[Amps] input tuning

[Roy Koeppe]

Stated:

"I'm building an amp using a pair of 4-400's in a grounded grid
configuration. I was wondering about the input tuning and what the best
way
of approaching it. I have heard of using everything from a 50 ohm
swamping
resistor to an internal auto tuner. As this amp is in the planning
stage, I
thought I'd post the question to the reflector."


The "standard thing' here is to use a pi-net mounted physically close to
the filaments. As stated by another, an operating Q of about 3 is ideal.
Some band switch pre-tuned, fixed pi-nets in and out using small relays.


Good luck,     Roy     K6XK