Transistors - is hFE the only number that matters?

[DAJE]

I needed some 2N5089s, for a Carcass build.

Couldn't find any at the usual places, so I looked for some subs.

I checked my stash and I have a bunch of 2N5088s, so that's just one less, right?

Also bought some MPSA18s from Tayda after I saw them recommended somewhere on this forum.

Then I did find some cheap 2N5089s on AliExpress (from a seller I've bought from and had good results with before) so I bought a bunch of them too. They arrived today and I've been testing and comparing.

The AE 2N5089s are around hFE 350
The 2N5088s are around hFE 300
The MPSA18s are around hFE 800
(I tested 3-5 of each, not all of them.)

So, the question is the title. In pedal terms, and particularly dirt pedals, is the hFE all that matters? Or is there some other meaningful number (or numbers) I should also be aware of? Given that I'm really not a numbers guy and that I only have a simplistic grasp of what's going on with transistors anyway. And really all I care about is whether the pedal sounds good or not.

 

[Coda]

Generally, transistor substitutions are easy. All you have to do is find something with similar specs. 5088’s would work well in the Carcosa. 2n5089 are the same thing, just rated for a higher hfe. Sometimes, the difference between hfe measurements makes a difference, sometimes it doesn’t. At the same time, with some circuits, you have to consider things like leakage…which is why those circuits usually have a way to set the bias correctly (like a trimpot, though all transistors have their bias set via resistors). One thing to keep an eye out for is pinout. Not all transistors are laid out the same. It just so happens for you that 5088, 5089, and MSPA18 are all EBC, so you could swap them in and out and choose what sounds best to you…because sometimes it’s not a numbers game, but a personal preference.

The most important thing about transistors in a drive/distortion/fuzz circuit, in my opinion, is that you use sockets. A great way, sometimes, to liven up an unimpressive pedal is to start swapping out transistors. Sometimes, though, it makes no difference. In short, generally, any transistor can sub for any other, as long as you are swapping npn for npn/pnp for pnp.

Jfet’s are a different story…

 

[DAJE]

Thanks Coda, that's what I thought, just wanted to be sure there wasn't some important information I was missing. I'm a socket fan for most things, in fact I just received 400 (10x40 strips) SIP sockets today. I won't be running out of those for a while.

 

[Barry]

Sockets are great, but once you've got it down to the one you want I find it best to solder in at least one leg

 

[DAJE]

Sockets are great, but once you've got it down to the one you want I find it best to solder in at least one leg

Most of my pedals are home use only, the fuzzes I've made for other people get soldered transistors. My only gigging band at this point is the one where I play uke bass (see avatar pic) and lap steel, and I only use a bit of delay/reverb for the steel.