Hello everyone! I don’t know if this is the right place to ask these questions🤷♀️.
I am making a small speaker for the LMNC modules. I found this schematic on the music from outer space site:
I builded it on a breadboard and plugged the LMNC VCO in. It is making a sound but when I turn the ‘tune’ knob on the vco the sound doesn’t change.
I can however change the sound by touching some components or just moving my hand around the vco or breadboard (like a theremin).
What could be the reason that I cannot change the sound by using the tune knob?
Hmm, I take it you get the same behaviour irrespective of which input on the mixer you use?
There could be various reasons for it not to work, but the first could be that the tune knob is not connected correctly. Have you ever hear it work properly?
Yes, i listend to it through an old pair of headphones. But the opamp got warm by doing this. That is why I am building this speaker/amp.
(The tl072 doesn’t get hot anymore when I use this circuit so that is something good :).)
Adding another module shouldn’t affect the coarse tuning, so odds are something else is broken. The VCO frequency is controlled by the sum of two (or more) voltages. If you have a multimeter, you can measure the voltages in circuit, see the annotations here:
Measure between 0V/GND and the 100k resistors (the points marked CV and TUNE CV). The voltage on the TUNE CV should change if you tweak the tuning knob, and the sum should be well over 5 V for things to be audible (see the chart further down). If this isn’t the case, check the wiring.
Well I only used one jack and pot just to test the circuit. Because I thaught if you only want to use one input the circuit should work aswell. Perhaps this is the problem?
I tested it again. They both work now but i didn’t change anything.
I do remember that I heated up the lm386 when I tested it for the first time because I plugged the 9 volts by accident to the wrong pin of the ic. Perhaps this has something to do with it?
Oke, then, for the stake of getting some reliable statistics, please repeat that (changing nothing) and see whether there is some consistency in the circuit’s behaviour
