Source modding

I wanted to start a thread on modding DACs. Most sources have DACs with a compromised I/V stage which is usually followed by a recon filter and /or buffer.
These two stages are the most crucial as they are essentially the analog output stage on the "DAC" source.

It so happened that I had an opportunity to buy a Sonic Frontiers Assemblage DAC 2 which uses dual PCM1702 DAC chips with the famed PMD100 digital filter. It uses a CS8412 for the digital receiver.

The one I bought came with caddock resistors and multicap capacitors int he I/V and buffer sections.
This was offered as an upgrade option if I remember by pats connection back in the day. So for 130$ shipped I was mighty impressed.

These small DACs have a reputation as giant killers. They retailed at 400$ in the late 90s.

Anyway..here are the mods I did

1> Replaced all old electrolytic caps in the DAC and I/V section with newer Nichicon Muse caps
2> Replaced I/V opamp with THS4031 opamps (adapter + opamps cost 12$ for each channel. Adapter is high quality one used in high freq applications and cost 7$ each)
3> AD797 for recon filter+buffer section. (9$ each)
4> PPS Coupling caps between the rails and NPO ceramics between rail to ground for all opamps

5> Last but not least K grade PCM1702 DAC chips (25$ per channel). This gives lower Inter modulation distortion and lower THD.

The transformation has been amazing. Everything is a lot livelier..better soundstage. The bass has just completely transformed. Tight and fast with plenty of impact.

I am totally sold on the fact that the THS4031 opamp is the best opamp out there for I/V and the AD797 is superlative in its filter role.

Total cost of this pgrade was about 120$ bringing the total i have spent on this DAC to 250$.

I won't make comparisons but suffice it to say..this little DAC bats way high up in the order.

Some pics

Before


After