[sdiy] NEWBEES are alive and kickin' !

[David Halliday]

One issue with circuit "complexity" is that the human ear is fiendishly
sensitive to pitch - much more so than amplitude.  Our range covers three
orders of magnitude and we can ( ie: most people with a "reasonable" musical
ear )immediately tell if a note is a fraction of a percent out of tune.

If you are going to use only one oscillator and only going to use it over an
octave or two range, you would be fine with your simple circuit but when you
want to have several oscillators and filters tracking over a many-octave
range, then you start getting into more complex circuitry.  Throw in parts
to compensate for temperature ( temp changes cause oscillators to change
pitch ) and power supply stability ( ditto ), you start getting into some
big circuits.

PAIA had a system ( the 2700  http://www.paia.com/fotoalbm.htm  ) with a
three octave keyboard that was based on linear tracking - there was a
separate trimpot for each key and you had to calibrate each one before it
was useable.  Volts per octave allows you to use simple resister strings or
ADCs.




-> -----Original Message-----
-> From: owner-synth-diy at node12b53.a2000.nl
-> [mailto:owner-synth-diy at node12b53.a2000.nl]On Behalf Of Peter van
-> Hamersveld
-> Sent: Tuesday, March 06, 2001 11:06 AM
-> To: synth-diy at node12b53.a2000.nl
-> Subject: [sdiy] NEWBEES are alive and kickin' !
->
->
->
-> Yes,
->
-> No, we did not give up.
->
-> After some thinking, and considering, we decided to start
-> REALLY simple.
-> So we (Peter) soldered a very simple square generating VCO,
-> consisting of:
-> 2 capacitors
-> 2 NPN transistors
-> 4 resistors
-> 1 trimpot parallel to the source to fake a Control Voltage
-> from a keyboard.
->
-> it worked :)
-> though not being a standard 1 V / Octave VCO, but having a
-> linear proportion between CV and frequency.
->
-> We noticed VCO's can be arse-kickin simple. A battery, a
-> resistor, a capacitor and a 'four-layer-diode' (sorry i do
-> not know the proper english word, but it's such a diode that
-> starts conducting at a certain (positive) voltage (NOT being
-> almost 0)) can already make a SAW Oscilator.
->
-> So, questions:
->
-> 1) Why are most VCO's (e.g. in tom's cookbook) having a
-> quite complicated structure. Just to make it 1 V/Oct? (than
-> that must be hard.)
->
-> 2) A bit the same question: Are there any circuits
-> converting a CV linear with frequency to a CV linear to note
-> (1V/oct)? Or do 1V/Oct need to generate the waveshapes in a
-> completely different way in order to be so?
->
-> thank you!
->
-> Your blockrocking' Bee,
->
-> -- Peter van Hamersveld, plons at gmx.co.uk on 06-03-2001
->