A few days ago a customer asked me about using the Eminence
820H speaker in the Memphis Mini amp. I
tried that speaker long ago and considered offering it as a substitute speaker
but I had to reject it: The 820H comes
only as a 4 ohm speaker and the MM amp expects to see an 8 ohm load at the
speaker tap. This would cause the amp to
run hot, leading to transformer failure.
Nobody likes to see smoke coming out of the back of his amp.
Any amp based on the Classic 5 platform will have the same
problem unless the builder has gone to the considerable trouble and expense of
swapping out the OT to accommodate the 4 ohm speaker. Even worse, if you are running a 6L6 power
tube along with the 4 ohm speaker you are likely to burn the power
transformer.
We have hundreds of Memphis Mini amps in use, many for up to
two years on stage. We know what works
and what doesn’t. A well-designed vintage-style
tube amp is a Rube Goldberg contraption of moving sonic parts that work
together to produce a wonderful tone. It
can be a delicate balance. Ask your amp
maker before using a lower impedance speaker or bigger power tube. It could fry your amp.
