Re: 2VCO Problems

by guest on Wed Apr 04, 2012 4:53 am

basically you unsolder the middle pin of q1
and then solder a 220k resistor
from that pin to the pad it used to go to
this inserts a 220k resistor in line with it
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Re: 2VCO Problems

by izze on Wed Apr 04, 2012 6:00 pm

Hello guest..

well i tried it.. the only thing it did, is that i now have a cutted leg on my Q1.. the click is the same.. didnt help any :( it seems that the 220k just lowers the overall volume so that the clicks seem less loud, like everything else.


1.) My x0x would be perfect without the click, well i think i will have to order the other stuff then. (trimmer, resistor, and cap)
Or is there another way ? I read somewhere that resoldering the VCA might help ? i am not confident that this would help because i used very good solder and soldered every pin with fresh cleaned iron and new solder.

2.) Also, does it help to tune the best possible if i change TM4/TM5 to precision trimmer pots ?

3.) I tweaked TM3 today, i am not quite sure which setting i like the most, i turned it a little clockwise from the middle position and left it that way. what setting is recommended, or is it just tuned by ear ?

Thanks again
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Re: 2VCO Problems

by guest on Wed Apr 04, 2012 8:51 pm

before tyring out the pot trimmer method
try soldering a cap at that same q1 middle leg position
the cap should go from the leg to ground
so you dont need to cut the leg again

better trimmers for the vco probably dont matter too much
its really the matching of dac resistors that give good pitch

tm3 is mostly to taste
but the tb303 manual gives a calibration point for it
if you want to set it like that
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Re: 2VCO Problems

by izze on Wed Apr 04, 2012 9:00 pm

Ok so i just solder a cap to the middle pin (which is connected, not cut?).
What capacity should the cap be ? i only have 10uF caps i guess.

Thanks for your time and effort
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Re: 2VCO Problems

by guest on Wed Apr 04, 2012 10:05 pm

i would try 10nF or so
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Re: 2VCO Problems

by izze on Thu Apr 05, 2012 7:10 am

I tried that, it doesnt work, i cant make out any difference.

I hope that the trimmer option will work.. i remember that at my first x0xb0x it got better with the trimmer, but nowhere silent :?
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Re: 2VCO Problems

by Altitude on Thu Apr 05, 2012 10:19 am

try the cap and the reverse diode like outlined in the click thread, that will do it for sure (too much maybe). I use a 150 nF which is way too much on its own but with the reversed diode, it works out very well
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Re: 2VCO Problems

by izze on Thu Apr 05, 2012 11:18 am

ok will try that tomorrow.. i only have a 10 nF in that range.. well.. we will see what happens
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Re: 2VCO Problems

by izze on Thu Apr 05, 2012 11:25 pm

Hey ya.
The click is not really gone, but i cant really hear it when the OSCs are running, there is some other noise, but well i dont care, thats as near as you can get to the original. A little noise is normal :)

Thanks to all for helping.. my x0x got its place in my homestudio now :D

Image


yay !!!!!! :D
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Re: 2VCO Problems

by guest on Fri Apr 06, 2012 1:34 am

awesome job
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Re: 2VCO Problems

by izze on Fri Apr 06, 2012 10:01 am

Thanks guest :)

I got another quick question, do you think if i buy a BA662A, i will get rid of the click ? Every single BA662A i heard sounds better to my ears. I plan on buying one, the are expensive, but well if it helps i am gonna pay :mrgreen:

Here is a quick recording you can still hear the clicks, but well now that the 2VCO is tuned it sounds better than the first recording for sure:

http://k003.kiwi6.com/hotlink/38us95657x/x0xtest.mp3
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Re: 2VCO Problems

by Altitude on Fri Apr 06, 2012 10:55 am

Some 303s have the click as well, ba662 most likely won't make any difference. I a/b them years ago when I built my first one and there was no difference in the click
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Re: 2VCO Problems

by izze on Fri Apr 06, 2012 11:06 am

I guess you are right, but well, i heard x0xes with the BA662 with absolutely no click, and they sounded so nice. They seem to sound more than the real deal to me. But this could just be me. Or maybe it was other parts that they used ?
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Re: 2VCO Problems

by Altitude on Fri Apr 06, 2012 11:34 am

there is no such thing as and x0x or 303 with absolutely no click, there is always a click as a result of the free running VCO (its the one that seems to have a pattern if you are listening closely to it). There is also the one which is a result of the DC offset of the opamp which can be trimmed out with the 10M resistor and trimmer. The third is the weird one that seems to be more prevalent, but not exclusive to the x0x. This is the one that you can mitigate with the extra caps in the VCA section.

Out of the 26 that I have built all using the same spec parts (as far as resistors and caps go), all have different severity of the vca click so I deal with it on an individual basis. There really is no silver bullet
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Re: 2VCO Problems

by izze on Fri Apr 06, 2012 10:37 pm

Ok i understand. But besides the click, does the BA662 offer the more TB-303 like sound ? I think so...
You have built alot of machines, could you tell me if an "upgrade" can be heard ?

Thanks for the time
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