[patricklang]

Quote:

Originally posted by patricklang The DAC is definitely being fed by +3.3v, not +5. The toslink output is fed from DigVdd, so changing the AnalogVdd won't affect anything else.

Oops, my mistake. I have to supply Vcom as well. This isn't going to be a cut and 1 extra wire anymore

 

[drp]

Great information, though some of it is a little over my novice electronics head. If you develop a paint-by-numbers-like modification list, I (as well as a few others I suspect) would appreciate the steps.

Based on the most recent posts, it seems it is more involved than simply splicing into the USB power and ground with an external DC source. Correct?

 

[patricklang]

Correct. Vcom is the reference level for the DAC. If we up the voltage to 5v, but leave Vcom at 1.6, we will be getting some pretty distorted waveforms. It may be possible to modify the existing Vcom source on the board, but I havn't traced that much out yet.

sorry for the technical detail, I'm a EE

 

[Wodgy]

Quote:

Originally posted by patricklang Even scarier: one channel of mine floats at .6v AFTER THE BYPASS CAP!

Mine has a pretty bad DC offset in one channel too (roughly 0.3v). The other channel is fine.

 

[Glassman]

those two smaller caps near the DAC are defining VCom value - they simply divide incoming voltage, so there's nothing wrong with them.. they can be even replaced for some Black Gates or simply tantals if you want.. as for the ground issue - all you have to do is to tie the negative leg of your 5V supply to the Sonica's common ground and apply positive leg to AVDD pin on the AKM.. I think it's pretty simple..

 

[patricklang]

Caps to divide voltage? I'll have to take a closer look tonight, I'm used to seeing resistor voltage dividers. If thats the case (2 caps in series), then we shouldn't have to change anything for Vcom

Although, we might get some better results by using a more stable Vcom, any power supply ripple is going directly to the output right now.

I'd still like to remove the DAC for a picture to make a more complete schematic, and find the best place to cut the +3.3v trace.

 

[Glassman]

regarding the caps dividing voltage, look into the DAC's datasheet.. it's a common practice in fact.. it has something to do with AC & DC properities of such divider..

 

[zaen]

Quote:

Originally Posted by Glassman you don't really need those caps in the signal path at all, .....

Sorry to be joinin in late, but I just aquired a Sonica and am interested in improving the clarity...

is the above statement true? Can someone please explain and possible enlighten me on the possiblity of just removing the caps...and the benefits of that....and if so...how to make it all work...thanks

 

[Submarinesailor]

Good job, Voodoochile! What other "Oh yeah, I already did that" mods you got hanging around? Start another thread and tell us about it, it's a great learning tool. No, I am NOT boot licking!

 

[Voodoochile]

Quote:

"What other "Oh yeah, I already did that" mods you got hanging around?"

I've been mostly messing around with PPA stuff for a while now, but have some other projests on the back burners that I am trying to get to the front burners. All I need to do is figure out how to get 36 hours out of a day and things will be all better!

 

[Glassman]

Quote:

Originally Posted by zaen Sorry to be joinin in late, but I just aquired a Sonica and am interested in improving the clarity... is the above statement true? Can someone please explain and possible enlighten me on the possiblity of just removing the caps...and the benefits of that....and if so...how to make it all work...thanks

sorry, actually not.. if you ommit them, you get >2V of DC on outputs..

 

[beats unbeaten]

Anyone know what purpose those SMT components (looks like two resistors and a cap per channel) next to the output jack serve?

Wondering if they could be eliminated/bypassed...

 

[flecom]

those are 220ohm and 27k resistors, plus a cap of what value im not sure...

the 220ohm and 27k resistors are there in the typical diagram on the datasheet, the cap goes between the output and ground on each channel... im guessing these can be removed, not sure what they are doing there? anyone? its C28 and C29 right next to the headphone jack

also my question and reason for bumping this thread from the dead

would replacing the 220ohm and 27k ohm resistors after the 10uF cap make a difference? from the little surface mounts to say some Vishay/Dale resistors?

 

[Garbz]

no doubt it would make a difference, but would it be worth the effort and the expense is another question.

Afterall my gilmore amp uses the cheapest nastiest resistors i could find. And it sounds like a chorus of angels.

Now the black gate mod on the other hand did wonders for my transit.

 

[patricklang]

I'm still hoping to get the time to do my external PS mod, but I think the real sticking point on Sonica quality is the limited PS given to the DAC.

That DAC uses a single supply (+3.3v). THe output is centered around half that, or 1.65v. This gives a theorical voltage swing of 3.3v, but in reality my guess is that it is more like 3v. So, you get -1.5 to 1.5, rather than -2 to +2 you would get from good audio gear. That's a sad loss of resolution.

This also means that the average (DC) level of the DAC output is 1.5v. This is why the blocking capacitors are CRUCIAL. 1.5dc into your camp (if it doesn't have its own blocking caps) would fry your phones. I have not heard black gates as DC blocking caps, but I would expect them to make the most improvement for the effort in the Sonica.

So, with this said, an external PS would lose the portability of the sonica, so why not skip the effort and go to an ART DI/O? Much less effort.

Also, if you have a desktop, get a Revo

They sound better than the Sonica at only $40 more, and are very close to $200 pro cards when it comes to unbalanced audio.