[sdiy] Two questions - VCO standards and Differential Op-Amp Circuit

[Laurie Biddulph]

Hi Chris,

I am of the opinion that with the footage control set to the 1' rage and with all other control inputs at 0V that the VCO should follow the conventional MIDI-Note range as listed here <http://www.elby-designs.com.midi-cv/midi-note-table.pdf>

Best Regards

(Mr) Laurie Biddulph
Mobile: 0404 846 943

Elby Designs
ABN: 70 022 727 605
http://www.elby-designs.com

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  ----- Original Message ----- 
  From: Chris Manders 
  To: synth-diy at dropmix.xs4all.nl 
  Sent: Monday, March 06, 2006 9:45 AM
  Subject: [sdiy] Two questions - VCO standards and Differential Op-Amp Circuit


  Hi folks

  Just two questions I have for you knowledgeable guys
  to answer, please?

  Regarding VCOs. Is there some sort of standard
  Frequency output setting? i.e. with the CV input at
  Zero (or disconnected) the VCO tunes exactly to Middle
  C? This would seem appropriate perhaps? Or is it best
  to set them to a very low level, as the CV inputs will
  generally be positive and cause a rising of pitch?
  My VCOs work fine (built on breadboard) but I have not
  set them up yet for anything specific. I know that I
  could set them up for anything I wanted but I would
  like to adopt an appropriate standard if there is one.

  Secondly, and on a different subject – Say I have an
  Op-Amp stage set as a differential amplifier, and
  running from a single 15 volt supply. If I set the
  inputs up so that the output should be a negative
  voltage, would it damage the Op-Amp as it couldn’t
  output this negative voltage as it is powered from a
  single supply rail?
  For this situation, would the output of the Op-Amp be
  an inverted positive difference, or would the Op-Amp
  output be Zero for all negative results like this?

  Thank you in advance
  Chris


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