Morley Pik effects

[RickL]

Some time ago I built a Pik-A-Wah using this schematic: http://www.morleypedals.com/sawes.pdf

It uses a metal pick to trigger a filter giving an envelope wah type of sound. The 1M pot controls how fast the filter sweeps. I have wanted for some time to build just the envelope part of the schematic (the lower half of the schematic) and see and see how well it could control other effects. I finally did it today and was quite impressed with the results.

I tried it using a home made LED/LDR as well as several commercial combos (VTL 1C1 , CLM 8000, etc) and all worked to a greater or lesser extent.

I tested it by clipping the leads of the LDR across the pot terminals of a number of effect controls. For the envelope control to work the pot had to be used as a variable resistor and had to be set above its minimum resistance, usually wide open worked best.

I tried it on a number of wahs and filters and all of them sounded good. It also sounded great across the gain pot of a Distortion + type circuit. Picking faded the distortion in like a Slow Gear. With the clipping diodes lifted in the D+ circuit I got a very good clean Slow Gear effect that triggered perfectly every time. On a SHO type effect the picking produced banjo type short envelopes. I imagine the same thing would happen if used on the gain control of a Fuzz Face.

It was less effective controlling the rate of a couple of tremolos and a phaser. The effect was noticeable (speeding up over time) but without tweeking there is no control over the maximum rate. I expect it could be done with a pot in series with the LDR but I didn't try it. It did sound kind of cool on one of the trems where fast picking leading into a sustained note gave the aural impression of adding tremolo only to the sustained notes.

I also tried it on the volume control of a couple of effects, clipping the LDR across the centre terminal and either the input to the pot or ground. I could get some effect, either volume increases or decreased but because of the nature of the control I couldn't go from silence to a preset volume either direction. It was kind of a less effective version of the D+ or SHO effect. The same thing happened when I tried it on the depth control of a tremolo. A bit of fading in of the effect but not enough to be usable.

At some point I'd like to try it in place of the LFO on a phaser that uses LDRs (like the Craig Anderton version or the Commonsound phaser) to see if I can get enveloped type sounds.

In short, I'm happy with the results and it's a simple enough circuit that it could be added to any number of effects, even commercial ones.

[petemoore]

Cool, if I understand it correctly...
  The pick is a conductor [wire goes from pick to...how far/long of a wire can this be?] when it touches the strings. The pulse then triggers the envelope.
  Pretty snazzy and simple !
  [One more wire]..a quick and dirty.. to get a 'separate' trigger set up.

[Mark Hammer]

Hi from the other side of the country, Rick!   Hope all is well.

Using the envelope generator section of the Pik-A-Wah is a great idea.  I gather that the envelope produced is fixed in time constants, and does not correspond to picking force, but simply uses the pick as a means to ground the input and force a pulse that gets stretched into a rising and falling envelope.  Faster picking essentially interrupts and resets the envelope generator?

[RickL]

Yes Mark, you've got it exactly right. A pot sets the decay (or rise, depending on how you look at it) time from almost instant to around a second. It has the advantage of triggering perfectly each time you pick, the disadvantage of having to use a metal pick with a wire attached.

The wire can be pretty much any length you want and it only has to be a single strand. The pick triggers the circuit by grounding through the guitar. It would also work using a foot switch to trigger the envelope but of course it wouldn't be syncronized to your picking.

One problem is that the envelope only goes in one direction. Grounding the pick turns the LED off and it brightens to an amount set by a trimmer. I downloaded the schematic for the Pic-Attack which has a slightly different envelope generator. I'm going to build it and hope that it works the opposite direction. If so, used with a filter it would give backward wah sounds, with a speed control the effect would slow down over time, etc.