Specifications

EFB™ is simply a way to achieve virtually all of what regulated power supply operation has to offer with regards to distortion
reduction, with the possibility of correcting other ills along the way as necessary.
In the ST-70, EFB™ would not add extended tube life to speak of, as the operation of the output tubes is already quite
conservative to begin with. It cannot be used to correct for original design ills in the output stage, because they basically don't
exist. It can reduce distortion some, and heat dissipation some, but the distortion levels of the original design -- even with both
channels driven -- is still quite low, and low enough to suggest that EFB™ would not really provide any sonic improvement to
speak of. That leaves reducing heat dissipation levels, which would be reduced more by eliminating the rectifier tube.
I'm hardly trying to trash my own product! But in this case, the ST-70 was so well designed as to benefit only marginally from the
concept.
Those new to an ST-70 then owe it to themselves to first properly restore it to its original configuration, and then listen to it
carefully for an extended period of time. Then, if you are looking for a different kind of sound, so be it. But at least find out what
caused it to outsell everything else by such a remarkable amount to begin with!
13