I have been trying to build the basic version of this circuit for a couple of weeks now but I can’t seem to get any sound of it. I am using a 3.5mm cable and converting it to a 6.35mm jack to plug it into my guitar amp. Virtually no sound comes out except for some occasional scratchy noise when I turn the potentiometer.
My power supply is fine, I know I have the right wall wart and have checked the output using a multimeter. All resistor values are roughly correct according to the multimeter.
The output on the voltmeter when I connect the multimeter to the tip and either the ring or sleeve of the audio cable jack ranges from ~1.06v to ~1.22v (respectively the minimum and maximum values of the pot).
The main two theories I have as to what is causing the problem is either 1) the grounding is incorrect and/or 2) the stereo jacks I am using are wired incorrectly.
The main thing to note is that the panel I am using (contrary to Sam’s original metal design), is a 3D printed plastic that doesn’t conduct electricity; therefore, everything had to be grounded manually. I have checked continuity with the grounding, everything seems to be connected fine at least.
I am not using the CEM3340, but instead the AS3340, which is an identical clone - I have checked with multiple ICs, they don’t seem to be the issue. I have also checked the power supply for both ICs on the board, both are receiving the correct voltage (+12v, -12v).
All resistor values have been checked and seem to be in order.
Am I missing something completely obvious? Thanks in advance.
Here are some photos of my current wiring for troubleshooting (cable is plugged into TRI OUT):
Component placement and values seem ok though I cannot determine the yellow stripe on the 1.5 meg. Can you provide a view of the track cuts on the back?
I don’t think that this is a panel grounding issue. Many of us use non conductive materials for the panels, and they work fine, as long as the jacks are properly grounded. And yours seem to be. I would suggest tracing the circuit to identify a misplaced component.
Unfortunately your vendor doesn’t supply a datasheet to show which terminal is which. Based on the datasheet for a similar jack sold by Tayda it seems likely that in this image
the terminals from left to right are tip, ring, and sleeve. You can ignore ring since this isn’t a stereo circuit. Ground connects to sleeve. It looks to me like that’s how you’ve wired yours but it’s hard to be sure. Anyway as @Bpbby says your best bet is to verify this using a multimeter. Stick a patch cable into a jack and see which terminal on the jack has continuity with tip and sleeve on the other end of the cable.
And I agree with @K.ostas: Jack wiring probably isn’t your problem. Can’t hurt to check but it’s more likely some error in the circuit assembly — or possibly just that your control voltage is out of range, as discussed in the 3340 troubleshooting and annotated stripboard links above.
Have you done it on breadboard? I can see how that would seem silly, but it would enable you to switch out any component with ease, and if you have a reliable breadboard it could facilitate the elimination of several possible faulty components if there happen to be any at all. Especially with a good quality breadboard…
Very sorry, I meant to provide an image of the back of the stripboard but forgot. Resistor value according to multimeter for the 1.5M reads as 1.57M, so I don’t think there are any issues there.
I have checked replacements for both the 3340 and op amp. However, I have only replaced the op amp with a TL082 rather than the original TL072 as I didn’t have a second of the latter. This yielded a loud buzzing sound when plugged into the guitar amp (not an oscillation, but the sound that comes out when you touch the tip of a plugged in audio cable).
No, I haven’t tried it on breadboard, but unfortunately I don’t think I have spares for some of the soldered components (but I will have a look). Some of the components may be faulty, however all resistor and pot values seem to be correct. The only ones I can’t verify are the capacitors, so I think all components seem to be in order.
Wait… just as I was taking the photo I discovered a lack of connection to the ground in the middle on the far right. Warming up soldering iron now - I’ll provide an update if it works.
I would replace everything! Lol. That’s what I do anyway. I built the same circuit. Same layout on strip board and same 3340. You can make this thing work, somehow. I’d aquire spares for the whole thing and breadboard for sure.
Will do! I can always use those components later for a second oscillator anyways!
I may have just discovered an issue. The voltage from the course tune pot output and ground ranges from 0 to 12 volts as expected. However, after the 100k resistor that connects to the input of the 3340 the voltage ranges from ~ -1.3v to ~6.5 v as I turn the pot. I should be reading only positive voltage here correct? Or at least certainly not one that ranges from a negative to positive value.
Is this what you meant @analogoutput when you said the control voltage input is out of range?
The two dots in the image below represent where I am putting the two terminals of my multimeter. The red dots yield values ranging from ~ -1.3v to ~6.5v and the blue dots yield the expected range from 0v to 12v. Maybe there’s an issue with the 100k resistor? Though the multimeter is reading the correct resistance…
Just replaced the 100k resistor and actually got a sound to come out! It’s very faint and relatively high pitched - turning the pot barely changes the pitch at all, to a degree I would expect the trimpot to change the pitch.
I think that the problem might lie within the 3340 itself (even though I have tried multiple chips). The TRI OUT voltage (between pin 10 and circuit ground) always hangs around -1.22v and barely changes when I turn the pot (which reflects the sound that I heard). This is of course inverted to 1.22v by the op-amp, however I can’t pin point why there is barely any change in voltage when I turn the pot.
Any chance that pot could be malfunctioning? I’ve had the issue before…not with this circuit but plenty of other occasions, a sh** pot was to blame for failure.
