Resonance as an effect

[Noplasticrobots]

I breadboarded a Colorsound wah yesterday and have a resonance pot on the board instead of the 33k to ground. I'm having fun with the resonance, it gives some pretty freaky sounds in certain ranges, especially near the oscillation point.

If I were to commit this circuit to solder, I would use it as a static wah (no wah enclosure) and it got me wondering if I could just build a "resonance box"?  Resonance isn't something I come across too often in pedals so I don't know much about how to implement it. What kind of circuitry is required to get resonance? If it's just a variation on an RC filter, can it be dropped into almost any circuit?

[John Lyons]

I've done a lot of fooling around with the Colorsound circuit and have the 33k to ground on a trimer as well as a dedicated pot on one build. There are some nice crazy sounds available for sure. You can tune it to the key of the song similar to a ring modulator etc.
The wah circuit is in the guitar range so really it most usable in it's unchanged schematic state. Since there are only a few parts I would put it on a breadboard and change out parts until I founs someting I liked.
Things to fool with:
The 33K to ground = resonance control if changed to a pot
Emitter to ground changes the gain of the wah. Smooths out the sweep with a foot controlled rocker. Sort of an intensity control.
Try .1 in and out caps for a fatter sound, .01 in and out for a thinner but tighter sound.
Change out the .002 and .0068 caps to fool with the range or frequency of the filter.
There is another inductorless wah on the GEO effects site with different values and a couple transistors, I have not tried it yet.

There are a couple soundclips on my site www.basicaudio.mrdwab.com look under the pedals page and near the bottom.

John

[Noplasticrobots]

Thanks for the tips John. I actually listened to your samples before I breadboarded this circuit! I'm off to try that emitter to ground trick right now!

[John Lyons]

Noplastic
The emmitter to ground is mainly a foot operated wah thing because it it fairly subtle and only effects the intensity...although that is important as well with a manual wah.

Also, the .015 cap that connects to the 33k to ground (or trimmer resonance control) makes a difference as well. I ended up liking the original value for a foot operated classic type wah but see what you think.

A cool thing to do is to get a couple rotary switches or just toggles and wire up the diferent caps you like as options you can switch between.
An input cap switch etc. or any other combos you want two switch between.

John

[Paul Perry (Frostwave)]

Resonance isn't something I come across too often in pedals so I don't know much about how to implement it. What kind of circuitry is required to get resonance? If it's just a variation on an RC filter, can it be dropped into almost any circuit?

If you have any lump of circuit with a gain of more than 1, then there is potential to feed back some of the output to the input, and get it to 'resonate'. What frequency it will do this at, depends on the frequency response of the circuit you started with.
If the gain is greater than 1, but out of phase, you need to have a phase switching stage in the feedback path.
A major problem, is that when the gain gets greater than 1, the resonance builds up & you get total overload... so you might want diode limiters for example.

[alderbody]

here's my resonance pedal:



It's a Vox style wah circuit though, but with a Ge transistor for Q1.

I really like it and i use it almost every time.

[John Lyons]

Do you have a schematic for that circuit Alderbody? Just curious about the gain control. Is it just a volume control at the end of the whole circuit or an actual gain control?

Thanks

John

[DDD]

As far as I know Frank Zappa used some sharp resonance schematic just on-board his guitar to obtain unusual effects and feedback.

[Gilles C]

Could be of some interest.

http://www.musicianshotline.com/issue/2006/0806/46.pdf

Gilles

[Marcos - Munky]

This seems to be an quick and dirty version of the Technology of Wahs at RG's site. But it's a cool article and also have an RG's photo in it .

[Gilles C]

This seems to be an quick and dirty version of the Technology of Wahs at RG's site. But it's a cool article and also have an RG's photo in it .

Well, just for that, I though it was a cool article... I never saw a photo of R.G. before.

Gilles

[Paul Marossy]

As far as I know Frank Zappa used some sharp resonance schematic just on-board his guitar to obtain unusual effects and feedback.

Yep, a pair of identical parametric filter circuits was installed in his guitars. Check out this thread for more on that: http://www.diystompboxes.com/smfforum/index.php?topic=36227.msg256447#msg256447

[John Lyons]

For a deluxe version of a filter with resonance check out the Craig Anderton "Super Tone Control" I built one and really like it. I have a few clips here: www.basicaudio.mrdwab.com under the pedals page and under "State Variable Filter" . Lots more control of all frequencies. High pass, Low pass and band pass, with resonance and frequenci controls. You could omit the knobsyou don't use much  and substitute them with fixed resistors to make the knob count lower (5) The foot control is cool but omitable if you want. (as in the original article in  Electronic projects for musicians book) It's a simple circuit otherwise.

John

[alderbody]

Do you have a schematic for that circuit Alderbody? Just curious about the gain control. Is it just a volume control at the end of the whole circuit or an actual gain control?

Thanks

John

Hey John,

nothing really exotic here... It's the classic Vox Wah circuit (inductor Wah).
The pcb was from GGG, although it's been heavily modded.

The gain control is just the Q1 Emitter resistor replaced by a pot,
but with some tricks (tapering resistor, etc) that don't allow it to "fall" below 200Ohms, if i remember well.

That tiny toggle selects between two "sweep caps" for different ranges.

With the Ge tranny and the gain at full, it gives a sweetest boost around the center frequency selected by the control.

I really like it.

[Paul Marossy]

nothing really exotic here... It's the classic Vox Wah circuit (inductor Wah).
The pcb was from GGG, although it's been heavily modded.

The gain control is just the Q1 Emitter resistor replaced by a pot,
but with some tricks (tapering resistor, etc) that don't allow it to "fall" below 200Ohms, if i remember well.

That tiny toggle selects between two "sweep caps" for different ranges.

With the Ge tranny and the gain at full, it gives a sweetest boost around the center frequency selected by the control.

I really like it.

I have had thoughts about doing something similar. Gives me food for thought... 

[Paul Perry (Frostwave)]

If you look at the National Semiconductor LM13700 data sheet, the application notes include a voltage controlled filter with resonance control. What they don't say, is that it works OK on 9 volts.
I used it years ago with a basic  envelope follower input.
Can you use a pot for the control voltage? Yes.... but please put a 10K resistor in series with the CV, to avoid acidentally blowing the LM13700 whihc HATES to have more than 10mA or so thru its control pins. A simple current source is smoother.

[A.S.P.]

2mA (absolute max.)!

[Noplasticrobots]

Basic, your link isn't working, Got a schematic for that filter?

[John Lyons]

Here's the correct link below although there is no schematic I want to post. It's a craig anderton Design from his book . I can email it to you though.
Shoot me an email at basicaudiowv @ earthlink.net  (take out the spaces) and I will send you one.
My build, pics and audio clips are at: www.mrdwab.com/john   then > Pedals> State Variable Filter

John

[alderbody]

I have had thoughts about doing something similar. Gives me food for thought... 

I guess you won't regret it!

I use mine almost all the time and mostly before fuzzes and overdrives.
btw, it makes a great "inbetween" (not exactly a buffer...) for a FF - Wah setup.
It's awesome before Aron's Smash Drive, too.

...really happy with it!