Hi,
Some time back I modified Daniel Martin's AC15H1TV to give
the original Mk3 Bright switching circuit removing the "Improvements"
in this area, while I was doing this which was at the Derby club, Daniel was using
the old '62 AC15 and when I finished the mods I re-connected the amp in place of the
AC15 and Daniel was impressed that it sounded much the same as the AC15.
On or two people in the club remarked how good it sounded..
Why Vox didn't just leave the original AC15 circuit alone I don't know!!
As to the ECC82 in the Circuit 3 AC15's it's used as the modulator for
vibrato and trem along with an ECC83 which is the vib / trem oscillator,
Most of the components on the lower tagboard of the amp are for Vib / Trem!!