Will this isolation transformer limit power draw?

An outboard bank of caps is FAR less effective than capacitors placed as close as possible to the output devices. That is, as far as storage devices go and minimizing sag on the rails.

As far as the 60 Hz voltage vs the rail voltage goes, the 60 Hz voltage will always be higher than the rails in most conventional designs. If one were using only partial rectification and not a bridge, the charging rate would be far more cyclical. As it is, the cycling with the resultant "glitching" that occurs during a typical charge rate has to do with the diodes themselves turning off and on, which produces ringing and distortion. This can be seen in many amps as a 120 Hz and sometimes even a 180 Hz resonance. This is why many designers are switching over to diodes that recover more quickly as they produce less noise.

Other than that, believe me, a good iso transformer will do GOBS more for you than a bank of caps could in terms of the filtering of noise. Having said that, i am a BIG fan of large capacitor reserves within the component itself, especially in power amps. That's why i've purchased BIG electrolytic cans by the box-full. Sean
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sean...60 Hz ac sinewave input power is at zero volts 120 times per second, and below rail voltage most of the time. (That's why we found a square wave power input was better).

Outboard location of some PS capacitance is OK. After all, some designs (usually "High End") put the entire PS on a separate chassis. Also, it is usual to have some small amount of PS capacitance distributed right on the active circuit boards to minimize the effect of inductance between the PS and the circuits.

Shall we now start a bragging contest to see who has the biggest capacitor :-)

Sooo,

is it a valid, non-stupid, non-deluded audiophile smoke-and-mirrors trick to use an isolation transformer (or a balanced transformer, perhaps) to minimize a slight humming or buzzing sound (ie lower the "noise floor") emitting from my speakers with the Bryston?

What would be better, just plug it to the wall and deal with the noise? I've already used the ground lift switch. My interconnects are all properly grounded at the source side, and my receiver did NOT produce even the slightest bit of noise (the Denon 3803)..

What other ideas would work to rectify the problem?

Sounds like the Bryston has a problem.

Does it hum or buzz when input interconnects are disconnected (ie: only the power amp is connected to the speakers)?

Other ideas...Are the source components and the power amp pluged into different outlets, which may be on oposite phases of the 115 V power? Try putting everything on one plug.

Try the interconnects the other ("wrong") way around. Sometimes this is better.

If this is why you are thinking of an isolation transfromer make sure you can take it back for refund when it doesn't work.

El: That's a good point about the "down time" on a sine as it is crossing over. Forgot about that : )

I can also see how a square wave would be FAR more efficient due to the longer duty cycle and more consistent peak to average ratio.

While it is true that many designs use an outboard power supply, the separate chassis typically just houses the transformer and / or rectifiers. Some designs do place the main filter caps in the outboard chassis, which is a poorer design in my experience. That's because the "umbilical cord" between the active circuitry and the output power supply acts as an antenna with minimal filtering at the point of entry into the circuitry.

Drlazybones: Work your way back through your system piece by piece to see where the hum is coming from. That is, hook up the amp to the speakers with nothing hooked up to the amp and see if you hear any hum. If nothing, turn the amp off, hook up interconnects to the amp and then turn it back on. If no hum, turn off the amp and connect the interconnects to your preamp with nothing else connected to the preamp. Do this until you find the source of the hum. It may be a bad set of cables and / or a ground loop that occurs only when specific components are tied together into the system. This can be VERY annoying and difficult to find, hence the need for step by step analysis.

As a side note, if you are running any gear that has a non-polarized two prong power cord, you might want to try flipping it around in the AC outlet. Some gear is VERY sensitive to proper AC polarity. Sean
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