[sdiy] Polymoog Resonator - no-pots equivalent

sleepy_dog at gmx.de sleepy_dog at gmx.de
Tue Aug 22 20:51:55 CEST 2017



 > No, the CoolAudio V2164 is widely available and cheap - and in both 
DIP and SMD

*V*2164, eh?
http://m.memegen.com/ub1ae4.jpg

I will at least put the existence of those into the back of my head.
One  needs to get them at 3rd party distributors instead directly, eh? 9 
bucks at small numbers otherwise... plus probably not so nice shipping 
costs to my country.
But if this thing has 4 complete VCAs and only minimal (?) support 
circuitry, it sounds like a nice IC.

Do they perform significantly better than LM13700 based VCAs (and as 
VCFs, too) with similar parts count?
And if so - does it matter for this particular project?

What's even cheaper than cheaply sourced parts is using stock you 
already have.
And I have roughly one kilogram* prime LM13700 at home. Might as well 
use them :-D

* slightly exaggerated. May be 150g.


Steve


> No, the CoolAudio V2164 is widely available and cheap - and in both DIP and SMD. The original Analog Devices SSM2164 might cost silly money by now, but it’s the same thing.
>
> Tom
>
> ==================
>         Electric Druid
> Synth & Stompbox DIY
> ==================
>
>> On 21 Aug 2017, at 20:16, 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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