f/v converter & log circ

[Paul Perry]

At 11:35 PM 6/06/97 +-200, Jonas Karlsson wrote:
>Hello!
>I am thinking about building a frequency to voltage converter and use it to
control the synthesizer i'm building. The f/v converter should use a
squarewave (from my D110) at the input and create one voltage that is
proportional to the frequency, and one that is proportional to the amplitude. 
>
>Is this a good idea? This way I don't have to build (or buy) a MIDI to CV
converter. 
>
>The v/f part is easy to design, but the problem with it is that the output
of it is exponential, so I have to build an exp. to lin. converter. Is there
an easy way to do this?
>
>I really would appreciate any comments and ideas on this subject.
>
>Jonas Karlsson
>
the answer to this, and almost every other purely analog electronic question
ever asked in this list, is to be found in "the Art of Electronics" vol 2
Horowitz & Hill
Cambridge University Press(available many languages)

in this case the log convertors are on p254 and p255
they are based on the - not cheap- LM394 supermatched npn pair but if you
are experimentally inclined i think the CA3046 transistor array should do -
it's been
used before in this type of thing

Winfield Hill one of the authors often replies in newsgroup
sci.electronics.design
have a look via DejaNews newsreader

i once lost a sale for my midi-cv unit (which as a standard feature puts out a 
voltage directly prop to frequency of input midi note) when i showed that the 
MS20 could in fact look at the output from any midi module & generate a CV
and gate
by itself...... so if you have a MS or Yam CS series synth all you need is
the F to V..

Paul Perry mfg Frostwave MIDI-CV convertor
>