TS 9 - drive pot does nothing

[antonis]

Ok, I can see that this circuit doesn't like germanium diodes

Ge diodes behave well in logarithic amps only with signals of very low amplitude..
It has to do with diode dynamic resistance in relation with current flowing through it..

[iainpunk]

Ok, I can see that this circuit doesn't like germanium diodes

could also be the specific ones you have. i have a bunch of different flavours of Ge diodes, some are really leaky, and some are nice and tight.
the really leaky ones can greatly reduce gain in feedback loops, but are generally nice to add in series with Si diodes for a softer knee
my favourites are the Philips AA119, compared to most Ge's, they tend to have a tad higher forward voltage, a really soft knee and next to no leakage at all. they are in this really cool green glass case, with a dark red band on the kathode

cheers, Iain

[Arangonix]

I have dozens of russian D9E ge diodes. I usually use em to stabilize trannies in FF circuits. But they are absolutelly no no for TS I built Will mix em with some Si diodes tomorrow and see what it gives.

[anotherjim]

I +1 to adding an Si in series with a Ge. It'll be a bit louder too!

[antonis]

And will "neutralize" Ge reverse bias leakage current..
(which, IMHO, is the main reason for defeating drive pot responce - there always is a pot parallel "leakage" current through diodes..)

[Arangonix]

Nice conclusion, antonis. I think I should foresee that while building this TS