Boy was I glad I did. The thing is nasty, sick, fierce and all the other things you want a fuzz to be. It is also a little more maleable than one would think, and VERY easy to build. The unit uses 2SC536F transistors. The F-suffix indicates 536's with hfe values in the 180's to 240's or so. The transistors on mine were around 250, but the values on one I built from scratch were 220 and the difference appears to have no impact.

The stock unit employs a passive mid-scoop filter between the fuzz-generating circuitry and output level control. While this injects the right amount of sinister tone (like a Superfuzz), it isn't always what you want. The scooping depends on passive loss through a 0.1uf cap. If you reduce the bleed through that cap to ground, you end up increasing the lower and upper mids and increasing the "body" of the sound. I inserted a 50k pot on mine (shown in the schematic) between the 0.1uf cap and ground. Alternatively, if the entire scoop circuit is bypassed and replaced with a fixed value resistor, you get the "full bandwidth" fuzz tone without any tone shapping.

The MP3 file provides comparisons between two FY-2 units. The first is an original, and the second is a home-build clone. What you hear is (in order):
- single note, original board, stock, minimum fuzz
- single note, original board, stock, maximum fuzz
- single note, original board, scoop bypassed with 33k resistor, minimum fuzz
- single note, original board, scoop bypassed with 33k resistor, maximum fuzz
- single note, clone, max fuzz, passive bleed through midscoop varied
- A-chord, clone, max fuzz, passive bleed increased over chord
- A-chord, clone, max fuzz, passive bleed decreased over chord

All samples recorded with neck+bridge pickups directly into a Roland UA-30 USB interface. No other devices were involved. Though the volume level on the fuzz was set the same all the way through, there are some pretty substantial volume changes so don't crank it up too loud until you've heard the whole sample.

Like most guitar compressors, the OS uses a feed-back control path so that the envelope/control-signal is derived from the changed/changing signal (one whose dynamics have been altered). This enhances the "squish" that compressors normally achieve.

Where the unit takes a slight left turn is in being able to select between feed-back OR feed-forward control. Feed-forward control is more often used in high-end limiters, and takes the control signal from a point *before* the dynamics were changed, this tends to result in the most compression being applied to the initial peaks.

The Tangerine Peeler incudes a control/capacity for adjusting the gain of the envelope follower and amount of dynamic attenuation applied (gain range of x2.45 to x26), as well as the release or recovery time of the envelope follower. It should be able to accommodate both hotter line-level input signals as well as guitar. Slower release times are more likely to have an effect on compression/feed-back.

As well, it includes a Tone control on the output stage. The output stage provides a fixed boost of x10. The design incorporates a second ground leg on the non-inverting output stage that provides for additional boost of higher end content. At maximum treble boost, there is a gain of x46 applied to signal content above 7.2khz. As treble boost is reduced, the amount of additional gain is decreased and the corner frequency where additional gain gets applied goes lower. At the halfway position (linear pot), there is a gain of about x14 applied to content above 2.2khz - just a modest nudge of the upper mids in comparison to the full-spectrum boost.

The pinouts shown are for any quad op-amp of the LM324/TL074 package pinout. I'm building mine with an LM837 quad lownoise op-amp. We'll see how well that works out. One of the advantages of this unit, though, is inclusion of an input buffer stage, which should add to the pleasing brightness of the original unit.

This circuit looks good on paper but as of October 10, 2005 is completely untested. Updates will be posted here as it gets built and refined.

To do this, the distorted signal is processed in parallel with the clean bass signal, filtered in a strategic way, and mixed back in with the clean. Rather than use variable gain to adjust fuzz amount, the gain is fixed, and the amount of harmonic emphasis to be added is varied. This gives the same quality of fuzz at all mix levels. The Harmonic Level control ranges from just a hint of grunt to almost more grunt than clean. If there isn't enough grunt for you, reduce the value of the 68k resistor before the Harmonic Level Control to 47k.

The Clean signal also includes a Tone control so that clean highs can be included when you mix the added Harmonics/fuzz well in the background. If the Harmonics are completely cut, the Tone control, together with the gain of 10 built into the unit, can allow it to function like a bass booster.

The schematic shows the various strategies used at different points in the circuit to achieve the sound.

The soundfile is a cheap fretless P-bass copy (though with only one open note being plucked who can tell its fretless?) going into the Gruntbox, into a Roland UA-30 usb interface and into the computer. The original recording is 44.1khz at 16-bit, downsampled to 22.05khz to reduce filesize. The same notes are played with the Harmonic Level up full, and progressively less harmonic content as the same pattern is played again. If you have a way to look at the waveform, note the asymmetry of the clipping emerging after the second repeat of the pattern.

Description of soundfile

Recorded from Turser Tele clone (passive pickups) into Forty-Niner into Roland UA30 audio-to-USB convertor. Originally recorded in 44.1khz 16-bit stereo. Reduced to 64kbd MP3.

1) Homebrew Crybaby into 49-er set for 3/4 drive; no freq boost
2) Same two chords played clean then with 49-er set for slight clip (drive around 8:00). If you watch the wavefile, note the compression.
3) Drive set to about halfway, treble rolled back. Same riff played twice, second time with boost engaged, but no pre-emphasis. This illustrates the slight overall boost provided by additional stage.
4) Drive set just under halfway. Guitar volume rolled back to clean up, thewn increased to demonstrate overdrive then boost engaged to push harder (still no preemphasis).
5) Everything dimed (no boost), and filter/treble control gradually rolled back. Seconds time the treble/filter control is gradually rolled forward.
6) Drive and 200hz boost dimed, treble rolled off

The unit has the standard LFO and regen possibilities, but it also has LFO shape, sum/difference outputs, and a whole truckload of modulation capabilities, including envelope-driven sweep. A *lot* of knobs and switches on this one.

As far as parts go, the only hard to get things would be the BBD chip (MN3009 256-stage BBD) and clock driver (MN3101) and a 2SA798 matched PNP pair. The MN3009 can be subbed with an MN3007 to some extent (though with a shift in delay time), and the other two are available, just hard to find from any of the typical industrial suppliers. Everything else either uses easily available parts or parts that are easily subbed for.

A PCB layout is included, flipped around for using PnP etching/resist method, however I cannot vouch for the scale of the layout. You may have to adjust the prinout size on your machine before printing it to your choice of transfer sheet. The traces have been digitally thickened a bit but I don't see any spots where there is big risk of traces bleeding into each other. That being said, you may want to touch up the resist pattern yourself before printing to transfer sheet.

The flaw in the circuit, if there can be said to be one, is the absence of companding for both level and noise control. On the other hand, there is pretty good lowpass filtering of the BBD (2-pole before and 5-poles after), and a input-level gain control so noise and distortion should not be too much of an issue.

This looks like a really interesting circuit.

The schematic comes from a collection of Japanese schematics that someone posted a while back. I cleaned it up a bit and flipped the PCB layout so that it is compatible with PnP transfer techniques. The PCB is probably not to scale so be careful in re-scaling it.

The diodes can be replaced with 1N914 without changing the circuit much. The 2SC1222 transistors are listed in my data book as the complementary unit for the 2SA640. I suspect that the 2N5088 would sub for the 2SC1222 just fine, meaning that a 2N5087 would sub for the 2SA640. It's your option to include the indicator built around TR4 or not.

Haven't built it, but it looks good.