EMU 0404 USB Modding FINISHED!
Jun 6, 2008 at 6:12 AM Post #16 of 50

grenert

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Quote:

Originally Posted by foreverzer0 /img/forum/go_quote.gif
for the large cap I used the largest capacity I could fit from the FK series, the headphones caps (2) were direct replacements, the line-out caps were C series for decoupling and are the same values except the V are much higher (which doesn't harm it in anyway).


Well, I'm glad you like the end result, but I've opened up my own 0404 USB, and what I believe to be the stock headphone caps (the ones closest to the headphone out) are 220uF, not 22uF. 22uF is pretty small for headphone out decoupling, considering the relatively low impedance of most headphones.

Also, I think those five 47uF capacitors near the line out section serve as local power supply caps (someone who knows more about this stuff than I should probably confirm this). You'd probably do better with larger capacitance, low impedance caps like Panasonic FM/FC or Nichicon UHE/PW, rather than those gigantic Blackgates (although given their higher voltage, they probably have less impedance than the stock caps).

I completely agree that the stock wall wart is a joke (basically a cell phone charger), and replacement is definitely a great idea.
 
Jun 6, 2008 at 11:51 AM Post #17 of 50

amb

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To follow up on my post above, I measured the resistance between the 3.5" mini output jack and the 1/4" TRS output jacks with a DMM, and found unexpected results. The sleeves all have zero ohms across them, so the grounds are all connected together as expected. However, there is 24.8 ohms between the left channel 1/4" jack's tip and the 3.5mm mini jack's tip (I expected it to be zero ohms). The right channel 1/4" jack's tip to the mini jack's ring is 22.8 ohms. So there is some asymmetry.

What even stranger is that the left channel 1/4" jack's tip to the 3.5mm jack's ring is 21.4 ohms, and the right channel 1/4" jack's tip to the mini jack's tip is 26.1 ohms (I expected both of these to be infinity, because these are across the two channels). I then tested each of the 1/4" jack's tip to sleeve (ground), and got 11.4 ohms and 12.2 ohms, respectively.

Ah hah. Not having opened up the box to look, I think I understand what might be happening. The 1/4" outputs are probably coupled through an unbalanced-to-balanced conversion transformer and I am measuring the winding resistance. The mini jack output is probably before the transformer. So my resistance readings are a bit bogus because it includes connectivity through ground. But it does show that the two sets of outputs are not exactly the same.

Here is a diagram of what I think is at the 0404 USB's outputs:
attachment.php


The measurements show that the transformer winding resistance is around 10-12 ohms per section, which is a really low impedance load for an active stage to drive. It would need to have a fairly stout output current capability and low output impedance.

If my guess is correct about the presence of the transformers, then for unbalanced output, theoretically the mini jack may actually be better because it skips the transformer. But, my RMAA tests of the 1/4" outputs in unbalanced mode shows excellent results anyway, and it's hard to imagine that the transformer is hurting performance, at least for those metrics that RMAA measures. It would be interesting to do an RMAA loopback run through the mini jack outputs and see what the results look like. I'll do that some time soon.
 
Jun 6, 2008 at 12:06 PM Post #18 of 50

amb

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Quote:

Originally Posted by grenert /img/forum/go_quote.gif
I completely agree that the stock wall wart is a joke (basically a cell phone charger), and replacement is definitely a great idea.


The little wallwart is a 5V switching supply. The digital stuff in the 0404 USB shouldn't be affected by the noise/quality of the power, and I am sure there is internal regulation for the analog stages (or the measured noise performance wouldn't be as good as it is). Nevertheless, it would be interesting to substitute the wallwart with a good, clean linear regulated supply. I had planned to build a σ11 PSU configured to 5V output as an upgrade for my Squeezebox 3 anyway, so this should be an good experiment.
 
Jun 7, 2008 at 9:02 PM Post #20 of 50

grenert

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Quote:

Originally Posted by amb /img/forum/go_quote.gif
The little wallwart is a 5V switching supply. The digital stuff in the 0404 USB shouldn't be affected by the noise/quality of the power, and I am sure there is internal regulation for the analog stages (or the measured noise performance wouldn't be as good as it is).


You know, based on your testing this makes sense, but I cannot recognize anything in the soundcard that looks like a voltage regulator. This is perhaps not saying much, given my inexperience. However, I definitely don't see anything that looks like voltage regulators I've seen in other equipment. Additionally, there is no capacitor larger than 220uF inside.
 
Jun 9, 2008 at 8:37 AM Post #23 of 50

foreverzer0

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Quote:

Originally Posted by ephrank /img/forum/go_quote.gif
foreverzer0, have you compared the sound quality of using the stock wall wart and the linear regulated? How big is the improvement upgrading the wall wart alone?


I don't know whether it's placebo or not, but to me it was rather subtle but it does seem smoother and faster, if not anything else. It's rather inexpensive and easy to implement anyhow.


Quote:

Originally Posted by grenert /img/forum/go_quote.gif
Well, I'm glad you like the end result, but I've opened up my own 0404 USB, and what I believe to be the stock headphone caps (the ones closest to the headphone out) are 220uF, not 22uF. 22uF is pretty small for headphone out decoupling, considering the relatively low impedance of most headphones.

Also, I think those five 47uF capacitors near the line out section serve as local power supply caps (someone who knows more about this stuff than I should probably confirm this). You'd probably do better with larger capacitance, low impedance caps like Panasonic FM/FC or Nichicon UHE/PW, rather than those gigantic Blackgates (although given their higher voltage, they probably have less impedance than the stock caps).

I completely agree that the stock wall wart is a joke (basically a cell phone charger), and replacement is definitely a great idea.



Sorry, I believe that was a typo if I said 22uF, the ones I have installed are direct replacement values so 220uF is right. If they were 22uF, those would be some rather huge 22uF caps!
biggrin.gif
 
Jun 12, 2008 at 6:01 PM Post #25 of 50

amb

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I ran RMAA loopback test of the 3.5mm mini jack output and added it to my RMAA results web page. It basically measured similarly to the main 1/4" phone jack outputs in unbalanced mode, except that the distortions are slightly higher, but the big loser is stereo crosstalk. I don't know why, but it might have something to do with the less robust 3.5mm connections.

Btw the internal photos don't seem to show any transformers, so my theory posted previously might be wrong. If I get a chance sometime in the future I'll open it up to have a good look.
 
Jun 19, 2008 at 3:16 PM Post #26 of 50

foreverzer0

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Quote:

Originally Posted by amb /img/forum/go_quote.gif
I ran RMAA loopback test of the 3.5mm mini jack output and added it to my RMAA results web page. It basically measured similarly to the main 1/4" phone jack outputs in unbalanced mode, except that the distortions are slightly higher, but the big loser is stereo crosstalk. I don't know why, but it might have something to do with the less robust 3.5mm connections.

Btw the internal photos don't seem to show any transformers, so my theory posted previously might be wrong. If I get a chance sometime in the future I'll open it up to have a good look.



They don't have transformers, but I hear they have multiplier circuits in the design, I don't know if that has anything to do it with it or not...
 
Jun 28, 2008 at 5:37 AM Post #27 of 50

PDOT

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I modded my E-MU0404Usb-LM4562MA-line out, LM4562MA+AD8066AR-headphones out. All the caps are Black Gates. The sound card sounds much more interesting: rich, detailed, not so sharp as it was. Bass response became much better. Thanks to foreverzer0.
 
Aug 4, 2008 at 1:46 AM Post #28 of 50

foreverzer0

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Quote:

Originally Posted by PDOT /img/forum/go_quote.gif
I modded my E-MU0404Usb-LM4562MA-line out, LM4562MA+AD8066AR-headphones out. All the caps are Black Gates. The sound card sounds much more interesting: rich, detailed, not so sharp as it was. Bass response became much better.


I was wondering which types and specification black gates did you use? and how did you use two different opamps for the headphones?
 
Aug 4, 2008 at 1:52 AM Post #29 of 50

foreverzer0

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Quote:

Originally Posted by grenert /img/forum/go_quote.gif
Well, I'm glad you like the end result, but I've opened up my own 0404 USB, and what I believe to be the stock headphone caps (the ones closest to the headphone out) are 220uF, not 22uF. 22uF is pretty small for headphone out decoupling, considering the relatively low impedance of most headphones.

Also, I think those five 47uF capacitors near the line out section serve as local power supply caps (someone who knows more about this stuff than I should probably confirm this). You'd probably do better with larger capacitance, low impedance caps like Panasonic FM/FC or Nichicon UHE/PW, rather than those gigantic Blackgates (although given their higher voltage, they probably have less impedance than the stock caps).

I completely agree that the stock wall wart is a joke (basically a cell phone charger), and replacement is definitely a great idea.



What capacitance are we talking about? I tried using 100uf types for those but they made it rather dark sounding... Are those Panny's or Nichicon's better spec'd than black gates?
 

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