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 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
The Bandersnatch
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PHOBoS



Joined: Jan 14, 2010
Posts: 1807
Location: Moon Base
Audio files: 351

PostPosted: Mon Nov 12, 2012 4:07 pm    Post subject: The Bandersnatch
Subject description: a frumious lunetta soundmachine
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This project started out with a simplified version of the jabberwock.


My idea was to make a solar powered/controlled version, with just 4 oscillators to control the data and clk inputs.
So I added some LDR's in series with the potmeters, which was nice, but the real fun and I mean REAL FUN Shocked Laughing
happened when I turned them into vactrols. I used my Mad Monkey Sequencer + Divider to control them
and with those I was to able to create some really nice electrobeats and basslines. (and jabbering aswell)

The same weekend I did the experiments there was an AcidTrasH performance planned which I was going to take
part in. So I decided to turn the circuit into something I could use for that, and thus the Bandersnatch was
born. Or at least the frumious oscillators Wink

I didn't have a lot of time to build it, so I searched for a piece of scrap wood that was big enough, drilled
some holes for pots jacks and switches and gave it a quick paintjob. During the performance the actual circuit
was still breadboarded, but at least I didn't have to use screwdrivers and trimpots.

I had thought about just making a simple box for it, but I could use some more control circuits (which are also
really usefull to control my ADRIAN8 drums) so I decided to turn it into a standalone system. I had some ideas
but no final plans on how it would turn out, I just started building,.. Cool

The recording below is from the breadboarded version (controlled by Mad Monkey Sequencer + Divider).
There are some effects added, but no extra sounds. The filtering you hear is not an added effect. Cool



more info will follow


Bandersnatch - front.jpg
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The bandersnatch
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Bandersnatch - front.jpg



Bandersnatch - back.jpg
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frumious circuitry
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Bandersnatch - back.jpg



PHOBoS - Bandersnatch Demo's - Vactrol Fun.mp3
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breaboarded bandersnatch sounds.

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 Filename:  PHOBoS - Bandersnatch Demo's - Vactrol Fun.mp3
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Last edited by PHOBoS on Mon Nov 12, 2012 4:51 pm; edited 2 times in total
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PHOBoS



Joined: Jan 14, 2010
Posts: 1807
Location: Moon Base
Audio files: 351

PostPosted: Mon Nov 12, 2012 4:16 pm    Post subject: Frumious Oscillators
Subject description: Bandersnatch info
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first, the part that started it all, which I named the frumious oscillators. I began with just 4 NAND oscillators attached
to the CLK and Data inputs of the 2 shiftregisters (CD4015). I also added some resistors to the outputs that were unused in
the jabberwock (12, 3) but connected them to the opposite channels (L/R) for some extra stereo effect. There's also a switch
connected to the RST input which, when closed, cuts out 1 (U2a) or 2 (U2b) stages of the shiftregister and changes the
waveform. creating a sharper higher pitched sound. I should record a small demo,. or test it yourself Wink
(for more info I suggest reading the CMOS Waveshaper thread)

As I mentioned the next thing I added were the LDR's, for this I used a configuration that I had used before in circuit bend
devices, namely putting the LDR parallel with the pot. This makes it possible to have manual speed control, but at a
certain point the oscillator won't just go slower, instead the LDR starts taking over. (no effect when it's in darkness).
you could put a switch in series with the LDR, so that you can turn it off completely.
note: I put the LDR parallel to the pot + series resistor, because even in full light the resistance is high enough not to stall
the oscillator.


For a wider range I added a switch with 2 extra caps. The switch has a center position which provides 3 different
ranges. (1nf, 1nf + 10nf, 1nf + 100nF)

of course I didn't just use LDR's but turned them into vactrols. I used a simple transistor driver similar to what's used in
the wogglebug. I didn't put the extra control pots in initially which is why there are only 4 pots on the panel (the sloped
one on the right side) instead of 8. But after having build some more circuits for it, I decided that it would be very usefull
so I made an extra panel. (the horizontal panel in front of it)

I also swapped the pots, so I now have the CV control pots on the sloped panel and the speed pots on the other one
(made more sense to me that way). because I had some extra room on this panel I also added output jacks for each
oscillator and an attenuated diode mixed output.


PHOBoS - Bandersnatch - Frumious Oscillators.gif
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PHOBoS - Bandersnatch - Frumious Oscillators.gif



_________________
"My perf, it's full of holes!"
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Last edited by PHOBoS on Tue Nov 13, 2012 3:02 pm; edited 2 times in total
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PHOBoS



Joined: Jan 14, 2010
Posts: 1807
Location: Moon Base
Audio files: 351

PostPosted: Mon Nov 12, 2012 4:16 pm    Post subject: Dual Binary Counter + RND generator
Subject description: Bandersnatch info
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Because I had such nice results with using the Mad Monkey Sequencer + Divider to control it, I wanted to make some similar
circuitry. The first thing I made was a binary counter/divider, I didn't choose a CD4040 this time but a CD4520, which is a
dual 4 bit counter. But you can link them to get one 8 bit counter so I added a switch for that option. It might look a bit
weird to see the CLK pin itself connected to GND but I think the following information from the datasheet will clear that up.
Quote:
The counter stages are D-type flip-flops having interchangeable CLOCK and ENABLE lines for incrementing on either the
positive-going or negative-going transition. For single unit operation the ENABLE input is maintained high and the counter
advances on each positive-going transition of the CLOCK. The counter can be cascaded in the ripple mode by connecting Q4 to
the enable input of the subsequent counter while the CLOCK input of the latter is held low.

Using the Enable inputs did mean I had to invert the CLK signal, so I used a simple transistor inverter for that, which as
an extra bonus makes it possible to use a 0-5V CLK aswell (while the rest of the circuit is powered from 12V). And there's a
reset switch for each counter but I don't think that needs any explanation.

The next thing I added (to the same panel) was a 4-bit (semi) random generator, well actually after some closer exmination it's
not really 4 bit random, but 1 bit that gets shifted through. It's the basic 4006(shift register) + 4070(XOR) combo used in
several circuits incl. designs by Yusynth and MFOS and it's also the random generator in my mad monkey sequencer. I did add
a switch to lock it into a sequence. I think it's 32 steps,. but have to check. There's one spare XOR which might be added to
give a more random output, or it could be used to invert the CLK in instead of the transistor inverter. But as with the divider,
the transistor makes it possible to use 0-5V signals.
Another option is to replace the RND/SEQ switch with one that has a center position and attach one side to the positive supply.
This would turn U2b into an inverter and if I remember correct that gives a 64 step sequence.


PHOBoS - Bandersnatch - Dual Binary Counter.gif
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PHOBoS - Bandersnatch - RND Generator.gif
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_________________
"My perf, it's full of holes!"
http://phobos.000space.com/ http://www.acidtrash.com/ Stickney Synthyards

Last edited by PHOBoS on Wed Nov 14, 2012 7:42 am; edited 2 times in total
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PHOBoS



Joined: Jan 14, 2010
Posts: 1807
Location: Moon Base
Audio files: 351

PostPosted: Mon Nov 12, 2012 4:16 pm    Post subject: Dual Sequencer
Subject description: Bandersnatch info
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next part was the sequencer for which I choose a CD4052 dual mux. One half is used to create a CV the other half for gates.
It has a 2 bit input which can be used in combination with the binary counter for a basic 4 step sequence. I added some
transistor buffers to these inputs, again to be able to use 0-5V signals.

the 10K resistors in series with the pots are added to prevent the ouput amp from clipping, later I added the 100K trimpot
to adjust the signal to the range of the vactrols. (so you could leave those resistors out)

to buffer the gate outputs I used a UN2981, A bit overkill with 500mA per output (it can control solenoids directly aswell Very Happy)
but I had one laying around, it's very easy to wire up and with 8 in/outs it was perfect for a dual version.


PHOBoS - Bandersnatch - Dual Sequencer.gif
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PHOBoS - Bandersnatch - Dual Sequencer.gif



_________________
"My perf, it's full of holes!"
http://phobos.000space.com/ http://www.acidtrash.com/ Stickney Synthyards

Last edited by PHOBoS on Wed Nov 14, 2012 1:11 pm; edited 1 time in total
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PHOBoS



Joined: Jan 14, 2010
Posts: 1807
Location: Moon Base
Audio files: 351

PostPosted: Mon Nov 12, 2012 4:17 pm    Post subject: Dividers
Subject description: Bandersnatch info
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let's see what's next, ah yes the dividers. these were added to provide some suboctave sounds (it's also
a very nice drone machine), but they can be used for other purposes aswell of course. One thing that is fun is to divide
the audio rate of an oscillator down to a CLK rate to control the sequencer which controls the oscillator.

There's not a lot to say about the schematic. A CD4040 with a reset button, a transistor inverter for the CLK and
a rotary switch to select the division. There are 4 of these installed in 1 panel (sloped, left side).

Another thing I installed in this panel is the main CLK oscillator. I didn't draw a schematic for this one, but it's made
with a 4093 NAND gate, a 500K pot and a 220nF/2.2uF cap. (switchable). (I can't believe I actually wasted 3 gates)


PHOBoS - Bandersnatch - Dividers.gif
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_________________
"My perf, it's full of holes!"
http://phobos.000space.com/ http://www.acidtrash.com/ Stickney Synthyards

Last edited by PHOBoS on Wed Nov 14, 2012 1:56 pm; edited 2 times in total
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PHOBoS



Joined: Jan 14, 2010
Posts: 1807
Location: Moon Base
Audio files: 351

PostPosted: Mon Nov 12, 2012 4:17 pm    Post subject: 4 Input Mixer
Subject description: Bandersnatch info
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To mix the oscillators (and/or suboctaves) together I added a simple 4 input mixer. a DC mixer would have been nice,
but not so easy to do with a single supply (I think). The circuit itself is very basic, an inverting summing amp,
followed by another inverting amp, and an attenuator to adjust the output level.


PHOBoS - Bandersnatch - Mixer.gif
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_________________
"My perf, it's full of holes!"
http://phobos.000space.com/ http://www.acidtrash.com/ Stickney Synthyards

Last edited by PHOBoS on Wed Nov 14, 2012 2:51 pm; edited 1 time in total
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PHOBoS



Joined: Jan 14, 2010
Posts: 1807
Location: Moon Base
Audio files: 351

PostPosted: Mon Nov 12, 2012 4:17 pm    Post subject: multiples and rhythm Generator
Subject description: Bandersnatch info
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The last panel I added was the one at the top, which I had actually cut to size before I even knew what I was gonna put in.
I did know I wanted some multiples so started with those. I did some experiments to see If I could give it some more functionality
and did come up with a way to use it as either a buffer or an XOR. But it was a bit confusing (especially without proper
labeling) to use. Still having the XOR's on my breadboard I decided to just add a switch to invert one of the outputs. There
are other ways to do this of course, it might even be better to use a 4049/4050, but it works. I also added some transistor
drivers for the LED's aswell this time.

And last but not least, the rhythm generator. This one is made with a CD4089 - Binary Rate Multiplier.
Posted Image, might have been reduced in size. Click Image to view fullscreen.

Besides external control for the ABCD inputs I added toggle switches to force them into a low or high state. When the CLR
input (pin 13) is made high it will just output the CLK in*, but only when the D input is high aswell. That's why there is an
2 diode/resistor OR gate attached to this input. So if the 'Roll' switch is closed it will make both the CLR and D high.

And then there is the INH input and 'On' switch attached to Inhibited In (pin 11). But I just figured out I screwed up here
and should have used the STR (pin 10) instead. So I'll have change that. Embarassed

*after just looking at the timing diagram again I realised it's actually inverted, so I will add a transistor inverter to
it, which again will make it possible to use 0-5V signals for this input aswell Very Happy.



ok, one more thing: The LED light. This was a USB light but I cut of the plug, replaced the LED with a bright pink one and
painted it in the same colors as the panels. It also has a transistor driver and is attached to the D output of the multiples.
This way I can let the Bandersnatch interact with other devices that have a build in lightsensor.

-------------------------------------------------------------------------------------------------------------------------------------------
edit: added a transistor inverter to the CLK input, swapped STR and INI pins, and added a transistor inverter
to this aswell. updated schematic.


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_________________
"My perf, it's full of holes!"
http://phobos.000space.com/ http://www.acidtrash.com/ Stickney Synthyards

Last edited by PHOBoS on Sun Nov 18, 2012 4:23 am; edited 3 times in total
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RingMad



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PostPosted: Mon Nov 12, 2012 5:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

Wow! Most frabjous!

Impressive build, for something you say you quickly threw together!

James.
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bubzy



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PostPosted: Tue Nov 13, 2012 12:24 am    Post subject: Reply with quote  Mark this post and the followings unread

reserved
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Blue Hell
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PostPosted: Wed Nov 14, 2012 9:14 am    Post subject: Reply with quote  Mark this post and the followings unread

Shocked

me though ... I'm not that reserved ... actually it looks pretty cool Cool

Laughing

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tony void



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PostPosted: Thu Nov 15, 2012 6:21 pm    Post subject: Reply with quote  Mark this post and the followings unread

Your work is very inspiring as always. This is beyond awesome. The Alice in Acidland theme you've got going fits these sounds perfectly. I usually lurk and make few reply posts but this deserves a big applause!! Thank you for sharing.
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PHOBoS



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PostPosted: Fri Nov 16, 2012 8:38 am    Post subject: Reply with quote  Mark this post and the followings unread

RingMad wrote:
Wow! Most frabjous!
Impressive build, for something you say you quickly threw together!
James.
thanks, the first panel was quickly thrown together but the rest took some more time Wink

Blue Hell wrote:
Shocked
me though ... I'm not that reserved ... actually it looks pretty cool Cool
Laughing
thanks Jan Very Happy

tony void wrote:
Your work is very inspiring as always. This is beyond awesome. The Alice in Acidland theme you've got going fits these sounds perfectly. I usually lurk and make few reply posts but this deserves a big applause!! Thank you for sharing.
Thank you very much, glad that it's inspiring as that is my main reason for sharing it. albino
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Last edited by PHOBoS on Sun Nov 18, 2012 5:52 am; edited 1 time in total
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analog_backlash



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PostPosted: Fri Nov 16, 2012 4:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

I know that it's been said before PHOBoS, but your galumphing building pace is quite incredible!

It's also giving me lots of ideas - thanks for sharing...

Gary


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PHOBoS



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PostPosted: Sun Nov 18, 2012 4:18 am    Post subject: Frumiousity Killed the Rabbit
Subject description: Bandersnatch demo
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Thanks Gary Very Happy

/me starts coloring pretty picture dwarf


here's another demo:


PHOBoS - Bandersnatch Demo's - Frumiousity Killed the Rabbit.mp3
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garcho



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PostPosted: Sun Nov 18, 2012 5:05 am    Post subject: Reply with quote  Mark this post and the followings unread

bravo! really well done
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analog_backlash



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PostPosted: Mon Nov 19, 2012 7:22 am    Post subject: Reply with quote  Mark this post and the followings unread

Brilliant demo! I notice that you've used some echo/reverb on that recording. Were you using a separate unit for that, or was it added digitally? Hope that's not an offensive question to ask...

Gary

P.S. No more pictures, until you've coloured that one in properly.
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PHOBoS



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PostPosted: Mon Nov 19, 2012 8:45 am    Post subject: Reply with quote  Mark this post and the followings unread

analog_backlash wrote:
Brilliant demo! I notice that you've used some echo/reverb on that recording. Were you using a separate unit for that, or was it added digitally? Hope that's not an offensive question to ask...

thanks, and no not offensive at all. I do realise that for a real demo I maybe shouldn't use any effects, but then again
I will usually add effects when I play with it anyway. Most of the time I'll use my trusty Pioneer EFX500, which
has a couple of other usefull features besides the effects. It has an input level control with a VU meter, which comes
in handy with loud signals (like CMOS). You can plug in a monosignal and it will route it to both channels, and it has
a 3-band tone control. (the effects are great too of course, especially with the beat sync option).

From there I usually route it to my miniKP (at least since I got it) which doesn't have any input level control
and can't really take any loud signals, which is why the EFX500 is so useful. And then it goes to my mixer which
also has some build in effects (mostly reverb/delay). So to answer your question, yes I was using a seperate
unit or actually 3 Very Happy

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JingleJoe



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PostPosted: Thu Nov 29, 2012 4:11 am    Post subject: Reply with quote  Mark this post and the followings unread

That thing both looks and sounds fantastic. I'm glad to see my old friend the 4089 in there too Smile it's a lot of fun and as you noticed: the key is to use the strobe input.
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