Circuitbenders Forum
Circuitbenders Forum => Circuitbending discussion => Synths & Samplers => Topic started by: gmeredith on November 22, 2007, 11:32:41 PM
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Now that I've finally finished my PHAT PHILTER BANK mod, here's how my SK8 looks with it installed, plus all my other mods!
The PHAT PHILTER BANK, for anyone who has been living under a rock the last month or so, is a true polyphonic VCF unit with CV input, cutoff and resonance, with envelope, LFO, external CV or manual control!
External CV inputs from a MIDI-CV box such as a Kenton box, to control the filter via MIDI, can be used to sequence the filter control remotely!
The SK8 also has an adjustable attack/decay on all presets/samples, as well as a whole stack of other mods like sample memory expansion, pitch bend wheel, LFO, MIDI input and multitimbral MIDI mode. There is also a separate drums VCF module.
The Phat Hilter Bank and also the single VCF drums module guides can be found at the Yahoo Casio SK group, in the FILES section of that site:
http://launch.groups.yahoo.com/group/CasioSK/ (http://launch.groups.yahoo.com/group/CasioSK/)
Cheers, graham
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And more
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And the PHAT PHILTER BANK close up!
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Front view labeled
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Thats some fantastic work there, you should get a medal for that one!
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Thanks! It took nearly a year of my spare time to get it to this, though. The Phat Philter Bank took about 3 months of that time!
I've attached below the original PCB layout of the single VCF filter by Tom. You can simply change the input and output resistors to suit whatever you're putting it in. It's really easy to make, too - you can just print this PCB out on cardboard at actual component size, then just poke the components through the cardboard and solder their legs together on the other side. Really quick and easy!
Cheers, Graham
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Wonderful work! I wish I was this good... :-\
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Thanks, mq!
Be encouraged to know that I barely knew any of this stuff before I began it; help from kind people on forums such as this one and others steered me in the right direction on circuits and info, so that I eventually knew what to do before I even picked up a soldering iron to start on it. You might say I'm pretty chuffed with the people on this forum ;)
Cheers, Graham
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would this filter work at a lower voltage?
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Yes, it will work down to about 3V DC, although it might not have much output at that voltage.
Cheers, Graham
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Would be about 6v dc off four AA batteries. I want to add some filter action to my vetech laptop.
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6V will run it fine.
Show us how you adaped it to the vtech when you're done he he!
You might need to add a separate on/off power switch for the filter - the vtech may not actually "switch off" completely when you hit the power off button, but just be in hibernation - like the Casio SK's. I flattened a few batteries with the filter still running after powering down because the part of the circuit I tapped into for the filter power still stayed on when you power the SK down, for memory retention etc.
Cheers
Graham
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Would be about 6v dc off four AA batteries. I want to add some filter action to my vetech laptop.
When you're done, post some pics/videos. What VTech laptop have you got?
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Sweet, I get paid this week so can buy all the nice components.
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hi,
you made me wet ;)
is there a possiblilty to get the schematic?
Or ist it this one .... from "Circuit Snippets"
http://www.geocities.com/tpe123/folkurban/fuzz/snippets.html
(http://www.geocities.com/tpe123/folkurban/fuzz/simplevcf.gif)
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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
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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
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Where do i sign for one of those? hats off if you pull it off sounds like it could be amazing.
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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
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Hiiiii,
Does it make alot of difference what type of capacitors are used?
Cheers!
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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.
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Just a thought...
To simplify the quad filter circuit further has anyone tried making it with 2 x NE5532 dual amps?
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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!
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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
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ah cool, i was wondering how you got the sine function.
Also any thoughts on inverting the envelope filter function?
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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
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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 (http://www.jaycar.com.au/productView.asp?ID=ZL3971) pic has 14 pins, not 8)
would a circuit built around a LM741 http://www.diystompboxes.com/smfforum/index.php?topic=89022.0;prev_next=next (http://www.diystompboxes.com/smfforum/index.php?topic=89022.0;prev_next=next) work just as well?
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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.
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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
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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