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DIY DAC/amp, drive bay

post #1 of 15
2/27/10 at 10:11am
Thread Starter 
I'm thinking about putting a DIY DAC/amp into a drive bay, like a Scythe Kama or those sound controllers that come with some sound cards, and powered from a USB header. But I don't really know what I should gut to use as a chassis. I was thinking of using an emptied out optical drive but then I'd have to make a front panel for it. I could probably cut up some ABS panels and use that. Anyone have any better ideas?
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post #2 of 15
2/27/10 at 11:44am
Couple of ideas for you,
5.25" Lian Li Black Bay Cover - FrozenCPU.com

Scythe KC01-ABK-5 Kama Cabinet 5.25" Storage Box - Black Aluminum Products Model: KC01-ABK-5 [KC01-ABK-5] : Performance-PCs.com, ... sleeve it and they will come
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post #3 of 15
2/27/10 at 12:23pm
I'd go with one of those locking, removable hard drive caddies, myself, because they're cheap, and the metal covers would hopefully provide some shielding in the (electrically) noisy innards of a computer.

Why would you need to make a front panel for a gutted optical drive? If you pick the right one, it will come with a perfectly unobtrusive front panel... and even a hole for a headphone jack.
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post #4 of 15
2/28/10 at 1:41am
Thread Starter 
That cabinet is just right actually, maybe with a few screw holes drilled along the side. Thanks a lot!
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post #5 of 15
2/28/10 at 2:12am
Of course if it's internal, you could just power it from the +5 or +12 from a spare molex connector you undoubtedly have.

I'd also recommend a hot swap drivebay. The size is a little smaller, but since you can remove it, it makes it easy to remove and work on. Also, if it is metal, you'll have some shielding for it.
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post #6 of 15
2/28/10 at 3:11am
If you use internal power, I would recommend using the 12V and regulating down to 5V with a nice big cap to filter it. Those internal supplies are horribly noisy and usually not very exact (5V can often be 4.86V, etc), especially under load. Shielding would also be a very good idea.
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post #7 of 15
2/28/10 at 5:45am
Quote:
Originally Posted by Juaquin View Post
If you use internal power, I would recommend using the 12V and regulating down to 5V with a nice big cap to filter it.
An inductor, perhaps a ferrite bead with a few turns, might be a good idea too.
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post #8 of 15
2/28/10 at 6:30am
Agreed - I do a lot of PC building / modding, and even high-end supplies like my 850W model have very dirty power (by audio standards).

Personally I wouldn't put any hi-fi equipment inside my rig because of all the stray EMF, but I'm certainly not going to stop anyone from trying! Definitely want to see how this turns out.
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post #9 of 15
2/28/10 at 6:55am
An interesting idea. Considering the sound you can get from a portable DAC/amp, what could you do in the space of a 5.25" bay?

Power's not a problem, I think. You could easily get 12-24 volts, and amperage isn't a problem. You'd need to filter it, for sure.

Hmm. If you tried hard enough, it looks like you could fit in a Gamma 1, a filtering board, and a mini^3 with room to spare for shielding.
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post #10 of 15
2/28/10 at 8:18am
Thread Starter 
If I wanted to skip the DAC and just use my sound card output, can you guys think of any suitable amp designs that'd fit in a drive bay? I could always try building a DAC in a second bay later.

And thanks for all the advice regarding the power!

EDIT: Also another thing I'm curious about but I guess it depends a lot on the particular amp design; will I have any grounding issues with the PC case?
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post #11 of 15
2/28/10 at 11:22am
What sound card are you using? Some of them are terrible.
There are some very small DACs out there.
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post #12 of 15
2/28/10 at 1:10pm
Quote:
Originally Posted by jamesbobo007 View Post
Thanks for posting the link to the drive bay covers. My computer has had an ugly hole in its face for YEARS after I realized I only needed one CD drive.... No more!
Quote:
Originally Posted by Oya? View Post
EDIT: Also another thing I'm curious about but I guess it depends a lot on the particular amp design; will I have any grounding issues with the PC case?
Good thinking and looking out for what can become a VERY real problem.

I learned about this one the expensive way with an amp with "virtual" ground that I wanted to run off of the +12V line in my computer while grounding it to "real ground" at my soundcard. Virtual ground is inherently several volts away from ground - all grounds are not created equal! and both my soundcard and amp bit it.

The comment was made to regulate down to 5V, I would say 9V. 9V gives enough voltage drop for most regulators to work with off of a 12V supply, and buys you a little more room for the amp to work under.

As for stuff you could build in a drivebay:
If you dont need much gain an amp like the szekers could easily be built on a 9V supply.

People have built MANY Comy type amps with 9V supplies. Be careful with that virtual ground! You may be better off thinking up a way to cap couple the inputs & outputs of the circuit, and float the opamp while having the output at "real ground" Its a bit of work, but much better than what happens if you screw up a Virtual ground.

There are probably a few more. Check them out. Most things that can run with a single 9V cell could be made to work.
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post #13 of 15
3/1/10 at 12:51am
A szekeres as a buffer for your sound card output is a good idea. If you decide to go with the 9v option, just make sure you have enough headroom, as szekeres amps work best at 12v or higher. You could try and filter the 12v from the molex connector and see if you can get rid of enough noise.

If your sound card doesn't have enough gain, you could make a cmoy like circuit with a virtual ground, and decouple it at the input and output to the szekeres buffer stage.


Something that i have been thinking a little about is making a szekeres VE derivative, where a 3rd channel is set up as the ground output for the headphone, which eliminates the output capacitors and provides some noise rejection. But you have to modify the ground channel so it's not connected to the ground of your pc, but the virtual ground that you would use for the cmoy gain stage.
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post #14 of 15
3/1/10 at 5:53am
Thread Starter 
I think I'll give the Szekeres a try with 9V. Or maybe use a really efficient regulator which doesn't shave off too much. How should I go about modifying the grounding scheme of the design on the HeadWize page to make it work inside my PC?

Quote:
Originally Posted by AndrewFischer View Post
What sound card are you using? Some of them are terrible.
There are some very small DACs out there.
I'm actually gonna use the output of my integrated sound since it's pretty clean.
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post #15 of 15
3/1/10 at 6:29am
Might I suggest an apheared47 amp? It'll run nicely of the regulated 9v supply and provide some 70 mA of output current (with OPA2134).

You could build it with a Sijosae discrete spliter to avoid using TLE2426 + BUF634. But you'd certainly need to watch your grounding so as to avoid connecting the virtual ground to the case.

cheers!
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