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Old 15th April 2009
  #25
All tests except where noted were done on stock channels. The intention was to determine what it was before I messed around with it.

What was interesting to me was first the noise floor on the master. I didn't do an unweighted signal to noise test as the time was too short. I did notice the noise floor remained constant whether channels were assigned or not, whether the faders were up or not. The noise did go away when the master fader was attenuated. This I don't notice in other designs including the 80B. My similar sized Delta 200 24 channel console is silent in comparison.

The other item was the stereo crosstalk. -58 db as a straight line is unusual. Most consoles show better crosstalk at lower frequencies, falling off at higher frequencies like 10k hz. -60 db crosstalk at 10k hz is common, but most with that spec will show better than -70 db at 1k hz. That requires further study to determine the cause but one is I suspect the pan pot design. This console uses a single pan pot with the wiper as ground and the left/right buss feeds at the other pins. Most consoles use a dual pan pot with each one wired as an attenuator for better channel cut off. My Delta uses that type of pot in the feedback loop of an opamp pan buffer. It gets -90 db at 10k hz crosstalk.

Jim Williams
Audio Upgrades