[sdiy] EDP gnat keyboard

[Scott Gravenhorst]

Dan Snazelle <subjectivity at hotmail.com> wrote:
>
>ALSO///when i first looked at the schematics for the GNAT i was 
>excited because it seemed they had found a simple way to convert 
>square waves to saw...but the more i look at it, the more it 
>seems that you might need to have the cv from pin 10 of the 4046 
>feeding into the 3900, so it is not a simple matter. 
>
>what does the signal from pin 10 actually do?

It is marked "demodulator output" and is the internal control voltage output brought to a
pin that was required to cause the PLL to track the input signal (assuming the PLL is
locked and settled).  One might call it a Pitch to Voltage value if used for music.

It is used in many circuits to recover the "data" signal that has been impressed by
frequency modulation onto a carrier, this composite FM signal is put at the input of the PLL.

>
>thanks so much
>
>
>
>
>
>
>--------------------------------------------
>check out various dan music at:
>
>http://www.myspace.com/lossnyc  
>
>
>http://www.soundclick.com/lossnyc.htm
>
>
>http://www.indie911.com/dan-snazelle
>(or for techno) http://www.myspace.com/snazelle 
>
>
>
>
>> From: tim102 at tstinchcombe.freeserve.co.uk
>> To: subjectivity at hotmail.com; synth-diy at dropmix.xs4all.nl
>> Subject: RE: [sdiy] EDP gnat keyboard
>> Date: Sun, 4 Jan 2009 17:20:47 +0000
>> 
>> Hi Dan,
>> 	I can answer directly (though re-ordered):
>> 
>>> is it simply a button underneath a key "button" or is it a 
>>> resistor chain like in a regular keyboard?  
>>> (ic10,1c25,1c33///those are 4051's right?)
>> 
>> There are no mechanical contacts (at least for the ordinary Gnat and the
>> 'Special'), it is all done with capacitive touch plates, so the note
>> annotations at the bottom of sheet 2 are simply large areas in the etched
>> PCB, in the form of a keyboard pattern. (And, minor point, the chips are
>> 4052s by the way.)
>> 
>>> I was wondering...on the keyboard multiplexer...
>>> do the 4051's connect directly to the keyboard? 
>>> and if so...what IS the method of keyboards giving a gate signal?
>> 
>> Each plate/note is scanned sequentially (via all the switches), and routed
>> to a flip-flop (IC28, sheet 3), whose output is triggered by the change in
>> capacitance if the 'key' is being touched - the test instructions document
>> has a fairly easily understood description of how it works, para 17, sheet
>> 3:
>> 
>> www.timstinchcombe.co.uk/synth/gnat/Gnat_Test_Instructions.pdf
>>  
>>> and thanks to TIM for  drawing those schematics! 
>> 
>> My pleasure! They get about a hit a day on my website, which I think is
>> probably quite a high level of interest in it, considering it is such a
>> small, obscure synth. I am also in infrequent touch with someone who is
>> trying to put a PCB together, but I haven't heard anything from him in
>> several months now...
>> 
>> Tim
>> __________________________________________________________
>> Tim Stinchcombe 
>> 
>> Cheltenham, Glos, UK
>> email: tim102 at tstinchcombe.freeserve.co.uk
>> www.timstinchcombe.co.uk
>> 
>> 
>> 
>> 
>
>_______________________________________________
>Synth-diy mailing list
>Synth-diy at dropmix.xs4all.nl
>http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>

-- ScottG
________________________________________________________________________
-- Scott Gravenhorst
-- FPGA MIDI Synthesizer Information: home1.gte.net/res0658s/FPGA_synth/
-- FatMan: home1.gte.net/res0658s/fatman/
-- NonFatMan: home1.gte.net/res0658s/electronics/
-- When the going gets tough, the tough use the command line.