DAC 707 Mods

[rds]

Here are some mods I did on the DAC 707 Super Pro.

But first:

I have traced the analog output stage of the DAC 707 Super Pro and have drawn the schematic in a way to make it easy to compare to the recommend stage from the CS4398 datasheet. As you can see the 707 using a single ended power supply for the opamp.




The front side of the 707 with the output stage schematic superimposed:


Now the mods so far...

The stock board:


Some stuff removed:


Film caps added to the bottom of the board. The blue ones are BC Components 419 mkp are parallel to the output coupling caps (which were switched to Elna Cerafine). The yellow is stock moved from the top because there is no room. The grey one is for filtering the opamp power. I removed two garbage smd caps on the output of the opamp and connected the opamp output directly to the Cerafine/419s with the red wires. If you look closely you can see where the caps were.


The opamp is socketed and the opa2107 is being used. The opamp power cap is replaced by 470 uF Panasonic FM. The output coupling caps are replaced with Elna Cerafine (bypassed by the blue BC Components caps).
A second 1000uF Panasonic FM was added for power filtering/stiffening.


A power switch was added. I don't like things that spark when you plug them in

[andrew jc]

rds Great work as usual! How does it sound compared to a stock unit? Also how does it compare to the Alien dac?

[rds]

How does it sound compared to a stock unit?

It's much better. Stock this dac is definitely not "hi-fi". Now it sounds very nice.

Also how does it compare to the Alien dac?

They are very different. The cs4398 is a great chip, but is best left to hi end circuits in my opinion.
I would take an alien with nice output caps over the stock 707 any day.
The alien has a much "warmer" and "darker" sound than the 707. You could also say it is more bass heavy and "veiled". I find the textural qualities of the alien to be very nice and it has a lower noise floor.

[mapstec]

Please believe that rds knows what he is talking about, and that there actually are people who agree with him!

That is not to say that I can not agree with parts of what you say.

And can we all please include a few more "imho" in our posts?

Just my two cents
Cheers

[mapstec]

So we all agree that we can like this DAC with careful selection of components and/or modifications.

@creek - The last opamp I had in there was the LT1057 - and I liked the sound.

btw: I send mine of today to rds for modding - I look forward to the result.

[CountChoculaBot]

Originally Posted by rds

OP updated with the final mods.

You stuffed the hell out of that board, can't wait to hear it

[rds]

Original post updated again with a schematic of the 707 analog output.

[rds]

Modding complete