Author Topic: TS 9 - drive pot does nothing  (Read 906 times)

antonis

Re: TS 9 - drive pot does nothing
« Reply #20 on: February 08, 2021, 06:30:17 AM »
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..
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

iainpunk

Re: TS 9 - drive pot does nothing
« Reply #21 on: February 09, 2021, 02:23:24 PM »
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
half man - half snail - 6 feet to scale - Snail man's - not frail - He's been - to jail - snail man is fuccing real
『snailpilled』

Arangonix

Re: TS 9 - drive pot does nothing
« Reply #22 on: February 09, 2021, 04:42:41 PM »
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

Re: TS 9 - drive pot does nothing
« Reply #23 on: February 09, 2021, 04:48:31 PM »
I +1 to adding an Si in series with a Ge. It'll be a bit louder too!
Croeso i Diystompboxes.

antonis

Re: TS 9 - drive pot does nothing
« Reply #24 on: February 09, 2021, 05:25:21 PM »
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..)
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

Arangonix

Re: TS 9 - drive pot does nothing
« Reply #25 on: February 09, 2021, 05:55:56 PM »
Nice conclusion, antonis. I think I should foresee that while building this TS :D