Can i use a computer power supply to power audio amplifiers?

[enter]

Very intresting thread that you started Carlos.
Many times before i wondered haw this kind of psu can be modifide to use with audio amplifires since many of them can be find very cheap and easy.Many pepole just throw them to garbage and they work fine.
I dont know haw this psu works exactly to modifie them, but with some help from more experienced pepole over here i can do this i think.Something simple i wonder is haw can it be done to take of the fan.Will then some beter heatsinks be suitable to do the job? Although there are more serious things to modifie this is just a thought i have right now.


Thanks George

[destroyer X]

Those ones, Jens and Eva are good EE, and Eva is deeply experienced in those supplies....maybe Jens too.

Eva, if you have some sketch, may be interesting to publish, so we can try, if it is not too much complicated.

regards,

Carlos

[mod_evil]

Hi carlos,

If you put a computer power supply to supply your amplifier you will have much noise, because this supplys isn't isolated from your AC-Line.

Frist,
You will change the frist diode bridge to a 8A Diode Bridge.

Second,
Change the dissipators. Because this isn't addecuated...

Third,
Put a Choke Coil in the input line and in the output line.

I think you isn't will have 35v. I have modified the line of 12v of a Enermax power supply ( It costs R$350 in Brazil ) to have in the output the high voltage to me.

The high voltage I have before the power supply will southdown ( is it correct? ) is 20v.

How you will give 35v from this power supply?

:P

[EWorkshop1708]

What about winding a toroid to replace the transformer on the PCB, and wind it with a 120V primary, and wind a CT secondary for your +/- outputs?

That way you can use the existing circuits, but your transfomer would be more suitable.

[Eva]

If a toroid is employed, you have to manage to put 3 layers of mylar insulation tape (or a material with similar properties) between the primary and the secondary windings. I have tried it and taping such a toroid ends up being quite difficult. Toroids are usually found in applications where no special insulation requirements exist.

[EWorkshop1708]

Originally posted by Eva
If a toroid is employed, you have to manage to put 3 layers of mylar insulation tape (or a material with similar properties) between the primary and the secondary windings. I have tried it and taping such a toroid ends up being quite difficult. Toroids are usually found in applications where no special insulation requirements exist.

Thanks for clearing that up.

Would not want a short to form (or a spark to jump) between primary and secondary windings!

[myhrrhleine]

Originally posted by destroyer X
Now a days, those computer supplies are very cheap.

I was thinking if is possible to modify to 35 Volts for instance.

Do you think that the oscilating frequency will be captured by our audio amplifiers?

It very well could.

Do you think we can increase the oscilating frequencies to avoid that?

It'd probably end up more work than it's worth.

The increase of oscilating frequency will be a good solution?

Not in my opinion.

Can this frequency cross the Supply shield can and be detected by our amplifiers?

Yes.

Do you think that I can install 30000 uF in the outputs?

Likely no.
The current needed to charge those would likely cause damage.

Can you suggest modifications to use them as audio supplies?

I'd recommend avoiding them.

Do you have some experience?… something practical related that?

They're very noisy.

Can you suggest filter values?

No.

Do you think that I will maintain the supply power when increase the voltage….. as 240 watts can be 20 amperes and 12volts….will 35 Volts have more than 6 amperes as simple calculations will shown us?

It's not that simple

If you can answer to one of more questions, please, go ahead.

OK

Thank you in advance by the cooperation

Regards,

Carlos

[enter]

I dig out some tips from an old radio telecommunications magazine.


It is a 13.6 V 20A psu made out of the Computer psu. All you need for added parts are a couple of 20 Watt 10 Ohm Power
Resistors, a FT140-43 Toroid Cors, a fuse holder and fuse.The 20 Watt 10 Ohm Resistors are to load the 5 Volt Supplies. The Computer Power Switchers will not produce output with out this load.The FT140-43 Toroid Cors use is for bundling the cables and rejecting undesirable RF.As for the voltage adjustment from 12V to 13,6V was done from a pcb pot his psu has(some psu dosent have that).


This is all the info i could find and i posted them as a good starting point although the major problem i think will be the oscilating frequencies


Regards George

[destroyer X]

I was already having strong suspections that will not be a good idea.

And now, as i could observe from many opinions, things will be very difficult and problematic...so, better to avoid such big modifications alike the ones i was intended to make.

I thank you very much...Avalon Islands,E Workshop 1708,Myhrrhleine, enter, Eva and Mod Evil.

Also the other guys that entered to help...but i am giving up....i am concluding that this idea is not good enougth to start some construction.... and if those modification are hard to Eva, well.... hard to her is impossible to me.


regards,

Carlos

[lineup]

Can I jump in with a question.

I have here a PC power supply, 200W, I found somewhere.
Output / Regulation %
--------------------------------
+12V/8A +-5%
+5V/20A +-4%
-5V/0.5A +-10%
-12V/0.5A +-10%
--------------------------------

I was thinking of using only the +12V/8A
to make a low power Mini Amplifier.
I think it is not impossible.
And 8 Ampere is more than enough to power both channels.

I will NOT BRIDGE! (any such suggestion is a waste of your time)
Output will be like 2x2Watt/6Ohm in Class A.
A push-pull common collector output stage.
Idle current ~ 0.7-1.0 A. Per channel.

--------------------------------

If my idea is alright
I will draw up a first version schematic with my EAGLE Schematic CAD.

Is there anything special to consider, before I start?