Amp/Preamp Asylum

CJ ignored the tube manual

73.201.131.109

garymuffley

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In Reply to: RE: The MV75A had an Achilles' Heel posted by DustyC on January 09, 2025 at 06:54:48

The MV 75 had 590 vdc on the plates and if you used the LED bias, the idle current was 75 ma, which equals a dissapation of 44.25 watts of heat! The max rating for the 6550 is 35 watts for the plate. Is it any wonder tubes did not last or fail completely?

The solution was to change the cathode resistor from 20 ohms to 28 ohms and you can use the LED bias and not over dissapate the tube rating.

Follow Ups:

"Is it any wonder tubes did not last or fail completely?" - AbeCollins 12:21:54 01/11/25 (1)
"Is it any wonder tubes did not last or fail completely?"

The company was formed by two economists and I suspect they didn't bring an actual engineer onboard til much later - but I'm just speculating.
- RE: "Is it any wonder tubes did not last or fail completely?" - DustyC 19:21:14 01/14/25 (0)
  Bill Thallman was employee number 3 and got the products going. Founded Music Technology after his stint with C-J. He was the go-to guy for updates on their early units.

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