modding an Adcom GDA-600 DAC?

That looks like a relatively easy board to modify. The components are hole mounted and not surface mounted?
 
Yes the components are "thru the hole" mounted.One thing that I would do ,is install the DIP sockets, that way you can roll opamps like tubes,just my .02 worth.
 
Well,, I finished the mods-- I went with the Browndog OPA 627 adapters,, replaced some caps in the power supply,removed and jumped the ferrite inductors.Actually,a pretty easy upgrade,, the resulting sound has taken this unit to an entirely different level.The detail is just stunning,not bright at all,it seems faster,soundstage is deep and wide,, almost scary,as I've heard things on familar songs that I did not know were there.The caps were obtained from digikey,the most expensive component was the browndogs,,I have a total of about 215 in this unit,including the original cost. Wow,,just wow.If anyone needs a step by step ,just shoot me a pm,,if you own one of these you owe it to yourself to perform this mod,as you do not know what you are missing. :banana:
 
Thanks much for the post. I own this DAC and just might try this. Did the I/C's remove easily? Sometimes solder can be difficult. Are the pcb's multilayer? I don't have a good solder station at home so must rely on a solderer at work who sometimes can be a bit impatient. It's one for thing for her to destroy company property, and quite another to damage my DAC. But if they remove easily I'll move forward.
Joe
 
I used a rat shack desoldering iron,,,the one with the bulb sucker,, an it's not a terribly difficult thing to do,, but proceed slowly,, i used a teeny teeny device kinda like a drill bit,,that heating and air folks use to clean out pilot lights/lines to clear any residual stuff out of the trace/hole after I desoldered.If you take your time,you'll be fine--good luck--let us know how it turns out. Good luck.
 
dangerbird said:
If anyone needs a step by step ,just shoot me a pm,,if you own one of these you owe it to yourself to perform this mod,as you do not know what you are missing. :banana:
Click to expand...

If you feel motivated to provide step-by-step details, I would encourage you to post them here in this thread for all to see!

Your positive results have me thinking about trying these mods myself... but this will have to wait as I currently have too many projects in progress.
 
I am looking at buying one of these, and I am terribly excited about these mod's!!!! I found this on google, and thought it would turn out being just another OLD thread..... Thanks for all the info guys!!!!

Ron
 
Well..... It looks as though someone needed it more than I! Damn, I wanted that thing pretty bad. The next one in my sights is a Monarchy Audio 22 B, from a fellow 'goner. I was really looking forward to the Adcom, because it seemed so easily modified. I'm on an extreme budget, seemed that would've been the ticket.

Thanks for putting up the info, I will follow this thread for sure!!

Ron
 
I'm starin' down the barrel of a GDA-700/PMD-100 HDCD, with box, warranty card and original receipt/brochures. It's a little spendy at $250, but may be worth it. I can only assume that modifications would be very close to that of the 600.

We'll see,

Ron
 
Found one! I will have to pick up the opamps, and get this thing going. I will have yungin listen to it before and after, to get a good A/B comparison, as my ears may fail me. They work as well as they once did.

Ron
 
I recieved your e-mail,, you are gonna love this DAC even more after you tweak it.When I first got mine, it was exactly what I was looking for,,somewhat detailed but very laid back in my system.Now,,I have detail in spades,,no brightness,,no digital" edginess",, I did not come up with this mod on my on,,I'll have to give credit to a gentleman who works for a respected audio manufacturer, who's name and company I will not mention,unless I get his permission,, my point is,as I have performed this mod in stages,then listenened to it,the biggest bang is the op-amps,in my case the Browndog OPA 627's found here

http://cimarrontechnology.com/twopre-mountedopa627auop-ampson020302adapterpnopa627au-020302s.aspx
*Carefull attention should be made as to the orientation of the power pins,as it is the pin adajacent to the "B" on the adapter, but a call to them will answer any questions you might have.I would strongly suggest that you use the DIP 8 sockets,as they can be soldered in,and then you can roll opamps if you like,,I was too impatient to do this,lol.

Next I replaced the 10uf caps in the power supply C-100 and C-104 with 470uf/35 volt Panasonic FC series from Digikey(since I had to buy 10,,I have 8 left over,,yours for the asking)

Next-- remove the .1 uf caps in the power supply (C122 and C 123) and replace with 22uf/25 volt caps--this will increase the ripple rejection(hey,,I'm just doing what I'm told)

Next I removed the ferrite inductors @ L 500 and L 501 and REPLACED them with jumpers(it was suggested that these might mask the flavor of the opamps)

I then removed the caps @ 550 and 551(right next/behind the ferrite inductors.) Nope-- no replacement is needed.

I then allowed the opa's to "burn in " for about 96 hours or so(cd on repeat-dac on,, pre on,,amp off)
I am extremely happy with the DAC at this point,as when performing A/B tests with my CD player(Rotel 855(tweaked), there is a huge difference.

But,, wait,, we ain't thru yet,,if you care to get the most outta this thing,, my final tweak is to replace the the bypass caps @ C 528,529,530,531 with .1uf/50 volt metal stack film caps(Digikey),,this was done friday night,,so far so good,,now today I'm gonna add 120uf/25 volt electrolytics in parallel,,more on that after I perform that task,,I'll report back later today,at this point I will be done.
I apologize for the somewhat "chopped up" way that I have done this,but I wanted to get it down before I forgot,, I am not an "expert" by any stretch of the imagination,,this mod is not that difficult if you take your time and use the proper tools,, such as a good de-soldering tool from Rat Shack--10 bucks,and a good iron.As mentioned before,I have parts left over,,so if you are interested,,pm or e-mail me,and I'll share until they run out.

Later--george
 
Wow! I am really looking forward to this project! I sent an e-mail to you George, and I really do appreciate all you help in this project, I'm sure I'm not the only one. You have me highly motivated to get this done now. Just have to set on it long enough to save up the hundred bucks for the BrownDogs and dip sockets. I'll update as we go.

Thanks again George!!!!!!

Ron
 
dangerbird said:
I recieved your e-mail,, you are gonna love this DAC even more after you tweak it.When I first got mine, it was exactly what I was looking for,,somewhat detailed but very laid back in my system.Now,,I have detail in spades,,no brightness,,no digital" edginess",, I did not come up with this mod on my on,,I'll have to give credit to a gentleman who works for a respected audio manufacturer, who's name and company I will not mention,unless I get his permission,, my point is,as I have performed this mod in stages,then listenened to it,the biggest bang is the op-amps,in my case the Browndog OPA 627's found here

http://cimarrontechnology.com/twopre-mountedopa627auop-ampson020302adapterpnopa627au-020302s.aspx
*Carefull attention should be made as to the orientation of the power pins,as it is the pin adajacent to the "B" on the adapter, but a call to them will answer any questions you might have.I would strongly suggest that you use the DIP 8 sockets,as they can be soldered in,and then you can roll opamps if you like,,I was too impatient to do this,lol.

Next I replaced the 10uf caps in the power supply C-100 and C-104 with 470uf/35 volt Panasonic FC series from Digikey(since I had to buy 10,,I have 8 left over,,yours for the asking)

Next-- remove the .1 uf caps in the power supply (C122 and C 123) and replace with 22uf/25 volt caps--this will increase the ripple rejection(hey,,I'm just doing what I'm told)

Next I removed the ferrite inductors @ L 500 and L 501 and REPLACED them with jumpers(it was suggested that these might mask the flavor of the opamps)

I then removed the caps @ 550 and 551(right next/behind the ferrite inductors.) Nope-- no replacement is needed.

I then allowed the opa's to "burn in " for about 96 hours or so(cd on repeat-dac on,, pre on,,amp off)
I am extremely happy with the DAC at this point,as when performing A/B tests with my CD player(Rotel 855(tweaked), there is a huge difference.

But,, wait,, we ain't thru yet,,if you care to get the most outta this thing,, my final tweak is to replace the the bypass caps @ C 528,529,530,531 with .1uf/50 volt metal stack film caps(Digikey),,this was done friday night,,so far so good,,now today I'm gonna add 120uf/25 volt electrolytics in parallel,,more on that after I perform that task,,I'll report back later today,at this point I will be done.
I apologize for the somewhat "chopped up" way that I have done this,but I wanted to get it down before I forgot,, I am not an "expert" by any stretch of the imagination,,this mod is not that difficult if you take your time and use the proper tools,, such as a good de-soldering tool from Rat Shack--10 bucks,and a good iron.As mentioned before,I have parts left over,,so if you are interested,,pm or e-mail me,and I'll share until they run out.

Later--george
Click to expand...

He's not lying! This is so great, this mod. And thanks for all the info and help. I am just as excited as you are about the mod
:music::D
bs
 
Glad that it turned out well for you :banana: I might buy another one after hearing mine,,it's really a fun mod,,and the payoff is HUGE:thmbsp:
 
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