OT: Tube Audio

[Tony Duell]

> >OK, since there seem to be a fair amount of people into Tube audio, 
> >or at least with a knowledge of it.  Would someone care to explain 
> >the following to someone that is used to an all in one unit such as a 
> >Sony Receiver.  What is the purpose of separate Amp and Pre-Amps.  I 
> >think I understand the whole phono pre-stage, but I've yet to find a 
> >decent explanation of the rest, and I'm looking to switch to tubes 
> >for playback of records (primarily Vinyl, but I'm also interested in 
> >78's).
> 
> Purely from memory, but I believe one generally used a separate pre-amp
> mostly due to hum issues.  The power supply for the preamp could make use
> of lower plate voltages, better regulation and DC heater supplies.
> 
> Or so I think I recall.

In the case of the 2 main 'classic' English systems (Quad and Leak), 
there was no electrical reason for the 2 units that I can see. The 
preamplifier valves had an AC heater supply shared with the amplifier 
valves. The preamplifer HT+ (B+) line came from the main amplifier HT+ 
line (OK, with an RC decoupling network). In fact Quad even ran the radio 
tuner valves off the amplifier supply.

I think the real reason was that the valve power amplifier was heavy and 
bulky. By putting the controls on the preampifier (in fact at least one 
of those manufacturers called it the 'control unit'), you could stick the 
PSU/power amplifier chassis out of the way and just have to fit the 
relatively small preamplifier on the shelf/cabinet.

-tony