It's a real mystery. The FWB2 in a HiCap uses SMD diodes but still has the rectified output going through the wiring loom so quite a long distance to the smoothing cap compared to a minicap6, but still produces the super uplift in SQ.
My uneducated guess is that the SMD version is somehow materially different from the TO220 and the improvement is not distance related.
From Avondale web site for the FWB2 (for those who haven't read it):
"For many years, the only solid state rectifier was the common or garden silicon device with its drawbacks - high forward voltage drop, conduction losses, relatively slow recovery times, charging spikes caused when supply voltage cycle is reversed.
Along came the Schottky although initially in a low voltage form, proved to be devoid of the former negative qualities.
Continuing progress in semiconductor manufacturing has resulted in the development of higher power devices and this is one of the latest.
As you will read from many reports, the Schottky is an almost perfect rectifier when used in our beloved audio equipment - devoid of what is known as a 'minority carrier' which is characteristic in a silicon rectifier.
This means that once the alternating current reverses its direction, the current through the diode comes to halt instead of continuing to flow and producing voltage spikes as with the humble silicon device.
Speed isn't all the Schottky diode is famous for - it has a lower conductance resistance than silicon meaning lower losses between the transformer and the capacitor bank it supplies. This means reduced noise being presented to the reservoir capacitors and therefore less work for any connected regulator systems to perform in eliminating that noise.
So then, what does all this mean in musical terms?. A quieter background enabling those tiny details to be resolved bass performance enhanced without becoming smeared & bloated. Great resolution of fast transient lead and decay times improved separation of instruments even in busy tracks."
Maybe the only way to know, as Dan K suggested, is for somebody to look at the outputs of the three different types on a scope. Probably not many here with the kit to carry out this test.
avondaleaudio.com
