Which of These Components Should Not Be Close Together?

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Hi


Assume that you have the following:
- a Desktop PC
- a USB Powered DAC
- an Amplifier Board
(and of course, in the end of all these, Speakers)

Can the first 3 be combined in 1 case?
For example, opening the PC's case, and putting there the DAC and the Amplifier?

I remember reading somewhere, that one of these components (I think the Amplifier) creates noise..


Pleas advise..

Thank you
 
You can include the amp also inside the PC, using the same power supply, depending of the power. I am using a self-designed Class D amp powered from the ATX power supply. Sound isn't the best, internet connection isn't excellent and the 4" speakers aren't the plus ultra, but for listening streaming audios/videos it suffices.
 

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Hmm..
That's 5W per speaker or 2x 5W?
What is the maximum current?

In any case I can use an external power supply, If the PC's power will not fit..
So back to the original problem: isn't there any problem with putting audio system components inside a computer's case?
I really remember reading twice people mentioning noise being generated, either by the amplifier, or by the PC, or both..
 
Hmm..
That's 5W per speaker or 2x 5W?

My fault, it is a bit more than 5W:

Prms = Urms^2/R

Prms = (12V/sqrt(2)) ^2 /8ohm = 9W for 8ohm speaker

Each channel, of course.

What is the maximum current?
Again, trivial calculation:

I = U/R

12V/8ohm = 1.5A max


So back to the original problem: isn't there any problem with putting audio system components inside a computer's case?

The amp has no effect on PC function. The PC noise can get induced in amp input circuits - placing the tiny TPA3116 amp into any shielded enclosure is simple. Proper balanced lines will eliminate the induced noise into input lines.

Always to key is making sure no ground loop within the signal path occurs - either using non-grounded PSU for the amp, or using balanced inputs of the amp.

For 12V PSU and the dirt-cheap quite distorting TPA3116 you may want to try the onboard Intel HDA soundcard directly. When properly connected (balanced) it has rather good params and sounds pretty good (no noise, distortion much below that of TPA3116). It may save you the USB DAC which would need to be shielded in the PC (IMO useless for this setup).
 
Hi Osvaldo

Using the PC's internal power supply for the Amp will not cause any trouble?
I am not just worried about the sound, i am also worried about my computer :)

Do you mean that the internet connection is affected by the circuit being inside?
Or you mention it without any connection to the circuit inside?

No, the amp will no overload the PC supply as it usually is well overrated, and you will not take thousands of watts from it, ten or twenty watts is of no trouble, I had repaired lots of them in past decades.

Internet connections here in Argentina, like cell phones are trouble per se. All way. All time. The amp doesn't interfere at any way with the LAN connection, as it is very resistant to interferences, provided wiring is properly.
 
Again, trivial calculation:
I = U/R
Yeah, I just didn't know if the 5W you mentioned is total, or x2 ;)


placing the tiny TPA3116 amp into any shielded enclosure is simple.
Are all metals good here, for a shielding enclosure, or just some specific metals will work?
And If I don't have a metal enclosure, can I take a plastic enclosure, and wrap it inside with some material that comes as a sheet?


Proper balanced lines will eliminate the induced noise into input lines.
Hmm, how is this done?



(IMO useless for this setup).
You say an external DAC is unneeded when using the TPA3116 amplifier?
Is it that bad?


(just for the record, my current speakers are Yamaha HS7, with a built-in Class AB amplifier (LM3886).
Th question in the current thread is about a second computer, with a simpler setup)


Osvaldo:
Oh..
Was worried that you might've meant that there is any relation between the 2 ;)
 
Going back to the topic, the ATX PSU can support efficiently a small amp. My project uses the ±12V rails as a kind of well regulated split power supply. Speakers are humble 4" in a small cabinet, and for listening background music is more than I need. Remember I'm in the job, so not too much volume I want.

Sometimes it captures some noise from the video or HDD, but still, is used for background music only.

I reinforced a bit the -12V line using two bigger diodes in the PSU, originally they were common UF4xxx diodes, and I replace them with 1N5822, 3Amper shottky, and the original cap (470µF 16V) was replaced by a 2200µF 16V, to enhance transient response, as the kind of half bridge PSU's are naturally slow. But in general terms, it performs excellent given the limitations of the service.

Lot of time ago, I was using more or less the same configuration but using TDA2006´s powered also from the ±12V rails, the same good results. But as I wanted to migrate to an experimental class D using parts in stock at job, this was the final layout. The schematic is available, if you want it. And very simple.
 
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the ATX PSU can support efficiently a small amp. My project uses the ±12V rails as a kind of well regulated split power supply.
Oh..
I wasn't aware that it also provides -12v..
I thought al voltages are V with Gnd..
But now I see there's -12v, and also -5v..
(3.3v doesn't have a -3.3v tho)


connector_atx_pinout.GIF



I wonder, why is that needed, in a computer? What parts of it might need the minus part?



Lot of time ago, I was using more or less the same configuration but using TDA2006´s powered also from the ±12V rails, the same good results. But as I wanted to migrate to an experimental class D using parts in stock at job, this was the final layout. The schematic is available, if you want it. And very simple.
Sounds cool, thank you..
I am using all ready-made modules, so not so much "DIY" for me..
 
Yeah, I just didn't know if the 5W you mentioned is total, or x2 ;)

Each channel has the same supply voltage, hence each channel has full power allowed by the voltage.



Are all metals good here, for a shielding enclosure, or just some specific metals will work?
And If I don't have a metal enclosure, can I take a plastic enclosure, and wrap it inside with some material that comes as a sheet?


Try first without any enclosure. It will be OK, most likely. Any conducting shield will do. I commonly use 3D-printed enclosures covered with grounded copper tape - works OK.

Headless Amplifier Measurement Workstation

Balanced Amp Outputs Measurement Adapter


Proper balanced lines will eliminate the induced noise into input lines.
Hmm, how is this done?

Well, the impedances are not balanced, but it works - just use proper twisted and shielded balanced cables from the soundcard to the amp. Any inexpensive microphone cable will do.


You say an external DAC is unneeded when using the TPA3116 amplifier?
Is it that bad?

It is great for its price. But the soundcard has way lower distortion than this amp (soundcard < 0.01%, amp 0.03%+). My measurements of TPA3116 with balanced connection to internal soundcard of FS Futro S550 powered by the 19V power adapter of PC are enclosed. Nothing special, IMO no reason to invest into a USB DAC. But you can always try and if you do not like it, get the USB DAC afterwards. You will need the balanced connection anyway if the DAC is powered/connected to the PC.
 

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You have +12V in any yellow cable. Preferably, use those connected to the mother, that has more steady current and lower current (The cables to the HDD can contain more motor ripple), or any unused set of cables. Blue cable has -12V over a limited power capability (Usually 0.5Amper), but the current drained to it by the CPU is only to the audio section and series port, and in rigor it must be there although nowadays it is not used, as the RS232 terminals has been deleted from the motherboard. And any black cable is ground. In any instance you can filter a bit the power lines as I did in my project (Small chokes of 10µH and 1mF @ 16V is sufficient)
 
I commonly use 3D-printed enclosures covered with grounded copper tape - works OK.
Cool, I should get a copper tape..


It is great for its price. But the soundcard has way lower distortion than this amp (soundcard < 0.01%, amp 0.03%+).
Hmm, will the TDA7297 (Class AB) be a better option than the TPA3116,
or is it in the same level?


Preferably, use those connected to the mother, that has more steady current and lower current (The cables to the HDD can contain more motor ripple)
Today with SSDs being so fairly priced, Mechanical HardDrives are disappearing from most computers..
I have an SSD,
yet I still have 2 motors left in my computer:
1) the CPU Fan
2) the main PSU's internal fan



-12V was part of PCI connector, IMO presumably for soundcards. Today PCI-e soundcards must deploy a DC-DC convertor if they want their analog stage powered symmetrically (e.g. Juli@ XTe based on the original PCI Juli@)
So t was mainly for audio?
Really interesting :)
How nice
 
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