The Adcom GDA 600 modification thread
george daniel
Posts: 12,108
OK here we go,first the schematics
http://www.audiokarma.org/forums/showthread.php?t=92160&highlight=modding+an+adcom
Opamps-- I purchased these (2)
http://cimarrontechnology.com/twopre-mountedopa627auop-ampson020302adapterpnopa627au-020302s.aspx
The circuit board is clearly labeled,,and corresponds to the schematics
Remove the opamps and install the new opamps--careful attention to pin #1 orientation,,in the case of the dogs,,pin 1 corresponds with the "b" in browndog.The adcom opamps were marked with a notch of sorts denoting the pin #1.I would suggest installing the DIP 8 sockets, then you have the ability to roll opamps like tubes,if you prefer. Next you want to install 120uf/25 volt electrolytic caps to serve as local power supply reservoirs. the positive lead from the cap goes to pin 8(opamp) and the negative cap lead to pin 4.Then connect the remaining + and - leads on the caps,and tie them to ground.I ran a wire fron the caps which I mounted on the underside of the board to the ground of the power supply,which is easily distinguished.
Digikey # P10270ND
Remove the ferrite inductors at L 500 & L501nand replace with "jumpers",, as they might hide the opamps "flavor" if left in place.
Remove the caps @ C 550 & C 551--nothing goes back there.
I replaced the .1 uf bypass caps(not a requirement) and replaced with Digikey part # P4525ND .1 uf/50 volt stack metal film caps.
On to the power supply--
Remove the two 10uf caps @ C100 & C 104 470uf/35 volt Panasonic Fc caps,,Digikey part # P10301ND
Next replace the two .1uf caps C122 & C 123 with 22uf/25 volt cpas,this will increse the ripple rejection.
Now you are done,, and prepare yourself for some sweet,detailed,and involving analod sounding digital tunes.
There are some film caps in the analog section that are easily identified and labeled,,should not make much of a difference,,but since Sonicap has a sale,,I'll replace them next week,,what the heck.
I give all of the credit to Fred Thompson,who helped me patiently via e-mail,,he answered all of my questions,and made the suggestions,,so,a Big Thank you to Fred,,for without his help,I would not have been able to complete this mod.
Cost--less than 200 dollars(I'm including the sonicaps) which are optional,and would drive the cost down to about 110 dollars.
Here is a link to opamp pin config
http://www.diyhi-fi.co.uk/pdf/Datasheets/lme49720_pinout.pdf
Pic 3 shows the new opa's installed.
http://www.audiokarma.org/forums/showthread.php?t=92160&highlight=modding+an+adcom
Opamps-- I purchased these (2)
http://cimarrontechnology.com/twopre-mountedopa627auop-ampson020302adapterpnopa627au-020302s.aspx
The circuit board is clearly labeled,,and corresponds to the schematics
Remove the opamps and install the new opamps--careful attention to pin #1 orientation,,in the case of the dogs,,pin 1 corresponds with the "b" in browndog.The adcom opamps were marked with a notch of sorts denoting the pin #1.I would suggest installing the DIP 8 sockets, then you have the ability to roll opamps like tubes,if you prefer. Next you want to install 120uf/25 volt electrolytic caps to serve as local power supply reservoirs. the positive lead from the cap goes to pin 8(opamp) and the negative cap lead to pin 4.Then connect the remaining + and - leads on the caps,and tie them to ground.I ran a wire fron the caps which I mounted on the underside of the board to the ground of the power supply,which is easily distinguished.
Digikey # P10270ND
Remove the ferrite inductors at L 500 & L501nand replace with "jumpers",, as they might hide the opamps "flavor" if left in place.
Remove the caps @ C 550 & C 551--nothing goes back there.
I replaced the .1 uf bypass caps(not a requirement) and replaced with Digikey part # P4525ND .1 uf/50 volt stack metal film caps.
On to the power supply--
Remove the two 10uf caps @ C100 & C 104 470uf/35 volt Panasonic Fc caps,,Digikey part # P10301ND
Next replace the two .1uf caps C122 & C 123 with 22uf/25 volt cpas,this will increse the ripple rejection.
Now you are done,, and prepare yourself for some sweet,detailed,and involving analod sounding digital tunes.
There are some film caps in the analog section that are easily identified and labeled,,should not make much of a difference,,but since Sonicap has a sale,,I'll replace them next week,,what the heck.
I give all of the credit to Fred Thompson,who helped me patiently via e-mail,,he answered all of my questions,and made the suggestions,,so,a Big Thank you to Fred,,for without his help,I would not have been able to complete this mod.
Cost--less than 200 dollars(I'm including the sonicaps) which are optional,and would drive the cost down to about 110 dollars.
Here is a link to opamp pin config
http://www.diyhi-fi.co.uk/pdf/Datasheets/lme49720_pinout.pdf
Pic 3 shows the new opa's installed.
JC approves....he told me so. (F-1 nut)
Post edited by george daniel on
Comments
Dynaudio Contour 3.3, Dynaudio Contour T2.1, Polk OWM3, Polk DSW micropro 1000 (x2),
Pioneer Kuro 50" Plasma, Phillips Pronto Control w/Niles HT-MSU.
Thanks George, please PM again with regards to getting those extra caps you have. Also I was confused with the highlighted part. What is this in reference to? Are you saying C550 and C551 have a bypass cap?
Awesome can wait to get going on mine.
H9
Pass Aleph 30 | EE Avant Pre | EE Mini Max Plus DAC | MIT Shotgun S3 | MIT Z P/C's | updated SDA 1C| SQ Box Touch/Welbourne Labs P/S- Tubes add soul!
Do you have a photo of this with the wire routing, etc? You say caps? How many?
Pass Aleph 30 | EE Avant Pre | EE Mini Max Plus DAC | MIT Shotgun S3 | MIT Z P/C's | updated SDA 1C| SQ Box Touch/Welbourne Labs P/S- Tubes add soul!
H9-- the caps that I replaced(.1uf) are the opamp bypass caps,,it's not mandatory,,I just had the spare caps,so I replaced them,,I have 4 set aside for you,,along with some others.
Or is this it P1177-ND a bi-polar cap
I have ordered all new caps to replace these 15 year old ones since I am in there, including some Sonicaps, but this polar thing and the parallel and wire thing has me at a stand still:o. I guess I need pics:D
Does this look like it might be an issue? Getting ready to start to get a parts list together for this and I want to take adv of the Sonicraft sale, but if they don;t work then I don;t want to be stuck with them.
Pass Aleph 30 | EE Avant Pre | EE Mini Max Plus DAC | MIT Shotgun S3 | MIT Z P/C's | updated SDA 1C| SQ Box Touch/Welbourne Labs P/S- Tubes add soul!
My bud who helps me with these mods suggested this: If the new leads are too large in diameter to fit in the PCB holes, clip the old caps as close to the body as possible leaving a small part of the old lead in the PCB. That way you have something to solder the new lead to.
H9
Pass Aleph 30 | EE Avant Pre | EE Mini Max Plus DAC | MIT Shotgun S3 | MIT Z P/C's | updated SDA 1C| SQ Box Touch/Welbourne Labs P/S- Tubes add soul!
You are my hero! I understand why you are so impatient to hear how this went for me, but I waited for weeks for your instructions:p So here is what I have to say:
The hardest part of the whole thing was getting the old caps out
I also broke the little wire for the "lock on" light in front. I was trying to get it back in and it pulled right out. I have no idea how much impact the sonicaps made, you'll have to tell me.
I can't even describe what I am hearing. Familiar music just doesn't sound so familiar any more. The detail and low end are the biggest impact that jumps out to me right now. These SDA 2's never sounded like this before.
Thank you for making sure I understood about the wire jumping and where to put the caps on those op amps. It was nothing to do.
Without you doing this mod first, I would never have heard this DAC sound like this. I knew I was always happy I had bought it new, but now it's a whole new piece of equipment.
If you have one, do this mod. It really is pretty easy, and well worth it!!!
The leads fit just fine. They are smaller on the smaller caps.
So you already replaced the yellow mylars around the op-amps with Sonicap Gen I's and the leads fit?
H9
Pass Aleph 30 | EE Avant Pre | EE Mini Max Plus DAC | MIT Shotgun S3 | MIT Z P/C's | updated SDA 1C| SQ Box Touch/Welbourne Labs P/S- Tubes add soul!
Thanks
Ben
these are the values I need to replace the yellow mylars around the op-amps.
(2) 0.022uF
(2) 0.0039uF
(2) 0.0027uF
are those the values you guys got?
H9
P.s. George I'll be sending a PM shortly with the info you requested.
Pass Aleph 30 | EE Avant Pre | EE Mini Max Plus DAC | MIT Shotgun S3 | MIT Z P/C's | updated SDA 1C| SQ Box Touch/Welbourne Labs P/S- Tubes add soul!
sold for 150 dollars-- there is a Stan Warren modded one for 245,, good luck with your sale.BTW,, the way that you are approaching it(read the rules),is generally frowned upon here.I doubt that you will have any interest because your asking price is probabally too high. Good luck.
http://cgi.ebay.com/ADCOM-GDA-600-DAC-D-TO-A-CONVERTER-WORKS-GREAT_W0QQitemZ290405244972QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item439d80602c
http://cgi.ebay.com/Adcom-GDA-600-Digital-to-Analog-Converter-USA-Nice_W0QQitemZ300396468374QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item45f1065896