Swapping class AB amp linear supply with a SMPS - incl measurements

[Piere]

Duh??? Of course, if you increase loop gain by an extra op-amp as Tom did, you will improve PSRR as well. Nothing special there.

 

[egellings]

I think I read that the Hypex SMPS isn't regulated per se, the output follows the input. But it may indeed have a lower output impedance.

It could have good load regulation and not very good line regulation. A low output impedance will result in good load regulation even if line regulation is less than stellar.

 

[McFly]

In what sense? If an amp fails, it fails. Most time by some sense of overload or in the long run by wear out of electrolytic capacitors. The Hypex SMPS are designed for their own Class-D amps, not for general use.

So this hypex SMPS is not to be used with a class AB topology?

 

[CleanSound]

Thanks for doing this test and sharing. . .eye opening.

Your experiment leaves a lot of questions to be answered. I wonder if that is a result of just the Hypex SMPS and what would the results be with other SMPS. Saids a lot about modern day SMPS.

 

[Doodski]

So this hypex SMPS is not to be used with a class AB topology?

It supplied amps and voltage so yes, it should be good for class AB stuff. It won't load down/sag like a designed for the task power supply but it will do in a jiffy.

 

[egellings]

So this hypex SMPS is not to be used with a class AB topology?

If the switch mode supply delivers the same DC voltages as the conventional supply does, it should make no difference. Only possible problem could arise with the SMPS is that it is likely to be regulated, and won't sag much under load, whereas the 50/60Hz-xfmr-diode-'lytic one will sag, limiting the power dissipation in the output stage when severely overloaded. So long as that overload/dissipation issue is properly addressed, then both types of supply should work well. Power amplifier output stages don't benefit much from regulation, while small sign stages do.

 

[Piere]

So this hypex SMPS is not to be used with a class AB topology?

Why not? With general use I did mean powering lamps, motors etc. Read the manual. They are designed especially for the characteristic fluctuating momentary load of audio amplifiers. This in contrast with generic SMPS that like to see a constant load. So class-AB wouldn't be a problem provided rail voltages matches that of the amplifier. But you can't power a full class-A with it that draws severe power continously. Then it will smoke likely soon.