[sdiy] Ray Wilson's Single Bus Keyboard

[Ray Wilson]

Here is more info specific to the CD40106 and 74HC14.

http://www.musicfromouterspace.com/analogsynth/mmlogic.html

hope this helps.

Ray



----- Original Message ----- 
From: "Ray Wilson" <raywilson at comcast.net>
To: "Pat Kammerer" <spivkurl at wearerecords.com>; "sdiy" 
<synth-diy at dropmix.xs4all.nl>
Sent: Monday, March 07, 2005 6:03 AM
Subject: Re: [sdiy] Ray Wilson's Single Bus Keyboard


> Hi Pat
>
> You should be seeing a change in voltage every time you press a new key 
> whether you are playing legato or stacato at point Z in the circuit. That 
> point is the raw voltage that appears on the keyboard bus as you press 
> keys. When you are playing legato you get changes of 83 mV per half step. 
> When you play stacato you will get changes from  about -0.6 volts to the 
> voltage of whatever key you press. If you are not seeing changes in 
> voltage then check that the constant current source (IC2-A, Q1 and 
> associated components) is providing 833 uA by putting your DVM set to Amps 
> between the collector of Q1 and the the keyboard resistor stack. I say 
> AMPs first then decrease the range until you are sure that you have the 
> necessary 833 uAs flowing into the resistor stack. If all o that is good 
> then process to the differentiator (IC5-D and associated components). 
> Every time you hit a key or play legato you will see a spike at the output 
> of IC5-D. It is differentiating the changes in voltage from point Z. They 
> go positive if the change is positive and negative if the change is 
> negative (relative to the last note's voltage). The positive and negative 
> spikes are rectified by IC5-A and associated components (CR5 and CR6). Op 
> amp IC5-B is used as a comparator and you should see a ground to V+ going 
> spike at the kathode of CR4 every time you change notes. If you don't then 
> something is not connected correctly in the 
> differentiator/rectifier/comparator section. The ground to +V spikes 
> charge C14 via CR4 and effectively stretch the pulse a bit. The rising 
> edge of the stretched cleaned up pulse is dropped across R47 via C12. The 
> pulse is inverted by IC6-D and the rising edge of the inverted pulse is 
> dropped across R48 via C13. IC6-B inverts that pulse which is anded with 
> inverted point B (effectively the keydown logic). The upshot of thewhole 
> thing is that the negative going pulse at IC6-B pin 4 is slightly delayed 
> from the edge of the inverted point B signal. This insures that samples 
> (and triggers) are only generated when a key is first pressed, when a note 
> is changed with the key down (legato) and NOT when the key is released. 
> The last key down's voltage is the last sampled voltage and not the 
> no-key-down bus voltage (which is about -0.6V). The point T pulses are fed 
> to pin 13 of IC3-A and the current bus voltage is sampled onto C2 which is 
> buffered by high impedance buffer IC4-B. The output of IC4-B is fed via 
> R18 to the non-inverting input of  IC4-A whose output feeds the keyboard's 
> sampled and held control voltage to the world via 100 ohm output 
> protection resistors. (I know the outputs are probably short proof but hey 
> why not be belt and suspenders safe). I am going to update the page with 
> this info and I replaced the abysmally out of date timing chart (my 
> sincere apologies).
>
> I hope this helps
>
> Ray
>
> ----- Original Message ----- 
> From: "Pat Kammerer" <spivkurl at wearerecords.com>
> To: "sdiy" <synth-diy at dropmix.xs4all.nl>
> Sent: Monday, March 07, 2005 12:14 AM
> Subject: [sdiy] Ray Wilson's Single Bus Keyboard
>
>
>> Hi everyone!
>>
>> I just finished all of the stuffing and wiring of Ray Wilsons Single Bus
>> Synth Keyboard.  I have a partial problem with it.
>>
>> If anyone has built this circuit, then I'm curious.  What should I expect 
>> as
>> an interaction between the 40106 and the 4066?  Am I right in assuming 
>> that
>> part of the 40106's job is to cause the switch to close when a key is
>> pressed. I'm not getting CV output or trigger where I should.  I can 
>> trace
>> the keyboard reaction in the circuit, and I seem to run into a dead end
>> somewhere around the 40106 and the 4066.
>>
>> I've never use the 40106 before, so I'm a bit above my head.  If any one 
>> can
>> help me understand what's going on in the CMOS part of this circuit, then 
>> I
>> would be grateful for help in troubleshooting.
>>
>> Take care,
>> Pat
>>
>