2N7000 Drive

Vitallka · Post by **Vitallka** » 20 Apr 2023, 18:45

Добридень or hello everyone!
I decided to make an overdrive on 2n7000, because apart from Zvex SHO, I no longer met the use of these transistors in guitar circuits. The circuit is built on 3 transistors, a green LED is used for bias.
At first, I designed the circuit in LTSpice, but then I adjusted the sound by ear.
I don't play the guitar well, but you can get some ideas about the sound from the video

I also speak Ukrainian in the video, so maybe not everyone will understand

The initial scheme sounds like this:

Schematic https://imgur.com/SCwqaGR

The changed scheme sounds like this:

Schematic https://imgur.com/qg6GOtK

Perhaps there will be some more changes in the scheme, so this is not yet the final version

Manfred · Post by **Manfred** » 20 Apr 2023, 19:01

it sounds to me like an overdriven tube power amp, not bad.

Vitallka · Post by **Vitallka** » 20 Apr 2023, 19:15

Manfred wrote: ↑20 Apr 2023, 19:01 it sounds to me like an overdriven tube power amp

It's probably because I used to try to do something in guitar tube circuits - some amplifiers and preamps. Therefore, the tube sound has been put aside in the head, and in new developments the ears try to hear something close to the tube sound

blackboarcult · Post by **blackboarcult** » 22 Apr 2023, 06:54

Nice one! Would it take 18 or 24V well, or would it need a different biasing?

Vitallka · Post by **Vitallka** » 22 Apr 2023, 11:19

No, the bias does not need to be changed, because at 1.8V on the gate, the 2n7000 will be open at any supply voltage. At higher voltages, you may have to increase the resistance of the positive resistor to the green LED to limit the current through the LED.
And even at higher voltages, the sound will be better

blackboarcult · Post by **blackboarcult** » 22 Apr 2023, 12:20

Thanks, Vitallka. I am currently breadboarding loads of preamps running at higher voltage for an SS amp build, but I'm getting sick of finicky jfets. I might try yours soon!

Vitallka · Post by **Vitallka** » 26 Apr 2023, 17:35

Continuation of experiments on overloading.
I came up with the idea of putting a zener diode from the drain to the gate - the simulator showed the rounding of the upper half-wave of the output signal (the corners of the rectangle are rounded). As a result, the sound became much soft

https://imgur.com/s2TcWEt