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Guitar pad file:   Guitar_pad.mp3 000092   5/19/2010 12:12 AM
Ethereal guitar sound made by plugging into a Craig Anderton Bi-Filter Follower, then into a PAiA Gator, then a Boss DM-3 clone modded with a hi-cut filter in the feedback path. The phasing effect is added digitally with Audacity, but everything up to that point is analog.

A trip back to the park - adventures in re-echo file:   Re-echo.wma 000091   1/30/2009 2:26 AM
The Line 6 Echo Park comes with two inputs and outputs. While not true stereo, the unit allows for some interesting cross-recirculation and reprocessing possibilities.

The soundclip illustrates two of the possibilities. It starts out with a short riff using the "reverse" program in the normal way. I have it panned 100% wet so you only hear the reverse. From there it switches to a re-echo whereby I plug into A, run A output back to B input, and send B output to the amp. You can hear a lovely shifting overlapping sound. Note as well that when you reverse what has already been reversed, you get it forwards again...sort of. Really interesting texture.

The second half of the sample illustrates the same once, then twice, processing of the "sweep" program. This is a program in the Echo Park that imposes a kind of wah sweep on each iteration. You'll hear it normally (again, 100% wet to emphasize the sweep), and then reprocessed. Note the lovely rhythmic emphasis feel to it. Also note that I have simply hit one note to produce all that.

Apologies for the buzzing. That's what you get when you record with single coils in front of a CRT monitor in a room with fluorescent lights. The fuzz is a Jack Orman Mos-Face; a variant of a Fuzz Face but with a mosfet transistor.

Envelope control of a Boss RPH-10 files:   PH-2_2.png | RPH-10-a.jpg | RPH-10-all.png | RPH-10_with_env.wma 000090   1/22/2009 1:51 AM
I recently picked up an old Boss RPH-10 phaser. This is a terrific little unit that should be thought of as a more muscular version of the PH-2 phaser pedal. Both are 12-stage phasers with 8 swept stages and 4 fixed stages, and both use Boss's proprietary IR3109 quad OTA chips as well as companding to make the IR3109s behave. The PH-2 appears to have a 6-stage and 12-stage mode, where the RPH-10 has a 3rd mode that seems to have 10 stages but stagger the sweep of the two IR3109 chips in some manner.

Where the PH-2 has the usual Rate, Depth and Resonance/Feedback controls, the RPH-10 adds a Manual offset control, not unlike what is in the BF-2 flanger. Just like the BF-2, the Manual and Depth complement each other.

Several other features stand out in the RPH-10. First, it has dual feedback paths, which the PH-2 does not have. Second, it has a "polarity" switch which inverts the control voltage. Third, it has a patch point for control voltage which lets you feed the LFO out, or feed another control voltage in.

With that option available, I went ahead and added an envelope follower to provide envelope control of phasing. It was a simple half-wave rectifier, based on the venerable Doctor Q,providing a gain of around 168 at max gain. I used a 10uf cap to smooth the envelope in parallel with a 47k resistor to keep the decay time modest. The resulting envelope voltage is fe through a 10k resistor to the junction of R82 and R58 in the RPH-10.

Because the internal shell is already pre-machined to accommodate more controls than come with the stock RPH-10, I was able to use those holes to add a sensitivity control and a toggle to enable/disable the envelope input. All that remained was to pop a couple of suitable holes in the plastic panel, add some rub-on legending, and wire up the little daughter board.

It all worked like a charm and I recorded some rather amateurish samples to show off what it does. They are strung end to end, and illustrate two of the modes in each polarity setting, ending with a combination of LFO and some envelope modulation over top to show off what you can do with two control sources. It provides a nice semi-periodicity that "humanizes" the sweep.

I have to say that envelope control of phasing is a very nice thing to have, and the RPH-10 makes it easy. A more valuable unit now, IMHO.

Some Shin-Ei Hockey files:   FY-2.mp3 | modded_fy-2.gif 000089   6/23/2006 1:46 PM
I acquired a Shin-Ei FY-2 fuzz in 1992 or so. I had bought it for $20 from a second hand store, largely because it had a decent case and stompswitch and buying either of those where I was living at the time would have cost me at least $30. Having a naively lesser opinion of 60's fuzzes at the time, I ripped the circuit board out and built another circuit into the box. The original board sat around for a decade or more until someone finally posted information that let me reconnect the pots to it and fire it up.

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.

The Tangerine Peeler file:   Tangerine_Peeler.gif 000088   10/12/2005 2:36 AM
This is a first attempt (October 2005) at a slightly more complex derivative of the classic Dan Armstrong Orange Squeezer OS compressor. The OS is much loved as a pretty transparent guitar compressor. The transparency is partly achieved by means of a low distortion solid-state "virtual" attenuator comprised of an 82k resistor and a 2N5457 FET. The use of an RC network between drain and gate helps to reduce distortion of the cell. Also helping to produce the transparency is an envelope follower with relatively fast attack and decay. Use of a FET as the control element further aids the speed of the unit.

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.

Gruntbox - a fuzz just for bass file:   Gruntbox.zip 000087   8/2/2005 1:42 AM
This is a distortion unit designed expressly for bass. The goal is to give the bass a solid sound but make it sound more emphatic, like a grunt. Don't even think of building one for guitar. It won't sound good at all. On bass, that's another matter.

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.

Forty-Niner soundsamples, schem and pix file:   FortyNiner-1.zip 000085   7/16/2005 1:09 AM
The Forty-niner is a 4049 hex invertor based overdrive capable of a wide range of sound, though a particular character of distortion remains in all settings. It includes a boost function that adds a bit of gain and can add some serious boost at several specific frequencies.

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

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