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previous: edwin hi RG,i've build 2 ... -- 10/15/1999 4:23 AM

Re: Transistors for Foxx Tone Machine?

10/15/1999 4:10 PM
R.G.	Re: Transistors for Foxx Tone Machine? Original FTM's were built with one of two transistor types, 2N3565 and 2N5133. Neither is widely available any more. I've tried a lot of transistors in this thing as well, and for the life of me (and some other guitarists who I asked to sit in) I can't tell any significant differences in tone with only the transistors. This is consistent with the circuitry - the input amp is a feedback pair, the others are a phase splitter and a simple common emitter amp. The last transistor in common emitter has the best chance to "imprint" the sound with any transistor individuality, as the feedback in the input amp and phase splitter should wash any transistor quirks out. 2N5088 and BC549 are close, and I would expect BC109C's to be as well. All are high gain (350+, 400+, and 300+ respectively) low noise devices, with high linearity. I did not try the 2N3565 as I couldn't get any either. I did try the 2N3904's and they were slightly softer than the 2N5088's, which correlated well enough with my expectations based on their lower (200+) gain. It's odd that your 2N3904's went the other way, not what I'd expect at all. I think Mark would do fine with the BC549, or other high gain, low noise NPN's. I think he'd have an even harder time finding 2N3565's or 2N5133's. The Experience Pedal is a partial copy of the FTM and uses NTE123's, 2N3904's, and other devices as well. My personal opinion and experience is that there are places where individual transistors matter - the FF and its brothers, cousins, and derivatives being notable - but that effects where most of the devices are used in high feedback pairs, emitter followers, or simple CE gain stages are not such places. Even in circuits where individual transistor characteristics matter, such as the FF and the Rangemaster, my personal advice is to get it working with something now, and tune it in with the perfect devices when they become available. As in all matters of tone, your own personal ears are all that matters, and you should go with whatever they tell you is right, no matter what I or anyone else says. That's one of the beauties of building your own - you can put in what sounds good to you.

10/15/1999 4:10 PM

R.G.

Re: Transistors for Foxx Tone Machine?

Original FTM's were built with one of two transistor types, 2N3565 and 2N5133. Neither is widely available any more.

I've tried a lot of transistors in this thing as well, and for the life of me (and some other guitarists who I asked to sit in) I can't tell any significant differences in tone with only the transistors. This is consistent with the circuitry - the input amp is a feedback pair, the others are a phase splitter and a simple common emitter amp. The last transistor in common emitter has the best chance to "imprint" the sound with any transistor individuality, as the feedback in the input amp and phase splitter should wash any transistor quirks out. 2N5088 and BC549 are close, and I would expect BC109C's to be as well. All are high gain (350+, 400+, and 300+ respectively) low noise devices, with high linearity.

I did not try the 2N3565 as I couldn't get any either. I did try the 2N3904's and they were slightly softer than the 2N5088's, which correlated well enough with my expectations based on their lower (200+) gain. It's odd that your 2N3904's went the other way, not what I'd expect at all.

I think Mark would do fine with the BC549, or other high gain, low noise NPN's. I think he'd have an even harder time finding 2N3565's or 2N5133's.

The Experience Pedal is a partial copy of the FTM and uses NTE123's, 2N3904's, and other devices as well.

My personal opinion and experience is that there are places where individual transistors matter - the FF and its brothers, cousins, and derivatives being notable - but that effects where most of the devices are used in high feedback pairs, emitter followers, or simple CE gain stages are not such places. Even in circuits where individual transistor characteristics matter, such as the FF and the Rangemaster, my personal advice is to get it working with something now, and tune it in with the *perfect* devices when they become available.

As in all matters of tone, your own personal ears are all that matters, and you should go with whatever they tell you is right, no matter what I or anyone else says. That's one of the beauties of building your own - you can put in what sounds good to you.

Replies:

edwin thanks for the explanation RG! i al... -- 10/18/1999 4:31 AM
MKB Just another opinion... I built an ... -- 10/18/1999 12:09 PM