Author Topic: How much is to low hfe  (Read 392 times)

spoontex

How much is to low hfe
« on: June 26, 2022, 04:39:23 PM »
Hi,

I've some good germanium transistors with a low hfe, 40 more or less. This are good for Q1? or are they to low?

Thanks!

antonis

Re: How much is to low hfe
« Reply #1 on: June 26, 2022, 04:53:51 PM »
Supposing "Q1" is refered on Fuzz Face 1st BJT.. :icon_wink:

http://diy.smallbearelec.com/HowTos/FuzzFaceFAQ/FFFAQ.htm
"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..

cspar

Re: How much is to low hfe
« Reply #2 on: June 26, 2022, 11:55:21 PM »
And then there is also this useful bit of information from the Small Bear "Deep Cave".

http://diy.smallbearelec.com/HowTos/BreadboardGeDarlingtonFFs/BreadboardGeDarlingtonFFs.htm

mac

Re: How much is to low hfe
« Reply #3 on: June 27, 2022, 09:16:06 AM »
You can make darlingtons or cascade 3-4 stages.
I tried hfe 30-50 in Tone Bender 2 & 3 and they do fuzz.
In a FF it could be a good thing for a blues man. Salt and pepper to taste  ;D

mac
mac@mac-pc:~$ sudo apt-get install ECC83 EL84

spoontex

Re: How much is to low hfe
« Reply #4 on: June 30, 2022, 02:33:28 AM »
Thanks.

https://www.electrosmash.com/germanium-fuzz

This guy talk about hfe >60 and adjust them with trimmers. Does the fact that it uses trimmers make hfe not so crucial? 

cspar

Re: How much is to low hfe
« Reply #5 on: June 30, 2022, 11:50:49 AM »
You can say it like that but really it's more that it is easier to set or adjust the bias with a trim pot than with a static resistor as well as making the range of transistors you can use larger.

Essentially, you get better results by biasing the transistors with the circuit then you will trying to bias the circuit with the transistors. And this is regardless of the values, within reason.

Vintage FF's weren't all built with ideal transistors. People used to sort through a bunch of FF's to find one they liked the sound of. If those same FF had bias pots in the design people wouldn't have sorted them at the music store as much.

I personally don't put much faith in static resistors for biasing germanium transistors and prefer builds with both rough internal and fine external biasing and always socket the transistors.