The Adcom GDA 600 modification thread

keck

Thanks H9 and FTGV. And wow, i just seach the price for the Rubycon Black Gate price, and its actually cost ard $80 a pair.
Yes H9, have received all the items for the signal section and power section modthat i ordered.
Will carry out the project whenever i have free time.

bradster56

Hello-Is there only one internal fuse for the Adcom? If so is it a large or small and what is the value? TIA!

pitdogg2

bradster56 wrote: »

Hello-Is there only one internal fuse for the Adcom? If so is it a large or small and what is the value? TIA!

Well looking at the pictures one page back seems 1 fuse. Open it up and look to see the value on yours.

agfrost

If I'm reading this correctly, 3/8A (part F100 on schematic, on power supply board).

bradster56

Indeed the unit has one large version fuse that will soon be replaced by a Hi Fi Tuning "Gold" version purchased for $12.98 on Ebay...

agfrost

Report back if you discern any improvement!

bradster56

I shall indeed...

bradster56

Just received the fuse...It's a no brainer upgrade for 12 bucks...Depending on your system a slight improvement or a major upgrade in sound quality...12 bucks! Do it now before these fuses are gone!

agfrost

For anyone who's still playing with this DAC, Partsconnexion has Dexa +15V and -15V regulators on special for $15 apiece...

I PM'd Fred (FTGV), the "driving force" and "technical honcho" (my terms not his) and he said these would work BUT are not the same pinout as the originals (or the Bursons people were buying on clearance in 2010). This means that some pin-bending or hookup wire will be needed to make the correct connections--this isn't a drop-in replacement as the Bursons were. For this mod, there are some resistors & capacitors to remove and in some cases, to jumper. Fred outlines which parts these are in his post HERE.

Any way, I bought the Dexas (make sure to order one each of +15V and -15V!) and will be getting around to this, eventually. Eventually may mean next summer, so don't hold your breath for an update!

annihilatorg

So were we are almost 8 years later, and I stumbled upon another GDA-600 on Ebay. It's in decent shape cosmetically. Someone else did some repairs along the way. Some replacement Nichicon power supply caps are in sorry shape, the rest is all stock. For now it's fully functional.

If anyone still monitors this thread. I want to take this one up a notch or two. Is it best to stay in the boat, or is the call of Muse or discrete op-amps enough to make money fly from the wallet?

I would like to get this going before long. Any insight to changes in technology would be appreciated. I figure it's more fun to throw money at this bit-ladder DAC than the Schiit you can buy off the shelf. I haven't done any audio mods in quite a few years. I still keep my original modded GDA-600 when all other electronics have long been replaced.

agfrost

Mine's still in rotation and still enjoyed. Puts a cramp in my SACD & DVD-A collection that's easily enough remedied by RCAs directly from my universal player to preamp.

I followed the "don't get out of the boat" directions because sadly I cannot look at a circuit and see areas for improvement. Actually I bought some DEXA regulators that I still have to install, so there's still some work for me to do... (LOL, I see I posted that in the penultimate post in this thread, about 1.5 years ago!)

If you've already got one and are considering another to mod, I guess it would be fun to choose a different op-amp pair--but I guess you could in theory roll those into the old one if you installed with BrownDogs the first time? Kinda rambling here but also kinda hoping you go for it and do something fun and hopefully amazing.

heiney9

I have a pair of Dexa regulators I never installed in mine sitting here. If anyone is interested post in this thread or PM me. I have no use for them

H9

annihilatorg

I PMd' H9 about the dexa regs. Now I need to decide if I want the burson v6 discrete opamps or to stick with the brown dog dual 623. Would feel silly to buy both just to roll. Then it's off to audioconexion and digikey for the rest of the BOM.

george daniel

Mine is still running fine and used daily. Rock on guys!

heiney9

annihilatorg - I will get back to you tonight. I got home later than I anticipated last night and never had a chance to look in my box of goodies.

With the Burson's make sure they will fit, sometimes that's an issue. Also make sure you will have enough to power them. The discrete Burson and Dexa op-amps can draw more juice and these older units weren't designed for that.....just a note of caution.

The Brown Dogs are much older op-amps, but they still hold up today against many of the "latest" IC op-amps. In fact some (including myself) prefer the BD's because that have a more analog sound.

The discrete op-amps are better in many ways than any IC op-amp I've heard (IMO). I use DEXA's in my EE Mini Max Plus and Keces dac's and they are superb.

H9

n25216

Sorry to bring this back from the dead. Seems the 120uF and the 0.1uf caps are obsolete, does anyone know suitable replacements? Don't want to "get off the boat" too much.. Thanks!