I have a amplifier using 6L6's in push pull. I am getting a little parasitic oscillation when i run a 400 Hz sine wave at full power. I remember from years ago putting a serial resistor in the plate circuit, between the plate and output transformer lead to suppress the oscillation.

Relocating the coupling caps has it almost gone, but I think adding the plate resistor's would be a good idea.

Anybody remember the normal value used ???

Thanks Bob

Bob,

Look at this site. http://www.montagar.com/~PATJ/ap56.htm
They used 50 ohm 1W.

Mike M.

:I have a amplifier using 6L6's in push pull. I am getting a little parasitic oscillation when i run a 400 Hz sine wave at full power. I remember from years ago putting a serial resistor in the plate circuit, between the plate and output transformer lead to suppress the oscillation.
:
:
:Relocating the coupling caps has it almost gone, but I think adding the plate resistor's would be a good idea.
:
:
:Anybody remember the normal value used ???
:
:Thanks Bob

Thanks Mike,
That amp looks quite nice, although a little over kill with the seperate bias for each of the 4 output tubes. But it answered my question.

:Bob,
:
:Look at this site. http://www.montagar.com/~PATJ/ap56.htm
:They used 50 ohm 1W.
:
:Mike M.
:
::I have a amplifier using 6L6's in push pull. I am getting a little parasitic oscillation when i run a 400 Hz sine wave at full power. I remember from years ago putting a serial resistor in the plate circuit, between the plate and output transformer lead to suppress the oscillation.
::
::
::Relocating the coupling caps has it almost gone, but I think adding the plate resistor's would be a good idea.
::
::
::Anybody remember the normal value used ???
::
::Thanks Bob