the 2SA1358's, and the appropriate bracket to attach my heatsinks to the opamps. However, if I purchase 16 small heatsinks with the small nut, bolt, and washer kits will that suffice for temporary cooling? Will not having one of the 2SA1358's affect the circuit in a serious manner?


----------



## kevin gilmore

quote
 However, if I purchase 16 small heatsinks with the small nut, bolt, and washer kits will that suffice for temporary cooling?

 I doubt this will work. It will get way to hot, way to fast.

 Will not having one of the 2SA1358's affect the circuit in a serious manner?

 Yes it will. Unless you build it with only one for each driver and change
 the 300 ohm to 150 ohm.


----------



## TrevorNetwork

Thanks for the quick response Kevin. Looks like I'll be waiting for the brackets. 
	

	
	
		
		

		
			





 I am hoping to get the needed 2SA1358 soon. My local shop ran out of them.


----------



## eric343

Quote:


  Originally Posted by *kevin gilmore* 
_Safety? Lets just say that my definition of safety may be different
 from others, especially the research safety boys which have been
 on my case a number of times. As long as i don't get hurt, or hurt
 someone else, or burn the building down... And believe me, liquid
 gold really likes to start a fire. Melts right thru transite._

 

 Liquid metal in general... try using some thick concrete instead of transite. Or put the transite over the concrete... Quote:


 So i should have got some sleep last night from working (ahem) all
 weekend. That is not what happened. All i got to say is SWEET.

 I've decided to build an anechoic chamber in the basement. Want
 to remove all outside noise. Say 6 foot cube on the inside with
 a comfy chair. 
 

"The Headphone Pod"

 Give it a gull-wing door that's hydraulically activated, and a red light that goes on when you're inside...


----------



## chillysalsa

Exactly! A headphone Pod!

 I guess we all know what Darth was doing in there!





 He couldn't put the cans on over his helmet! 
	

	
	
		
		

		
		
	


	




 Now....

 Will someone care to expand on how to match a potentiometer to the amp?

 I know it has to do with the output and input impedance of the source and amp respectively...

 so when applied to the Dynahi, what is a good pot value for, say, a source with 100 ohm output impedance? What if the source has a high 1K impedance? 47K? How can I calculate the optimal match?


----------



## kevin gilmore

quote
 Will someone care to expand on how to match a potentiometer to the amp?

 Well i do things a little differently. For this amp i use the nexgen 75 ohm
 chassis connectors which inside the amp connect to 75 ohm cable which
 terminates at the pot 75 ohms to ground. The pot in this case is nominally
 20k. The output of the pot goes to the amplifier and the 10k resistor to
 ground at the amp is removed. Also because the P&G pot does a hard
 switch to zero, i insert a 100 ohm resistor in series with the pot to the
 amplifier. Almost all pots do not do a hard switch to ground and the
 extra resistor is not needed. Outside the amp to the preamp will
 be some new 75 ohm cable (once i get it) terminated appropriately.
 This of course only works if you have a preamp with less than a 75 ohm
 output impedance.

 The P&G pots are almost 20% low with respect to resistance, not sure
 why. The 20k pot is actually 16.8k and the 10k pot is about 8.9k.

 Now if you have a source with a 1k output impedance, then you should
 probably pick between 10k and 50k pot. If you have a source impedance
 of 47k, then you should pick between 50k and 100k. But certainly not
 more than 100k or you will introduce extra noise into the system.

 quote
 "The Headphone Pod"

 Actually looking around work i got this idea. Start with a lindgreen
 screenroom. Really well built and all copper. Nice swinging door.
 Now start applying layers of sonex on the outside, layer by layer
 until it is quiet enough. Not only will it be silent but the aliens won't
 be able to beam their subliminal messages into your head.
 OOH WE OOH


----------



## eric343

Quote:


  Originally Posted by *kevin gilmore* 
_Actually looking around work i got this idea. Start with a lindgreen
 screenroom. Really well built and all copper. Nice swinging door.
 Now start applying layers of sonex on the outside, layer by layer
 until it is quiet enough. Not only will it be silent but the aliens won't
 be able to beam their subliminal messages into your head.
 OOH WE OOH_

 

Then it's not an anechoic chamber, it's a soundproof room... anechoic chambers have that funky foam on the inside to prevent sound from reflecting off the walls. Or so I've been led to believe by movies and pictures in Stereophile of speakers under test...


----------



## pabbi1

Quote:


  Originally Posted by *eric343* 
_Then it's not an anechoic chamber, it's a soundproof room... anechoic chambers have that funky foam on the inside to prevent sound from reflecting off the walls. Or so I've been led to believe by movies and pictures in Stereophile of speakers under test..._

 

I can verify that... we used anecholic chambers at TI (now Ratheon) to test military radar. Absolutely all sound is absorbed, even yelling at the top of your voice - spooky. Absolutely zero reflected sounds, and everything is absorbed. This sounds a little more like Tempest Mod spec (Secret / TS level access areas).

 And, can anyone else see Dr Gilmore lighting a grill with liquid O2?

http://ep.llnl.gov/msds/Chem120/lox-oxidation.html


----------



## eric343

Hmmm... yeah, definitely. Though, since LOX has already been done, I could imagine him lighting the grill from a distance via high-power RF. (He's already got experience lighting stuff on fire with RF, if I recall correctly.)

  Quote:


 WARNING: an ignition source, such as a lit cigarette or one glowing coal, must be present before pouring on the LOX. If charcoal is PRESOAKED in LOX first, an explosion will result. One briquette presoaked in LOX is approx equiv to 1 stick of dynamite. 
 

Wow. Now I know what to use when I next have to remove a tree stump...


----------



## TrevorNetwork

Back on topic guys. 
	

	
	
		
		

		
		
	


	




 Let's get some impressions here! I am sure many have finished it already. Mine will be done as soon as I get the bracket, and missing transistor 
	

	
	
		
		

		
		
	


	




 probably about a week or so. Believe me when I say I will be giving a full run down of this amp within 3 days of it being finished. It will be compared to the heavily modded Sugden, maxed PPA, and gilmore dynamic.


----------



## rsaavedra

Mine will be done as soon as I get back to Ivan-beaten Pensacola, and the mail delivers the items I last ordered, and I can install them. Right now am in New Orleans at some friends' house, waiting for electricity to come back to my apartment in Pensacola. This weekend I'll do the soldering of all the resistors on the Elna (brought all that with me), and will continue on the boards, mostly the heatsink assembly. But my Dynahi will have to wait at least couple more weeks to see the light in full.


----------



## sft

Quote:


  Originally Posted by *TrevorNetwork* 
_What are the best caps that can be used for the two electrolytics? It seems that the 50V/470uF blackgate standard is 16mm in diameter. I am not sure that would fit correctly. Should I be using a different series? Different brand? What is the best?_

 

 Quote:


  Originally Posted by *kevin gilmore* 
_The black gate caps should fit, but it might be tight. I already do not
 remember what i used. What is the pin to pin on the BG?_

 

The BG can fit. The diameter is 16mm so it's tight. the pitch is 7.5mm.

  Quote:


  Originally Posted by *kevin gilmore* 
_Those are titanium emitter resistors. As far as i know you are not
 going to find them anywhere. They are part of my personal stash,
 more than 30 years old, better than .1% and very quiet._

 

That's too bad...

 I've installed low inductance, low temperature coefficient and quiet emitter resistors in my dynahi. It sounds great.


----------



## chillysalsa

sft: 
 Which brand and where did you source the low inductance / temperature coeff resistors? Thanks!


----------



## sft

It's custom-built.

 --------------------------------

 FYI: http://www.diyaudio.com/forums/showt...p?postid=70608

 The old Holoc H4 (non-magnetic) seems to sound pretty good. I've bought 64 * Holoc H4 20R for my next project-dynamight.

 ------------

 One interesting thing: the knob on panel is hot(warm) since I attach heatsinks to the chassis.

 I really want to hear K1000 powered by the monster.


----------



## chris719

Beware, the 1/2 watt holcos have leads that are too thick to fit into the holes on the dynahi pcb. Learned this the hard way...


----------



## sft

Thanks, chris719.

 I have a grinder, so it's OK.


----------



## kevin gilmore

After everyone is done i'll take suggestions and make modifications
 to the current board layout for the next round. Already on the list
 are moving the one regulator to the right a little to give the trimpot
 more room, and bigger mountings for the caps.

 This project is going to be one of the most popular ever i think.
 Just wait till you hear this.


----------



## TrevorNetwork

Kevin,

 Although I already have a thread asking, what is the use of AuriCaps? Are they snake oil? Do they have a use in the Dynahi design? Do you feel the 470uF/50v BG are appropriate for use as stated by SFT?

 Trevor


----------



## pabbi1

Except for the most extreme builders, what is the mean final cost?


----------



## kevin gilmore

quote
 Although I already have a thread asking, what is the use of AuriCaps? Are they snake oil? Do they have a use in the Dynahi design? Do you feel the 470uF/50v BG are appropriate for use as stated by SFT?

 I use the illinois capacitors. As far as i can tell for power supply use they
 are absolutely the same, physically smaller and a whole lot less expensive.
 There are no caps in the signal path like there would be in virtually all
 tube stuff (like the carlo modifications)

 Black gates (while they are still available) and cerafines are really nice
 bulk power supply caps. But they are not that much better than the
 competition for this purpose.

 For blue hawaii use black gate power caps cannot be beat. They are
 however way out of line pricewise.


----------



## Pars

Quote:


  Originally Posted by *kevin gilmore* 
_quote
 Although I already have a thread asking, what is the use of AuriCaps? Are they snake oil? Do they have a use in the Dynahi design? Do you feel the 470uF/50v BG are appropriate for use as stated by SFT?

 I use the illinois capacitors. As far as i can tell for power supply use they
 are absolutely the same, physically smaller and a whole lot less expensive.
 There are no caps in the signal path like there would be in virtually all
 tube stuff (like the carlo modifications)

 Black gates (while they are still available) and cerafines are really nice
 bulk power supply caps. But they are not that much better than the
 competition for this purpose.

 For blue hawaii use black gate power caps cannot be beat. They are
 however way out of line pricewise._

 

Kevin,

 Where do you get your Illinois caps at? Do they sell directly to you or do you get them thru some distributor? I was trying to get the ultrafast 5uf ones that you had spec'd for the original Dynamic, but they appear to only deal in large volume. Now that we no longer do our own manufacturing where I work, fat chance on approaching them from that angle.

 Chris


----------



## kevin gilmore

illinois caps available here
http://www.vacuumtube.com/capacito.htm

 and probably many other places.

 I get them direct. It is unlikely you would be able to do the same thing.


----------



## chris719

Well, I've finished mine, for the most part... Ran into one problem, I get a low level hum when I use my W2002s, was not audible on HD600 but is quite annoying on the AT's. Any ideas? Also, one channel takes a while to get the DC offset down to acceptable levels, I used the trimpot on the right but can't make it any better, would the left socket allow me to further adjust?


----------



## rsaavedra

Inner circle of the Elma completed, here's a pic when I was about to apply the last soldering points:


----------



## kevin gilmore

low level hum is typically an input wire too close to a power transformer.
 Input wiring needs to be shielded.

 Dc drift during the first minute may be a power transistor that is slightly
 loose on the heatsink. You can remove the opamp from the socket and
 adjust the pot for zero and then the servo should keep the thing
 under 3 millivolts during turn on from cold with the output less than 1mv
 after a minute.


----------



## rsaavedra

Elma completed, here couple o'pics:


----------



## TrevorNetwork

Looks great Rsaavedra! 
	

	
	
		
		

		
		
	


	




 I wish I had gotten in on that group buy! I'll be using an Alps Blue Velvet until I am able to obtain something better.

 Cheers!

 Trevor


----------



## rsaavedra

Thanks Trevor! I had to correct my postings, the actual brand name is *Elma* and I have been writing Elna.


----------



## TrevorNetwork

Well, we have pics from Hadron, SFT, and KG, what about the rest of you? 
	

	
	
		
		

		
		
	


	




 I'll be posting pics as soon as I have the heatsink brackets. That's all I'm waiting on. I'm dying to hear this amplifier. This weekend or perhaps two weekends from now there is going to be a PPA-X vs. modded Sugden vs. Dynahi showdown in Seattle.


----------



## TrevorNetwork

ok guys, I'm trying to get 'er working however. I have one big question:

 I have two powerone psus. the power one provides a +V, and a -V. The differential across them is +30V. Each channel has a place for +30V, -30V, and ground. However, the PSU's do not provide a ground. Do I hook the +v to +30, and the -v to -30, and leave the ground alone on the dynahi? please answer soon, it's late as heck, and I want to hear this thing! 
	

	
	
		
		

		
		
	


	




 Trevor


----------



## TrevorNetwork

somebody? anybody?


----------



## ayt999

Quote:


  Originally Posted by *TrevorNetwork* 
_I have two powerone psus. the power one provides a +V, and a -V. The differential across them is +30V. Each channel has a place for +30V, -30V, and ground. However, the PSU's do not provide a ground. Do I hook the +v to +30, and the -v to -30, and leave the ground alone on the dynahi? please answer soon, it's late as heck, and I want to hear this thing! 
	

	
	
		
		

		
			



_

 

good luck with that Trevor. hope I was somewhat helpful.


----------



## sft

NO.


----------



## sft

FYI


----------



## TrevorNetwork

Yeah, I managed to figure out the wiring bit. However, in my tired state I made an error. I connected +v to the left sense lead on one of the power supplies. Although everything measured fine, when I attached the load (headphones) there was a spark, and a resistor cracked in half on the miswired psu. The voltage between +V and -V on that PSU is now ~45V, and is not adjustable. However, the voltage adjust pot does adjust the voltage between +V, and the left sense lead. Arghhh... very frustrating. 

 I checked the resistance on the good psu on the two resistors between the +V, and -V, and their associated sense, and received 10ohm on the left (+v) side, and 10kohm on the right (-v) side. However the color code is very odd (blue/green, grey, gold, gold) on both. Yet they measure differently (?) Anyway, I'm very not impressed, and I hope I did not blow out either of the dynahi boards. I am not sure how to troubleshoot the PSU, although I suspect (hope?) that it's something minor. 

 Well, it's 4:00am, and I have to be up in a few hours. ****** end to this night...


----------



## kevin gilmore

wire +V to + sense, and -V to - sense and don't worry about
 the sense resistor. You probably cannot measure that resistor
 in circuit and get the correct value. The supplies come apart easy
 and you probably should replace the resistor when you have a chance.


----------



## TrevorNetwork

omg teh bass


----------



## kevin gilmore

quote

 omg teh bass 

 Now do it again in full valley speak.


----------



## TrevorNetwork

I'll have some impressions a bit later. I'm just cleaning up the psu section. For my initial (3-4 hours) impression I believe Sega said it best:

 WELCO
 METOT
 HENEX
 TLEVEL


----------



## rsaavedra

Quote:


  Originally Posted by *sft* 
_FYI 
	

	
	
		
		

		
		
	


	






_

 

Is that the same way the condor power supplies have to be connected to the audio boards?


----------



## TrevorNetwork

<drooling> <drooling> <drooling>


----------



## sft

Quote:


  Originally Posted by *rsaavedra* 
_Is that the same way the condor power supplies have to be connected to the audio boards?_

 

I haven't the condor and powerone. If they are single-voltage like battery, then yes.


----------



## rsaavedra

Thanks for the feedback!

 Here some pictures of the "transistor sandwich" I finished just a few minutes ago. Decided to sandwich the transistors like that for better heat dissipation. Using just one of these relatively small angles under the transistors didn't seem enough to me. 

 The whole assembly goes as follows:

 Screw head
 Nylon nut (as washer on top)
 Top aluminum angle
 Heat sink compound
 Transistor
 Heatsink compound
 Bottom aluminum angle
 Teflon tape (3 layers)
 PCB board
 Normal washer
 Spring washer
 Nut

 I also applied heat sink compound between the angles and the heatsinks. One detail, notice I soldered the transistors after the sandwich was all assembled.

 These angles are easily obtainable in Home-Depot / Lowe's, so it's an easy and very affordable alternative to the large thick ones. The drawback: double the drilling, + extra drilling of the heatsinks:























 And here's how the amp is coming together so far. On the right (on a napking for visibility) RCA connectors, power inlet + switch module, fuse holder, blue power led, and the Elma attenuator. Missing parts still: headphone jack and volume knob (both in transit), and the signal path wire (still deciding). 








 The power supplies will actually go guts facing down as in the following picture. I attached them to one another using an angle and an extra flat piece of aluminum. Besides the heatsinks, this "wall" on the power supplies will provide extra shielding between the power side and the audio signal side of the amp:


----------



## TrevorNetwork

Is there a way to adjust the gain? Using my CDP, with a 50k pot I have about 1% movement.


----------



## kevin gilmore

You should use the line output of your cdplayer if it has one.
 Otherwise you can cut the resistance of the feedback resistor.
 Changing it from 2k to 200 ohms will cut the gain 10db.

 rsaavedra, i like the double heatsinking. Probably unnecessary, but
 pretty.


----------



## rsaavedra

Quote:


  Originally Posted by *kevin gilmore* 
_rsaavedra, i like the double heatsinking. Probably unnecessary, but pretty._

 

Thanks Kevin! I also wondered if it would be overkill. No one had objected to my using just one of those small angles after all. But I thought the second one could help dissipation a bit.


----------



## djwkjp

looks good so far, raul. i like the idea of using 2 angle brackets. what kind of case is that? it looks great.

 dan


----------



## rsaavedra

Quote:


  Originally Posted by *djwkjp* 
_looks good so far, raul. i like the idea of using 2 angle brackets. what kind of case is that? it looks great._

 

It's one of these: http://www.hammondmanufacturing.com/dwg25.htm

 I got the RMCS190313BK1, 17" x 13" x 3.5". Top and bottom panels are not too rigid though, planning to add some aluminum angles along those and the side panels inside for extra rigidity.


----------



## TrevorNetwork

rsaavedra,

 Looking at how much heat is created by my Dynahi boards, as well as their power supplies, I am not sure your dynahi will be stable. The dynahi boards alone create quite alot of heat.


----------



## rsaavedra

Quote:


  Originally Posted by *TrevorNetwork* 
_rsaavedra,
 Looking at how much heat is created by my Dynahi, as well as its power supplies, I am not sure your dynahi will be stable. The dynahi alone creates quite alot of heat._

 

I rather tend to agree with Kevin, that the sandwich scheme I used is probably a bit overkill. I think I'm using the same heatsinks you are using. Why do you think my heat sinking and dissipation is insufficient? 

 Notice, half the top and bottom panels of the case are vented. I'm planning to install them so that let's say bottom has vents in the back half, and top panel has the vents in the front half. So besides the probably overkill heatsinking, air circulation will be plenty.


----------



## TrevorNetwork

My dynahi and power supplies are currently operating out in the open, without enclosure. They get quite warm. At very least, I suspect your case could be hot to the touch. The believe the heatsinks will have to be outside the case, or alternatively, you will require a fan to pull out the heat.


----------



## rsaavedra

Quote:


  Originally Posted by *TrevorNetwork* 
_My dynahi and power supplies are currently operating out in the open, without enclosure. They get quite warm. At very least, I suspect your case could be hot to the touch. The believe the heatsinks will have to be outside the case, or alternatively, you will require a fan to pull out the heat._

 

I see. Once I try it, I'll make sure to have the amp with plenty of breathing room. If it gets too hot, I'll first try drilling rows of holes on the panels all the way right below and above the heatsinks. I suspect that should be sufficient in case of the case getting too hot. But if still too hot, then I'll change the case and arrangement to have heatsinks outside. In any case, no way I'll have a fan in this amp, that would be blasphemy!!! 
	

	
	
		
		

		
			





. When listening to music at home, whether through speakers or headphones, I even turn off the air conditioner and refrigerator to avoid any background noises as much as possible. (I'm one of the ones who couldn't put up with the Azur 640C because of its transport noise)


----------



## philodox

Quote:


  Originally Posted by *rsaavedra* 
_I even turn off the air conditioner and refrigerator to avoid any background noises as much as possible._

 

ok, thats crazy


----------



## gsferrari

You can get noiseless PC fans and install them in the case. Passive water cooling is also an option. 

 Just leave her topless and let er rip


----------



## chillysalsa

I'm not so concerned about a case that is warm. My plans include bolting the heatsinks to the floor of the case and letting the chassis be an extension of the heatsink. I am also using BEEFY heatsinks... will post pictures when I start the build (December vacation project!)... sorry to tease you. No time, and I'm partly waiting for the silver wire from the group by for signal connections.


----------



## rsaavedra

Quote:


  Originally Posted by *philodox* 
_ok, thats crazy 
	

	
	
		
		

		
		
	


	


_

 

Yeah it is a bit 
	

	
	
		
		

		
		
	


	




 Well, in defense of my sanity, the apartment where I live is relatively small, the neighborhood is very very quiet at night, and my appliances quiet loud in their own way. Whenever listening to music, either the central A/C or the fridge motors kicking in are almost little explosions of noise in their own way. Not referring to the electrical noise in the electricity feeding the audio components (something to avoid anyway), I mean perfectly audible noise in the room. Very distracting and annoying when you are listening specially in very quiet conditions. Because of that, I started turning them off before listening, not to have to stand up in the middle of a session, and I started doing the same when watching DVDs also.


----------



## philodox

Oh, I understand that, its just that for me my comfort [airconditioning] and my food not rotting [fridge] are fairly important considerations as well


----------



## rsaavedra

Quote:


  Originally Posted by *philodox* 
_Oh, I understand that, its just that for me my comfort [airconditioning] and my food not rotting [fridge] are fairly important considerations as well 
	

	
	
		
		

		
		
	


	


_

 

LOL, no but I don't keep them off for too long, almost always less than 2 hours. And I mostly do this late at night when it's really quiet. If it's not that quiet it's not worth turning them off.

 In any case, definitely no fans for my amp.


----------



## rsaavedra

After some requests of part lists, here the list of things I got and the sources:

 Audio board components from BCBill's list:
http://members.cruzio.com/~billsiegmund/

 From www.mouser.com:
 Knob (part# 450-6017)
 Headphone jack (# 550-NMJ6HCS)
 Case (546-RMCV190313BK1)
 (After Trevor's comments, explore alternatives to this case)

 From http://www.alliedelec.com:
 Power inlet with switch (# 509-3110) 
 Power led (# 566-1031)
 Fuse holder (# 798-0019)
 Condor power supplies (# 744-5020)

 From http://www.surplussales.com/Heatsinks/HeatSink1.html
 Heatsinks HS-TWS

 From http://www.moon-audio.com/
 Pair of Cardas Female RCA's (GRFA S Thick)
 18awg 3 conductor shielded silver plated wire (for power wires)
 Cardas roll of Silver solder

 From Home Depot and Lowe's
 Aluminum angles, washers, bolts, and nuts

 From a local computer parts store:
 Silicon based heat sink compound

 From groupbuys at Headfi:
 Quail power cord
 Elma Ladder attenuator
 Dynahi pcb boards

 Still to buy:
 22-20 awg solid silver wires (Kevin's recommendation) for signal path


----------



## pabbi1

What would you guess your total expenditures to date are?


----------



## rsaavedra

Quote:


  Originally Posted by *pabbi1* 
_What would you guess your total expenditures to date are?_

 

(09/29/2004) I estimate close to $500.

*(Update 09/30/2004) Currently a more accurate estimate is $600 (see this post).*


----------



## gsferrari

ATTENTION :-


 Anybody considering this project please send me a PM. If there are enough people interested we might be able to organize a group buy for parts and save some $$$ this way.

http://www5.head-fi.org/forums/showthread.php?t=87506

 Cheers!


----------



## rsaavedra

Tested the power supplies independently, and then connected them to the audio boards for the first time to do the DC offset measurement between output and ground. Did this with the two boards connected, not each one separately. Also, I don't have the trimpots yet on the boards. Measured 15.8 volts from one board, and 15.6 v from the other. 

 Left them powered for approximately 20 seconds each time. At the beginning the meter read around 25 v, then after a few seconds it starts dropping till it stays stable at 15.x volts. Same on both boards, so the two are behaving consistently. 

 But in general, do these measurement suggests everything seems ok so far? (Taking into account the trimpots are not yet installed) Here pics of the measurements.













 I placed everything inside the case not accidentally, but just in case anything would blow 
	

	
	
		
		

		
		
	


	




 Fortunately nothing did. Also, for the short periods of time they were powered, there was absolutely no heat. Neither in the audio boards, nor in the power supplies, which was odd. Fortunately also, absolutely no humming from the power supplies.


----------



## TrevorNetwork

As for the heat, give it a bit of time.


----------



## chris719

DC offset of 15V is almost 1000 times too high. I'm hoping that you mean 15 mV but if not there is definitely a problem.


----------



## kevin gilmore

Sure looks like that meter is on the 20 volt scale. Something
 is very wrong.

 First you should never ever do this with clip leads, something will
 move for a fraction of a second and you will have lots of blown up
 parts.

 Second, your power supplies are probably not wired right. Make
 sure that you can measure +30 and -30 at the power connector.

 Sure sounds like the -30 supply is not working, or not hooked up correctly.


----------



## TrevorNetwork

Agreed with Chris. Mine was ~14mv originally. I then utilized the trim pot to make it 0.00 on the right, and ~0.10 on the left. I suspect you mean 15mv.


----------



## rsaavedra

Meter is at the 200 position actually. But at that same position I measured 28.1 and 28.2 volts (they are rated at 28v, not 30v) from the power supplies.

 I wired the power supplies to the boards following this diagram:






 Will check again tonight, but just in case, can somebody suggest which are the parts that could most likely get blown?

 Also, if possible, some easy diagnostic on board procedures to check whether they are blown (other than the resistors of course which I can easily check, but I doubt they would get blown easily, or would they?).

 Or in general, some other possible tests to narrow down sections that might be in trouble?

 One comment that might help identifying a potential problem for you guys. The red LED's to the right of the boards were much brighter than those to the left. Not sure if this can be easily seen in the pictures though, since the left LEDs are half covered by the capacitors. But those were clearly less bright than the right ones.

 About not using the alligator clips, should I solder everything already? If not, what alternatives are there? But actually, I doubt anything moved when I did this test. The power was coming from a switched surge protector. After everything was connected I only turned the power switch of that surge protector to on, and then took a pic. Then off, connected for the other board and did the same again. But indeed, if a fraction of a second minor unnoticeable movement might blow up things, well... hope I wasn't too unlucky.


----------



## rsaavedra

Quote:


  Originally Posted by *kevin gilmore* 
_Second, your power supplies are probably not wired right. Make sure that you can measure +30 and -30 at the power connector._

 

Checked the power supplies again separately, they are both working fine. Also, when connecting them in series, I get the expected 56.3 ~ 56.4 v.

 Checked the whole testing wiring again, and it is true to the sketch above. Yet, at the power connectors on the boards I measure 28.1 v from positive to ground, but only -1.5 v from negative to ground


----------



## kevin gilmore

You may have wired to the sense lines instead of the V+ and V- lines.
 Or 1 channel is pulling way to much current (like a shorted electrolytic)
 and the minus supply is shutting down. Hook up just one channel and
 see if that works.

 Edit: the picture seems to show the sense lines wired to the V+ and
 V- lines, so something is pulling too much current.

 If you are using the L series regulator one of them needs the position
 flipped.


----------



## rsaavedra

Quote:


  Originally Posted by *kevin gilmore* 
_If you are using the L series regulator one of them needs the position flipped._

 

Thanks so much Kevin, oh boy I think that's it. I now remember exchanging some PM's about some reversals needed, and I think I messed it up anyway. After that comment of yours above I went back in this thread and compared carefully my board to Strohmie's picture in this post. I bet he has things the right way, and therefore, I soldered both my 7815 and 7915's reversed. Here's my board:






 Gee, this is bad. Can you tell more or less how damaging was this for the components in the board? Would it be ok to just unsolder them and resolder them (rather new ones) the right way and try? Or might some important things on the boards have gone kaput because of this silly mistake of mine? Gee I definitely shouldn't solder too late at night.


----------



## TrevorNetwork

This is exactly why I didn't use the smaller "L" reg's.


----------



## strohmie

Wait a sec, I'm confused. Is the orientation that I had in my original image incorrect, or is it the orientation you have in that image incorrect? Because if it's my fault I'll pay for the new components you need.

 edit: oh, I think I see the problem now.


----------



## rsaavedra

Quote:


  Originally Posted by *strohmie* 
_Wait a sec, I'm confused. Is the orientation that I had in my original image incorrect, or is it the orientation you have in that image incorrect? Because if it's my fault I'll pay for the new components you need._

 

No you or your images are not at fault whatsoever Strohmie, thanks for the gesture though. Only now I checked mine with your image carefully, so yours didn't influence my messing things up, don't worry really. It was all a silly mistake of mine, despite warnings I got about this specific detail. Your image I believe must be showing the correct way to place those components, I only linked to it as a reference to the correct way to solder 7815 and 7915. I added the signs "wrong" to the image above which is my current board, your boards and your photo have them the right way I believe.


----------



## kevin gilmore

7815 across the front in ground out

 78L15 across the front out ground in

 7915 across the front ground in out

 79L15 across the front ground in out

 From the picture it looks like you got both in backwards
 which would explain the -15 supply sinking to -1.5v

 Current limited power supplys keep the magic smoke in.

 You should have put the opamp on a socket. Although the
 opamp is probably ok since one of the supplies was shorted the
 most it could have seen was 30 volts which it can take anyway.

 look here, and expand all the way
http://gilmore.chem.northwestern.edu/dynahif2.jpg

 I would unsolder the old regulators, and throw them away and
 put in new ones. Because if they are shorted, they will blow the
 opamp...


----------



## rsaavedra

Quote:


  Originally Posted by *kevin gilmore* 
_You should have put the opamp on a socket. Although the opamp is probably ok since one of the supplies was shorted the
 most it could have seen was 30 volts which it can take anyway._

 

This is a relief to read. So mostly the opamp was at risk then. Well I'm desoldering 7815 and 7915's, and will try these very same ones the right way. If measurements are decent I'll keep then at least for now, but I'm ordering new ones anyway. In the end, if I hear anything weird, I'll be replacing not only those, but also the opamps. Thanks a bunch Kevin for all the help!!
 Cheers,
 Raul


----------



## gsferrari

Raul - how far away are you from your first "listening" session with the amp?


----------



## rsaavedra

Quote:


  Originally Posted by *gsferrari* 
_Raul - how far away are you from your first "listening" session with the amp?_

 

Depends on how the components on the boards handled this blunder of mine 
	

	
	
		
		

		
			





 Just finished unsoldering/resoldering the 7815 and 7915's on both boards btw, will do the offset measuring now with much care to see how everything went. If ok, I guess before end of the week I'll have time to connect everything and listen.

 On a different note, just today I ordered 22 awg solid core, teflon insulated silver wires from www.homegrownaudio.com for the input signal path. For output signal path I think I'll go with 20 awg cardas copper wires, can't find 20 awg silver. The mix might be a good idea after all.


----------



## gsferrari

why not go 20awg ssolid copper all the way? 

 OK -slightly OT but maybe KG has something to say about this.

 Stranded vs Solid. IMHO Solid has almost no practical use because current is a surface phenomenon. Thats why you have skin effect. Wouldnt stranded wire be just as good as solid wire as long as it is high quality without frayed/broken strands? It will also be more flexible and easy to work with 
	

	
	
		
		

		
		
	


	




 Also - why silver? Just want to know why...

 Cheers!


----------



## rsaavedra

Silver is the metal with best electrical conductivity, that's why, copper is a second close though.

 After resoldering the 7815's and 7915's the right way, the boards seem to be working perfectly now. With much care I went ahead and did the test again using the alligator clips despite the danger. With the meter at the 200 position I measured zero offset from both boards. At the 2000m position, the offsets measured 6 in one board and -3 in the other. Not really sure if those are 60 and -30 or 6 and -3 mvolts respectively, but anyway, seems reasonable now I guess.

 Also, at the boards's power connector, + to ground measured 28.1, and - to ground measured -28.2 volts. And now clearly both leds light up with equal brightness. And despite the short time I kept the boards powered (probably 30 seconds for each picture; the measurements take a little while to settle, and also I had to take the pics), right after the second pic I turned off the surge protector feeding the psu's, and touched the aluminum angles and the heatsinks, they are clearly warm! It does look like it will heat up quite a bit. Here the pics:


----------



## gsferrari

what is the scale on your meter (what scale are you using to make that reading?) use the scale to arrive at the final value of offset voltage.

 Cheers!

 Like I said - wouldnt it make more sense to use hollow silver tubes instead of solid wires? I will ask this question in the cables/accessories section. Copper wire coated well with silver should also work well.


----------



## rsaavedra

Quote:


  Originally Posted by *gsferrari* 
_what is the scale on your meter (what scale are you using to make that reading?) use the scale to arrive at the final value of offset voltage._

 

It's the one that reads 2000m, I guess it suggest the readings are 6 mvolts and -3mvolts, but not so sure. After the hurricane I packed a bunch of stuff and my apartment is still a relative mess, I have it somewhere but can't find the little manual for this meter.


----------



## chillysalsa

Quote:


  Originally Posted by *gsferrari* 
_Like I said - wouldnt it make more sense to use hollow silver tubes instead of solid wires?_

 

 Tubes have much higher stiffness in bending compared to solid rods, and it presents a bit of a challenge to make thin sections in a tube: the extrusion process required to make a tiny tube is not easy, but thin wires are easy to make using a drawing process.

 Raul: what is the bias current you are running and approx. temperature rise of your heatsinks?


----------



## rsaavedra

Weird, made another set of measurements with the meter at the (V dc) 20 position, here the measurements do show a decimal point, readings are 0.01 and -0.01, so guess the actual offsets are approximately 10 mvolts and -10 mvolts? 

 About temperature rise no idea, don't have a thermometer to measure that. Measuring current between output and ground (not sure if that's the way to measure the bias current though), and meter at the (A) 20m setting, seems to take a long time for the reading to settle. Reading started at around 3.5 now after about 4 minutes reading is already going at around 0.60 but keeps going down. Heatsinks are warm, not the power supplies though.

 Update, after couple more minutes, current between ouput and ground is reading -0.03 and slowly oscillating sometimes down to -0.1, sometimes slowly back up to 0.1. Heatsinks are very warm to the touch, and I'm just touching the tips. Pressing the finger flat on the aluminum angle hurts very quickly. Power supplies are mildly warm now, and btw, now I do detect there's a minor hum in them. Have to get my ear close to them to hear it, but they do hum a tiny bit.

 Update 2: after about 10 minutes, the heatsinks are HOT. Turned off and on to measure voltage offset again, in the board that had 0.01 before, now most of the time reads -0.00, seldom jumping to -0.01. In the other board it remains stable at -0.01. Wonder if I can do without the trimpots.


----------



## rsaavedra

Found the manual for the multimeter (in my toolbox! duh). The 200m position is the most accurate for small voltages measuring a range of up to 200 milivolts. (2000m measures up to 2000 mvolts, or just to 2 volts, at 20 up to 20 volts, and so forth). 

 At that 200m position, and after maybe half an hour of this somewhat intermittent break-in, the voltage offset in bottom board now changes somewhat slowly between 2.2 all the way to -2.5 millivolts. In top board, it's between -0.3 and -4.2 millivolts. 

 Chassis of the power supplies remain just warm.
 Heatsinks are VERY HOT.
 Opamps, however, are not even warm. Wondering if that's a bad sign.


----------



## sft

The voltage drop across 20R is about 700mV.


----------



## philodox

Would 24 AWG silver wire such as that being purchased in the wire group buy be suitable? If not, I guess I could maybe trade some of my 100ft for some 20 AWG.


----------



## sft

I think it's fine but i've no experience of 24AWG silver wire.
 The ckt. of dynahi is very excellent.


----------



## rsaavedra

Followed Kevin's instructions to test that the voltage regulators are still ok. For this I had to short the inputs with ground (for less voltage variability), and then had to do the following:

 Leg 4 of opamps should have -15 v. On my boards I measured -15.29 v, and -15.17 v, so ok.

 Leg 7 of opamps should have +15 v. I measured +15.06 v, and +15.24 v, so ok too.


 Now as far as the trimpots, leg 6 (output) of the opamp ideally should be within +5 and -5 volts so as not to need a trimpot. I measure -6.01, and +2.90 on my boards. So I do need at least one trimpot, good I ordered 2 already.

 One other comment, the power supplies have voltage trimpots on their boards. Adjusting those, instead of 28.xx volts, both are now producing exaclty 30.0 volts.

 Again Kevin thanks much for all this info!


----------



## rsaavedra

This weekend I did some chassis work, connected power inlet, fuse holder, and RCA ins to the back panel. Now that I'm using the fuse holder to power the psu's, I'm realizing a standard Radio Shack 250 volt 1 amp fast blow fuse doesn't last more than a couple of power ons. Had the power supplies not connected to the main boards, so there was no load except the multimeter measuring voltage. I've burned 2 fuses already and both blew just at the third time.

 Update: fuse better be slow-blow, 1.5 or 2 amps.


----------



## gsferrari

Quote:


  Originally Posted by *rsaavedra* 
_Update: fuse better be slow-blow, 1.5 or 2 amps._

 

Wouldnt a 2A Fast Blow protect the electronics better? That is what I see in most of my amps.

 Cheers!


----------



## rsaavedra

Quote:


  Originally Posted by *gsferrari* 
_Wouldnt a 2A Fast Blow protect the electronics better? That is what I see in most of my amps.
 Cheers!_

 

Don't really know, Kevin told me they need to be slow blow ones. And in addition, that given the size of the psu's they'd better be 1.5A or 2A. Actually, since they are cheap I'm ordering a combination of types: 2A-slow, 1.5A-slow, and 2A fast.


----------



## TrevorNetwork

Has a PCB been created for the custom PSU? I believe SFT used a custom PSU.


----------



## rsaavedra

Quote:


  Originally Posted by *TrevorNetwork* 
_Has a PCB been created for the custom PSU? I believe SFT used a custom PSU._

 

AFAIK it has not been created yet.

 I must say can't wait for the trimpots and the silver wires to arrive. Have been having so much fun building this, can hardly wait to listen to it.

 This past weekend plus yesterday I spent some time doing lots of drilling. Back panel and bottom panel finished, front panel sort of. I'll sand it all down and apply some very dark lead (color) non-shiny paint. Now it got (when drilling it) some minor corner scrathes. For later I'm leaving some tweaks, like copper shielding the Elma attenuator area for instance. Here some pics:

 The moon-audio wires I got for DC power. These are 18 awg, silver plated, shielded wires. Everything that's not metal in it is teflon. Each conductor's casing is teflon, as well as the exterior white tape around the shielding. So no much concern about surrounding temperature for these. For AC power I'm using conductors from the Halloween powercord.






 First time front panel put together:





 Back panel, with RCA input connectors, switched power inlet, and fuse holder:





 Plenty of drilling for the back half of the bottom panel. Both for the bolts to hold the power supplies and main boards in place, and for ventilation. The raw of holes in the middle is right under one of the heatsinks.


----------



## Turing

rsaavedra:
 Will the boards not fit if you spin them 90 degrees so that the heat sinks are directly over the pre-drilled holes?


----------



## philodox

I think he wants the sinks to help shield the audio components from the PSU's.


----------



## rsaavedra

Both things apply. I wanted the heatsinks to shield audio boards from PSU's. But also, having the PSU's from front to back on the left, the audio boards can't fit from left to right.

 I thought about putting the PSU's left to right on the back of the amp, and then the audio boards in parallel from left to right in the front of the amp, with heatsinks facing the PSU's, so that heatsinks would still shield between psu's and boards. That way the heatsinks would actually stand on the border of the pre-drilled holes, which was good. But that way also the transformers of the right most PSU, and also AC power wires, would have ended up quite closer than I wanted to the input RCA's and the signal path. I prefered to put all AC power and transformers as much to the left of the amp as possible, and the input signal as far to the right as possible. Hence, audio boards's best placement was in the middle from front to back, with extra ventilation drilling required.


----------



## rsaavedra

Quote:


  Originally Posted by *sft* 
_6)Add 10K pot. Try and you will know which socket is right.
 Then trun the post until dc-offset near to zero._

 

Can someone provide more step by step details about that process? I got the trimpots today, how do I exactly know if I should use it on the left or right hand side of a board? Should I turn the trimpots to some specific (max) resistance between specific legs before installing them on that side of the board, etc.?

 I'm asking after having tried the trimpots on both sides, and with different initial settings, and then turning their little knobs many times both ways, with apparently no effect on the output voltage of pin 6 of the opamp.

 When using the trimpot, depending on which side I install it on, the voltage in pin 6 of the opamp seems to go either directly to 14.44, or -14.44 (without the trimpot it was -6.01), apparently regardless of what value I set the trimpot to initially, 10K, 7K, 3K, or 1K... Turning the trimpot clockwise or counterclockwise many many turns from that initial setting (to the point of even turning off that side's LED completely), the voltage in pin 6 of the opamp doesn't change a bit anyway, remains at 14.44 or -14.44.

 So what am I doing wrong? Can someone explain in more detail the process of bringing the DC offset of opamp's pin 6 down to (or closer to) zero volts by installing and then adjusting the trimpots?


----------



## sft

Oops! my wrong typing: trun the post->turn the pot.



 If the heat solution is good enough and the DC-offset 
 is small and stable, you needn't install both the pot and DC-Servo maybe, it's your choice.

 To Raul:
 1) Remove op27 or 5K beloing to Servo

 2)Measure the dc-offset, if it's negative then populate the pot in right socket.Trun the pot clockwise until you hear a click before populate it and You must plug pin 3 in the small circule position.

 3)measure again, the dc-offset should increse.Turn the pot unclockwise until the dc-offset increse to zero

 4)install dc-servo

 hope this is helpful.


----------



## rsaavedra

Quote:


  Originally Posted by *sft* 
_To Raul:
 1) Remove op27 or 5K beloing to Servo_

 

Thanks a lot sft, will remove the op27. I got sockets for them, and new op27's are in transit arriving maybe today.

  Quote:


 2)Measure the dc-offset 
 

Ok when the opamp is not there, how do I measure the offset? Is it the same way as if the opamp was there? E.g. output voltage between where leg 6 would be, and ground?

  Quote:


 If it's negative then populate the pot in right socket.Trun the pot clockwise until you hear a click before populate it and You must plug pin 3 in the small circule position. 
 

Ah weird, I've turned the pot both ways till I get 9.99K and 0K ohms between two of its legs, but never heard or felt any click. Will have to pay attention to that.

  Quote:


 3)measure again, the dc-offset should increse.Turn the pot unclockwise until the dc-offset increse to zero
 4)install dc-servo 
 






 By installing dc-servo, do you mean whatever I had removed for this, right? E.g. Either the opamp or the 5K resistor?


----------



## sft

Quote:


  Originally Posted by *rsaavedra* 
_Ok when the opamp is not there, how do I measure the offset? Is it the same way as if the opamp was there? E.g. output voltage between where leg 6 would be, and ground?_

 

measure the voltage between the output pad and ground.

  Quote:


 Ah weird, I've turned the pot both ways till I get 9.99K and 0K ohms between two of its legs, but never heard or felt any click. Will have to pay attention to that. 
 

It's a very slight click. You need pay attention to that. You can hear or feel it. It means you have reach the end.
  Quote:








 By installing dc-servo, do you mean whatever I had removed for this, right? E.g. Either the opamp or the 5K resistor? 
 

Yes.


----------



## rsaavedra

Thanks a lot sft! If I get the opamps and the replacement 7815 and 7915's today, I should be able to have the dc-offset adjusted finalized versions of my boards tonight.


----------



## rsaavedra

Quote:


  Originally Posted by *sft* 
_BTW, if the heat solution is good enough and the DC-offset 
 is small and stable, you needn't install both the pot and DC-Servo maybe, it's your choice._

 

In the other board, the offset I measured (with the opamp and 5K resistor installed though, maybe incorrect way to measure it) was +2.90 v. In principle I don't need the trimpot there since that's within +5 and -5 volts, but shouldn't I install it in that board anyway, so as to bring that offset as close to zero as possible?


----------



## chillysalsa

Shouldn't DC offset be in the < 5mV range with this amp?


----------



## gsferrari

I am sure thats what he is talking about 
	

	
	
		
		

		
		
	


	




 +/- 5V is a typo on his part...should be mV


----------



## philodox

This is a little off topic so if you think I should open another thread I will...

 Could you set up the Dynahi like a power amp with no volume control and make another box that just handles volume control and maybe source and/or destination switching similar to the headroom switchbox?

 I was thinking that you could have a box with an elma stepped attenuator, gain switch, 3 choice input selector and maybe a 2 choice output selector [for headphones and speakers]... with all the appropriate hookups on the back. That way you could use the attenuator with your headphone and speaker setups and switch between your sources. Would this be bad sonically for any reason and would it be hard to set up?

 EDIT: Raul answered my question in PM, so there is no need to reply. Thanks.


----------



## rsaavedra

Quote:


  Originally Posted by *chillysalsa* 
_Shouldn't DC offset be in the < 5mV range with this amp?_

 

I measured with the opamp connected. The output of the opamp is in volts, and with the input shorted to ground on the board, that voltage is supposed to be anything in the range of -5 to +5 volts (not millivolts) to not need a trimpot. This according to what Kevin once told me, or I should rather say, according to what I understood from what he told me 
	

	
	
		
		

		
			





. That measure having the opamp connected might be called just exactly that: "output voltage of the opamp having input shorted to ground". Most likely that shouldn't be called "DC offset", as I was calling it though, so there might lie the culprit of the confusion. (For sure I don't really know the true technical definition of DC offset).

 From sft's post I now gather, DC offset is measured (maybe with input shorted to ground?) measuring voltage between ouput of the amplifier (not of the opamp) and ground, having the opamp (the servo for that matter) disconnected or disengaged. Can someone please confirm whether this is correct?

 PS. Obviously this part of the assembly instructions needed more details on how to do every little step, especially for still e-diy newbies like me


----------



## gsferrari

So you're still NOT at the listening stage? 
	

	
	
		
		

		
		
	


	




 I am on rush mode ordering parts now...should have everything next week, furious building so that the amp will be ready in time for the meet...it will be great to judge two Dynahi's back to back!!

 Cheers!


----------



## rsaavedra

Quote:


  Originally Posted by *gsferrari* 
_So you're still NOT at the listening stage? 
	

	
	
		
		

		
		
	


	




 I am on rush mode ordering parts now...should have everything next week, furious building so that the amp will be ready in time for the meet...it will be great to judge two Dynahi's back to back!!

 Cheers!_

 

Not yet. Had to wait for the trimpots which arrived just yesterday together with the silver wire. Now waiting for the replacement opamps, transistors (78 and 7915), and fuses... (Edit) which btw didn't arrive today @#$%@$#%. Hoping for tomorrow...

 This weekend I have work to do, but might have time to put the amp together, break it in a bit and listen to it, at least with the current components on the boards. Will desolder just the 5K resistor (instead of the opamp) to do the dc-offset measurement.


----------



## kevin gilmore

The output from the amplifier should be +/- 1 millivolt.

 The output of the servo which is about 1000 times more sensitive
 should be in the range of +/-5 volts.


----------



## rsaavedra

Thanks a lot Kevin!


----------



## rsaavedra

Ok guys, sorry to keep bothering but I still need some help.

  Quote:


  Originally Posted by *sft* 
_1) Remove op27 or 5K beloing to Servo_

 

I removed the 5K resistor since it was easier than removing the opamp (and I haven't received the replacement opamp). Opamp is still on the board then. And btw, I still measure 15v and -15 volts at opamp legs 4 and 7, even though I removed this 5K resistor. Output of the opamp is also similar to what I had measured before, despite the missing resistor.

  Quote:


 2)Measure the dc-offset, if it's negative then populate the pot in right socket.Trun the pot clockwise until you hear a click before populate it and You must plug pin 3 in the small circule position. 
 

Before installing the trimpot I measure the dc-offset to be -14.4 mvolts. So trimpot should go on the right for that board then. Before installing the trimpot, I turn it all the way clockwise as indicated. Just for verification, after that I measured resistance between pins 2 and 3 of trimpot at that setting is 0 ohms.

  Quote:


 3)measure again, the dc-offset should increse.Turn the pot unclockwise until the dc-offset increse to zero 
 

Installed trim pot on right socket then, turned on amp, and dc-offset did increase, but seemingly way too much. DC-offset now is +111.4 mvolts!!! 
	

	
	
		
		

		
		
	


	










 What is worse, if I start turning the trimpot un-clockwise, then that offset just grows worse and further away from zero. Turning it clockwise never makes it better than 
 +111.4 mvolts, the trimpot was already at its limit to being with, so that at least makes sense.

 In the other board did the same, offset starts positive in this one though, +35.1 mvolts. So in principle, I have to put the trimpot on the left socket for this other board. Pre-adjusted the trimpot (again all the way to the right clockwise) and installed it on the left socket. Turned on the amp, DC-offset here decreased, but also way too much, becoming -99.1 mvolts. And again, turning that trimpot un-clockwise just makes it worse, a larger negative number the more I turn it unclockwise. Clockwise and never gets better than -99.1 mvolts.

 So what's wrong? Does it look like I have some components blown maybe? Or should I definitely remove the opamp to take these dc-offset measurements?

 The only way I've managed to bring the offset close to zero in a board is installing the two trimpots on both sockets of the same board, and then tunning appropriately. But is this a sign of some problem? Or do I really need 4 trimpots after all?


----------



## sft

Nothing wrong.The situation is "over adjustment".
 It looks like everything is fine. 
	

	
	
		
		

		
		
	


	




 All you need is 50K or 100K pot
 anorther way is to install two 10K pot per board.That will change the bias current, so be careful.

 Some simple estimation and computation for you 
	

	
	
		
		

		
		
	


	



 When change 1 ohm for 500R, the DC-offset change about 4~5mV, if your DC-offset is 15mV, you must adjust 3 ohm.
 so (500*X)/(500+X)=497, X~83K

 The same compution for another board. This is just only roughly estimation.


----------



## kevin gilmore

The opamp should be on a socket. The 2 pots should be on sockets too.
 Put the 5k resistors back. Turn it on for a few minutes and measure
 the output of the servo. Now take a 50k resistor and put it on pins 1 and
 3 of one of the pot sockets. The bias will change, and will take a minute
 or two. Either the right direction, or wrong direction. If the wrong direction
 flip to the other side. Now if 50k is not enough or too much, then compensate
 with a different value resistor. Once you know about what you need then
 put in the appropriate pot. There are cases where the 10k pot is not
 enough resistance i could imagine.


----------



## rsaavedra

Gee this trimpot adjustment wasn't a simple plug and play thing after all. Looks like I'll have to order and wait for higher value trimpots then, so l won't be listening to the amp this weekend 
	

	
	
		
		

		
		
	


	




. In any case thanks a lot guys!

 Cheers,
 Raul


----------



## rsaavedra

Quote:


  Originally Posted by *sft* 
_Some simple estimation and computation for you 
	

	
	
		
		

		
		
	


	



 When change 1 ohm for 500R, the DC-offset change about 4~5mV, if your DC-offset is 15mV, you must adjust 3 ohm.
 so (500*X)/(500+X)=497, X~83K_

 

If I understand your formula correctly, then a 10K trimpot works only when the circuit has DC offset of approx 119 mvolts or larger.

 Given that my offsets are -14.4 and +35.1, would seem I need trimpots of at least 88K , and 36K respectively. I guess 100K and 50K are the options then.

 But before placing any order will re-solder the 5K resistor, and will try resistors in pins 1-3 of the trimpot sockets, as suggested by Kevin, to corroborate these required pot values.


----------



## sft

Good luck and enjoy the great machine!


----------



## kevin gilmore

If you have high impedance headphones even 35 millivolts of offset
 are not a problem, so go and listen.

 Many capacitor coupled amps with electrolytic caps leak 35 millivolts
 or more...


----------



## rsaavedra

Ah good to know!!! 
	

	
	
		
		

		
		
	


	




 Will go ahead and listen once I put everything together then. Thanks much again!!


----------



## rsaavedra

Quote:


  Originally Posted by *kevin gilmore* 
_The opamp should be on a socket. The 2 pots should be on sockets too.
 Put the 5k resistors back. Turn it on for a few minutes and measure
 the output of the servo._

 

Finished that part, here's 5K resistors back and opamp sockets installed:






 Amp has been on for about 15-20 minutes. I guess the temperature affects the measurements? Haven't installed trimpots, so other than the presence of the opamp sockets, is back to where I had it before receiving the trimpots. Here's what I'm measuring:

 Left board opamp output: -4.85 volts, and very slowly changes, some times up, some times down. I've seen it between -5.11 and -4.65, just minutes away between measurements.
 Left board dc-offset: oscillates between -4.1 and -0.08mv 

 With a 39.2K resistor on left socket of left board, opamp output is 0.30, and very slowly going up.


 Right board opamp output: +2.20 volts, and very slowly changes as well, have seen it between 1.47 and 2.90.
 Right board dc-offset: oscillates between -4.4 and +5.3mv

 With a 39.2K resistor on right socket of right board, opamp output is -2.87, and slowly going up (e.g. getting closer to zero).


----------



## rsaavedra

Got the fuses, new opamps, and new 7815,7915's (to220 package) today!

 But now I'm wondering if I should install them. I rather tend to think in the "if it ain't broke don't fix" philosophy. If I seemingly have rather well matched components already on the boards, and they seem to be working fine, would you recommend installing these new ones?


----------



## gsferrari

Have you listened to the amp already!?!?! 
	

	
	
		
		

		
			








 This is like having a ferrari parked in your garage and no gas to take it out!! CMON!! I am dying to hear what you think about the amp 
	

	
	
		
		

		
		
	


	




 Waah!


----------



## rsaavedra

Quote:


  Originally Posted by *gsferrari* 
_This is like having a ferrari parked in your garage and no gas to take it out!!_

 

Yes man I feel exactly like that! 
	

	
	
		
		

		
		
	


	




 No I haven't listened to it yet. Right now building the coax cables for inside the amp using the teflon coated silver wire. Planning to use copper braid and aluminum foil + teflon tape + electric tape to finish up the coax on these. Here's a pic of the silver wire btw. Also sanding down the bottom panel where the braces for the heatsinks will be attached. Totally bought the idea of using that whole panel and the whole chassis as part of the heatsinking structure. It does get very hot. Hope to have everything together between tonight and tomorrow.






 More pics of the put-together coming...


----------



## rsaavedra

Well, removed the 10K resistors from the boards once the Elma was connected. Put the 100 ohm resistors between Elma outputs and board inputs (because of the "hard zero" on the way I populated the Elma), and connected everything using a star ground scheme. Powered it up with no input connected, and volume setting at zero. LED's went up for a second and then went off. I powered it down and then up again, they wouldn't come up, the 2A fast blow fuse had blown. Tried again with another same kind of fuse, and it was blown immediately, LED's didn't even lit up this second time.

 I double checked all the connections and everything was ok. Disconnected the power supplies and tested them independently, turns out one seems to be damaged, or in any case not working right. It's producing just 0.9 volts 
	

	
	
		
		

		
		
	


	




 They have 3 years warranty, but not sure if after soldering wires in the AC inputs it still holds. Right before putting everything together the two power supplies were working fine. The other one is fine producing 30 volts perfectly. Any ideas why this problem might have occurred?


----------



## TrevorNetwork

Guru & all those that have yet to _really_ hear the Dynahi,

 OMG teh sound!!!! 
	

	
	
		
		

		
		
	


	










 You -will- love it.


----------



## gsferrari

I hope Raul will have his finished in time for the meet. I hope he is more optimistic about it than I am...this seems to be a tough job if he has been at it for several months now...

 I have all the parts coming in time for the meet and I will probably sit in a corner with Raul and get everything sorted out with his guidance...yay!


----------



## rsaavedra

I now notice left the resistors between pins 1 and 3 of the trimpot sockets. The resistors are those with which I got the dc-offset measuremenst reported before, the lowest ones I could without actual trimpots. So in one board there was one of 39.2K resistor, in the other one of 97K instead of the trimpots. Could any of this have been a problem to damage one of the power supplies?


----------



## intlplby

yeah i just got a lot of my parts this past week

 all components except transistors for 12 dynahi boards.....

 all components for 1 ppa, 1 ppa battery board, 1 steps, 1 mint


 still need dynahi transistors, dynahi power supplies, dynahi heatsinks, enclosures, connectors, buttons and switches for the amps


 i need to go get some organizer for all these resistors......


----------



## kevin gilmore

Nothing you could have done would have damaged that power supply.
 (well unless you apply 110 volts to the output section)

 There are 2 pots on the power supply, one is voltage, the other is current.
 Try moving the current pot slightly.


----------



## rsaavedra

Quote:


  Originally Posted by *kevin gilmore* 
_Nothing you could have done would have damaged that power supply. (well unless you apply 110 volts to the output section)_

 

An a/c cable touching the chassis would be the only way I can think of that would allow a/c to get into the output part (through the star ground point), but seriously doubt that could have happened. Well, once I also wouldn't have thought there could have been anything wrong on my boards, and turns out I had couple of components reversed, so won't bet anything. But also, wouldn't a/c anywhere in the ouput have damaged both power supplies? Only one is damaged, the other seems to be in perfect condition, and they were connected in series. Also, I guess that would have been a major spark and smoke feast. None of that. The amp actually sort of started, LED's lighting up but just for half a second or so, then went out, silently.

  Quote:


 There are 2 pots on the power supply, one is voltage, the other is current. Try moving the current pot slightly. 
 

That other pot has some stiff blue resin on top blocking the slot (almost as if not to be adjusted actually). Just in case, I'll wait a bit to find out how the warranty goes with these. After calling AlliedElec I had to call Condor directly. Waiting for them to call me back to see what will do, if troubleshoot or send for checkup/return/exchange.

 In any case thanks a lot Kevin! Can hardly wait to have this amp ready and enjoy its sound.


----------



## rsaavedra

I started thinking that if by any chance a/c got into the chassis and ground, then it could have damaged possibly lots of things on the boards. I just did a little test that is a little comforting. Used a 9v little battery + alligator clips + cables of the multimeter to touch the legs of all the LEDs in the boards. They are all working fine. Hope this is encouraging about the state of all other things on the boards.


----------



## rsaavedra

Starting to feel bad about hijacking this thread. Noone else has had too many Dynahi building related questions/issues? I'm such a newbie then 
	

	
	
		
		

		
		
	


	







 Anyway, just wanted to write that I talked to Condor's Support Dept., they told me to fill out their RMA Request Form online (done already), to eventually get the unit repaired under its warranty, sounds great, the girl I talked to was really nice. Only bad thing is, not sure how long that might take, back-and-forth shipping time + repair time. My Dynahi is on hold for a while before it sings then.

 In any case, I ordered 3 types of trimpots already: 25K, 50K, and 100K, for whenever I get a chance to power everything again, fine tune its DC-offset, and then finally listen it sing.


----------



## rsaavedra

Gallery of my Dynahi here.


----------



## rsaavedra

After checking with Kevin and giving it much thought, think I know what must have happened to my power supply. If you check this pic:







 Notice that side aluminum wall on the right, I installed it to shield the main boards from the power supplies even more than what the heatsink assembly would on its own. Notice also in the picture, there's this aluminum angle that I installed to attach that wall to the supplies chassis. I had to file down that angle on top in two places, so that it could fit snugly around the transistors. It did fit around them, but the borders of the dents ended up quite too close to the transistor anyway. The transistors have metallic exterior, and are isolated from the power supply chassis by a thin pinkish washer that can also be spotted in the pic. *That exterior of the transistor is not supposed to *ever* get in touch with the DC circuit's ground*. This I wasn't aware of was so critical. If that transistor touches dc ground, then the PS can get damaged. As good as these power supplies must be, that is quite an Achilles heel in this design I think, having that transistor so exposed and with metallic exterior, just ready to get shorted with the power supply's chassis all around it.

 Anyway, won't blame it on Condor's engineers, all my unawareness and fault. When attaching the power supplies to the case of the amp, for easier fit the aluminum angle holding that shielding wall connecting the power supplies better not be too tightly attached, so that it could yield a little for bolts to enter the holes more easily, otherwise the fit would prove quite challenging. With that aluminum angle being so near the transistors, it could have easily reached out some millimeters and have touched the transistors exterior. Even if this didn't happen, I realize any tiny chip of aluminum left over from drilling the chassis etc, could have shorted the transistor with the power supply chassis. And for sure, that chassis was connected to DC ground. So this is by far the most likely scenario that caused one of my power supplies to go bad: that transistor getting shorted to DC ground.

*So beware: if you are getting one of these power supplies, apply some layers of electric tape on top of those transistors, to make sure nothing will touch them and possibly short them to the chassis or DC circuit's ground.*

 Besides applying that tape, needless to say, I'll file those dents in that aluminum angle quite a *lot* more.


----------



## TrevorNetwork

Shorting the transistor cans to the chasis of the PSU could definitely result in a pooched PSU. Best of luck with the RMA.


----------



## rsaavedra

Quote:


  Originally Posted by *TrevorNetwork* 
_Shorting the transistor cans to the chasis of the PSU could definitely result in a pooched PSU. Best of luck with the RMA._

 

Thanks Trevor!
 Cheers,
 Raul


----------



## Pars

Quote:


  Originally Posted by *rsaavedra* 
_Starting to feel bad about hijacking this thread. Noone else has had too many Dynahi building related questions/issues? I'm such a newbie then 
	

	
	
		
		

		
			






_

 

I dunno. Some of us haven't started yet


----------



## strohmie

Quote:


  Originally Posted by *Pars* 
_I dunno. Some of us haven't started yet 
	

	
	
		
		

		
		
	


	


_

 

Yea, most of my time has been getting the heat sinks finished up -- warning to anyone who deals with that eBay SpeedyMetals group that I mentioned earlier -- they do NOT do straight cuts. 
	

	
	
		
		

		
		
	


	




 Almost finished sanding down Trevor's heatsinks for his second Dynahi, still haven't drilled all the holes for my own. Boards done, power supplies have yet to be designed. I'll post schematics and such as I get that accomplished, but grad school calls.


----------



## TrevorNetwork

I would just like to publically acknowledge Strohmie's efforts on the metal brackets. I really appreciate this Strohmie.


----------



## rsaavedra

Good news! Just got the RMA from Condor, they will repair the PS under warranty at no charge! This is regardless of my telling them I had drilled the side panels, and the terminals have had wires soldered on them. Great warranty and service. PSU is on their way.


----------



## rsaavedra

Checking these pictures of Trevor's Dynahi, I realized he hadn't removed the 10K resistor from this boards, even though he already had connected an attenuator. Trevor tells me he hadn't heard about having to remove that resistor at all, and after all he likes how his amp is sounding. Both Sft and Kevin had told me through pm or email that I did indeed have to remove that resistor before connecting the Elma attenuator. Supposed to be needed to measure the DC offset when there is no attenuator connected.

 In the pic below I highlight the resistor, it's the one right above the input signal connector. Can someone please explain what the deal is between that resistor and the attenuator? Should it always be removed, or is it just optional to remove it?


----------



## Garbz

Not exactly sure because i haven't been following the Dynahi design but in the older Dynalo the input needed to be connected to GND either via resistor or via a direct connection do measure DC Offset. The amp still worked afterwards if there was a resistor there but generally I removed any input -> gnd connection once my pot was in.

 If you try to measure the DC offset on the Dynalo without the input loaded the Offsets would go nuts!


----------



## rsaavedra

Thanks Garbz, guess it's not a problem to leave those resistors there then. Though I think I'll remove mine once dc-measured is done, and trimpots are installed.

 Added couple pics of my redone wiring at the bottom of this post. The power supply I sent to Condor hasn't been delivered to them yet, it'll be a while.


----------



## sft

It changes the log curve.


----------



## rsaavedra

Quote:


  Originally Posted by *sft* 
_It changes the log curve._

 

What changes the log curve, the presence/absence of the 10K resistor you mean? What log curve is this btw?


----------



## sft

1)the presence of the 10K resisitor.
 2)volume pot


----------



## rsaavedra

Thanks Sft!

 Sorry to keep nagging on this, trying to understand.

 Checking BCBill's schematics here, I observe that the 10K resistor seems installed between the input signal and ground. But measuring the DC-offset, aren't we supposed to short the input to ground? From that, I would guess that resistor is not needed for DC-offset measuring and adjusting the trimpots. But then, it is not needed after measuring DC-offset and adjusting the trimpots either, once the attenuator is installed. So we actually could do without that resistor all together? Just trying to understand these things electronic. If I'm way off just ignore, I'm a newbie after all.


----------



## Garbz

if it is the resistor i think it is then the effect would be the same. The input needs to be in some way electrically connected wheter by a direct short, by a 10k resistor to gnd, a 1M resistor to gnd, or via the resistance in the volume pot / stepped attenuator.

 If an attenuator is attached the resistor is NOT needed. If the amp does not have a volume it is needed since unplugging the souce would cause the amp to go nuts.


----------



## rsaavedra

Quote:


  Originally Posted by *Garbz* 
_If an attenuator is attached the resistor is NOT needed. If the amp does not have a volume it is needed since unplugging the souce would cause the amp to go nuts._

 

Ah ok great, thanks for the clarification Garbz!
 Cheers,
 Raul


----------



## rsaavedra

Well if I got something positive after the recent amp-gut "analness" displayed by some headfiers, was the awareness of floating wires possibly being not a good idea for the long term. I added some bolts and plastic clamps to support my input signal path wires. Formerly they were just floating between the RCA ins and the Elma, so over time there could be stress on the solder points. Not any more with this extra support:
http://photo.head-fi.org/showphoto.p...sort=1&cat=500 ( <- large version)





 Though it didn't seem as necessary, added similar support for the output wires too:
http://photo.head-fi.org/showphoto.p...sort=1&cat=500( <- large version)





 Bolts holding the clamps for the output wirese are attached to the heatsink. The clamps are rated 185 degrees F (85 C). In case that's not sufficient heat tolerance, I used nylon nuts as washers for tightening the clamps, just in case. Aluminum foil stripe (not visible) lining the inside of the electrical tape sleeving the output wires, for shielding. Similar to the diy coax for input wires.

 Another angle of the support additions:
http://photo.head-fi.org/showphoto.p...sort=1&cat=500( <- large version)




 Any suggestions welcome.
 PS. Power supply arrived in Condor yesterday for service.


----------



## TrevorNetwork

Hi all,

 I have cased up the dynahi (similar to Rsaavedra's) and I now have a hum (60hz). Unfortunately it is induced on the board, and not the input wires. So shielding the input will not really help. I removed the input wires from the board all together, and still heard a light hum. I have tried rotating the power supplies to no avail. This issue did not occur prior to casing it up. The person that made my enclosure it willing to make me a solid piece of 1/4" aluminum with a 3/4" hole near the bottom with a grommet to feed the wires through. I could place this wall in the centre, to divide the psus from the pcbs. Would this help at all? Or is my only solution to separate the psus from the pcbs, and run an umbilical?

 Trevor


----------



## rsaavedra

Quote:


  Originally Posted by *TrevorNetwork* 
_The person that made my enclosure it willing to make me a solid piece of 1/4" aluminum with a 3/4" hole near the bottom with a grommet to feed the wires through. I could place this wall in the centre, to divide the psus from the pcbs. Would this help at all? Or is my only solution to separate the psus from the pcbs, and run an umbilical?
 Trevor_

 

Hope the separation in two cases can be avoided. I already have some sort of wall between the psu's and the heatsinks (see here), but after your post, wonder if it will provide enough shielding, it's just 1/8" thick, and the angle holding the wall is just about 1/16" thick. Also, it has 4 holes, 2 for wires, and 2 for ventilation. If that wall doesn't do enough shielding, would it make sense to make some sort of Faraday cage for the boards using a metallic mesh that will completely surround them, heatsinks included? Would that shield the boards completely from any nearby field no matter how strong?


----------



## TrevorNetwork

To be frank, I do not really understand what is occuring. I do understand the induction of current, in, say a transformer. However, I do not understand what is occuring in this scenario. Thus, I am unable to come to a reasonable fix for it. I thought that maybe a 1/4" thick wall, that is isolated from the chasis, but connected to circuit ground might do it. At present my chasis is isolated fully from the circuit.

 I am not sure how many members are reading this thread. It may be a good idea to post it up in the DIY forum under its own thread...

 Trevor


----------



## rsaavedra

Quote:


  Originally Posted by *TrevorNetwork* 
_I am not sure how many members are reading this thread. It may be a good idea to post it up in the DIY forum under its own thread..._

 

Agree, this issue is not really Dynahi specific, but amp building related in general.

 I'm also wondering whether what ends up being listenable humming might be 60 Hz ripples that might leak in through the DC power wires themselves.


----------



## chillysalsa

You guys are way ahead of me... I am getting around to ordering parts now.

 Questions:

 One transistor part has two versions with different DC current gain specs:
 2SC3381GR is typically 200-400
 2SC3381BL is typically 350-700

 Does it matter which one I use?


----------



## Edwood

Will the next version have option for balanced inputs? or can the current one be wired for balanced inputs?

 -Ed


----------



## chillysalsa

Update: I contacted Kevin about the versions and this followed:
  Quote:


 They all need to be the same, and match the
 other power transistor. Did not know there were
 two versions. Will have to look later as to which
 i've been getting. 
 

 So, since I am ordering from B&D. For the other trans. they only have 2SA1349BL, so I have no choice really, and will match it with 2SC3381BL. BL versions are the higher rating... I bet it won't make much of a difference.


----------



## rsaavedra

Quote:


  Originally Posted by *chillysalsa* 
_Update: I contacted Kevin about the versions and this followed:
  Quote:


 They all need to be the same, and match the
 other power transistor. Did not know there were
 two versions. Will have to look later as to which
 i've been getting. 
 

_

 

Gee had to check the receipt, fortunately I got matching 3381BL and 1349BL, from B&D as well.


----------



## Pars

Quote:


  Originally Posted by *Edwood* 
_Will the next version have option for balanced inputs? or can the current one be wired for balanced inputs?

 -Ed_

 

I think the current one can be built in a balanced configuration, but would require 4 boards instead of 2 for the unbalanced. Someone correct me if I'm wrong <g>.


----------



## TrevorNetwork

Yes, it would require four boards, and four PSUs. Unless someone makes a PSU specifically for the Dynahi that has the current to power four hungry dynahi boards at +/-30.


----------



## gsferrari

Trevor - Balanced means that you have separate power supply and amp section for each channel right? Isnt that what the current 2 board setup achieves?

 Can you post a quick drawing about what balanced and non-balanced are? 
	

	
	
		
		

		
		
	


	




 Why would you need 2 boards for each channel?


----------



## rsaavedra

Quote:


  Originally Posted by *gsferrari* 
_Trevor - Balanced means that you have separate power supply and amp section for each channel right? Isnt that what the current 2 board setup achieves?_

 

Nope that's not balanced Guru. Here a definition of balanced connection: http://en.wikipedia.org/wiki/Balanced_audio_connector


----------



## TrevorNetwork

I'll post up a little paint drawing soon. 
	

	
	
		
		

		
		
	


	




 One of my paint drawings is already in this thread. 
	

	
	
		
		

		
		
	


	




 Anyway, the idea of "Balancing" an amplifier is not simply having one psu per separate, and identical amplifier channel. What you are referring to would be dual mono. Balancing implies that each channel is outputting the original wave form, and a wave form shifted by 180 degrees. Effectively, the inverse wave. To achieve this, one must have two boards per channel. Four power supplies are necessary due to the draw of the amplifier.


----------



## gsferrari

Quote:


  Originally Posted by *rsaavedra* 
_Nope that's not balanced Guru. Here a definition of balance connection: http://en.wikipedia.org/wiki/Balanced_audio_connector_

 


 Thanks


----------



## gsferrari

Quote:


  Originally Posted by *TrevorNetwork* 
_I'll post up a little paint drawing soon. 
	

	
	
		
		

		
		
	


	




 One of my paint drawings is already in this thread. 
	

	
	
		
		

		
		
	


	




 Anyway, the idea of "Balancing" an amplifier is not simply having one psu per separate, and identical amplifier channel. What you are referring to would be dual mono. Balancing implies that each channel is outputting the original wave form, and a wave form shifted by 180 degrees. Effectively, the inverse wave. To achieve this, one must have two boards per channel. Four power supplies are necessary due to the draw of the amplifier._

 


 ummm...I think i'll build the stock Dynahi for the time being 
	

	
	
		
		

		
		
	


	




 LOL


 Anyone need extra heatsinks (the HTS ones that Raul etc. are using?) I may have 2 or even 4 of them leftover after I finish...

 Cheers!


----------



## TrevorNetwork

I could use a couple heatsinks. Maybe even all four.


----------



## rsaavedra

I think this comment deserves a separate post.

 For those who might be planning to go balanced, except for systems with long cable runs, *balanced doesn't necessarily mean better*. In fact, if cable runs are short, an unbalanced system might be the best option. From the Wikipedia entry posted above:

  Quote:


 In recording and for short cable runs in general, a compromise is necessary between the noise reduction given by balanced lines and the noise and distortion introduced by the extra circuitry they require.


----------



## Turing

I could also use 2 heatsinks if you have some left over gsferrari


----------



## philodox

I could use a couple of the heatsinks... but it looks like they are already spoken for.


----------



## gsferrari

I will get back to you guys who need the heatsinks after I test my amp out. I bought the extra ones just in case because Raul complained about excessive heat...

 If I dont need them - you guys can have em - just give me some time to work this out.

 Cheers!


----------



## drubrew

What flavor Opamp is everyone using? Have not had a chance to sit down with the schematic and parts list yet. Has anyone determined any critical components in the signal path worth upgrading to high quality components? Or is everyone one still in the building process? Hope to get to this next month.
 Drew Baird
 Moon Audio


----------



## Jahn

somewhat related Q - any possibility of a Dynahi being ready to check out at the NYC meet? hmm, and for that matter, having a balanced can in hand? Just wondering, thanks!


----------



## Pars

Quote:


  Originally Posted by *drubrew* 
_What flavor Opamp is everyone using? Have not had a chance to sit down with the schematic and parts list yet. Has anyone determined any critical components in the signal path worth upgrading to high quality components? Or is everyone one still in the building process? Hope to get to this next month.
 Drew Baird
 Moon Audio_

 

The opamp is pretty immaterial as it is only for the servo loop. I am just getting started in spec'ing out (then buying) parts, but the recommended parts in the spreadsheet are a real good starting point... not much application for BlackGates and other magic components, at least on the amp modules (IMHO). The PSU may be a slightly different story, but I'm guessing not, particularly if you use the Condor PSUs.


----------



## TrevorNetwork

The opamp does not influence the sound whatsoever. As long as one within the spec laid out by KG is used there is no problem. Get with the next generation. OPAMPs are for chumps. 
	

	
	
		
		

		
		
	


	























 jk (kindof!)


----------



## Edwood

Quote:


  Originally Posted by *rsaavedra* 
_I think this comment deserves a separate post.

 For those who might be planning to go balanced, except for systems with long cable runs, *balanced doesn't necessarily mean better*. In fact, if cable runs are short, an unbalanced system might be the best option. From the Wikipedia entry posted above:_

 

Yes, but balanced runs are virtually immune to ground loops, which is an important feature for those using computers-as-a-source.

 Oy. 6000th post! WOah. 
	

	
	
		
		

		
		
	


	




 -Ed


----------



## strohmie

This thread dropped so low that I accidentally posted in the original "group buy" one.


 Severe boredom with my school work has led me to start designing the power supply for my Dynahi. I unfortunately pulled up a couple of the top-side resistor pads recently so I'm not going to have the prettiest Dynahi out there. 
	

	
	
		
		

		
		
	


	




 Should still be functional though.

 The first part of the chain will likely be a toroidal transformer, likely from Plitron. I have a few of these I need to buy which I'll probably do all in one fell swoop. The one I get from them will probably be your standard issue +30V/0/-30V or so, though I might have to do a couple calculations and check to make sure that isn't going to give me too much voltage past the diode bridge/caps at the voltage regulators (which I believe are rated for a max input of ~36V).

 After the transformer comes the diode bridge -- I'm planning on buying a good one for this purpose:






 The heatsinks won't be needed for the amount of current used in this application. Following this directly will be a decent amount of capacitor filtering, though I'm not sure of the exact amount I want to use. Ideas?

 I have a couple Jung superreg boards I'll be propagating this week to come in after the caps:






 One will be designed for approx. 30V, the other approx. -30V. The resistor numbers will be a little off but I'm aiming it a little over +/-30V. Planning on using excessively priced materials the whole way through. 
	

	
	
		
		

		
		
	


	





 How many people have theirs done and are listening right now?


----------



## Pars

Strohmie:

 Where'd you get that bridge board? Thats exactly what I was thinking about doing when I get around to building my Dynahi (or 2). I see the regulator boards are from LW audio, might have to look into those also.

 Chris


----------



## strohmie

Quote:


  Originally Posted by *Pars* 
_Strohmie:

 Where'd you get that bridge board? Thats exactly what I was thinking about doing when I get around to building my Dynahi (or 2). I see the regulator boards are from LW audio, might have to look into those also.

 Chris_

 

Go over to diyaudio -- they're having a group buy for them that's basically ending as of Sunday. Might still be able to get in on it, not positive.


----------



## rsaavedra

What do you guys think? Here's the shielding I added to my Dynahi boards. The heatsinks will be connected to the chassis through those aluminum feet, and also connected to the shield through a copper angle at the top. So besides shielding the boards from interference, and shielding the attenuator and input wires from the boards, all this surface in the shield + the bottom of the chassis will help heat dissipation a lot, I might drill some holes for more ventilation.





Full size image





Full size image





Full size image





Full size image





Full size image


 Bottom of the shield. Here you can see all the holes in the shield so far: for power wires at the bottom, for input wires in the steel back, and a hole for the output wires on the side that will be facing the headphone out connectors.




Full size image


----------



## gsferrari

Raul - with the amount of effort you have put into this amplifier - you deserve one that works flawlessly and sounds better than anything else out there 
	

	
	
		
		

		
		
	


	




 It looks absolutely STUNNING!!! 
	

	
	
		
		

		
		
	


	




 Congratulations and I hope this has solved the humm issue...


----------



## JohnFerrier

I purchased my amp case, but hand-formed metal battery holders inside. I used Visio to create a paper template of exactly what I wanted. It was such a good experience that I had wished that I hadn't already purchased the case. Otherwise, I would have tailored one as you have. It has a distinctive look. Enjoy the rare Dynahi.


 JF


----------



## TrevorNetwork

feh. Mine'll still be better.






















 /ulti-person.


 Awesome job Raul. I love it.


----------



## TrevorNetwork

Speaking of, Tiberian's Dynahi made an appearance at the Burnaby mini-meet. I think it did _very_ well. 
	

	
	
		
		

		
		
	


	




 /Dynahi *rules*.


----------



## strohmie

Nice shielding. I'm planning something similar.

 Even with all that and the additional heatsinking to the case, I might recommend putting a few extra holes in the top copper shield just to make sure that heat doesn't get trapped within the copper "case."


----------



## tiberian

Quote:


  Originally Posted by *TrevorNetwork* 
_Speaking of, Tiberian's Dynahi made an appearance at the Burnaby mini-meet. I think it did very well. 
	

	
	
		
		

		
		
	


	




 /Dynahi *rules*._

 

dude, send it to me asap with express mail 
	

	
	
		
		

		
		
	


	




, i have been waiting for more than a month 
	

	
	
		
		

		
		
	


	




.


----------



## gsferrari

Quote:


  Originally Posted by *tiberian* 
_dude, send it to me asap with express mail 
	

	
	
		
		

		
		
	


	




, i have been waiting for more than a month 
	

	
	
		
		

		
		
	


	




._

 


 I thought I was supposed to get it first?


----------



## TrevorNetwork

It sounds sooooooooooooooooooooooooooooooooooooo good

 I am listening to violin concerto music with the ATH-W11R, and ATH-W2002. Jebus it sounds good. I'm serious. Unbelievable.


----------



## tiberian

Quote:


  Originally Posted by *gsferrari* 
_I thought I was supposed to get it first? 
	

	
	
		
		

		
		
	


	


_

 

the florida meet was long over dude.


----------



## gsferrari

Quote:


  Originally Posted by *tiberian* 
_the florida meet was long over dude._

 


 Yeah I know...besides I dont know where I am gonna be tomorrow...and its like this everyday 
	

	
	
		
		

		
		
	


	




 LOL

 Just to clarify - I dont think Raul intends the shielding to be the case - he will put the whole thing into the larger case along with the PSU's or does he have the PSU's in that "improvised" enclosure??


----------



## rsaavedra

Quote:


  Originally Posted by *gsferrari* 
_he will put the whole thing into the larger case along with the PSU's_

 

Yes that is the case (pun intended 
	

	
	
		
		

		
		
	


	




). It will all go inside the larger chasis that has the PSU's and the attenuator. I like the industrial look of the shielding a lot, but unless I use a temperate glass on top, it won't be visible from the exterior.

 Btw Guru, it was Trevor who had a hum problem, turns out it was related to his ground wiring and a ground loop, as Morsel had suggested. He revised his ground wiring and the hum dissapeared.

 I did make the shielding after Trevors problem, thinking the proximity of the PSU's could produce some interference, but could never tell if mine had any hum, I haven't heard my amp yet.

 Anyway the shield will certainly be beneficial against RFI at least. Between PSU's and this amplifier module (as I call it now), instead of an aluminum wall there will be two 26ga steel sheets, which will help against magnetic interference. At some point I might consider some Mu Metal extra shielding for that wall. Can't hurt to shield as much as possible, and it's fun 
	

	
	
		
		

		
		
	


	




 Here's a mild strip tease of the assembly, taking out the sides of the shielding.
 The steel back is sturdy enough so I didn't need nylon spacers to go all the way up to hold the top in place at the back. Left the long spacers just because I had them already.

Full size image


----------



## rsaavedra

Have a question about balanced inputs and outputs.

 If I understand things correctly, you can have balanced headphone outs in a headphone amp that doesn't have balanced inputs. And conversely, you can have balanced inputs, and normal headphone outs. Of course you can also have a headphone amp with both balanced inputs and outputs.

 When people talk about a "Balanced Dynahi" needing 4 boards, they are talking about a Dynahi with (edit) balanced outputs, not necessarily balanced inputs.

 Is all of this correct?


----------



## flecom

well, my source outputs balanced, and my headphones have balanced connectors also... but i dunno if its really worth it to build a balanced (4 board) version...

 it will cost literally twice as much

 has anyone tried a balanced version?

 if it makes an audible difference (for the better obviously) then i guess i will, but im not planning on it atm

 also one other question, the recommended voltage im guessing is +/- 30v... what is the minimum recommended voltage?

 im designing my psu and im trying to figure out what components to get and i would like to know if i can slip by with like 25~28v +/- without a noticable degredation in quality


----------



## chillysalsa

What was KG talking about when he said:
  Quote:


 On the fets you don't connect the middle pin, either bend it up
 or cut it off. 
 

in the original thread...
 Is that still correct?


----------



## rsaavedra

Quote:


  Originally Posted by *chillysalsa* 
_What was KG talking about when he said:
in the original thread...
 Is that still correct?_

 

I believe it is correct, that applies to some components that have 7 legs, and you discard the middle leg. This doesn't apply to any of the 3 legged transistors on the boards though, just to those 7 legged components, e.g. the long black little rectangle, behind and to the right of the LED in this pic:


----------



## sft

Quote:


  Originally Posted by *rsaavedra* 
_If I understand things correctly, you can have balanced headphone outs in a headphone amp that doesn't have balanced inputs. And conversely, you can have balanced inputs, and normal headphone outs. Of course you can also have a headphone amp with both balanced inputs and outputs._

 

Sure.
 It depends on the ckt. between the I/O. And the perfomance depends on topology and implementation.

  Quote:


 When people talk about a "Balanced Dynahi" needing 4 boards, they are talking about a Dynahi with (edit) balanced outputs, not necessarily balanced inputs.

 Is all of this correct? 
 

Believe me, it's difficult to build the balanced bridged dynahi similar to headwize project with RCA input. But i think if you have perfect rca input signal, it's worth to try....


----------



## rsaavedra

Quote:


  Originally Posted by *sft* 
_Sure.
 It depends on the ckt. between the I/O. And the perfomance depends on topology and implementation.

 Believe me, it's difficult to build the balanced bridged dynahi similar to headwize project with RCA input. But i think if you have perfect rca input signal, it's worth to try...._

 

Thanks Sft, no in fact I'm not planning to build a balanced Dynahi, just wanted to make sure my understanding of these technical concepts was right. For sure my Dynahi will be non-balanced.

 I keep thinking going with balanced inputs is only worthwhile not only if you have a source with balanced outputs, but also, if you are going to have long cable runs. Otherwise the extra circuit complexity might make it harder to build it achieving comparable sound quality levels as non-balanced. Just my belief after reading the last paragraphs here. Besides, going balance would mean double+ the cost, double+ the size and heat, and double+ the work.


----------



## sft

About *SPECIAL* benefits of balanced topology especially*for gilmore or dynahi*, pls search kevin's statement.

 about output wire connection for speaker, headphone, balanced, unbalanced,...etc. pls search amb's post recently.

 If i find these post, i am glad to read carefully once again.


----------



## jogor

from what i remember, the benefit of balanced output is double the voltage swing and double the slew rate. high impedance cans will certainly like this.

 i was considering balancing the output of the dynahi im planning to build. how do i go about it? shall i follow how it is done in the dynalo? no need for balance input for me, rsaavedras link (btw thanks for that!) on the balance connector definition help convince me that balance out / unbalanced in is the way to go, a good compromise for my situation.


----------



## dgardner

The only downside is double the distortion.


----------



## jogor

dgardner, good point. from the comments of AMB this could not be a problem if you match your transistors (hand matching your resistor for biasing should also help?). please refer to an enlightening post below:

http://www6.head-fi.org/forums/showp...07&postcount=2


----------



## rsaavedra

Searching about balanced amplification I found that there are indeed "balanced outputs" in some speaker amplifiers, as in this Krell monoblock. The benefit is "better control", words of Krell's founder:
  Quote:


 "The primary advantage of input-to-output balanced operation is control. Independent symmetrical circuit paths individually amplify the positive and negative signals, locking the speaker into a push-pull relationship. FPB series amplifiers exercise absolute control over the most unruly speakers, even those with exotic impedance curves and disruptive back-electromotive forces (EMF). These amplifiers overcome the speakers natural resistance to motion and forces them to perform the precise required movements."


----------



## strohmie

Bump regarding flecom's recent question -- +/-30 is the desired voltage but would a slightly lower voltage still be feasible?


----------



## sft

Yes.


----------



## strohmie

Remind me never to bike at 6am again, 'k?

 Was pulling an all-nighter for no other reason than that I couldn't sleep. Decided to go to work and putz with the output transistors and see if my set would match well. Never made it there.

 It was really just bad timing -- was going across the street at a green light, when someone at the same time happened to be getting ready to turn ahead of me on the opposite side of the street. I'm not sure if I, as a biker, count as a pedestrian, but either way, I didn't get the right of way from the guy. He keeps going, I swerve toward the back of his car to avoid him, pass him, lose control...and crash back-first onto the sidewalk. The Dynahi boards broke my fall.

 I came out of it relatively unscathed:






 The Dynahi boards, on the other hand:






 (and yes, I do realize that I only need one of the trimpots, thanks 
	

	
	
		
		

		
		
	


	




 ). The top board is the more attractive one, you don't want to know what the other one looks like. Surprisingly, the boards didn't crack -- I landed slightly on the curb, so there was some bending pressure applied on the boards, but they survived. Props to the manufacturers for the sturdy boards.

 I'm going to call them a lost cause though. I get the feeling it would be easier to start with fresh boards and parts rather than desolder everything and see if any of it works. The resistors (those that aren't cracked) should still be usable, and luckily the output transistors/resistors weren't yet on the board.

 Oy. And now I have a backache.


----------



## skyskraper

ah bummer about the boards man. glad to hear you are ok though!!!


----------



## strohmie

To make matters worse I had my D-303 I'm selling in there along with the boards (though separated and at least somewhat protected) and now it won't read CDs.


----------



## TrevorNetwork

Ouch.

 I feel for you Strohmie.

 On the bright side, I think I'm the first person to sell/trade a Dynahi. I believe Tiberian is the first guy to have a Dynahi that didn't build it himself. 
	

	
	
		
		

		
		
	


	




 My new, maxed (non-balanaced) will be done in the next couple weeks. If it weren't for the big move, I'd be done this week!


----------



## rsaavedra

Strohmie sorry about the misfortunes you went through, hope there's good luck ahead.

 This morning I got the Condor power supply back from warranty repair. The Repair sheet indicates:

 Failure Observed: No output voltage
 Primary Cause: The IC U1 (ic adj 723 14p dip) was found electrically in short, causing no output voltage.

 So one of the IC's was shorted. Not sure if that's related to my guess of possibly having shorted the large transistor with the case, might have damaged that IC eventually? In any case it's back, haven't tried it yet but I assume it will work perfectly.

 Will proceed as I was planning originally, will just try to adjust DC-offset with the appropriate trimpots, having the transistors 1145 and 2705 for now as they came, with no careful matching. Haven't ordered new ones to match so these ones will do for now.


----------



## rsaavedra

DC Offset adjusted!!! Here's a pic of my Dinahi alive, though not yet heard:


----------



## rsaavedra

Just heard it, found two issues:

 1) Humming. Haven't soldered everything power related though, and in particular, didn't have chassis connected to the ground point. Will have to recheck everything ground related.

 2) Gain is HUGE!! In first position of the Elma there is no music (just that hum in 1). In second position, volume is already around maximum comfortable levels (
	

	
	
		
		

		
		
	


	




) From then on at third, fourth position and so on, it gets progressively louder, but curiously not in major jumps of volume, just slowly getting louder with each step of the attenuator 
	

	
	
		
		

		
		
	


	




 The jump from first to second position is the one that has a major jump in volume.

 This gain issue is making me wonder if the values I used in my Elma are ok. Anyone would like to comment/make any suggestions?


----------



## TrevorNetwork

Raul,

 What is the value of your feedback resistors? Do you current have the input resistors in?

 Trevor


----------



## TrevorNetwork

As for the humming, send me a paint drawing of your signal + ground scheme. I can probably help.


----------



## rsaavedra

Quote:


  Originally Posted by *TrevorNetwork* 
_What is the value of your feedback resistors?_

 

Which ones would those be?

  Quote:


 Do you current have the input resistors in? 
 

Well, same question again. Are you referring to resistors between the Elma and the boards? Because of the "hard zero" in my Elma, I have 100 Ohm resistors in series between its outputs and the inputs of the board. 

 I did remove the 10K resistor from the board though, not sure if that's part of the reason of this huge gain.


----------



## TrevorNetwork

The feedback resistor is to the right of the 33pF capacitor. It is labelled "2000" on the board. This controls the gain of the amplifier. A lower value will decrease the gain of the amplifier.

 The input resistor, labelled "10K", and located near the centre of the board should be populated in my opinion.


----------



## rsaavedra

As for my wiring diagram:
http://www5.head-fi.org/forums/showp...6&postcount=16


  Quote:


  Originally Posted by *TrevorNetwork* 
_The feedback resistor is to the right of the 33pF capacitor. It is labelled "2000" on the board. This controls the gain of the amplifier. A lower value will decrease the gain of the amplifier._

 

I have a 1.2K, as it had been recommended at some point.

  Quote:


 The input resistor, labelled "10K", and located near the centre of the board should be populated in my opinion. 
 

I will try populating it to see.


 You know, I now really wonder about the sequences of resistors in my Elma. This is how I populated them:
 (1) 49900 - 0
 (2) 34800 - 15000
 (3) 25500 - 24900
 (4) 20000 - 30000
 (5) 15000 - 34800
 (6) 12100 - 38300
 (7) 10500 - 39200
 (8) 7870 - 42200
 (9) 6340 - 43200
 (10) 4990 - 46400
 (11) 3920 - 46400
 (12) 3160 - 46400
 (13) 2490 - 47500
 (14) 2150 - 47500
 (15) 1690 - 47500
 (16) 1400 - 47500
 (17) 1050 - 49900
 (18) 750 - 49900
 (19) 562 - 49900
 (20) 392 - 49900
 (21) 274 - 49900
 (22) 121 - 49900
 (23) 51.1 - 49900
 (24) 0 - 49900
 In parenthesis: position in the attenuator
 Left column: Input-to-Output resistor values (inner ring in the Elma)
 Right column: Output-to-Ground resistors (outer ring in the Elma)

 Notice that above there is indeed a big jump between first and second position. I'm thinking whether the following should have been the correct way to populate the attenuator, basically fliping upside down the table above, and switching the columns, while preserving the same legend. I considered this scheme too, but thought it didn't make as much sense to keep the same resistance between input and output all the way from position 1 to position 8. But now on second thought, the resistance from output to ground does increase very slightly on those after all:
 (1) 49900 - 0
 (2) 49900 - 51.1
 (3) 49900 - 121
 (4) 49900 - 274
 (5) 49900 - 392
 (6) 49900 - 562 
 (7) 49900 - 750
 (8) 49900 - 1050
 (9) 47500 - 1400
 (10) 47500 - 1690
 (11) 47500 - 2150
 (12) 47500 - 2490
 (13) 46400 - 3160
 (14) 46400 - 3920
 (15) 46400 - 4990
 (16) 43200 - 6340
 (17) 42200 - 7870
 (18) 39200 - 10500
 (19) 38300 - 12100
 (20) 34800 - 15000
 (21) 30000 - 20000 
 (22) 24900 - 25500
 (23) 15000 - 34800
 (24) 0 - 49900


----------



## TrevorNetwork

Try placing an Alps blue pot in the place of the SA should you have one around. Let's eliminate the gain issue, and humming first. Then we'll take a look at the potentially problematic SA.


----------



## rsaavedra

Quote:


  Originally Posted by *TrevorNetwork* 
_Try placing an Alps blue pot in the place of the SA should you have one around. Let's eliminate the gain issue, and humming first. Then we'll take a look at the potentially problematic SA._

 

Good idea Trevor, will order an Alps to try that. Thanks a lot!


----------



## eweitzman

Go buy a cheap pot from radio shack and you'll eliminate problems with the attenuator pronto double quick!

 - Eric


----------



## sft

How to check ladder type SA:

 measure the resistor between input and ground, if the value is near 50K(10K, 100K) at every position, then we can make sure almost that the SA is good. It takes just about 1 minnute.


----------



## rsaavedra

Quote:


  Originally Posted by *eweitzman* 
_Go buy a cheap pot from radio shack and you'll eliminate problems with the attenuator pronto double quick!_

 

Oh man even faster, didn't think about Radio Shack this time, hopefully they still carry volume pots. This is a perfect case when they would save the day quickly.

  Quote:


  Originally Posted by *sft* 
_How to check ladder type SA:
 measure the resistor between input and ground, if the value is near 50K(10K, 100K) at every position, then we can make sure almost that the SA is good. It takes just about 1 minnute._

 

Yes Sft I did that right after finishing the Elma, and at all the positions it measured perfectly very close to 50K. That test has to hold, so it's necessary, but it's not really sufficient. The ordering of Input-Output and associated Output-Ground values, is also very important (and I think that's the part I might have wrong).

 Consider that if you scrambled the ordering of raws in any of the tables above, you would still always measure ~50K between input and ground, but despite that, the attenuator would be useless since the ordering wouldn't provide a progressive volume increase/decrease when switching positions.


----------



## gsferrari

If you need an ALPS pot pronto I can send you one express mail. 50K pot.

 Cheers!


----------



## rsaavedra

Quote:


  Originally Posted by *gsferrari* 
_If you need an ALPS pot pronto I can send you one express mail. 50K pot.
 Cheers!_

 

Thanks very much for the thought Guru. I think it'll be faster that at lunch time I just stop by the local Radio Shack to get a cheap pot. Thanks again though!
 Cheers,
 Raul


----------



## sft

Now I know what happen to you...
 96 resisitors, OMG


----------



## rsaavedra

Quote:


  Originally Posted by *sft* 
_Now I know what happen to you...
 96 resisitors, OMG 
	

	
	
		
		

		
		
	


	


_

 

Yes 96 resistors == 192 soldering points == about 8 hours of work in total for me. And if my guess is correct, I think I should have built it using the second table instead of the first. 

 Reversing the input and ground connections might be an easy quick fix though. But then the attenuator would raise the volume when turning it counter-clockwise which would be weird.


----------



## eweitzman

Quote:


  Originally Posted by *rsaavedra* 
_Reversing the input and ground connections might be an easy quick fix though._

 

If you're using a single "stereo" switch with five decks, the middle deck is ground. Reverse the in/out connections and you'll get silence.

 - Eric


----------



## rsaavedra

Quote:


  Originally Posted by *eweitzman* 
_If you're using a single "stereo" switch with five decks, the middle deck is ground. Reverse the in/out connections and you'll get silence._

 

Five decks? I think the Elma ladder attenuator probably is not one of those:
http://www5.head-fi.org/forums/showp...8&postcount=91.

 Also, it's not reversing Ins and Outs what I said btw, would be reversing Ins and Grounds actually.


----------



## eweitzman

Quote:


  Originally Posted by *rsaavedra* 
_Five decks?_

 

See the Elma BV22569 five-deck switch that Michael Percy sells on the middle of page 13 in his catalog.

  Quote:


  Originally Posted by *rsaavedra* 
_I think the Elma ladder attenuator probably is not one of those:
http://www5.head-fi.org/forums/showp...8&postcount=91._

 

I looked at the photo and it doesn't help me understand what you're doing. Do you have a photo showing resistors in place? I don't see how you'd wire a ladder attenuator with the four deck switch unless the ground leads are all soldered together in free air.

  Quote:


  Originally Posted by *rsaavedra* 
_Also, it's not reversing Ins and Outs what I said btw, would be reversing Ins and Grounds actually._

 

My mistake: reverse in/ground and you'll get silence if both channel's grounds are tied together.

 - Eric


----------



## rsaavedra

Just confirmed with Itzbitz, yes the right ordering should be as in the second table. I'll update my original post with that ordering, so that noone might follow the first wrong table blindly and make the same mistake. In case anyone purchased resistors following my table, fortunately all the resistor values hold, only not in the ordering I had originally indicated.

 To fix the Elma I'll go ahead and order new resistors, will be too much trouble to desolder these ones planning to reuse them. But for now I'll reverse inputs and ground. Got a $3.00, 100K potentiometer from Radio Shack, but I'll rather just switch ins/gnd, and turn the volume up counter clockwise till repopulating the Elma.


----------



## rsaavedra

Quote:


  Originally Posted by *eweitzman* 
_My mistake: reverse in/ground and you'll get silence if both channel's grounds are tied together._

 

Both grounds are really separate in the Elma though (I merged them into one ground but outside the Elma). Here's a schematics of how the Elma is wired, it's the "mini-L" case:
http://www.goldpt.com/compare.html

 Inputs and grounds should be switcheable with no problem, the circuit will effectively become table 2.

 Photo of my Elma with resistors in place:


----------



## rsaavedra

Tonight I did the reversal of input and ground on my Elma and works ok, only volume increases counterclockwise, till I repopulate the Elma.

 I also separated the grounds of each channel between the Elma and the star ground point, and kept the Elma dettached from the chassis. Hum was reduced quite a bit, but didn't fully dissapear. I started moving slightly the ground wires between the Elma and the star ground point, and lo and behold!, the humming increases quickly and gets quite loud the closer those wires get to either the PSU transformers, or the AC power inlet. So actually, now not sure if the separation is what reduced the humming, or just the fact that the wires ended up located slightly differently from before. I will try shielding those wires and routing them appropriately straight away from the hum sources. Indeed it seems the safest bet would be to keep the power supplies in a separate enclosure.

 At the minimum hum layout I could muster, I listened to the combo: modded Tosh->Dynahi->Zu->HD650, for about an hour and a half. Even though there is still that trace of a hum, and has gone through very short break-in, I can easily say my Dynahi is sounding awesome. Once music plays, even at relatively low volumes, the music overpowers the tiny hum and basically I can't tell the hum is there, though for sure it should be rippling the music a bit. But the sound is awesome already anyway, way better than my Marantz receiver. Did some comparison, though not instantaneous A/B (don't have a switchbox).

 Voices and highs are much more clear in the Dynahi, it seems to have excellent "instrument separation" as some people might call it. I use that term because in comparison, the Marantz seems to put in particular voices and highs sort of merged with the warmer lows, showing less separation, or kind of a flatter 2D presentation, if I could use those words. The sort of "volumes or spaces of silence" between different sounds are so much larger and clearly defined with the Dynahi. Wonder if that's what people call blacker backgrounds. Bass is also powerful and plenty, and very controlled. All of this is quite remarkable because believe it or not I didn't find my Marantz too different from a Grace 901, and the difference with the Dynahi is significant. (Of course, placebo nonwithstanding, I didn't build that Grace, but I built this Dynahi 
	

	
	
		
		

		
		
	


	







) But anyway, in summary, for me the sound of this combo really makes me think of a truly high-end speaker setup, in particular one having a "high-current" power amplifier. Plenty of juice, effortless, and natural, full extended sound. Even if I pause the player and can detect that @#$@#$ tiny hum.


----------



## TrevorNetwork

The Grace 901 is poo imho. 
	

	
	
		
		

		
		
	


	




 Congrats on the Dynahi Raul. Now to solve that pesky hum problem. If you need a hand, drop me a PM.


----------



## rsaavedra

Ah certainly Trevor, thanks and YGPM


----------



## gsferrari

Houston!! We have music 
	

	
	
		
		

		
		
	


	




 Wow!! Raul - after exactly how long? How many days since you started the building process??

 Man you sure take a LOOOOONG time 
	

	
	
		
		

		
		
	


	




 But you do it right and it looks stunning.

 Congrats!


----------



## rsaavedra

Yes, the power supply warranty repair was almost a whole idle month. I got the boards of the first Dynahi boards groupbuy in August/06, so that's a total of basically 4 months from getting the boards till now. And it's still not ready!


----------



## kevin gilmore

Do not try and unsolder all those resistors, you will ruin the thing.
 Leave it alone and do this instead

http://home.san.rr.com/john1in2/DIY/...ges/closeR.JPG


----------



## rsaavedra

Looks like a "complication" as in a watch 
	

	
	
		
		

		
		
	


	




 Well but yesterday night I realized there are quite a few things that make me want to redo the Elma:

 1) The first one of course, wrong ordering of resistor, so it's working counterclockwise now.

 2) At one of the lowest volume positions, I think the fourth, there is a strange interference and I'm pretty sure it's a radio station, even though I can't discern any specifics in the speech. My guess is this is a bad soldering point? At no other position of the Elma I hear that. 

 3) With the source paused, at exactly min and max position of the Elma a low white noise comes out of nowhere. It looks as if the two extremes of the Elma have some steep peaks in the noise floor, not sure why. And it's not exactly the hum, some other white noise it seems. Not sure if this is related to my "hard zeros" in those positions. Instead of resistors, there are just exposed wires (little antennas?) in one of the halfs for those positions. [EDIT] After Kevin's suggestion, I'll add a 1K resistor (instead of a 100 resistor) between outputs of the Elma and the inputs on the amp boards.


----------



## rsaavedra

Wiring diagram updated, this one reflects exactly how I have everything right now:







 The chassis actually is *not* connected to the star ground right now at any point, and ground wires go separately from each of the channels in the Elma to the Ground Star Point. RCA ins, and Attenuator are for sure not touching the chassis, since they are detacched from it. Also, boards are not touching the chassis, I placed a vynil tile under them. So everything is connected within the enclosure, but not really touching the enclosure.


----------



## eweitzman

You have a ground loop in each channel. Follow this loop: 

 (A) ground connection on Elma switch
 -> wire to PCB
 -> ground plane/traces on PCB
 -> wire to star ground
 -> wire from star ground back to Elma switch (A)

 If there is any signicant resistance anywhere in these two loops, and any stray fields from the transformer(s) intersect either loop, you'll get hum.

 There are two ways to fix this:

 1. Try making the loops physically smaller by moving some wires. Try to squish this loop, which looks like an "O", into the shape of an "I".

 2. Remove one of the unnecessary redundant wires in the loop. I'd try the one between the Elma switch and the star ground. No guarantees, though, 'cause I'm not looking at the full picture right now.

 - Eric


----------



## sft

#2 
	

	
	
		
		

		
		
	


	




 I thought #1 works too.


----------



## rsaavedra

Ah but notice the ground wires between the boards and the Elma (#7 and #8 in the diagram) are not connected on the Elma's end, they are "floating" in the air, sort of. That's intentional, a one-ended shielding of the input signal wires between Elma and boards. So there can't be a ground loop there (if I understand it correctly). The Elma's ground points only reach the ground star (#1) through direct connections #4 and #5. Here the updated diagram again, for easier tracing of the numbers:







 I do believe the left-over humming is related to proximity with the PSU's, since moving precisely those ground wires that connect the Elma directly to the star ground point anywhere nearer the PSU's picks up the hum which goes louder quickly the closer it gets.


----------



## comabereni

Quote:


  Originally Posted by *kevin gilmore* 
_Do not try and unsolder all those resistors, you will ruin the thing.
 Leave it alone and do this instead

http://home.san.rr.com/john1in2/DIY/...ges/closeR.JPG







_

 

Good idea. Find a mechanical solution. 






 Only eliminate the intermediate gear or add (2) intermediate gears so the SA's turn in opposite directions 
	

	
	
		
		

		
		
	


	




. 

 Or (what I'd probably do), mount the SA and shaft completely inside the case with a gear that mates to a single volume knob shaft) --> the volume knob moves clockwise and the SA on the inside of the case moves CC-wise...

 -coma


----------



## rsaavedra

Getting fancier, I'm thinking of the following. Somehow fixing/bolting the stepped attenuator to the shelf or wall or floor, allowing the amplifier to be rotated around it, making the whole amplifier the knob itself! A little harder to move, but hey, I would have a clock-wise way to turn up the volume


----------



## comabereni

Quote:


  Originally Posted by *rsaavedra* 
_Getting fancier, I'm thinking of the following. Somehow fixing/bolting the stepped attenuator to the shelf or wall or floor, allowing the amplifier to be rotated around it, making the whole amplifier the knob itself! A little harder to move, but hey, I would have a clock-wise way to turn up the volume 
	

	
	
		
		

		
		
	


	











_

 

Consider capitalizing on your SA mistake by turning it into a sliding volume adjuster. Mount the assembly completely inside the case at an appropriate location, attach a pulley to the shaft and another pulley at a distance on the opposing end of your case and wrap a cable or belt around them. Attach the 'knob' (is that what you call it??) to an appropriate place on the cable so that volume increases as you move it to the right. If you have to mount the SA somewhere near mid-point in your chassis, just use three pulleys--one on the SA shaft and two at the L/R ends of the case. Wrap the cable around the SA shaft pulley twice to grip it tightly. I definitely would not rework the thing with a soldering iron--you have other (cool) options.

 -coma


----------



## gsferrari

Another thing you can do is have the volume knob as usual - use a gear inside and another gear on the stepped attenuator...this will make it turn in the opposite direction 
	

	
	
		
		

		
		
	


	




 If this was a pot then you could have simply changed the input and output wires (interchange). This will not work in this case 
	

	
	
		
		

		
		
	


	




 Dont rebuild the whole thing again 
	

	
	
		
		

		
		
	


	




 Another option is to mount the volume control on the side of the chassis (left side) so that the direction you turn it will "appear" to be correct if you use your left hand 
	

	
	
		
		

		
		
	


	




 Another option 
	

	
	
		
		

		
		
	


	




 Mount the SA inside the chassis facing backwards. Mount it high enough on the chassis that the knob will protrude a fair distance through the chassis. Make a grooved knob which will be easier to turn.


----------



## rsaavedra

I just used the soldering iron to remelt the soldering joints of the "radio station" position of the Elma, radio pickup gone now.

 Also attached the hum sensitive ground wires to the bottom panel of the chassis using Leviton cable ties (passing the ties through the ventilation holes). Turns out the best location of the star ground point and wires for minimal hum was basically anywhere but as close as possible to the bottom of the chassis. Lifting the wires increased the hum, but moving them horizontally over the bottom of the chassis didn't, as long as they didn't really get too close to the transformers.

 Another discovery: I was wearing the headphones listening to the amp when I was going to close the top cover. Not even yet touching the chassis with the cover, just hovering it over the amp the hum gets louder 
	

	
	
		
		

		
		
	


	




 And actually placing it on the amp (in contact with it), same effect, louder hum. So actually my amp is sounding better when it's "top-less" 
	

	
	
		
		

		
		
	


	




 The cause is certainly power supply/transformer related. When placing just part of the cover on top of the boards and Elma, but not covering the PSU's, hum doesn't change much. When placing the cover on top of the PSU's only, but not covering the boards and Elma, not much change either. When covering the whole amp, PSU's and boards and the Elma, then the hum increases.


----------



## gsferrari

Why dont you temporarily place the amp section outside the box or move the PSU sections out of the box - see if this helps ? If it does then a two box solution is your best option.


----------



## eweitzman

Quote:


  Originally Posted by *rsaavedra* 
_Ah but notice the ground wires between the boards and the Elma (#7 and #8 in the diagram) are not connected on the Elma's end, they are "floating" in the air, sort of._

 

Ah, but I do notice that you changed the diagram, making my suggestions seem off the mark. That's contrary to the rules of good etiquette...


----------



## rsaavedra

Quote:


  Originally Posted by *eweitzman* 
_Ah, but I do notice that you changed the diagram, making my suggestions seem off the mark. That's contrary to the rules of good etiquette... 
	

	
	
		
		

		
		
	


	


_

 

I didn't change that part. Added labels and recolored and marked things a bit better, but the ground wires (#7 and #8 now) between the boards and the Elma have never been connected on the Elma end in my diagram, or in my Dynahi for that matter. Probably you didn't notice before, but it was the same in the original diagram. That's something Kevin told me to do long ago.

 Some more news. Remember I didn't have the star ground connected to the chassis yesterday. This was because the ground connection I had planned for that now I needed for the other ground in the Elma, so that I could have #7 and #8 instead of just one ground wire for both channels in the Elma. Well, today I added another lead to the star ground, and connected it to the chassis. *Hum went down immediately!!!!!* If I unplug the ground-chassis connection, it goes up, together with white noise (this is with the cover removed from the top); if I connect it, goes down!!!! Really good news. Also, now the behaviour of the top cover is opposite of what I saw yesterday. When the amp is open there is some white noise pickup, as soon as I hover the top cover close enough on top (with chassis grounded), it dissapears!!!!! And then I can tell the now very tiny hum is not really completely gone, I guess still because of the proximity of the PSU's, but it's really much lower than yesterday, much cleaner background. Trevor probably I see what you meant now saying than keeping PSU's within the enclosure you could only get rid of 98% of the hum.

 Still at the first and max position of the Elma the white noise goes up a bit, even with the lid on top. So I'll have to change those 100 ohms resistors for 1K.

 I'm letting it break-in playing continuously through it. It is sounding great!!!!

 Guru yes future upgrades for my Dynahi will be taking the PSU's outside this case. But for now I'll keep it like this. Also the boards right now don't have the shield I built for them because I did the DC offset recently. Will add that, even though now after all the dealing with the hum and ground, shielding the boards I think is not as critical as I thought. Good grounding and the PSU's away are the critical conditions.


 What happened to the photos in Headfi? Can't see the list of photos in the bottom. Anyway, here's my lattest photo of the amp. Notice the red connector at the top of one of the pilars holding the input wires, that's the chassis-ground connection.







 Here's a close up of star ground point (green), held as close as possible to the bottom of the chassis by wire ties. The two orange caps are the +30v (wires marked red) and -30v (black) DC power distribution points:


----------



## rsaavedra

Tried the Dynahi with my SR60's, no surprise these are more sensitive, volume knob has to be much closer to the minimum position for similar volume as with the Senns. The hum is much more prominent with the Grados. Also, I realize, it seems to be mostly on the left channel, right channel is dead silent. Believe it or not I couldn't detect the hum was only on the left channel with the Senns, it's so minimal there. Also, part of it might be that right where I live there is some construction going on (Hurricane Ivan roof repairs), so it's not perfectly quiet right now, will check more later tonight.

 Also with the Grados, just by touching the volume knob, some white noise and interference appears out of nowhere, especially when the volume knob is at max position. With the Senn's I can only detect that by sliding my finger on the knob, not just by touching it. This is all with the case closed, and chassis grounded as from previous post.


----------



## dgardner

Not enough posts in this thread considering how many dynahi boards are out there... Something new to look at:

dynahi amp pcbs under construction
 (resistors matched to 0.1% or better)

dynahi amp heatsinks


----------



## rsaavedra

Those boards look great dgardner! The link doesn't seem to work directly for me, but I saw the image pasting the link directly in my browser.


 Tonight I'm doing some more listening of the Dynahi while it breaks-in. Paused the player and started changing the volume in the Elma. I'm realizing with the Grado's, switching the volume position in the Elma produces quite a very loud CRACK in the headphones. Quite too loud actually, makes me think it might not be very good for my ears or the headphones, even though it's over very quickly. Is this a sign of anything particularly wrong, or worth noting? With the Senn's there's also a loud crack, but it made me get concerned with the Grados where it appears louder and probably more dangerous.

 Hum level changes very little regardless of what position the Elma is set to. The loud crack happens regardless of whether the player is paused or playing music. Also, it is kind of erratic. Some times there's barely any crack, some times it's a loud little explosion.

 Also I'm positive about the following. Chassis is grounded as in some of my previous posts, but now keeping the top of the amp open for sure causes less hum than puting the top cover on it. As soon as the top cover is on both the PSU's and the right of the amp, particularly on the Elma, hum picks up in volume.


----------



## rsaavedra

Changed the resistors between Elma and boards from 100 ohms to 10K (Kevin recommended 1K, but I don't have those right now). The white, radio interference like noise is totally gone from both min and max positions of the Elma.

 Now, not sure if it's just my impression, but would the amp get hotter using these higher resistor values for the input signal? 

 Only the minor hum remains. Minute in the Senns, not so minute in the Grados. Also, hum definitely grows when placing top cover. Not only that, I notice the input signal wires between Elma and boards are extremely sensitive and microphonic. I can hear through the headphones whenever touching or moving them. If I move those wires closer to the bottom panel of the chassis, hum picks up, though not too much. Lifting the ground star point in front of the PSU's was much worse.

 Here's the latest pic, with the shield installed on the boards (Have to clean up all those fingerprints). The shield didn't reduce the hum though.




 High-res version


 Next step will be to replace those 10K's for 1K or 2K resistors, and definitely take the PSU's outside this chassis, far from the boards and input signals.


----------



## Woody

Of the few that have built the Dynahi, has anyone monitored the DC offset in normal use and after a period of time ?

 I'm struggling to believe that over time that the servo-less DC offset will not change, either while the amp is in use or as a result of component "aging" particularly in view of the high temperatures we're talking about.

 I cant recall the range of offset that the servo compensates for, but im curious to know whether over time it could get to a point where the servo cant cope and you end up damaging your heaphones ?


----------



## sft

no problem if you have a good solution for heat.
 It's VERY stable.


----------



## rsaavedra

Great news!!!!!! *My Dynahi is now without a doubt 100% HUM-FREE!!!!!* Both with Sennheisers and Grado's, absolutely no hum whatsoever, dead silent hum-free background.

 Guess what it took to make it hum free:




 Hi-res version.





 Hi-res version.


 You guessed it, taking the power supplies (see floor, bottom left corner on pics), outside the chassis, far far away from the boards and signal wires. 

 I used a halloween power cord, about 3 feet long, and some alligator clips to connect the PSU's to the now remote chassis. This is of course temporary. 

 You can see in the pictures, there's even some proximity between alligator clips and A/C power cords. Even so absolutely no hum, nada de nada. And I'm picky about this. But truly, hum is just no more whatsoever. The hum was undoubtedly caused by proximity of the PSU's.

 [size=large]So to all Dynahi builders, obvious recommendation: keep the PSU's and the boards in separate enclosures. And I wouldn't stack them, or place them one next to the other. [edit] I would place them at least 2 feet apart (see my long post further down).[/size]


 After doing that separation and happily realizing there was truly no hum at all anymore, I went ahead and replaced the 10K resistors I had between Elma and boards with 1K resistors, per Kevin's recommendation. This raised the gain, and with the player paused and using the Grados, at the last four maximum volume positions of the Elma (total of 24), a tiny amount of white noise surfaces from the pitch black background. Yet still no hum, and I'm thinking this white noise is probably related to the fact that the chassis is actually not fully closed in this improvised setup. And it won't be an issue for sure anyway, with the 1k resistors I couln't pass half the attenuator without ears hurting if listening to Grados.

 For the senn's the amp is absolutely 100% hum-free and 100% white noise free, regardless of Elma volume setting. Complete pitch black background all across. Actually I have been just engrossed listening mostly with the 650s. This is the time I'm still awake (3:00am) because of that.

 Finally I've completed my rig. Only need to put those PSU's in their own enclosure, and have a power umbilical cord connecting the two boxes. And now that it's sounding perfectly clean I should say, the Dynahi is a truly great sounding amp imho.


----------



## skyskraper

nice work. looking good. 

 i was going to build my dynahi and psu in seperate enclosures in a floor standing rack. put psu at bottom of rack and dynahi at top. not the 3 feet, but we'll see what happens.

 what do you guys reccomend for making connections between the psu and amp? xlr connectors with power cable or?


----------



## sft

xlr


----------



## skyskraper

would i be alright running 4 pin xlr with 4 conductor power cable. or would i be better off running one cable for the positive and ground, and one cable for negative and ground?


----------



## chillysalsa

Raul - how close can you put the psu before you start detecting hum?


----------



## skyskraper

also do you guys have any suggestions for volume controls besides stepped attenuators? if only i could afford one of those lovelyt 50mm penny and giles pots, theyre a joy to use. i wqas thinking of tracking down a couple of black velvets, would they be good enough for a dynahi? im assuming the blue velvet would be like putting retreads on a bentely


----------



## rsaavedra

About hum-free borderline separation, I really didn't try systematically because as you can see the whole setup wasn't on a flat surface. I basically placed things the way you see them in the picture at once. (So that I would know, if there was any hum remaining, for sure wouldn't be PSU related). Also with the aligator clips it was a bit dangerous to move things while power was flowing. My 3 feet estimate is just sort of a guess, but will let you know more precisely tonight, will try let's say with 4 inch steps, and with everything on the floor.


----------



## rsaavedra

One comment, now that I think about it, it's possible the hum wasn't caused only by proximity of the PSU's, because there is another variable in place. The fact that now the PSU's are not in touch with the amp's chassis, so that the signal ground now never flows through those PSU half enclosures surrounding the transformers.

 I'm going to try using a long wire just to connect the chassis of the amp with the metal enclosure of the PSU's and see if there's any hum pickup. Probably that would be a grounding problem. Even if it doesn't bring back the hum, I'll remove it anyway. I think I'd rather have the PSU's enclosures "floating" as they are now, or connected to AC ground actually, rather than to signal ground.


----------



## sft

Hi skyskraper,

 1)4pin or 3pin, one cable or two cable are all OK.
 2)1 encloser or 2 enclosers is OK
 3)Tokyo ko-on 2p2511s or 2cp2500 is fine.


----------



## skyskraper

ok cool. i was planning on keeping my psu in a seperate enclosure for the sake of cooling. i will work out the cabling arrangement down the line.

 the tkd pot seems very reasonably priced. would i be better off with one of these or a 100k log black beauty? my friends dad told me he has one he may be able to spare me. theyre both not far from each other in price...


----------



## chillysalsa

I am going to try a TKD pot in mine, but I have the opportunity to compare with a 25K Alps 23-pos stepped attenuator which I populated with Holco resistors.

 Raul: is there any chance you are picking up interference from the wiring in the building? That happened with my friend's computer monitor. The CRT was all 'wobbly' until it was moved to another room in the house.


----------



## skyskraper

in the case of mains related rfi would a mains isolation circuit with two transformers help you guys out? i was thinking of building one to run my studio gear off as a test to see whether it makes an improvement. if it shows up in cheap studio gear im sure it would make a difference in 'phile setups. unless i have the purpose of mains isolation circuits mixed up.


----------



## rsaavedra

Good point chillysalsa, very possible. I have an Ultimate Power Outlet that I didn't use yesterday for this test. Will try that as well tonight to see if the faint white noise at max volume with the Grados (player paused of course) goes down or even dissapears.


----------



## chillysalsa

Try the conditioner, and then try the amp in another room. It maybe your are in some kind of Bermuda triangle of EMI/RFI at that location.


----------



## rsaavedra

Placed everything on the floor. Power supplies on the left, as in the pics, guts facing upwards, transformers on the left. Amp chassis in the middle, and player to the right of the amp, and very near it, so that I could move the amp easily closer or farther away from the PSU's with no problem, leaving the player in the same place. Player and PSU's powered by my Ultimate Outlet, not by the surge protector you see in the pics. The ultimate outlet is in the middle and far in front of the amp chassis.

 The amp chassis is relatively light now, PSU's are not in it after all. So it's easy to move it, with the provision of the power, input signal, and headphone wires dangling from it though. In any case, with the setup as described, I could move the amp while having it powered and while wearing the headphones and having the player playing or paused. This was good because I didn't want to turn on/off the amp for every distance test, and it also allowed me to do a sort of continuum evaluation of when the hum picked up, for uninterrupted finer position adjustment.

 I started with the lelf edge of the amp chassis at 3 feet from the right border of the PSU's. Note that my amp chassis doesn't have that left and back panels right now. Connected my Grado SR60, turned on everything, paused the player, and sent the Elma to max volume. No hum whatsover, but the faint white noise pick up is there, same as yesterday night. So the ultimate outlet is not getting rid of it, which makes me think as I originally thought, it is picked up by the input signal wires. More on the sensitivity of those later.

 Because of that minor "shhhh" of the white noise, I sent the Elma to 3/4 of its range, and the shhhh is gone, amp is again exhibiting pitch black background, no hum and no hiss. This remains all the way moving the amp chassis closer to the PSU's down to 2 feet, and also just 1 foot. In all of this I'm making sure the wires are not getting close to A/C wires. More on that later.

 So that's more or less my starting point, with perfectly clean silence from the amp, left border of amp chassis 1 foot away from right border of PSU's.


*Horizontally*, if I move the chassis closer to the PSU's, I start to hear the hum when the gap shrinks to about half a foot (or 6 inches). With that gap at 5 inches the hum is barely there, but no doubt is there. 6 inches is about borderline for me. Given the position of the boards assembly inside my amp, this means that the borderline separation has the star ground point in the amp chassis (right in front of my heatsinks) at about a foot away from the right border of the PSU's. And the input signal wires, to the right of the boards assembly, are about a foot and a half away. 

 Now here's an interesting thing I wasn't expecting. Because I wanted to see how the hum peaked, I started moving the amp closer and then lifted the amp, and started hovering it over the PSU's. And here goes the vertical point in my observations.

*Vertically*, with the amp chassis above the PSU's, I have to lift the amp at least 2 feet above them to get rid of the hum!!! Obviously these magnetic fields have some peculiar geometry around the PSU's. But maybe not so. I find these 2 feet vertically consistent with the fact that horizontally, hum starts to be picked up when input signal wires are about 1.5 feet away from and to the right of the PSU's. And horizontally, the boards assembly is in between them actually, probably allowing for a little shorter separation with no audible hum pickup.

 After realizing this, I went bold to truly find out how powerful this nasty hum introduced by proximity with the PSU's could get. Between the RCA ins' and the Elma, and also between Elma and boards, my input signal wires are silver coated stranded copper, teflon jacket wires, not shielded. I twisted paired them with their own ground wires, of exact same make. *Placed those input wires directly on the transformers of the PSU's!* The hum went so loud as if there was a testing humming signal, bearable but way too loud for an interference pickup. Interestingly, moving the input signal wires close to and touching A/C wires I couldn't pick up any hum. This even with the Halloween powercord, which I know is not shielded. So maybe this is a "master of the obvious" statement, but *proximity between input signal wires and in particular the transformers in the PSU seems to be the real cause of the hum pickup.*


 Another test I did, now with respect to grounding. Used a long wire to connect the amp chassis (which is connected to signal ground) to the PSU's chassis, e.g. the same situation you get when having the PSU's inside the amp's chassis. This didn't change anything. No hum pickup if both are sufficiently apart, e.g. at least half a foot horizontally, at least 2 feet if directly above the PSU's.

 Yet another test, connected A/C ground to the PSU's chassis (having previously disconnected the latter from the amp's chassis). No difference either. I think this is the grounding scheme I'll use for the PSU's enclosure.

 Yet another test, moving the DC power wires close to A/C wires or the PSU transformers, no hum.


 Remember this was all with the very sensitive Grados, Elma set at 3/4, which for the Grados is a lot. For me, this amp has to have the Elma maximum no higher than about 1/3 for loudest comfortable listening with the Grados. With the Senn's it can go past the middle and still be bearable, depending on the gain in the CD. Also keep in mind, for these tests my amp chassis had no left wall or back panel. And PSU's are not caged in their own fully closed metallic box. And I really really hate hum in audio equipment. So with respect to hum pickup, YMMV.


 [size=small]*Conclusion: the interference these PSU transformers cause is powerful. My updated suggestion then, after these experiments: keep amp, in particular input wires and star ground point, at least 2 feet apart from the PSU's enclosure. With amp chassis fully closed, and PSU's enclosed in their own metallic enclosure, that distance might be reduced, but not sure how much till you start picking up some hum though, at least listening with attenuator at high setting, and using low impedance headphones.*[/size]


----------



## gsferrari

Raul - your case is not grounded right? How about yout input RCAs?? Are they insulated from the case or not? If they are NOT then perhaps the case is picking up the stray fields and the RCA's are a ground to them...there is a loop right there.

 Just a suggestion - I have no idea how you have implemented the case/case components.

 Now - this is what I had planned as a layout (ignore the grounding scheme...bunch of crap 
	

	
	
		
		

		
		
	


	




 )






 the grey stuff is ferrite blocks or some other form of shielding.


----------



## rsaavedra

Quote:


  Originally Posted by *gsferrari* 
_Raul - your case is not grounded right? How about yout input RCAs?? Are they insulated from the case or not?_

 

I believe the case is perfectly grounded. Either of the grounding configurations I mentioned in my previous post are perfectly ok and totally hum-free, provided PSU's are far enough.

 The RCA's are not mechanically connected to the case in this test, since the back panel is near the PSU's (I soldered the wires between PSU and power inlet/fuse, so for now the back panel remains close to the PSU's). But electrically the RCA's and the amp chassis are connected, since they all have direct connections to the star ground point (RCA's ground going through the Elma, then to star ground). Also, even if the RCA's were attached to the back panel, the only connection between their ground and the star ground would still be just their own direct wires. When attached to the case there is no direct electrical contact between RCA's and chassis, thanks to the nylon washers the RCA's came with (these are the Cardas RCA's from Moon-audio). So the grounding I'm using, as shown in a diagram in a previous post, I'm confident is correct, especially given the results I observed in these tests.


----------



## rsaavedra

Quote:


  Originally Posted by *gsferrari* 
_the grey stuff is ferrite blocks or some other form of shielding._

 

If your PSU's will be Condor's, or similar ones with transformers like the Condor's, I doubt any shielding within the same case will truly kill the hum. The transformers will be too inevitably close to the signal wires if in the same case.


----------



## dgardner

I stop listening to the new boards after 3 hours and started the enclosure work. Tried something to keep it running cooler with the heatsinks OUTSIDE.

Dynahi - Dynamite in Heeger Mod-U-Line - Top View (jpg, 352KB)

Dynahi - Dynamite in Heeger Mod-U-Line - Side View (jpg, 299KB)

 EDIT:/ Only listened to Dynahi mode, did not have the guts to listen to Dynamite mode yet. Gotta go back to the power supply boards and get them working...


----------



## skyskraper

thats the sort of thing i was thinking about. running the heatsinks on the outside then mounting them to the case with the "T" stem of the heatsinks coming in to the case.


----------



## drubrew

Something I would recommend is not using brackets to mount your heatsink to the boards. Mount them directly to the boards. And make sure to mount them with the fins running up and down. The transistors should be screwed to the heatsink not a bracket. This will insure maximum heat dissipation to the heat sink instead of sending it through the braket first and them the heatsink. When I get a chance I will post pictures of mine.
 Drew


----------



## skyskraper

so would it be ok using a heat sink like this:






 then cutting an opening in the front or rear panel of the case that would let me fit that stem in, bolting the body of the heatsink to the case panel so that i would end up with a configuration like this:






 if this is ok, for the sake of aesthetics would there be any problem stripping the black paint and getting the sink anodized natural to match my intended enclosure?


----------



## sft

Hi skyskraper,

 Your solution is the best so far i've ever seen.
 The temp. will be lower even than 70 C .(case by case)


----------



## skyskraper

sweet, well i'll defn be trying it out. my dynahi will be in normal stereo operation, not balanced, so only one pair of boards. 

 the only thing im concerned about is the thermal resistance of the lorlin rotary switches i will be mounting on the same panel. hopefully the exposed panel (i only intend to have a 200mm heatsink across the front) doesnt get too hot. ah well. it'll be a long time until im at the case work stage of my dynahi anyway 
	

	
	
		
		

		
		
	


	




 edit: i came up with this solution because i intend on housing my dynahi in a 2ru rack case, in a rack in my room. having heatsinks hanging off the side would be useless to me, plus im lazy and don't want to get L bends and drill and cut etc, the T shaped heatsink seemed like an easy way out. 

 having them at the back would mean id forget about them and theyd get dirty, plus the power supplies of the other gear in the rack (dont worry there will be minimum 2ru space to my next item) are all at the back, so want my boards as far from AC as possible in the rack....

 plus front mounted heatsinks anodized to match my case would look cool i think


----------



## sft

The lorlin rotary switch is OK.
 if you care, just add two teflon washers.


----------



## skyskraper

would you or anyone else be able to reccomend me a rotary switch 4p3t that is of better quality (or quality that would match the dynahi) that isn't going to send me broke. somewhere around the 10-15usd range is what id be willing to stretch to....


----------



## skyskraper

hey i had a pm asking me about these heatsinks so i took the liberty of getting pricing on quantity of 40, in case there are a few of you out there that would want to group buy if you can't find them. 

 if you guys want to group buy, the pricing works out to be quite cheap, but im in australia and would be shipping them individually from australia. unless someone wants to co ordinate it from the US, i could ship them all as one then and they be sent out individually. 

 anyway here are some details on them:

 they have a 35mm wide by 6mm thick flange for semis or PCB’s. 
 theyre available in three widths:
 Length: 150mm
 Thermal Res. : 0.78°C/W
 Length: 200mm
 Thermal Res. : 0.60°C/W
 Length:300mm
 Thermal Res. : 0.39°C/W

 theyre 75mm high, 46mm deep. 

 if theres interest i can start a new thread about it. let me know guys


----------



## eweitzman

Quote:


  Originally Posted by *skyskraper* 
_...but im in australia_

 

I thought they looked like the heatsinks that your fellow Australian Hugh Dean sells with the AKSA amp kits.

 You won't need to affix standoffs to the board and the chassis bottom as shown in your sketch. There will be 8 bolts running through the heatsink ledge, transistors, and board that will keep everything in place.


----------



## skyskraper

hehehe yep prolly the exact same source.

 fwiw here are the prices: 
 H 0535 $10.98, H 0538 $12.80 and H 0542 $18.85.

 please note these are my prices in AUD. so they work out quite nicely in USD. $1usd buys aprox $1.3aud. 

 if you guys are keen i can look in to weight/packaging prices to send individually or as a whole....


----------



## dgardner

Are the fins bonded or is the T-bar bonded? or Both? One or the other must be, because you cannot extruded this shape.


----------



## skyskraper

iirc the stem section is bonded or welded. i dont know why but welded sticks out in my mind hugely for these heatsinks. i will try check before i leave


----------



## eweitzman

Quote:


  Originally Posted by *dgardner* 
_Are the fins bonded or is the T-bar bonded? or Both? One or the other must be, because you cannot extruded this shape._

 

The very-similar-looking heatsinks that came with my daughter's AKSA kit were one piece, not bonded. From the surface finish, they appear to have been cast, not extruded. All the surfaces were a bit rough except for the mounting ledge. It was machined but for a small area near the junction with the fins.


----------



## skyskraper

i emailed the supplier. more details shortly


----------



## skyskraper

yup theyre die cast, one of the sides of the stem is machined for semi's 
	

	
	
		
		

		
		
	


	




 can anyone answer me on the resistor question?


----------



## sft

Dale RN60D is good enough.
 1)match them
 2)solder them a little higher such that there is a short distance from the PCB.

 Where is my english dictionary?


----------



## skyskraper

oops sorry i must have posted it in another thread, i meant for the vishay dales, i havent used them before but intend to on this and other amps i build, to get a match, how many do you guys find you need? i find one in four for generic metal film 1% resistors come out bang on. i just need to know how many to order


----------



## intlplby

has anyone ordered the L-shaped aluminum from Onlinemetals.com for use with the HS-TWS from Nebraska Surplus?

 if so which size and type piece of aluminum did you buy?


----------



## Edwood

Are those toggle switches on the right illuminated?

 -Ed


----------



## skyskraper

i think so, they were discussed in a thread about illuminated switches/buttons last month


----------



## Edwood

If you mean this thread: http://www6.head-fi.org/forums/showt...minated+switch

 I don't see where they mention those little switches. 
	

	
	
		
		

		
		
	


	




 -Ed


----------



## chillysalsa

Those illuminated toggles are available here in Toronto at Active Surplus. They are new, and I recall they were rated for 12V, but I'm not sure now. $5 I think for each.


----------



## Edwood

Quote:


  Originally Posted by *chillysalsa* 
_Those illuminated toggles are available here in Toronto at Active Surplus. They are new, and I recall they were rated for 12V, but I'm not sure now. $5 I think for each._

 

Any sources online? 

 I used to live near Toronto, but am a lot farther away now. 
	

	
	
		
		

		
		
	


	




 -Ed


----------



## chillysalsa

You could call them and enquire if they can ship them to you:

http://www.activesurplus.com/ 

 If not, I could pick them up for anyone and ship them out. It would have to be in the new year though.


----------



## intlplby

http://www.mouser.com/catalog/620/1019.pdf


----------



## chillysalsa

FINALLY finished! I told ya'll it was a holiday season's project, and by my last day off I was listening to the unit. Pictures to follow in the 'pics of your builds' thread, but for now I am listening to Smashing Pumpkins, 'Adore'. AMAZING! This amp is so detailed, clear, sweet, articulate, clean, and powerful at the same time. I'm having many of those "I never heard _that_ before" moments!


----------



## intlplby

i don't have access to a drill press..... can anyone give advice on how to drill the L-brackets accurately so that i can mount both the board and heatsink to it 


 i was planning on drilling the heatsinks with a 9/64" bit and then tapping it with an #8/32


----------



## Edwood

Use a center punch to "dent" the center of the holes you are going to drill.

 Then clamp the piece down, and drill carefully.

 Try not to use a an excessively thick piece.

 -Ed


----------



## chillysalsa

After reducing the gain by changing the resistors, I noticed that the stepped attenuator was making a faint click between the first 5 positions, and that #4 of the volume steps was picking up really low static / RFI or something. 

 I had the box open for upwards of an hour, trying to reposition wires, checking / reflowing the solder joints on the resistors at Position 4, and nothing was really making it go away. 

 Then I removed the cheapo Radioshack headphone extension cord: all the noises went away. OMG... check the simple things FIRST! 

 Radioshack: behold my fist shaking in your direction!


----------



## Woody

Did you replace it with another extension cord or just remove it ? I wouldnt be surprised if you found the noise was due to the length of the headphone cable rather than Radioshack quality in this instance.

  Quote:


  Originally Posted by *chillysalsa* 
_Then I removed the cheapo Radioshack headphone extension cord: all the noises went away. OMG... check the simple things FIRST! 

 Radioshack: behold my fist shaking in your direction!_


----------



## Woody

Now there are a few people with working Dynahis, those with the Elma stepped attenuators, do you have any comments ?

 Any noise as volume increased\decreased. i.e clicks or pops ?
 Is 24 positions enough ? Without a gain switch ?


----------



## sft

1)all the same slight clicks in every position, with different headphone(headphone line).
 It's normal.BTW, my switch is not Elma.
 2)Is 24 position enough? It's depends on you(and your headphones). It's not enough for me.


----------



## Woody

Quote:


  Originally Posted by *sft* 
_1)
 2)Is 24 position enough? It's depends on you(and your headphones). It's not enough for me._

 

Reading some of the other threads about stepped attenuators, this seems to be a common complaint. I know KG also has problems with anything less than 40 steps.

 I know reducing the gain of the amp alleviates the problem because you should be able to set the gain so that the 24th position is just too loud using your quietest source, but it doesnt address all the un-used lower end positions.

 So what about choosing say a 20K stepped attenuator, but then adding another resistor to it externally top and bottom for each channel ? OK you would never be able to set zero volume, but you could use a separate mute switch for that.

 Alternatively, leave the top one of those two extra resistors out and adjust the gain of the amp to set the max volume.

 Nothing clever here I know, but can anyone see any downsides to this approach ? I'd have thought that at least doubling the resolution would be possible. Although I accept it may not be practical if you have to accomodate many different headphones.

 Another advantage is that you effectively limit the max volume at the same time, protecting your headphones and your hearing.


----------



## sft

1) 1.0dB resolution is enough absolutely.
 2) 24 position(3dB resolution) and +-1.0dB gain switch(on-off-on)
 -> 72dB range. the range is wide enoung for every headphone
 3) shortcoming: not user-friendly


----------



## chillysalsa

I use the Alps 23POS with Holco resistors: no audible clicks at any position when you switch volumes. I'm using gain of 5, and it gives me about 6-8 positions of useable volume control with Grados. I think lowering the gain to 3 would be more ideal for these cans, but I may get Senn's in the future, and don't want to put a gain switch in the signal path unless I really have to.

 The 6ft Radioshack extension chord was useful for me though... I think I will make my own, with shielded cable and higher quality connectors, and see if it picks up RFI again.

 So how would one go about wiring the +/- 1db switch?


----------



## sft

lower R20 by paralleling a resistor->-1dB
 lower R21 by paralleling a resistor->+1dB
 just use on-off-on type switch.


----------



## NOTHINGness

Has anyone looked at using the TI PGA2311 for a volume controll? Using a rotary encoder and microcontroller, it shouldn't be too hard to get it to work.


----------



## chillysalsa

Which are R20 and R21?


----------



## ble0t

Quote:


 Has anyone looked at using the TI PGA2311 for a volume controll? 
 

The problem there (as I see it) is that you'd need another power supply (+/- 15V and 5V) and some people would have a hard time programming the controller. It might be easier to just use a preamp if you have one. 

 Having said that, I do know someone who has used the chip, and it works quite nicely.


----------



## philodox

Quote:


  Originally Posted by *chillysalsa* 
_I think lowering the gain to 3 would be more ideal for these cans, but I may get Senn's in the future, and don't want to put a gain switch in the signal path unless I really have to._

 

Is there really any danger of audible degredation in using a gain switch?


----------



## sft

Quote:


  Originally Posted by *chillysalsa* 
_Which are R20 and R21?_

 

2000 and 100 on silkscreen


----------



## chillysalsa

Thanks sft,

 I see. Those are the resistors controlling gain, so one would have to calculate the correct R values to give you 1 db in either direction, based on the gain you have.

 I still don't know if having a gain switch or a fine +-1db adjustment switch will affect sound quality, so I may try it later. I just know that putting switch contacts into the signal path, and it will mean running jumpers to the resistor pads... and I'm a bit of a purist so the idea isn't turning me on. I guess trying it will only determine if the affect is even audible.


----------



## viper32

Can someone tell me where I can get a P & G attenuator with 4 decks for a balanced setup. Are these hard to get? What would something like this cost? 

 Also looking for a very high quailuty attenuator with 48 steps or more, just incase the cost on the P & G is too high. 

 Thanks


----------



## rsaavedra

Quote:


  Originally Posted by *Woody* 
_Now there are a few people with working Dynahis, those with the Elma stepped attenuators, do you have any comments ?

 Any noise as volume increased\decreased. i.e clicks or pops ?
 Is 24 positions enough ? Without a gain switch ?_

 

When player is paused, no clicks at all changing the position of the Elma. If music is playing, then changing the position causes a very loud pop/crack most of the times.

 For the Senn's the 24 positions is perfect imho, no gain adjustment needed. Listenable up to mid position comfortably, starts to get loud after that for most recordings, but I can listen to some even at position 14 without discomfort. With the Grado's, howevere, it starts to get too loud after 1/3 of the positions, and with the Shure E3c's, just the first few positions are listenable, gets too loud too quickly after that. So for low impedance/high sensitivity headphones, a gain switch would be highly advisable I think.

 (My Elma is setup as a 50K btw)


----------



## Woody

Thanks Raul, is it severe enough to make you think it cant be good for your headphones ?

 I've been looking at comments on other forums, and most people report low level clicking as 'normal' with all of the well known SAs, but you've got me worried now 
	

	
	
		
		

		
			





  Quote:


  Originally Posted by *rsaavedra* 
_... changing the position causes a very loud pop/crack most of the times._


----------



## Edwood

Perhaps grounding the metal part of the Elma might help? It's a stretch, because grounding the metal part is usually for when there is buzzing when touching the shaft.

 -Ed


----------



## Pars

Quote:


  Originally Posted by *viper32* 
_Can someone tell me where I can get a P & G attenuator with 4 decks for a balanced setup. Are these hard to get? What would something like this cost? 

 Also looking for a very high quailuty attenuator with 48 steps or more, just incase the cost on the P & G is too high. 

 Thanks 
	

	
	
		
		

		
		
	


	


_

 

I think Dr. Gilmore has gotten a couple of these (maybe 2 deck) from a friend in England. I think he said to buy one of these would run around $400 (IIRC), so yes, they are expensive. I know P&G is used alot in studio/prof. equipment, and I haven't googled onto anyone who sells the attenuators. Perhaps buying direct from P&G is the only way?

 I would also look at Goldpoint.. they are another of his favorites, and don't seem to be crazy expensive (relatively... 
	

	
	
		
		

		
		
	


	




 )


----------



## skyskraper

i looked in to getting a stereo version of their rf15 and $400usd sounds about what i was quoted. try contacting the distributors in your area for pricing on the four deck model....


----------



## rsaavedra

Quote:


  Originally Posted by *Woody* 
_Thanks Raul, is it severe enough to make you think it cant be good for your headphones ?_

 

It can be severe enough in some cases. Also, severe enough for your hearing. So after I realized with the player paused it doesn't click, I always pause before changing the volume. I don't change the volume that much now either, since I know more or less where the position should be for the recordings I listen to the most.


----------



## chillysalsa

Very strange Raul! Do you know if anyone else with the Elna installed has the clacking? 

 I get absolutely zero noise when I switch volumes using that Alps stepped attenuator unit. Is there a difference in their design compared to the Elna? Does "make before break" have something to do with it?

 Anyway, I have finally posted PICS of my Dynahi.


----------



## rsaavedra

Quote:


  Originally Posted by *chillysalsa* 
_Very strange Raul! Do you know if anyone else with the Elna installed has the clacking? 

 I get absolutely zero noise when I switch volumes using that Alps stepped attenuator unit. Is there a difference in their design compared to the Elna? Does "make before break" have something to do with it?

 Anyway, I have finally posted PICS of my Dynahi._

 

Cool pics Chillysalsa, congrats!! About someone else having the clacking, haven't heard of anyone else noticing that yet.


----------



## eweitzman

Quote:


  Originally Posted by *chillysalsa* 
_Very strange Raul! Do you know if anyone else with the Elna installed has the clacking? 

 I get absolutely zero noise when I switch volumes using that Alps stepped attenuator unit. Is there a difference in their design compared to the Elna?_

 

Recall that Raul had all sorts of strange issues due to his grounding scheme. It may not be the switch that's at fault.

 - Eric


----------



## rsaavedra

Quote:


  Originally Posted by *eweitzman* 
_Recall that Raul had all sorts of strange issues due to his grounding scheme. It may not be the switch that's at fault._

 

There's zero grounding issues in my amp. You probably missed my post with the power supplies separated from the boards. After connecting signal ground to the chassis (which I did long time ago), the leftover humming was for sure caused by proximity of the power supplies. Absolute zero humming after they got moved far from the boards. Poping happened in the Elma before and after that, and both with the Elma totally dettached from the amp box, as well as with the Elma in contact with chassis and signal ground.

 My signal ground btw is still "floating" in the amp box though. It's not in contact with earth ground (since that might cause ground loops). In any case I really can't be 100% certain it's the Elma, might indeed be related to something specific to my setup. But grounding issues my amp has had zero for quite a while now.


----------



## drubrew

Ok I'm close to a final product, but having some issues. My headphone amps are both oscillating at pretty hefty levels at about 5MHz. They pass audio, but, of course, it sounds pretty bad, the sound is very thin. The grounding seems OK. Any ideas? The DC offset drifts. Not by much but I cant get a constant offset of zero. I'm using an Elma ladder volume control. Each click of the dial gives a pop as I increase the volume. Should I increase the value of the 33pf cap to resolve this?
 Thanks
 Drew


----------



## dip16amp

Quote:


  Originally Posted by *drubrew* 
_Ok I'm close to a final product, but having some issues. My headphone amps are both oscillating at pretty hefty levels at about 5MHz. They pass audio, but, of course, it sounds pretty bad, the sound is very thin. The grounding seems OK. Any ideas? The DC offset drifts. Not by much but I cant get a constant offset of zero. I'm using an Elma ladder volume control. Each click of the dial gives a pop as I increase the volume. Should I increase the value of the 33pf cap to resolve this?
 Thanks
 Drew_

 

Thats probably from either the power supply or source. Hope you aren't using a lab type power supply. Use the dynahi power supply.
 Try disconnecting the source and connecting the input to ground and see if it stops oscillating and stabilizes the DC offset.


----------



## drubrew

Not using a lab power supply. Using both the Dynahi Power Supply and one of my one designs. No source was attached. Only a scope on the output end to measure the oscilation. Or a meter to measure DC offset.


----------



## dip16amp

Quote:


  Originally Posted by *drubrew* 
_Not using a lab power supply. Using both the Dynahi Power Supply and one of my one designs. No source was attached. Only a scope on the output end to measure the oscilation. Or a meter to measure DC offset._

 

Maybe cut off the middle flying pins off the JFETs. I've never seen anyone leave those on like that.


----------



## drubrew

Yes I have not gotten around to cutting those, but I cant believe that is the problem. Looks like rsaavedra also has the same pop problem when turning his Elma switch. This I think relates back to the fact that the circuit is trying to null out. And each time we switch the control another notch we are disrupting the null process.
 Drew


----------



## rsaavedra

Quote:


  Originally Posted by *drubrew* 
_Yes I have not gotten around to cutting those, but I cant believe that is the problem._

 

Shouldn't be, I have popping, and I cut those legs at very early stages of populating the boards.


----------



## dip16amp

Quote:


  Originally Posted by *drubrew* 
_Yes I have not gotten around to cutting those, but I cant believe that is the problem. Looks like rsaavedra also has the same pop problem when turning his Elma switch. This I think relates back to the fact that the circuit is trying to null out. And each time we switch the control another notch we are disrupting the null process.
 Drew_

 

The oscillation problem could be caused by picking up noise on those leads. The switching pop from the elma is another problem that I think someone added a 100 ohm resistor between the amp and board and the attenuator to reduce it. The DC servo takes minutes to slowly null the offset and would not cause the pop. Is the DC offset less than 10 mV? 
 Are you using a 30VAC transformer? What voltage is measured in and out of the LM338 regulators?


----------



## Woody

Quote:


  Originally Posted by *drubrew* 
_Not using a lab power supply. Using both the Dynahi Power Supply and one of my one designs. No source was attached. Only a scope on the output end to measure the oscilation. Or a meter to measure DC offset._

 

Hmmm...

 1) Have you used the scope to check the power supply (Some people had oscillation problems with the original dynamic Amp PSU ) ? 
 2) HAve you tried it without the servo amp (Although I cant see this oscillating at 5MHz) ? 
 3) Have you tried shorting the amplifier input rather than relying on the an open input and the impedance of the volume control ?
 4) Is the power supply transformer and PSU regulator board located sufficiently far away from the amp ?
 5) Is the 5MHz noise still present if you put a dummy headphone load on the output ?


----------



## drubrew

Have not put the power supply on a scope. The power supply I am currently using is not the Dynahi Prototype PS but one I came up with. I measured the voltage to the amp boards as 28+volts but that is as far as I took that. I have the power supply mounted on a piece wood and it is a sufficient distance from the chassis containing all the amp boards/connectors and such. I'll try the other suggestions this wknd. Need to relook at all the grounding pts.
 Thanx for the help, keep it coming.....
 Drew


----------



## kevin gilmore

Here is the info on the P&G pots.

http://gilmore.chem.northwestern.edu...on '04.doc

 Available in up to 6 channel versions.
 4 channel version about $500
 contact info at the bottom of the document.


----------



## Edwood

If the Welborne Lab's digital stepper was compatible with a rotary encoder, I would've liked it better.

 -Ed


----------



## Edwood

Argh!

 Trying to get 2SC3381 transistors is hell. MCM is backordered for months.

 BDent's website is down, and they are waaay overpriced compared to MCM.

 Is there another source for 2SC3381?

 Googling 2SC3381 gives me nada.







 -Ed


----------



## MisterX

Try THLaudio
http://www.thlaudio.com/ICsmn.htm


----------



## walangalam

drubrew,

 have you fixed your oscillation problem? I'd be interested to know what you did if its gone.


----------



## Edwood

Quote:


  Originally Posted by *MisterX* 
_Try THLaudio
http://www.thlaudio.com/ICsmn.htm_

 

Unless they are butt cheap, overseas shipping is gonna kill the deal. THey have yet to respond to my email inquiry. I'll give another day or so.

 Otherwise I guess I'm going to get gang raped by MCM and BDent. 
	

	
	
		
		

		
		
	


	




 -Ed


----------



## drubrew

No things are actually worse now. Once the amp warms up the oscillation hits it's roof and then the signal cuts out. This happened after I rewired the grounds to match the previous posts I have seen in this thread. Going back to my original grounding layout. I have also ordered some top adjusting trim pots. I have side versions that were laying around that I used. They are a bitch to adjust. I think part of my problem is here. As soon as they arrive I will retry one last time to adjust everything. If still a mess the project gets shelved and I go back to playing with tubes. Much easier to trouble shoot.
 Can some one give me the voltages across R23, R27 and R37? And would someone please double check the first repliers numbers. Much appreciated. 
 Drew Baird
 Moon Audio


----------



## Pars

Quote:


  Originally Posted by *Edwood* 
_Unless they are butt cheap, overseas shipping is gonna kill the deal. THey have yet to respond to my email inquiry. I'll give another day or so.

 Otherwise I guess I'm going to get gang raped by MCM and BDent. 
	

	
	
		
		

		
		
	


	




 -Ed_

 

I know that Justin at headamp has used Fibra-Brandt, but they are in Germany, and he mentioned they are only competitive for large orders.


----------



## skyskraper

email the guys at www.futurlec.com they dont list a lot of transistors on their site but they do have a tonne of the gilmore transistors. shipping is cheap too!


----------



## Pars

Never dealt with them, but in gsferrari's parts group buy thread, someone came up with these guys:

http://www.electronix.com/

 no idea if the parts are actual Toshiba or what they are...


----------



## skyskraper

i buy a heap of stuff from futurlec, they stuffed up my dynalo order, but they fixed it up pretty quickly and painless. 

 the 2sc3381 is $0.78usd from futurlec.


----------



## dip16amp

Quote:


  Originally Posted by *drubrew* 
_No things are actually worse now. Once the amp warms up the oscillation hits it's roof and then the signal cuts out. This happened after I rewired the grounds to match the previous posts I have seen in this thread. Going back to my original grounding layout. I have also ordered some top adjusting trim pots. I have side versions that were laying around that I used. They are a bitch to adjust. I think part of my problem is here. As soon as they arrive I will retry one last time to adjust everything. If still a mess the project gets shelved and I go back to playing with tubes. Much easier to trouble shoot.
 Can some one give me the voltages across R23, R27 and R37? And would someone please double check the first repliers numbers. Much appreciated. 
 Drew Baird
 Moon Audio_

 

The voltage across the 100 ohm R23 resistor should be about 2.87 volts.
 The voltage across the 5K ohm R27, R29, R37, and R39 should be about 5.00 volts.
 The voltage across the 500 ohm R30 and R40 resistors should be about 1.00 volt.
 The voltage across the 300 ohm R17, R18, R25, and R26 resistors should be about 4.30 volts.
 The voltage across the 20 ohm R1-R16 resistors should be about 0.74 volts.


----------



## drubrew

God Bless you. I love more info than requested. Hopefully I can get this dog up this wknd.


----------



## drubrew

Man finally got past the nonsense. The opamps were fried. This didn't help. Changing the trim pots to top instead of side mount, really helped. I just couldn't get a good offset tune in on the horizontal version. I will scan in the schematic for the Power Supply we came up with. No Heat from this version. The same 30v toroid can be used for either supply so you can decide which you like better. I may have some left over parts for sale for the Gilmore power supply and for my supply if anyone needs at cost.
 Need to do some final buttoning up and then I will post pictures and will burn this thing in for reviewing.
 Cheers and thanx for all the help.
 Drew


----------



## Woody

Quote:


  Originally Posted by *drubrew* 
_Man finally got past the nonsense. ....Drew_

 

Did you find anything that might be an inherent problem ? Or were the problems down to component faults ?

 What prompted the alternative PSU design ?

 Just curious as I will be attempting the amp/psu builds soon.

 Rgds


----------



## drubrew

Besides the bad opamps screwing with the offset and constantly drifting, having the horizontal trim pots made life very difficult. Just couldn't get a screw driver in there properly to adjust. I also did several ground wiring schemes. The last one took care of the popping in the Elma switch. I have the ground now running from the inputs to the Elma switch to the amp boards. I have the Output jack ground tied to the power supply input ground on the amp board. I have both boards grounded from this ground to each other. Then the ground from the Amp board thru the power supply to the ground on the IEC. The IEC is then grounded to chassis. I saw some other posts where everything was being star grounded. This didn't work well with my amp. 
 The reason for the other power supply is, at the time there was no power supply designed. So I needed to come up with one. This power supply should be able to be placed in the same chassis with no interference or added heat. Just an option to toy with. Don't know yet which design sounds better than the current Gilmore design. I have built both so I will try them both out.
 I'm going all out with mine. As high quality value caps are available for mine. Using Black Gate and Cerafine. 2 of each.


----------



## rsaavedra

Quote:


  Originally Posted by *drubrew* 
_The last one took care of the popping in the Elma switch._

 

A good reason for me to try this alternative grounding.


----------



## drubrew

Here is the alternate Power Supply Layout.
 Drew


----------



## drubrew

Here are some pics:




 The rest Are big so here are the downloadlinks:
http://www.moon-audio.com/Images/Dynahi/Dynahi1.jpg 
http://www.moon-audio.com/Images/Dynahi/Dynahi2.jpg 
http://www.moon-audio.com/Images/Dynahi/Dynahi3.jpg 
http://www.moon-audio.com/Images/Dynahi/Dynahi4.jpg 
http://www.moon-audio.com/Images/Dynahi/Dynahi5.jpg 
http://www.moon-audio.com/Images/Dynahi/Dynahi6.jpg 
 Enjoy Drew


----------



## fyleow

Sorry for digging up an old thread guys but I was hoping I could get some help. I purchased the board during the first group buy but never got around to building this and I'm thinking about starting on it, I have a few questions though.

 1. I'm planning to use the Condor powersupplies but from some previous posts there seems to be a lot of humming problems, is there an alternative solution to this or are most just using separate enclosures?

 2. Will using different grade transistors have significant consequences (audio or otherwise). I plan on ordering from MCM but I've noticed a few posts saying they are clusless about grades.

 3. Has there been any luck with finding a premade heatsink or are most people hacking up larger ones?

 Lastly, I've read a little bit about the Dynalo and it seems to be less hassle than the Dynahi for similar performance? For me the biggest issue with the Dynahi is finding a heatsink and dealing with the relatively large enclosure.

 Thanks.


----------



## tkam

The Dynahi sounds soo much better than the dynalo, it's not even close.


----------



## drubrew

Why not use the Gilmore Power Supply or the one I show above? I may have an extra Gilmore Power Supply that is built and ready to go. It has the Heatsink also.
 Drew


----------



## fyleow

Quote:


  Originally Posted by *drubrew* 
_Why not use the Gilmore Power Supply or the one I show above? I may have an extra Gilmore Power Supply that is built and ready to go. It has the Heatsink also.
 Drew_

 

Drew,

 You have an extra one that's already done? I'd really appreciate it if you could PM me with more information. I'm not an expert when it comes to electronics (I'm just handy with a soldering iron) so I usually avoid trying to figure out circuits on my own. If you could help me out with this part I'd really appreciate it.

 Is the humming problem gone with your power supply even though you have it in the same chasis?

 Thanks,

 Fu


----------



## palchiu

Some questions about 2sj109/2sk389, Can them replace to 2sa1349/2sc3381?

 Thanks for your kindly inputs.


----------



## amb

Quote:


  Originally Posted by *palchiu* 
_Some questions about 2sj109/2sk389, Can them replace to 2sa1349/2sc3381_

 

If you cannot find 2SK389/2SJ109 in Taiwan, I think you'd be better off using hand-matched pairs of 2SK170/2SJ74 instead of using BJTs. The K170/J74 should be easy to find and cheap there.


----------



## palchiu

Thanks AMB!


----------



## Kenny12

when i plug the dynahi psu into my amp board with dc servo opamp put in i get +30V 0 1.6V and without opamp its +30 0 0.8V 

 basically everything is on the board, does anyone know what i've done wrong? or where i should start looking? 

 Should i eleminate all the parts for the dc servo?


----------



## dgardner

Quote:


  Originally Posted by *Kenny12* 
_when i plug the dynahi psu into my amp board with dc servo opamp put in i get +30V 0 1.6V and without opamp its +30 0 0.8V 

 basically everything is on the board, does anyone know what i've done wrong? or where i should start looking? 

 Should i eleminate all the parts for the dc servo?_

 

How about a little more detail, in pieces? 
 Do you know the PSU is working correctly at +30 and -30?
 Have you done any powerup testing on the amp board?
 How about some more explanation about what these measurement mean above. Where are you measuring?


----------



## Kenny12

the psu i'm using at the moment is just a straight linear psu with lots of regulation, the voltage tests are at the +30V 0 -30V inputs on the amp boards.

 On the psu board with a 12k dummy load, the output is 30 0 -30V 

 however when i connect it to the amp, it becomes 30V 0 0.8V. 

 heres a pic of the amp board


----------



## chris719

I too, had this problem. The problem I believe is one of my condor PSUs. I figured this out because when either board was hooked up, I got the 30-0-30 just fine.. then hook up the 2nd board and I would get 30-0-something low. Swapped the supplies and I ended up with something low-0-30. Thinking it had to do with the boards pulling too much current (ie, something fails) I put used my ammeter to measure the current each was using when hooked up alone and it was within spec (~400mA). So as a final attempt to try something before having to return the supply I put a switch in series with the -30V going to one board, after I plugged in the supply I would flip the switch about a second later, and this allowed me to get the full 30-0-30. I think for some reason there is some kind of protection being triggered on one of the regulators of the damaged PSU. Of course I could be wrong, but the amp seems to work fine so I am pretty sure it is the psu.. building the gilmore one to see for sure.


----------



## Kenny12

i get that exact same problem! 

 i guess i'm going to have to build the dynahi psu boards to be sure now


----------



## flecom

im finally getting aroudn to building my dynahi's... building a dynamite or whatever the balanced one is called lol..

 anyway i was wondering if they will run ok @ +24 / -24 instead of +28 / -28... at least for testing it out and such... before i build a proper psu... gonna use my dual 24v 15A regulated rackmount psu... yay government surplus


----------



## sbelyo

Just had to vent... This amp is labor intensive. I must have changed my heatsink arrangement 6 times. I finally ended up with sandwiching the transistors between two pieces of aluminum angle iron.


----------



## sbelyo

Oh darn... I forgot to order the input resistors. I know they're supposed to be 10K but I don't have any RN60D series. I use a 50K pot in a passive switchbox not installed in the amp .

 I do have:
 1K
 2K
 4.7K
 100K

 or I have a RN55 10K

 Will any of these work?


----------



## sft

100K


----------



## amb

100KΩ is the best of the bunch that you have. Usually you should use a value that is at least 10x the value of the volume pot, and in your case it should be >500KΩ. I also used a 50KΩ volume pot in my build, and I used a 1MΩ resistor.


----------



## sbelyo

Thanks guys.. I forgot the reccomended value. I'll use the 100K


----------



## sbelyo

I got one board mounted and working. Without pots or the opamp installed it's at 28mV offset. I popped in a TL81 opamp in and just to see if it would correct that much and it jumped up to 70mV. I tried an opa134 and it started at 26 mV and went down to 18mV but no further.

 So I guess I'll have to use the pots to dial it in to less than 10mV. When I put in the pots, should I preset both to 10K?


----------



## rsaavedra

Quote:


  Originally Posted by *sbelyo* 
_I got one board mounted and working. Without pots or the opamp installed it's at 28mV offset. I popped in a TL81 opamp in and just to see if it would correct that much and it jumped up to 70mV. I tried an opa134 and it started at 26 mV and went down to 18mV but no further.

 So I guess I'll have to use the pots to dial it in to less than 10mV. When I put in the pots, should I preset both to 10K?_

 

Check posts 261 to 263 in this thread (page 14). After I had some problems with the 10K pots and DC offset adjustment, Kevin Gilmore wrote some suggestions about how to determine which pot to use and on which side of the board to place it. A 10K pot might not be enough btw.


----------



## sbelyo

Thanks...

 That's just what I was looking for. At least if I need different pots my local electronics place has them.


----------



## amb

sbelyo, those trimpots accomplish two things: offset trimming and overall amp biasing. If you only have one trimpot installed then you could only do the offset adjustment. Having both, you can then also adjust the amp bias to achieve the designed operating points.

 See this post from me on headwize on how to properly adjust the two trimpots. I had posted the same info in this forum but don't remember which thread it was in.


----------



## sbelyo

thanks amb.... you guys weren't kidding about the heat it throws. It's like 10X the dynalo


----------



## vpivinylspinner

I thought you guys might be the best to ask on this issue. I have a Dynahi SA that has a vibration problem. There is an audible buzz on the amp anytime it is on. If you damp the top of the amp with your hand the noise lessens but it does not go away. I have opened it up and tried to determine what is vibrating but I can't decide. Is this a common issue and if so is there a particular area to look at or a fix that I might try.

 Thanks,

 Jeff


----------



## rsaavedra

Quote:


  Originally Posted by *vpivinylspinner* 
_There is an audible buzz on the amp anytime it is on. If you damp the top of the amp with your hand the noise lessens but it does not go away. I have opened it up and tried to determine what is vibrating but I can't decide._

 

I would associate any buzz/vibration in an amp with the transformer and power supply in it, probably it's a transformer hum. By the way, buzz is coming through the signal, or are you hearing it in the open with your ears near the amp?


----------



## vpivinylspinner

No sound through the headphones, the sound is actually quite good. The vibration is a mechanical one that resonates through the flimsy sheet metal of the case. The transformer is bolted down so tightly that the bottom of the case is bent up by the bolt so I don't believe that to be the problem. This buzz can be heard from the next room rather easily as it is that noisy.


----------



## Pars

Quote:


  Originally Posted by *vpivinylspinner* 
_No sound through the headphones, the sound is actually quite good. The vibration is a mechanical one that resonates through the flimsy sheet metal of the case. The transformer is bolted down so tightly that the bottom of the case is bent up by the bolt so I don't believe that to be the problem. This buzz can be heard from the next room rather easily as it is that noisy._

 

Torroid transformer, I assume? You could try some Dynamat or rubber between the transformer and the case. One other thing I would check: does it do it in another location in your house (just take it somewhere else and plug it in). Also, if you could try it somewhere else altogether (i.e., not in your house). DC on the mains can cause transformer noise (IIRC).

 Chris


----------



## sbelyo

Fixed my problems pretty much. 260mA draw from the power supply. with no pots the offset is around 10 - 12 mv and the servo immediately drops it to 0 in 2 minutes or so. each output transistor is drawing 60 ma or 0.602 V

 I know it should be 0.7 but I put the pots in place and I could only get the current draw or offset to normal but not both.


----------



## sbelyo

How should the pots be oriented?

 I've seen them with the pot on the left having the adjustment screw towards the top and the right with the screw on the bottom http://www6.head-fi.org/forums/showp...&postcount=503

 Or like this with both adjustment screws towards the top http://www6.head-fi.org/forums/showp...2&postcount=54

 Also, should I set them both to 10K (the max)?


----------



## amb

Quote:


  Originally Posted by *sbelyo* 
_How should the pots be oriented?_

 

I thought the board silkscreen is marked with the orientation... It actually doesn't matter much, since two of the pins are connected together, reversing the orientation simply reverses the "sense" of the adjustment screw rotation.

  Quote:


 Also, should I set them both to 10K (the max)? 
 

I suggest setting both to the middle of their travel to start with.


----------



## sbelyo

Quote:


  Originally Posted by *amb* 
_I thought the board silkscreen is marked with the orientation... It actually doesn't matter much, since two of the pins are connected together, reversing the orientation simply reverses the "sense" of the adjustment screw rotation._

 

The board is marked I just got confused because some people had them switched around.

 I got it working. 0.73V across the 20 Ohm resistors. Between 10 and 15 mV upon warm startup with servo installed. It quickly settles to 0

 I've finished the one board and gave it a listen. Very nice, it sounds like it's worth all the work.

 Thanks


----------



## vpivinylspinner

Quote:


  Originally Posted by *vpivinylspinner* 
_No sound through the headphones, the sound is actually quite good. The vibration is a mechanical one that resonates through the flimsy sheet metal of the case. The transformer is bolted down so tightly that the bottom of the case is bent up by the bolt so I don't believe that to be the problem. This buzz can be heard from the next room rather easily as it is that noisy._

 

Well apparently the buzzing was a sign of things to come as now the amp has periodic loud static followed by a large dropout of the sound. Anybody in NYC willing to check out the amp for a fee and try to get it operating properly again so the money I laid down for the amp two weeks ago is not a complete waste?


----------



## sbelyo

Well, It's up and running. Sounds friggin' awesome. I'm guessing this is what full range sounds like. I've still got some case work to do, but all in all this amp was more labor intensive than anything else.

 My question today is can I set the bias to 0.7 Volts and still be in the correct operation range? I had it set to 0.74 on cold startup, but after using it for 1.5 Hours it crept up to 0.79 and the heatsinks were getting hot to the touch.


----------



## n_maher

Quote:


  Originally Posted by *sbelyo* 
_Well, It's up and running. Sounds friggin' awesome._

 

Congrats Steve! I wish I had the time/energy/desire/stomach to tackle this amp. I just don't see it in my future and have avoided listening to one at every meet I've been to 
	

	
	
		
		

		
			





.

 Nate


----------



## sbelyo

Quote:


  Originally Posted by *n_maher* 
_Congrats Steve! I wish I had the time/energy/desire/stomach to tackle this amp. I just don't see it in my future and have avoided listening to one at every meet I've been to 
	

	
	
		
		

		
		
	


	




.

 Nate_

 

It definitely is a ton of work, there is a reason why it costs $1800 when professionaly built. Most of the work was in the planning stages like case size, heatsinking, and assembling the output transistors to the heatsinks. I'll tell you one thing I hope I never go balanced because I aint building another one anytime soon.

 But it was worth it, this is the first project that I can't find any faults with the outcome. The only thing I can tell you Nate old buddy is keep not listening


----------



## rsaavedra

Congratulations Sbelyo, enjoy!!!


----------



## sbelyo

Thanks... I will


----------



## amb

Quote:


  Originally Posted by *sbelyo* 
_My question today is can I set the bias to 0.7 Volts and still be in the correct operation range? I had it set to 0.74 on cold startup, but after using it for 1.5 Hours it crept up to 0.79 and the heatsinks were getting hot to the touch._

 

Yeah, that's fine. The positive tempco of the output BJTs will cause the current to increase when they heat up, so you should adjust it for the target quiescent current when it's warmed up.


----------



## sbelyo

Great I'm gonna bump it down to 0.68 or so and then see where it's at after 1-2 hours


----------



## Kruemelix

Hello,

 I am just gathering all the transistors for the amp board, as I saw that reichelt.de sells the SA1349 for 0,82€. Nevertheless, a SC3381 costs 2,55€. Since a SA1349 costs even at borbelyaudio and bdent 3-5$, I thought that it would be an fake of the original Toshiba trannies. To buy or not to buy: that's the question....

 Thomas


----------



## Pars

Hard to say. MCM has the 2SA1349 for $1.69 and the 2SC3381 for $0.87. BDent has these for $4.77 / $6.43. MCM is typically cheaper on alot of these, and they are genuine to the best of my knowledge. But it is odd that the price varies so much and one place has one cheaper than the other while another has the other cheaper.


----------



## steinchen

I got mine from Reichelt and they are fine, no fake
 Reichelt has a very competitive pricing


----------



## werewuff

This is related to the dynahi PSU,. I was wondering if someone could tell me if I could replace the REF02BP (digikey: REF02BP-ND) from the BOM with a REF02AP instead (digikey: 296-12732-5-ND) - reason being digikey doesn't have the BP one in stock at the moment. At a glance they seem quite similar....

 Thanks


----------



## grasshpr

Quote:


  Originally Posted by *werewuff* 
_This is related to the dynahi PSU,. I was wondering if someone could tell me if I could replace the REF02BP (digikey: REF02BP-ND) from the BOM with a REF02AP instead (digikey: 296-12732-5-ND) - reason being digikey doesn't have the BP one in stock at the moment. At a glance they seem quite similar....

 Thanks _

 

At first glance at the datasheet, looks like the AP version has a higher ppm compared with the BP version. Also the drift is slightly higher with the AP version. I doubt it will contribute significantly to your PSU.


----------



## werewuff

just got another question that surfaced. I was wondering how critical are the seven 5K resistors on the dynahi audio board (BOM from Dan Gardner's website). I'm getting my RN60 resistors from THLAudio and they don't have the 5K ones in stock, but they do have the 5.1K ones. Is 5.1K close enough or will it throw things off?

 thanks for your patience!

 (Grasshpr, thanks for your reply on the previous post)


----------



## drubrew

That is fine. It is not a critical spot.


----------



## grasshpr

I agree with Drubrew. Not a critical issue. However, is it possible to get 4.99k resistors instead? That should be closer to 5k.


----------



## werewuff

Quote:


  Originally Posted by *grasshpr* 
_I agree with Drubrew. Not a critical issue. However, is it possible to get 4.99k resistors instead? That should be closer to 5k._

 

Unfortunately they (THLAudio) don't have either in stock. 
	

	
	
		
		

		
			





 Closest one they have is the 5.1K and I was trying to avoid ordering from mouser as shipping is quite a fair bit more. 

 I guess the question now would be, as it is sort of "non-critical" anyway is it better to:

 1. use generic 5K

 or

 2. an RN60 5.1K

 ?

 thanks


----------



## Kruemelix

I just finished all the PSU boards for my Dynamight and plgged them in...
 Getting +29,9V between +30V and ground and around 8V between -30V and ground is not really satisfying. Furthermore, the lower right capacitor (near the output of the PSU) becomes way too hot...
 I just tested the LM338 and OPA541 and they are all insulated from each other. They also do not run very hot. Any proposals where failures can be?

 Thomas

 P.S. pictures coming soon on request


----------



## DigiPete

Quote:


  Originally Posted by *Kruemelix* 
_I just finished all the PSU boards for my Dynamight and plgged them in...
 Getting +29,9V between +30V and ground and around 8V between -30V and ground is not really satisfying. Furthermore, the lower right capacitor (near the output of the PSU) becomes way too hot...
 I just tested the LM338 and OPA541 and they are all insulated from each other. They also do not run very hot. Any proposals where failures can be?

 Thomas

 P.S. pictures coming soon on request_

 

Check for reversed caps/diodes or a cold solder joint


----------



## sbelyo

something's not right...

 Check all your resistor values as well. Could be a cold solder joint on a resistor.

 After I stuff and solder a board, I clean the board with alcohol and reflow all the joints until they're shiny. If I suspect a joint may not be up to snuff, I check it with an eye loop.

 I know that sounds a bit anal, but when building a dynamight you've already dumped several hundred into the project before you start to solder.


----------



## DaKi][er

OK, I’ve been slowly working on a dynahi, after being given all the parts for 2 and a half of them and completed one that had a busted psu from kenny12 and all I had to do was to get one working for a friend of his which was no problems after getting some more opa541's for the psu and a little more care in the construction and testing than kenney12.

 So with all the other parts left I got enough to make a balanced dynahi and have decided to go nuts on it and do it all perfect from the start.

 I got a psu board all soldered up and outputting a nice +/-30.000V after hand selecting resistors to get a perfect output.

 Now onto the amp, I’ve been measuring the gain of the transistors but I’m a little unsure on what the ideal transistor values for what spot.
 So here is a list of what I’ve got and I’m after some recommendations on what transistors to use where.

*2sa1145*
 164
 164.1
 165.1
 166.6
 168.4
 169.3
 169.4
 169.45
 171.8
 172.3
 172.5
 173.4
 173.7
 174
 174.5
 175.85
 177
 191

*2sc2705*
 177.1
 178.12
 178.3
 180.2
 180.3
 180.6
 180.7
 181.35
 182.55
 182.8
 183.5
 183.55
 183.7
 185.45
 198.95
 202.6
 203.7
 207.8

*2sc3421*
 142.5
 145.3
 146.2
 148.4
 148.9
 149.3
 150
 150.3
 150.5
 154.3
 157.5
 158
 158.7
 159.3
 161.5
 161.9
 162.3
 163
 164
 166.9
 167.8
 168.6
 169
 169.7
 370 dead?

*2sa1358*
 183.3
 191.1
 193.1
 194.3
 195.2
 196
 196
 196.65
 197
 197.4
 198.1
 198.75
 198.8
 199.65
 200.1
 200.5
 200.5
 201.1
 201.8
 202
 202.75
 202.9
 204.2
 205.1
 223.2


----------



## Kruemelix

I tried another PSU board and exactly the same thing happens. Around +30V between +30/GND and +10V between -30/GND. Seems as I soldered something wrong. Can I post some HiRes pics of the PSU board? Perhaps someone here can see the failure as I am still thinking having done nothing wrong...

 Thomas


----------



## Kruemelix

another thing: the right OPA541 is getting way too hot on both boards


----------



## DaKi][er

Quote:


  Originally Posted by *Kruemelix* 
_another thing: the right OPA541 is getting way too hot on both boards_

 

Most certainly sounds like you killed the -ve output opamp, check that none of the capacitors near it haven’t blown, the tantalums really like to go short circuit when they die.

 Also the way it works is the -ve opamp takes its input signal voltage from the +ve opamp and inverts it for its output, so trace that back as well and check the 2 10K resistors as if there is something wrong there and the input is open circuit it will kill it too

 The psu circuit is very temperamental, anything wrong at all on it will nearly always end in catastrophic failure, check everything twice over


----------



## DigiPete

Quote:


  Originally Posted by *Kruemelix* 
_another thing: the right OPA541 is getting way too hot on both boards_

 

Hmmm, check your LM338 inputs/outputs to make sure they are correct.

 Try posting also on Headwize in the Dynahi PSU DIY section.


----------



## DaKi][er

BUMP!

  Quote:


  Originally Posted by *DaKi][er* 
_OK, I’ve been slowly working on a dynahi, after being given all the parts for 2 and a half of them and completed one that had a busted psu from kenny12 and all I had to do was to get one working for a friend of his which was no problems after getting some more opa541's for the psu and a little more care in the construction and testing than kenney12.

 So with all the other parts left I got enough to make a balanced dynahi and have decided to go nuts on it and do it all perfect from the start.

 I got a psu board all soldered up and outputting a nice +/-30.000V after hand selecting resistors to get a perfect output.

 Now onto the amp, I’ve been measuring the gain of the transistors but I’m a little unsure on what the ideal transistor values for what spot.
 So here is a list of what I’ve got and I’m after some recommendations on what transistors to use where.

*2sa1145*
 *snip*
*2sc2705*
 *snip*
*2sc3421*
 *snip*
*2sa1358*
 *snip*
 223.2_


----------



## dip16amp

2sa1145 164, 164.1, 165.1
 2sc2705 178.12, 178.3, 180.2
 2sc3421 149.3, 150, 150.3, 150.5
 2sa1358 196, 196, 196.65, 197

 2sa1145 169.3, 169.4, 169.45
 2sc2705 180.3, 180.6, 180.7
 2sc3421 158, 158.7, 159.3, 161.5
 2sa1358 197.4, 198.1, 198.75, 198.8

 2sa1145 172.3, 172.5, 173.4
 2sc2705 181.35, 182.55, 182.8
 2sc3421 161.9, 162.3, 163, 164
 2sa1358 199.65, 200.1, 200.5, 200.5

 2sa1145 173.7, 174, 174.5
 2sc2705 183.5, 183.55, 183.7
 2sc3421 166.9, 167.8, 168.6, 169
 2sa1358 201.1, 201.8, 202, 202.75


----------



## DaKi][er

Makes sense, Thanks for that


----------



## rsaavedra

I'm rebuilding an enclosure for my Dynahi, in fact two separate enclosures, one for the power supply, another for the amp.

 Using a 7ft balanced shielded microphone cable to bring the electricity (+, -, and ground) from the power supply box to the amp boards box.

 The + and - wires in this cable are 22 AWG, ground will travel through the shield mesh. Does this sound like a good choice of a cable to bring the DC power (+/-30v, 2A) to the dynahi boards?


----------



## Pars

I would probably opt for either larger gauge or more runs. Also, I would not use any type of audio connector for this that a user could mistake for an input/output. Something like Amp 97 series, etc. circular connectors would be good. Amb has done this and recommended a connector for it.


----------



## rsaavedra

Quote:


  Originally Posted by *Pars* /img/forum/go_quote.gif 
_I would probably opt for either larger gauge or more runs. Also, I would not use any type of audio connector for this that a user could mistake for an input/output. Something like Amp 97 series, etc. circular connectors would be good. Amb has done this and recommended a connector for it._

 

The balanced connectors wouldn't be a problem for me, this would be the only balanced cable I have at home, at least so far. Yet I certainly see your point though, a balanced cable running DC power would be very destructive if plugged into the connectors of a legitimate balanced component. Quite risky. I will have to find another use for this balanced cable 
	

	
	
		
		

		
		
	


	




 Thanks Pars!


----------



## DigiPete

Quote:


  Originally Posted by *rsaavedra* /img/forum/go_quote.gif 
_The balanced connectors wouldn't be a problem for me, this would be the only balanced cable I have at home, at least so far. Yet I certainly see your point though, a balanced cable running DC power would be very destructive if plugged into the connectors of a legitimate balanced component. Quite risky. I will have to find another use for this balanced cable 
	

	
	
		
		

		
		
	


	




 Thanks Pars!_

 

I'm using 12g power cable wire from home depot and 20-amp plugs/sockets (sideways pins vs. the standard vertical pins on 120v household plugs).


----------



## flecom

i would look at CPC connectors... or maybe SpeakON connectors would be good since they are designed with large conductors in mind, and they are locking too... other usual suspects could be used also, such as DIN connectors... im also a fan of radio mic connectors... switchcraft has the three pin version... but i have seen them start at 2 pins and work their way up to i think 8 pins dont remember

 ex

http://www.switchcraft.com/products/connectors-53a.html


----------



## n_maher

Quote:


  Originally Posted by *flecom* /img/forum/go_quote.gif 
_i would look at CPC connectors... or maybe SpeakON connectors would be good since they are designed with large conductors in mind, and they are locking too..._

 

I would go one step further and use the Neutrik PowerCon connectors. They have three dedicated terminals which would be useful for this application and they are a "one-way" plug meaning that you can't get it wrong. You could use the Speakon connectors but you would have to find the 4-channel version as i think the one's most commonly found are two conductor, or at least the ones that I used for. I also like to make sure that none of the connectors used on my amps duplicated on that amp. So for the Dynahi I'd use a standard IEC receptacle for the AC input and then use a Powercon setup for the umbilical between the PS and Amp.

 rsaavedra, here's the back panel of my PPA which used a Powercon for the AC connector and Speakon hardware for the umbilical cord.


----------



## j4cbo

Cases are expensive! 
	

	
	
		
		

		
		
	


	




 I'm looking for a good enclosure for my Dynahi (potentially to be upgraded to a Dynamite in the future). The HiFi2000 "Pesante Dissipante" and DIY Enclosures 1712HS both look really nice, but they're insanely expesnive - $150-$200 after shipping. I could stretch that much, but I'd have to put everything in one case rather than two, and apparently that's much preferable from a noise and interference point of view.

 Are there any nice-looking, not-overly-expensive, heatsinkable cases out there?


----------



## Pars

look here


----------



## rsaavedra

Speaking of cases, I have a problem finding any decent metallic cases here in Venezuela. The only available ones have inapropriate dimensions, and are extremely horrible anyway 
	

	
	
		
		

		
			





. Not sure if I will be able to find aluminum panels to build the enclosure myself. Also wondering if wooden enclosures would be too bad an idea. Some amps don't have metallic enclosures after all, for example the Audio Valve RKV MK II. Even the Berning Microzotl has some glass walls, not a full metal jacket so to speak. In my case it's a Dynahi, I know those heatsinks heat up a lot and will have to breathe, but assuming sufficient vents how about a wooden enclosure that I could build myself? I wonder it wouldn't help against EMI though. Any suggestions/recommendations?


----------



## rsaavedra

Today I found some nice connectors and a nice cable for the umbilical cord between my two enclosures:







 Interestingly, I did find the speakon connectors in one local store, but they only had the cable connectors, not the chassis mountable ones, so couldn't use them. I liked these ones too anyway.

 Despite the overall thickness of the cable, it is really very flexible. The wires in it are 16 awg btw. This will be much better than the 22 awg wires in the microphone cable I have.


----------



## luvdunhill

I'm not sure if this is the best place to ask this, but I wanted to see if it would be possible to use PRP resistors on a Dynahi board. As you might know, there are a lot of holes in their 0.5 W line. So, I'm trying to understand if it's possible to substitute. Here's my analysis:

 schematic value 500R used at the emitter of 2sa1145. sub to 510R. seems reasonable, this will decrease the current a tad.

 schematic value 20R. strange, as I found a schematic that uses 10R, but the 20R is mentioned in djgardner's BOM. anyways, my choices are 18R and 22R, 18R seems fine here.

 schematic value 300R. used at collector of 2sc2705/2sa1145. Closest value is 270R or 330R. I'm not so sure about this one.

 schematic value 30K. use at base of 2sa1145... choices are 27K or 33K...

 schematic value 5K, used at collector and base of 2sc3381/2sa1349 and into OP27. Closest value is 5K1... seems reasonable to me, but again I'd like your opinions.

 If this isn't feasible, then I'll just use vishay-dale resistors, but I'd like to give it a try. I know some of these values are available in Holco, but I'd like to stay with the pretty red ones 
	

	
	
		
		

		
		
	


	




 Thanks guys!


----------



## DigiPete

If you don't get help here, go to the DIY area of headwize. There is a Dynahi amp build thread there.

  Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_I'm not sure if this is the best place to ask this, but I wanted to see if it would be possible to use PRP resistors on a Dynahi board. 
 Thanks guys!_


----------



## Pars

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_I'm not sure if this is the best place to ask this, but I wanted to see if it would be possible to use PRP resistors on a Dynahi board. As you might know, there are a lot of holes in their 0.5 W line. So, I'm trying to understand if it's possible to substitute. Here's my analysis:

 schematic value 500R used at the emitter of 2sa1145. sub to 510R. seems reasonable, this will decrease the current a tad._

 

should be fine

  Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_schematic value 20R. strange, as I found a schematic that uses 10R, but the 20R is mentioned in djgardner's BOM. anyways, my choices are 18R and 22R, 18R seems fine here._

 

the actual resistance is 10 ohms... done by paralleling (2) 20 ohm resistors for better power handling.

  Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_schematic value 300R. used at collector of 2sc2705/2sa1145. Closest value is 270R or 330R. I'm not so sure about this one._

 

not sure on this one... I'd probably try both

  Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_schematic value 30K. use at base of 2sa1145... choices are 27K or 33K..._

 

I would think that would be OK
  Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_schematic value 5K, used at collector and base of 2sc3381/2sa1349 and into OP27. Closest value is 5K1... seems reasonable to me, but again I'd like your opinions._

 

that would be fine

  Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_If this isn't feasible, then I'll just use vishay-dale resistors, but I'd like to give it a try. I know some of these values are available in Holco, but I'd like to stay with the pretty red ones 
	

	
	
		
		

		
		
	


	




 Thanks guys!_

 

I'd use Roederstein MK3s if I could get them... PRPs are nice also... my dynalo uses a mix of these since the common values (10K, 1K, etc.) are unobtainable in Roederstein.


----------



## luvdunhill

Quote:


  Originally Posted by *Pars* /img/forum/go_quote.gif 
_
 not sure on this one... I'd probably try both_

 

heh, and what would be my litmus here?


----------



## Kruemelix

Hello,

 just wanted to know whether the planned internal wiring of my Dynamight will be correct. Hope everyone understands everything. The input ground of all amplifier boards and the ground of the balanced input jacks are connected due the internal structure of the attenuator.

 Thomas





 P.S. I still don't know how important a good ground wiring is. By using a seperate PSU case, is it possible to connect the ground of the two power supplies and the ground wire of the power supply for the attenuator already in the PSU case together and lead only one ground cable out? Or shall I realize a uncompromising star wiring (don't know the exact english word) which will result in many ground wires from the PSU to the Amp case where the connection point will be.


----------



## Kruemelix

nobody who could help? A "yes" or "no" will be enough


----------



## amb

Run the unbalanced headphone jack ground return wires separately from the amp board grounds back to the PSU. As far as your attenuator goes, you do not mention what it is, and whether the "ground" on it going back to the PSU is shared with signal ground. If you put the PSU in a separate case than the amp, it could really complicate matters if the grounds are shared.

 I suggest you read my post in the dynahi thread at headwize about grounding concerns and why separate amp and PSU cases are a good thing, but in my situation the volume control is an Alps RK40 pot, so there isn't an issue with having to run power supply lines to it.


----------



## Kruemelix

thanks amb, I found your artile at headwize and read it. The problem I had was that I didn't look neither at a schematic nor at a PCB of the amp. Now that I had a look at the schematic, you better replace "Out 2" in my picture by the GND pin at the amp board. So our two proposals are almost the same, except the fact that you are realising a better "star wiring" (still don't know the exact name), right?

 But another major problem occured: I thought the amp boards were already built completely when I saw the 2sk389 and 2sj109 missing. After a little bit of searching I realized that they are almost everywhere out of stock or only avaliable at insane prices (15$ a piece). Is it possible to use 2sk170 and 2sj74 instead of them? Of course I will have to match them (even if I don't know exactly ho to do so with JFETs).

 Furthermore, with the qouted wiring above, I can use the balanced output only with balanced inputs completely, right? 

 Thomas

 P.S. I just realized that the grounds aren't tied together (attenuator is a V-03 from diyclub.biz


----------



## amb

Quote:


  Originally Posted by *Kruemelix* /img/forum/go_quote.gif 
_thanks amb, I found your artile at headwize and read it. The problem I had was that I didn't look neither at a schematic nor at a PCB of the amp. Now that I had a look at the schematic, you better replace "Out 2" in my picture by the GND pin at the amp board. So our two proposals are almost the same, except the fact that you are realising a better "star wiring" (still don't know the exact name), right?_

 

Yes, the idea about running separate wires for the unbalanced headphone jacks' ground return back to the PSU ground is so that the small signal ground reference from the amp boards won't be modulated by the higher output return currents.

  Quote:


 Is it possible to use 2sk170 and 2sj74 instead of them? Of course I will have to match them (even if I don't know exactly ho to do so with JFETs). 
 

2SK389 and 2SJ109 is obsolete (Toshiba has stopped making them quite some time ago), and the shrinking supply of unsold parts are being horded at high prices.

 You can use matched 2SK170 and 2SJ74 in place of 2SK389 and 2SJ109. They are equivalent devices (except for the fact that the former are singles and the latter are duals). See the "device matching" page of the β22 website about how to match them. You will need a fairly large number of them to achieve a good match, though, which probably makes even less sense than buying the 2SK289/2SJ109s at their high prices (if you could find them).

  Quote:


 Furthermore, with the qouted wiring above, I can use the balanced output only with balanced inputs completely, right? 
 

If you use an unbalanced input (feeding only the + and GND input pins on the XLR), and you also ground the - input, then you can still use the balanced output jack. The signal won't be truly differential, but it will work.

  Quote:


 P.S. I just realized that the grounds aren't tied together (attenuator is a V-03 from diyclub.biz 
 

I suggest running a separate ground wire back to the PSU for this board since it contains relays and digital circuitry. I don't think there is a need for the ground on this board to be connected to the amp ground at all. They could remain completely independent.


----------



## Kruemelix

After around 12 hours of working (only enclosure), I finally finished my Dynamight. Checked everything twice, plugged in and runs stable for around 15 minutes now. Thanks to Pars and Amb who helped me a lot during the building process.

 Thomas

 P.S. first DIY project for me 

 EDIT: now around 1 o' clock in the morning....


----------



## Kruemelix

ok, first problems appeared:

 when I plugged in a headphone, I heard nothing. After some measurements, I found out that the controller board of the attenuator (V-03 from DIYClub) seems to be damaged - the input resistance never goes below 100k. Might be the microcontroller.

 Another problem occured: Without any input signal/load, the voltage drop over the 20 Ohm output resistors is around 1V - makes 100mA per transistor. Furthermore, the heatsink is getting damn hot after some minutes. Thus, I never have plugged in my Dinamight a longer time. How can you adjust the output current?


----------



## Pars

I would short the input of the amplifier to ground when setting up or verifying its operating points. The 20 ohm resistors are in parallel (2 in || for 10 ohms), so that would be your current calculation for the output devices. There is another build thread on Headwize as well if you aren't aware of it. I still haven't


----------



## Kruemelix

ok, after a month I got back again on the Dynamight, adjusting the output current of each of the output transistors to 75mA. Nevertheless, the heatsinks (HS-TWS) are still getting very hot - you can barely touch them with bare hands. Is this normal? Are the heatsinks undersized?

 Thanks,

 Thomas


----------



## amb

The HS-TWS is a bit undersized for the amount of heat the dynahi puts out. But as long as your case has good ventilation it should be ok.


----------



## steinchen

What's the heatsinks K/W rating ? Did you happen to measure the heatsinks temperature ? You may consider to reduce the bias a bit, e.g. 70mA per tranny.


----------



## Kruemelix

@steinchen

 don't think that will help much. While adjusting the trimpots on the boards, some of the boards ran at only 65mA - and got also hot. I am just thinking about mounting two 40x40mm fans with reduced speed on each of the heatsinks. The small additional noise won't bother me much and it should work fine...
 But good to know that the heatsinks are too small


----------



## digger945

So how is it goin with everyone?
 Just wondering.


----------



## Energy jobs

hi,
 what does the sound originate? No matter how good the rest of your stuff is, if you're running off a 128CBR Mp3 through a terrible motherboard RealTek AC97 DAC, you're going to get terrible sound output quality. At the least, you owe it to your ears to get the Chaintech AV710 PCI sound card. Using "High Quality Mode" outputs the sound through the rear DACs, which have a SNR of 106dB and a very low THD figure. Let me be clear, here: a lovely source will RUIN your listening experience. You don't have to go absurdly all-out, but pay attention to the figures and get something that isn't going to suck the life out of the rest of your setup


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## Pars

What? Nice 1st post in a completely unrelated thread


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## digger945

Odd post.
 Well I finally have all the parts to build mine
	

	
	
		
		

		
		
	


	



 Can't wait, as I have probably read every post in this thread alone 3 times already.


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## Kruemelix

finally everything works well. I mounted two 60mm fans on each heatsink (with reduced speed). As a consequence, they never get above hand-hot. Nevertheless, another problem occured: When plugging in my AT W5000 I always hear a small background hum that doesn't increase with bigger attenuation. I have to admit that this only occurs with the ultrasensitive W5000 and only with the Dynamight. When being plugged into the headphone jack of my preamp I hear nothing.

 Any explanation?


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## digger945

You have a pic?
 You think maybe having two fans close to the amp may have something to do with the hum?


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## FallenAngel

So I got my 2-channel Dynahi build and playing beautifully (though running pretty damn hot - 8 hours of straight and with the heatsinks bolted to the bottom of the steel chassis, the bottom plate gets too hot to comfortably hold).

 Now I'm planning for a DynaMight and just ordered a set of heatsinks off eBay. I had these cut to 2.5" lengths (well, height - the length is 5 3/8").

 My question is about the L brackets. I got some aluminum brackets from the local hardware store (couldn't find a good choice online) and I'm wandering on the thickness requirements for them. They will be actually taking all the heat from the transistors and spreading it to the heatsinks and I'm worried that they'll just get too hot themselves before dispersing the heat to the heatsinks. The thickness of the brackets is 1/8" I think and it feels like very lightweight aluminum. Would (or could) this be a potential problem. I don't really want to spend a lot of time with them if they will ultimately hold back the heat dissipation.

 Is there a minimum (or optimal) thickness for the brackets? Good place to get them?

 Thanks in advance.


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## digger945

I cut mine to the exact width of the pcb. I wouldn't go any longer unless I knew for sure I would have room in the case. 
 I don't think you will have a problem with this method, the heat travels pretty fast in the L bracket. I used thermal compound between the bracket and HS and lapped the two on a piece of plate glass with 440 grit sandpaper.
 I read Kevin say he had seen this done literally hundreds of times. Can't remember where but I'll look for the link.





 Aluminum angle 1/8" thick and 1"X1", I cut them on a Makita power miter saw with a carbide blade. I cut really slow so the edges would be smooth. I used Thermasil III stick on pads and trimmed them with scissors after sticking them to the outputs. Bolted everything together first then soldered the legs in place.


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## Pars

Very nice job on the brackets digger! You wouldn't want to make another pair would you? PM if so. When you say you lapped the bracket and the heatsink with 400 grit, did you place the piece to be lapped on top of the sandpaper on top of the glass? I assume wet?


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## digger945

The glass was a door on a stereo cabinet, very thick. I have a roll of adhesive backed sandpaper disks and just stuck them to the glass, sometimes two side by side(never overlapping) and rubbed the parts(bracket or HS) on the glass dry. To test the fit I put a drop of oil on the bracket and stuck it to the HS and if it was almost impossible to get the two apart I was satisfied it would work great with just thermal compound.
 All 4 brackets(balanced amp) had to be numbered as the holes were peculiar to each position. I actually mounted the brackets to the HS's with rubber washers to allow the bracket to expand and contract with heat but using the Conrad HS's everything stays pretty cool. Only the top of the actual outputs get kinda hotish.


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## FallenAngel

Sorry, I meant "optimal/minimal THICKNESS" to the brackets, not "width". Thanks


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## Pars

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_The glass was a door on a stereo cabinet, very thick. I have a roll of adhesive backed sandpaper disks and just stuck them to the glass, sometimes two side by side(never overlapping) and rubbed the parts(bracket or HS) on the glass dry. To test the fit I put a drop of oil on the bracket and stuck it to the HS and if it was almost impossible to get the two apart I was satisfied it would work great with just thermal compound.
 All 4 brackets(balanced amp) had to be numbered as the holes were peculiar to each position. I actually mounted the brackets to the HS's with rubber washers to allow the bracket to expand and contract with heat but using the Conrad HS's everything stays pretty cool. Only the top of the actual outputs get kinda hotish._

 

Thanks. Did you buy the L bracket material online or Home Depot, etc.? Same for the carbide blade? I have a radial arm saw, but cutting the brackets would be the biggest problem for me; I have a drillpress, etc. so drilling them and the rest of the work would not be a problem.

 As for the mounting hardware, I assume you used probably 4-40 stuff for the output transistors and for mounting the boards to the L bracket? As for mounting the L bracket to the heatsink, I would guess 8-32 from your pics?


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## MisterX

You don't want to go much thicker then an 1/8" because you are going to have a very hard time mounting the transistors if you do. 
	

	
	
		
		

		
			





 What I did is bought a 6' piece of 2" x 2" stock from Ebay and had the seller cut it into lengths (which he did for free) and then cut the PCB "mounting side" to size with an abrasive disk in my dremel, laid a circuit board over the stock, marked the hole locations, zapped it with the automagic center punch then drilled the holes. 
 Took about 10 minutes to make each bracket. 
 (I made 3 sets of heatsink mounting brackets for less then $10)

 Unfortunately I cannot locate that ebay seller so maybe try online metals instead? 
Order Aluminum 6061 Angle in Small Quantities at OnlineMetals.com


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## bhjazz

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_To test the fit I put a drop of oil on the bracket and stuck it to the HS and if it was almost impossible to get the two apart I was satisfied it would work great with just thermal compound._

 

Very similar to what I've done with CPUs and heatsinks. Better heat transfer = more overclocking! 
	

	
	
		
		

		
		
	


	




 Nice idea to do it here, digger!


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## digger945

Quote:


  Originally Posted by *Pars* /img/forum/go_quote.gif 
_Thanks. Did you buy the L bracket material online or Home Depot, etc.? Same for the carbide blade? I have a radial arm saw, but cutting the brackets would be the biggest problem for me; I have a drillpress, etc. so drilling them and the rest of the work would not be a problem._

 

Got the aluminum from Ace Hardware, which was a little more expensive than just about any where else, but Ace has a lot of the small fasteners so I got most everything while I was there. The saw is a 10" Makita compound miter(not sliding) from the pawn shop and the blade is a Freud F-40 I think made for wood.


  Quote:


 As for the mounting hardware, I assume you used probably 4-40 stuff for the output transistors and for mounting the boards to the L bracket? As for mounting the L bracket to the heatsink, I would guess 8-32 from your pics? 
 

 Yes the transistor mounting is 4-40 stainless button heads from ebay and/or Fastenal. Started with 6-32 for the bracket to HS mounting but broke 2 drill bits and 1 tap so they ended up being 8-32 with plain socket cap screws/brass washers/rubber washers. I think maybe the rubber washers are not really necessary with Conrads in this particular application. I really didn't know exactly how much heat this beast would make so I just did some guessing.
	

	
	
		
		

		
		
	


	




 The key thing for me the next time I do this is to line up the bracket mounting holes so they fall BETWEEN the HS fins. This will make life much easier when drilling/tapping.


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## Pars

Quote:


  Originally Posted by *digger945* 
_The key thing for me the next time I do this is to line up the bracket mounting holes so they fall BETWEEN the HS fins. This will make life much easier when drilling/tapping._

 

Do the heatsink bracket mounting holes go all the way thru the heatsink, or deadbore into it? From your comment, I would assume this means you are going thru?


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## digger945

Yea all the way through as far as necessary to tap the holes. Maybe a bottom tap might work better.


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## luvdunhill

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Sorry, I meant "optimal/minimal THICKNESS" to the brackets, not "width". Thanks_

 

basically, the thicker the better, provided you can work with them. There's a tradeoff between using wider brackets (even up to the height of your heatsinks, see some of the Dynamight builds as Digipete did this) and the larger thermal junction. The Cadillac solution is find someone who can bend copper for you.


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## digger945

^^Cadillac indeed. I thought about that some in the middle stages of building the Dynamite, just never pursued it much.

 I was a little worried about the rather small brackets I used for this build but after it was completed I could see/feel that it was more than adequate for this amp, and I am biased in the lower 90mA range when I should be around 75.

 Again what I went with was(from top to bottom):
 Transistor
 Thermasil III silicon pad, trimmed to fit nice(Mouser # 53-77-9ACG)
 1/8" thick 1"X1" aluminum angle, sanded and lapped smooth and the width of the pcb.
 I made a jig to bend the legs of the transistors and then assembled/bolted up 2 pcbs(making one channel) and after everything was lined up perfectly, I installed the each channel assembly into the case(the picture I posted above) and tweaked some more until perfect, then carefully remove the 2 halves and solder it up last, after double checking to make sure the outputs are snug.
 It took a lot of time to do this


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## luvdunhill

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Thermasil III silicon pad, trimmed to fit nice(Mouser # 53-77-9ACG)_

 

If you have deep pockets, and shop around, you can do better than these. Check out the various ratings of the Bergquist products at Digikey. Other than that, you can make your own using Kapton tape, which perform very well.


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## digger945

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_If you have deep pockets, and shop around, you can do better than these. Check out the various ratings of the Bergquist products at Digikey. Other than that, you can make your own using Kapton tape, which perform very well._

 

I will definitely check that out for my upcoming dyna build.

 I had to take her apart and change the bias resistors so I snapped a couple more pics to maybe help out.













 I will consider using just one long piece of angle for both boards on the next build.


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## FallenAngel

Quote:


  Originally Posted by *MisterX* /img/forum/go_quote.gif 
_What I did is bought a 6' piece of 2" x 2" stock from Ebay and had the seller cut it into lengths (which he did for free) and then cut the PCB "mounting side" to size with an abrasive disk in my dremel, laid a circuit board over the stock, marked the hole locations, zapped it with the automagic center punch then drilled the holes. 
 Took about 10 minutes to make each bracket. 
 (I made 3 sets of heatsink mounting brackets for less then $10)_

 

Thanks for the info, just one clarification - by "cut mounting side to size", do you mean down the entire 5' length of the L-bracket? That sounds a little difficult (and time consuming with a Dremel).

 I just measured mine to be 1/16" thick and a little worried about that. Likely going with the ones you linked to.


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## MisterX

Yes, down the whole length of the bracket and it was actually pretty easy to cut with a dremel once I sat down and did it. Sure did make a mess though. 
 (if I was going to make another set of brackets today I would use the bandsaw I picked up a couple of weeks ago instead)

 Maybe ping the seller from the auction below and see if he will cut them for you?

Aluminum Angle 36" piece 2" x 2" x .125" - eBay (item 200329712685 end time Apr-15-09 19:46:54 PDT)


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## FallenAngel

Thanks buddy, good link.

 I'm thinking I'll ask to have these cut to lengths. At 1" x 2", it should sit well enough and only stick out by 0.4" so it should be quite manageable. I'll ask if they'll cut short lengths.

 Ooh, found this - looks prettier and 0.5" x 1" so it doesn't have to be cut lengthwise, just to board size.


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## MisterX

Those are a lot more manageable.
 Stoopid.... I looked right at both of them when I was poking around on Ebay and never even thought twice about them.


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## digger945

The 1" X 2" looks perfect for me. Very reasonably priced, not bad on the shipping either.


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## luvdunhill

nm


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## FallenAngel

Hey guys, so I'm biasing my Dynahi here and I notice a little trend - I bias to 0.75V across output resistors, wait for amp to heat up for 15 minutes, see the bias go up, turn it down, wait another 15 minutes until it goes up again, turn it down again... and so on. It's been running on my desk for over an hour at this rate and I just about maxed out the trimpots. When is "enough"? Should I be expecting that eventually this would not happen? I'm thinking that the amp warmed up enough that the transistors are running at a certain temperature and self-bias but if I turn them down too much, they'll never even reach 0.75V.

 EDIT: I have 500R resistors across the 10K trimpots now, but those are being chopped and I'm sticking 1K in there instead for even more adjustment.


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## digger945

Replace the 500 with ~620 is what I did.


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## Pars

Yep. 500 ohms in parallel with a 10K pot will never get above ~476 ohms. 620 ohm fixed resistor will allow up to 583 ohms.


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## FallenAngel

I've got a pair of 680R coming tomorrow but I have 1K around so I'll just use those tonight. 
	

	
	
		
		

		
			





 EDIT: Well, 1K in parallel with 10K certainly makes adjustment fun but after a while, I got it to 750mV and pretty stable there, but does still seem to go up ever so slightly over time. After an hour or so, dropped it to 740mV and it's again slowly climbing up, about 1mV every few minute.
 EDIT2: Finally looks like it's stabilized at 742mV, not moving much in either direction.


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## vixr

FallenAngel...you got PM


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## rsaavedra

As most of you might know, the blackout Headfi suffered in 2007 made us lose all photos that had been uploaded onto the Photo gallery, braking all links that pointed to those pics.

 I recently uploaded all my Dynahi construction related pics onto Picasa, so here are the links, for anyone who might be interested:

Picasa Web Albums - Raul - Building the Dynahi

Picasa Web Albums - Raul - Finishing the Dynahi


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## bhjazz

Good to see it has stabilized for your, FA. The heat of the components, the effectiveness of the heatsinks, the heat of the air inside the case...I'm not surprised it took an hour! 
 I, too, used 620s for the build I was repairing. It was stable at...about 970 (before the repairs, anyway...)!


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## FallenAngel

Yep, and I just got the chassis this weekend so I get to build it. FPE panels won't be arriving until next week, so I get to run it naked for a while. I foolishly ended up ordering only 2 680R resistors instead of 4, used 1K for other position, so one board has one of each.


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## bhjazz

Let me know if you need those last two. I'm sure I have extras!


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## FallenAngel

Thanks for the offer, but I biased it all with 1K's, just takes a little longer and requires a finer touch.


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## luvdunhill

Chris: How complementary did you find the output devices? If you're calculating hfe (rather than grouping by a related parameter, not sure how you did it), could you get identical matches from the npn and pnp device pools?


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## Pars

Not sure if you were asking me Marc, and meant to post in this thread instead, but I wasn't able to match the hfe of pnps vs. npns. Apparently it is possible, but the pnps were rather high, at least the ones I got from Digipete. In fact most of them measured out of spec. Y grade is supposed to be from 120-240, but I had hfes going up to 299. I used basically the circuit in post 5 of that thread. I also used a piece of 1" x 1/8" aluminum clamped (clothespin) to the DUT, and was able to run them long enough that the readings were pretty stable, and the device was not getting hot. It was not a problem to hold them after testing. I went thru the setup 3 times and verified all connections, though I was using a plugin breadboard. This is what the last set of measurements looked like:

  Code:


```
[left]measuring Vrbmeasuring Vrb 2SC3421 NPN2SA1358 PNP #HfeIc (mA)VrbRbIbdgpete#HfeIc (mA)VrbRbIbdgpete 2815676.6724.4349692491.60.029212.762.6729.3999731294.70.0 29157.677.524.4349692491.6158.62821563.3629.3999731294.70.0 26160.178.7224.4349692491.6164.316217.564.0629.3899731294.60.0 5162.179.6624.4249692491.40.0321864.0829.3299731294.00.0 2163.680.3624.4149692491.2167.714218.364.2829.3799731294.50.0 21163.680.4224.4349692491.6165.526220.464.9229.3899731294.60.0 3016480.6524.4349692491.6166.76221.265.1429.3799731294.50.0 9164.180.6224.4249692491.4166.418221.865.3429.3899731294.60.0 19164.180.6824.4349692491.60.02223.165.7329.3899731294.60.0 18164.881.0424.4349692491.60.015224.366.0929.3899731294.60.0 25164.981.0524.4349692491.6171.227224.466.1429.3999731294.70.0 17165.281.2124.4349692491.6168.123225.466.3929.3899731294.60.0 7166.781.9424.4249692491.4167.62422766.8629.3899731294.60.0 316782.0524.4149692491.20.017228.667.3429.3899731294.60.0 22168.682.8924.4349692491.60.07232.368.4129.3799731294.5187.4 27168.682.8724.4349692491.6172.231248.273.1529.3999731294.70.0 10169.483.2524.4249692491.4172.85249.273.3329.3599731294.3215.9 11170.383.7324.4349692491.60.030262.577.3529.3999731294.7215.9 2417184.0824.4349692491.6174.710266.678.5229.3799731294.5217.3 12171.184.1224.4349692491.6175.521267.378.7429.3899731294.6218.2 4171.584.2824.4249692491.40.01267.778.7929.3599731294.3225.1 8171.584.3224.4349692491.6168.7926878.9229.3799731294.5220.2 1171.884.3624.449692491.00.020268.379.0529.3899731294.6220.0 16173.285.1724.4349692491.60.019269.979.5329.3999731294.70.0 23173.985.4924.4349692491.60.08271.379.9229.3899731294.6217.8 31174.685.8324.4349692491.6176.322273.480.5529.3899731294.6222.1 14178.787.8624.4349692491.60.032274.680.9429.499731294.8220.0 13179.788.3724.4349692491.60.012277.281.6429.3799731294.5228.1 6179.888.3524.4249692491.40.013279.182.2329.3899731294.6224.3 2018490.5124.4449692491.80.04286.584.3829.3799731294.5241.4 1519696.3824.4349692491.6199.225288.785.0729.3999731294.7236.3 32024.4349692491.60.011299.288.2329.4199731294.9215.9[/left]
```


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## luvdunhill

that's strange they are out of spec... I've never seen any Toshibas that were out of spec like that, with regard to the datasheet. Also, I'm concerned that you could hold the devices after you matched them, that seems strange to me. Sorta surprising that these aren't more complimentary!

 Totally off topic, but I learned of a very beautiful thing recently... GR1, BL1, etc. grades. They are even narrower grades that customers paid to basically get matched devices right off the assembly line. When I was talking with Linear Systems for a group buy I did, they offered a similar service... lame thing about Linear is they don't mark the packages when they grade the devices... sorta stupid IMHO. Anyways...

 Also, do you need more devices to match with?


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## Pars

Yes, I thought it was strange also, which is why I redid my measurements 3 times, with different base resistance. Digipete had measured his PNPs with ~79K Rb, but was just doing them for 15 seconds or less (no heatsink). From watching the Ic as they heat up on the sink, I can see where his measurements would be lower than mine, as initial Ic would typ. be in the ~70-75mA range but would settle in the low to mid 80's. All but 2 of the out of spec devices were the ones I got from him; the others I got from Scott (digger945). I have them colorcoded in my spreadsheet, but that didn't come over when I pasted the measurements in 
	

	
	
		
		

		
		
	


	




 Sure, I could use more, but I think I have acceptable matches for a 2-ch Dynahi. Scott had posted the close matches he got from Dan Gardner, and they were all in the 153 hfe range or so, so I guess it is possible to find good PNP-NPN matches. Going back thru that thread, it looked like dip16amp (sp?) also had close matches, but used O grade devices for the PNP.

 I'd agree with your assessment of Linear... kind of stupid to do tight grading and not mark them 
	

	
	
		
		

		
		
	


	




alm:


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## rsaavedra

Here's a post for anyone interested in the power consumption of the Dynahi.
   
  Purchased a Kill-a-watt meter from Amazon recently, and I've been having some fun measuring a bunch of stuff at home. Among the measured things, my Dynahi, of course.
   
  Keep in mind, I built my Dynahi using two Condor power supplies, not Gilmore's designed power supply (in case that might make any difference in consumption.) 
   
  Playing Prodigy's "Fat of the Land," and driving two headphones simultaneously: HD600 and HD650. Volume at ~10:30 am, which is the one I commonly use with these headphones. Here's the values I measure: 
   
  Input AC: V = 119.5 V, F = 59.9 Hz
   
*Measured Power Consumption of my Dynahi:*
*0.93 Amp*
*84 Watt / 111 VA*
*PF = 0.75*
   
  Right after powerup the amp was drawing only 0.84 amps, and pf was 0.82. But after 25 minutes the measured values were already as shown above, and they remain the same and stable after 40 min.


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