circuit to scale 0-10v to 0-5v?

[sneakthief]

pardon me if this is a rudimentary question, but is there a simple way to scale a voltage source of 0-10v to 0-5v?

i've built a lovely MIDIbox CV midi-cv converter ( http://www.ucapps.de/midibox_cv.html ) and am in the process of adding CV-input functionality. unfortunately the analog inputs of this project only accept 0-5v.

once i get the input voltage it scaled down, the software will then convert the voltage to a note number - and with the help of a few ASM gurus, we're going to create a scale-quantizer and harmonizer.

Info: the MIDIbox CV supports 8 CV+Gate & sync out and can be built for as low as $60-70 US with a little help from microchip & analog devices

[etaoin]

[sneakthief]

ok i figured as much thanks!

[Thomas Henry]

The divider takes care of the voltage levels, as explained above, but there's more to think about.

You should also consider the output impedance. According to the Electronotes standard, the output Z of most synth circuits should be 1K. This is easy to arrange here. Besides computing the divider voltages mentioned above, arrange for the parallel resistance of the two resistors to be equal to the desired Z.

For this case, we want 0 to +10V to go to 0 to +5V, with a output Z of 1K (common for Electronotes circuits). Choosing both resistors to be 2K gives the required voltage reduction (10V max to 5V max), and in parallel they are 1K, a good impedance to drive other modules without worrying about shorted outputs.

My rule of thumb has always been: design a circuit to (a) be elegant, and (b) not burn up or cause other modules to burn up, no matter how stupid the operator may be.

Thomas Henry

[sohcahtoa]

Thomas,

I don't see any parallel resistors in that circuit, are you talking in reference to some other circuit?

Furthermore what is "Electronotes" ?

[etaoin]

[mono-poly]

This would work out good both directions.

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[EdisonRex]

[Uncle Krunkus]

I am also having problems with the parallel resistance idea. They are in series aren't they?

[blue hell]

[sneakthief]

many thanks to everyone for the input!

re. Electronotes - In 1975 the author of Electronotes, Bernie Hutchins, wrote a book called the "Musical Engineer's Handbook" - both the Electronotes series and this book have basically been the reference and inspiration for a good portion of todays modular synths.

AFAIK Don Buchla, Bob Moog and Serge Tcherepnin were all subscribers to Electronotes and were definitely inspired by the schematics and/or contributed their own to the magazine.

I would even go so far to say that most current modular manufacturers have "borrowed" designs from the Electronotes series ; )

ps. Mr. Henry, it's delightful to have you here

[Uncle Krunkus]

Thanks Jan,
suddenly it all makes sense!
I think.

[Thomas Henry]

[Scott Stites]

Mmmmmmyep. Actually, one of my favorite Thomas Henry tricks is to get a 1K impedance out of a 15V -> 5V divider. The signal passes through a 3K resistor with a 1.5K resistor to ground. Violin! - you get a 5V output out of 15V and it's a 1K output impedance. Very handy for converting a comparator signal that rails at +15V to a +5V signal (say an Electronotes standard +5V gate or trigger). Learned that one from the Potpourri module in "Build a Better Music Synthesizer".

What's that? You use 10V gates and triggers? No problem, swap the two resitors around and Viola! - you get a 10V signal with an output impedance that is still 1K.

The above explains the output resistors on the Klee gate bus, and the note about the 10V gates/triggers.

Cheers,
Scott