en NPN Germanium transistor list for Fuzz pedals

Updated on January 31, 2020 | 4833 Views No Category
6 on January 22, 2019

My interest in fuzz pedal came from JMI Tone Bender III reissue which belongs to a friend. this pedal has 3 of OC75 glass tube transistors.

And, unfortunately, My Sola Sound Bum Fuzz came with 3 of NPN transistors while OC75 is PNP type. then found this web page with germanium and silicone transistor lists


There are 26 of germanium NPN transistors from the data sheets

ASY28, ASY29

2N388, 2N388A

2N1302, 2N1304, 2N1306, 2N1308,

OC139, OC140, OC141



NKT713, NKT773, NKT774, NKT781


Black glass tube NPN transistors are OC139, OC140, OC141 from them.

OC75 is like this according to this web page on alltransistors.com

Type Designator: OC75 (PNP)

Maximum Collector Power Dissipation (Pc): 0.125 W

Maximum Collector-Base Voltage |Vcb|: 20 V

Maximum Collector-Emitter Voltage |Vce|: 20 V

Maximum Emitter-Base Voltage |Veb|: 10 V

Maximum Collector Current |Ic max|: 0.01 A

Transition Frequency (ft): 0.1 MHz

Collector Capacitance (Cc): 50 pF

Forward Current Transfer Ratio (hFE), MIN: 55

And, for OC139, OC140 is

Vcb: 20 V / 20 V

Vce: 20 V / 20V

Forward Current Transfer Ratio (hFE), MIN: 40 / 75

I’m going to try OC139. simply beccause, OC139 is cheaper than OC140 on ebay. and I’m wondering how Transition Frequency differences work with Fuzz. I’ll update in a few weeks

  • Liked by

Be the first to post a comment.

Add a comment

5 on January 29, 2020

you haven’t done this yet have you????!!!! 

on January 30, 2020

I’ve done like this

I just tried this from a hunch while I barely understand electric circuits. Bum fuzz was made after B&M fuzz. it came from Tonebender Jumbo, and Jumbo came from Big muff. and they are not far from Tonebender MK3. it means this pedal would work with Germanium transistors. Sola Sound make 3 different versions of Bum …


on January 30, 2020

It looks great! Did you rebias the collector in the transistor? What is the hfe (gain) of your OC139s? The original transistors had a minimum hfe of 130. OC139 has a minimum of 30 hfe. Did you notice a drop in distortion? Is it a gated fuzz sound?

on January 30, 2020

I got the OC139 transistors from this ebay UK seller. and he put hfe on the package. I’ve tried more than a few of them and followed the hfe of ZTX109’s. can’t remember the final setup but it turned out a very nice high gain germanium fuzz after all. 

it sounds pretty close to this one

http://www.bearfootfx.com/fuzz/ The Gated Apple Fuzz is a further take on the Candy Apple Series. This one adds the ‘N’ or Nature control to allow gating, oc…

and unfortunately, I don’t know how to bias the collector and I didn’t it of course.



on January 30, 2020

That is great!! Wonderful job!

on January 31, 2020

I think I still have some OC139. let me know if you need them

Show more replies
  • Liked by
Loading more replies