I’ve built 5 super simple oscillators using SS9018 transistors and varying capacitor values between 10-100uf. I have a bench supply so I can give them whatever voltage I need, and I can confirm that the LEDs start to flicker at ~8v. Turning the potentiometer also changes the rate of this flicker. This leads me to assume that the oscillators are, well, oscillating. However, I cannot get audio out of them at all. I’ve tried wiring them (individually as well as in parallel) to a mono mic jack, as well as a .5w project speaker I have laying around. Neither one results in ANY audio whatsoever. These are so simple that I’m a bit at a loss as to what could be to blame. Any ideas are welcome.
one thing that has me puzzled is that the schematic shows the capacitor’s negative lead terminates on the positive side of my LED, but the stripboard layout shows the capacitor’s negative lead terminating on the negative side of the LED. Right now i’ve got it wired per the stripboard layout (with the capacitor’s negative lead on the negative side of the led), could the layout be incorrect and that be the cause of my issues?
Yes, I’ve read through all of these threads. Doing so is what got me as far as I’ve gotten.
I think I’ve narrowed things down a bit. Firstly I believe I had a grounding issue on my jack, which I’ve resolved. This got me far enough that I could then get each oscillator to output audio individually. However when I connect all of their outputs to the jack at the same time - silence.
Ahaha, he surely did not.
From the video it hard to see but he may have used high impedance resistors on the output.
Like this
When connected all together, the voltage from one will affect the other and could break the avalanche… should simple enough to simulate on a piece of free software.
If you look at the diagram, there are 100k resistors on the outputs yes. Not sure what the difference is between the video and mine. Would diodes on the output prevent that “circulation” or am I off base?
True yes there are 100K, the webpage was not loading here.
A diode would decrease the voltage quite a bit and not sure it would help at all.
Did you also look at this :
I built the “super simple mixer” and took each of the oscillators’ 100k resistor outputs directly into the “inputs” of the mixer circuit (no pots, just directly soldered in). I am still getting absolutely no audio even though I can see the oscillators working when I power them up.
I have the power input/distribution on the big board as well as the mixer. You can see the red/black wires supplying power to each oscillator. When I give it power the oscillators light up and the VRs do affect the rate that the LEDs flash. The blue wires going into the mixer circuit are the outputs from each oscillator post-100k resistor.
I JUST noticed the broken trace on the backside of my amp board. I’m repairing that as we speak and will re-test. No idea why that is like that, must have been left over from … god knows what.
When things are going nowhere, i usually start with systematic tests. I would test each oscillator individually first, they are getting the volatges, they all make a sound. Then, the mixer, you could test it with voltages (it will work for mixing DC voltages as well), after that I would test one oscillator at a time in each individual mixer input, making sure they all work, etc… hopefully, you will find where the issues is/are.
I did some more testing and was able to make a little progress, however things are still not great.
Some additonal background:
I built 5 oscillators which are identical, using the SS9018 transistor. Each has a different capacitor value. 10, 22, 33, 47, and 100
If I ONLY connect the oscillator using the 100uf cap, I get LED flicker and audio using my amplifier circuit.
If I ONLY connect an oscillator using any lower value cap, I get LED flickering, but no audio.
If I connect the 100uf oscillator/cap to ANY mixer channel, I get audio.
If I connect ANY other oscillator to ANY other mixer channel alongside the 100uf oscillator, I get no audio at all. Even just one additional oscillator kills my audio regardless of which channel I connect it to.
So, I feel confident that each channel of my mixer circuit is working. I’m also confident that my oscillator using the 100uf cap is fine. I see no difference at all in how the other 4 oscillators are constructed and they ALL give me LED feedback when I turn their pot.
I’m going to test using 2n3904 transistors next since that was the original design and I’m always going to be on 12v.
I’m not sure what issue could explain the symptoms I’m seeing though. Even if the 4 lower-cap-value oscillators weren’t oscillating, I wouldn’t really expect them to kill the input of the oscillator that I know IS working.
Another note: if you look at the photos I attached previously, you’ll see that the traces UNDER my IC were not cut. I thankfully fixed that issue before proceeding with these tests.
When you say “flickering”, you mean you visually see periodic changes in the brightness of the LED?
That would imply the oscillation period is fairly low. If it were say 200 Hz I wouldn’t expect you could see that, it would just look like a steady light I think.
And I assume you’re varying the potentiometer that is supposed to control the frequency.
Can you estimate the pitch or oscillation frequency range you get (from low to high pot setting) with the 100 µF cap?
If you’re actually seeing the LED pulsing with any cap, but getting audio only with the 100 µF — that’s really bizarre. The LED is telling you there is an oscillating voltage at the output, that should give audio when sent to the speaker. I’d think the only way you’d not hear anything is if the frequency is above or below the audio range… but 100 µF should give a fairly low frequency, well below the upper end of the range, and smaller cap value should give a higher frequency. 47 µF should give you about an octave higher. It doesn’t make sense that it would be too high a frequency to hear. And in any case, way way way before it was too high a frequency to hear, you would not be able to see flickering on the LED.
So something is very very strange here. Either that or I’m misunderstanding you, or you’re misinterpreting some behavior.
This sounds to me like there are DC levels (and there should be) which add up to more than the op amp output can get to.
If that is happening, then turning down the mixer pot for the non 100 µF oscillator would reduce the summed voltage and you should start to hear the 100 µF oscillator again.
I’d try using a multimeter to see what voltages are present on the oscillator outputs. If it’s oscillating you might see the multimeter moving around between values or it might just show the DC level it’s oscillating around. If it’s not oscillating but just putting out a DC level the multimeter will show that.
There will be a DC offset on the oscillators’ outputs, and if those offsets add up to something over 12 V you won’t get anything but a DC 12 V out of the mixer. Really to mix these oscillators you should use a mixer with AC coupled inputs, which just means adding a capacitor between each input and its resistor. If the mixer input resistors are 100k then a reasonable cap value to use would be something like 100 nF to 1 µF. That will remove any DC levels and leave only the oscillating part of each signal (or zero, if it’s not oscillating at all) and summing those won’t push the op amp to its output limit.
the 100uf cap oscillator is definitely the slowest “flicker” and it’s the only one that I can hear (and obviously it’s very "clicky). Honestly I’m not happy with how slow it is, but that’s another issue for another time.
For of the others, the “flicker” (probably not the best term to use) is less perceptible, but you can see a difference (mostly it manifests as slight changes in brightness) in the period when you turn the potentiometer on all of them. On the 10uf, you can barely tell at all.
Even if this were a matter of being outside of audible ranges, I don’t know how attaching a 2nd oscillator could result in the first one becoming inaudible. It’s really FN bizarre.
