by EWBrown » Fri Jan 18, 2008 7:19 am
I notice the big differences between these designs and the "hifi" amps, is small interstage coupling caps, no NFB, lower B+ (around 325V) and use of a a 130 ohm cathode resistor for the pair of 6BQ5s, which harks back to the 1950-1960s tube manual data. The tube combinations seem to be 12AX7 / ECC83 and 6BQ5 / EL84 almost exclusively.
I posted an article over at 18W about the use of "non standard" tubes like 6GK6 and the various siblings, like 8BQ5, 10BQ5, 10GK6, 16GK6 and the alleged 29GK6. I dunno just how much "18 Watters" tend to experiment, or if they prefer to stick to tried and proven designs.
/ed B in NH
Real Radios Glow in the Dark