[sdiy] Polymoog Resonator - no-pots equivalent

sleepy_dog at gmx.de sleepy_dog at gmx.de
Tue Aug 22 22:00:34 CEST 2017


 > 2164 clones ... exponential control ... all that other stuff

Ok ok, shut up and take my money...
Eh, well, there's a "waiting list" at "Thonk", this makes me somewhat 
concerned. This feels like (not) buying bananas in East Germany again. 
Are the commies back? *looks under the sofa with heavy duty flashlight 
and a _hard_-cover edition of "Das Kapital" with attached beating handle*


Am 22.08.2017 um 21:20 schrieb Tom Wiltshire:
> The 2164 (any version) performs much better than the 13700. There’s no audible or measurable difference been reported between the SSM2164 originals and the V2164 clones, as far as I’m aware. It’s a much quieter chip.
>
> The exponential control is often quite useful too. For example, in our filtering application here, the exponential control response saves us needed to add an exponential convertor for the Frequency CV, and it provides a softer approach to resonance in the resonance VCA (this seems counterintuitive, but that’s because in an SVF, the resonance is often controlled by having a VCA control the *damping*). It also provides a linear-in-dB response for the final Gain VCA, which is what you want for mixing audio signals. So it’s a win in every case.
>
> I also find the virtual ground input very handy - you can mix signals straight into a 2164 VCA by just adding more resistors. Similarly, the current output allows you to mix the output from several VCAs by feeding them all directly to the same I-to-V stage (there’s a 4 channel mixer example in the data sheet that shows this). Very useful.
>
> HTH,
> Tom
>
> (removes Dave Dixon hat ;)
>
> ==================
>         Electric Druid
> Synth & Stompbox DIY
> ==================
>
>> On 22 Aug 2017, at 19:51, sleepy_dog at gmx.de wrote:
>>
>>
>>
>>> 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
>>>>>> _______________________________________________
>>>>>> Synth-diy mailing list
>>>>>> Synth-diy at synth-diy.org
>>>>>> http://synth-diy.org/mailman/listinfo/synth-diy
>>>> _______________________________________________
>>>> Synth-diy mailing list
>>>> Synth-diy at synth-diy.org
>>>> http://synth-diy.org/mailman/listinfo/synth-diy
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at synth-diy.org
>> http://synth-diy.org/mailman/listinfo/synth-diy
>




More information about the Synth-diy mailing list