HexInverter
New Member
Hello all!
I am playing around with oscillators and filters/weird audio circuits. To give you a bit of background, I am using a CD4093 Quad NAND gate to generate 3 square waves at out of phase frequencies, and mixing them together with equal resistors. These are being listened to through a small amplifier and speaker. I have attached a simple passive filter to my chain based on this design:
**broken link removed**
I have replaced R with a potentiometer, to be able to sweep the frequency. Now, my issue is that I can sweep the frequency upwards quickly, but then when returning it back down, it cuts out at various points and all audio stops. I understand that volume can change with the frequency, but this is volume completely dropping out - and once the knob is set in place it will regain itself. If I sweep it down slowly it tends to work. When the audio cuts out, my amplifier power LED dims/brightens oddly. I suspect it has something to with a signal issue, but couldn't be sure! What am I doing wrong here?
I know that passive filter design is considered inferior to active filters, but due to space limitations and the parts I have on hand right now, I can't really make an active filter. Can anyone shed some light on what's happening here? I've tried keeping a resistor load on the pot between poles to stop it from reaching zero resistance to no real help, and I've also tried dropping the level going into the filter from the oscillators via a resistor to ground.
Any help would be much appreciated!
I am playing around with oscillators and filters/weird audio circuits. To give you a bit of background, I am using a CD4093 Quad NAND gate to generate 3 square waves at out of phase frequencies, and mixing them together with equal resistors. These are being listened to through a small amplifier and speaker. I have attached a simple passive filter to my chain based on this design:
**broken link removed**
I have replaced R with a potentiometer, to be able to sweep the frequency. Now, my issue is that I can sweep the frequency upwards quickly, but then when returning it back down, it cuts out at various points and all audio stops. I understand that volume can change with the frequency, but this is volume completely dropping out - and once the knob is set in place it will regain itself. If I sweep it down slowly it tends to work. When the audio cuts out, my amplifier power LED dims/brightens oddly. I suspect it has something to with a signal issue, but couldn't be sure! What am I doing wrong here?
I know that passive filter design is considered inferior to active filters, but due to space limitations and the parts I have on hand right now, I can't really make an active filter. Can anyone shed some light on what's happening here? I've tried keeping a resistor load on the pot between poles to stop it from reaching zero resistance to no real help, and I've also tried dropping the level going into the filter from the oscillators via a resistor to ground.
Any help would be much appreciated!
