altering Tone Bender circuit, Germanium to Silicon

[slowpogo]

This may be a bigger question than I realize... but what is involved in changing a Tone Bender circuit from PNP Germanium to Silicon? Is is mostly a matter of changing Collector/Emitter resistor values?

The reason is just that Germanium is so hard/expensive to source and I know silicon fuzz can sound good.

I'm especially looking at the Tone Bender side of this DFX board:

https://drive.google.com/file/d/1zqEsQMVecs1-njY_N86_64nTgSHcTsH3/view

[kaycee]

Not the Darlington type one you posted, which, BTW is probably the most forgiving of the Ge tonebenders.

https://tagboardeffects.blogspot.com/2017/06/silicon-tonebender-mkii.html

[nocentelli]

There are quite a few modern MkII tonebender-type pedals that have been specifically designed around silicon transistors, rather than being simply converted Ge circuits with a few tweaked component values. It might be worth trying a few of these out on a breadboard: The Black Ash fuzz by Earthquaker I tried out only this weekend (pretty decent) and I also liked the Catalinbread Katzenkonig and Skreddy Luna Module. These last two have a few circuit tweaks and some extra features to give a broader range of sounds than a bare bones Si TBMkII clone, but they can be modified to remove the extra controls (or replaced with set+forget trimmers).

[Gus]

Have you seen this?

https://www.diystompboxes.com/smfforum/index.php?topic=114210.msg1059856#msg1059856

[slowpogo]

This link claims that you don't even need germanium in Q1/Q2 in a mkII darlington version

http://fuzzcentral.ssguitar.com/3knob.php

[Rob Strand]

There was also this one with the diode.   


IIRC there was a silicon tone bender (?) thread on this forum.   Someone in the thread says something along the lines that the silicon one sounds pretty good but if you can get germaniums you would go with those.


Maybe this thread?
https://www.diystompboxes.com/smfforum/index.php?topic=81110.0

(There's silicon versions of different versions of the tone bender.  All different circuits.)

[kaycee]

This link claims that you don't even need germanium in Q1/Q2 in a mkII darlington version

http://fuzzcentral.ssguitar.com/3knob.php

I've actually got a vero of the Darlington version Tonebender on the bench at the moment (Park 2 Knob ). When I get the chance I'll pull the transistors (if I haven't soldered them to their sockets already) and pop in a set of silicon transistors and see if it fires up.

You could try building this one and throw whatever Ge's you have available, it seems to fire up with a wide range of the ones I have tried in it.

[iainpunk]

(if I haven't soldered them to their sockets already)

i thought the idea of sockets was that you don't have to solder the component that gets inserted?

cheers, Iain

[kaycee]

So, I swapped out out the Ge's in the Park 2 knob vero for 3906's and it doesn't work at all.

I'd suggest Mictester's version, its close to the Hot Silicon (some controversy back in the day).

https://3.bp.blogspot.com/-9-JCWwhb7dI/T2CnJnCI7hI/AAAAAAAABF4/-NpEXcKcO84/s1600/mictester_silicon_tonebender.gif

I use sockets if I'm likely to try a few transistors, after a few insertions they lose their firm grip so I tag one leg down to make sure they are secure. I don't tag all 3 as they are a pain to de-solder should the need arise.

[Rob Strand]

So, I swapped out out the Ge's in the Park 2 knob vero for 3906's and it doesn't work at all.

The Ge circuits which don't have a resistor from the transistor base to the supply rail don't work well when the Ge transistor is replaced with silicon.     The Ge transistor has leakage and that biases the transistor to some degree, enough to make it work, and in many cases it defines the sound of the pedal.   The silicon transistors have no leakage from a practical perspective.   You would need to add some form of biasing resistor to give them some bias.    Even then the character of the ge version is lost.

In cases where the Ge transistors do have some form of biasing resistor, sub'ing silicons means you need to tweak the biasing resistors since the Ge values are often completely wrong for silicon.

It's best to find some circuits where people have already tweaked the circuits for silicon.

[kaycee]

Thanks, Rob - I wasn't really expecting it to work, even with my limited understanding - but as I had it laying around, it was easy to just try swapping the trannies.

[Rob Strand]

Thanks, Rob - I wasn't really expecting it to work, even with my limited understanding - but as I had it laying around, it was easy to just try swapping the trannies.

If you wanted you could probably get the thing sounding reasonable by tweaking the bias.   

[Big Monk]

I'm especially looking at the Tone Bender side of this DFX board:

https://drive.google.com/file/d/1zqEsQMVecs1-njY_N86_64nTgSHcTsH3/view

That looks like the 3 Knob MKIII circuit, if I am not mistaken. I dont have as much experience with that as I do the classic MKII circuit. Which one are you looking to build?

Since tweaking my Germanium MKII circuit, I have been curious about applying those tweaks and notes to a silicon circuit. 

[dthurstan]

Hi

Here is a schematic for a silicon Mk II I draw up based mainly on John Lyon's Scarab I think. Although I would have looked at Mictester's circuit and the Hot Silicon Fuzz as mentioned above.



As Rob mentioned you have t correctly bias Q1 for silicon, then there are some resistors on the emitters and on the fuzz control too. A lot of silicon fuzz designs require low gain transistors i.e. <100. But I wanted something that worked with more typical silicon gains. I used some 2N3904s in it. They didn't have lots of gain (less than 200), but I think I tried some transistors with a gain of ~200-250 and it still worked.
It's always a good idea to breadboard first and see if it works ok.

I would just like to be clear I'm not claiming this circuit is my own design, I just reworked other peoples ideas to fit what I wanted a basic silicon Mk II.

Thanks
Dave

[Gus]

About the Hot Silicon

Look at the dates when things were first posted

Doug posted the Hot Silicon in 2003 IIRC. Doug put that together with ideas from Aron and myself. So IMO it is more Doug's circuit

Note the resistor values used. I used 10K and 1K etc in the FF like distortion section because at the time I first built the distortion circuit(mid 90s) Radio Shack did not stock values I would have used. This was so people could buy parts at Radio Shack.

Parts for effects were much harder to find 20, 25 years ago.

Look at the values used and compare. I would have used a 2K bias control(Radio Shack did not stock them in the stores) and some other changes.

And I think there was something about the Glass Blower circuit as well

https://www.aronnelson.com/gallery/main.php/v/DougH/fuzz/hotsi/GS_Tonebender.gif.html