MOTM

I remember reading an essay a long time ago about modulating
frequency-domain devices. It claimed that a sinusoidal LFO was a
less-than-ideal source for modulation because of the log nature of the
frequency/pitch spectrum. A sin (or triangle, if we're being cheap) tends to
"rush" through the lower frequencies and take "too long" to sweep high,
giving a vertically off-balance cycling.

This article claimed that the best way to modulate these kinds of devices
was a negative-cycle full wave rectified sine. In other words, a wave that
looks kind of 'spiky' like this:

(format this diagram with a monospaced font such as Courier)

  |    |    |
_/ \__/ \__/ \__


Just thought I'd throw that into the discussion.

In fact, let me throw in another "beat the dead horse" comment:

Phasers work great with Shepard function generators as modulators...

Agreed. Just thought I'd throw that into the mix; experimentation might bear
that out, in which case it might be cool to add that "rectified" wave to the
rotary switch or whatever selects the LFO waveform for the Phaser module.

		-----Original Message-----
		> (format this diagram with a monospaced font such as
Courier)
		> 
		>   |    |    |   
		> _/ \__/ \__/ \__
		> 
		>>> Well, that wouldn't be too hard to do.  Turning a sine
wave into a rectified sine is certainly easy enough. :)

> From: "Tkacs, Ken" <Ken.Tkacs@...>
> 
> This article claimed that the best way to modulate these kinds of devices
> was a negative-cycle full wave rectified sine. In other words, a wave
that
> looks kind of 'spiky' like this:
> 
> (format this diagram with a monospaced font such as Courier)
> 
>   |    |    |
> _/ \__/ \__/ \__
> 
> 
> Just thought I'd throw that into the discussion.

Well, that wouldn't be too hard to do.  Turning a sine wave into a
rectified sine is certainly easy enough.
:)

You have my curiosity up.  I will have to try some half wave and full wave
LFO modulations.  I never would have thought of that.
LH

----------
> From: Tkacs, Ken <Ken.Tkacs@...>
> To: 'motm@onelist.com'
> Subject: [motm] Phaser Modulation
> Date: Wednesday, December 01, 1999 4:15 PM
> 
> From: "Tkacs, Ken" <Ken.Tkacs@...>
> 
> 
> Agreed. Just thought I'd throw that into the mix; experimentation might
bear
> that out, in which case it might be cool to add that "rectified" wave to
the

> rotary switch or whatever selects the LFO waveform for the Phaser module.
> 
> 
> 		-----Original Message-----
> 		> (format this diagram with a monospaced font such as
> Courier)
> 		> 
> 		>   |    |    |   
> 		> _/ \__/ \__/ \__
> 		> 
> 		>>> Well, that wouldn't be too hard to do.  Turning a sine
> wave into a rectified sine is certainly easy enough. :)
> 		
> 
>

In a message dated 12/1/99 7:34:20 AM, Ken.Tkacs@... writes:

>I remember reading an essay a long time ago about modulating
>frequency-domain devices. It claimed that a sinusoidal LFO was a
>less-than-ideal source for modulation because of the log nature of the
>frequency/pitch spectrum. A sin (or triangle, if we're being cheap) tends
>to
>"rush" through the lower frequencies and take "too long" to sweep high,
>giving a vertically off-balance cycling.

Thanks Ken! This was the point I was trying to make (not build in 2 MOTM 320s 
into the Phaser). But I also think that other LFO waveshapes produce 
identifiable (and popular) types of sweeps. For example, any LDR based phaser 
would (presumably) have a characteristic type of sweep that might be worth 
incorporating. If these could be implemented by VC (possibly by adding just a 
few components for say $20), all the better! If not, oh well.

>This article claimed that the best way to modulate these kinds of devices
>was a negative-cycle full wave rectified sine. In other words, a wave that
>looks kind of 'spiky' like this:

>(format this diagram with a monospaced font such as Courier)

>  |    |    |
>_/ \__/ \__/ \__

>Just thought I'd throw that into the discussion.

>In fact, let me throw in another "beat the dead horse" comment:
>Phasers work great with Shepard function generators as modulators... 

I agree wholeheartedly, maybe down the road apiece Paul will introduce one -- 
given time for us to acquire 8 VCOs, 8 VCFs, 8 Phasers, etc.

And Ken, this phaser will undoubtedly have a "KILL" setting! For self 
destruct, it is often just enough to plug the modules output into its input.

John B.
Oh yeah! Pole switching is nice and an envelope follower (even a cheesy one) 
might be an interesting idea, I've never tried it before.

In a message dated 99-12-01 09:34:22 EST, you write:

<<  negative-cycle full wave rectified sine. In other words, a wave that
 looks kind of 'spiky' like this: >>



ken, if my memory serves me correctly this sort of idea was used by craig 
anderton in the ( kit by paia ) hyperflange and chorus. this same sort of 
waveshape is producable via a dsg ( by another manufacturer ) feeding the 
envelope back into the control input and using negative biasing. using 
positive biasing produced a sort of overrounded / convex kind of waveshape. 
both were neat for assorted control purposes, phasing and otherwise.
best,
dave

On Thu, 2 Dec 1999, J. Larry Hendry wrote:

> Dave, I do happen to have the old Hyperflanger schematic.  It is built
> around a SAD1024 and 571.  I can send you a copy if you like.

  It also uses a CEM3340, if I recall.  $50 chip these days.

/**/

jlarryh@... writes:

>>But, I do not agree with the general concept that feature reduction because
 of incremental cost increases should be an icon of MOTM design.  If MOTM
 really means Mother of the Modulars, or Modular of the Millennium, then it
 should be just that.<<

I don't like to see compromises made either.  But when somebody is asking for 
the functionality of the MOTM-320 LFO to be placed in the Phaser, that is 
going too far.  Keep in mind, virtually all modular synths that have phaser 
modules don't provide any internal modulation at all.  You are expected to 
use other modules for that.  So the MOTM phaser has already gone beyond the 
others in that area.  The places to spend more money on are the phase shifter 
itself.  As I suggested before, negative feedback.  How about a rotatary 
switch to allow the user to choose 4,6,8,10,12 stages of phase shift like the 
Moog 12 stage phaser?  Someone else mentioned spreading/contracting the 
phaser bands/notches apart, for totally different phaser sounds.  The Nord 
Modular does that, and it gives you thousands of different phaser tones.  
These are the places to add features.

-Elhardt

> From: DAVEVOSH@...
> ken, if my memory serves me correctly this sort of idea was used by craig

> anderton in the ( kit by paia ) hyperflange and chorus. this same sort of

> waveshape is producable via a dsg ( by another manufacturer ) feeding the

> envelope back into the control input and using negative biasing. using 
> positive biasing produced a sort of overrounded / convex kind of
waveshape. 
> both were neat for assorted control purposes, phasing and otherwise.
> best,
> dave


Dave, I do happen to have the old Hyperflanger schematic.  It is built
around a SAD1024 and 571.  I can send you a copy if you like.

LH

> From: Elhardt@...
> I don't like to see compromises made either.  But when
> somebody is asking for the functionality of the MOTM-320
> LFO to be placed in the Phaser, that is 
> going too far. 

Agreed.  I'm not sure anybody really intended that.  Heck, that's what the
320 is for.

> Keep in mind, virtually all modular synths that have phaser 
> modules don't provide any internal modulation at all.  You are expected
to 
> use other modules for that.  So the MOTM phaser has already gone beyond
the 
> others in that area.  The places to spend more money on are the phase
shifter 
> itself.  As I suggested before, negative feedback.  How about a rotatary 
> switch to allow the user to choose 4,6,8,10,12 stages of phase shift

Ooh. That sounds cool.  I like rotary switches.  And, standard MOTM knobs
are big enough to handle the job.

LH

> On Thu, 2 Dec 1999, J. Larry Hendry wrote:
> Dave, I do happen to have the old Hyperflanger schematic.  It is built
> around a SAD1024 and 571.  I can send you a copy if you like.

> From: The Old Crow <oldcrow@...>
>   It also uses a CEM3340, if I recall.  $50 chip these days.

Of course.  Silly me sitting here looking at only the audio section of the
thing.  The modulation section of the schematic does indeed have a 3340
along with CMOS 4046 and 4041, and of course some op amps.

I certainly would never build from this schematic especially when Paul is
making us such a super one.  However, the good news is that Paul's December
sale has reduced the price of CEM chips.  :-)

I was looking to see if I could identify the feature that Dave was talking
about.  It isn't jumping out at me.  But then, I don't see as well as I
used to. :-)

LH

My $0.02:  This reasoning makes perfect sense to me.

		-----Original Message-----
		From: Elhardt@...

		Keep in mind, virtually all modular synths that have phaser 
		modules don't provide any internal modulation at all.  You
are expected to 
		use other modules for that.  So the MOTM phaser has already
gone beyond the 
		others in that area.  The places to spend more money on are
the phase shifter 
		itself.  As I suggested before, negative feedback.  How
about a rotatary 
		switch to allow the user to choose 4,6,8,10,12 stages of
phase shift like the 
		Moog 12 stage phaser?  Someone else mentioned
spreading/contracting the 
		phaser bands/notches apart, for totally different phaser
sounds.  The Nord 
		Modular does that, and it gives you thousands of different
phaser tones.  
		These are the places to add features.