[sdiy] Fixed filter bank questions

David G Dixon dixon at mail.ubc.ca
Thu May 9 07:05:03 CEST 2019


That's a beautiful piece of work, Oren!!!  But, my experience with winding
the plastic line into my weed wacker tells me that I would have absolutely
no patience for winding my own inductors, so I'm gonna stick with the active
filter option.

I'm curious about one thing: Do you find that you ever use the individual
filter inputs, or was it (in retrospect) basically a waste of jacks?

Tonight I came up with a very elegant layout for all 12 dual BP filters, on
a piece of PCB which is only 2.1" x 6", so I'm now very stoked to build this
thing.



-----Original Message-----
From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Oren
Leavitt
Sent: Wednesday, May 08, 2019 4:18 PM
To: synth-diy at synth-diy.org
Subject: Re: [sdiy] Fixed filter bank questions


On 5/8/19 5:50 PM, David G Dixon wrote:
> Having said all that, don't ya just love the idea of these filter banks?
> The idea that something so electronically simple can have such smashing
> sonic results?  This is why I build synthesizers.


My clone of the Moog 914:

https://www.flickr.com/photos/synth64/albums/72157638017535176

That was a fun one to make!

White noise played thru various settings:

https://soundcloud.com/oren-leavitt/7914-fixed-filter-bank-test

https://soundcloud.com/oren-leavitt/7914-fixed-filter-bank-test-2

- Oren

>
>
> -----Original Message-----
> From: Tom Wiltshire [mailto:tom at electricdruid.net]
> Sent: Wednesday, May 08, 2019 3:24 PM
> To: David G Dixon
> Cc: *SYNTH DIY
> Subject: Re: [sdiy] Fixed filter bank questions
>
>
>> On 8 May 2019, at 22:04, David G Dixon <dixon at mail.ubc.ca> wrote:
>>
>> FIRST QUESTION:  Is there anything wrong with any of these concepts?
> Nope.
>
> I'd just flag up that Rod Elliott of the ESP audio pages makes a good
> argument that the use of 1000Hz as the "centre" of audio is misplaced.
> Instead, he goes for 640Hz as the geometric centre based on a ten octave
> range from 20Hz to 20.48KHz:
>
> http://sound.whsites.net/dwopa2.htm
>
> Having experimented with this, I've found that I agree with him. It makes
a
> good "mid" frequency. Consider it.
>
>
>> SECOND QUESTION:  Is there something fundamentally less desirable about
> doing it my way than doing it Yves' way?
>
> I don't think so. I'd have done it your way too, for the same reasons. It
> seems sensible to reduce the number of expensive caps (these are good
> quality close tolerance film caps you're using for something like this,
> right?!) and use resistors to set the frequency.
> Personally, I wouldn't fret too much about getting the resistor values
> absolutely spot-on, unless you're going to buy 1% tolerance caps too. If
the
> caps are 5%, there's not much point stressing to find an exact resistor
> value from the E192 series.
>
>   
> HTH,
> Tom=
>
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