The CJO Conrad Johnson (DAC) D/A 3 Modification Thread

[lowpoweraudio]

Hello,

Digging around in one of these and pretty amazed and the opportunity for mods. The TDA1305 really had a nice sound. The chassis constrution makes these super easy to work on Looks a like the dac feeds some 1nf filtering caps right off the TDA1305 replacing these with some REL Caps, then it seems to feed some .5uf caps and then into the output stage with some big 10uf mylar with .5uf bypasses. Easy to upgrades here.

Anyone have a schematic for the D/A 3?

Thanks in advance
Lowpoweraudio
Alex

[admin]

Unfortunately, I haven't seen the schematics for any of CJ's older DAC's or media players. If you do get a copy, send me it and I'll add it to our database.

[lowpoweraudio]

Thanks Admin! I will post if I can connect with one.

[lowpoweraudio]

This is some brief documentation of mods to the CJ D/A 3 introduced in March, 1996. This info may also be posted elsewhere but I wanted to make sure it was on CJO as valuable resource for CJ owners.

The vintage D/A 3 now over 25 years old and is likely considered obsoleted by most audiophiles. After more than two decades compact disc users have watched digital spin through several "new" technologies, R2R-Multi-bit ladder, Bit-Stream, up-sampling, Delta-sigma, more up-sampling, SACD, to name a few. How astonishing now in 2022 to see many well known audio journalists going back to 20-30 year old tech in embracing NOS (no over sampling) implementations of 80s 16bit ladder dacs in their personal systems, as being more listenable? Perhaps the old TDA-1305 hold some new tricks as well.

Looking at the CJ D/A 3 we find a wonderful implementation of the TDA 1305 bitstream dac with a Class A fet output stage. I thought to see how updating a few of the output capacitors with newer designs might impact the sound. The results are astonishing!

20211228_162431.jpg (3.21 MiB) Viewed 1931 times

Here is a pic showing the D/A 3 output caps with two 10uf large (mylar?) and two .5 uf polystyrene bypass caps.

20211228_152525.jpg (3.08 MiB) Viewed 1931 times

Here is a pic post mod with the previous caps replaced with 10 uf Mundorf M-Caps and .47 uf EVO Aluminum-Oil bypasses. In retrospect I could have also used EVO Aluminum-oil for the 10 uf main caps but I had the M-Caps already so I just used what I had on hand.

Hre.jpg (3.37 MiB) Viewed 1931 times

Next I will be adding two more .47 Aluminum-oils to replace the two .5 uf input caps (shown sitting in parallel on the right side of the last pic) and will update the two 100ohm output resistors with a pair of audio-note tantalum resistors. more to come.

Alex
Lowpower audio

[admin]

Great stuff. As a previous owner of the D/a-2b DAC, I can say that CJ made some really wonderful digital products. Although they are now completely in the realm of analog signal processing, I really miss my DAC sometimes even though my new modern one is "superior" on every measurable test. It didn't have all the fancy modern specs of accepting high res audio, but when I was spinning those CD's, that sound was really nice. It just sounded right.

Great to see you are bringing the life back into a vintage but still great sounding device.