Doepfer

hi group, especially florian,

i'm thinking about building a simple keyboard replacement - different
arrangement of the keys but still the tempered scale. i think i know
how i want to do it, but i'd appreciate any advice that anybody may have.

first question to florian (or anybody that has his book griffbereit):
on page 32 of your book "synthesizer" you have a simple diagram of a
control voltage generator, each resistance corresponding to one key on
the keyboard. what would you recommend as a suitable value for the
resistors? and should i be using 5v as shown in the previous diagram,
or 12v as stated in the text?

secondly, i intend to produce the gate by simply putting the control
voltage through a comparator - everything above 0v opens the gate.
does anyone foresee any problems here?

and any other problems i've overlooked?

all comments much appreciated,

stu

Stu-
  I know this may be out of your price range - and may not fit your  
design criteria - but for ease of assembly have you thought of the  
Doepfer CTM64 or MKE combined with a  MCV4 or A-190. The limitations  
are no portamento and you will be defaulting to tempered scales but  
you could have LOTS of switches/buttons plus the added modulation and  
pitch bend inputs.

-James

On Feb 3, 2008, at 3:49 AM, Stu Grimshaw wrote:

> hi group, especially florian,
>
> i'm thinking about building a simple keyboard replacement - different
> arrangement of the keys but still the tempered scale. i think i know
> how i want to do it, but i'd appreciate any advice that anybody may  
> have.
>
> first question to florian (or anybody that has his book griffbereit):
> on page 32 of your book "synthesizer" you have a simple diagram of a
> control voltage generator, each resistance corresponding to one key on
> the keyboard. what would you recommend as a suitable value for the
> resistors? and should i be using 5v as shown in the previous diagram,
> or 12v as stated in the text?
>
> secondly, i intend to produce the gate by simply putting the control
> voltage through a comparator - everything above 0v opens the gate.
> does anyone foresee any problems here?
>
> and any other problems i've overlooked?
>
> all comments much appreciated,
>
> stu
>
>
>
>
> Yahoo! Groups Links
>
>
>

--- In Doepfer_a100@yahoogroups.com, James Husted
<the_ersatz_planet@...> wrote:
>
> Stu-
>   I know this may be out of your price range - and may not fit your  
> design criteria - but for ease of assembly have you thought of the  
> Doepfer CTM64 or MKE combined with a  MCV4 or A-190. The limitations  
> are no portamento and you will be defaulting to tempered scales but  
> you could have LOTS of switches/buttons plus the added modulation and  
> pitch bend inputs.
> 
> -James
> 

hi james,

that was actually the original plan, but the pure analog attempt has a
few features that i find appealing: power comes from the modular, the
resistors will not be completely accurate, i save myself a midi-to-cv
converter (although i have a couple) and it's all so hands-on when it
comes to adding pitch bend and firing off a gate while holding a note
etc. i save myself a ton of wiring too - all of which needs to be
soldered!

if it is as simple (though rudimentary) as i think it is, then the
analog way is easier, as well as offering opportunities for more
individual features/limitations/quirks. i love quirks :)

relying totally on a single control voltage solution (so no release
envelopes here unless we inclue a s+h) also allows me to use the a112
sampler to record melodies and such - the necessary gates are still
produced by cv>0v and therefore don't need to be recorded separately.
my dream is to leave the electribe at  home :)

cheers,

stu

> Stu-
> I know this may be out of your price range - and may not fit your
> design criteria - but for ease of assembly have you thought of the
> Doepfer CTM64 or MKE combined with a MCV4 or A-190. The limitations
> are no portamento and you will be defaulting to tempered scales but
> you could have LOTS of switches/buttons plus the added modulation and
> pitch bend inputs.
>
> -James

By the way: the new A-100CGK (CV/Gate keyboard) will be availabe as an OEM
version too (i.e. without keybed and case). Christian is about to finish the
firmware and I think it will be ready still in February.

Best wishes
Dieter Doepfer

> hi group, especially florian,
>
> i'm thinking about building a simple keyboard replacement - different
> arrangement of the keys but still the tempered scale. i think i know
> how i want to do it, but i'd appreciate any advice that anybody may have.
>
> first question to florian (or anybody that has his book griffbereit):
> on page 32 of your book "synthesizer" you have a simple diagram of a
> control voltage generator, each resistance corresponding to one key on
> the keyboard. what would you recommend as a suitable value for the
> resistors? and should i be using 5v as shown in the previous diagram,
> or 12v as stated in the text?
>
> secondly, i intend to produce the gate by simply putting the control
> voltage through a comparator - everything above 0v opens the gate.
> does anyone foresee any problems here?
>
> and any other problems i've overlooked?
>
> all comments much appreciated,
>
> stu

I can send you the scan of an article in the German electronic magazine
FUNKSCHAU I wrote in the eighties. It describes an analog working CV/Gate
keyboard with a resistor chain. Simple send me an email directly to
hardware(at)doepfer(dot)de.

Best wishes
Dieter Doepfer

Hi Stuart,

> first question to florian (or anybody that has his book griffbereit):
> on page 32 of your book "synthesizer" you have a simple diagram of a
> control voltage generator, each resistance corresponding to one key on
> the keyboard. what would you recommend as a suitable value for the
> resistors? and should i be using 5v as shown in the previous diagram,
> or 12v as stated in the text?
The Resistors depend on the range of the keyboard and the used voltage.
If you want well tempered tuning, then the voltage 'around' one resistor 
should have 1/12th Volt.

Exmaple: You provide 5 Volts, the keyboard should have two octaves. Then 
it might look like this:

          R1    Rx    Rx    Rx           Rx    Rx    R2
Ground--RRRR--rrrr--rrrr--rrrr--[...]--rrrr--rrrr--RRRR--+5V

The Resistor R1 should have 120 kOhm, R2 should have 240 kOhm, each of 
the 24 Rx's should have 10 kOhm. The lowest "key" will be between R1 and 
the first Rx and will provide 1Volt.

> secondly, i intend to produce the gate by simply putting the control
> voltage through a comparator - everything above 0v opens the gate.
> does anyone foresee any problems here?
The lowest note must provide more than 0 Volts (and it should be 
noticable above 0 Volts to prevent erronous triggerings)

> and any other problems i've overlooked?
You need also a sample & hold to store the keyboard after you released 
the key. The S&H has to be triggered by the gate.


Florian

Hi

> if it is as simple (though rudimentary) as i think it is, then the
> analog way is easier, as well as offering opportunities for more
> individual features/limitations/quirks. i love quirks :)
These aren't only limitations. Having the gate and S&H-triggering 
separated provides also some features, which are usually not available. 
(think of transposing a sequence within the timing of some external clock).

Florian

hi florian,

that's pretty much the idea - the smaller the modules, the more
spielraum you have for weird ideas like... externally clocked
transposition??

so release phases, pitch bends and all that will be realised using
modules that exist already anyway.

thanks for the resistance values, which i understand. but the line
that looks like you're quoting my dog !?? sorry, it's rose monday and
the house sounds like a stadium. i know i should get it, but i can't
think.

:)

stu

thanks for the help with this, especially james, dieter and florian.
i've now got schematics for a mono keyboard, a two voice keyboard and
florian's original diagram :) 

which should keep me busy for a while.

stu