AC to AC supply: Are some better than others?

[Cableaddict]

I need a ps that outputs 24vac, for a mic preamp.

The supply that came with this preamp was a cheap wallwart type, evidently just a tranny encased in plastic.

I'm wondering if I might getting better sound, or more stability or whatever, with a higher quality unit, but not sure if there even IS such a thing with an AC - to -AC supply. So... IS THERE?

For instance:
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Is there such a thing as AC regulation (In a small package) ?

I've seen some supplies with a "current limiting, earth ground" secondary.
Is this a good thing, and something to pay extra for no matter what might be inside the preamp itself?

How about using a 24v laptop supply? Those have some kind of regulation, no? (Or is it "no" ? )

How about shielding? I can always add ferrite beads to both the input & output wiring, but is there more to it than that?

[budm]

Re: AC to AC supply: Are some better than others?

It sounds like a simple step-down transformer that step the 120VAC inout down to 24VAC.
What is the current rating?
Is it bad at this point?
The preamp has rectifier circuit that convert AC to dc and feed the DC regulator circuits to maintain constant DC so if the AC input varies the DC will always be constant.
There should be protection in the primary side of that transformer in case you have shorted circuit or if the temperature gets to high.
Your preamp itself should also have protection circuits.
What is the make and model of the MIC preamp?

[Cableaddict]

Re: AC to AC supply: Are some better than others?

^ Thanks.

Kind of what I thought, but I wanted to be sure.

I guess this kind of design exists to keep noise down, or maybe so the entire chassis can be smaller, thus slightly less expensive. Good point about short-protection on the primary, though it's hard to know if that exists when looking at these things.

FWIW, this is just an Aphex 107. They're actually pretty decent sounding if you change the op amps, and swap the 12AX7 for a good 12AT7. I figure the techs created a good design, then the bean counters destroyed it with cost-cutting, so maybe the power supply could be improved.

I'm now thinking (just for fun) of bypassing the entire psu with a separate, linear, well-regulated supply. Probably not worth the trouble, but it WOULD be an interesting experiment.
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And just for references, what is a "current limiting, earth ground" secondary? I saw this on a smallish AC -to- AC supply, offered by Cornelius. Could this just be some kind of "death cap," as used in tube amps, etc?

[budm]

Re: AC to AC supply: Are some better than others?

You cannot just feed DC into the device that required AC unless you know how that AC is converted into multiple DC output Voltages or not, I.E. DUAL-SUPPLY (+/-) to run the OPAMP .
Using external power supply is one way of reducing the cost of UL safety compliance testing. The safety will be on that power transformer, you should see the real UL E# printed on that wallwart.
You can open up the unit and show us the pictures of the inside of the unit.