BCbox's VCA "Click be Gone" Mod

[guest]

antto
the first pulse is the reset pulse for the envelope generator
the second pulse is the gate signal
a cap at the r131/r133 juncture will slow this down
and either removing d35
or putting another diode in reverse to it
will allow this capacitor to discharge
when the gate is off

altitude
how does it sound now
can you try placing a 10k resistor
from the d35/r133 juncture to ground

[Altitude]

The harsh click is replaced by the "regular" click (similar to Paul's tests). Same randomish increase and decrease in click intensity while seq is running. I can mask it like Paul did by various cap values but it does mess up the env and is a marginal improvement in the click. My bad mod actually sounded better and did not have the same effect on the envelope if that has any relevance. What does shorting the two diodes actually do? The demo I posted is with those two shorted together and the 150nF cap and as flawed as it is, it does work to take the click out completely so something there did make a difference..

I'll be going back and re running all the tests you recommended in the previous pages as well as the 10K you just mentioned in a little bit..

[guest]

do you have the vca offset trimmer installed

[Altitude]

do you have the vca offset trimmer installed

Yes.

[guest]

can you get a scope capture
of the output of the vca
with the x0x at the highest note possible
no resonance or envelope mod
and cutoff at maximum
just the first 10ms is best

[Altitude]

Which pin should I probe for the output of the VCA?

I did some initial tests:

10K resistor between gnd and R131: Lowered volume, no change in click
150 nF between GND and R131 with extra diode in opposite direction on D35: Improved click removal, will solder for more testing
1M+10K at pin 3 of VCA: No effect

Some other observations: With waveform switch in middle, clicks are obvious, with cap installed almost inaudible and with cap + extra diode, return considerably

Also, with heavy filtering, I can hear the clicks much better and there is definitely a fixed period to them

[guest]

pin8 of the vca

is the click still periodic
when the waveform switch is in the middle position

its interesting that the reverse diode makes it worse
with the switch in middle position
but makes it better under regular conditions

[Altitude]

sorry if I am a bit of a scope newb here, but what do I reference probing pin 8 to? If I reference to gnd, I cannot zoom in on the waveform since it is offset

to clarify, when I added the diode in, it made it worse with the waveform switch in the middle only compared to the cap by itself. Overall, it seemed to return the env to normal behavior while removing most of the clicking.

[guest]

you can try referencing to 5.333v
or scope at the volume pot if that doesnt work
referencing to ground

so cap+diode is worse than cap
with waveform switch in middle
but cap+diode is better than cap
with regular setup

[Altitude]

ok,
Here is the waveform with everything down, cutoff all the way up



Here is the output with everything all the way down, note the spike. These vary in intensity also.. could this be it?




I'll look at the extra diode in and out of the mix here in a minute

[guest]

is that with a capacitor in place

the first waveform has a bit of a spike as well
those are showing up in the envelope also

is the second waveform during a note on
or is it always oscillating at that low level

[Altitude]

No cap in place on either. The second one is of the actual wave playing. I do not see the spike in the env at all.

This reverse diode to discharge the cap thing is looking really promising and very well may warrant some recording. There is still a click there it but sounds more like the free running osc rather than the pulsing click without the cap. The range of values I can use for the cap is also broad. 100n, 150n, 220n all work the same to my ears and only when I am at 680n do I really hear a difference. The only effect I see on the env is a rounding off of the leading and top edges, no change in the decay.

[Altitude]

Ok, decided it worth recording some real world tests.

http://midiot.net/x0xclick.wav

This is a 0.15 uF electrolytic cap between ground and the junction of R131 and R133 and a 1N4148 diode reversed on D35. The clip starts out with the mod off, then on at around 6 secs, and then I take the diode out at ~12s and from then on the cap is switched in and out.

[guest]

i hear the clicks getting reduced
but i cant hear much difference with the diode changed

it seems like the clicks come in bursts
at a rate slightly faster than the notes being played
but that could be the oscillator slightly out of sync with the gate

[Altitude]

i hear the clicks getting reduced
but i cant hear much difference with the diode changed

it seems like the clicks come in bursts
at a rate slightly faster than the notes being played
but that could be the oscillator slightly out of sync with the gate

The diode change is 12-13 seconds. It is subtle at all the settings at min but gets considerably more pronounced when you start using it since it has a big effect on the env (confirmed on scope). It is a lot easier to hear wearing cans. I dont doubt that this may be a sync issue with the gate and osc since it does scale with tempo.