What's a good 2SC2389 replacement?

[jimosity]

Would a 2N5089 (or possibly an AC128) be a good replacement for a 2SC2389?

I'm looking for something to use for Q1 & Q3 in a Vox Valvetone V810.
Looks like Q2 and Q4 are 2SC1815; which seems to be able to use a 2N5089 as a replacement...would be nice if all four are the same (5089).

[JDoyle]

It is the input buffer and nothing about it is unique to that transistor.

That said, it IS a low noise type - as well as high voltage but at 9V, we can ignore that little tidbit...

The main thing about that circuit, at least from the one I looked at on the web, is that the input biasing network is rather high resistance. Whatever you replace it with, you will want a high gain type.

DO NOT use an AC128, unless you feel like changing that input biasing network - and it's just a buffer, so in my opinion it would be a waste of time. Whatever subtle changes you accomplish once you get it working, will be completely obliterated by the clipping in the next stage.

In short - I'm 99.9% sure that you will be fine with a 2N5089/MPSA18. Just don't use a PNP germanium. You will get it up and running that way. If you want to concentrate on getting low noise (again obliterated by the diode clipping so IMO kind of a pointless pursuit) scale down the input biasing network and use a 2N4401.

Good luck!

Regards,

Jay Doyle