OPT and IT for SV811 SET amp

Design and use of the various types.
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bigfunhorns
Posts: 10
Joined: Thu Aug 23, 2012 3:33 am
Location: New Zealand

OPT and IT for SV811 SET amp

Post by bigfunhorns »

Long story having tried a variety of driver and DHT power tubes. I'm now using a 2 stage SET with a triode-wired, grid battery biased, C3M with a Dave Slagle 49% nickel IT driving a Svetlana SV 811-10 DHT also grid battery biased ( to operate in class A1).
I'm looking at building a new pair of, larger, monoblock chasis to
enable me to increase the SV811-10 B+ to around 700 V dc.
I've experimented with 'filament bias' on the SV811s and will
incorporate this too.
I'm not sure if my current '300B' output transformers will take the
proposed B+
I'm after a pair of output transformers for the SV 811-10s.
Operating conditions would be 700v dc B+ and around 75 mA plate current.
The tube plate resistance is a highish 2500 ohms and Svetlana's recommended plate 'load' is 5K. I've seen higher OPT primary Z suggested
but my present 5K amorphous nickel OPT sounds about right.
I'd also like to try some of my Raytheon 5842s as driver tubes.
They have twice the mu of the C3M so I could look at a 2:1 step down IT.
Is that a worth while step?
Any suggestions or questions are welcome, Kevin
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