[sdiy] Real piano keyboards: any use?

[David G. Dixon]

Hey, D.:

I tried searching for asymmetric LPFs on the web, but came up empty-handed.
I can also find nothing about it in Horowitz and Hill.  So, let me see if I
understand you correctly:

My vision of a simple AR is two diodes in opposite directions feeding two
(variable, or just differently valued) resistors which then come together
across a single (typically fairly large) cap to ground.  Obviously, if the
voltage input has different polarities it will be shunted across the
different diodes, thus rendering the filtering asymmetric.

Using active rectifiers rather than just bare diodes would eliminate the
diode voltage drop and its associated crossover distortion, which would make
the device useful for filtering actual signals rather than just gate inputs.

Does this more or less correspond with what you are talking about?

Cheers,
Dave

David G. Dixon
Professor
Department of Materials Engineering
University of British Columbia
309-6350 Stores Road
Vancouver, B.C. V6T 1Z4
Canada
 
Tel 1-604-822-3679
Fax 1-604-822-3619
 
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> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-
> bounces at dropmix.xs4all.nl] On Behalf Of cheater cheater
> Sent: Thursday, January 29, 2009 1:34 PM
> To: synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] Real piano keyboards: any use?
> 
> No, if you feed an asymmetric LPF something other than a gate signal
> you won't get an AR signal out of it.
> 
> Think of sidechains in compressors. The loudness analyzers are
> (usually) asymmetric LPFs fed the rectified signal you put into the
> sidechain.
> 
> Cheers
> D.
> 
> On Thu, Jan 29, 2009 at 9:09 PM, David G. Dixon
> <dixon at interchange.ubc.ca> wrote:
> > Ah.  I get it.  It's an AR.
> >
> > David G. Dixon
> > Professor
> > Department of Materials Engineering
> > University of British Columbia
> > 309-6350 Stores Road
> > Vancouver, B.C. V6T 1Z4
> > Canada
> >
> > Tel 1-604-822-3679
> > Fax 1-604-822-3619
> >
> > "PERFECTA FINGAMUS SERVIAT NATURA"
> >
> > The information in this email and in any attachments is confidential and
> > intended solely for the attention and use of the named addressee(s).  It
> > must not be disclosed to any person without the writer's authority.  If
> you
> > are not the intended recipient, or a person responsible for delivering
> it to
> > the intended recipient, you are not authorized to and must not disclose,
> > copy, distribute, or retain this message or any part of it.
> >> -----Original Message-----
> >> From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-
> >> bounces at dropmix.xs4all.nl] On Behalf Of cheater cheater
> >> Sent: Thursday, January 29, 2009 12:27 PM
> >> To: synth-diy at dropmix.xs4all.nl
> >> Subject: Re: [sdiy] Real piano keyboards: any use?
> >>
> >> An AR is a non-symmetric LPF that you put a gate into and get an AR
> >> envelope out of.[1]
> >>
> >> An assymmetric LPF is an LPF where the 'slew rate'*is set separately
> >> for rising and falling signals.
> >>
> >> *(actually: time coefficients)
> >>
> >> [1] That's why different gate designs make your synth sound
> >> differently. It's all in the transient!
> >>
> >> Cheers
> >> D.
> >>
> >> On Thu, Jan 29, 2009 at 8:15 PM, David G. Dixon
> >> <dixon at interchange.ubc.ca> wrote:
> >> >> It does indeed!
> >> >> I think the best way to achieve this kind of control is to have a
> >> >> continuous optic distance sensor. This can give you acceleration
> >> >> output and position output.
> >> >> Imagine having a synth style keyboard with the position going to the
> >> >> volume of the voice, and the speed going (through a non-symmetric
> LPF
> >> >> with a long release) to the volume of the suboctave. This would be a
> >> >> great lead/pad patch.
> >> >
> >> > Did you mean "non-symmetric AR" as in fast attack, long release?
> What
> >> is a
> >> > non-symmetric LPF?
> >> >
> >> >
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> >
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