The hum level of the power
section is zero. The pre is
picking hum (interference)
but it's not from the power
supply. It's a specific wire
that I have already located
that's working as an
antenna. 

Your hybrid rectifier works
nicely. There's a subtle
compression if you let the
power stage overdrive,
very touch responsive. The
problem is it is hard to
keep the pre from distorting
before the output, it has so
much gain. With a 5Y3 and
a pair of 6V6s biased in
class A I can get great tone
and response with a
reasonable volume. The
triode mode is a bit dark
and the drop in output is not
that much. By the way, even
with only one pair of tubes
and a low B+ (~270 V with
a 5Y3) the amp is really
LOUD in pentode, class
AB operation. 

I'm running the preamp
from the tube rectifier also. 

SS-5Y3-CAP1(50u)-choke-CAP2(50u)-1K-CAP3(100u)-4k3-CAP4(100u)-2k7-CAP5(100u)

Plates are fed from CAP1,
grid2 from CAP2, PI and
loop drive/recovery from
CAP3, pre from CAP4 and
the input extra stage for
lead from CAP5. There's
more capacitance than
usual for a 5Y3 but both
halves are in // so I hope it
won't burn. Each half is
conducting 1/2 current but
is also firing at twice the
frequency, so average
power is equal. But I think
the greatest problem is not
average power, but peak
current. 

With a GZ34 I have less
sag but it still has a
different dynamic than all
SS. 

I'll try feeding the pre from
the SS rectifier to see if I
can get more headroom in
the pre and still have a
responsive power section. I
haven't thought of it - it's a
very versatile configuration
you came across. 

I also read a suggestion
here in AMPAGE about a
hybrid brige rectifier that
uses a tube to rectify B+
and 2 1n4007s to ground.
Very interesting. If I used
this I could get more power
(my trannies can handle it)
but I would have to use
filter caps with a higher
voltage rating, or use caps
in series... I won't do it,
there's enough holes per
square inch in my amp and I
think it is loud enough as it
is, but this idea coupled
with yours can be a
reasonable way to add a
tube rectifier to many amps
that weren't supposed to
have one. 

GFR

You could run a single SS
diode in series with the
decoupling resistor
between CAP2 and CAP3.
This way, the preamp
supply voltage won't sag
when the power amp/PI
does. It's a one way valve,
allowing C3 & C4 to be
charged, but prevents their
being drained back. 

From your description it
sounds like it's gonna turn
out to be a great amp. Are
you planning on putting it in
a combo cabinet, or
building it as a head? 

Doc

I've changed it like this: 

SS-5Y3-CAP1(50u)-choke-CAP2
  | 
   -5k6-CAP3(100u)-4k3-CAP4-2k7-CAP5 

Will add a diode in series
with the 5k6. 

My initial idea was to build
it as a combo. I have a big
100W head (Fender copy)
with a bigger than usual
4x12 cabinet (head+cabinet
is 1.20m tall), and a tiny
Washburn VGA-15. I
wanted something that
would fill the gap between
them, portable yet
reasonably loud. 

After some tests in the
bench I gave up this idea. I
had to select tubes in order
to avoid microphonics and
I feel that I would have
trouble with vibration in a
combo. 

I think I'll go with a head
and a small closed back
1x12. Perhaps I'll add some
way to "clamp" the head to
the cabinet so it's easier to
carry. 

The "clean" channel is
really great. I can go from
blackface brightness to
AC/DC crunch reaaly well.
Messing with the gain and
master I can balance pre
and output distortion to get
a really nice touch. The
"triode" mode in the output
section makes the clean
sounds too muddy, but
when the output is
overdriven it adds a nice
midrange emphasis (read
"brown sound" here). 

I wasn't able to get a decent
sound from the "lead"
channel yet. It has a
ridiculous amount of gain.
EQ in FX loop is certainly
a must, but I haven't had the
time to play with it. 

When I arrive at a final
configuration I'll post the
schematic in "Plate to
Plate". 

GFR

GFR did you try 

ss-coil-lots of capacitance-5y3-poweramp

| preamp 

You also might want to
build a slow start circuit to
cut down the surge in the
solid state rectifer. 
gus