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In Reply to: RE: Nope posted by danlaudionut on May 24, 2012 at 19:13:06
This must be an older model!
I am thinking of building a one with KT120s
and the Lundahl LL1620CFB good for 20W in UL.
Maybe a 6GK5 for a driver.
I don't think those LL1620 OPT's will have UL.. I bought some used SE 50 mA LL1663 thinking they would have it , but no. They may not make any SE OPT'S with UL.
They all do if you want to use 50% UL since
they have 2 or 4 equal primary windings.
(1663 has 2 primaries so 5/11 pins are UL tap)
BUT the LL1620 splits one pair of primaries
with half going for the Cathode Feedback
so you are left with 2 "normal" windings
and 2 half windings so you can wire it
as 33%, 50% or 66% UL if you want.
With 2 CFB windings that can be wired
in parallel for 25% CFB
OR in series for 50% CFB.
BTW The LL1620 is not a stock item
so a special order is necesary.
And they normally are PP (see link) so a
LL1620CFB gapped for SE is even more so.
I bet you could get Edcor to wind a 20 watt output transformer with an 8 ohm speaker winding and a 64 ohm cathode feedback winding.
BTW - you can get 20 watts out of a 6550 single ended pentode, I'd imagine the KT120 could net a little more!
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