Swedish Chef
Well-known member
In my preamp, after a voltage gain stage and a cathode follower stage, I have a normal tonestack a la Fender, I'm coming off the Treble wiper, 220K stopper resistor (is that what it's called?) and then through a 1K5 into the EL84 grid.
I have a feeling that this should be wrong as there are usually stages after the stack (PI or another gain stage) to buffer the output. The thing is it sounds pretty darned good up to a certain point, after which it gets a little nasty. I am guessing that the point after which it starts complaining is where grid current begins to flow for a portion of the wave cycle. I have scoped around it and the waveform looks okay going in at the top of the tone stack but pretty wonky coming out.
Any thoughts would be appreciated, and I'll try and scribble a schem for you to see what I'm doing...
Oh and I have a variable B+ on the EL84 for variable power o/p, and I realise that as I ramp the B+ down, at some point grid current will flow, but I just want to tame it a little...
p.s. yes there is power to pin 7 of the EL84, I just neglected to draw it. sorry!
Chef
I have a feeling that this should be wrong as there are usually stages after the stack (PI or another gain stage) to buffer the output. The thing is it sounds pretty darned good up to a certain point, after which it gets a little nasty. I am guessing that the point after which it starts complaining is where grid current begins to flow for a portion of the wave cycle. I have scoped around it and the waveform looks okay going in at the top of the tone stack but pretty wonky coming out.
Any thoughts would be appreciated, and I'll try and scribble a schem for you to see what I'm doing...
Oh and I have a variable B+ on the EL84 for variable power o/p, and I realise that as I ramp the B+ down, at some point grid current will flow, but I just want to tame it a little...
p.s. yes there is power to pin 7 of the EL84, I just neglected to draw it. sorry!
Chef