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    Building, troubleshooting and testing of these amplifiers should only be
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6AU6 Varieties

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I have a load of 6AU6s, NOS and used, of all flavors. This includes 6AU6, 6AU6A, 6AU6WA, and 6AU6WC. I've seen some talk on this forum of the relative faults and virtues of various brands (RCA ok, GE not so good), and wondered if there was any difference in percieved quality for the milspec WAs and WCs. I have a bunch of these, though unfortunately, they are all of the GE persuasion. The WCs are marked in green paint with JAN-6AU6WC, and etched with 6136.
 
About 2 years ago I tested a bunch (100 +) 6AU6's in triode mode. I found good ones and bad ones in every flavor. I can't find my notes from that testing. The main difference between good ones and bad ones is noise, microphonics, hum and distortion (in that order). Most of my tubes are either pulled from military spares, or NOS military bulk pack. The tube to tube variations were pretty wide. I would think that you should be able to find some good ones in a big collection of any vendors tubes (except maybe some of the early Japanese tubes).
 
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