iNuke as Bench Supply?

[ssashton]

With Dave's recent videos about the cheap bench supply modules I'm curious to ask if an idea I've had for a while will actually work? Is there any reason one could not take a cheap high power class-d audio amp such as the behringer iNuke 3000, remove the a.c. coupling capacitors and connect an adjustable voltage reference to get a massively powerful, low noise clean supply? The iNuke 3000 will drop 1500watts into 2ohm loads.

I am not aware of any reason a class-d amp can not supply clean DC on the output. You could even use a clean ossilator to get an adjustable A.C. supply at least up to 20khz. Even if you could remove input filtering you might not want to go higher in frequency since you want to stay away from the switching freq. of the amp and let the output LP filter do it's work.

A current limit on the output would need more fiddling to achieve

Anyone done it?

[wraper]

Why do you think it will have low noise or remotely accurate output? Not to say output voltage not varying with load. And there won't be any of features that normal bench supply has like constant current.

A current limit on the output would need more fiddling to achieve

Fiddling? More like building from a scratch.

[wraper]

And it's not like it will be capable of supplying 1500W continuous, or not burn under all possible loads or short circuit. Also you can buy real switch mode 1000W PSU with constant current for the same money.

[b_force]

The problem with most audio amplifiers, is that the thermal design isn't adequate enough.
That's even true for high professional brands like Hypex, Pascal, IcePower etc etc.
They can only provide the rated power for so long, which is fine for music.
But with a DC current (or continues ACrms current), this is a whole different story.

In my career I tested most of these amplifiers, and pretty much none of them will deliver the rated power for more than (roughly) 30 minutes or so.
For the price the iNukes are pretty decent, but they have one of the worst thermal designs I have ever seen for an high power unit.

So in theory it can be done, easily even.
In practice it's a bit of a different story.

[ssashton]

Why do you think it will have low noise or remotely accurate output? Not to say output voltage not varying with load. And there won't be any of features that normal bench supply has like constant current.

A current limit on the output would need more fiddling to achieve

Fiddling? More like building from a scratch.

Audio amps are designed with the specific intention of reproducing the input as accurately as possible, although AC not DC I admit.

Your point that you can buy a 1000watt bench supply as cheaply is a good one! I wonder how they would compare on noise. I suppose a DC only bench supply has the advantage that it can employ much heavier LP filtering.

I thought about it because I know that a certain turntable maker uses the exact same circuit for their 'low noise AC motor driver' as they do for their power amp. They obviously thought it was a good way to get a clean AC power signal, but it does only need to drive the motor at max 45RPM.

[Shock]

How about buying a precision low noise power supply connecting it to the input, then cranking your amp up and sit back and enjoy all that low noise.

Or how about get a sine wave signal generator, connect it to the input and add some diodes and capacitors on the output, then you can have DC of any frequency.

Just make sure you get beryllium-copper cables and gold plated plugs, in case you run into high THD.

[wraper]

Audio amps are designed with the specific intention of reproducing the input as accurately as possible, although AC not DC I admit.

Nothing to do with reality. All audio amp aiming is low distortion and noise in audible frequency range, that's all. Amplification may change by 5% within a minute and it still will be in spec.