[sdiy] Max Filter Cutoff

[Quincas Moreira]

Sweet, thanks, will do!

On Mon, Oct 24, 2016 at 11:55 AM, Tom Wiltshire <tom at electricdruid.net>
wrote:

> Olivier Gillet has several nice 2164 filter examples on the Mutable
> Instruments site. Ask me if you can't find them.
>
> Tom
>
> On 24 Oct 2016, at 15:50, Quincas <quincas at gmail.com> wrote:
>
> Dave, I have a spare 2164... Do you have any filter schematics you'd be
> willing to share with us diyers? I can make OTA filters just fine, but I'm
> not terribly familiar with the 2164 yet :)
>
> Cheers!
> Q
>
> Quincas Moreira
>
> On 23/10/2016, at 3:12 p.m., David G Dixon <dixon at mail.ubc.ca> wrote:
>
> I gave up on OTAs.  Once I discovered the 2164, I never looked back.  The
> only issue with them is that they must terminate at virtual ground, and
> this limits their uses a bit.  However, for most filters this isn't really
> a limitation, especially for cascaded-stage filters.
>
> ------------------------------
> *From:* Jacob Watters [mailto:jacobwatters at gmail.com
> <jacobwatters at gmail.com>]
> *Sent:* Sunday, October 23, 2016 11:37 AM
> *To:* David G Dixon
> *Cc:* Tim Ressel; synth-diy at dropmix.xs4all.nl
> *Subject:* Re: Max Filter Cutoff
>
> Ok thanks for the info. I think I need to adjust my circuit a bit. I am
> maxing out at 15k using LM13700 and 50pF caps. I get a better range with
> just a pot as a viltage divider and no expo conversion, so i am guessing my
> error is in the convertor. I am reading TH's book on the 3080 right now. I
> will redisgn the expo conversion based on what I am learning.
>
> Thanks!
>
>
> -Jacob Watters
>
> On Sunday, 23 October 2016, David G Dixon <dixon at mail.ubc.ca> wrote:
>
>> ...yeah, but if the filter doesn't go high enough, then it doesn't allow
>> all the higher overtones when its fully open.  In other words, it doesn't
>> fully open.  This can change the sound of waveforms even if it is above
>> your hearing range by subtle modulation.  I only hear up to a little less
>> than 13kHz myself.  Too much loud rock music.
>>
>> In any case, I would recommend 220pF as a good size for filter caps.
>> It's always worked well for me.  Of course, all my designs also use the
>> 2164 quad VCA chip for expo-controlled variable resistors, with the
>> standard 30k input resistor.  This fixes the "baseline" frequency of my
>> filters at something like 21kHz.
>>
>> ------------------------------
>> *From:* Synth-diy [mailto:synth-diy-bounces at dropmix.xs4all.nl] *On
>> Behalf Of *Tim Ressel
>> *Sent:* Sunday, October 23, 2016 10:48 AM
>> *To:* synth-diy at dropmix.xs4all.nl
>> *Subject:* Re: [sdiy] Max Filter Cutoff
>>
>> Since most ears stop at 16KHz I'd say its safe to stop there.
>>
>> --Tim (can't hear above 10K) Ressel
>>
>> On 10/23/2016 9:47 AM, Jacob Watters wrote:
>>
>> I am working on a filter and I was trying to get the maximum cutoff up to
>> 20kHz. I found that I needed much smaller caps than what is usually used in
>> most filters.
>>
>> Then I noticed that on the Arp 2600 the max filter cutoff is labelled as
>> 10kHz.
>>
>> What is the normal max cutoff for a 4-pole -24dB analog filter?
>>
>>
>> _______________________________________________
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>>
>>
>> --
>> --Tim Ressel
>> Circuit Abbeytimr at circuitabbey.com
>>
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-- 
Quincas Moreira
Test Pilot at VBrazil Modular
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