The first Fuzzface units utilized germanium pnp transistors since they were the semiconductors most available and reliable at that time. The schematic below shows the circuit of the classic unit.
You’ll observe that the positive battery connection is grounded and also the circuit utilizes a negative supply current. This is actually the typical method in which simple pnp transistor circuits are utilized. Additionally, it helps make the circuit incompatible using the usual pedalboard power which has a negative ground along with a positive supply current.
There’s an easy solution though. turn the circuit "upside-lower" and employ an optimistic power! The floor connection from the pcb will end up the V+ and also the previous ground pad attached to the positive current. This really is shown within the schematic below.
Should you consider the drawing you’ll rapidly uncover there’s very little difference backward and forward circuits. Think of the ground of battery at the base drawing attached to the ground reason for top of the finish from the 33k resistor and you will see that it’s the just like within the original. The Fuzzface circuit is effectively "isolated" between your input and output capacitors and can’t tell if it’s being run from the negative or positive ground power. certain points from the circuit are pretty much positive than the others which relative current is exactly what determines the bias and never the polarity from the power.
So how exactly does it seem? Just like before – the transistors cannot differentiate!
You’ll observe that I’ve altered the polarity from the input capacitor. I believe that it’s more correctly oriented by doing this since the bottom of the input transistor Q1 is going to be about .7v below its emitter in current, that is 8.3v as proven. You can’t get a lot more positive than that within this circuit and also the capacitor is much more correctly placed using the plus side attached to the transistor base. Either orientation using the capacitor and also the circuit will still work.
I’ve altered laptop computer board labels to mirror the brand new designations from the power and ground pads and provided it for download. One factor to become careful about may be the connection from the 1k Fuzz pot the finish not attached to the pc board points X and Y should be linked to +9v and never to ground as formerly.
This trick works together with both plastic and germanium transistors and might be adapted for other kinds which use pnp transistors (such as the Rangemaster) though it’s possible the electricity configuration of some circuits might not be suitable for it. Do this wiring setup and eliminate the requirement for another negative current supply in your pedalboard.
How you can use the technique (fundamental steps):
- Find out if all of the grounds are linked to a typical point around the pcb. If that’s the case, you are able to switch the V- and ground connections to ground and V+ correspondingly.
- If there’s any pot which has a electricity road to ground, the grounded finish should gone to live in the V+ supply. A good example of this is actually the Fuzz control within the fuzzface examples above. Observe that the output Volume pot is ac coupled via a capacitor which is not altered.
- Make all connections short and direct.
- If for whatever reason you do not such as the seem while using the positive supply current, it’s easily altered back.
Update 12 Marly 2002
I received an e-mail asking if the approach to powering might cause oscillation within the circuit. There’s always the potential of oscillation in most high gain circuits if good construction practices aren’t adopted however, there are lots of examples in circuit good reputation for PNP transistors operated off an optimistic supply. More often than not if you notice an NPN driving a PNP inside a typical transistor circuit the PNP is working in the positive supply. The Roger Mayer Axis Fuzz is certainly one commercial illustration of this method the Harmonic Percolator is yet another.
If for whatever reason oscillation does occur, an excellent low esr capacitor in the positive supply to ground will solve the issue everytime because it effectively places the ability rails in the same ac potential. Place the capacitor using the pc board if at all possible. Also keep your good and bad power wires as little as practical. I have used this process with two different fuzzface derivatives for a long time without any problems and one of these includes a quite lengthy positive power wire.
The circuit may be easily converted to positive ground when you get oscillations that aren’t cured through the power filter.
You like the typical Germanium sound from the 1970’s? (2W Audio amp. with 2 Germ. end transistors))
- colinmel66: Could I substitute silicon transistors for the germanium output pair? (while I'm waiting for my AC187 & AC188 to arrive 🙂
- scott2000: Great channel! Wow what a treasure of information. Thank You! I wanted to ask, and sorry if it has been answered already, but when coating wood for a project, does it have to be pvc glue or can it be something else like polyurethane clear? And, when you say brass nails, can they be brass or copper "coated" zinc? That's all I have seen locally. Thanks so much! Already grabbed a few books from you! Wish I could read the others!
- Riskteven: I LOVE it when you upload videos about projects where you can actually hear the signal, like LF circuits with amplifiers and oscillators that generate max 20Khz. Thumbs up for this!
- PASSTRAN eci_twi: excelente amigo
- Are Jayem: Angry discussions can happen in the expensive audio amplifier world, where tube amp people talk to solid state amp people how tube amps sound "so warm, natural" and so on… For me, I'd like to see electronic and frequency-spectrum analysis to show "pure, warm, natural" versus not having such characteristics. With comparing analysis using the numbers, if there's little difference, then it becomes what people think or decide, not any physical reality.
- kazibadema kalim: thanks . nice video!
- Francois Dastardly: Excellent ! Thanks.
- Shandybrother: I like the way you drew your schematic, reminds me of the cards for the philips
electronic engineer kit I had as a lad!
- DrCassette: I once tried building an amplifier based around the AC187/AC188 transistors but it never worked. I have to see if maybe I still have some of these transistors. When I bought them, they were tied together into pairs with wire through the screw hole, so they had already been matched. But back then I didn't know what that meant so I just cut the wire. Oh well…