I recently purchased a "HAMMOND H-AO-40-1FIELD COIL AMPLIFIER" from ebay. The tubes are: eight 6V6's, two 6SN7's an two- 5U4G's! So it appears (I have not recieved the amp yet) that there are two completely seperate (dedicated rectifier and power supplies) channels on the amp. The seller states that the amp has been tested and works "perfectly". It appears to be circa 1940-1960 era. I was wondering if anyone has had any experience with, or information about, field coil amplifiers? Is this a type of push-pull topology? Any info is appreciated as I could not find anything on the forum or on the web. Cheers. Dylan.