Tubes Tubes

[Rene Schmitz]

At 09:52 14.12.99 +0100, Ingo Debus wrote:
>
>
>Rene Schmitz wrote:
>> Nearly all older (and prefered)
>> guitar amps have no feedback, or just feedback within one stage.
>
>In guitar or bass tube amps, I've often seen a connection from a
>secondary winding of the output transformer to somewhere before the
>power amp stage. Isn't that for feedback?
>

Yes, that is for feedback. Ususally this voltage goes back to the cathode 
of the tube before the phase splitter. Its an example for feedback over 
several stages. I had the VOX AC-30 in mind, which just has one 
current-feedback stage. 

However these several-stage-feedback amps are not used in the high-gain limit 
like opamps (or some discrete SS-power amps). That is the amplifiers open
loop 
gain is much lower. So the amps gain (and bandwidth, distortion ...) are not 
solely determined by the feedback.

Bye
 René

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