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Old 30th January 2013, 07:11 PM   #71
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Quote:
Originally Posted by regiregi22 View Post
Has it ever worked to you or never had?
good question. duno. I never used it before. I use EMU 0404 USB for measurement through analog output only.... pity. good thing. I'd like to repair it.
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Last edited by Artmaster; 30th January 2013 at 07:14 PM.
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Old 31st January 2013, 03:11 PM   #72
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Be sure to check SPDIF is selected in the main/spdif/off button...
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Old 31st January 2013, 05:54 PM   #73
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Quote:
Originally Posted by regiregi22 View Post
Be sure to check SPDIF is selected in the main/spdif/off button...
done. not working. need circuit diagramm. people - heeeeeeelp
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Old 8th April 2013, 09:10 PM   #74
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Default Emu 0404 USB modifications

So at last I found a *second* cheap (used) Emu 0404 USB and I can start something I was waiting for: I wanted to modify the first unit I've had for a while, and that I use mostly as a USB DAC out of a "music server", but I thought that to really check the effects of different things, I needed a stock unit to use for reference.

So I have started looking at what is what, and I am updating the E-MU 0404 USB mod wiki with my findings.

Just "diagrams" and description of the unit, for the moment.

I am posting in this thread because it seems the most recent specifically dedicated to the subject. (Sorry Artmaster, I will not really go into the spdif part... hope you solved your problem.)
It's probably an old subject, but who knows, maybe somebody is still interested, and anyway that keeps me busy while waiting for a certain long-pending group-buy for another DAC...

Enjoy.

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Old 12th April 2013, 10:04 PM   #75
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Wow!
I started testing.

The setup:
MacBook Air playing flac on Songbird.
USB to the Emu 0404, line outputs (not balanced) into my headphone amplifier (JLH "circuit 2") into AKG K240 Monitor.

I couldn't really put together an A-B switch, so in fact I have to disconnect and reconnect every time. I also don't have all my equipment here, so the volume level matching between the "DUT" and "reference" is not really done, and this can fool comparisons, I know.

The modification I tested is one that's extremely easy to do:
Replace the supply to the op-amps of the output stage.
You only need to remove two resistors, and solder three wires into easy places (look here).
Well, you also need a bipolar supply...
I just connected two 9V batteries.

My conclusion is that the result is well worth the mod.
I was careful not to be fooled by a volume difference (but +/-9V intead of +/-6V shouldn't change the gain of the op-amps, right?) and I must say that the "clean" supply is distinctly audibly better:
the instruments can be better distinguished, there's "space" and width, and more dynamics. Not "night and day" (the stock unit is already decent, I think) but certainly an improvement.

I used Mahler's 6th by the SF Symphony conducted by Tilson Thomas, in 24bit 96KHz. I have heard this symphony live in concert halls too (that's still a whole other planet...)

I think this is a nice start.


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Old 14th April 2013, 04:02 PM   #76
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Tried another easy one:
Pick the output before the volume potentiometer, skipping output buffer and muting.
This time I put together a sort-of A-B switch to be more comfortable.

Result: Cannot hear a difference.

I had put back the stock (noisy and unprecise) supply to the opams, though, to test one thing at the time.

So this could mean one of the following:
- The difference, if any, is masked by the bad opamp supply
- The difference, if any, is less than my system's and my ear's discriminating power
- The "signal path" is something more complicated than we think, and the fact that the downstream chain was still connected, makes its "effect" stay (I just connected before the pot, without interrupting the rest of the connection).

In fact, I was almost expecting that without the output buffer it would sound worse, since the way through my A-B switch makes double length of interconnects...


So for now I would conclude that removing the pot or muting transistors is probably not the first modification to do...


Next: replace coupling caps at the outputs of the DAC.


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Old 14th April 2013, 10:03 PM   #77
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Replaced the 47uF coupling caps (C80, C81, C82, C83) with 56uF Sanyo OsCons. These were the "best" I have around.

Result?
I think I can hear an improvement in symphonic, the sound is "wider", the strings nicer, more precise and "silky-creamy". Not huge difference, though.
With baroque the difference is less pronounced. Maybe attacks are more precise and decays a tad longer...
With rock I cannot really hear a difference.

(Comparing to my other unit, kept 100% original. So here the only difference are the coupling caps, all previous changes had been undone).


I guess that now I'll build two dual supplies for the opamps, put that in both units and proceed from there...


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Old 14th April 2013, 11:22 PM   #78
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Hi
did you check how the ADC quality of this unit ? I thought of using this for recording to create hi resolution audio file from good analog source?
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Old 15th April 2013, 07:32 PM   #79
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Hi kannan,
sorry, I didn't trace much on the input part, and I know even less about ADCs than I know about DACs...

There are several opamps near the input connectors, and they are probably used as input buffers of some sort. I would expect that they also benefit from a cleaner supply (remember: both the positive and negative supplies to the opamps are obtained from dc-dc converters that to build 6V from the 5V of the supply, use high frequency switching of some sort; the negative supply seems to be especially "noisy").

Trace the circuit starting from pins 4 and 8 of the opamps, and see if there is an easy place where the supply rails are "picked" (like the two 0ohm resistors R149 and R157 of the DAC output stage). In that lucky case, you can cut this connection and use it for a better supply; if there are local reservoir caps, that's an easier soldering point.
Looking at the board, candidates could be R134, R380, C61, C63.

But I don't know how the phantom supply (48V) gets in the game...
Make sure it's off, unless you know how to handle that "detail"


I am using this soundcard also for the input, and digitizing vynil at high resolution to see what it does is also in my thousand-plans list.
I have been recording instruments, but for "musicians" high fidelity seems to be less of an issue... (it's not like I am really a musician anyway...)

For the moment I'll concentrate on the output part, but who knows, maybe later on.


Cheers,
pilli

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Last edited by pilli; 15th April 2013 at 07:37 PM. Reason: forgot one piece...
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Old 17th April 2013, 08:17 AM   #80
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Quote:
Originally Posted by pilli View Post
Next: replace coupling caps at the outputs of the DAC.
Done that, and not just those but all 'lyics of the PCB. Nothing fancy, I just used panny FC that at least are long life and well regarded soundwise.

I don't know what to do with the volume pot. After near 3 years it has started to fail, sometimes it makes loud crack and pops on the speaker when you turn it up/down. Meanwhile I don't use it but instead a preamplifier (buffer) after the emu. Which in turn I wouldn't need, because it adds no gain, just volume controll, it's a unity gain buffer.

Haven't tried yet a better psu rather than the cell phone charger though...
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