Chop shop BJT transistor

[almondcity]

I recently built one of these pretty much to stock with the only difference being this final BJT I used a 2n3904 in place of the 2n2222, figuring it wouldn't make much difference. However, it ended up having much less gain than another one I built with the 2n2222. How critical is this part or was it just some bad jfets?

 

[owlexifry]

difference being this final BJT I used a 2n3904 in place of the 2n2222, figuring it wouldn't make much difference. However, it ended up having much less gain than another one I built with the 2n2222. How critical is this part or was it just some bad jfets?

shouldn't really make much difference as Q3 is mostly an output buffer

the trimpot settings and JFET selection would have a greater impact IMO

 

[Einzeln]

I build 2 chopshops without measuring jfets.
There is a difference in gain between them

 

[Feral Feline]

The 2N3904 is a good sub for the 2N2222, their hFE are very similar (up to about 300 max, average hFE IDK).

Pull out their datasheets and compare.


What makes you think you had a bad JFET? Did you take any measurements before soldering them in?
They're notoriously finicky, another great case for using sockets 'til you find "the one" and then solder in one of its legs into the socket.

 

[PedalBuilder]

It wouldn’t hurt to post a picture of the inside of the pedal. There are a number of other things besides the semiconductors that could cause the same issue.