[blip]

Okay, probably a stupid question but I'm building a CMoy (or at least I will be as soon as I get some spare time) and I had a strange thought about powering it. I'm planning to us it mostly as a headphone amplifier for my computer and thus I was wondering if I could actually power the CMoy off of my computers PSU. It would reduce the cord confusion and give me decent voltage (12v divided into +/- 6v).

I wonder though if the PSU would be too noisy or if drain from other devices would introduce fluctuations. What do you think?

 

[mlchang]

I'm sure it could be done. It's a switching power supply so it could be noisy. How stable is the 12V rail on your PSU? How many devices are you running in your PC?

 

[Dreamslacker]

Quote:

Originally posted by blip Okay, probably a stupid question but I'm building a CMoy (or at least I will be as soon as I get some spare time) and I had a strange thought about powering it. I'm planning to us it mostly as a headphone amplifier for my computer and thus I was wondering if I could actually power the CMoy off of my computers PSU. It would reduce the cord confusion and give me decent voltage (12v divided into +/- 6v). I wonder though if the PSU would be too noisy or if drain from other devices would introduce fluctuations. What do you think?

Don't bother.

The ground signal from your soundcard is tied with the ground on the PSU. Hence, you can't build a splitter to be powered off the PSU and use the amp for the soundcard at the same time.

The power isn't that good either (unless you have nothing else running off the PSU). You'll get occasional clicks & pops.. Maybe humming on the amp. Any cheap AC --> DC adaptor will do the job fine.

 

[blip]

Dreamslacker -> Ahhh... good save Dreamslacker. I hadn't thought of that. Thanks a lot.

Michang -> The 12v rail varies considerably depending on the quality of the PSU. Mine is a pretty decent one (Enermax) so it generally stays stable at 11.95v. Cheaper ones tend to have higher variances depending on how much is connected to it.

While I'm thinking about it, how good/bad do you think a PC PSU would be at powering a CMoy or other small audio gear if you rigged it up for use outside of the computer? (A simple task of shorting two cables) I've got some old ones laying around that might come in handy for this type of thing. Of course, if they were used external then they would be dedicated to the device and thus wouldn't have quite as much of a noise issue... still they aren't known for being the quietest in the world... What do you think?

(Hmmm... If i didn't have to power a mobo with it, I could probably use the PSU's -12v line and eliminate the rail-splitter.... Interesting.)

 

[Dreamslacker]

Quote:

Originally posted by blip Dreamslacker -> Ahhh... good save Dreamslacker. I hadn't thought of that. Thanks a lot. Michang -> The 12v rail varies considerably depending on the quality of the PSU. Mine is a pretty decent one (Enermax) so it generally stays stable at 11.95v. Cheaper ones tend to have higher variances depending on how much is connected to it. While I'm thinking about it, how good/bad do you think a PC PSU would be at powering a CMoy or other small audio gear if you rigged it up for use outside of the computer? (A simple task of shorting two cables) I've got some old ones laying around that might come in handy for this type of thing. Of course, if they were used external then they would be dedicated to the device and thus wouldn't have quite as much of a noise issue... still they aren't known for being the quietest in the world... What do you think? (Hmmm... If i didn't have to power a mobo with it, I could probably use the PSU's -12v line and eliminate the rail-splitter.... Interesting.)

You could rig up an external PSU for the job. It'll do the job fine but you have to:

1) Watch the voltage lines. Some of the PSU's don't regulate the line at very low loads (usually under 800mA) and you can get a significantly higher voltage than 12v.

2) Sepearate the earth from the ground in the PSU.

 

[mlchang]

Quote:

Originally posted by Dreamslacker 1) Watch the voltage lines. Some of the PSU's don't regulate the line at very low loads (usually under 800mA) and you can get a significantly higher voltage than 12v.

I hadn't even thought of that ground problem you mentioned earlier, good one. But this above statement is true. Although cmoys, depending on their construction (caps used, etc) should be able to take higher voltages...at least the op-amp should be able to. I still think it will be noisy though.

 

[jasong]

<2) Sepearate the earth from the ground in the PSU.>

How would you go about doing this? I have a PSU apart on the bench but I have no idea how to clean it up for possible cmoy duty...

 

[Dreamslacker]

Quote:

Originally posted by jasong <2) Sepearate the earth from the ground in the PSU.> How would you go about doing this? I have a PSU apart on the bench but I have no idea how to clean it up for possible cmoy duty...

Open it up. Isolate (using grommets or otherwise) the PCB from the screws and metal parts of the PSU case.

 

[blip]

Quote:

Originally posted by Dreamslacker Open it up. Isolate (using grommets or otherwise) the PCB from the screws and metal parts of the PSU case.

Hmmm... Sounds easy enough... just out of curiousity, why do you need to do this? I'm a newbie to this stuff so I'm still trying to learn the theory behind things.

It sounds like an interesting idea.... Next time that a spare PSU comes accross my desk, I'll definitely give it a shot.

 

[Dreamslacker]

Quote:

Originally posted by blip Hmmm... Sounds easy enough... just out of curiousity, why do you need to do this? I'm a newbie to this stuff so I'm still trying to learn the theory behind things. It sounds like an interesting idea.... Next time that a spare PSU comes accross my desk, I'll definitely give it a shot.

Ok..

In a PC PSU (I'm really more of a PC hobbyist so I know a little more about PC PSU's), the ground is usually tied to the casing. ie. The EARTH wire.

Now. If you don't isolate the PCB from the Earth (casing), then both PSU's (external and PC) will essentially have the same ground. Which would be the same as trying to power your amp from the PC's PSU.

 

[blip]

Ahhh.... I get it now... thanks.