osc-->buffer-->cathodyne PI--->Mixer-->out
 
the wave is a peaky sine. (and probably asym as well..)
The PI splits the signal (duh), and then applies two filters to it (0ne
to each signal) then these two eq'd and out of phase signals get
mixed in a non-linear fasion in that mixer. There is a good bit of
LFO junk coming out of the mixer, but since there is not that much
amplification going on the artifacts don't require a HPF (as in the 3
stage one employed by the AC30). What you get is a lovely
"whoosh whoosh" kinda trem - not that big on intensity, but huge
on phase-filtering.. your univibe kinda action. It's a bear to build
for sure.. I actually did a resto of a Brown Concert (one of my first
ground ups..) for a buddy at the custom shop and that is the
toughest amp to build.. I have no idea how Fender made them on
an assembly line. There's also a mistake in the factory schem
(compare it to the layout.. the layout is right if memory serves..) 
If you look at the non-"A" version (i.e. Super 6G4) you'll see that
the harmonic split is accomplished without the cathodyne splitter. I
haven't heard the difference between the two, I would imagine that
the earlier version has a bit less oomph. 

As for the unused half of the tremolo splitter, I'm going to use it as
the gain stage into the trem section and put the two stages of the
first preamp tube in parallel.

Check the Intesity pot value. 10 MEG! REVERSE AUDIO taper!
Where the hell can I get these? The largest value I can find is 3
meg RA or 5 meg linear. 

If anyone has any idea where I can find the 10meg RA or suggest
a suitable alternative please reply here or email me directly.
Thanks.
Don't sweat the reverse audio thing. That's just so "10" on the dial
is faster than "1". If you build your own and use a different taper,
the knob numbers just won't correlate intuitively. 

If 10 meg pot is hard to come by, as will be the 4meg intensity
control, you could use a lower value pot and switch resistors
ahead of /behind the pot to change discrete "ranges". The pot
would vary the effects over limited ranges, and provide for a finer
adjustment. It would involve maybe rotary selector switches, but
what a nice touch to a custom amp with primo tremelo effects! 

 One trick is to have a microphonic tube in the trem circuit. The sympatheic vibration from the chassis gives it more depth and phase cancels out all of its honkiness. 
 
somthin' else

I don't know about the Magnatone vibe, but I don't know why
you couldn't do it.

One thing I've been trying to work out is a way to incorporate
BOTH the harmonic trem and the bias trem using the same
oscillator. I'm not sure if this would be overkill but it seems like it
would be pretty cool to have the univibey thing going on as well
as the woomph woomph pulsing trem. I was thinking this would
be like having "width" and "depth" controls.

I need to be able to change the polarity of the harmonic trem so
that the either the treble or bass leg could coincide with the peak
of the bias trem wave. Otherwise the "depth" would only affect
the highs or lows of the harmonic trem. Super fancy would be to
add a phase delay to the bias trem. I have no idea how the hell I
would do that. 

Caps
  In any case, I believe that the stronger and bassier signal
passed through the mica cap may have contributed to the
harsher sound you mentioned (as the extra low frequencies
may have caused the subsequent stages to overdistort).
With a ceramic cap of the same value (as measured by my
"El Cheapo" Radio Shack DMM) the signal is softer and
grainier- sort of like smearing Vaseline over the lens of
your camera when you are taking pictures of your..., uh,
dog.

Bass Master
I will just point out a couple of things about my Bassmaster
as I received it. The volume pots are 500k. The first
preamp has independent cathode resistor and caps. It has
a cathode follower. It has EL-34's (actually came with
6CA7's). The treble cap is a .001. The guitar channel's
volume pot has a .001 cap. Bass cap is .1uf, mid is .02uf.
PI has 47K grid resistors, power tube grid has 68K
resistors. There is no choke. There are no 4 meg pots.

I've been messing with different values of caps and also
reworked the PI (replaced the 47K's to 1 meg, etc). Tried
increasing the grid resistor on the power tubes to 220K but
brought it down to 100K. First preamp now has a 2.5K
resistor with .68uf cap. The second stage has the 820 ohm
with a .68uf cap. The treble cap is a 500pf, bass cap
.022uf, mid cap .022 uf. Off the plate of the first tube is a
.022uf cap through a 220K resistor bypassed with a 500pf
cap. The typical 470K/500pf combo was a little harsh to
my ears. The 220K/500pf combo sounds a little smoother.
Also I don't have a bypass cap on the volume control. I
changed the 47K slope resistor to 33k for the best balance
yet. (maybe switching to a closed back speaker I will have
to do some adjustments, don't know yet. Got any
feedback on that?)

I had posted about three months ago that I was tweaking
this amp and that the bottom was thumpy and maybe the
top was harsh. I found the slope resistor plays a bigger part
than I realized in the overall tonal balance. Also, I don't like
the tone of a smaller coupling cap (i.e., .002) off the first
stage. (that snaller cap made it appear to have a thumpy
bass also-I prefer a little lower frequency to come through
for a softer bottom). 

I may consider installing a large cap off the cathode feeding
the tone stack and then using a pot to adjust the slope. I
have gone from 22K all the way up to (don't laugh, ha,ha)
1 meg. Well, actually I've spent so many hours of changing
caps and a couple of resistors back and forth that it was
down right disgusting at times. Instead of being relaxed and
enjoying this hobby of mine, I would get frustrated and
even get some anxiety over not getting it right. Currently it
sounds pretty good. Of course that was a couple of nights
ago, hope I still like it next time I crank it up. We'll see. 

Lastly, I reduced the caps going to the power tubes to
.022 but later changed them to .1uf. (seemed like the
.022's chopped off the bottom). Now in all fairness I'm
playing with a Gibson Les Paul Deluxe with those stock
mini humbuckers. So it may sound heavier with my ES 335
with Duncan Alnico Pro bridge and stock neck pick ups. I
may have to compromise somewhere in the amp or just set
it for one guitar mainly. Haven't tried my strat yet. 
STOCK FENDER
After some quick voltage measurments I realized that the plate
voltages on the vibrato 12AX7 were running a little higher than
others I had worked on or voltages I had seen listed on some
Fender schematics. This led me to double check all the
resistors in the circuit one more time.......bingo! There was a
100k cathode resistor installed on the second triode instead of
a 56K. I installed the 56K resistor and the depth was then
back to normal on the vibrato.........which got me thinking!
Hey.... what would a 47K resistor do there.......Bingo......A
nice rich vibrato depth that is better than the stock sound and
a now I'm a happy tech!.......

Hmm. Well, I built mine from the ground up, so I'm not real sure what the common failure scenario is like. I guess my semi-knee jerk response would be to replace the electrolytic bypass caps of the oscillator and mixer sections, and replace the tubes.

What is the pumping you're refering to? I definitely can tell when the trem is on, but I hear it more from the slight HF hiss pulsing in and out.

I did notice that the .1 caps to ground just before the phase splitter will have a very drastic effect on the pulse. I played around with different values, and think I settled on .1 and .05 but I don't recall which went where.