are all amps equal

Shadorne - I can make case for bad power supply being less affected by power cord than very good one. Here it comes:

Average value of current being drawn from power supply caps is taken from transformer in very sharp pulses. These pulses heat up transformer (higher harmonic content heats-up the core and much higher rms value than average value heats-up the copper) and appear on the power cord. Sharpness and amplitude of these pulses can be determined from diagrams: conduction angle that depends on ratio of transformer output impedance to ESR of capacitor.

Amplifier with poor capacitors (higher ESR) will have longer pulses of smaller amplitude and will possibly be less dependant on gauge of power cord (for voltage drops) or shielding (for polution).

Mentioned conduction angle is a Catch 22 for designers - in order to know how big transformer should be (to accomodate for bigger losses caused by sharp current pulses) conduction angle has to be found. It require value of transformer's output impedance - not known since transformer is not designed yet.

I made this a little bit technical to show that anything can be proved. Somebody can probably make equally valid case that proves just the opposite.

Kijanki,

There is a lot of distortion in power supply transformers - AC power has all kinds of terrible harmonics to begin with and can often look more like a square wave than a sinusoid - but who cares - the idea is to prevent all this stuff from ever reaching the power supply rails or the audio signal by careful design.

Kijanki, I'm definately with you on this one . . . an interesting comparison is the differnces between these conduction-angles and time-constants between tube and solid-state amps. Tube amps have lossier power transformers, (sometimes) tube rectifiers, C-L-C or L-C filtering (and more RC for the small-signal stages) . . . which all seems to have the effect of making the filtering time constants much longer than a typical SS amp - in both directions.

Then there's another little detail that is so often ignored - the fact that the vast majority of "DC coupled" solid-state amps are in fact capacitively coupled . . . Kirchhoff's law says the AC ground current from the speaker has to go somewhere, so it returns through the main filter capacitors. It's just that they're in the feedback loop all the way to DC that makes DC offset possible at the output, thus making it "DC coupled".

Kirkus - Tubes should be better then, for reducing power related hash. I'm getting interested in power cables and their effect on the sound. My Benchmark DAC has regulated linear supply while my Rowland 102 has a switcher. I have to find some testimonies on power cables - I'm not sure where to start - possibly with the same brand as my interconnect and speaker cable (Acoustic Zen). Is there any science behind power cables other than gauge, inductance and shielding?

Your DC coupling observation is very interesting one and suggest that good sound depends more on the quality of this cap than we think. Good low ESR low inductance caps are expensive (like slit foil type) and fixing cheap ones with Mylar cap in parallel can make it worst by adding lossless cap in parallel to inductive cap creating in effect resonant circuit that rings (and is in the signal path).