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

by rv0 on Fri Jul 10, 2015 8:43 am

@faybiens
The original 303 clicks too.. if you removed the click completely, it will sound less 303-ish

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

by faybiens on Fri Jul 10, 2015 9:15 am

I know that click can be discussed but reading this post I understood that silent 303 and even xox does exist and clicking annoys me.
Any analog synth I had which I can hear trigger sound makes me become crazy :-) It spoils the pure analog sound beauty and it is so easy to install "cleaning" capacitors

My xox was clicking too much to my taste especially in the high frequencies, for sure the digital click due to trigger has to be cancelled.
For me the click is a "bug", it is the trigger that is audible and the oscillator non reset that is audible which somewhere is responsible of the envelopp being audible.
The last point can be discussed but increasing the attack just enought to bring the env in the non audible domain does not affect the attack and punch of the sound, just takes off a high frequency marker at begining of nearly each notes.

And I compared to a real 303 with very little clicks, the sound remains unchanged just click free and that is very enjoyable (always my taste) when played dry or in a delay/verb with headphones just for the pleasure.
It is something to apreciate the first ms of the xox sound and to apreciate the evolution of the parameters with no click hidding these first ms.

The mods I have found do not affect the envelopps and the mods can be adjusted to reduce the click and to the point to cancel the click.
A 10uF and a 20k resistance will maintain the same click than the 303 that I used for comparaison.

After that a switch can be used to go back to initial components, I have to say that clicks can be usefull to create a marker when mix becomes populated.
But now I have the choice.
Last edited by faybiens on Fri Jul 10, 2015 9:28 am, edited 1 time in total.

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

by altitude on Fri Jul 10, 2015 9:20 am

faybiens, thanks for your input. I agree, there is normal clicking you hear in the 303 and there is the sharp slapping click of the x0xb0x. Some are better, some are worse, I have a bad one. I switched my BA6110 to a BA662 clone so all my old fixes are out the window and I'm rebuilding mine shortly so will give your mods a try. If you dont mind, could you post a schematic or diagram of your changes?

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

by faybiens on Fri Jul 10, 2015 9:42 am

I will share, with pleasure. I have an explanation of why the tb303 click is less sharp than the xox, it is due to C72 capacitor being old and seing its value increased in time. I changed a lot of capacitors in old gears and noticed their value can increase more than two times for some. So that is a bit what I am doing on Q36 env generator. I did compared a 303 and my non mod xox and noticed that the release at note off is a bit longer on the tb303. These observations brought me to that conclusion. After the trig is a xox bug, on the 303 it is very discrete and without high frequencies
Last edited by faybiens on Fri Jul 10, 2015 11:02 am, edited 1 time in total.

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

by faybiens on Fri Jul 10, 2015 10:12 am

These are the mods I did:
Attachments
Xox no click mod.jpg
no click
Xox no click mod.jpg (261.01 KiB) Viewed 1135 times

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

by faybiens on Fri Jul 10, 2015 10:17 am

And that is the result:
https://soundcloud.com/jamsh-1/no-clicks-xox

Nothing compared to the sharp click I had before, and I made the effort to keep the same initial release which was not the case of the R133 trick
And the R133 trick was keeping a medium/bass part of the click

Tell me your impressions when testing
Last edited by faybiens on Fri Jul 10, 2015 11:03 am, edited 1 time in total.

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

by faybiens on Fri Jul 10, 2015 10:59 am

Just to confim that the xox with 945, 733AP, a BA662 and the C29 reserved sounds exacly the same as a tb303
Reversed capacitor behaves differently that is an evidence mainly like if higher value and maybe different resistance

I have no doubt, even the accent interaction on next following notes is there, the resonnance sounds exactly the same
And I can tell you that I am a picky guy

if I can give an advice install 945 in the resonnance and the square shapper, the square which is quite delicate by the way it is produced needs a high beta transistor
I got a nearly 50/50 cycle, I heard some with 40/60 even less which gets into pulse waveform domain if even heard 30/70 which is really bad, some people do even install 733K at this place to be sure the beta will be high.
The square is so good that it has not to be missed!

Even the sequencer which has to be programmed a bit differently produces the same sequences

Very impressed, very good job and knowing that you can easily put your hands in ...

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

by antto on Sat Jul 11, 2015 6:16 am

faybiens wrote:if I can give an advice install 945 in the resonnance and the square shapper, the square which is quite delicate by the way it is produced needs a high beta transistor

the transistor in the square waveshaper (Q8) is 733, which is PNP.. 945 is NPN, isn't it?
i don't think the beta of Q8 really changes things much..
i've tried quite a bunch of different transistors in place of Q8, with all kinds of hFE values.. the sound was still the same:
viewtopic.php?f=12&p=114271

faybiens wrote:I got a nearly 50/50 cycle, I heard some with 40/60 even less which gets into pulse waveform domain if even heard 30/70 which is really bad, some people do even install 733K at this place to be sure the beta will be high.
The square is so good that it has not to be missed!

the 303/x0x "square" is not a square
your square is also 30/70 on some lower freq
the thing is.. the square shaper creates a "square" with frequency-dependant pulse width, frequency-dependant middle edge softness and "knee", and frequency-dependant amplitude
in short: the square has a frequency-dependant shape

at low freqs the PW is 30/70 .. (it's even less on even lower freqs)
then at some mid freq it's 50/50
and at higher freqs it goes in the other direction
this is the most audible aspect of the 303 square

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

by faybiens on Sat Jul 11, 2015 6:38 am

It is a square, produced in a different way than a minimoog, this square has harmonic dephasing due to filter chain, but still a square

I meant 733ap for the square, as I was specifying a 733k later. Sorry for that.

I did a comparaison at 100hz, I am 50/50 while another xox with 733p was at 60/40, definitly beta should distord harder that saw wich goes through a high pass to get rid of DC.
Then it is totally normal that at lower frequencies, the square is no more close to 50/50 as the saw is getting less and less symetric.

But the square tone feeling is more pronouced at medium and high frequencies, at these frequencies you can tell if the square is good, like I said if at these frequencies the square sounds pulsy, you missed it. That is the purpose of my advice.

How many demos of xox I heard with 'bad' square...

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

by faybiens on Sat Jul 11, 2015 7:19 am

I will check the behaviour of cycle at higher frequencies, as I don't get how it can go the other way, interesting

I will measure the cycles, but if I remember well even at low freq I still close visually to 50/50, will check and measure the deviation freq vs cycle, and compare to my friends 303

I will check as well if the upstream circuit prior to the transistor ( high pass if I remember) does not have a higher influence on the cycle

this square is so important to sound correct, after that you guys are perhaps used to correctly get it, but I heard so many bad demos....
Maybe not enough documented, selection has very certainly to be done at that point, knowing that same model of transistor can have big beta differences

So my asumption was to put the higest selected beta 733ap there, should try the lowest 733p to experiment, and will check upstream circuitery influence

And thanks for your input!

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

by faybiens on Mon Aug 10, 2015 10:27 am

Here is my definitive mod, using a 0.47uF chemical on the BA662

Concerning the square cycle, I am 60/40 at the lowest note (30hz), 50/50 on the main range of notes and drifts to 30/70 to the higest note of the added octave.
I have my assumption on why it drifts on the higest notes, but do not want to spend time on it as for me the most important is to get the 50/50 cycle on the same range of notes of the TB303 I could try.

I am doing a second xox with the same components I used for my first one, I will see if I get the same cycle on the same range of notes.
Attachments
Xoxmod no click.png
Xoxmod no click.png (497.04 KiB) Viewed 705 times

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

by altitude on Mon Aug 10, 2015 11:04 am

I just installed these mods on a new one I am building for myself this weekend and they sound pretty good! I am using my modded version of the OML BA622 clone and I cant hear any of the harsh click that I had with my other box. I have a 100n on the BA662 right now but will try the electrolytic cap tomorrow..

Thanks for the input!

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

by faybiens on Mon Aug 10, 2015 3:44 pm

The good thing with that is that the release env time is maintained, the short staccato style notes are preserved.
Longer release changes a lot the initial TB groove

I was still hearing some tiny clicks with the two ceramics, I ended to put the closest chemical I had in hands to the sum of the two ceramics (0.47) and install it at the summing node of std vca env and accent vca env.
My xox is totally free of any clicks now, and I do really enjoy playing bass in my tape delay/echo with pure sound, click on LP bass in a delay is not good for me, especially when the sound is solo.

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

by altitude on Mon Aug 10, 2015 3:50 pm

Try one of these next time. Way less than a BA662A

https://oshpark.com/projects/QCnNP4oK

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

by faybiens on Mon Aug 10, 2015 4:04 pm

I bought one from synth cube, they propose another clone without the trim pot.
But i did not found the original BA662 was finally so expensive, I bought severals at 40/50$

I did try all I had and I never noticed any changes in the click, not even lower or higher hearable clicking

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Please be positive and constructive with your questions and comments.