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BCbox's VCA "Click be Gone" Mod
Moderators: altitude, adafruit_support_bill, adafruit, hamburgers, phono

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

by crustypaul on Wed Aug 18, 2010 12:58 pm

I did have a 68nF in there but it didn't quite feel like enough as a bit to much of the top end click was still getting through, so i added another 18nF one in parallel as that was what i had handy. I guess every x0xb0x would be slightly different so trying out values between 47nF and 100nF to see what works best would probably be the best bet.
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Re: BCbox's VCA "Click be Gone" Mod

by guest on Wed Aug 18, 2010 3:46 pm

this click problem is very strange
im not convinced its a resistor tolerance stackup
although it might be possible its a capacitor tolerance issue
most capacitors are +/- 20%

its clear its not coming from the accent volume section
and im getting the feeling its not coming from the envelope generator
as changing out all the transistors in that section had no effect

so this leaves two other areas to check out
the vca
the mixer

does the click happen on mixout as well as headphone

the vca is more likely of the two
it would be interesting to take the ba6110
out of a nonclicking x0x
and place it into a clicking x0x
and see what happens

another way to get more attack time
is to increase c42
this changes the decay time
but not the release time
isak recently put this mod in
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Re: BCbox's VCA "Click be Gone" Mod

by bcbox on Wed Aug 18, 2010 3:58 pm

so this leaves two other areas to check out
the vca
the mixer
an easy way to verify if it's the mixer or VCA is to turn down the volume control. If you still hear it it's the mixer since it's after the volume control.
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Re: BCbox's VCA "Click be Gone" Mod

by crustypaul on Wed Aug 18, 2010 5:29 pm

It must be before the volume control as the level drops with the normal sound when you turn down the main volume. The click also comes through the headphones on mine.

I've swapped out all the transistors in both the envelope and the VCA in an effort to track this down, along with trying aout 30 different BA6110's from 4 different batches. None of it has any effect on the clicking. Its entirely possible that every BA6110 i have is dodgy though.

I'll have a go at swapping some caps out when i get a chance.
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Re: BCbox's VCA "Click be Gone" Mod

by guest on Wed Aug 18, 2010 7:22 pm

the volume knob controls the volume
for both the mixer and the headphone

do you have a good x0x you could try the ba6110s on
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Re: BCbox's VCA "Click be Gone" Mod

by crustypaul on Thu Aug 19, 2010 12:42 pm

I just changed all the capacitors in the VCA and the envelope and theres still no change to the click. i get the impression i could rebuild the entire thing with brand new parts and it'd still be exactly the same. :?

I also just tested the headphone output again and the clicking is a lot worse through there that through the mix out. In fact the 86nF to ground mod that i put in has virtually no effect on the clicking from the headphone socket.

I don't have a silent x0xb0x i could test the BA6110's on but i do have and adafruit one that clicks a bit less, and theres no change in that one if i stick in any of the BA6110's i have.
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Re: BCbox's VCA "Click be Gone" Mod

by rv0 on Thu Aug 19, 2010 1:56 pm

Keep in mind real 303's click too..

so don't go insane with it!

Here's some "real" 303 tests, left and right are different 303's, one clicks, one doesnt. txt for info+pattern
http://users.telenet.be/darffader/rv0test/sqrclick1.wav
http://users.telenet.be/darffader/rv0test/sqrclick1.txt

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

by guest on Thu Aug 19, 2010 2:26 pm

if the clicking is worse through the headphones
its possible its coming from the headphone amp
although im not sure exactly how that would happen

did you listen on headphones
or plug the headphone out into your mixing board
and then listen through the same speakers
you listened to the mixout on
as it would be good to keep the testing conditions the same
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Re: BCbox's VCA "Click be Gone" Mod

by crustypaul on Thu Aug 19, 2010 7:02 pm

darffader wrote:Keep in mind real 303's click too..


True, but i've built an x0xb0x that doesn't click in the past so now i'm on a mission to find out why :wink:

guest wrote:did you listen on headphones
or plug the headphone out into your mixing board
and then listen through the same speakers
you listened to the mixout on
as it would be good to keep the testing conditions the same


Both through a mixer channel but I think it might have just been that the signal is slightly louder through the headphone output, either that or i'm starting to imagine things.

Its not the headphone amp causing this. I've isolated it from the circuit by pulling out J5 and lifting R159 and theres no difference. The click is definately getting in before the mixer as i tapped the signal on the positive side of C38 / pin 8 of the BA6110, and the click is still there. Its also after the filter as if i listen to the signal on C21, just after the filter theres a very slight click on the note, but no more than i would expect on any analogue synth, and it disappears if i turn up the decay.

I'd say it must be something in the VCA, but seeing as i've changed every component in both the VCA and the envelope section apart from the diodes and the resistors, that doesn't leave very much to try. :?
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Re: BCbox's VCA "Click be Gone" Mod

by guest on Thu Aug 19, 2010 7:59 pm

is there the same slight click sound out of the vcf
on the nonclicking x0x

it could be some pickup in the vcf section

another thing to do is to compare betas
between all transistors in the envelope section
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Re: BCbox's VCA "Click be Gone" Mod

by Luap on Thu Aug 19, 2010 9:14 pm

Crusty, after hearing your demo's, your click is worse and more consistent than I have here. Either way, the cause is likely similar I expect.
I was just listening to my other x0x, and actually, it does click, but only very slightly. You have to listen carefully to notice it, so it's not a problem.

The clicky x0x is in pieces right now while I change the led spacers (tedious!) so i've not done any work on it for the clicking problem. Im still reading this with great interest though..
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Re: BCbox's VCA "Click be Gone" Mod

by crustypaul on Fri Aug 20, 2010 7:14 am

after listening to what other people describe as clicks it does seem like mine is more of a popping thump than a click. Most peoples click seem to be top end ticks which would be taken care of by the mod i've got in, but mine seems to have a lot of bottom end thump on it as well. It sounds more like the kind of thump you get through speakers when you switch something on! :(

guest wrote:is there the same slight click sound out of the vcf
on the nonclicking x0x


I don't have a nonclicking one, but the adafruit one i have that clicks a lot less has more or less the same response at C21 as the clicking one.

guest wrote:another thing to do is to compare betas
between all transistors in the envelope section


Can that be done with the transistors in place? I'm not sure i have the patience with this to remove them all again.
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Re: BCbox's VCA "Click be Gone" Mod

by guest on Fri Aug 20, 2010 2:04 pm

you cant measure beta in place
so its probably not worth it
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Re: BCbox's VCA "Click be Gone" Mod

by izze on Sat Sep 11, 2010 3:06 pm

Thanks for discovering this Mod.. works perfect.. no more clicks.. makes the x0xb0x a charm to work and record with 8) Thumbs up!!
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Re: BCbox's VCA "Click be Gone" Mod

by altitude on Sat Sep 11, 2010 3:33 pm

not me, thank BCbox.. I just adapted it to the stock x0x

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Please be positive and constructive with your questions and comments.