Re: Valve frequency multipliers

john larkin <jl@glen--canyon.com> wrote:

On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <cd@notformail.com>
wrote:

[...]

   Operating Point:
       Grid Voltage: Adjusting the grid voltage to operate closer to
cutoff can increase harmonic distortion since the tube's response
becomes more non-linear near cutoff.

 
Operate it deep in cutoff, off most of the time. A high amplitude
drive and grid-leak bias would be good.

That is exactly what I am doing and it doesn't appear to be working.
With 100v on the anode,  15 Mc/s at 25v pk/pk on the grid and a 22k grid
leak, the peak current for one triode of an ECC91 is around 20 - 30 mA
at the positive peak of the grid swing.  The average anode current is
around 2.5 mA, so the conduction period is about 10%.

A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so
little drive to the following stage that I can't see any change in the
average grid voltage of that stage caused by the drive.


--
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk