Unity gain power amplifier for guitar

[kacernator]

Could anyone guide me to unity gain power buffer for driving loudspeakers which would have high output impedance - say 4 Ohms and low distortion.
It is intended as guitar power amplifier.


Thanks.

 

[JMFahey]

Unity gain power buffers by definition have very high NFB, either because they are emitter/source followers which is 100% NFB or they are stages with higher open loop gain padded down to unity.

In any case they have inherently low impedance.

Low distortion is a given , so don´t worry about that.

Or, you could cheat: make a normal mixed feedback power amplifier with 4 ohms output impedance, which will have, say, 20X gain ... and pad input signal also 20X so *system* gain is 1.

 

[kacernator]

Unity gain power buffers by definition have very high NFB, either because they are emitter/source followers which is 100% NFB or they are stages with higher open loop gain padded down to unity.

In any case they have inherently low impedance.

Low distortion is a given , so don´t worry about that.

Or, you could cheat: make a normal mixed feedback power amplifier with 4 ohms output impedance, which will have, say, 20X gain ... and pad input signal also 20X so *system* gain is 1.

Thats exactly what I do not want to do. Because I intend to drive buffer with tube preamp and I want tubes to make all the voltage gain.

 

[kacernator]

Is it the same when I put 4 Ohm resistor at the output of amplifier as raising the output impedance with current feedback?

Could be the current feedback implemented to Hawksford error correction scheme, like in paX amplifier?

paX: an error-correction power amp

 

[sreten]

Hi,

Its easy enough to get 4 ohms output impedance.

Variable Amplifier Impedance

Why you want unity gain is a bit beyond me,
that is just making life difficult AFAICT.

rgds, sreten.

 

[AndrewT]

just use a 4r0 resistor.
It will have the same effect as having a buffer/amplifier with a 4ohms output impedance.
The resistor if not overheated will be more accurate.

 

[kacernator]

Ok, thanks. Resistor definately simplifies things a lot.