E-MU 0404 USB Modification?

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I have tested all the output stage with CS4397-98 chips.

The Solid stade is not very good as sound, too digital.

The best is pure vacuum tubes but it is the more expensive.

The transformers solution is fast and good but it can lost some little details also if the sound is the more natural.
 
Does anyone know about the capacitors on the input side of this device? I see there is a trio of large 47 uF, 63V electrolytics on each input channel and a smaller fourth capacitor near them. I suspect the large electrolytics have something to do with phantom power blocking. As I am mainly interested in the line input, I would like to re-cap or bypass any extraneous caps on the input side.

Also, I had the headphone output crap out on me during a live concert recording (not a good time for the headphone output to crap out). The audio was "static-y" and full of crackle. I replaced the headphone caps with Nichicons and the problem has not reoccurred.
 
I have seen high output noise on my scope too from my Emu tracker. Even sine waves produced by it are obviously dirty VS my analogue old generator on the scope's screen. But when looped with measurement software, it ignores it, and it compares very well for THD readings and SNR of DUT VS normal measurement equipment. A guy in a local forum made an extensive analysis and comparison with his HP gear, and beyond square wave generation that was ringing, he found the EMU very useful when looped with measurement software, but not as a stand alone generator. Especially not beyond 48kHz sampling rate. Big noise starts at 35kHz and he made a filter. That helped if there is need for an AF only capable stand alone generator and it must be the EMU, for economic and utilization reasons if its already in hand. They also proposed buffered attenuation for its input so it can be used on measuring high voltage signals too.

are there any 0404 mods that are known to specifically improve the sound card when being used in loop mode with RMAA (SNR, THD, etc.)?
 

iko

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It doesn't do anything, and it shouldn't. In goes +5VDC which then gets converted in several parts of the board to various positive and negative voltages. I've provided details elsewhere (see the wiki) about each place where it gets converted, and by what IC. Those converters introduce all sort of high frequency garbage into the rest of the circuit.
 
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For 1KHz he does show higher distortion. Tho it isn't awful and should not be audible.

But the real test is at >1KHz. That's often where opamp output circuits start to get nasty. Try 3KHz and its octaves. There may be some real differences. Ditto with multi-tone and IMD.
 
And past 10kHz... you don't hear the harmonics anymore.
I can't tell I have heard the effect but the harmonics above audibility do create an audible effect.

Think about the 19kHz + 20kHz intermodulation test.
These two frequencies are sufficiently high enough that most listeners cannot hear the fundamentals. I'll bet most can hear the in band distortions readily.
 
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