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John wrote in message
news:BJ6dnX5CzPSozH7YnZ2dnUVZ_tSunZ2d@prairiewave. com...
I used a hammond 1645 output transformer (30w 5000ohm plate to plate) my B+
around 320
VDC.
I built mine like the 1956 RCA manual (page 276) with a few execptions:
my power transformer was a 240AC full wave bridge rectified by 6A10. I
used two 193d
inductors (hammond 8H@150mA )and four 33uf 630v poly caps (solen) and .1
uf on the end of
the power supply. I use a 5vdc industral switcher tweaked to 6Vdc for the
heaters. I split chasis
my amp the power supply is on one chassis and the amp on another. This
lets me tweak the
power supply separately from the amp and it helps with controlling the
magnetic noise the
power supply emits . I use jones connectors for my power interconnects.
In most of the tube push pull amp the output stage acts really like a
buffer, the voltage gain is
happening before it in the tube predriver stage before the pase split . In
the 6as7's case,
needs a really high impedence input with about 60-80% of what signal you
want the output
comming out of it. and the grid loading the 6as7 reflected back to the
phase splitter should be
isolated by some type of balanced driver stage. And last, it needs the
medium-low
impedence load of 2500 ohms per plate to establish the idle current
without causing
transformer saturation. I go about 2-3 times over on power rating of the
output transformer to the
circuit to achieve low transformer saturation and better bandwidth. its
about 12 watts of amp.

I was going to expirament with using a signal transformer 600:50k ct
(sowter 9062) grounded
center tap sec. and two stages of john brooskie's akido per signal path
(one two tube 6sn7 for
the signal + and one two tube 6sn7 for signal - ) as a balanced amp.
Otherwise, to cut parts
count down, a simple 6sn7 or 6sl7 common cathode will fit the bill. If you
dont have any of those
octals try 12ax7, 12ay7, 12au7 9 pins.

this is the link to RCA amp above:
http://www.kbapps.com/audio/tubemanual/276.html


How do you like the sound of this amp??? I think it would be a good
candidate
for a CT choke loaded driver to get low distortion AF voltage swing at the
6AS7 grids.
you might look into John Stewarts "Bootstrap" 6AS7 amp.....There are alot
of
these regulator tubes to be had at cheap prices...GC