been a while since i posted anything good, guess i might as well join in the fun. originally thought of running it with an external power supply altogether, but balanced out looks much more suitable, and less hassles.

the card is running entirely on super regulated 6V (more or less). all power is taken from the +12V rail, feeded into a C-R-C-R-C filter before feeded into a low noise regulator and dropped to exactly 6V. done the same thing for the -12V where it's regulated to -6V.
the whole Opamp and buffer section runs from this +6V and -6V rail, and the DAC section requires another regulation by a low noise BurrBrown DMOS REG102-5 and dropped to 5V. the whole DAC, ADC, ASRC, and DSP runs on this 5V rail. the DSP chip however requires another drop to 3.3V and 1.8V from the 5V.





bypassed most (if not all) of the original power supply scheme. hopefully the 6V drop cleans most of the ripples from the noisy switching power supply. the buffer is still there, but socketed and biased into Class A with low noise JFETs. the decoupling caps is replaced with Muse FineGolds. the final Opamp is also socketed and separated for both channel, now requiring 2 X single channel Opamp. also biased into Class A with low noise FJETs. each Opamp has its own tantalum bypass for both rail to ground.

bypassing the original power supply scheme for the card is a somewhat easy thing to do since there's only 3 voltage regulators on the card. solder and pull the input/output legs and leave it floating.

That's quite a heavy mod. Does it live yet? How does it sound?

^ the +12V and -12V is taken from the caps position near the analog D9 connector. the Opamp/buffer section is running from an unfiltered +12V and -12V directly from the mainboard rails. good in the sense that it could power just about any power hungry Opamp including the AD843 and OPA627, but there's uber minimum amount of filtering (close to none) for it.

originally, the DSP is running from 3.3V and 1.8V regulated from the mainboard's 5V rail. using either AMS1117-3.3 or ST Semiconductor's LD3.3 and LD1.8. the DAC, ADC, and the rest of the card are running from 5V regulated from the +12V by an L78M05.

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yeah it still lives. the output is somewhat better than my Class A EMU0404 (as in the sig). quite an improvement really. but the positive regulator gets somewhat hot even with the heatsink. i wonder just how much current drain that particular regulator had to deal with, taking that it's more or less powering the whole card by itself.

but nothing to worry i guess, since it has thermal shutdown.

you could sell that sucker probably for a few hundred..

Those mods just made me lean back and go "woah"

There must be a market for modded 0404s. I doubt most people here would want to attempt something like that. I must say you've got a lot of balls!

Wow, now there's some nice work. I'm wondering if you're getting any high frequency noise added due to the length of the power supply leads from the regulators? Maybe a couple of ferrite beads on the DC supply leads wouldn't hurt?

Has anyone else considered removing the DB-9? The DB-9 connector strikes me as good for 9600 baud serial, but not for audio.

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thanks. i'll take that a compliment.
tried the implementation quite a number of times using 9V batteries to make sure the 5V don't give out anything above 5V. because if it did, then bye-bye DAC, bye-bye ADC and bye-bye EMU0404.

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i wouldn't worry too much about that. mainly because there's lots of capacitors to buffer the charge. but i've never encountered any high frequency noise before, so i can't really tell. how does it sounds like?

i still need the input jacks, the optical and coax connection. and removing the DB9 might lower the resale value of the card.

Inside a typical computer case is pretty RF-heavy, so it's hard to say what you can pick up with a random length wire in there. My curiosity about the induced noise stems from a different project I was working on -- off-board linear regulator (12v to 5v) for an embedded GPS. The GPS would lock fine in the shop, but not in my truck. +5 looked fine on my voltmeter. When I took the oscilloscope out to the truck, I saw there was a (approximately) 1MHz oscillation on my leads from the regulator to the GPS. Some twisting and additional bypass caps cleared that up.

If you still need the inputs, or more than approximately 5 RCA jacks on there, I guess you might not be able to replace the edge bracket. I would have used the WBTs on mine, but they're too wide for the PC case. The Cardas jacks are a bit smaller.

Question!
What is the purpose of the output buffers? and why should we bypass them? Shouldn't we just need to bypass the output capacitors to achieve the desired affect?

Thanks!

The final set (at a minimum) converts the balanced output from the DAC to non-balanced output suitable for most consumer uses. I've completely omitted the final opamps on one card that I've modified and route the + and - outputs (and ground) to a pair of Neutrik XLRs for use with some powered monitors needing balanced input. Works just fine. Levels are reasonable. Sounds good.

I could be wrong, but the set after the DAC may be just to present a known load to the DAC. In some cases, shorting the output of an op-amp will cause no damage. (Or would damage only a $7 part.) I have spare op-amps in the junkbox, but no spare DACs of that type.