Stuart

An LFO puts out a signal between 1 and -1. If the desired output shall oscillate between 2 and 0.5, I input my mod depth as 2

So to set the modulation depth (d) of the modulating signal (m) I use

Is there a more efficient way of doing this ? pow~ is hardly a processor friendly method :-)

desperately-seeking-efficient-modulation-depth

like lfo~ -> *~ 0.75 (to make the range 1.5) -> +~ 1.25

Jonathan Segel 4014 Brookdale Ave. Oakland, CA 94619

jsegel@magneticmotorworks.com magsatellite@yahoo.com

mul and add?
like lfo~ -> *~ 0.75 (to make the range 1.5) -> +~ 1.25

Jonathan Segel                 4014 Brookdale Ave. Oakland, CA 94619
jsegel@magneticmotorworks.com  magsatellite@yahoo.com


Do you want a wave that spends as much time between 0.5 and 1 as it 

does between 1-2 (implying an exponential distortion) or do you want a 

wave that is simply balanced between 0.5 and 2 (with a center of 1.25)

If it's the latter, I have an abstraction, PM.Scale~, that does this 

with matrix~ which is very fast. If it's the former, you could try 

doing a lookup table. In all likelihood, there's not going to be that 

many log scales that you'd need (especially if it's just for an lfo) 

and the difference between them will eventually be negligible given 

enough samples. Store the log scales in a buffer, and use the exponent 

to set the offset into the buffer~. (use a phasor~ to drive a wave~ 

for this, and have the offset points pass through a sah~ so you only 

grab a new offset at the beginning of the cycle)

Alternately, if pow~ is too expensive, you could try putting it in a 

poly~, downsampling it n times, and then using rampsmooth~ on the 

Do you want a wave that spends as much time between 0.5 and 1 as it 
does between 1-2 (implying an exponential distortion) or do you want a 
wave that is simply balanced between 0.5 and 2 (with a center of 1.25)

If it's the latter, I have an abstraction, PM.Scale~, that does this 
with matrix~ which is very fast.  If it's the former, you could try 
doing a lookup table.  In all likelihood, there's not going to be that 
many log scales that you'd need (especially if it's just for an lfo) 
and the difference between them will eventually be negligible given 
enough samples.  Store the log scales in a buffer, and use the exponent 
to set the offset into the buffer~.  (use a phasor~ to drive a wave~ 
for this, and have the offset points pass through a sah~ so you only 
grab a new offset at the beginning of the cycle)

Alternately, if pow~ is too expensive, you could try putting it in a 
poly~, downsampling it n times, and then using rampsmooth~ on the 
output.

I forgot to add that when the LFO outputs zero, then I need a value of 1.

So I guess it's the exponential that I'm after (anyone know a site for people who haven't even thought about maths for twenty five years ?).

I had already considered the wave~ lookup solution, maybe even the 2dwave~, which is a bit above me but I might as well get stuck into it now.

I forgot to add that when the LFO outputs zero, then I need a value of 1.
So I guess it's the exponential that I'm after (anyone know a site for people who haven't even thought about maths for twenty five years ?).

Desperately Seeking: Efficient modulation depth