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 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
Simple 2 Chip Drum Machine
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Cynosure
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PostPosted: Wed Dec 07, 2016 7:22 am    Post subject: Reply with quote  Mark this post and the followings unread

Grumble wrote:
Could you maybe use this: http://www.onsemi.com/pub_link/Collateral/MC74VHC1G14-D.PDF

Yes, that should work. However, it looks like it is only in an SMD package. Also, it has a lower max voltage, so you need to be aware of that when designing your circuit.

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Cynosure
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PostPosted: Mon Jan 09, 2017 5:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

Someone made this into a PCB and has cases for it too. I feel like a grandfather Very Happy

More info: https://www.muffwiggler.com/forum/topic-174599.html

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Blue Hell
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PostPosted: Mon Jan 09, 2017 5:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

Cool
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gasboss775



Joined: Jan 02, 2016
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PostPosted: Thu Jan 11, 2018 1:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

I really like the bass drum sound but still a bit unclear on its mechanics. 3.8H is a big inductor!
I'm thinking that the 3.8H inductor and 82n capacitor form a series tuned circuit, which in conjunction with the 4069 wired as an inverting amplifier, you get a tuned band pass filter with a centre frequency of:

Fc = 1/(2*pi*sqrt (L*C))

Fc = 1/(2×3.14×sqrt (3.8 × 82 × 10^(-9)))

Fc = 285 Hz approx which seems a wee bit high for a bass drum but the inductor probably has a huge tolerance so the figure could be at either side of this.

Now, I have a 500mH inductor which I believe are still made as spares for wah wah pedals.

Now to get the same Fo = 285 Hz, we need to rearrange the formula;

C = 1/ (2*pi*Fo)^2×L

C = 623.7 n , so probably use a 680n, though might be better with an even bigger cap for lower Fo, will try a 680n then maybe a 1u cap instead.
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IGR



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PostPosted: Fri Jan 12, 2018 4:47 am    Post subject: Reply with quote  Mark this post and the followings unread

You are near right, but.. Original LC has damping factor approx. 0.00734 and bandwith of 4,2 Hz. Yours will have damping factor 0.05 /bw 31,83 Hz. It will not so readilly oscillate as you need.
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IGR



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PostPosted: Fri Jan 12, 2018 5:03 am    Post subject: Reply with quote  Mark this post and the followings unread

I just thought try small power transformer primary, this should be about 5H.
Check Roland TR 77 schematic too, there is 16H inductance in BD tank, of course LC circuit in parallel. Good luck.
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gasboss775



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PostPosted: Fri Jan 12, 2018 5:51 am    Post subject: Reply with quote  Mark this post and the followings unread

IGR I did wonder about this, though I was thinking in terms of Q ( resonance ) only because I am more familiar with that concept.

The mains transformer primary might be worth a try, thanks for the suggestion.
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IGR



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PostPosted: Fri Jan 12, 2018 6:10 am    Post subject: Reply with quote  Mark this post and the followings unread

I just breadborded this circuit- primary 3W mains transformer in parallel with 1uF cap, excited by piezo pickup. I got simple passive stompbox, much better then all those cigarbox with piezo. It must be followed by high impedance preamp, otherwise nice boom disappears.
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gasboss775



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PostPosted: Fri Jan 12, 2018 10:54 am    Post subject: Reply with quote  Mark this post and the followings unread

I'm going to experiment with this over the weekend, I like the idea of using inductors in music circuits, they are quite unique and quirky.

Craig Anderton made a passive filter using one half of a transformer a bank of capacitors selected by a rotary switch and a pot to vary the resonance.

The CR78 drum machine had a few inductor based percussion voices and I think a lot of these early beat boxes used LC circuits in their percussion voices.
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IGR



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PostPosted: Fri Jan 12, 2018 11:09 am    Post subject: Reply with quote  Mark this post and the followings unread

I agree, inductors are piece of magic, partly unpredictable, hard exactly reproductible due core alchemy.
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Cynosure
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PostPosted: Sat Jan 20, 2018 9:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

I am glad to see that people are still playing with this idea.

I used those huge conductors only because I had them. I had just taken apart an old EQ that was filled with them. They are big things about 1" in diameter.

You should be able to replace the LC parts with RC instead and get the same sound.

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