Cycling 74 » Topic: simulated pull-up resistor (make a signal slowly gravitate toward toward 1.0)

simulated pull-up resistor (make a signal slowly gravitate toward toward 1.0)

shhhh — Wed, 23 Mar 2011 23:00:23 +0000

I have an audio signal that i’m using to modulate other signals. Sometimes it goes dead, stopping at a value of 0.0 — when this happens, it silences the other signals, which is not what i want. How do i make it so that if the signal goes dead, it pulls back to a value of 1. instead of 0. ?

Re: simulated pull-up resistor (make a signal slowly gravitate toward toward 1.0)

Tim Lloyd — Wed, 23 Mar 2011 23:03:22 +0000

If it just fluctuates between 0 and 1, then you could just invert it [!-~ 1] … so when it goes “dead” it’s on 1 instead of 0. Would that work?

Re: simulated pull-up resistor (make a signal slowly gravitate toward toward 1.0)

shhhh — Wed, 23 Mar 2011 23:04:51 +0000

i guess i could use a snapshot~ and a counter and a crossfader, and crossfade to a signal of 1 whenever it counts to a certain number of 0 values in a row. But this seems like a really janky solution. Surely there’s a more elegant way?

Re: simulated pull-up resistor (make a signal slowly gravitate toward toward 1.0)

shhhh — Wed, 23 Mar 2011 23:06:43 +0000

Tim — that’s a cool idea, but the signal actually fluctuates between -1. and +1. I’d rather not have to do like a system-wide overhaul where i change all of the signal values.

Re: simulated pull-up resistor (make a signal slowly gravitate toward toward 1.0)

shhhh — Wed, 23 Mar 2011 23:09:56 +0000

I guess i could do a temporary downsample to take the signal to the 0-1 range, then invert it, then upsample it back to standard. but then i would lose some audio resolution, right?

edit: just realized this wouldn’t work at all; when upsampled the “dead” signal would sit at .5 instead of 0 or 1.

Re: simulated pull-up resistor (make a signal slowly gravitate toward toward 1.0)

Roman Thilenius — Thu, 24 Mar 2011 09:49:35 +0000

i think i know what you mean … but this is not possible with a
“dead” signal, you have to make sure that you know at which sample
(or vector) the modulation signal goes back to “no modulation” (i.e. 1).

then you have to replace this signal with the desired steady signal for
“no mnodulation”.

i use two poly~n for this … one holding a [sig~ 1] and the other one
lets pass the signal which is comsing from the user control or LFO
or whatever. and when one is turned on – the other one is turned off.

Re: simulated pull-up resistor (make a signal slowly gravitate toward toward 1.0)

stefantiedje — Thu, 24 Mar 2011 15:27:40 +0000

What kind of modulation? If its amplitude modulation, just add a fixed value, and eventually scale it back.
In amplitude modulation you should avoid zero crossings anyway, as that would create a reversed phase…

Stefan

Re: simulated pull-up resistor (make a signal slowly gravitate toward toward 1.0)

andrea agostini — Thu, 24 Mar 2011 17:33:18 +0000

This is how I would do it…
According to what you use it for, you might want to smooth the jump back to the incoming value when it goes back to != 0
hth
aa

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