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Vacuum Tube Preamp Circuit Noise

Hey everyone,

I purchased some 6ak5 tubes to start messing around with.

After trying several schematics and nothing working, I attempted my own configuration and this is what I got.

This so far does exactly what I want, except for a high pitch squeeling noise I cannot get rid of. This is pretty much the first schematic that has gotten my a volume output from a tube.

I am plugging this device directly into a 100w solid state amplifier. Again I can hear everything perfectly like the way I want, I just need to get rid of this noise. I attached a schematic.


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If it works at all it is a miracle.
It also might blow out your 100W amp, and/or you speakers if you attempt to modify what you have already done.

But before you decide what circuit to use, or what tube to use, please tell us what you want to do.
What is the purpose and intended function of your 6AK5 amp?

Fuzz Box?
Or what?

After we hear an accurate description of what you want the 6AK5 to do, we might have an idea or two.

If I had a 6AK5 Pentode, I would Triode Wire it (but I am kind of strange that way).

Please post a Real schematic of a 'Valvecaster'.

You are posting in the Tubes / Valves threads (Hi Fi and Stereo).
There is an Instruments & Amps thread area (Guitars, Guitar amplifiers, and such) they know what a Valvecaster is.

Your "schematic" is not a real working schematic.

Triode wired, but No plate/screen load resistor, no B+, and no connection from B+ to that 'missing' plate/screen load resistor.

Filaments are AC or DC? If they are AC powered, that is a problem. Because you have a 100k Ohm cathode/suppressor resistor to ground, any AC filament to cathode leakage Will Add Noise to this circuit.

Also, you have a 470k Ohm g1 resistor to ground, the 6AK5 maximum resistor specification is 100k Ohm.

Once you have B+ and a plate/screen load resistor, you are going to need a coupling cap from the plate/screen to the output, and a resistor from the output to ground.

There will be more questions when we get a real complete and accurate working Valvecaster schematic.

Hang in there.
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The "schematic" in Post # 1 can not work as it is drawn.

I do not know what a Valvecaster is, but I bet it is a tube circuit to give some voltage amplification, some harmonic and intermodulation distortion,
in order to change the sound of an electric guitar.

In order for a 6AK5 pentode to work as a triode wired pentode voltage amplifier . . .
it has to have a proper input circuit, a reasonable resistance cathode resistor, a plate load resistor, B+ voltage, and a C and R output coupling network to remove DC to the next stage.