5 Note Lunetta

[garcho]

Howdy y'all, I've been noodling on the breadboard and drew this up so I thought I'd post here. It's a very slightly sexed-up Schmitt trigger. 5 keys, 5 knobs, 5 switches. In the process of building one, have a PCB in the tank now. Lots of fun sounds, will post some samples soon, along with some pics and PCB stuff. All suggestions welcome!

[PHOBoS]

thanks for posting, looks interesting
I'm currently doing some vactrolled oscillator stuff myself, and I can get very nice sounds out of it, so would love to
hear some sound samples from this design.

one thing that doesn't seem right to me is how you connected U1D, U1E, U1F. assuming these are just spares and
not meant to heat your tea/coffee/soup or whatever you want to keep warm, I would only connect the inputs
to GND not the outputs

or just make more oscillators out of them = more fun

[garcho]

[analog_backlash]

Hi,

An intriguing circuit - I've just been thinking about how it all works. I nearly sent you a very stupid reply, but then I realised that I was mis-reading the circuit diagram (when your interconnecting lines cross, they are connections, I think). That's where the little blobs come in handy.

I'm looking at the capacitor values attached to your keyboard. Is there any clever plan to this, i.e. are the keys in any kind of musical interval apart? Probably, a silly question for a Lunetta thread... Also, where did you geta 1u33 capacitor (or is it a 1uF in parallel with a 330nF)? I've never seen one with that value before.

Look forward to hearing the results,

Gary

[garcho]

[analog_backlash]

Ah! I thought that it might be a pentatonic scale ( the word Pentasonic in your title is a bit of a clue...). That also explains the strange capacitor value. I think that putting the 2 caps in parallel is a perfectly valid way of achieving this.

Thanks for the clairifications,

Gary

[mosc]

Cool circuit. Thanks for posting.

Just a suggestion. Don't ground unused outputs in CMOS chips, unless you know that the output will be LOW because of the way you have tied the inputs. This will be an unnecessary current suck.

[garcho]

Thanks for the tips and kind words! Any advice for how I should deal with the unused inputs in this instance?

[trav]

tie unused inputs to ground, leave unused outputs hanging

[garcho]

Oh, that's what I thought. Messed up the schemo then misread Mosc's post. Gotta slow down!

[mosc]

Yes, Trav got it right.

[didactic and not necessarily directed at garcho]

CMOS is said to use virtually no current, which is almost true. It uses current only during the transitions from high to low or vice-verse. This is because CMOS inputs have almost infinite input resistance and very small input capacitance. For practical purposes, the only current CMOS uses to to pump up or pull down the capacitance of the gate inputs. Once these capacitances are charged up or pulled down, no more current is used. But when an output is tied to the state opposite to the logic of the inputs, you get a switch which will draw the max possible current constantly. The amount of this current is limited by the dimensions and materials of the internal transistors.

Lunetta circuits, which run at very slow audio and sub-audio rates, use very little current. Crank the clocks up a few hundred times and those chips would get too hot to touch and would eventually burn up if there are enough gates that are switching in the chip. This probably won't happen in a hex-inverter though. Still saving power one place give more to use elsewhere.

At one time I used to design CMOS DSP chips.

[/didactic]

[garcho]

Thanks! Makes a lot of sense.

[garcho]