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G6Tanuki · 19th Aug 2019, 5:56 pm

Fascinating that the McIntosh amps used a set of push-pull-parallel 6LQ6 TV "sweep tubes" rather than a couple of big 813-style ones.

Was this perhaps cheaper? Or possibly a nod towards reliability - with four tubes in each half of the push-pull setup you could lose one tube and things would continue (with a bit more distortion) until the end of the set.

(lots of parallel tubes also mean you can trade lower HT volts against higher HT current - 500V at an amp or so is more open-air-rainy-venue-friendly than 2KV at 250mA)

19th Aug 2019, 5:56 pm	#3
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,996	Re: Woodstock PA system.... Fascinating that the McIntosh amps used a set of push-pull-parallel 6LQ6 TV "sweep tubes" rather than a couple of big 813-style ones. Was this perhaps cheaper? Or possibly a nod towards reliability - with four tubes in each half of the push-pull setup you could lose one tube and things would continue (with a bit more distortion) until the end of the set. (lots of parallel tubes also mean you can trade lower HT volts against higher HT current - 500V at an amp or so is more open-air-rainy-venue-friendly than 2KV at 250mA)