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K&K Audio / Lundahl Transformers

What do you think of this - LL1676/Aurora variation

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Allo,
I'm looking to put together a direct drive ESL amp which is something of a mutant offspring of Allen Wright's and Lynn's amps...
Output stage will be 4212 triodes in PP with CT choke load (possibly air-core at some point) direct coupled to ESL panels. Driver undecided as yet but will involved diff pairs, possibly loaded with Gary Pimm's CCSs (with high value shunt resistors to equalise the anode loads).
The whole amp will be floated so the B+ is at ground. This will mean that the input is at about -2.4kV. So I need someway of isolating that from my source components which will be at 0V.
Now looking at the spec for the 1676, I see it offers 3kV isolation between pri and sec, and 1.5kv between either winding and the es screen. Considering biasing the screen at the midpoint of the main amp HT, ie 1.2kV via a resistive divider. Per Lundahl reckoned this would be ok; I since had the idea of including a large resistor eg 20M in line with the screen to limit the current should anything go wrong.
I know this is technically within spec, but the LL1676 is a cute (ie little) thing and I feel it may be a tad insane.
What do you fellas think?
Best,
Chris

Follow Ups:

Re: What do you think of this - LL1676/Aurora variation - KevinC 07:23:44 09/24/03 (4)
Chris,
I'm with you on the cautious side. The L1676 would work based on ratings, but there should be another level of isolation to provide a back-up. At the moment, other than capacitors,which aren't particularly elegant in concept, I am at a loss to suggest something that is elegant.

Kevin Carter
K&K Audio
www.kandkaudio.com
- Re: What do you think of this - LL1676/Aurora variation - vry 07:44:48 09/24/03 (3)
  Thanks Kevin,
  Maybe best bet would be a custom interstage between driver and output; I have a Sowter that has this feature but it's 1:2 and I really need 1:1 (blasted 4212 Miller capacitance).
  But I doubt there's many that would match the performance of the LL1676, hence my thoughts.
  Still, no point frying everything upstream, or indeed, anyone listening.
  cheers
  - correction to above note - vry 08:36:16 09/24/03 (2)
    The "feature" of the 1:2 interstage was that it was explicitly spec'd for a few kV isolation between primary and secondary...
    - LL1660S - KevinC 08:49:02 09/24/03 (1)
      More than the 4kV between pri and sec and 2kV between either and the core?
      
      Kevin Carter
      K&K Audio
      www.kandkaudio.com
      - Re: LL1660S - vry 09:32:55 09/24/03 (0)
        
        In Reply to: LL1660S posted by KevinC on September 24, 2003 at 08:49:02:
        
        Hi Kevin,
        LL1660S looks like it would work fine, but I'm a big fan of the high perm cores (the 1:2 i/s was a custom job with combination core, 50% m6/mumetal).
        Now if Per could do an amorphous LL1660S...
        Best,
        Chris

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