Isolating amp power from preamp

[docmh]

I'm thinking of getting a SMS classic tube preamp ( basically blackface Twin)
it has a 1/4 inch jack to mate with a power source. I have Several amps at home I could use for power. How would I separate my amps power from it's preamp section?

[Dr-Joned]

What brand and model amps are you speaking of? Pretty much every amp can be modified to accept a power amp input. This would normally be performed by a competent bench tech.

[KT66]

You put a jack in the signal path between the preamp and the phase inverter so that when you are not plugged into it the amp functions as normal but when you plug into the jack the amps preamp becomes disconnected by the normally closed shorting jack and the power amp is then fed by whatever you plugged into the power amp in jack. As Dr. Joned suggested, if you don't have experience working on amps you should have a tech do it for you - you don't want to hurt yourself or mess your amp up.

[d95err]

If the amp has an fx loop, just plug into the fx return.

Otherwise you can plug into the regular amp input (the low imput if available) and set the EQ as flat as possible. Setting the EQ flat is not as straight forward as it could appear. For example, On a classic Fender tonestack, the flattest EQ is achieved by setting Mid to max and Bass and Treble to zero.