Tube Cricket Schematic

[dano12]

I've been tinkering with extending the Noisy Cricket amp with a full three-knob tone stack (most likely the classic Fender circuit). Given the loss of the tone stack, I'll need some gain recovery. A good friend shared his tube-preamp design with me and I've worked that into the front end of the circuit.

Before this goes on to the breadboard, any obvious problems or comments?

[Peter Snowberg]

R5 is unnecessary, the ground of the LED does not need to be switched (so you can use a SPST for power), there should be a cap in series with pins 1 and 8 of the 386 (see the datasheet), and I question the value of C5 (seems a little small) but that's just a guess.

Build away! Everything seems to be there.

Be sure to try out a bunch of different tubes in there. The differences can be startling. I did find that I liked the tone of tubes with larger plate structures more, especially when running at low voltage.

[dano12]

R5 is unnecessary, the ground of the LED does not need to be switched (so you can use a SPST for power), there should be a cap in series with pins 1 and 8 of the 386 (see the datasheet), and I question the value of C5 (seems a little small) but that's just a guess.

Build away! Everything seems to be there.

Be sure to try out a bunch of different tubes in there. The differences can be startling. I did find that I liked the tone of tubes with larger plate structures more, especially when running at low voltage.

Thanks much. I've updated the schematic.

A few questions: first, I've never been able to hear any difference in the LM386 with or without the cap in the gain loop. Any ideas why it is recommended?

Second, what you suggest as a good starting value for the 330pf cap?

Thanks!

[mjones99]

the first stage cathode bypass capacitor is one of the most important tone shaping elements in a tube amp, typically that value goes from .68uf to around 25uf or even higher, it increases gain yes but also works like a fixed shelving bass control, the smaller the cap the higher the freq of the shelf.