Oh, I used the wrong tag, @bjf

Postad av: @georgeh

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Hi @björn 
Im looking at adding a bias pot for your Bone Bender 2 kit, to get a more gated sound and maybe overbias the transistor for a fuller sound. Basically some some diffrenet textures. Is this possiable with your design and which pot value should I use and connect it to which trimpot? T1 or T2?

Thank You and Happy New year! 
George

Hi There George,

And a happy new year to you

I think what you'd like to do is much easierly done with Bone Bender 1 since you would allready have the trimpots to do it and then also set similar response to Maestro FZ1/A.

On The Bone Bender 2 partly the servo action of the current input voltage output stage ( T2 T3 somewhat negates this) but if the transistors used have enough leakage it can be done with TR2 trimmer.

About fuller sound at over bias:

Consider that amplification is roughly gmxRC for a bipolar transistor: one could say lower current gives higher amplification.

However considering that just about all NPN germanium transistors were made primarily for complementary push pull stages so definitely  higher current could be run through the stages. Gains tend to be lower at higher currents though.

The design however I primarily thought about battery operation and high gain and also to set design center so

it would be an easy build to get working.

Another thought is that if you want a gated sound you can use a pair of antiparallel germanium diodes in series with connection from output on pcb to Volume control; you can also parallel this diode pair with a reverse log say 500K pot to set depth of gating.

This circuit will work as noisegate and signals below threshhold of the diodes will be cut off. The 500K C pot will if used partly be able to shortcircuit the noisegate so it is out of circuit as well as setting the depth of gating

What you ask for is anyhow intersting and I will have a look at it and also that with possible compression at high current if the battery operation option is excluded.

Have fun

BJ

@bjf Thanks for your answer.
All the best

George

Interesting idea! A bias pot on T2 would likely have the biggest impact on gating and texture. I’d start with a 10k–20k pot and experiment carefully. Curious to hear what settings work best.

I’d be interested in this as well. Adding adjustable bias sounds like a great way to unlock extra textures. Has anyone experimented with T1 versus T2 and found which gives the most noticeable results?