Silence oscillation

[squarewhite]

Hi

I've built from nicolas collins book a diy vactrol panner. I'm using the 40106 as the panner. There are different caps which creates different speed. I've hook up the panner as in the book. My problem is that there is always a sound coming from the panner, 40106 oscillating. How can i silence this oscillation? It's annoying when i send a sound into it and there is this constant sound. Any advice on this?

[Psyingo]

have you added any decoupling caps? 100nF on the +v pin of the chip to gnd, as close as possible, with as short of leads as possible. and a big cap, say 100uF or more from + to gnd.

also how close is the vactrol to the 40106? is it on a breadboard? if its close, try moving it further away?

and then after that, is there any DC offset present in the signal you are panning? even if the signal is silent there could still be, say, 0.5v or something of offset, and with that your oscillator may leak through because it is turning on and off that offset to impose itself... try putting a 1uF cap before the vactrol if there isnt one already.

[squarewhite]

thanks for the tip. No I didn't add any decoupling caps. I'll do the modification once I get back home.

no I've already build in on the pcb. you can see it in the pic, left corner. The vactrols are left and right of the 40106. (on the left side of the pic)

how do I check for DC offset? I don't have a oscilloscope. Do you mean putting a 1uF cap before signal in and vactrol? I'm using 1 mono input to the vactrols; input-vactrol1-vactrol2.

[Psyingo]

What picture are you referring to? I dont see a picture posted here

[squarewhite]

oops.. here you go.

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