Yesterday I received a great condition Adcom GDA-700 DAC. My first experience with the PCM1702 chip, I like it! I have a Audio-GD R-1 NOS already and while it is pretty amazing, I've never felt like I completely vibed with it, mainly because the sound stage is so very in my face all the time. Now with the Adcom, I am hearing pretty much all the same detail but with a much more dispersed and pushed back soundstage. And for about third of the price, this is a win for me.
So I figure now that I have it, it would be worth it to tinker with OP amps and replace some parts since this guy is from 1995 😎.
The tools I own already:
I figure the sound quality can only go up from here. Problem is I don't know/don't really understand how to choose replacement OP amps. I get the general principle but frying my new dac would really suck. I did some digging and found this post for modern OPA alternatives: https://www.diyaudio.com/community/threads/adcom-opamp-semiconductor-replacements.339904/
The ones in the GDA-700 are ADCOM 6AA 9439. According to the chart I can use OPA604 or AD711. I would love to use some sparkos SS3601 OPAs but I need to know if they aren't compatible.
Other than the OPAs, is it safe for me to order all new caps with matching uf/V ratings as the ones already installed? A quick search led me to these caps:
https://partsconnexion.com/products/elna-capacitor-10uf-35vdc-roa?_pos=1&_sid=c38316f85&_ss=r
The only schematic I found was pretty rough but still legible:
https://akdatabase.org/AKview/displayimage.php?album=20&pos=6
This is a big step for me but it's got me pretty stoked! Any and all advice is greatly welcome. Thank you for reading my first post here.
Photos below
So I figure now that I have it, it would be worth it to tinker with OP amps and replace some parts since this guy is from 1995 😎.
The tools I own already:
- Soldering iron
- Good Rosin solder, solder wick
- Decent Multimeter w/ clip and point leads
- Cheap pcb holder
I figure the sound quality can only go up from here. Problem is I don't know/don't really understand how to choose replacement OP amps. I get the general principle but frying my new dac would really suck. I did some digging and found this post for modern OPA alternatives: https://www.diyaudio.com/community/threads/adcom-opamp-semiconductor-replacements.339904/
The ones in the GDA-700 are ADCOM 6AA 9439. According to the chart I can use OPA604 or AD711. I would love to use some sparkos SS3601 OPAs but I need to know if they aren't compatible.
Other than the OPAs, is it safe for me to order all new caps with matching uf/V ratings as the ones already installed? A quick search led me to these caps:
https://partsconnexion.com/products/elna-capacitor-10uf-35vdc-roa?_pos=1&_sid=c38316f85&_ss=r
The only schematic I found was pretty rough but still legible:
https://akdatabase.org/AKview/displayimage.php?album=20&pos=6
This is a big step for me but it's got me pretty stoked! Any and all advice is greatly welcome. Thank you for reading my first post here.
Photos below
Rather than OPA604 or AD711 (which is what the 6AA already is) rather choose something more modern and lower noise. Probably you would need to use it in a SOIC-DIL adapter as the more recently designed opamps tend not to be available in DIL. OPA1641 like this : https://www.aliexpress.com/item/1005006537987334.html
