Will have to listen later.
Carrier bleed to a certain extent is known issue. Specially with passive.
Been awhile, far as I remember it wont be completely cancelled
since the circuit isn't completely balanced.
If bleed is excessive can be DC offset or excessive DC
Can use a highpass or cap on oscillator output to block DC
Or since you have 2 signals or A and B input could be DC from
voice input. Or overall problem with dual rail opamps and oscillator
using half the rail.
Carrier bleed to a certain extent is known issue. Specially with passive.
Been awhile, far as I remember it wont be completely cancelled
since the circuit isn't completely balanced.
If bleed is excessive can be DC offset or excessive DC
Can use a highpass or cap on oscillator output to block DC
Or since you have 2 signals or A and B input could be DC from
voice input. Or overall problem with dual rail opamps and oscillator
using half the rail.
Last edited:
I've made another video to illustrate the problem better, including scoping the output of the preamp when the output is oscillating, if that sheds any light on the problem.
You can parallel gates of a 40106 to get more oomph.
Fun fact: I just built a ring modulator with an LM1496 driven by a sine wave. Actually two driven in quadrature. This to create a device called Audiakaleidoscope (sic) after its inventor W. Jak (Audiak). I wrote some stuff about that on sister forum MFB Freaks (in Dutch).
Fun fact: I just built a ring modulator with an LM1496 driven by a sine wave. Actually two driven in quadrature. This to create a device called Audiakaleidoscope (sic) after its inventor W. Jak (Audiak). I wrote some stuff about that on sister forum MFB Freaks (in Dutch).
I see another problem: The 555 output is positive only, not AC, so only half the ring modulator is ever used. A DC blocking cap on the 555 output should fix that.
Hi,
I thought I'd post an update on this. Adding the 220uF decoupling next to the CD40106 solved the oscillation problem and dramatically reduced the carrier bleed.
I've now had PCBs made and 3D printed an enclosure. Initially, it wasn't working and the CD40106 was going up in smoke. It turned out to be the fault of the HG Semi ICs that had been fitted. Replacing with a TI part fixed the problem and now everything is functioning correctly. The carrier bleed is inaudible and the circuit is quiet. The only noise comes from the rustling of the microphone.
Thanks for all the help!
James
I thought I'd post an update on this. Adding the 220uF decoupling next to the CD40106 solved the oscillation problem and dramatically reduced the carrier bleed.
I've now had PCBs made and 3D printed an enclosure. Initially, it wasn't working and the CD40106 was going up in smoke. It turned out to be the fault of the HG Semi ICs that had been fitted. Replacing with a TI part fixed the problem and now everything is functioning correctly. The carrier bleed is inaudible and the circuit is quiet. The only noise comes from the rustling of the microphone.
Thanks for all the help!
James