High voltage single tube overdrive (12v/80v)

High voltage single tube overdrive (12v/80v)

Project description

This unverified layout is based on this schematic by fredjuh.

Possible tweaks:
R1: Bias resistor that controls clipping behavior.
R3: Bias resistor that controls clipping behavior and low frequencies.
R12: Bias resistor that controls clipping behavior and gain.
R15: Lower to 50K or increase to 220K. Major influence on clipping.
R14: Major influence on gain and clipping of the JFET.
C1: Low end amplification.
C2, R5: High pass filter. Decreases highs and mids to increase low response.
C3: Determines the "fizz" in the overdrive.
C10: High end amplification and gain.

For use with a clean amplifier: reduce C3. If your (tube) amp will oversaturate: remove C2 and R5.

Bill of materials

R1: 50K
R2: 1M
R3: 2.2K
R4: 1K
R5: 5K
R12: 50K
R14: 100K
R15: 100K
R16: 100K
R20: 1M Log (A)
R21: 10K Log (A)
C1: 680nF
C2: 100nF
C3: 4.7nF
C6: 22nF
C10: 470pF
C13: 470nF
C8: 4.7μF
C9: 100μF
D2: 15v Zener
Q1: 2N5486
1 jumper wires
6 trace cuts


Click here to see the bill-of-materials as a list or download it as a comma separated values file (.csv).


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n00b question

You mention a possible mod for several resistors. Let's take R1 as an example. Would such a mod entail changing the value of R1 to for example 100K? Or even 22K? Is that what will influence clipping behavior? Or do I fit a 50K pot?


At this point, I can't tell you anything other than to 'experiment' with it! I built it once, it works fin, but came to a conclusion I like diode/opamp clipping more ...

The effect eventually got recycled ;)

Experiment it is!

Thanks. I was just asking to make sure I wouldn't cause a ThermoNuclear meltdown... ;)

this looks awesome

Do you have any sound samples of this? Is it kind of like a fuzz and tube overdrive combined?
I have been trying to build a Valvecaster today, but I am still waiting on for the correct parts to arrive in the mail. I hope I can figure out what I am doing wrong with a larger breadboard.

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