external power supply question, will it work??

If the wallwart’s a 24V unit, another 24V supply should work, providing it has the current capability, required by the preamp.

You need voltage AND current.

However, the problem is finding a high quality, low noise unit. You can find several wall warts which are digital and noisy as can be.

I can highly recommend Astron power supplies as great, low noise, general purpose units.

Best,
E

To be clear,
Voltage should match, but current can be over.

Agree Voltage needs to be correct, but the available amperage/current can be higher, even double or triple, quadruple. I would not worry about a four or five amp device. (I would avoid huge ones..thirty... fifty amperes and such though...), and no problem.Yes any power supply can do, What you want is a quality device, low ripple, good capacitor storage.
Almost all my preamps use a large separate power supply, One (actually two separate) was swapped by a rebuilder, Jon Soderberg and made as one for both the Threshold line and Threshold phono FET 10 pair.
I would suggest checking out American Science and Surplus.. over time they have all sorts of power supplies. Some are very high quality Science stuff. An actual store is better than the website.. But the website can do.