[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]

Quote:

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.

Quote:

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]

Quote:

Originally Posted by rds /img/forum/go_quote.gif 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

 

[hopeless]

I've just finished modifying a Super Pro I had (not the newest that I'm awaiting), a non USB model (I don't care for USB, anyway).



It's playing right now and wow, is it good.


I...


Changed the 4 + 2 caps in the signal path with 6 WIMA MKS2 4.7uF 50V (the two output caps being bypassed with 100nF Evox MMK too).

Put a Rubycon YXH (high ripple current) 1000uF 25V in the main power line, bypassed with a 100nF Evox MMK.

Soldered a LME49860NA on the pcb.

Changed the DAC and receiver power supply caps with 47uF Rubycon ZLH (very low ESR).




Sounds extremely good (playing Jason Lytle, "Yours truly, the commuter"). Musical, airy, and very revealing; what more can I ask?

 

[hopeless]

It also served as a test for the possible mods for my next incoming Super Pro 707 (I'm too in love with this little very musical DAC).


I say possible because when it arrives I'll be comparing the stock one with the modified one, and will decide what sounds better. Will report back.

 

[hopeless]

Lucky me that I'm loving the sound with the LME49860 inside, 'cause I couldn't change it easily.

Actually I'm glad I did so because I quite dislike sockets.

Everything works fine, and the sound is very happily warm + analytical. It's very balanced, but lively. I didn't (maybe) expect such a satisfactory result. We'll see if the stock new DAC 707 stands the comparison. If it does, I may not touch it at all.

 

[hopeless]

Well...


The brand new Super Pro 707 just arrived today.

I have briefly switched the two 707's and...


Well the stock new one is very musically charming, clearly thanks to the LT1364. The other one is probably "more transparent" though, if that's what matters (hmm).

Honestly the stock one with its "rubbish" SMD output caps and all, doesn't really sound very much less detailed than the modified one (as above), really.

I would leave the new one untouched, weren't it that in an impulse I aready purchased the parts for modifying it too.

However the opamp will either remain the (excellent indeed, in this DAC) LT1364, or will become a EL2227 (just got this) or a OPA2211AID (which I know sounds great).


The LME49860... I like it, but it lacks that very special LT1364 charm. I think that the OPA2211 is a sweet spot between them. Who knows about the EL2227... so curious to discover.

 

[hopeless]

I've now modified my newest one too!

As I opened it I realized that it has been extensively reengineered. Now the regulators are 2x LM317 (no more just one), but especially, all of the components have been made to fit on the upper side of the PCB - not a single resistor, or chip, to be found below. There are some new parts too.

Oh and interestingly on the leads of each of the 4x stock film 4.7uF 63V caps (which appear to be good BTW) there are small ferrite beads (so 8 beads in total). Also the layout has been rearranged so that a DIP socket fits well without moving anything.

So did I a socket put.

And on it I put a LT1358.



Well, I've compared the new one with LT1358, to the older one with LME49860 (with the bypass 100nF caps replaced with Wima's, BTW, and the ones in parallel with the output caps just removed because they made the sound worse than without)...

Clearly the one with LT1358 sounds better (though I also love the other's cool refreshing character). It's more "real". I like this opamp even better than the LT1364. Excellent opamp (not that I'm going to keep it forever...just received some EL2227 BTW).

 

[MrSlim]

Check out this thread, they've bypassed the output stage all together on a 4397/8 DAC, and have done the same on the 707. Not that it'll fit in the case..
diyAudio Forums - Experience with this DIY DAC ? - Page 11

 

[hopeless]

I don't feel the need for that at all (assuming that it would sound good). Next opamps I'll try are EL2227 and OPA2211AID, and maybe OPA2822 and OPA827.


EDIT: Thanks, anyway. I'll give it a look (is it transformer coupling?).