external power supplies

I believe it is a theoretical advantage on today's line stages. Back in the days of real preamps (with built in phono stages), a seperate supply had real value. The smaller the signal, the more it needed to be sheilded from magnetic interfence from the power supply.

As of today, when most 'preamps' are actually line stages, the signal is strong enough, and the power supplies can be internally shielded well enough, that seperate power supplies really are only theoretical improvements.

I guess if you are still considering a full function preamp (w/phono) today, there could possibly be a slight audible difference from the phono source with an internal vs. external supply.

John

Well, in theory.........you could introduce some RF noise and other crud along the cable from the supply to the preamp. Keeping the power transformers as far away as possible from sensitive circuitry is a good idea.

(Also applies to amps like the S-150. Hope Nelson isn't reading this. Inside joke.)

I've wondered why there are no amps with external power supplies. Espescially class A, where the heat can get to the caps. There were the Rowland batteries back in the day and the Coda System 100 that seperated the input section. Joule has it's variac. Almost forgot about that Mission/Cyrus optional PS.

Is it just a matter of packaging and financial restraints or is it market and tradition driven, expecting big boxes? Considering the weight and size of some the big amps, perhaps they would be better off in 2 chasis. It could also lead to a modular design and vertical upgrade path.

A while back, I came across some foot square by 4" heat sinks and I seriously considered building some DIY amps with external power supplies and EI trannys. The amplifier boxes would have been one foot cubes, two-thirds of which would have been aluminum fins. Of course, what stopped me is that I have no idea of what I'm doing.