Re: [sdiy] Request brain dump on balanced lines

[Don Tillman]

   > From: jhaible at debitel.net
   > Date: Mon, 14 Oct 2002 14:58:06 +0000 (UTC)
   > 
   > Don says:
   > >By the way, my comments shouldn't be interpreted to mean that I hear
   > >no difference between a typical tube amp design and a typical
   > >transistor amp design.  I just don't think the difference lies in some
   > >weird abstraction involving the second harmonic.
   > 
   > Yes, but an abstraction that prefers lower order harmonics against
   > higher order harmonics covers a remarkable amount of 
   > phenomena that are considered relevant for a pleasant sound.

For cases where the topology of the amplifiers are simliar, sure.
Especially for intermodulation issues.

But when the topologies of the amplifiers being compared are very
different, and thus the basic processes involved are different, I
would say that such an abstraction becomes deceptive.

   > >(To that end, I'll even claim that they typical opamp-style transistor
   > >amp is not an amplifier at all, it's a servo.)
   > 
   > And the servo works nicely if it is fast enough, and as long as it
   > does not hit its limits of operation. 

But at the same time the output is the gain times the error.  :-)

   > In a way, even a slight feedback from the output winding to 
   > the driver stage of a tube amp is a "servo". 

When the qualities of the gain stage are significantly different from
the qualities of the overall amplifier (gain, bandwidth, phase,
distortion, etc.) I think you're firmly in servo land.

  -- Don

-- 
Don Tillman
Palo Alto, California, USA
don at till.com
http://www.till.com