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update 2










Hot diggity dam! Got BOTH the 845 and the 813 amps up and running this morning per the attached schems. I took blackplate's advice and put a capacitor in front of the output tubes and was then able to get things running well. Both amps now sound really good, with the triode connected 813 being particular pleasing. The operating points for 845 are pretty close to those I was trying to hit that Mike Lafevre said were a favorite in Japan. Once I had the 845 running well, I basically just dropped the 813 in it's place with a few changes to accommodate that tube. I have no idea if the operating points of the 813 are considered to be good ones, but when you look at the plate curves for the 813 it seems to be in a pretty linear area.
If anyone has any suggestions on other operating points for the 813, I would like to hear them. These are both easy to build, good sounding amps. The only hassle is the 10-volt filaments. Even then, by using the resistors off of the filament pins to balance out the hum, I am able to use AC voltage on all the filaments with so little hum I have to have my ear right next to a speaker to hear it.

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  Kimber Kable  

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