Help Me Decide

[crawler486]

My electronic supply store has no stock of MPSA18 transistor.

What they have are MPSA13 and MPSA20.

MPSA13 is 30 Volts and MPSA20 is 40 Volts.

Can I use anyone one of them as alternative? Which one?

The transistor is going to be used for my WAH FX project.
I'm also having a hard time looking for the 500 MH inductor.

Please help. Thanks

[jimmy]

i think i use MPSA13s. they work as well as could be expected!  for the Inductor, use on side of those little 1k:8ohm transformers.

cheers
Jim

[Arno van der Heijden]

The MPSA13 is a darlington, so it won't work.

The MPSA18 is a high gain transistor. It is assumed that transistors with lower gain sound better if you're aiming for a vintage sound. Try BC109b for example.

Some more information here:
http://fuzzcentral.tripod.com/mckoy.html

[Travis]

The MPSA13 is a Darlington tranny, is it not?  

The MPSA20 has an hfe of c. 400, if I recall correctly.  That should be about right.

edit: too late

[Jered]

2N5089 is also a suitable replacement for an MPSA18.
 Jered

[crawler486]

Thanks guys.

These are the available inductors they have.
Can I use of of these instead of the 500mz

Inductors (choke coil)
2.7 uH
10 uH
18 uH
33 uH
47 uH
100 uH
18 mH


How do you read mH? Is it megahertz?

[petemoore]

A VOX inductor and it works ok, I've been actually able to use it and work around the midrange homp...
 Still I'm thinkin of going to a Red Fasel or Clyde inductor for it.
 It came with MPSA18 transistors, that's what's in there.

[Joep]

Inductors (choke coil)
2.7 uH
10 uH
18 uH
33 uH
47 uH
100 uH
18 mH

Forget it, much to low.....

mH = milli Henry

[Mark Hammer]

As RG Keen notes, the 1k:8R interstage-matching transformer that Radio Shack sells/sold provides a suitable inductance.  See his wah document for what leads to use.  I picked up some nice ferrite inductors that look similar to the Fasel with a niminal 900mh inductance and a tap at around 700mh or so and they work just fine.

[Phorhas]

Hey there...

Let's start with the inductor - I suggest the Halo replica from: http://www.wah-wah.co.uk - a wonderful site and a wonderful inductor (I used it to replace my 535Q original inductor) truely a great waaaaaahhh vibe.

and about the tranny I would go for the bc109 as well for that vintage tone or maybe even an ac187c Ge tranny for that vintage feel