Basic Oscillator help?

OK so I’ve followed the LMNC tutorial for the basic Oscillator, using a transistor that oscillates at 9V (S9018) and it appears to be working, the led does the flickery thing and changes rate with the variable resistor, so it appears to work, but no sound comes out of the 8ohm speaker. Any ideas? Do I need to amplify it somehow? Please help

Can you post some pictures of your build?

It’s not made clear in the tutorial but you can’t just attach an 8Ω speaker. You need a powered speaker or an amplifier.


Right, no worries. I was a bit wary of plugging it into a powered speaker incase I blew the whole thing up haha! So if I wire the outputs into like a pocket guitar amp that’d work? Also, probably a dumb question, but am I OK to have the neg wire of the output soldered to the earth point of the 9V on the stripboard?


Would it be detrimental to hot glue the pot to the stripboard once I’ve completed each one? I’ve got 5 made so far, and things are getting a bit messy haha


Hot glue is ok but can fail attaching to the back of pots. You could drill a hole in the board and mount the pot thataway.


I give you, THE OCTODRON (should be an umlaut over the third O but idk how to do it)


These Ö codes might help: ASCII und HTML Codes für Umlaute und ß – Deutsch 101-326

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You are a legend! So now I present: THE OCTODRÖN!

Ön my Lïnux Mínt bøx I lîkě to üse thè Maç kéyböård lã¥oút.

How’d you make the panel?

And I see a picture of an output jack… but I don’t see an output jack… ?

I’m gifted enough to work in a high school that has a laser cutter, and I’ve enough of a brass neck to claim any wee gadgets I make as “Continued Professional Development” haha!

Ah yeah, that was before I’d soldered everything together. It is now alive, and has a nice wee set of wooden shoulders. Just need to finalise the 9v dc socket and the 1/4" Jack socket and I’ll be good to go, but as it stands I’ve already been sitting making squealy noises with it



Ok, so as it stands this thing needs to be plugged into an amp to make noise. Is there any way I can build a wee amp to go inside it so it’s an amplified output? I’m just thinking so I can plug it then into my Monotron rather than daisy-chaining Octo->amp->monotron->monotron output/headphones

I’m honestly not sure what voltage levels this oscillator makes but I think it’s really more a case of needing to buffer the output rather than to amplify it. That is, the signal size is large enough if the impedance you’re trying to drive is large enough (as opposed to 8Ω). In fact it’s possible it’s a little too hot for the Monotron, but if so a voltage divider (two resistors) can take care of that.

The output also has a DC offset but the Monotron input is AC coupled so that shouldn’t be a problem either. So I’d guess the oscillator could just go directly, or via a voltage divider, into the Monotron.

But a buffered output might be a better idea, just to make sure the oscillator and the Monotron don’t get into any fights. The Kassutronics avalanche oscillator I linked to regarding CV input also handles output.

(Q2, Q3, R3, R4, and C2.) The transistors do the actual buffering and C2, R4 remove the DC offset.

My oscillator runs off a 9V Centre Negative PSU, and when I tried running it directly into the Monotron I wasn’t getting any sound. I may have buggered something up, so I’m going to give it a going over tonight to see if I can make any sense of it, or see anything obvious I’ve done wrong

Oh, right, power supply. That Kassutronics circuit uses ±12 V. But I think you can use +9 V instead of +12 V and ground instead of -12 V and it’ll still work, provided the oscillator amplitude isn’t a lot larger than I think it is. You might need to drop R3 down to about 1k to avoid clipping, depending on the amplitude.

More investigation is definitely required haha. Thanks so much for being patient with me and putting up with my incessant questions

For 9v circuits look to the guitar pedal world - if fidelity isn’t a concern the ‘ruby amp’ or the ‘noisy cricket’ would work, but you would need to attenuate the signal going in to them I imagine. A simple voltage divider or a volume pot would be enough…

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