Because they simply tend to 'UNBURN-IN'and that is logical..Next time find out for yourself when you buy a pair of new amps!! Run a varied signal through one of
them for 48 hours-no more needed. Then listen to it in
mono-carefully. Do not rush. Then listen to the unplayed one for comparison-in mono. Now unhook the first one and
place it in another room for 2 weeks. It will not sound
as good as it did before and not as good as the second
one you had been playing for 2 weeks. It is changed=
UN-Burned-in!
them for 48 hours-no more needed. Then listen to it in
mono-carefully. Do not rush. Then listen to the unplayed one for comparison-in mono. Now unhook the first one and
place it in another room for 2 weeks. It will not sound
as good as it did before and not as good as the second
one you had been playing for 2 weeks. It is changed=
UN-Burned-in!