MOTM

Hi everybody,

Can anybody tell me exactly what a Schmitt Trigger does? 2nd question:
Is a lag processor similar to a slew limiter? I am after portamento in a 
hungry way. Has anybody ever mentioned a joystick or other control voltage 
source module? Would be great for shifting audio gears during stage use or 
is a one on synth trance out session! Thanks for help,

Thomas White "T-Dub"
(*my friends call me this, short for TW and my shameless appreciation of 
tape echo and dub music technologies.)




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Basically, a Schmitt Trigger is a simple circuit (actually, they come in
chip form nowadays) which outputs a 'gate' (to use synthesizer speak)
depending upon the level of an input. The thresholds at which the output
goes high and then low again are independently controllable (this is called
'hysetersis,' which is probably how your furnace thermostat works, though
you control both thresholds with a single control... they are internally
staggered so that the furnace doesn't switch on and off too quickly, so the
"on" threshold is a few degrees higher than the "off."). So an incoming
voltage may rise and trigger the output to high at 4 volts, but as it falls,
it may not allow the output to fall low again until it goes down to 1 volt.
Hope that makes sense.

It's a useful component in a synthesizer. You could put such a device after
a lag integrator and make yourself a Gate Delay. I keep toying with that
idea but I have too many unbuilt MOTM kits on the bench right now...

Yes, a lag processor is one of many generic names for an integrator that
slows down and smoothes changes in voltages, the rate depending upon how
it's set. Other popular names are "glide," "slew limiting," "portamento,"
etc.

I believe Paul is currently working on such a module for release in the near
future.

Yeah, a joystick would be cool.

		-----Original Message-----
		From:	thomas white [mailto:djthomaswhite@...]
		Sent:	Thursday, January 27, 2000 12:27 PM
		To:	motm@onelist.com
		Subject:	[motm] Modular Growth Required

		From: "thomas white" <djthomaswhite@...>

		Hi everybody,

		Can anybody tell me exactly what a Schmitt Trigger does? 2nd
question:
		Is a lag processor similar to a slew limiter? I am after
portamento in a 
		hungry way. Has anybody ever mentioned a joystick or other
control voltage 
		source module? Would be great for shifting audio gears
during stage use or 
		is a one on synth trance out session! Thanks for help,

		Thomas White "T-Dub"
		(*my friends call me this, short for TW and my shameless
appreciation of 
		tape echo and dub music technologies.)




		______________________________________________________
		Get Your Private, Free Email at http://www.hotmail.com


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------------------------------------------------------------------------

Thomas,

From a catalog of another synth maker that makes a dual Schmitt Trigger:

"The DUAL SCHMITT TRIGGER is similar to the Dual Comparator, except that it
has been optimized for squaring up audio signals.  The Schmitt Trigger is a
single-input comparator with hysteresis.  Hysteresis means that the
switching thresholds are different for an input signal depending upon
whether it is going up or down.  This feature can be used with an envelope
and VCA functioning as a noise gate to reject low-level background noise in
audio applications. 
The Schmitt Triggers can be used for level detection, plus they have a
function unique to the module: both sections of the module can be used as a
"set-reset flip-flop".  Essentially, this is a memory element.  A pulse or
level into the SET input sets the R/S output high.  This output will stay
high independently of the activity at the SET input.  It is reset to zero
when the RESET input receives a pulse or sufficient level." 

A lag processor and a slew limiter are the same in my mind but there may be
subtle differences that I'm not aware of and yes, it will do portamento when
applied to keyboard CV.  Search the archives for discussion of exponential
vs. linear portamento.  Exponential is much more musical IMHO since it
matches the way singers tend to "slide" into notes.

There has been mention of joysticks it the past.  I love 'em!!  They can be
hard to find these days but a few manufacturers make them.  Joysticks have
more mechanical issues with their development than anything else.  An
alternative would be to take a MIDI keyboard with a joystick, like the Korg
M1, and use a MIDI/CV converter to send the voltages where you want.
Unfortunately, most of these joysticks are spring loaded.

	Eric

> -----Original Message-----
> From: thomas white [mailto:djthomaswhite@...]
> Sent: Thursday, January 27, 2000 12:27 PM
> To: motm@onelist.com
> Subject: [motm] Modular Growth Required
> 
> 
> From: "thomas white" <djthomaswhite@...>
> 
> Hi everybody,
> 
> Can anybody tell me exactly what a Schmitt Trigger does? 2nd question:
> Is a lag processor similar to a slew limiter? I am after 
> portamento in a 
> hungry way. Has anybody ever mentioned a joystick or other 
> control voltage 
> source module? Would be great for shifting audio gears during 
> stage use or 
> is a one on synth trance out session! Thanks for help,
> 
> Thomas White "T-Dub"
> (*my friends call me this, short for TW and my shameless 
> appreciation of 
> tape echo and dub music technologies.)
> 
> 
> 
> 
> ______________________________________________________
> Get Your Private, Free Email at http://www.hotmail.com
> 
> 
> --------------------------- ONElist Sponsor 
> ----------------------------
> 
> Looking for the lowest refinance rate for your mortgage?
> GetSmart.com can help. We'll help you find the loan you 
> need - quick, easy, and FREE click
> <a href=" http://clickme.onelist.com/ad/GetSmartRefinance 
> ">Click Here</a>
> 
> --------------------------------------------------------------
> ----------
>

Has anybody ever mentioned a joystick or other control voltage
> source module

A while ago this was a hot topic.  Basically you need a voltage source &
something to attenuate it with.
You could use an old mod wheel from a busted keyboard (or make your own), or
just pots w/ plain old
knobs, or a joystick, or whatever esoteric setup you want.

tomr

>
>
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