6 May
2003
6 May
'03
7:34 a.m.
Hi,
Sorry if this is the wrong list. I have never found a list with people
who can help me with these kind of questions.
I am trying to figure out how a rectifier works in code. I have created
something like it using tanh() distribution ( which will turn a sine
wave into a sort-of-square wave). I can also achieve it with hard
clipping/saturation. In the same sense I'd also like to know how a
smooth operation works as well. I can not find any source code or
explanations to help me figure out the algorithm yet.
My other question is how are exponential signals generated? I want to
experiment with exponential FM. My only understanding of Exp. Fm is that
it sweeps half down and full up ( at 440hz, it would sweep 220hz down
and 880 hz up). I haven't much of an idea how this is achieved. How do I
convert a sine wave into an exponential signal for Exp FM?
6 May
6 May
8:15 a.m.
Hallo,
nickt hat gesagt: // nickt wrote:
Sorry if this is the wrong list. I have never found a
list with people
who can help me with these kind of questions.
Check out the code archive on musicdsp.org.
I am trying to figure out how a rectifier works in
code. I have created
something like it using tanh() distribution ( which will turn a sine
wave into a sort-of-square wave). I can also achieve it with hard
clipping/saturation. In the same sense I'd also like to know how a
smooth operation works as well. I can not find any source code or
explanations to help me figure out the algorithm yet.
Musicdsp has several examples and you also could take a look at
Steve's plugins. There are several ways to rectify a signal. The
hardest way is doing convolution with a matching impulse response. The
easiest way seems to be waveshaping: There you use a lookup table that
multiplies your input signal with values that smoothly approach 0 when
your signal approaches 1.
My other question is how are exponential signals
generated? I want to
experiment with exponential FM. My only understanding of Exp. Fm is that
it sweeps half down and full up ( at 440hz, it would sweep 220hz down
and 880 hz up). I haven't much of an idea how this is achieved. How do I
convert a sine wave into an exponential signal for Exp FM?
I don't quite understand this. To sweep the frequency, you just apply
a function on the frequency input. Simplified like
out = sin(exp(freq))
ciao
--
Frank Barknecht _ ______footils.org__
9:19 a.m.
On Tue, May 06, 2003 at 12:05:00 +0200, Frank Barknecht wrote:
Definatly. Check the mailing list archives too.
I wouldn't look at my stuff, I implemented rectification, but its
mathematically ideal (ie. fabs()) or sinus based. If you are looking at
emulating class B amplitification, I think its generally easier to go for
the whole thing, if you really want a working rectifier simualtion, then
you might be able to do it with spice, but IANASU (I Am Not A Spice User).
#include <exponential-fm-is-pm.rant>
the frequency of an oscilator is given by:
osc_freq = base_freq * pow(2.0, pitch_mod) + freq_mod;
where pitch_mod is the "exponential FM" in octaves, ie +1.0 will shift up
by one octave, eqivalent to the old analogue 1volt/octave system.
- Steve
Sorry if this
is the wrong list. I have never found a list with people
who can help me with these kind of questions.
Check out the code archive on musicdsp.org. I am trying to
figure out how a rectifier works in code. I have created
something like it using tanh() distribution ( which will turn a sine
wave into a sort-of-square wave). I can also achieve it with hard
clipping/saturation. In the same sense I'd also like to know how a
smooth operation works as well. I can not find any source code or
explanations to help me figure out the algorithm yet.
Musicdsp has several examples and you also could take a look at
Steve's plugins. There are several ways to rectify a signal. The hardest way is doing convolution with a matching
impulse response. The
easiest way seems to be waveshaping: There you use a lookup table that
multiplies your input signal with values that smoothly approach 0 when
your signal approaches 1.
Yes, but then you have to beware of aliasing, you could probably fix that
with oversampling however.
My other
question is how are exponential signals generated? I want to
experiment with exponential FM. My only understanding of Exp. Fm is that
it sweeps half down and full up ( at 440hz, it would sweep 220hz down
and 880 hz up). I haven't much of an idea how this is achieved. How do I
convert a sine wave into an exponential signal for Exp FM?
I don't quite understand this. To sweep the frequency, you just apply
a function on the frequency input. Simplified like
out = sin(exp(freq))
9:34 a.m.
New subject: [linux-audio-dev] Rectifier algorithm and Exponential FM question
out = sin(exp(freq))
That's my guess. I
know ALSA Modular has Exponential FM, but I have not
found out where is doing it or how.
My guess is that an exponential jack does something similar like this
and than passes it to circuit for modulation. So it might do something
like exp(signal).
The signal itself is modulated between 1 octave down and 1 octave up.
A straight exp(x) will not do that. It has to be a formula of some sort.
8:33 a.m.
--- nickt <nicktsocanos(a)charter.net> wrote: > Hi,
Sorry if this is the wrong list. I have never found a
list with people
who can help me with these kind of questions.
I am trying to figure out how a rectifier works in code. I have created
something like it using tanh() distribution ( which will turn a sine
wave into a sort-of-square wave). I can also achieve it with hard
clipping/saturation. In the same sense I'd also like to know how a
smooth operation works as well. I can not find any source code or
explanations to help me figure out the algorithm yet.
My other question is how are exponential signals generated? I want to
experiment with exponential FM. My only understanding of Exp. Fm is that
it sweeps half down and full up ( at 440hz, it would sweep 220hz down
and 880 hz up). I haven't much of an idea how this is achieved. How do I
convert a sine wave into an exponential signal for Exp FM?
freq * pow(2.0, sin(x))
will modulate a frequency in this way.
e.g. 440 * pow(2.0, 1.0) will raise by 1 octave (880Hz)
440 * pow(2.0, -1.0) will lower by 1 octave (220Hz)
So an unscaled sine wave will do a 2 octave sweep.
Mike
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4 comments
4 participants
participants (4)
-
Frank Barknecht -
Mike Rawes -
nickt -
Steve Harris