# Transistors for fuzz pedals?



## Username123 (Aug 23, 2021)

I just wanted some info on transistors in fuzz pedals. I know nothing about the gain you want or matching transistors or stuff like that. If someone could give me a complete rundown of transistors in fuzz pedals, I would appreciate it greatly.


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## Big Monk (Aug 23, 2021)

Username123 said:


> I just wanted some info on transistors in fuzz pedals. I know nothing about the gain you want or matching transistors or stuff like that. If someone could give me a complete rundown of transistors in fuzz pedals, I would appreciate it greatly.



Depends on the pedal. Do you have one in mind?


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## Username123 (Aug 23, 2021)

Sandspur maybe. Also curious about the transistors for the fuzz foundry deluxe.


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## Big Monk (Aug 23, 2021)

Username123 said:


> Sandspur maybe. Also curious about the transistors for the fuzz foundry deluxe.



It would depend on whether you decided to go true high gain silicon Fuzz Face with the BC108, medium gain or low gain modeled after something like then Fuzz Central Axis Face, which mimics the characteristics of the Germanium units with Silicon.  

Medium gain I’d probably go for approximately Q1 = 120 hFE/Q2 = 200 hFE.

Low gain I’d probably match the germanium values at approximately Q1 = 70-80 hFE/Q2 = 110-120 hFE.


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## Username123 (Aug 23, 2021)

I don't really even know what the hFE means or how to match them. I know almost nothing about transistors.


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## peccary (Aug 23, 2021)

There is a lot of good knowledge on this board already. I would try searching first and then maybe trying to get a bit more specific with what you are looking for. 

Just to start you off, do a search for "tone henge" and check that thread out. @thewintersoldier spent a lot of time puting some good info there and it's a good starting place. Lotsa good stuff here - poke around and read a bunch of threads.


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## Big Monk (Aug 23, 2021)

Username123 said:


> I don't really even know what the hFE means or how to match them. I know almost nothing about transistors.



hFE is the current gain or amplification factor of the transistor. Short version: it’s the factor or ratio of the current entering the base versus the current exiting the collector or emitter. 

Grab yourself one of these and test away!:






						Amazon.com: LCR-TC1 Colorful Display Pocketable Multifunctional TFT Backlight Transistor Tester for Diode Triode Capacitor Resistor Transistor LCR ESR NPN PNP MOSFET : Industrial & Scientific
					

Buy LCR-TC1 Colorful Display Pocketable Multifunctional TFT Backlight Transistor Tester for Diode Triode Capacitor Resistor Transistor LCR ESR NPN PNP MOSFET: LCR Meters - Amazon.com ✓ FREE DELIVERY possible on eligible purchases



					www.amazon.com


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## Coda (Aug 23, 2021)

https://forum.pedalpcb.com/threads/whats-all-this-hfe-stuff-about.4537/


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## Username123 (Aug 24, 2021)

Ok. I don't know how I would determine what is an acceptable he range for individual pedals. I probably can't do either of the methods Chuck described.


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## Feral Feline (Aug 24, 2021)

As you may have surmised by now — there is no one-stop drop & complete rundown of transistors in fuzz pedals. 
Any that claim to have such, I bet you could still find plenty missing from their rundown.

There is simply too much information out there, and too many fuzz circuits to explore. The best approach I can suggest is to pick one particular fuzz pedal that you liked the sound of, in demos and in songs you've heard or from playing a friend's or in-store demo unit. Then analyse that particular circuit. Find as many variants of it as you can, learn/try-to-figure-out why somebody chose to build their variant the way they did — perhaps parts are obsolete, so a near substitute was found; maybe the builder prefers the tone or the affordability of easy-to-find inexpensive off-the-shelf parts for his/her build. 

On your build journey you'll pick up info and learn more by doing and exploring — and retain it — than if someone had given you a complete rundown.

Enjoy your journey...



High gain
Low gain

Silicon
Germanium

Expensive
Cheap

Rare 
Common

Smooth
Spitty

Organic
Velcro

single, double, triple, quadruple...


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## thesmokingman (Aug 24, 2021)

even analogman has multiple choices for the sandspur ... right now you can get perfectly good TFK transistors from smallbear in bc108B, 108C, and 109C and all of them are going to sound good ... they're fairly consistent so you can gain match them if you want to or you can just throw them in and drive on down the road ... as far as fuzz factory goes most zvex are either ac128 or 2n404 ... and that's probably changed over time as the supplies dry up. I've bought a few sets of zvex branded 2n404 off ebay when I  could find them and they're good in either the factory or a regular fuzz face


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## Username123 (Aug 24, 2021)

Thanks for all the info guys! I will do more research.Thankfully out of production and rare parts is not always a problem for me...


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## Big Monk (Aug 24, 2021)

My opinion is you should get a breadboard and the tester I linked to in Post #7.

The breadboard is the Fuzz Head's best friend!


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## Username123 (Aug 24, 2021)

I have a tester that looks just like that. I don't have a good breadboard though. Any suggestions?


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## Big Monk (Aug 24, 2021)

Username123 said:


> I have a tester that looks just like that. I don't have a good breadboard though. Any suggestions?









						Breadboards - Hardware
					






					www.taydaelectronics.com
				




Any of those will do but go bigger or use multiples. PedalPCB has a few options but this is the most comprehensive and I think I'll be retiring "The Prototyper" (my Breadboard environment) soon in favor of this:









						ProtoBoard - PedalPCB.com
					

Integrated Prototyping Board




					www.pedalpcb.com


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## ntuncer (Jan 3, 2022)

Hello all,
I am planning to build Sandspur and my aim is to get as close as Analogman's Sun Face silicon tone. I tried to search on forum first to find some information about how to pick right transistors according to hFE values for Q1 and Q2 but couldn't find it. My target transistors are *BC108C *and *BC183*. Could you please help me to clarify the points below?

My knowledge of hFE range of BC108Cs are between 400 and 800 in that case, is it possible to build only high gain fuzzes?
What should be the Q1 and Q2 hFE values? I think that Q1 value should be less than Q2 but what should be the differences between Q1 and Q2 Ex: Q2= Q1+100hfe?
Another option is don't bother with buying big quantity transistors and buy matched BC108 transistors and pay around 14$ per set.

My knowledge of hFE range of BC183s are between 40 and 800. In this case can I use them to build low or medium gain germanium like fuzzes or I have to buy big quantity of them to pick the right ones which is almost impossible solution?
As we are talking about silicon transistors, is it suitable to use LCR-T4 meter to measure them? Can I ignore the leakage?





Cheers


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## mdc (Jan 3, 2022)

The best (and probably only) way to match a BC109 sunface would be to have the real deal in front of you and swap transistors around in your circuit until it clicks. 

Also, the BC549C is about 1/10th the cost of a metal can BC109C, and is afaik the exact same transistor in a different case with tighter specs and lower noise. They sound fantastic in pretty much every NPN Si fuzz circuit and should work great in anything that asks for a BC109C.

For lower gain transistors, 2N3440 has been a wonderful NPN Si find for me. Consistently in the ~100 range for hfe, and they're a T05 package so you get that metal can ~ v i b e ~.

As always though, the easiest move is to socket the transistors and just plug stuff into it until you're stoked on how it sounds.


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## ntuncer (Jan 21, 2022)

So I bought 30 BC108B silicon transistor and try to measure hfe but it changes a lot when I use  LCR-T4 meter. 310 hfe to 430 hfe. I am reading different values Is it normal? Am I doing something wrong?


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## peccary (Jan 21, 2022)

ntuncer said:


> So I bought 30 BC108B silicon transistor and try to measure hfe but it changes a lot when I use  LCR-T4 meter. 310 hfe to 430 hfe. I am reading different values Is it normal? Am I doing something wrong?
> 
> View attachment 21910



Handling germanium transistors will raise the hfe, any kind of heat will, and they are very sensitive. If you touched the transistor be sure to let it sit for a minute before measuring. 

I will lay them spread out on a table for a while and then use the little lead grabber on my DCA75 to pick them up so I don't touch them.


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## ntuncer (Jan 21, 2022)

peccary said:


> Handling germanium transistors will raise the hfe, any kind of heat will, and they are very sensitive. If you touched the transistor be sure to let it sit for a minute before measuring.
> 
> I will lay them spread out on a table for a while and then use the little lead grabber on my DCA75 to pick them up so I don't touch them.


Thanks but I think that it is not necessary for BC108B as they are silicon and we can ignore the leakage right?


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## peccary (Jan 21, 2022)

ntuncer said:


> Thanks but I think that it is not necessary for BC108B as they are silicon and we can ignore the leakage right?


Yeah, my bad dude. I just assumed germs and apparently need to work on reading posts fully before replying


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## benny_profane (Jan 21, 2022)

ntuncer said:


> So I bought 30 BC108B silicon transistor and try to measure hfe but it changes a lot when I use  LCR-T4 meter. 310 hfe to 430 hfe. I am reading different values Is it normal? Am I doing something wrong?


Is there a reason why you aren’t putting the transistor directly into the ZIF socket?


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## ntuncer (Jan 21, 2022)

benny_profane said:


> Is there a reason why you aren’t putting the transistor directly into the ZIF socket?


Not really I found this way more faster than using the ZIF socket.


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## ntuncer (Jan 23, 2022)

Here  I use 2M2 resistor from base and 2.469K from collector. The voltage I read on 2.469K decrease. Should I wait till to stable? Is it normal? It takes really time to be stable.


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## Username123 (Jan 24, 2022)

ntuncer said:


> Here  I use 2M2 resistor from base and 2.469K from collector. The voltage I read on 2.469K decrease. Should I wait till to stable? Is it normal? It takes really time to be stable.


I can't really help, but this thread is definitely nostalgic. I used to ask some pretty horrible questions a few months ago. I'm glad that you are asking good specific questions. Good luck. I hope you find the information you need. This forum has some really great members, so I'm glad you are getting some help.


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