[sdiy] Polymoog Resonator - no-pots equivalent

Michael E Caloroso mec.forumreader at gmail.com
Tue Aug 22 02:07:20 CEST 2017

I own a Polymoog with that resonator.  At 6dB/oct slope it is not very
effective.  If you want a resonator bank, 12dB slopes work much


On 8/21/17, Pete Hartman <pete.hartman at gmail.com> wrote:
> V2164 from Coolaudio is a good sub for the SSM2164 that doesn't cost
> collector prices, and is also available in SMT.
> Pete
> On Mon, Aug 21, 2017 at 2:16 PM, <sleepy_dog at gmx.de> wrote:
>> Thanks Tom, yes that cleared some things up. "go wild with this", yeah, I
>> have some ideas about that ;)
>> The 2164 being one of those ICs available for collector's prices?
>> Although
>> I might even have some of those hidden in some box... But I think I'm
>> going
>> to make this SMT.
>> Am 21.08.2017 um 19:46 schrieb Tom Wiltshire:
>>> Hi Steve,
>>> Yes, three multimode filters would be the same as the PolyMoog
>>> resonator.
>>> That’s what it is:
>>> http://www.synthfool.com/docs/Moog/polymoogresonator.jpg
>>> Note that the schematic shows us that the filters are state-variable
>>> filters (which we’d guessed anyway because of the HP, BP, and LP
>>> outputs)
>>> and that they’re *not* VCFs. They’re just based on op-amps. You also
>>> mention the slopes. A 12dB SVF has 6dB slopes for the BP output. That’s
>>> normal, since that’s a 2-pole bandpass filter, and it’s a 2-pole filter.
>>> The way I think about it is that you need to filter off both the low and
>>> the high frequencies, so you have to share the poles out to do the job!
>>> The Moog schematic is about as simple as such a thing could get, since
>>> it
>>> is pretty much just the three SVFs joined together. Personally I don’t
>>> like
>>> the way you have to change the response of all the filters together
>>> instead
>>> of individually, but that would be easy to change. Compare with this
>>> schematic:
>>> http://sound.whsites.net/articles/st-var-f1.gif
>>> Obviously you could go wild with this. Some years ago I built SVF+VCA
>>> modules around the 2164. This would be perfect for this, since you get a
>>> 2-pole VCF with VC resonance and a VCA all on the one chip.
>>> http://electricdruid.net/images/svf+vca.jpg
>>> I don’t seem to have the schematic online, but ask me if you’re
>>> interested.
>>> HTH,
>>> Tom
>>> ==================
>>>         Electric Druid
>>> Synth & Stompbox DIY
>>> ==================
>>> On 21 Aug 2017, at 17:16, Steve <sleepy_dog at gmx.de> wrote:
>>>> Hey experienced SDIYers,
>>>> say, would slapping together 3 {VCA, multi-mode VCF 12 dB/oct with Q
>>>> control} combos be the functional equivalent of the Moog Resonator?
>>>> (with
>>>> modified VCF control ranges, limited to 1 of those 3 bands each)
>>>> Although I faintly remember some of those multi mode VCFs having only 6
>>>> dB/oct slope on BP. Maybe not those. Are there designs with the same
>>>> slope
>>>> for all, or is this a general feature of such VCFs?
>>>>   My goal is to make something that can shape sounds similarly to the
>>>> Moog thing, as demo'ed on YT by some guy enhancing vocal and brass
>>>> sounds.
>>>> https://www.youtube.com/watch?v=_XUiJi5153Y
>>>> But in a much smaller box, without the battalion of pots.
>>>> I thought about just taking J.Haible's schematic and replacing all the
>>>> pots with MCP41HV digipots, but that'd be 14 (some are stereo), a bit
>>>> expensive *and* wiper noise, that doesn't taste well together ;)
>>>> - Steve
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