[sdiy] Keyboard Control

[harrybissell]

Hi Ray (et al)

I did it differently... I take the output from the current source... and I
ground the
resistor matrix through the keys.

You are picking off the voltage to the 'bus buffer'.

I did the grounded key so that I could get two CV from the keyboard. I used
two current sources, and inverted the upper one so that I had low note / high
note
priority

H^) harry

Ray Wilson wrote:

> Hi Guys
>
> Just a note on this. I feed the current from the top end of the keyboard and
> I still get low note priority because when more than one key is pressed you
> are essentially bypassing all of the intervening resistors and since the
> current is constant (in the design I use) you get the voltage that is
> dropped across the low side of the resistor ladder.
>
> Ray
>
> -----Original Message-----
> From: owner-synth-diy at dropmix.xs4all.nl
> [mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of harrybissell
> Sent: Saturday, October 18, 2003 3:03 PM
> To: Thomas Holley
> Cc: synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] Keyboard Control
>
> Yes, you are right. By taking the output from the low side you will
> also get low note priority (which I for one, insist on :^)
>
> H^) harry
>
> Thomas Holley wrote:
>
> > Thanks Harry,
> >  I have the keyboard controller arranged so that the current source is to
> > one end (HI) of a resistor ladder and the other end (LO) referenced to
> > ground. The keyboard is from an old broken ensonique with little spring
> > contacts on each key. I have it so when the key is pressed the contact
> > grounds that point in the resistor ladder. The reference voltage for the
> > controller is taken from the top of the resistor ladder where the current
> > source connects (copied from an old ARP patent). With this arrangement I
> > think the current source should then go on the low (left) key side to give
> > the highest voltage reference to the high (right) keys. Is this right or
> do
> > I have it turned around?
> >
> > Thomas
> > ----- Original Message -----
> > From: "harrybissell" <harrybissell at prodigy.net>
> > To: "Thomas Holley" <thomasholley at adelphia.net>
> > Cc: <synth-diy at dropmix.xs4all.nl>
> > Sent: Saturday, October 18, 2003 1:57 PM
> > Subject: Re: [sdiy] Keyboard Control
> >
> > > Hi Thomas
> > >
> > > Higher pitches (to the right side of the keyboard) get higher
> > > voltages...
> > > so the current source should go on the highest note side...
> > >
> > > H^) harry
> > >
> > > Thomas Holley wrote:
> > >
> > > >     I have a rather fundamental question. In a keyboard controller
> > > > resistor ladder, does the high voltage side go to high pitch key or
> > > > the low pitch key. I have been tinkering with an old keyboard and
> > > > soldered up a 100 ohm resistor between each key for a nice ladder when
> > > > it finally dawned on me that I had not a clue which side to put the
> > > > current source on and which one to ground. Thanks for your help Thomas
> > >
> > >