X0XB0X clicling noise problem

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x0xb0xer
 
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Joined: Sun Oct 17, 2010 2:20 pm

X0XB0X clicling noise problem

Post by x0xb0xer »

i get some clicking noise in my x0xb0x. i changed the vca and the problem was not solved. the clicking noise comes randomly so i don't think it is an vca issue. i also try BCbox's VCA "Click be Gone" Mod but it does not solves the problem.


http://www.file-upload.net/download-289 ... m.mp3.html

can anyone help me!

Luap
 
Posts: 363
Joined: Wed Jul 08, 2009 7:10 pm

Re: X0XB0X clicling noise problem

Post by Luap »

If you tried the BC click be gone mod, then I assume you already had a good read through that big thread?
( http://forums.adafruit.com/viewtopic.php?f=13&t=16764 ) It discusses more than just the VCA click.
Yours actually doesn't sound that bad!? I've heard much worse.. I think even some real 303's click more than that..
But as you probably gathered, there are 1 or 2 unknown causes of this click, besides the VCA. It appears Altitude may have a fix though, and i'll try it myself this week. I'd suggest keeping an eye on that thread :wink:

x0xb0xer
 
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Re: X0XB0X clicling noise problem

Post by x0xb0xer »

Thanks for helping me. I tried about 5 VCA's (BA6110) and the Problem is still there. The Mainproblem is, that this Clicking Noise in my X0xb0x comes randomly. The usual VCA Clicking noise comes at the beginning of a note. It Sounds like a kind of LFO controlled clicking in a random way. Sorry for my bad english, its hard to describe. Im sure there is a simple solution for this Problem. Adding Lowpassfilter mods change the Sound to much away from a TB-303. This is a poor kind of Solution :-(
Last edited by x0xb0xer on Mon Oct 18, 2010 6:20 am, edited 1 time in total.

x0xb0xer
 
Posts: 3
Joined: Sun Oct 17, 2010 2:20 pm

Re: X0XB0X clicling noise problem

Post by x0xb0xer »

Today i search for a solution again and tested some mods. Now im pretty sure the Problem comes from Q1-Q4! Some People solved the clicking noise Problem by chnaging the BA6110 to a BA662. With a BA662 there is no need for Q1-Q4.

I tried to solder a 1K Resistor from Collector of Q1 to a 0,22uF Cap. The other end of the cap is connected to GND. The clicking Noise is gone! Im pretty sure this mod is needless if Q1-Q4 are matched ore selected in any kind (high beta? low beta? same beta?)

Can anyone tell me the effect of selecting Q1-Q4?

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altitude
 
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Re: X0XB0X clicling noise problem

Post by altitude »

You know, the current mirror is something I would like to look at in depth. It is supporting circuitry for the BA6110 and I am wondering if using the old PNP and NPN parts there makes any sense since they vary wildly in specs/ hFe etc. Looking at other modern transistors I have on hand, they are much tighter spec'd than the vintage parts (especially the 733). Hopefully someone a little more knowledgeable about this can shed some light..

guest
 
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Re: X0XB0X clicling noise problem

Post by guest »

putting a 1k and 220nF cap
at the collector of q1
will have almost the identical effect
of putting a 100nF cap after the 2.2k resistor of r133
it slows down the attack a bit

matched betas are important in q1 through q4
but as long as they arent off too much
you wont notice
the human ear isnt all that sensitive to volume
like it is to minor frequency discrepencies
but new parts would definitely be better here

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altitude
 
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Re: X0XB0X clicling noise problem

Post by altitude »

Have some BC640 and BC639 parts on the way to try out (same pinout and I have seen them used for 733/945 alternates)

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