[sdiy] keyboard schematics

[fmg]

Osamu (Sam) HOSHUYAMA wrote:
> 
> Hello Fabio,
> 
> fmg wrote:
> > Sam,
> >
> > I'm looking at Moritas keyboard schematics of your site (moritaKB.gif)
> > and wondering if you can help me with some questions.
> >
> > 1. Do you know the value of the Rs in the voltage divider (or the
> > numbers of keybrd contacts), or the value of zeners in both sides of
> > this chain ?
> 
> That part is very typical with old monophonic keyboards.
> I guess 100 ohm resistors are OK.
> 
> The value of zener diodes is not important here.  Upper side is just
> a voltage source and the lower is a current source.
> 
> The voltage defines the highest KB output, which should be determined
> by the spec of the VCOs you use.
> 
> The current must be set so that the voltage across each 100 ohm is 1/12
> volts.
> 
> > 2. What say the vertical text that point to the 4558 ? (the one which
> > have the + input to the keyboard)
> 
> "Calculates the voltage of high note."
> 
> > 3. The output of the other opamp of this 4558, goes to the 10k of the
> > 741 immediatly below the S&H buffers ?
> 
> Yes.
> 
> > 4. What say the text below this 741 and the S-T that follow it ?
> 
> What's S-T?
> 
> "Detects whether the number of pressed key(s) is multiple."
> 
> > Sorry to be so inquisitive :-) I saw the PE msonic rf keybrd, the
> > moog 952, and the Morita's, and liked this.
> 
> Why do you need duophonic keyboard?
> Morita's design requires a 2-contacts-per-key keyboard.
> (The bottom left switch represents all the trigger contacts.)
> Do you have one?
> 
> Regards, Sam Hoshuyama
> -- - ---  - -- ------ - -------- -- - ---- -
> Osamu (Sam) HOSHUYAMA      houshu at rogers.com
>                               Ottawa, CANADA
> --------------------------------------------

Sam,

Thanks for the answers.

I have no keyboard. The questions was just for learning.

I surf synth-related sites and when find something that I don't
understand I usually bother the author of the site with questions.
(I acquired this annoying habit two months ago when joined this list)

What I really wish to build is a guitar-style controlled synth, but
that's another story and I don't want to keep boring you or the list
with my bad English.

Thanks again for the answers.

Fabio Gonzalez
Posadas, Argentina