Christian Klippel wrote:
Am Freitag, 17. November 2006 17:26 schrieb Steffen:
I read about it in Delton T. Horns Music Synthesizers: A Manual of Design and Construction, if i recall correct, where the author suggested to use a S/H in connection with such a converter to save CPU power (when one wanted to keep a given CV for a period of time (faster then the port)).
this is only usefull if you want to digitize a changing signal. you use the s&h circuit (usually just a capacitor and a switch) to "freeze" the current value, so it stays stable while you digitze it. to digitize a signal, you basically need a dac, s&h and comparator. you load the s&h, set a value at the dac, and compare the two voltages with the comparator. you change the dac value so long until you have a match between the two voltages. then you discharge the s&h, and go ahead with the next sample.
Not only useful for digitizing an analog sample into the digital world, but also useful as a multiplexer. If you build a converter using one single ADC, you could share it to say 8 channels by sending them one at a time. Often (but not always) cheaper and easier than using 8 normal ADC's. Multiplexing with S&H works even on a low pass filtered PWM-signal if thats what someone (?) was planning on using...
mvh//Svante - with a homebuilt midi to 8-channel CV somewhere in some drawer...