Resonance circuit ?

[Northwave]

I recently sold my Boss ME-50 COSM multieffectpedal, because I mostly used mye DIY overdrive pedals.
But it featured a really neat sound on the expressionpedal called Resonance, which kinda masks/blurs your signal and cuts treble in a really cool way.
Im intrested in what the effect does electro/acoustically, and if it can be simulated with some sort of sweeped filter.
Anyone got any clues?

Jason Newstead in Metallica used it live on Cunning Stunts, and its used in the intro of Mnemic - Deathbox.
I'll try to dig up a soundsample.

EDIT: it must be somehow related to a wah, because it responds in almost the same way, only that it attenuated treble and some mid instead of boosting it.

EDIT2: I think this is somewhat what I'm looking for:
"Resonance effect originates from an artifact in the original cutoff filter used in old hardware synthesizers. It is narrow band of frequencies, near the cutoff level, where the sound is amplified. Today this artifact can be easily avoided, but it is still available though, because it can be used as a special effect. Changes in the cutoff level together with high resonance produces interesting phaser-like effect, which is one of the reasons for the popularity of the TB-303 synthesizer."

EDIT3: http://www.softlab-nsk.com/ddclipro/audiofx/profres.gif
Perhaps this is all of it?

[d95err]

I recently sold my Boss ME-50 COSM multieffectpedal, because I mostly used mye DIY overdrive pedals.
But it featured a really neat sound on the expressionpedal called Resonance, which kinda masks/blurs your signal and cuts treble in a really cool way.
Im intrested in what the effect does electro/acoustically, and if it can be simulated with some sort of sweeped filter.
Anyone got any clues?

Jason Newstead in Metallica used it live on Cunning Stunts, and its used in the intro of Mnemic - Deathbox.
I'll try to dig up a soundsample.

EDIT: it must be somehow related to a wah, because it responds in almost the same way, only that it attenuated treble and some mid instead of boosting it.

EDIT2: I think this is somewhat what I'm looking for:
"Resonance effect originates from an artifact in the original cutoff filter used in old hardware synthesizers. It is narrow band of frequencies, near the cutoff level, where the sound is amplified. Today this artifact can be easily avoided, but it is still available though, because it can be used as a special effect. Changes in the cutoff level together with high resonance produces interesting phaser-like effect, which is one of the reasons for the popularity of the TB-303 synthesizer."

EDIT3: http://www.softlab-nsk.com/ddclipro/audiofx/profres.gif
Perhaps this is all of it?

A wah is a resonant filter. The frequency response looks exactly like on the picture you posted. The difference is probably in what is being modulated. A wah modulates the cutoff frequency of the filter. Perhaps the resonance effect modulates something else, e.g. the Q value.
So, it's difficult to tell from the BOSS text what the difference between the resonance effect and a typical wah is. Perhaps it modulates the Q value of the filter instead of the cutoff frequency.

[Northwave]

The wah is a resonant bandpass isnt it?

Heres a sample of a resonator (synth-filter) with a resonant lowpass in series with a resonant hi-pass, both seperatly sweepable.
Indicates the basics of what I wish to do, only I mostly want the ability to cut/sweep treble-mid like you are hearing in the first 30 secs or so.
(EDIT: giving a muffled/kinda bassy sound when activated and a normal freq response when not)
http://www.frostwave.com/soundfiles/resonantor/res_drumsample1.mp3

Perhaps a preset resonant lowpass at some mid-frequency mixed with a dry signal would do?
Sweep controls wet/dry ratio, and therefore both high-freq component and Q factor?

"Resonance Filter in the TC Electronic G-Major
The Resonance filters are basically a Hi and Lo Cut filter that can be swept up and down the frequency range. When the Resonance (Q-factor) parameter is increased, the filters peak and the cutoff frequency gets very narrow and very steep."

[Elektrojänis]

EDIT2: I think this is somewhat what I'm looking for:
"Resonance effect originates from an artifact in the original cutoff filter used in old hardware synthesizers. It is narrow band of frequencies, near the cutoff level, where the sound is amplified. Today this artifact can be easily avoided, but it is still available though, because it can be used as a special effect. Changes in the cutoff level together with high resonance produces interesting phaser-like effect, which is one of the reasons for the popularity of the TB-303 synthesizer."

That's kind of funny... They make it sound like the resonance was something that was hard to avoid and only modern stuff could avoid it. How on earth they can even say like that almost all analog synths (the tb-303 included) have a control for the amount of resonance that goes from absolutely no resonance to heavy resonance (sometimes even self oscillation of the filter)...

As for the question, I'd say taht it's probably just a different (than the normal wahs) type of filter with a different cutoff range. Different filters sound different (even if they are all low pass). I'd still quess that the cutoff is modulated by the pedal as it usually sounds most interesting, but without hearing a sample I'm not sure.

[Northwave]

I knew I should have recorded a sample before sending that ME-50 away, I cant seem to find a sample that does exactly the same on the internet either.

Also I'd like to note that the qoute in my first post is not from Boss, but from an indepentent site explaining a resonant filter (I had no clue, so had to google it).

EDIT: can you give examples of resonant filter schematics? or perhaps you know of any good sources ?
I only seem to find digital things, or inductor based (which I want to avoid).
Using a low-pass in paralell with a highQ bandpass should work for creating a lowpass resonant filter? Would make sweeping kinda complicated tho.

[Elektrojänis]

The wah is a resonant bandpass isnt it?

Some of them are, but the usual Vox/Crybaby style wahs are resonant Low-Pass.

Heres a sample of a resonator (synth-filter) with a resonant lowpass in series with a resonant hi-pass, both seperatly sweepable.
Indicates the basics of what I wish to do, only I mostly want the ability to cut/sweep treble-mid like you are hearing in the first 30 secs or so.
(EDIT: giving a muffled/kinda bassy sound when activated and a normal freq response when not)
http://www.frostwave.com/soundfiles/resonantor/res_drumsample1.mp3

To me that sounds like the cutoffs are just modulated. If you wan't the muffled sound with the bass intact, use a resonant low pass filter. If you wan't the thin sound with treble intact, use resonant high pass. If you want to cut both, treble and bass, you might hve to use both but band pass might do it. It depends on how you want to modulate it antd do you wan't two resonant peaks or is one enough.

Perhaps a preset resonant lowpass at some mid-frequency mixed with a dry signal would do?
Sweep controls wet/dry ratio, and therefore both high-freq component and Q factor?

If you want sweeping like in that sound sample you should not mix any dry in... Just modulate cutoff of the filter/filters.

Also I'd like to note that the qoute in my first post is not from Boss, but from an indepentent site explaining a resonant filter (I had no clue, so had to google it).

Oh... Sorry... It looked just like the marketing oriented manuals of some manufacturers.

EDIT: can you give examples of resonant filter schematics? or perhaps you know of any good sources ?

There was one on the net years ago that was kind of simple and worked (I even made some kind of prototype, but never got around putting it in a box), but I'm not sure if it can be found anymore. It was actually meant as a wah, but it sounded much more synth-like than the "standard" things. I'll post a link if I can find it.

Oh... If you want to get more synth-like, make sure your wah is after overdrive/distortion/fuzz (if any) and not before. It makes a real big difference. It's not possible to use amp overdrive then though...

[Northwave]

Well at least now I know what I'm looking for. A resonant low-pass with sweepable cutoff frequency.

So far I've found these two schematics:
http://www.synthfool.com/schematics/polyvcf.jpg (way to complicated IMO)
http://www.cgs.synth.net/modules/cgs35_syntha_vcf.html (diode ladder, looks interesting, but is the sweeping smooth?)

Since wah-pedals use inductors, a simple gyrator-design might be possible ?
And a ordinary low-pass in series with a high-Q bandpass might do the trick as well?

[slacker]

If you're interested in the cgs35 then check out my slackfilter that's basically the cgs35 converted for 9 volt use. Makes a great auto wah and you could easily add an expression pedal to it if you wanted.
If you want something simpler try one of Tim Escobedos Quasi VCFs they make good lowpass filter sounds and can be swept with an expression pedal. http://www.geocities.com/tpe123/folkurban/fuzz/simplevcf.gif

[Northwave]

That Quasi looks like something I'll have try out, thanks alot!;)

Is the fitite number of steps in a diode ladder audible? Is there a noticable "switching" in the frequency response of the filter?

I've also found a OPAMP inductor wah that I might modify for gyrator use, it looks quite promising too.
http://www.geofex.com/Article_Folders/wahpedl/wah7.gif

[slacker]

Is the fitite number of steps in a diode ladder audible? Is there a noticable "switching" in the frequency response of the filter?

No you get a smooth sweep.

[Elektrojänis]

Is the fitite number of steps in a diode ladder audible? Is there a noticable "switching" in the frequency response of the filter?

I'm not sure but I would quess not. Many analog synths use diode ladder and transistor ladder filters and they produce smooth sweeps.

The thin I mentioned earlier is Wha-Filter on this page: http://www.fortunecity.com/tinpan/humperdinck/223/effect.htm

Straight link to the schem: http://www.fortunecity.com/tinpan/humperdinck/223/mormod.gif

The link to the text is broken now, but it can be reached through archive.org wayback machine: http://web.archive.org/web/20050906133437/http://www.fortunecity.com/tinpan/humperdinck/223/whaf.htm

I think that schematic was updated some way after I tried it.

Also check out "Multiple Feedback Opamp Circuits" on www.geofex.com article "The Technology of Wah Pedals". Another thong that probably could be used is the filter section from Dr. Quack.

[slacker]

I had a look at the ME50 user manual online and it doesn't really say what the resonance control is except to say that it's based on analogue synth filters so it probably is just a lowpass filter where the cutoff frequency is set by the expresion pedal. In which case one of Tim's VCFs will definately get you the right sort of sound.

[Paul Perry (Frostwave)]

There's the low pass voltage controlled filter in the LM13700 data sheet, as well.
This will work at 9v wiht the biasing fixed. (the notes have + - 15v rails)

What happens is, with low resonance, the frequency response looks like you would imagine, flat and then falling off.
But as you increase the resonance, the slope down after the cutoff frequency becomes sharper, and at the same time, a peak appears at the cutoff frequency. And with more feedback the peak increases, until eventually the system oscillates.

And why the MS20 type filter sounds interestign is 1. with the resonance up, sweeping the frequency of the peak is very intense, and 2. the nonlinearities in the feedback loop (see diodes) and the distortion inherent to the OTA stages.

You will find a lot of stuff if you google for
        MS20 filter schematic
including this 3080 version  http://www.uni-bonn.de/~uzs159/rs20.png

[Nasse]

I have Korg Pandora and B* V-Amp2 and both have such filter, or about there, works nice. Has anybody tried this? http://www.sugardas.lt/~igoramps/article57.htm

[Jaicen_solo]

My cousin has an ME-50 which I spent some time playing around on. I'm pretty sure the resonant filter is just your bog-standard low-pass affair as has already been mentioned. The easiest way to get a similar sound that I can think of in the DIY realm is the Parapedal so that might be worth checking out.

[Northwave]

Thanks for all the replies and circuit recommendations!
I've now found the circuit that I want, using a State Variable OPamp Lowpass Filter.
(http://www.analog.com/Analog_Root/static/techSupport/designTools/interactiveTools/filter/filter.html)
It's nearly perfect, adjustable Q without affecting anything else, and Q independent of frequency.
The only thing is that it needs dual pots for freq control, but thats not really a problem, most expressionpedals are stereo anyways.