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note about lowpass gates

note about lowpass gates

2006-05-16 by Gary Chang

I wanted to post a note about the "Lowpass Gate" and its usage
throughout electronic music, for the purpose of clarifying why some of
us have obsessed about them....

From the 200 Series Brochures, circa 1970s:

"The Model 292[Quad Voltage-Controlled Lopass Gate], with the
capability of simulating the spectral and amplitude changes that
accompany a receding sound source, is one of several Electric Music
Box modules that can deal with spatial localization and movement."

There were three opreation modes for these devices - filter, vca and
dual.  Obviously, when in dual mode, the lopass gate operates as both
- a filter(6db/oct) and a VCA.

This dual mode is the sound of Mort Subotnick's electronic
realizations of the 70's.  It has a characteristically "woody" chirp
to its transient character.  It is this mode that most of us who used
the old Buchlas miss, hence the quest for "LowPass Gates".

The issue with the recent versions of this circuit is that most of the
versions of the the LP gate is that they are too slow.  When hit with
a short transient, they tend to ring excessively, making the "uber
marimba" patch made famous by Subotnick all but impossible without
slapping a VCA after the gate to shorten the sound.  The old Buchla
had only a 1v ptp audio signals, so the vactrol didn't have as far to
go to open all the way up, compared to the 10v ptp audio signals found
on Wiard and many other systems, so it was very quick.  As a matter of
fact, even the new 200e has very slow lopass gates, needing a second
gate in VCA mode to shorten the ring.  This is not typical of the 70's
200 series 292 gates.

Then in comes the Borg2, and we have a perfect 10v ptp lopass gate -
even better than the original (which are 1v ptp and had a "dual
linear" - as opposed to logarithmic cv curve).  

I also love to use the original Borg Filter for multichannel panning
with the JAG, because it rolls off the distant channels (just like the
227 quad locator of the Buchla 200 system), while opening up to full
bandwidth where the sound is nearer.

So, that's the lowdown on this LowPass Gate business....

gary

Re: [wiardgroup] note about lowpass gates

2006-05-16 by Eyesaw

Thanks for the info Gary, Bill
Show quoted textHide quoted text
----- Original Message ----- 
From: "Gary Chang" <gchang@calarts.edu>
To: <wiardgroup@yahoogroups.com>
Sent: Tuesday, May 16, 2006 3:18 AM
Subject: [wiardgroup] note about lowpass gates


>I wanted to post a note about the "Lowpass Gate" and its usage
> throughout electronic music, for the purpose of clarifying why some of
> us have obsessed about them....
>
> From the 200 Series Brochures, circa 1970s:
>
> "The Model 292[Quad Voltage-Controlled Lopass Gate], with the
> capability of simulating the spectral and amplitude changes that
> accompany a receding sound source, is one of several Electric Music
> Box modules that can deal with spatial localization and movement."
>
> There were three opreation modes for these devices - filter, vca and
> dual.  Obviously, when in dual mode, the lopass gate operates as both
> - a filter(6db/oct) and a VCA.
>
> This dual mode is the sound of Mort Subotnick's electronic
> realizations of the 70's.  It has a characteristically "woody" chirp
> to its transient character.  It is this mode that most of us who used
> the old Buchlas miss, hence the quest for "LowPass Gates".
>
> The issue with the recent versions of this circuit is that most of the
> versions of the the LP gate is that they are too slow.  When hit with
> a short transient, they tend to ring excessively, making the "uber
> marimba" patch made famous by Subotnick all but impossible without
> slapping a VCA after the gate to shorten the sound.  The old Buchla
> had only a 1v ptp audio signals, so the vactrol didn't have as far to
> go to open all the way up, compared to the 10v ptp audio signals found
> on Wiard and many other systems, so it was very quick.  As a matter of
> fact, even the new 200e has very slow lopass gates, needing a second
> gate in VCA mode to shorten the ring.  This is not typical of the 70's
> 200 series 292 gates.
>
> Then in comes the Borg2, and we have a perfect 10v ptp lopass gate -
> even better than the original (which are 1v ptp and had a "dual
> linear" - as opposed to logarithmic cv curve).
>
> I also love to use the original Borg Filter for multichannel panning
> with the JAG, because it rolls off the distant channels (just like the
> 227 quad locator of the Buchla 200 system), while opening up to full
> bandwidth where the sound is nearer.
>
> So, that's the lowdown on this LowPass Gate business....
>
> gary
>
>
>
>
>
>
>
>
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>
>
>
> ---
> avast! Antivirus: Inbound message clean.
> Virus Database (VPS): 0620-0, 05/15/2006
> Tested on: 5/16/2006 4:53:53 AM
> avast! - copyright (c) 1988-2006 ALWIL Software.
> http://www.avast.com
>
>
> 



---
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Virus Database (VPS): 0620-0, 05/15/2006
Tested on: 5/16/2006 9:27:03 AM
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Re: note about lowpass gates

2006-05-16 by drmabuce

an edifying post, Mr. Chang.... thanks!

i'd like to add one small factoid:
The Buchla design for a lowpass gate exhibits a dynamic attenuation of
the harmonic spectrum that is very close to the characteristics of a
real physical sound source fading into the distance. I can't declare
whether this was a deliberate effort on Don Buchla's part or not, but
given his deep roots in physics, i'd be willing to bet it was no
accidental coincidence.

-doc


--- In wiardgroup@yahoogroups.com, "Gary Chang" <gchang@...> wrote:
Show quoted textHide quoted text
>
> I wanted to post a note about the "Lowpass Gate" and its usage
> throughout electronic music, for the purpose of clarifying why some of
> us have obsessed about them....
> 
> From the 200 Series Brochures, circa 1970s:
> 
> "The Model 292[Quad Voltage-Controlled Lopass Gate], with the
> capability of simulating the spectral and amplitude changes that
> accompany a receding sound source, is one of several Electric Music
> Box modules that can deal with spatial localization and movement."
> 
> There were three opreation modes for these devices - filter, vca and
> dual.  Obviously, when in dual mode, the lopass gate operates as both
> - a filter(6db/oct) and a VCA.
> 
> This dual mode is the sound of Mort Subotnick's electronic
> realizations of the 70's.  It has a characteristically "woody" chirp
> to its transient character.  It is this mode that most of us who used
> the old Buchlas miss, hence the quest for "LowPass Gates".
> 
> The issue with the recent versions of this circuit is that most of the
> versions of the the LP gate is that they are too slow.  When hit with
> a short transient, they tend to ring excessively, making the "uber
> marimba" patch made famous by Subotnick all but impossible without
> slapping a VCA after the gate to shorten the sound.  The old Buchla
> had only a 1v ptp audio signals, so the vactrol didn't have as far to
> go to open all the way up, compared to the 10v ptp audio signals found
> on Wiard and many other systems, so it was very quick.  As a matter of
> fact, even the new 200e has very slow lopass gates, needing a second
> gate in VCA mode to shorten the ring.  This is not typical of the 70's
> 200 series 292 gates.
> 
> Then in comes the Borg2, and we have a perfect 10v ptp lopass gate -
> even better than the original (which are 1v ptp and had a "dual
> linear" - as opposed to logarithmic cv curve).  
> 
> I also love to use the original Borg Filter for multichannel panning
> with the JAG, because it rolls off the distant channels (just like the
> 227 quad locator of the Buchla 200 system), while opening up to full
> bandwidth where the sound is nearer.
> 
> So, that's the lowdown on this LowPass Gate business....
> 
> gary
>

Re: [wiardgroup] note about lowpass gates

2006-05-16 by John Mahoney

At 03:18 AM 5/16/2006, you wrote:
>I wanted to post a note about the "Lowpass Gate" and its usage
>throughout electronic music, for the purpose of clarifying why some of
>us have obsessed about them....
>
>[snip]
>
>gary

Interesting! I always associated the LPG with the Subotnick marimba 
sound, but I hadn't thought of them (or Borg filters) for "spatial 
localization and movement". Guess I should be reading old Buchla 
brochures! Thanks for posting.
--
john

Re: [wiardgroup] note about lowpass gates

2006-05-16 by Romeo Fahl

As far as I've been able to tell, there's no difference between the 
vactrols (VTL2C3) that were used in the Buchla and the ones (VTL5C3)  
used in the modern lopass gate clones, other than the package.  Is the 
slowness and ringing really due to the difference in signal level? The 
Borg2 uses the Silonex vactrols, which are supposed to be much faster 
than the VTLs.

Romeo
Show quoted textHide quoted text
On May 16, 2006, at 12:18 AM, Gary Chang wrote:

> I wanted to post a note about the "Lowpass Gate" and its usage
> throughout electronic music, for the purpose of clarifying why some of
> us have obsessed about them....
>
> From the 200 Series Brochures, circa 1970s:
>
> "The Model 292[Quad Voltage-Controlled Lopass Gate], with the
> capability of simulating the spectral and amplitude changes that
> accompany a receding sound source, is one of several Electric Music
> Box modules that can deal with spatial localization and movement."
>
> There were three opreation modes for these devices - filter, vca and
> dual.  Obviously, when in dual mode, the lopass gate operates as both
> - a filter(6db/oct) and a VCA.
>
> This dual mode is the sound of Mort Subotnick's electronic
> realizations of the 70's.  It has a characteristically "woody" chirp
> to its transient character.  It is this mode that most of us who used
> the old Buchlas miss, hence the quest for "LowPass Gates".
>
> The issue with the recent versions of this circuit is that most of the
> versions of the the LP gate is that they are too slow.  When hit with
> a short transient, they tend to ring excessively, making the "uber
> marimba" patch made famous by Subotnick all but impossible without
> slapping a VCA after the gate to shorten the sound.  The old Buchla
> had only a 1v ptp audio signals, so the vactrol didn't have as far to
> go to open all the way up, compared to the 10v ptp audio signals found
> on Wiard and many other systems, so it was very quick.  As a matter of
> fact, even the new 200e has very slow lopass gates, needing a second
> gate in VCA mode to shorten the ring.  This is not typical of the 70's
> 200 series 292 gates.
>
> Then in comes the Borg2, and we have a perfect 10v ptp lopass gate -
> even better than the original (which are 1v ptp and had a "dual
> linear" - as opposed to logarithmic cv curve).
>
> I also love to use the original Borg Filter for multichannel panning
> with the JAG, because it rolls off the distant channels (just like the
> 227 quad locator of the Buchla 200 system), while opening up to full
> bandwidth where the sound is nearer.
>
> So, that's the lowdown on this LowPass Gate business....
>
> gary
>
>
>
>
>
>
>
>
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>

Re: note about lowpass gates

2006-05-17 by Gary Chang

Romeo,

Probably it is more due to the "dual linear" cv response that made the
older gates shut off faster - (this exclusively Buchla response
circuit also made the gate not open for the first 60% of the cv range,
too...).  

The Borg1 has true logarithmic cv response, and along with the 10 ptp
range, I think that it makes its response slower than the old 292. 
The Borg2 solves the slower release by the faster Silonex vactrols,
making it, IMHO, even better than original 292 LP gate, because it has
the true log cv input, so it can be more subtly controlled via cv.

gary

 

--- In wiardgroup@yahoogroups.com, Romeo Fahl <rfahl@...> wrote:
Show quoted textHide quoted text
>
> As far as I've been able to tell, there's no difference between the 
> vactrols (VTL2C3) that were used in the Buchla and the ones (VTL5C3)  
> used in the modern lopass gate clones, other than the package.  Is the 
> slowness and ringing really due to the difference in signal level? The 
> Borg2 uses the Silonex vactrols, which are supposed to be much faster 
> than the VTLs.
> 
> Romeo
> 
> On May 16, 2006, at 12:18 AM, Gary Chang wrote:
> 
> > I wanted to post a note about the "Lowpass Gate" and its usage
> > throughout electronic music, for the purpose of clarifying why some of
> > us have obsessed about them....
> >
> > From the 200 Series Brochures, circa 1970s:
> >
> > "The Model 292[Quad Voltage-Controlled Lopass Gate], with the
> > capability of simulating the spectral and amplitude changes that
> > accompany a receding sound source, is one of several Electric Music
> > Box modules that can deal with spatial localization and movement."
> >
> > There were three opreation modes for these devices - filter, vca and
> > dual.  Obviously, when in dual mode, the lopass gate operates as both
> > - a filter(6db/oct) and a VCA.
> >
> > This dual mode is the sound of Mort Subotnick's electronic
> > realizations of the 70's.  It has a characteristically "woody" chirp
> > to its transient character.  It is this mode that most of us who used
> > the old Buchlas miss, hence the quest for "LowPass Gates".
> >
> > The issue with the recent versions of this circuit is that most of the
> > versions of the the LP gate is that they are too slow.  When hit with
> > a short transient, they tend to ring excessively, making the "uber
> > marimba" patch made famous by Subotnick all but impossible without
> > slapping a VCA after the gate to shorten the sound.  The old Buchla
> > had only a 1v ptp audio signals, so the vactrol didn't have as far to
> > go to open all the way up, compared to the 10v ptp audio signals found
> > on Wiard and many other systems, so it was very quick.  As a matter of
> > fact, even the new 200e has very slow lopass gates, needing a second
> > gate in VCA mode to shorten the ring.  This is not typical of the 70's
> > 200 series 292 gates.
> >
> > Then in comes the Borg2, and we have a perfect 10v ptp lopass gate -
> > even better than the original (which are 1v ptp and had a "dual
> > linear" - as opposed to logarithmic cv curve).
> >
> > I also love to use the original Borg Filter for multichannel panning
> > with the JAG, because it rolls off the distant channels (just like the
> > 227 quad locator of the Buchla 200 system), while opening up to full
> > bandwidth where the sound is nearer.
> >
> > So, that's the lowdown on this LowPass Gate business....
> >
> > gary
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
> >
>

Distance and humidity

2006-05-17 by Grant Richter

> Interesting! I always associated the LPG with the Subotnick marimba 
> sound, but I hadn't thought of them (or Borg filters) for "spatial 
> localization and movement". Guess I should be reading old Buchla 
> brochures! Thanks for posting.

The effect is high frequency roll off over distance with humidity (adds friction to air).
That was the error in the speed of sound measurement variation that Newton never solved. It 
took 200 years after his death to figure it out (according to PBS).

The VCA (or Combo) mode is 6 dB per octave, probably average humidity. 3 dB / Oct would 
be dry air and 12 dB / Oct would be a visably foggy night (just guessing).

Also the 6 dB output of the Boogie can be used for the same effect.

To Summarize: Humidty forms a lowpass filter over distance in air. To simulate this effect in 
panning, use low pass gates (Borg, Boogie) instead of plain VCAs.

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