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SET amps and biasing 300B's; expert advice needed

Another tube biasing thread, sorry for that. I'm driving my Audion SET amp with a pair of EAT 300B's and am perfectly happy with them. Yet, this hobby being the never-ending money squandering activity it is, I felt the itch to try a couple of Shuguang black bottles, used - but alledgedly with far less than 100 hours - and therefore offered cheap enough to give them a go. What held me from it was the drag of having to re-bias every time I would change tubes. The dealer tried to convince me, not of importance with SET amps as long as I use matched pairs. That flies in the face of what I've been reading so far. At the very least, I would think, the tubes would have to show similar specs (in this case, it would seem both abide by the original WE 300B specs). Tube guys, please advise, was he just trying to find a dummy to get rid of the tubes or is there (some) truth in this?
karelfd

Showing 2 responses by swampwalker

swampwalker's avatar
swampwalker
5,138 posts
 
From what I can gather from a quick web search, the current crop of Audion integrated/amps are auto-bias of some sort.
"The Audion 300B single-ended amplifiers employ pure Class-A circuitry from the input to the output, with two voltage gain stages culminating in a high dynamic driver circuit driving a Super Linear (1) output stage that operates with auto-bias."

It's stated explicitly at the end of the manual:
" No other voltage adjustments will be necessary but the valves should be replaced as matched pairs."

I'd check w Audion tech support to be sure. The amps either have a bias pot somewhere or have some sort of auto-biasing functionality.
swampwalker's avatar
swampwalker
5,138 posts
 
Kerlfd- NP. If it looks "remarkably like" and has similar name, I would not be surprised to find out that there is a "common ancestor". None of my business and I think you probably made a good call on the tubes, but it wouldn't hurt to contact Audion UK and see if the products are related and if they can answer your biasing question. 'Nuf said. Good luck.
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