Building Aft Preamp, question on transistor substitute

[rsvaughnua]

Hi all, I am working on building an Aft Preamp and when I was going over all my parts I had a transistor set aside for this build I thought was a npn ge but its actually a pnp ge. I looked again and I did not have any npn ge transistors on hand. My question is can I replace that npn ge with a similar silicon npn transistor? I am assuming the answer is no but I did want to ask here incase my understanding of this is incorrect in that there would have to be more modifications to the resistors in the circuit to go with a silicon npn. I do have some 2N3904 's, 2N5088 's, 2SC381 's and some 2N2222A 's on hand but all the ge stuff I have is pnp.

The npn ge listed in the build doc is an OC139

 

[Cybercow]

The OC139 is a low gain (~20) Ge NPN BJT and as such may require different biasing to accommodate a silicon replacement.

 

[Chuck D. Bones]

The answer is "Probably yes, but the tone may change and you will have to tweak the biasing." These days people put Ge transistors in guitar equipment for a couple of reasons:
a) Marketing.
b) Ge has a different tone than Si. Depending on the circuit, that difference can be subtle or pronounced.

I have a question of my own: How about sharing the schematic?