[sdiy] Anyone do a voltage controlled "Tilt" Filter?

houshu at muj.biglobe.ne.jp houshu at muj.biglobe.ne.jp
Tue Jun 1 15:21:13 CEST 2021


Hello Neil and List,

Toshiba TA8184 is a one-chip dual voltage-controlled tone/pan/amplitude.
Datasheet can be found easily.
You can build a tilt tone controller just by adding CV mixers.
If you connect the two channels in series, the effect can be more drastic I guess.

I've seen a DIY module with schematic, but, can't remember where it is.

Sam HOSHUYAMA
Kawasaki, JAPAN

> 2021/05/31  2:21 Neil Harper via Synth-diy <synth-diy at synth-diy.org> wrote:
> 
> 
> I recently breadboarded this tilt equalizer filter as found on EDN:
> 
> https://www.edn.com/implement-an-audio-frequency-tilt-equalizer-filter/
> 
> A similar (the same?) circuit is shown here:
> https://sound-au.com/articles/eq.htm#s10
> 
> It's pretty cool, low parts count and can sound interesting - i'm kinda
> digging it to eq an fx for sample.
> 
> of course my next question was "how can I get this under voltage control"?
> 
> here's what I plan to try, maybe you can steer me in the right direction.
> 
> my first guess was to replace the potentiometer (P1) with two
> vactrols/LDRs, but I'm not sure how to basically 'crossfade' the two
> vactrols in opposite directions and I think the response curves of the
> vactrols with regard to voltage input (light) and resistance are far
> from linear.
> 
> i've read that OTA's like the LM13700 (the monty python chip) can be
> used as voltage controlled resistors, but I've never seen them
> implemented as a pair replacing a potentiometer - so I don't know if
> that route is possible either.
> 
> my last guess was wondering if an equivalent circuit could be made by
> combining a lowpassed and hipassed audio signal and then crossfading
> them. I can imagine it would somewhat similar, but I'm not sure if you
> would get the same totally flat frequency response in the middle setting.
> 
> 
> 
> --
> /// Neil Harper
> /// Every Wave is New Until it Breaks
> 
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