filter changing tremolo.

[deadastronaut]

so while i was watching the earth from  space again, i saw sandra bullock whizz by screaming her head off,   and it got me thinking....

here goes..thinking aloud..

LFO-1:  triangle/sine --- ...driving a Q&D filter or 2 /bass balls filters/phaser ...so we get the usual : BBBBbbbbbwwwahhhhawwbbbbbBBB....but a nice slow ,and even smooth sweep...

but have that signal interupted with a choppy tremolo/ LFO-2...might be an interesting option/addition for an otherwise normal tremolo...

and maybe add an envelope later too...anyone done it, got a schemo/link if they have... ...nice dual lfo circuit?..

ok, it had nothing to do with sandra, but @#$% it , oh hang on sandra's coming back around again........................beep........................................beep................................................beep.....................................

[tubegeek]

I think she's stalking you....

[drolo]

Funnily I started watching this movie last week my wife and gave up 5 minutes into the movie. It just felt too fake. Then we watched Duncan Jones' Moon instead, which blew my mind.

[Mark Hammer]

The "phasefilter" mod to OTA-based phasers, when used without any dry signal mixed in, yields an interesting amalgam of bubbly auto-wah, vibrato, and a tremolo-like effect stemming from the reduction in perceived volume coming from the reduction in treble as the filter sweeps lower.

Never heard anyone sweep the first 2 (allpass) sections and second 2 (lowpass) sections separately. 

Alternatively, lets just take a pair 0f 13600/13700 chips, use 3 sections (plus an op-amp based fixed allpass stage à la Causality) for a phaser/phasefilter, and save the 4th OTA stage for a VCA to do the tremolo thing.

[deadastronaut]

Alternatively, lets just take a pair 0f 13600/13700 chips, use 3 sections (plus an op-amp based fixed allpass stage à la Causality) for a phaser/phasefilter, and save the 4th OTA stage for a VCA to do the tremolo thing.

cheers mark, sounds cool to me... if i catch your drift properly..

i'll breadboard up the casuality 4 phaser, and we'll go from that standpoint..

i may need your help with the VCA though..


i like the idea of a phaser with a choppy trem shfting 2 in 1 thing.....cool.

[deadastronaut]

hmmm i breadboard the casuality 4, seems more wah than phaser to my ears....and the demo's ive heard sound like wah too really...

certainly not as phasey as a phaze 45 that i modded to be more chewy...

i might bread up my modded phase 45 , then add another lfo in there..

[Mark Hammer]

You do know how to get the lowpass function out of the OTA-based allpass stages, right?  The cap that would normally go from pins 10/12 or 5/7 to the input, now goes to ground from 10/12 or 5/7.

It is a judgment call regarding what the value of those caps should be.  Some may find the stock values used for phasing entirely appropriate for the lowpass function, while others may prefer slightly smaller or larger values, depending on where they like the sweep.

Charlie Barth has some nice demonstrations of the effect at his moosapotamus site: http://www.moosapotamus.net/frankenstone.html

I'll just note that it may be best to listen to only one channel since, some of the samples are I stereo and you get clean in one ear and wet in the other. The phasefilter sound can be heard most effectively by leaving out the clean signal.

[deadastronaut]

too late mark, i pulled it off the breadboard...

i'm going with a phaze45 on breadboard...then i'l have a go at adding another choppy lfo..

[Jdansti]

Oh no... Here we go again!  You're gonna make me want to build another really cool pedal you've designed, aren't you?

[Mark Hammer]

And given recent events, you just KNOW it will be death-defying.

[Jdansti]