# Swapping germanium transistors for silicon



## 117mateo (May 9, 2021)

Coming from a poor man who enjoys this hobby..

I'm wanting to pick up some germanium based fuzzes, namely the tone bender mki and the hoof/reaper, however germanium transistors seem to be extremely difficult to come by, and where they are, seem extremely expensive for what they are. So the question is, is it possible to just sub out germanium transistors for silicon, and just re - bias them to account for leakage?

To my understanding, the biasing of the tone bender's transistors is set to account for the leakage, meaning that it can be re - biased for low - leakage silicon transistors with a similar hfe, right?


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## giovanni (May 9, 2021)

I think it’s possible to do that for some designs but it will require to change a lot of components in the circuit. Some designs may not be adaptable at all, but that’s just my hunch. Also, it will lead to a completely different sounding pedal. Better to get a circuit designed for silicon right off the bat instead.


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## Leftovernoise (May 9, 2021)

I don't know enough about swapping germanium for silicone, but I'll just note that pedalhacker usually has a bunch of nos parts. Just looked and they have a few different types of vintage germanium transistors for $3ish usd. And I think they have a testing fee you can request to make sure you're getting a specific gain range that will work for your build. Yes it's more expensive than purchasing a silicone transistor for .50-1.50 each, but considering that most of those old fuzzes only have a small parts list anyway,it would still be a pretty inexpensive project. Just a thought!


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## Big Monk (May 9, 2021)

117mateo said:


> Coming from a poor man who enjoys this hobby..
> 
> I'm wanting to pick up some germanium based fuzzes, namely the tone bender mki and the hoof/reaper, however germanium transistors seem to be extremely difficult to come by, and where they are, seem extremely expensive for what they are. So the question is, is it possible to just sub out germanium transistors for silicon, and just re - bias them to account for leakage?
> 
> To my understanding, the biasing of the tone bender's transistors is set to account for the leakage, meaning that it can be re - biased for low - leakage silicon transistors with a similar hfe, right?



You can sub Silicon transistors in any of the old fuzz circuits with some tweaking but Germanium responds differently and with different distortion characteristics than Silicon. 

With that said, I love both Silicon and Germanium circuits. And hybrids.


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## zgrav (May 9, 2021)

silicon fuzzes sound different than germanium fuzzes.  it is the type of transistor that is mostly giving the character to the fuzz box.   so subbing silicon into a circuit for a germanium fuzz and getting it to work will not give you something that sounds different.  

there is an interesting fuzz design I built recently that uses four silicon transistors to aim for a germanium fuzz sound.  interesting build and I like the pedal.  http://tagboardeffects.blogspot.com/2012/06/npn-silicon-fuzz-face-germanium.html


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## bifurcation (May 9, 2021)

zgrav said:


> there is an interesting fuzz design I built recently that uses four silicon transistors to aim for a germanium fuzz sound.  interesting build and I like the pedal.  http://tagboardeffects.blogspot.com/2012/06/npn-silicon-fuzz-face-germanium.html


This looks fascinating. I totally want to try this.


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## phi1 (May 10, 2021)

zgrav said:


> silicon fuzzes sound different than germanium fuzzes.  it is the type of transistor that is mostly giving the character to the fuzz box.   so subbing silicon into a circuit for a germanium fuzz and getting it to work will not give you something that sounds different.
> 
> there is an interesting fuzz design I built recently that uses four silicon transistors to aim for a germanium fuzz sound.  interesting build and I like the pedal.  http://tagboardeffects.blogspot.com/2012/06/npn-silicon-fuzz-face-germanium.html


I just finished this one, was very intrigued by the idea. Have you compared it to a Ge fuzz face?  I A/B’d it with my Ge fuzz face. Measured the transistor pairs before building to determine the resistance to get the HFe’s to match my GE build. Played with those 47p caps, ended up with 150p but still experimenting.

anyway, it’s sounds pretty great. Sadly the Ge version still sounds a bit different to me (rounder, squishier, something like that). I was really hoping I could match the sound exactly, but was not surprised that this was the case. But, it is still an incredible fuzz and quite close to the Ge. Curious to hear of other experiences, there seem to only be a few completed builds discussed on the threads about this project.


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## HamishR (May 11, 2021)

Well Ge transistors leak, and that can be a big part of why some fuzz circuits work with Ge but not so well with Si. I have had good results in some circuits by subbing low-gain Si trannies for Ge. I've used some very old 2N3903s and 2N2222As. Of course with older transistors noise can become an issue, but if you replacing germanium perhaps not such an issue!

My most successful use of Si instead of Ge has been in the Red Rooster (Chickenhead) treble booster. I still need to modify the circuit a bit to roll-off some of the treble but by using a 2N2222A with an hfe under 160 I have made some great sounding Red Rooster pedals. And no need for the reverse polarity chip either.

Germanium does have some sounds which are difficult to get from silicon but it's not impossible to get close enough. Ge cleans up from the guitar better than Si in general which can be difficult to replicate, but a tone control or some kind of treble snubber in the circuit can help a silicon pedal sound more Ge. Get a transistor power rating meter to measure the hfe of your trannies and by using really low hfe transistors you might get closer to that Ge sound.


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## Big Monk (May 11, 2021)

The big difference between Silicon and Germanium transistors is the way in which they transition into clipping. Biasing a vintage circuit with Silicon transistors subbed in is almost an afterthought.

What's hard to replicate is the softer clipping and transition to clipping. Vintage circuits like the Fuzz Face, Rangemaster and Tonebender often have a harder edge and less touch sensitivity with Silicon transistors. 

With that said, careful biasing and frequency shaping mods can really turn a Silicon based circuit that was originally designed around Germanium into a monster.


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## Chuck D. Bones (May 11, 2021)

Big Monk said:


> You can sub Silicon transistors in any of the old fuzz circuits with some tweaking but Germanium responds differently and with different distortion characteristics than Silicon.


Sometimes a whole lotta tweaking is req'd just to get sound to pass thru.  I agree that Ge & Si sound different in most circuits.  Pedalhacker & Small Bear are reputable Ge suppliers, just keep in mind that the GE transistors they sell have been out of production for decades and the supply can't always keep up with demand.  Also, it's not enough just to buy the same part number transistor that was used in the original vintage pedal.  Ge transistors have to be tested and selected for the particular circuit.


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## Big Monk (May 11, 2021)

Chuck D. Bones said:


> Ge transistors have to be tested and selected for the particular circuit.


I agree and should have made this clear. 

Any generalities about Vintage Dirt comes with the assumption that you have taken the time to select the transistors and tested them for Noise, Leakage, etc.


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