Reverb driver/recovery

[Leevi]

I'm planning to build a Blues Jr. type amp and thought to use 3 preamp tubes which means
that some extra amplification is needed in order to implement one tube reverb.


I thought to implement either the reverb driver or recovery circuit by using LND150 Mosfet.


My question is which one of those is recommended to be implemented with the fet, driver or recovery?


/Leevi

[d95err]

A FET should be ideal for the recovery stage. This is just clean amplification of a very weak signal; no clipping involved. The fet should provide a good low noise amplification.

[Leevi]

Thanks d95err
And it provides more gain.
/Leevi

[Bieworm]

You have to consider the PT for that project too. There should be enough current for the mosfet.

[Leevi]

You have to consider the PT for that project too. There should be enough current for the mosfet

Good point, it probably takes ~30mA. That can be an issue in the PT I have planned to use.


/Leevi

[Soulfetish]

This is a 1 tube reverb I designed to go in my buddies Silvertone 1474 to give you some ideas. It uses a 6U8A Pentode/Triode tube with the Pentode used as a CCS driver and a hybrid cascode as a really low noise, high gain recovery stage.

[tubenit]

I would love to hear a sound clip or YouTube of that "one tube reverb".  I like innovative ideas and this looks great!


Can you share a sound sample of the reverb, please?


With respect, Tubenit

[pdf64]

This is a 1 tube reverb I designed to go in my buddies Silvertone 1474 to give you some ideas. It uses a 6U8A Pentode/Triode tube with the Pentode used as a CCS driver and a hybrid cascode as a really low noise, high gain recovery stage.

Nice! What spec tank?

[Leevi]

This is a 1 tube reverb I designed to go in my buddies Silvertone 1474 to give you some ideas. It uses a 6U8A Pentode/Triode tube with the Pentode used as a CCS driver and a hybrid cascode as a really low noise, high gain recovery stage.

Very interesting! The tank should probably have high impedance?


/Leevi

[pdf64]

…The tank should probably have high impedance?

Yes, I suspect it would work best with the highest impedance drive coil available.

I wonder what the gain of the cascode stage is?

[Leevi]

I used the following setup because of limited resources.
I had 1/2 12AX7 free. It works excellent, very low noise even if the reverb is fully open.

Longer reverb can be reached by changing the 470K resistor from the reverb pot lower e.g. to 220K or 270K.

/Leevi