ampage Tube Amps / Music Electronics	For current discussions, please visit Music Electronics Forum.

ampage archive

Vintage threads from the first ten years

Transistors in fuzz box

:

6/22/2000 2:05 PM
SteveG	Transistors in fuzz box I have an old fuzz pedal with two metal can transistors marked: SPT 363E and SPT 337 ( the 'P' in SPT could be an 'F' or 'R'). Does anyone know what these are? (Germanium or Silicon, equivalents, etc) Thanks a lot, SteveG

6/22/2000 3:01 PM
Liam	Put a diode tester across the base/emitter junction. If it shows about 0.6-0.7 volts they're silicon, if it shows 0.15 - 0.4 volts they're germanium. Liam

6/23/2000 5:10 PM
Ian Anderson	Steve! I can find no listing for SPT or SRT suffix transistors. I can only find entries for SFT337 which is a PNP Ge device with a typical Hfe of 100. equivalents listed are AC125 and 2N406 ...Ian

6/28/2000 12:56 AM
SteveG	Cheers Ian SFT must be it - the letters aren't easy to read. BTW did I read in another thread that you're building a Rangemaster? Did it work out OK? I made one using a Mullard OC44. It sounds pretty good. Steve

6/28/2000 11:55 AM

I still haven't gotten round to doing that rangemaster because all of the transistors I've got (or have gotten since) have either been too high gain (probably leaky) or the ones that have been in the right gain range have not biased properly according to R.G's notes on how to build one to get the original sound.

I've already built it one before by just subbing different transistors (ACXXX's), but I don't think it was working in the way it should - sounded terrible. Not even a nice treble boost, just very quiet and raspy.

I'd love to get one working to go with my newly aquired bluesbreaker combo.

... Ian

6/28/2000 1:32 PM

I've built a couple with 2SB172's, and they work very nicely. I think the secret to building one is to have a breadboard, and a broad assortment of resistors, since they aren't all biased the same with the same nominal resistor values. The last one I made used 470k and 68k, as per the original, but used a 3.3k instead of 3.6k to get the collector voltage to around -6.87v. I had to sub a few values to find that out. A trim pot CAN work for this, but sometimes it's hard to tweak one in small increments.

The results are pleasing, though. Seems like an oxymoron, but the sound is at once mushy and bright. I stuck one in a little Muff Fuzz case I had sitting around (the Muzz Fuzz is long gone but the 2N5133's live on in something else).

6/28/2000 6:11 PM
Ian Anderson	What version Muff Fuzz was that, was it a homebrew? I've only ever seen the op-amp schematic. I made it a while back and thought it sounded quite cool in a Neil Young 'rockin in the free world' kind of way. ... Ian

Page 1 of 2