Fender Blues Junior excessive treble

[Chevy]

Have this beige board Blues Jr III... not too familiar with the whole series and their problems, but this one is way, way bright and sounds rather harsh in the top end. I've changed out the coupling caps to slightly larger value orange drops (ie the .002 caps have been changed to .02), beefed up the power supply cap to 100uF, to allow a little more bottom end thru; changed all the tubes, even put a 2000uF snubbing (or whatever you call it) cap across the master volume pot to kill some of the top end. Way too much top end. The schematic seems like the amp has been designed for top end reproduction. The output xformer is teeny. On the scope, it performs correctly, no oscillations apparent from below 100hz to 5 or 6 khz.
Definitely could use a beefier output xformer, it seems. Puts out the expected 15-18 watts or so.
But can't seem to find why the top end is not sweet... it's rather harsh. Can't seem to tame it. Been running Jensen P10R's at 8 ohms, and a celestion G12-65 for comparison, but can't seem to make the thing sound nice and smooth. Replaced all the tubes as well. Tried to change the slope resistor on the tone stack too, to around 60K, this fattened it up a bit, but this doesn't help with the top end harshness.
Any ideas ?

[g1]

Have you a/b'd it against any other BJ III's? It would be good to know if you are trying to repair a defective amp, or trying to modify a trebly design.
If they are all like this, the first thing to try would be a different speaker, it may make all the difference you want with no other mods required.
Otherwise, there are probably tons of mods to be found, one such here: Billm Audio » Sparkle control tames brightness on Blues Junior
I'm not sure what the 2000uf cap at the master is about, can you link any info ?

(Edit: I realize the Billm mod is a kit for sale, and am not trying to shill for them, but if you read through the comments you will get an idea of what was changed for the high end in the III and how it can be undone)

[Chevy]

I'm not sure what the 2000uf cap at the master is about, can you link any info ?

)

OOPS... pF, not uF... Many earlier Fenders used a 2000 or so pF cap across a point in the output stage to kill the top end, for oscillation control, I'm assuming.

[J M Fahey]

All amps are harsh in the bedroom, at bedroom levels and alone.
Play it loud, in a Club or rehearsal situation, with other players and specially a Drummer close by and *then* tell me whether you find it too bright or not.
Using stuff in a very different way as expected by the designer generally brings poor results.

I bet a POD , Sansamp or any PC guitar plugin sounds much better ... in the bedroom.

There´s a reason Classic amps got to be classic (no, I agree that a Blues Junior *by itself* is not, but it shares its ADN with classic Fender amps from the last 60 years) and lots of good Techs I know work on customer´s amps who afterwards claim, time and again:
- "wow!! what did you do to my amp? it sounds killer now !!!"
- "I applied the best Mod of them all ..... I removed all the silly ones and returned it to stock !!!! "
Not kidding.