Audio synthesis via vacuum tubes/Keyboard controller for tube synthesizer: Difference between revisions
Audio synthesis via vacuum tubes/Keyboard controller for tube synthesizer (view source)
Revision as of 18:39, 19 July 2022
, 1 year agoText replacement - " (archived) by Eric Barbour, 1997, with permission of the author" to " by Eric Barbour, 1997, with permission of the author - archived"
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== Background ==
Classic analog synthesizers commonly achieved equal tempering with one of two schemes: either a linear-response VCO (or VCOs) with a keyboard attached to a voltage divider network with exponential scaling; or, more commonly, a VCO with an exponential-to-linear voltage scaler circuit, and a keyboard with a linear divider network. Both schemes have their weaknesses. The former, when an LFO or other modulation voltage was added to the VCO input, did not offset in equal tempering. Also, the resistor divider often required unusual high-precision values. The latter scheme was easy to do, If one could control the temperature drift endemic to the exponential scaler (it usually relies on base-emitter exponential response to do the conversion, which drifts a great deal with temperature). The thermistors used in early exponential scalers are now difficult to obtain.<ref name="cont">[https://web.archive.org/web/20111001170916fw_/http://cgs.synth.net/tube/controller.html Controllers]
These problems do not apply directly to our tube synthesizer. Instead, we have a different problem: our very simple VCO is temperature-stable, but has a response that varies semi-randomly with the individual thyratron tube used. So, we not only have to use a non-linear divider on the keyboard; we have to use one that can be adjusted for the individual thyratron. If we want to use two or more VCOs in parallel, we have to match the thyratrons for pitch-to-voltage response curves.<ref name="cont" />
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* [http://www.j-omega.co.uk/ JW Electronics MIDI-to-Parallel converters]
* [http://metasonix.com/ Metasonix]
* [https://www.modwiggler.com/forum/viewforum.php?f=13 Metasonix] subforum at
[[Category:Vacuum tube synthesizers]]
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