Basically I have one of those bumper style Traynor
YBA-1 Bassmasters (no choke) but has cathode
follower. Originally the amp came with 4 x 40uf caps. I
immediately installed two 50 x 50 LCR caps. The amps
always sounded stiff and the treble was kind of harsh.
Well, I did some basic plexi type mods, preamp and PI
and it still had a high end harshness. Played around
with the tone stack values and slope resistor, etc., etc.
Back and forth, back and forth over a long period of
time in between messing with other amps.
 
Long story short, I got pissed off one night and changed
the 50's to all 20's and voila! No more of that cold ass,
stiff sounding amp. And, I must add, I also changed the
bias feed resistors to 220k from Traynors original 68K
(IIRC) then to 100k and finally to the 220K (that's
where it will stay - For now anyway.
 
I don't like the .002 off the lead channel preamp tube,
for my tastes it's too sterile sounding, so I used a .02
(messed with higher values with varying results) and
then into a 1 meg resistor bypassed with a .001 cap
instead of the 470K/470pf arrangement. The volume
control on this Traynor is a 500K rather than a
common 1 Meg so all of that I'm sure came into play.
Left the .02 into the PI and the .1uf's into the power
tubes, 2 x EL34's Svet's. I've played with the .02 and
.1's just mentioned but nothing helped like lower the
filter cap values and increasing the bias feed resistors. 
 
Why then does everyone (it seems) want to continually
up the values of the filter caps. I've heard one reason is
to tighten up the bass but in my case all I got was a real
punchy bass and I believe an overall harshness. BTW, I
didn't detect any hum problems. I'll get back to the amp
in the near future and give it a workout just to make
sure all is well.