Few days ago I came across an internet forum dealing with the old selmer buzztone (Pink Floyd’s Sid Barrett) and it triggered the wish to go listening to some old pink floyd and Marc Bolan’s T-Rex. Inevitably this triggered as well an old hybrid fuzz idea of mine. I breadboarded (again) that circuit.
Cloning isn’t my stuff at all, that’s boring and even though this isn’t very new either I like the idea of using modern concept (buffering) with those old germanium fuzz circuit. I have 2 AC127 which are low gain (30/35Hfe) but low leakage.
The circuit isn’t complicated. The first op amp gives somekind of buffering and additional gain to compensate very low pickup (telecaster, vintage P90 and so on…). Ideally the pre-amp control is a trimer otherwise it’ll be a “double” with the drive pot.After that the boosted signal goes into 2 cascaded germanium transistors. In this part all the value components matter somehow, they’ll depend on the sound you’re looking for.
Once passed through the distortion stage, the amplitude is reduced to a manageable signal (10V P-P isn’t very handy as it’ll sature right at the begining the input of the amp) with the value of the “cut” pot and volume pot (signal divided by two, basic voltage divider).Then, buffering for offering a low output impedance to the outside world (which will be very grateful for some much kindness)
And you have it. The final stage can be made more elaborated with incorporating the op amp into a more complex filter but I’d like to keep that 60’s/70’s aesthetic, that kind of textbook fuzz.
If you wish to have a lower impedance at the input and lose some high end (as a traditional fuzz face or big muff does) just reduce the value of R9 (which can be a trimer as well)
Originally, I wanted this circuit to be all transistors (yes, op amps are made of transistors, I should say “no ICs”) but I couldn’t find those bloody BS170 mosfet. I cleaned up my mess and of course I can’t remember where I put those (clean your room they say but it becomes even worse after that…)
This circuit is quite hot, it can be used as a booster (with massive results) or as an overdrive-fuzz. The plus side being that the “drive” control is useable on all its range which I tend to maximise in my design (otherwise why should it be here ?) I wanted to find that 60’s fuzz sound and I’m quite happy with the result.
needless to say that many things can be added to the design if you don’t mind the increase in pots. For isntance R17 can be changed for a pot to create a SAG effect (reducing current through with massive attack, giving that buzzing sound) . Thinking about it I might give it a try !
I’ll update the design once I get those BS170 back from their hiding and certainly make a PCB. The original plan was to use an old tonebender enclosure which is gathering dust in my junk box but it only has two pots and I’d like to have a kind of filtering happing (maybe I’ll try to hunt Boss double pots or something)
PS: No doubt many knows about Pink Floyd but Bolan seems to have less attraction and I don’t understand why. He produced wonderfull trippy music, so if you don’t know go listening to “electric Warrior” and “the slider” (amongst all the others albums) to get convinced !