Any Pedal Schem's for Acoustic Guitar ?

[Arn C.]

I have used some of the pedals I've built from here with my acoustic electric, but some don't work so good with it.   Are there any effects schematics floating around for just acoustic guitar ?

Thanks!
Arn C.

[Mike Burgundy]

Most stuff for acoustic is a lot more full-range than for electric. You'd at least have to voice stuff differently.
What works for acoustics are high-inputZ buffers (needed for piezo's), EQ's (preferably parametric, if you want I have a pcb around somewhere), and stuff like choruses, delays and reverbs. Compressors are great, too, especially the ones that allow attack adjustment.
More extreme effects like distortion, ringmods, wahwahs usually don't sit too well, unless you intend to destroy the acoustic character.
hih

[Arn C.]

Thanks Mike!  

Parametric EQ pcb?  Yeah man!  I would sure appreciate that if it is not a problem.

Thanks!
Arn C.

arn.conklin@ametek.com

[Mike Burgundy]

I'll do some digging. Drop me a PM if I don't post back in a day or two - it's on a different system and I'm prone to forget at this time

[Mark Hammer]

The "Harmonic Sweetener" from Jules Rykebusch is a nice addition to an acoustic guitar.  Cheap, simple, and straightforward.  Brightens things up nicely.  I used the basic principle of it for the "Woody".

[Arn C.]

Thanks Mark!!!!

Peace!
Arn C.

[Arn C.]

This one Mark?

http://www.montagar.com/~patj/harmswtn.gif

Is the schematic correct?  Just curious....

Thanks!
Arn C.

[Mark Hammer]

Yup, that's it.  The schematic is correct.

I built one shortly after the article originally appeared, and powered it with a couple of 9-volts.  I also stuck in a variable gain pot in the clipping stage, and a dual-ganged pot for retuning one of the filter stages, as shown in RG's redraw of what I sent him all those years ago.

The unit uses a fixed 4-pole highpass, but I found you could get a nice variation in timbre to suit different signal sources if you made one of the 2-pole stages retunable.  It's not a day and night difference, but its certainly more than a mere nuance.

Since the LEDs have a high threshold, and since the stock unit assumed a particular input level, I put in the variable gain, which also helped out a lot.

The Woody modification of this involved the following:

1) The 4-pole/2-stage highpass was replaced with a 3-pole/single stage highpass.

2) The LEDs were replaced with an asymmetrical (2+1) Si diode complement in the feedback loop, with somewhat reduced gain because of the lower clipping threshold.

3) The inverting stage used in the HS was replaced with a single all-pass stage to monkey around with the harmonics/fundamental phase relationship.  I recalled reading somewhere long ago when Aphex stuff first started being used that it employed some sort of "phase-shifting" post-clip to add a little more animation, so I figured I'd try it out - small-time - and was pleased with the outcome.

Since your intent is to use it with acoustic guitar, rather than park it as a nondedicated unit in a studio rack, I'd suggest rolling off the highs around 10-12khz in the first op-amp so that you don't get too much audio crap being boosted and mixed in.  Remember, that clipping stage boosts ALL that high end coming into the filter section, including whatever hiss precedes the input of the unit.  You'd like to be able to mix the additional *musical* harmonic content back in without having to fight to hear it amidst all the boosted thermal noise that might come through the same path.  Good idea to use a decent quality op-amp at the input stage and low noise resistors there too.