FuzzBox 1967

[boratto]

[rocket88]

Since you were happy with the Fuzz Box 66, I took a shot at the Fuzz Box 67. Didn't test either one, just just drew up the layout. Got some time on my hands today since I'm home sick from work. Let me know how they go.

[boratto]

Both deserves the layout section, from the crypt to the light!

[rocket88]

Let me know both fuzz boxes go, man. If they work I'll move them over.

[tjdracz]

Only shame that these MAT transistors are unobtanium now!

[rocket88]

Aww man. What can be substituted for them? I think it would be awesome to make a pedal this old usable now. I hope that it sounds good too.

[tjdracz]

2N499 and 2N500 seem to be close substitutes but with higher voltage ratings. They are also quite rare but analogue in turn to Russian GT305A and GT313A which are available from usual sellers of Soviet germaniums.
I did some reading on that circuit and transistors and it seems that basically as long as you keep Q1 and Q2 high and Q3 low, all germaniums (opposite of Tone Bender type and similar to Fuzzrite type) you should be good. Not sure about gains of original MAT types so best idea is to just breadboard and socket them until it sounds good. Additionally, trimmers at Q2 and Q3 collectors might be useful to adjust the bias to taste.

[tjdracz]

Additionally, for anyone interested, here's the link to the issue of PE where the circuit was published, includes nice explanation and couple of quirks like removing the diode producing the tremolo effect (is it due to the fact that they are there for temperature stability (?) and without them those early transistors would just fluctuate in gain, thus bringing the tremolo effect? I'm far from being an engineer and I'm interested how it works and that was just my educated guess)

https://archive.org/details/PracticalElectronics1967November

[IvIark]

Just use any germanium PNP transistor in there and I'm sure it will work fine, try silicon too.  The MAT transistors were almost certainly only used because they were "in" at the time, but let's face it, if they were that good they'd be sold all over the place now instead of 50 years forgotten.

[IvIark]

tjdracz wrote

Additionally, for anyone interested, here's the link to the issue of PE where the circuit was published

Thanks, I really love these old electronics mags.  I need to spend a few days downloading them all

[rocket88]

Aw man that just seems crazy. I went searching to find the MAT transistors or at least some info on them and I really didn't find much. But, it seems there is a group of people across the pond that rebuild old radios that have horded a whole bunch of them. Hopefully the layout works, and someone builds it. I'm really curious to know how this thing sounds, you could put the diode on a switch so you can have 2 effects in 1.

[tjdracz]

They are just germanium transistors that were on vogue back then, with quite high frequency capabilities, hence the usage in radios.
MAT120 is 25-75 gain and MAT101 is 75-200. Take a low leakage fuzz face pair and at another transistor around 130-150 and it should do