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Does the Bohemia have smd pads for the Jfets like the Covert od? Mmbf4393 supplier?

Tha’ToneSeaQr

New member
I'm actually planning to build both of these, but before I order the Bohemia PCB I want to be sure about mounting the Jfets. Like most of us nowadays the only reliable spec, reasonably priced jfets are smd type sot-23; mmbf5457, mmbfJ201 etc.. So I need to know if I need to buy conversion boards for the Bohemia. Thanks!!

Ps; mpf4393's aren't available anywhere I know of, and likewise with their smd type counterpart mmbf4393. I was planning to just use my stash of mmbf5457's.. Just out of curiosity, and for the sake of experimentation; is anyone aware of a reliable supplier of 4393's? Can be th-hole or smd package I don't care..
 

Chuck D. Bones

Well-known member
Dude, read the Build Docs. If there are alternate footprints, it would say so there. Spoiler alert: there aren't SMD pads on the Bohemia.

AFAIK, the supply of NOS MPF4393s has dried up. That circuit will tolerate other JFETs. Look for ones with Vp around 2V.

FYI, PN2222A & 2N2222A can be noisy. MPSA18 or 2N5088, 2N5089, BC549C, BC550C, etc. are all better alternatives IMHO.
 

Tha’ToneSeaQr

New member
Dude, read the Build Docs. If there are alternate footprints, it would say so there. Spoiler alert: there aren't SMD pads on the Bohemia.

AFAIK, the supply of NOS MPF4393s has dried up. That circuit will tolerate other JFETs. Look for ones with Vp around 2V.

FYI, PN2222A & 2N2222A can be noisy. MPSA18 or 2N5088, 2N5089, BC549C, BC550C, etc. are all better alternatives IMHO.
Appreciate your input!
I guess I knew the bohemia didn’t have smd pads but I thought it might because the DLS clone board had em, and I’ve found (not on here) that there are often lots updates & changes to diy pcb’s that aren’t documented in the build files. So again thanks.

*Ps; You recommend non jfet transistors, I’m just curious about your observations sonically.. IOW if you were able to compare the sound/feel of this or any amp in a box circuit with jfets vs say an mpsa18 like you mentioned.. Boy I’ll tell you I’d sure be happy if a 7cent general purpose silicon transistor actually sounds better than an expensive, fussy hard to find, jfet.. They vary so widely between type & even individually, yet they’re not easy to measure.. needs to be biased, sorted for the right specs, etc etc!
 
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