amp for pc? awesome? or not awesome?

Mojo JoJo

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i've never seen anything like that. it looks like its for cd-rom/dvd analog audio connection only.
 

atarione

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i saw the cd audio connectors but they show it hooked up to the m/b audio out with a 3.5mm cable

so i **think it would be like hooking your pc to an external amp with a 3.5mm cable right?
 

Mojo JoJo

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If you look closely at the pictures on the card, they show audio out connectors. kind of strange.

maybe something like this might be better.. just a recommendation. I've never had a Muse Amp.
 
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atarione

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i did see it is labled audio out... but the way it is hooked up it almost has to be in?

plus it wouldn't make any sense unless it is actually in?

i don't know... it does in fact make me a bit nervous to even consider trying it.


i'm also wondering about the potential for noise from being inside the case and all.. the zero foot print would be nice in my case not much room on my desk
 

Snufykat

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i did see it is labled audio out... but the way it is hooked up it almost has to be in?

plus it wouldn't make any sense unless it is actually in?

i don't know... it does in fact make me a bit nervous to even consider trying it.


i'm also wondering about the potential for noise from being inside the case and all.. the zero foot print would be nice in my case not much room on my desk

Higher potential for problems from using the pc power supply.
 

dustNbone

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There isn't really anything differentiating a PC power supply from any other switching power supply, which is what you'll get with most standalone amps in the lower price range anyway. Any decent amp will have proper isolation from it's power supply, no audible noise should get through. I have my PCs sound card connected to some very sensitive output gear, and there is no audible noise coming through to it's outputs. There is no reason I see not to use your PCs supply for a Class T amp.

Also, the 3.5mm jack on the back is a stereo input, the banana sockets are outputs. I don't see anything wrong offhand with this unit, different for sure but a tidy way to package a small amp in your PC I guess.
 

grimster

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There isn't really anything differentiating a PC power supply from any other switching power supply, which is what you'll get with most standalone amps in the lower price range anyway. Any decent amp will have proper isolation from it's power supply, no audible noise should get through. I have my PCs sound card connected to some very sensitive output gear, and there is no audible noise coming through to it's outputs. There is no reason I see not to use your PCs supply for a Class T amp.

Also, the 3.5mm jack on the back is a stereo input, the banana sockets are outputs. I don't see anything wrong offhand with this unit, different for sure but a tidy way to package a small amp in your PC I guess.

Thank you for being a force in the side of sanity. People who hear audible noise coming through from their computers need to address it. It could be something as stupid as a bad ground between the computer and speakers/amp, and not actually anything to do with the computer, itself. There are not radio waves just flying around inside of a computer like some will have you to believe. Power supply noise? That's what capacitors are for, but there still shouldn't be any noise coming from the power supply. Motherboards now condition power on their own for the CPU, RAM, etc. so noise shouldn't be created in the power supply lines anymore. I've only ever had noise from onboard sound and generic other parts like a decade ago.

I'd say go for that amp if it really interests you. It's not expensive. And if you go with it, let us know how it goes.
 

Fenris_Ulf

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There isn't really anything differentiating a PC power supply from any other switching power supply, which is what you'll get with most standalone amps in the lower price range anyway. Any decent amp will have proper isolation from it's power supply, no audible noise should get through. I have my PCs sound card connected to some very sensitive output gear, and there is no audible noise coming through to it's outputs. There is no reason I see not to use your PCs supply for a Class T amp.

Also, the 3.5mm jack on the back is a stereo input, the banana sockets are outputs. I don't see anything wrong offhand with this unit, different for sure but a tidy way to package a small amp in your PC I guess.

Not true. I've built amps based on the LM4950 and integrated them into a PC. (See: http://hardforum.com/showthread.php?t=1322687) Even with a PSRR of 70 dB (which means it only has 1/10,000,000 the noise of the power supply on the output) there was still significant noise that varied based on what the computer was doing. I tried 20,000 uF of capacitance, RC filters, decoupling caps, etc. Nothing worked. Eventually I gave up and switched to a cheap 12v wall wart - suddenly there was no noise, hiss, or interference. There is too much EMF feedback on the 12v line of the PC to make it quiet. Maybe if you used a DC-DC converter to isolate the two it would work better. Maybe a Tripath might work better. Maybe you'll be lucky and have a mobo with little to no back EMF (unlikely, I've never experienced it). But personally, I've given up on using the computer's power supply to directly power an amplifier.
 

grimster

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You never mentioned trying a different internal power supply. How is it that most people simply don't have problems?
 

Procyon12

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You never mentioned trying a different internal power supply. How is it that most people simply don't have problems?

i wasnt aware the most people power amplifiers with an pc power supply.
you know considering he would have to go to ebay and order from China to get something like this, i think that would be testament to how few people actually do this.
 

grimster

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I've powered amps with computer power supplies before without problem, for using car subwoofers with a home theater receiver. You don't hear basically anyone with sound cards with headphone amps bitching about noise, either. Even back in the day my one Sound Blaster had an amp to power some low-power computer speakers. No noise there.
 

Procyon12

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I've powered amps with computer power supplies before without problem, for using car subwoofers with a home theater receiver.

huh? i think you need to learn how an amplifier works, and what it means to be a power supply for an amplifier.

just because your your reciever recieves electricity from a PC power supply, doesnt mean that the PC power supply is the amplifiers power supply.

You don't hear basically anyone with sound cards with headphone amps bitching about noise, either. Even back in the day my one Sound Blaster had an amp to power some low-power computer speakers. No noise there.

ditto.
 

grimster

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Please read my previous post before you make such statements. I powered the AMP with a computer power supply. The amplifiers I've used are those people use for subs in their cars. It's the exact setup you would find in a car, but powered with a PC power supply, and it has a signal fed from a home theater receiver. The receiver only delivered a line-level audio signal over a coaxial cable. I've done it plenty of times.
 

Procyon12

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when the seller of the product thinks you should use an external power supply, that might be indicitive of something.

Keep in mind! Do not try to use the same power line with the hard disk, CD-ROM, or it may be introduced of interference noise!
Because of a lot of interference inside the computer, there may be interference noise, which is normal. If you mind of this, please apply the external power!
 

grimster

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None of those things will introduce noise. They post these warnings not knowing how any of those devices work, assuming that because a brushed motor in some home appliance or tool creates bad EMI that anything else in the world with a motor will do the same. They're just covering their ass so if someone puts that card into a computer with crap components and it makes noise, they reserve the right to not issue a refund based on that.
 

Procyon12

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Please read my previous post before you make such statements. I powered the AMP with a computer power supply. The amplifiers I've used are those people use for subs in their cars. It's the exact setup you would find in a car, but powered with a PC power supply, and it has a signal fed from a home theater receiver. The receiver only delivered a line-level audio signal over a coaxial cable. I've done it plenty of times.

ok. take my post and replace 'reciver' with 'subwoofer amplifier'

same thing.
 

Procyon12

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OK, will do:



Yeah, that makes sense :rolleyes:

you must have forgotten step one:
i think you need to learn how an amplifier works, and what it means to be a power supply for an amplifier.

if you dont mind can you give me a diagram of how you connected your power supply to your subwoofer amplifier?
 

grimster

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Why? Do you think I don't know how to connect positive to positive and negative to negative? That's really as simple as it is, plus a huge capacitor in parallel, simply to only deal with huge thumps in sound to not make the power supply shut off to protect itself.
 

Fenris_Ulf

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I've been building HTPCs for about 12 years and building amps and speakers for about a decade. In that time I've tried alot of solutions to integrate an amp into the computer using the same power supply and have come to the conclusion that it's just a bad idea. Poor motherboard layouts will leak noise into the onboard audio. Other motherboards will have back-EMF from (usually) video or the CPU VRMs. Sometimes you have a ground loop using the same power supply for your amp as your sound, and the ATX spec frankly has too much allowable ripple. 120mv is what's allowed on the 12v rail, and that's usually tested with a linear, benign load resistor rather than a reactive load. 120mv leaked into the normally 2v line out signal would be incredibly noisy, but that would be worst case. Even a few mv injected into the signal will be quite audible, and even more so as the overall quality of your audio system increases.
 

grimster

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Well then you have some really crappy components. Sorry, but most people just don't have problems with this.
 

Fenris_Ulf

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I've powered amps with computer power supplies before without problem, for using car subwoofers with a home theater receiver. You don't hear basically anyone with sound cards with headphone amps bitching about noise, either. Even back in the day my one Sound Blaster had an amp to power some low-power computer speakers. No noise there.

OK. Now try hooking up a computer to the power supply in addition to the amp. And try full range speakers instead of a highly filtered suwoofer. You wouldn't hear much of the 2KHz noise through the filters of the sub amp and the significantly reduced response of a woofer at those high of frequencies. Oh, and by the way, a car amp uses a high frequency (well above audible range) DC-DC converter which effectively filters out alot of noise. So there's really no comparison.

Headphones don't have a ground loop or an active gain stage, and yes, I can hear noise from some onboard sound cards with good headphones. Yes, the Soudblasters did. But by today's standards they were low-fi and computers were quite different then. Back at that time most of the power for the computer was drawn from the 5v line and the 12v line was relatively clean, so it was easier to filter out the noise, especially with both the DAC and amp next to each other physically. There's a reason they stopped doing it.
 

grimster

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if you dont mind can you give me a diagram of how you connected your power supply to your subwoofer amplifier?

Code:
     +-----------------+                    +-----------------+
     |                 |                    |                 |
-----| ~           12v+|----o----------o----| 12v+ in         |------+
     |                 |    |          |    |            A    |     _|_ /|
 A/C |        PSU      |   === Cap.    +----| Remote     M    |    |___| |  <-- Speaker
     |                 |    |               |            P    |      |  \|
-----| Neutral     GND |----o---------------| GND             |------+
     |                 |    |               |                 |
     |      ATX pin 16 |----+               +-----------------+
     +-----------------+
 

grimster

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And you don't think the switching in a power supply is above audible range? You should really stop acting like the idea is the problem and start looking into not buying crappy components. Why would I hook a computer to that supply also? That's retarded. It still doesn't change the fact that plenty of people have sound cards with amps in them and don't have audible noise. A ground loop issue is not the fault of the computer or its power supply, whatsoever. Stop spreading your false garbage. Just because an old Sound Blaster was "lo-fi" in your mind doesn't change the fact that there was no noise coming from it, in the era of noisy everything. Power inside of a computer is now cleaner than ever...the opposite of what you claim.
 

Fenris_Ulf

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Hmmm, let me do about 30 seconds of research for you. Can we agree to use [H]ardOCP as a reliable testing standard? OK, look at the latest [H] PSU review. Can we assume that the OCZ 650 represents a typical modern PSU? Check out the DC quality page. Here, I'll provide a link to the o-scope output:
http://www.hardocp.com/image.html?image=MTMyMzQ4MTM1M2pQSGRoQWZNODZfOF8yX2wuZ2lm
Those time divisions are 2ms. There are approximately 10 AC noise cycles per division, or 0.2ms per cycle. That would be about 1/5,000 of a second each. Frequency = 1/time, so that would be about 5,000 Hz. Very audible. All switching PSUs are not made the same, there are significant tradeoffs and design factors depending on intended use, cost, etc. Computer switching power supplies were never intended to power audio amplifiers.

And not all noise comes from the PSU. Add in soundcards do help isolate the PSU noise, but running an amp off that PSU may cause a ground loop or magnifiy voltage line noise.
 

grimster

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Are you telling me a capacitor can't filter this out? How, oh HOW do we EVER get DC to anything besides batteries, then? Your BS is a joke.
 

Fenris_Ulf

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I just provided real world results. I guess all those guys at Seasonic and other PSU OEMs must be a bunch of idiots. Why oh why haven't they used capactiors? Well, they have, it's just they're not a panacea.

There is no such thing as true DC except in textbooks. Every voltage source has noise, even batteries (those chemical reactions are discrete events on the molecular level!). The question is always the allowable amount of noise/variation. Good audio power supplies will have at least -50dB of noise rejection at audio frequencies, excellent pre-amp and vacuum tube power supplies I've seen at better than 90dB. ATX spec is 20dB and doesn't specify frequency (they tend to use lower frequencies to avoid high power interference with other electronics).

Go research electrolytic capacitor ESR and leakage as well as electrolye composition and temperature vs lifespan and then factor in size and cost. Compare the capacitor Farad rating with what you need to supply the number of amps of current. Factor in losses due to resistance on circuit boards. Come to the realization that all of this varies with frequency. Write off electrolytic caps and switch to better film capacitors. Find out what the size and cost of 20,000uf of film capacitors is. Go back to electrolytic capacitors. Learn active filtering, PCB layout, and emf propagation. Discover diode switching noise. Now compromise with active regulation and capacitors to get within spec and at a competitive cost.

Trust me, I've tried a low pass CRC filter (5 ohms, 2x 15,000uF) which should give a 6 db roll off at 2Hz. It did jack, maybe 3db at several thousand Hz.

If you want to learn more about the basics of "simple" linear PSUs, try downloading and playing with the Duncan PSU simulator. Then realize that switching PSUs are about 10x more complicated.
 

grimster

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Hey, how about no? All you provided was that THAT particular power supply had some noise. I really don't care what you can copy and paste here or what experience you claim you have. If you can't build a computer with a sound card and not have noise come through it, you're choosing cheap crap. DC being pulsed still does not make it AC, so there IS such thing as DC.
 

Fenris_Ulf

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Hey, how about no? All you provided was that THAT particular power supply had some noise. I really don't care what you can copy and paste here or what experience you claim you have. If you can't build a computer with a sound card and not have noise come through it, you're choosing cheap crap. DC being pulsed still does not make it AC, so there IS such thing as DC.

Well, we're not talking about the noise level of a sound card are we. This thread was about an amp running off a PSU. And apparently you don't understand what DC and AC are. You can have primarily DC with an AC component - for example the previously mentioned PSU has a nominal "+12v" DC ouput with about a 10mv AC superimposed. You can have primarily AC with a DC component - I've seen house wiring with a volt or two of DC on it. You're probably thinking that AC voltage is alternating + and -. Well, you have to define what your zero volts is. Voltages are always relative, although the commonly accepted zero level is earth ground.
 

grimster

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I think you don't understand what AC or DC are. It would be 12 volts DC with a ±10mv ripple (electricity is still flowing only in one direction.) That doesn't mean AC is specifically superimposed over that DC signal. If it was "AC superimposed it would be 60 Hz", but it's just DC being pulsed is what makes that ripple.. AC voltage is alternating + and -, the hot lead flows in alternating directions. All DC voltage does to AC is offset it (DC offset in audio?)
 

atarione

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Hmm, we'll this seems to have started a thing. So while the amp isn't that expensive with it being Xmas time I'd rather not toss $40 away. It seems many think a separate mini amp would be better?
 

Fenris_Ulf

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Hmm, we'll this seems to have started a thing. So while the amp isn't that expensive with it being Xmas time I'd rather not toss $40 away. It seems many think a separate mini amp would be better?

I've never had a problem with a separate amp. Those Tripath based amps are pretty good and should be fine unless you're trying to fill a big room with sound. For sitting at your computer, they're more than enough.

Here's a couple from a reliable retailer:
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=300-380
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=310-300
 

Fenris_Ulf

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I think you don't understand what AC or DC are. It would be 12 volts DC with a ±10mv ripple (electricity is still flowing only in one direction.) That doesn't mean AC is specifically superimposed over that DC signal. If it was "AC superimposed it would be 60 Hz", but it's just DC being pulsed is what makes that ripple.. AC voltage is alternating + and -, the hot lead flows in alternating directions. All DC voltage does to AC is offset it (DC offset in audio?)

Depends on your reference point. Up to here we've been talking voltage, not current. Use +12v as your ground reference then measure the output and suddenly all you see is 10mv AC. And using this new ground reference, you most definitely would see current flow in both directions. And btw, AC =/= 60Hz and it is not necessisarily sinusoidal. AC can be any frequency except 0.
 

Mojo JoJo

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back to my second post.....if you look closely at the back plane of that card it says "speaker out" for the banana plugs, and "line out" for the 3.5mm connection. unless I am reading it wrong, or it's labeled wrong.

in any case a good external solution is probably your best safest solution.
 

dustNbone

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They labelled it wrong. Line Out should say Line In. I guess once you have a few thousand backplates stamped you just suck it up and sell them :)
 
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