Anyone have experience with building amps into computers?

[karl k]

It's been awhile since I visited here and even longer since I did anything audio but the bug has bitten me again and here I am with some ideas and questions.
I've built a couple of computers in the last couple of years with the intent of acquiring as much knowledge as I can about what is available in the industry in making an HTPC. The biggest issues I've had were trying to integrate an on board amp set for all the outputs of an audio card AND being able to plug my HD satellite dish into the computer. The latter is about to solve itself in the form of a new Auzentech audio card with HDMI input and output. The former however is a bit more tricky as I have no experience with building amps or using the amp modules available. I do think that it is possible to from a heat standpoint with the use of class D amps but most are well out of my price range and never having tried any of them it would be hard to tell whether these assembled "kits" really sound as good as the specs say.
I guess my first question is...
Has anyone actually done something like this and how successful was it?
If so, how much did it cost?
Who would have amp and power supply modules for such a project?
The ones I'm looking at now are as follows...
http://www.classd.ltd.uk/Datasheets/Specifications%20for%20the%20CD%20NX's.pdf
http://www.cadaudio.dk/d150c6a.pdf
The former is a single channel module that would have to be reproduced for each output of the sound card and the latter is a 6 channel on one board. Both would need power supplies added but it looks like no matter what either could fit in a small enough space within a normal ATX mid tower case with the rest of the computer components.
Anyone have experience with either of these companies or the concept in general?

[Kevio]

It looks like the single channel amps will need heat sinks. The specifications on the 6-channel amp are more believable. What do you have in mind as far as a power supply is concerned?

[Feanor]

It's been awhile since I visited here and even longer since I did anything audio but the bug has bitten me again and here I am with some ideas and questions.
I've built a couple of computers in the last couple of years with the intent of acquiring as much knowledge as I can about what is available in the industry in making an HTPC. The biggest issues I've had were trying to integrate an on board amp set for all the outputs of an audio card AND being able to plug my HD satellite dish into the computer. ...

Sounds like an interesting project and challenge -- I wish I had the technical expertise to tackle something like that. In fact I'm intimidated by the othewise appealing possibility of sticking a complete DAC kit with power supply and transformer into a box.

But practically speaking I don't see any advantage, and maybe some disadvantages, to actually putting the amplier inside the computer. That is, it would seem to avoid, for example, EMI/RFI problems putting the amp in a separate box in the conventional manner. Would you use the computer's power supply to power the amp?? Most audiophiles would be appalled by the concept.

[karl k]

What do you have in mind as far as a power supply is concerned?

Would you use the computer's power supply to power the amp?? Most audiophiles would be appalled by the concept.

Well, I'm not planning on using the same computer power supply as the rail voltage isn't near what it would need to be. No... I'm trying to contact the suppliers of the amp modules to see what they recommend. There are all kinds of concerns about noise and compatibility as well as space. I can't fit a power supply that depends on a toroid coil so I will need a transformerless supply... either switching or linear... IDK which yet. CAD Audio offers power supplies for their other amps but don't have any specific listing for the multichannel I'm looking at. If the Class D amp is as efficient as some of the others(85%-90%), then the supply shouldn't need to be bigger than about 800wts to get a reasonably clean 100wts per channel.

But practically speaking I don't see any advantage

Well, the advantage is not needing to have a receiver any longer. With the right parts, software, and an on board amp, it will literally take the place of everything I have in AV equipment and be more versitile at the same time. Additionally, the ability to market either the equipment or the service to install it in existing units would be more appealing to Average Joe.

It looks like the single channel amps will need heat sinks

Yes but if they are anything like the other class D amps I've seen on their website and others, then the sink is pretty small and w/o fins. Additionally, the case fans I have should assist in keeping things cool.

[qinjuehang]

I'd say use a voltage multiplier to boost the compter PSU 12V rail to 48V or 24V for the second one. Really, a computer PSU is a rather precise regulated power supply, don't waste it. Also, do attach a small heatsink, because the devices will probably have higher distortion and lower SNR if the temp goes too high, even if the devices are rated to handle the temperatures. I have routed things in my computer, and made a PWM fan controller before, but that's rather off topic...also, most high-end audio cards do have a EMI shield. It is not hard, a simple metal shield, ie. faraday's cage should suffice. Also, for home theater setups, you might want to go with a horizontal case. I suggest a SINGLE RAIL power supply, because a high wattage triple rail or quad might not have enough juice on one rail, and the CPU will be wasting a lot of juice, by dedicating one rail to itself.