71 superlead differ from a 68
         plexi?
There really isn't any significant difference other than
the OT and on the early Plexi's you'll find 32uf power
supply caps, which by itself won't really make much of
a difference in tone. I see alot of people recommending
the .68uf bypass cap on the second gain stage, but I
honestly can't remember ever seeing one on an amp
built before '69. Splitting the cathodes doesn't make a
whole lot of difference. The volume pot on alot of '72
amps and later was almost a linera tapre which causes
the amp to go from no volume to raging distortion very
early in the knob rotation. If you want early
Plexi-Specs....put the cathodes in the first stage together
with an 820 ohm resistor and a 250uf cap......change
the tone stacke to 56K slope and a 250pf treble cap.
Change the output coupling to .1uf. Remove the .68uf
bypass cap on the second gain stage. Use a 500pf
bypass cap on the bright channel summing resistor and
a 500pf bright cap on the volume pot and change the
power supply caps to 32uf. Power supply caps are
definately optional because it really won't make much
tonal difference.....mostly a difference in feel with the
bottom being a little squishier with the 32uf caps. For
later Plex.....'69......keep the early seventies setup. If
you want the amp to sound as good as a
Plexi......replace the OT. OEI will have a 100 watter
out soon and I'd recommend waiting for it to come out.
That's all there is and there isn't anymore.......the really
big difference is going to be in replacing the OT.

Peter 

Peter is pretty much dead on. The 68-69's did
have the .68uF cap across V2A's cathode and so do all
the point to point Marshalls up to 73. In 73 they
converted to PCB's and removed the .68uF bypass
from V2A.

The 32uF caps do make a difference and while the
50uF caps give a bit more low-end I think the 32uF's
sound a little more "open" over all. It's hard to explain
but if you try it you'll hear what Peter and I are talking
about.

The output transformer is where A LOT of the
mystery, myth, and legend comes into play. The whole
Aluminum verses steel chassis debate is not as relevant
(in my humble opinion) as opposed to the differences in
OT's. OEI's is the best plexi replacement OT out there
HANDS DOWN!! (no I don't own stock in OEI..not
yet!!! ha, ha)

Trace 

My hunch is that Reb would replace with 100k plate
resistors.

Winnie