[sdiy] Polymoog Resonator - no-pots equivalent

[Pete Hartman]

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
>>> _______________________________________________
>>> Synth-diy mailing list
>>> Synth-diy at synth-diy.org
>>> http://synth-diy.org/mailman/listinfo/synth-diy
>>>
>>
>>
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