garAM10BC build thread

[AntonioAnz]

It would be best to see them somehow. What about the 620k resistor question?

Gary, Antonio thinks he received 620k R's instead of the 62k's. Can you shed some light on this?

Hey Jeff, I think I may have mistaken the red multiplier for orange when I reached out previously (didn't have my magnifying glass handy). I saw the 61.9k resistor in the assembly guide photo and assumed because the 62k color code didn't match that I mis-measured the original resistor by a decimal. I have since pulled out these resistors and re-measured them, so it looks like they are the correct 62k values. I do know that the distortion is not due to any diodes being polarized wrong, D6 and D7 look right to me. It does sound like a bias issue of some sort. Here's a link to photos of one of my builds:
https://www.dropbox.com/sh/npbomgfsa9do5tt/AADtdFwrlxjrlW3Mi69PO3Eza?dl=0

Thanks!

 

[Potato Cakes]

D6 and D7 are incorrect. You made the same mistake that I posted about earlier in this thread. The PCB is marked properly, it's just that there are assumptions being made about placement and we all know that does... The instructions do clearly show proper orientation and there is even a photo of what it should look like. You can even see in your top photo that the line showing how the diodes are supposed to go. I did the same thing but didn't catch it till after I had ten of them finished.

Side note to Gary: don't change in the manual. It's perfectly fine the way it is unless you make a revision change to the design in the future. Also, thanks for this project!

Everyone else: please learn from my mistake that I wrote about on the first page of this thread. Double check the orientation of D6-8.

Thanks!

Paul

 

[jsteiger]

...I do know that the distortion is not due to any diodes being polarized wrong, D6 and D7 look right to me.

As potato cakes Paul has stated, D6 and D7 are installed wrong. They are not polarized backwards but you have criss-crossed their holes. Take a closer look at the build guide. As Paul says, it is very clear.

 

[AntonioAnz]

Haha well this is embarrassing  I'll take another look. Thanks for the insight!

D6 and D7 are incorrect. You made the same mistake that I posted about earlier in this thread. The PCB is marked properly, it's just that there are assumptions being made about placement and we all know that does... The instructions do clearly show proper orientation and there is even a photo of what it should look like. You can even see in your top photo that the line showing how the diodes are supposed to go. I did the same thing but didn't catch it till after I had ten of them finished.

Side note to Gary: don't change in the manual. It's perfectly fine the way it is unless you make a revision change to the design in the future. Also, thanks for this project!

Everyone else: please learn from my mistake that I wrote about on the first page of this thread. Double check the orientation of D6-8.

Thanks!

Paul

 

[JW]

Great sound to these! I have them in my master buss of my Yamaha PM2000 console and they're sweet sounding. Haven't listened critically enough to make comparisons to other opamps. But first impression is very sweet and smooth.

 

[JW]

Gary or Jeff,

What is the current draw on these?

 

[[silent:arts]]

+/-24V Idle = +/- 3,5mA
+/-24V +26dBu into 600R = +/- 15mA

+/-16V Idle = +/- 2,9mA
+/-16V +23dBu into 600R = +/- 11mA

 

[JW]

Thankyou Silent Arts

I'm about ready to replace my Yamaha 80100 DOA omamps in my console full scale. I've had so many go bad it's ridiculous. I'm also seeking some info as to how much current the 80100 and 80200 draw to compare.

So, I'm getting to the point where it might be advantageous to buy just the little pcb's (start with 32 . . . . .)  and so, does anyone have a parts list? Or have you compared price with the full kits?

 

[[silent:arts]]

There is a parts list in the assembly manual.

 

[JW]

Oh, duh. I have that. Thanks

 

[karloff70]

Hi there....

Just built a couple of these and having some trouble. They overheat and shut down very quickly it seems.

I used original RCA 2N4036 and 2N2102's for the output transistors. That should work, right?

Can't see any obvious mistakes in component placement or solder pad shorts........any help vastly appreciated.

 

[gar381]

Yes the 2n4036/2n2102 will work in this circuit.  Just be VERY careful about pinout
and make shure that these TO5/TO39 transistor cases do not touch any other component leads.

BTW...With all our listening tests done with the R&D of this DOA,  We have found that the sound
differences are very very very minimal and not worth the vast differences in price to the BD139/140
pairing.

Gary

 

[jsteiger]

The collector will be connected to the case on the metal can transistors so don't let it short to anything!

 

[karloff70]

Thanks guys! Yes, indeed a bit tricky to stop the cases touching other bits. They are not. If the case touches the body (as opposed to the metal leg) of a resistor, is that a problem, too? It isn't touching at the moment, but there is not a lot of room.....

Likely my issue is a transformer one after the opamp then, not the opamp......putting these in a pair of DIYRE EQP5's with vintage Jensen JE-123-S trannies. Must have wired the transformers wrong after all.

 

[noiro]

Hi Gary, Hi Jeff. Question here, is the fivefish test jig reliable to test all opamps, so far I have build many and test all of them using that jig and they all show properly on my scope. But this time around with the garAM10 v.2 all I've got is basically a flat line on the scope, even when I set jig with load, etc. I'm using 15v as power source. All the other Opamps, gar2520, gar1731, OA10, 918 that I build and test give me some result on that jig. So far I build 3 of the AM10 with the same result. I check and they are well build, the diodes D6 to D8 are in the right position. I'm concern of trying them on a module at the moment. Is there a better way to test them as well as of the jig.

 

[gar381]

don't know why they wouldn't work on the 5 fish jig unless
you made the same mistake on all 3 of them.  If there is no
"magic smoke" out of them on the 5 fish give them a try in a module
I doubt you will hurt anything.

Best of luck

Gary

 

[cassio2263]

Hi.
Is there a lot of difference in the BC560 to 560C or B transistor?
In Brazil I only found BC550, BC550b, BC560, BC557 and BC557B.
Can I use BC550 and 560 (B) to replace BC550C / 560C?
Greetings.

 

[gar381]

Hi.
Is there a lot of difference in the BC560 to 560C or B transistor?
In Brazil I only found BC550, BC550b, BC560, BC557 and BC557B.
Can I use BC550 and 560 (B) to replace BC550C / 560C?
Greetings.

560B will work OK for the 560C.  550B will work for any npn not in the input pair.

As for the input pair, just make sure the hfe is over 450 and matched +/- 5. Whatever you can find npn wise is OK as a substitute. even 2n stuff will work but check the pinouts.

The best to use here is the 550C.  Jeff at CAPI does sell matched  pairs of 550C
Its a shame that sourcing parts in some parts of the world is
difficult.  Best of luck on your search.

Gary

 

[cassio2263]

560B will work OK for the 560C.  550B will work for any npn not in the input pair.

As for the input pair, just make sure the hfe is over 450 and matched +/- 5. Whatever you can find npn wise is OK as a substitute. even 2n stuff will work but check the pinouts.

The best to use here is the 550C.  Jeff at CAPI does sell matched  pairs of 550C
Its a shame that sourcing parts in some parts of the world is
difficult.  Best of luck on your search.

Gary

Thank you very much, Gar381.
If I don't find it in Brazil, I'll buy it at Capi.
I found many 2n4036 / 2n2102 transistors manufactured by philips in Brazil - New old stock.

 

[fragletrollet]

Hello!

Anything wrong with using BF139/140 "non-16" in the AM10BC? I got some that apparently are just named "BD-139" and "BD-140" without the "-16" suffix.
And what about in OA-10?

Thanks and keep up the cool stuff,
Magnus