Square Wave

The Square Wave is a very transistor-y sounding fuzz before the hard clipping section and more exploding and gated sounding after it.

The original two controls were balance and shape. Balance is output volume. Shape forces the output through a small capacitor. It reminds of a Muff or Fuzzrite tone control. Shape's low end makes me think that this might be a great platform for a bass fuzz.

One common mod to this circuit is a clipping diode lift switch. The non-clipped fuzz is sort of plain sounding but much louder than the clipped signal. With the diodes engaged the fuzz volume is lower than unity volume at the treble end of the tone spectrum. Perhaps one could use LEDs in the clipping section to strangle the output volume less. The other common mod is a gain (fuzz) control.

The end result is a fuzz that covers a lot of sonic territory. With lower fuzz and no clipping it is a fairly usable distortion. With the fuzz cranked, diodes engaged and especially at the treble end of the spectrum at is pretty gnarly and nasty. Lower the fuzz and you are in Satisfaction territory.

Harmonic Percolator

The Harmonic Percolator challenge. What should it sound like? How much should it clean up? Does that high pitch Velcro noise at the top of the note when backed off make the Jerkulator unusable? Should the input volume be left off? Is a clone made from more commonly available parts a clone at all? What means good when a pedal at its best sounds "bad"?

The lore of the Percolator is all over the place out on the web. Clones are commonly available. Devi Ever came up with some values that would work well with commonly available parts. Her version (the Jerkulator) uses two Silicon transistors and eliminates the hard clipping diodes. This is the version with the high fizz when input volume is backed off. Full up it sounds explosive and delightfully broken and over the top. With certain bridge humbuckers it delivers a delightful kerrang with the strumming of an E major cowboy chord.

My recent attempt to breadboard the circuit (as it may be as there are a variety of schematics on the web) with a NPN Silicon (2N4401) and a PNP Germanium (AC128) transistor resulted in a backed off sound without the fizz, bright and raspy. Full on it has that exploding thing but raspy, not as bright and biting. It has more of a lo-fi edge. I'm not really getting that E chord tastiness and single notes sound weak and uninspiring. The resistance between the collectors and voltage and between the bases and collectors of the transistors can be tweaked for gain and texture.

I am going to end up using pots to dial in those resistor values and going with what sounds best bad or worst good and be happy with it. Hopefully I can hang on to that kerrang with enough gain for tasty single notes. Hopefully I can back off the input and get a sparkly clean.

Here is a phone video of a Firebird through a "stock" ish Percolator with a variety of guitar settings through a modded Valve Junior.

Here is the Jerkulator with and without Germanium clipping diodes engaged.

Here is me dialing in what I would hope to be the ideal tone with these particular transistors. 1M pots instead of the resistors between the collectors and bases. 100k pots from collectors to v+ and ground.

I basically ended up with the same tone but with more squish. Somewhere in there there is a bright tone with less squish but still very transistorish. What to choose!

Here is the schematic for the squishier sound:

If you flip the values of the resistors form base to collector it is much tighter and brighter. Also, I discovered that with the tone rolled back, things get very interesting. Super saturated and bright.

Update: I think I nailed it! A 220k resistor replacing the 750k and a 500k pot in series between the base and collector of the silicon transistor. This allows me to adjust from raucous and open sounding to squishy and exploding!

Boost

This is the story of a 1 knob, 1 switch treble/bass booster with mid cut.

The challenge, instant EQ change for a boost (or cut) to move the guitar into another sonic room. I started with a known (and often used) boost schematic, the LPB-1. This is a very easy (easy's good) 1 transistor transparent boost. Minimal parts, very tweakable. The EHX Mole/Hog's Foot bass boost and Screaming Bird/Tree treble boost are variants of this circuit with larger or smaller caps to achieve the desired frequency response.

In my prototype I used both the Mole and Screaming Bird input capacitors and made them switchable for an either or arrangement. The Mole has additional .1uf capacitors from the collector to v+ and emitter to ground. I allowed control of these with a stacked B100k potentiometer. I split the difference on the output cap and went with .1uf. The output cap does not have as much impact on the sound and works fine in both bass and treble modes.

I added Nocentelli's mid scoop control to the output. It does knock down the output volume quite a bit. I added another gain stage to compensate when the scoop is enabled.

Swiss Cheese Prototype

After experimenting with and listening to the prototype and receiving feedback from friends I decided to limit the amount of control-ability to one knob and one switch. The knob would sweep between bass and treble boost. The switch would enable the mid scoop. There would be internal trimmers for output volume and amount of scoop.

Version 1.1

All Boxed Up

This thing sounds remarkably good with bass for a big helping of extra boom. On the treble side at adds shimmer to clean tones and has a Rangemaster effect to already dirty sounds. The mid scoop is troubling before a dirty signal. The overall effect is added messiness and more pronounced low end, not in a pretty way. Clean however, with the input cap balance skewed toward the treble end and the mid scoop engaged, a Fender guitar has delicious shimmer and bite at some very tasty, ear pleasing frequencies.

There is still work to do but it is going the right direction.

Happy Anniversary

This is the green Soviet Muff with custom paint I made for my wife for our fourteenth anniversary. It's an awesome circuit for bass. It's seems to let a lot of the bass signal through under the fuzz. Meaty!

Happy anniversary honey!

Coily Cord Simulator

This is not a new or original idea. But, I am suddenly fired up about it since accidentally receiving a Seymour Duncan Pickup Booster. The Resonance switch on the Booster engages a couple of different low value capacitors to ground. This has the effect of rolling off a little or a little more of the high end, much in the way that the capacitance of coily cords did back in the 60s.

I ran across some cheap, small steel electrical enclosures perfect for a little "pedal" version of this mod. The tip of each jack is connected through the poles of 2 SPST switches. These switches connect a 1nf and 3nf capacitor to ground.

Fancy Elaborate Schematic

This gives me the choice of no capacitance, 1nf for a short cord, 3.3nf for a long one and 4.3nf in parallel when both switches are engaged for a really long cable simulation. This really only works in the historically accurate way when placed between guitar output and the first thing in your chain.

It's Cute!

The flanges on this box inspire me to want to attach it to another pedal, an amp or even a beater guitar.

Fuzzrite

The Germanium Fuzzrite is the fuzz that comes to mind when I envision Italian soundtracks or funky soul solos. It is also the In-A-Gadda-Da-Vida fuzz. It's brash and tight at one end of its tonal spectrum. At the other end it is almost not fuzzy at all but bassy and muddy.

My Germanium Fuzzrite Build

The top left control blends between output from the first transistor (dark and less distorted) and the output section through a tiny capacitor (bright buzzsaw). Somewhere in between is great for single note lines. It's perfect for nailing those "I'm pretending to be a brass instrument" tones of the sixties.

I socketed the transistors and capacitors for experimentation and left out the external power input and LED for a true vintage experience. 

The second control is output volume. There is no gain control. It does clean up when the guitar volume is rolled back. However, the resulting tones are very bright and low fi. Here is a down and dirty demo with a LP Jr Special through a modded Valve Junior.

To sum up, this pedal lacks versatility but it nails some great, bright 60s tones.  Here it is in action at Club Congress in Tucson standing in for a sax solo in a Nina Simone cover (1:32).