OTA problems. No signal after pin 5

Started by ohmelter, February 06, 2010, 02:11:38 PM

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01370022

#20
Man you're keen  ;D Still once you got it working, its one more for the tales of awesomeness.

Did you check if the oscillator is working correctly? I'm fairly sure the voltage reading that you got on Pin1/pin16 is too low. If you've got an audio probe or got access to an o'scope then put that on either pin1 or pin16 (they should be the same trace) or on the other side of the 10k resistor supplying them. You should hear(see) a low pitch hum(low frequency whacked up sine wave) that moves in pitch(frequency) when you turn the rate knob. Your meter may have some issues reading it if it's set to DC, cos the signal is an AC wave.

If you're getting 0V on that pin then it could be that the oscillator stage isn't functioning and (I'm fairly sure) that it needs some voltage on that pin to pass the signal (I want to check voltages on that pin to make sure), since that's how a phaser works, by varying the volume of the wet signal in relation to the dry signal. I can't remember the specifics of it exactly but Uncle Google should know if your interested. Just ignore the stuff about why moving multiple comb filters creates a phasing sound and find out how they go about creating the moving multiple comb filters.

And I'm gonna look like a right twat if I've got my phaser and flanger theory mixed up   :D

Edit: sp
Looks like we're gonna need a bigger amp.

Just to "get to pitch" you need a trimmer. That's why guitars have knobs, and why xylophone makers have power grinders. - PRR