[sdiy] Max Filter Cutoff

[Jacob Watters]

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
> <javascript:_e(%7B%7D,'cvml','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
> <javascript:_e(%7B%7D,'cvml','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 <javascript:_e(%7B%7D,'cvml','timr at circuitabbey.com');>
>
>
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