Took me a bit longer because I did not realize that these are mirror image top plate.
20mA is OK, if you have enough HT to load anode 10-12K, otherwise it will be not enough gain, c3m has S 6.5mA/VThanks @Alexz for sharing your experience. I am still in the middle of adjusting the amp. Trying to get to 220v at the plate of C3m. I am currently running at 20ma at cathode and 3ma at g2.
oops... just realized that it is 20ma CATHODE... (Ia+Ig2), so you run Ia at about 17ma.Thanks @Alexz for sharing your experience. I am still in the middle of adjusting the amp. Trying to get to 220v at the plate of C3m. I am currently running at 20ma at cathode and 3ma at g2.
Well it is done. Finished the project last night. Well after many tweaking I am finally happy with all the voltage.
B+ on 300B around 420v, 68V cathode with 1K cathode resistor. 215 at the C3M plate 5.5V at cathode with 3ma at G2. I am running around 20ma total. Hum at one amp is 3.7mv and one at 4.8mv.
First impression last night. I love it. The amps are fast with deep and wide sound stage. I cannot judge the tonality yet until they burn in. But the bass and high are more extended than my 310A/300B which is more dreamy like in the mid range. Well time will tell. I will list my part selection on my next post, need to work on it since I had changed many parts before settle into the final amps.
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I'll tell the family that the kid's extra-curriculars are on hold until I spend a few days at the bench in the basement.