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 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
A few Lunetta circuits I've been messing around with
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gasboss775



Joined: Jan 02, 2016
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PostPosted: Tue Dec 12, 2017 5:39 pm    Post subject: A few Lunetta circuits I've been messing around with Reply with quote  Mark this post and the followings unread

This one can be made from 1/4 of a 4093 or 74hc132. It is an oscillator or a nand gate depending on the switch position.


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gasboss775



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PostPosted: Tue Dec 12, 2017 5:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

Another Schmitt gate based oscillator, this one with a sync input as well as the gate input. The value of C1 depends on that of C2, will need to experiment more to see what is best as I don't know how to calculate it on paper. Q1 can be a bs170 or a 2n7000.


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gasboss775



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PostPosted: Fri Dec 15, 2017 6:39 am    Post subject: Reply with quote  Mark this post and the followings unread

I have found the following oscillator with sync to work better than the one with the mosfet.

Note that with these simple circuits if the syncing oscillator runs at a higher frequency than the main oscillator that the oscillator will stall as the capacitor can't recharge quickly enough to sustain oscillation.


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gasboss775



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PostPosted: Fri Dec 15, 2017 8:10 am    Post subject: Reply with quote  Mark this post and the followings unread

The next Schmitt oscillator isn't really a VCO as such however it does permit a degree of modulation of both frequency and pulse width which is very much dependent on the setting of the main tuning control VR2 as well as that of the actual modulation depth control VR1.

With VR1 fully clockwise and VR2 at maximum resistance it is possible to get around an entire octave of frequency modulation, however with VR2 at minimum resistance the maximum frequency modulation is equivalent to about a major 3RD going by ear.
The CV input was at VDD which in the experiment was equal to 10.04 Volts.

The relationship is frequency to CV is neither linear or 1V per octave but given its simplicity and that this is the Lunetta forum I think that is OK! Smile


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gasboss775



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PostPosted: Sat Dec 16, 2017 11:23 am    Post subject: Reply with quote  Mark this post and the followings unread

This one is a square noise generator, basically it outputs random 1s & 0s. This can be fed into shift registers to produce random gates or random voltages ( using a DAC such as an R2R network )

The low pass output is just more slowly changing, effectively it gives an alternative random output.


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gasboss775



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PostPosted: Sun Dec 17, 2017 2:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

This is a 3 bit DAC, has only been tried on the simulator but should work. With a hex inverter and a dual opamp you could make a Dual 3 bit DAC module, or with 2 hex inverters and a quad opamp you could make 4 3 bit DAC's.

The output is 0 to +10V, the inverters should be powered with a regulated +5 volt supply. The opamp (s) the usual +/- 12 or +/- 15 V supplies.


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gasboss775



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PostPosted: Sun Dec 17, 2017 3:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

A very simple VCO using a Schmitt trigger oscillator controlled by a Vactrol. Note this VCO isn't linear OR 1V per octave! Is very simple though, good for Lunettas!


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PHOBoS



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PostPosted: Mon Dec 18, 2017 11:49 am    Post subject: Reply with quote  Mark this post and the followings unread

nice little circuits Very Happy

I like how you used the same resistors in the DAC to get different values. You can leave out the 2.2M though,
the tolerance of the 4k7 is much higher than what it changes in total value. Also instead of using the 3.33V reference
for the non-inverting input of the opamp I think you can just attach it to GND and add an offset voltage to the inverting
input.

And yes, vactrols work great for those oscillators, the slight slew is actually great for percussive sounds.

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gasboss775



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PostPosted: Thu Dec 21, 2017 1:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

PHOBoS wrote:
nice little circuits Very Happy

I like how you used the same resistors in the DAC to get different values.


Is good for 3~4 bits, though in this case I had an abundance of 8K2 resistors!

Quote:
You can leave out the 2.2M though,
the tolerance of the 4k7 is much higher than what it changes in total value.


I was thinking that too tbh, even with 1% resistors the tolerance error is greater!

Quote:
instead of using the 3.33V reference for the non-inverting input of the opamp I think you can just attach it to GND and add an offset voltage to the inverting input.


I'm still scratching my head with that one, did you mean with the opamp powered from +/- 12 V power supplies rather than single rail? I would prefer single rail options in the context of Lunetta circuits.

Quote:
And yes, vactrols work great for those oscillators, the slight slew is actually great for percussive sounds.


I made a bass drum circuit last year using a vactrol to tune a twin tee circuit using a decaying envelope signal. I posted it on muff wiggler.
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PHOBoS



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PostPosted: Fri Dec 22, 2017 9:58 am    Post subject: Reply with quote  Mark this post and the followings unread

You mentioned "The opamp (s) the usual +/- 12 or +/- 15 V supplies." but you're correct that it wouldn't work with a single supply.
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