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In Reply to: Re: plate load-"brilliant" question posted by dave slagle on October 29, 2001 at 14:53:35:
I used an 866A under the cathode in a preamp I was fiddling with a few weeks ago. It looked really cool, but there were problems with noise. I'm not sure if it was from that or something else - it was a new design that I just sort of did for kicks and I've disassembled it since. It only dropped about 10 volts, though.John
Follow Ups:
was it the same 60hz noise tom mentioned from the 5Y3???dave
Well, there was 60hz hum. Plenty of it. However, I was using SV572-10's as a linestage, so that could have been the cause of that. The reason I lost interest was that there was a ton of higher frequency hash. When I turned on my speakers, there was just solid noise. I don't have a scope, so I couldn't look at. I didn't really ever track down what the problem was. I just unclipped it all and moved on to other things. It looked cool, though - the bright white 572-10's and the blue 866a's (I had them in the supply too).Reading your other posts now, I did try a hum balance pot on the 866a filament - it helped some, but not enough. I had a huge amount of voltage present on the outputs initially and tweaking the hum pot got it low enough for me to actually turn on my speakers to listen to. Well, I never actually listened to anything through it...
John
i guess the whole 83 in the cathode goes farther down on the to-do list... :_(dave
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