I think one of the nicest amps that sounds really good with the S80.2's is the Beolab 5000 from way back in 1967
but any of the Beomaster 5000, 5500, 6000, 6500 and 7000 models drive these speakers pretty well IMHO !
If you have owned a lot of B&O equipment then
you will have probably noticed that these 3 Beomaster models give a slightly
disappointing sound when used with passive loudspeakers and when compared
to some of the earlier designs. This is surprising as the power
amplifier circuit is very similar to that of the Beomaster 5000 and the Beocenter 7700 (amongst many others), all of which give very satisfactory performance.
The Beomaster 5500, 6500 and 7000
have a rather basic pre-amplifier circuit compared to that used in the
original 5000 model but this is not the cause of the problems, the same
arrangement is used in the Beocenter 9000
where it seems to work pretty well. Therefore the power amplifier
circuit was investigated to see what could be causing the trouble.
The only substantial difference between the Beomaster 5000 circuit
and that used in the later models is the addition of four 220nF
capacitors C215, C216, C415 and C416. They are not shown on all the
Beomaster 5500 circuit diagrams but many sets have them. As these do
not appear in any other versions of the circuit it seemed safe to
remove them and see if the performance improved. With the capacitors in
circuit the sound from one Beomaster 5500 was lifeless, bland and
uninteresting, without them it was more similar to the 5000, engaging and
lively with a full, rich tone.
It is not clear what the purpose of these capacitors is but
performance definitely improves if they are removed. Before doing
this make sure that the muting relay 3RL1 is in good condition (contact
resistance less than 0.5R at rest) and that the output bias current for
each channel is correctly set.