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BCbox's VCA "Click be Gone" Mod
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Re: BCbox's VCA "Click be Gone" Mod

by antto on Sun Oct 24, 2010 2:52 am

okay..
in my synth - there is no audiable clicking
and i have a 132Hz LP filter filtering the "GATE"
and the "GATE" is just a sharp step signal (that's why i suggested if it's possible to make the expo-like x^2 build-up instant)

now, a LP filter of about 120-140Hz would be good
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Re: BCbox's VCA "Click be Gone" Mod

by antto on Sun Oct 24, 2010 3:08 am

"the click is periodic" :shock:
noooooo!
the click is there, every time
it's just that you don't hear it on every note
since the oscillator is free running, when some notes begin - the waveform is near 0.0 (thus upening the VCA fast won't make an audiable click)
but when the waveform is away from zero - opening the VCA fast will make a sharp transition from 0 to wherever the waveform is at, and thus an audiable click
the shape of this transition is the shape of the image i was talking about, that looks like x^2

btw, what is the resistance in that spot where you're trying to put a cap?
i wanna calculate the frequency there..
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Re: BCbox's VCA "Click be Gone" Mod

by antto on Sun Oct 24, 2010 3:41 am

i recorded my synth with 3 different settings for the LP filter (sample)
1) the filter is set to ~14kHz (virtually disabled)
2) 72Hz (no clicks, but it's too slow)
3) 144Hz (no clicks, good)

as you can see, in the first part it's clicking like a b*banned, and it sounds like periodic but it's not, as i already said, the click is always there, it's just not audiable on every note..
i can record more samples with other filter settings if you want..
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Re: BCbox's VCA "Click be Gone" Mod

by guest on Sun Oct 24, 2010 5:07 am

its right after r133 so 2.2k
that should give 500Hz or so with the 150nF
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Re: BCbox's VCA "Click be Gone" Mod

by guest on Sun Oct 24, 2010 5:19 am

this has been a good thread
i never quite understood
why c42 didnt control the attack time
but its because the reset pulse comes before the gate

its looking like c72 actually controls the attack time
which is probably better
since it gives that x^2 increase antto mentions
whereas a normal capacitor discharge is an inverse exponential
so it gets loud really quickly
and then slowly tapers off

altitude
you might want to try clipping in a 10uF or 22uF
in parallel with c72 and see how it sounds
but im pretty sure the release will effected
along with the delay till the note comes on
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Re: BCbox's VCA "Click be Gone" Mod

by antto on Sun Oct 24, 2010 6:14 am

so with 2.2k resistance, my calculator says 0.47uF for ~153Hz which is fast but it's close to 144 which doesn't click
a capacitor between 0.47 and 0.5uF should work
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Re: BCbox's VCA "Click be Gone" Mod

by altitude on Sun Oct 24, 2010 6:36 am

antto: do you have the extra diode in with your test? That is vital.. That will discharge the cap so you will get the filer without any major effect on the env

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Re: BCbox's VCA "Click be Gone" Mod

by antto on Sun Oct 24, 2010 8:10 am

uhm.. there is no diode.. "my synth" is a software synth, not the x0xb0x..
this filter is "reset" to 0 when gate goes off
so it only affects the attack of the gate (which is instant, so the LP smoothens it up)
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Re: BCbox's VCA "Click be Gone" Mod

by Luap on Sun Oct 24, 2010 11:22 am

antto wrote:uhm.. there is no diode.. "my synth" is a software synth, not the x0xb0x..


Wait, software synth?? :? You were not talking about a software synth all this time, were you?
You have a x0xb0x, or no? Does it click?
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Re: BCbox's VCA "Click be Gone" Mod

by antto on Sun Oct 24, 2010 11:37 am

Luap wrote:
antto wrote:uhm.. there is no diode.. "my synth" is a software synth, not the x0xb0x..


Wait, software synth?? :? You were not talking about a software synth all this time, were you?
You have a x0xb0x, or no? Does it click?

yes, i have a x0xb0x and it clicks just like all the others
but the audio recording i posted is from "my synth" which is a software synth.. :roll:
We are here too: irc.freenode.net >>> #x0xb0x
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VCO Tuning: http://forums.adafruit.com/viewtopic.php?f=12&t=24759 (do it the EASY way)

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Re: BCbox's VCA "Click be Gone" Mod

by Luap on Sun Oct 24, 2010 4:05 pm

antto wrote:
Luap wrote:
antto wrote:uhm.. there is no diode.. "my synth" is a software synth, not the x0xb0x..


Wait, software synth?? :? You were not talking about a software synth all this time, were you?
You have a x0xb0x, or no? Does it click?

yes, i have a x0xb0x and it clicks just like all the others
but the audio recording i posted is from "my synth" which is a software synth.. :roll:


Ok...
However, anyone that has built more than one of these things will tell you that they don't all click.
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Re: BCbox's VCA "Click be Gone" Mod

by antto on Mon Oct 25, 2010 2:11 am

i meant that my x0x clicks in the same way as the other clicking x0xb0xes..
btw
anyone with a non-clicking x0x should come and post scope pictures from the GATE..

guest: could it be the difference in the types of capacitors around that part of the circuit?
maybe it was meant to be fixed with capacitors but if we are using different types.. i don't know..
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Re: BCbox's VCA "Click be Gone" Mod

by guest on Mon Oct 25, 2010 4:17 am

there seems to be two different clicks
one is due to offset in the vca
which varies between x0xen
and the other is due to the short attack time
which i think is pretty consistent between x0xen

its been a while since i played with my 303
but i seem to recall it having the same sharp attack
and similar click

when i get my audio gear out of storage
ill throw it on a scope and see whats up
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Re: BCbox's VCA "Click be Gone" Mod

by antto on Mon Oct 25, 2010 4:25 am

offset in the VCA..
yeah, i understand, but it won't sound like clicking if the attack isn't so sharp

EDIT: here: (sample)
i added offset into the input of the VCA, it's like:
vca_out = (VCF_out+offset) * LPF(amp_env * GATE)
the offset itself is pretty much half of the volume of the filtered output (so it's quite loud)
it's audiable (sounds like an annoying pressure) but it dousn't sound like sharp clicking
...this is with the filter set to 144Hz
We are here too: irc.freenode.net >>> #x0xb0x
..:: c0nb0x v1.00 ::.. http://forums.adafruit.com/viewtopic.php?f=7&t=29282 (new control app - win/osx)
VCO Tuning: http://forums.adafruit.com/viewtopic.php?f=12&t=24759 (do it the EASY way)

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Re: BCbox's VCA "Click be Gone" Mod

by altitude on Mon Oct 25, 2010 2:09 pm

Something that just occurred to me, is the reset pulse supposed to overlap the env pulse? Cause it does..

Image
Last edited by altitude on Mon Oct 25, 2010 3:42 pm, edited 1 time in total.

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