And this is how it all started

[Peter Daniel]

It all depends on what you whant to get out of your system. I believe that separate power transformers are giving you better value for the money than $300 power cords. With them come separate bridges for positive and negative rails (if not discreet soft recovery diodes). At least go for separate transformers for main channels and another one for center and surround. Depending on the rest of your system, but for me its not a law of diminishing returns anymore.

[capslock]

A large transformer will be more power-efficient and stiffer (i.e. less load dependent) than two smaller transformers of the same total rating.
Hence it might be a good idea both environmentally and sonically to use only on. Depending on how far you want to go, you can always use separate common mode chockes, rectifiers and filter caps for the channels.

In my amp, I have a common rectifier, choke and huge PI-filter. The channel boards are supplied from braided cables (to minimize the magnetic field) passing signal lines only at right angles and input stages only at a great distance. Then each board has its own 3x 4700 uF per rail as local decoupling.

Eric

[gromanswe]

Capslock.
I also prefer 1 trafo. That doesn't mean you can't
use separate rectifiers.
One could even provide separate rectifier
for the the inputstage.
To have inputstage well protected from output stage
I find very important.

Of cource different variations could lead to satisfying
result.
Amplified capacitance I also find as a good thing.

[Peter Daniel]

Maybe I would use one big transformer for stereo amp now. It was not possible in the pictured amp because my intention was to have very low chassis and two transformers fitted there perfectly. Sometimes looks are important.

Today, I wouldn't build a stereo amp. I always go for monoblocks, because I want to keep my amps close to speakers (especially when using expensive cables, when every foot counts).

[promitheus]

They look a lot better then my first attempts LOL :-)

[gromanswe]

Originally posted by HPotter

Today, I wouldn't build a stereo amp. I always go for monoblocks, because I want to keep my amps close to speakers (especially when using expensive cables, when every foot counts).

That is the most sensible thing you can do. It makes you most free to use you endstage in different ways.
In an non-active implication it can different.

Preamplifiers, controlamplifiers there you would like to have
everything in one place.
Not to have to "run around in room" when
selecting different features.
But this could also be overcome by using
remote signals.

[gromanswe]

When transfering the signal from signal source,
CDplayer, turntable, to Loudspeaker,
it preferable to maintain the amplitude.
That leaves best margin to background noise.
Background noise can be seen as "the ocean of noise".
It is often expressed in S/N-ratio. Signal to Noise.

When using some meters of Loudspeaker cable,
you get one problem. Transfering high currents
at high speeds.
When using bi-/tri-amping with monoblock mounted
next to woofers, you get another problem.
Tranfering the signal attenuated of Volume control
in centerplaced Preamp, to the Endstage.
My solution is to have a remotely controlled
attenuator, placed next to endstage input.
It can be wire-remote or Infrared-remote.

This solution keeps signal/noise HIGH over
the transfering distance.
The shorter distance a signal is low, the better!

[janneman]

Hi Gromanswe,

That is interesting. Can you give us some more info on how you implemented the "local" (to the monoblock power amps) remote volume control?

Jan Didden

[gromanswe]

CMOS 40193 up/down counter is remotely controlled
CMOS 4051 8-channel analog multiplexer
resistor divider
1 resistor is in series with incoming signal
where only the 8 resistors are switched to GND
the CMOS FETS works best around GND
this is repeated
twice with a buffer OP in between
to get 8x8=64 steps -1dB/step

[gromanswe]

http://www.gotham.ch/gac/datsheet/gac_1.htm

high quality
the RIGHT price