mpf102 substitutes?

[Marcos - Munky]

I built the Dr. Boogey using J201s, but it have too much noise and gain (never though lots of gain will be a problem to me  ), and screams a lot. I saw a few posts telling that a MPF102 as the first transistor will fix this problem, or at least will help a lot, but I didn't found them anywhere at the local stores. Any suggestions for something I can use instead of the MPF102?

[mac]

I use the BF245A and 2SK117 (high gain) to replace j201.
BF245B or C to replace MPF102.


mac

[Xavier]

2N5457 would be my choice, same pinout as the J201 and no need to rearrange the layout or twisting transistor legs.

[birt]

i allways use 2N5457

[stm]

The 2N5458 and 2N5458 are pretty close replacements of the MPF102 in termos of both Vp and Idss.  In fact, the characteristics of the MPF102 lie in between them, perhaps a little closer to the 2N5458.

The 2N5457 is a good candidate that will be somewhat "hotter" than an MPF102.

[powerplayj]

I tried the 2N5457...less gain but almost the same amount of noise as the J201.  MPF102 is really the way to go.  Seems like I got mine at Radio Shack.

[oldrocker]

MPF102's is all I use.  Why?  It's sold and available at Radio Shack.  I never had too much a problem using this Jfet and it's easy to get.  For me if I can run down to RS and get the parts right now instead of waiting for parts through the mail then that's the pedal I'm building.

[MetalUpYerEye]

So you can build the Dr. Boogey with MPF102's instead of J201's and still get the desired sound?

[Marcos - Munky]

So you can build the Dr. Boogey with MPF102's instead of J201's and still get the desired sound?

Don't know how it will sound with MPF102s, but the build reports said that it sounds great with MPF102 as Q1 and J201s as the other Qs.

[stm]

A first stage with a high Vp FET like the MPF102 makes sense as it has wider input dynamic range without clipping.

For the remaining stages where you want to have gain, the MPF102 will probably be dissapointing due to the poor gain you'll get.

[Bucksears]

I have pretty much [permanently] set my Dr. Boogey with an MPF102 for Q1 and J201s for the rest. All J201s had too much gain and was too noisy, but using MPF102s for both Q1 and 2 cut too much gain, although it cut noise too.

- Buck

[powerplayj]

So you can build the Dr. Boogey with MPF102's instead of J201's and still get the desired sound?

Don't know how it will sound with MPF102s, but the build reports said that it sounds great with MPF102 as Q1 and J201s as the other Qs.

Sounds awesome with less noise than my BSIABII (my experience anyhow).  It absolutely kills with a MOSFET boost behind it too.

[RDV]

Marcos:

Which layout did you use? Because I used a layout at first that did not include a key capacitor. It was a .005µF(I used .0047µF with no problem) that is located from the power rail to ground near Q2. Mine did not stop squealing till I added that cap. It seems to bypass the PS and filter some squeal.

Shortening my wires and proper routing also helped. I struggled for weeks with it. You can't have the wires to the pots crossing over each other much. It meant I couldn't really lay out the box the way I wanted to but it works now so I don't care. It's a blast to play through.

I also used MPF102 at Q1.

HTH

RDV

[Stephen]

Where is a scheme for one???

Dr Boogey

[Gilles C]

Is that the one mentioned there?

http://www.diystompboxes.com/smfforum/index.php?topic=28854.0

Gilles

[Marcos - Munky]

The layout I used have that capacitor. About the wires, they are a little longer, but I will redo all the wiring after I box it.

Yeah, it's this schematic.