Casio SK PHAT PHILTER BANK pics!!

[gmeredith]

Hi Catweazle, How' you been? Haven't seen you around the forum traps lately. Still studying? What's your latest project, if any?

Yes that schematic is the one. It's Tom Escobedo's Q&D VCF design. I chose the high resonance schematic circuit on that drawing for the Phat Philter Bank, with a few extra input attenuators and caps to suit the SK's voice levels.

Cheers, Graham

[catweazle]

Hi,
thanks for the info! I'll try it.
yes studing and working ... a lot of ideas but no time.
I did no circuitbending and 8bit microcontroller stuff for a while...
It's also that prob with beginning things and comming to the conclusion that
a similar thing is on the market. Mostly buying that thing is cheaper than DIY.
(like the SK-MIDI as it is available as an working kit

But my intention is generating 8bit lofi audio with cheap microcontrollers.
Emulating circuitbent stuff for example
- most bends affect the adressing of a stored sample
  which can easily done with a uC and little extra RAM (like the SKs)
  bending is done in software externally controlled...

or Different sequencers
Klee Sequencer   
The Muse
, "GameOfLife / Cellular Automata" and all the Chaos algorithm stuff
http://ultravires.net/ensyns.html  and
http://www.noyzelab.com/research/research.html

and so on ...

My goal is an easy and cheap modular system controlled by a master unit.
All modules (slaves) are controlled by the main unit (microcontroller with pc interface)
over i2c bus (2-wire bus) which is >10 times faster than midi and you don't need that In/Out/Thru garbage.
Since only two wires are needed. 127 Devices can theoretically be controlled.
I2C is implemented in the most uC with baudrates up to 1Mbit/s. (and I don't like MIDI)
The Main Unit can act as a stupid PC->I2C converter or as a stand alone master controller.
MIDI -> I2C is possible, too. A touchscreen (320x240) acts as an human user interface
like the "Lemur" or the "Fairlight CMI" (but all cheap and easy with 8bit microcontrollers)

The modules connected to the I2C bus can be everything..
- a input device (controllers, switches, pots,  sensors ...)
- a output device (I2C controlled bending, analog CV/Gate, DIN Sync etc)
- Filter-, Synth-, Effect- Modules like on all the common analog modular systems (but digitally controlled)

Circuitbending can be done with Analog Demultiplexers from the 4000-Series  like the
http://www.ee.washington.edu/stores/DataSheets/cd4000/cd4051.pdf
or 4097 (2x4051)  ...  4066 (4 switches)
OR "digital potentiometers"
controlled by a microcontroller which is controlled by the master unit.

RetroTechnologies from the past with new components. Most old things where very intuitional.
... a long way to go

... ok that's not real circuitbending, I know ...
but can make it much more controllable and comfortable

Gtz
Eric

[Signal:Noise]

Where do i sign for one of those? hats off if you pull it off sounds like it could be amazing.

[Circuitbenders]

I've just split this into a new topic about catweazles Fraktal/CellilarAutomata Synth.

The new thread can be found here http://www.circuitbenders.co.uk/forum/index.php/topic,573.0.html

[Dj Task Manager]

Hiiiii,

Does it make alot of difference what type of capacitors are used?

Cheers!

[Gordonjcp]

Possibly.  Ceramic capacitors are drifty as hell.  If you use them in the filter cell you'll be able to sweep the filter by warming them with your hand ;-)

You may as well use el-cheapo polyester film capacitors for the small ones - they're only a little more expensive than ceramic but way more stable.

[Dj Task Manager]

Just a thought...

To simplify the quad filter circuit further has anyone tried making it with 2 x NE5532 dual amps?

[Dj Task Manager]

A couple of other thoughts too...

I was also wondering what lfo circuit gmeredith used

and if there would be a way of inverting the envelope(s) from the sk to get the opposite response from the filter.

Cheers!

[gmeredith]

Sorry I missed this thread reply - sorry for the late response!

LFO circuit - just a simple 555 timer - i wanted to put in something simple that also did triangle waveform as well but nothing was out there at the time that was as quick and easy. I must revisit this sometime soon when I modify my soon-to-be Casio DM100...

Cheers, Graham

[Dj Task Manager]

ah cool, i was wondering how you got the sine function.

Also any thoughts on inverting the envelope filter function?

[gmeredith]

You mean so that instead of the filter going wwwaaaaawwww when you play a note it would go aaaaawwwwwaaaaa? I think you would need a separate ADSR circuit first to achieve that control over the DC control lines that control the note volumes and envelopes. I did my Slo-AD mod to get slow attack and decay responses, which then also controls the filters in the same fashion, but it's not a true controllable ADSR circuit - it's just some capacitors in parallel with the control lines to slow down the attack and decay. I was hoping to find a siimple ADSR circuit that would run off a single 9V source but couldn't find one - they all ran off split rail -12V-0V-+12V power supplies. Anyone know of such an ADSR circuit?? (which is also simple and quick to build and not bulky?)

Cheers, Graham

[wax+wire]

The circuit for the PHat Philter bank seems to be built around an IC - NE5534AN.  this looks a bit hard to get access of in australia from a quick search (I think, as http://www.jaycar.com.au/productView.asp?ID=ZL3971 pic has 14 pins, not

would a circuit built around a LM741 http://www.diystompboxes.com/smfforum/index.php?topic=89022.0;prev_next=next work just as well?

[gmeredith]

Not as well - a lot noisier, and the feedback less controllable. I tried all the popular replacements, but the 5534 was the best. That link for the 5534 is correct - ignore the picture that is next to the description - that picture is for the 5533 14 pin variant - the 8 pin variant is called the 5534. Download the datasheet that's on the page for a detailed description - it contains both.

[wax+wire]

I started building mine today.

I'd planned to build it on one of those non-soldering dummy boards to test it out, but with all little tricks like cutting IC legs and things I just got straight to it on a vero board.

I found it hard however to work out how to orientate my board between cutting traces then flipping the board

So i flipped the trace cuts in PhotoShop and redrew them.

I can upload a picture of the traces inverted on the board - but the upload folder is full it says

[gmeredith]

You can email it to me at gmeredith1@yahoo dot com dot au

I'll put it up on the Casio SK group downloads section.

It was a bit of a mistake of me designing it so miniature, it has caused a lot f problems. If you do redesign it on normal PC hobby board, that would be great! I got half way redesigning it then life got extremely busy and I never finished it.

Cheers, Graham