Hello,
Sorry if I used the term High frequency DC out of context. I don't consider myself an electronics authority and I was attempting to interpet the explanation of a similair problem that I had.
Just to clarify, I had a problem with a phono stage that caused very unusual problems with my system that had baffled the manufacturer and was the most frustrating audio situation that I ever encountered.
The phono stage, a BAT P5, connected to a BAY VK 30se, caused the power tubes (KT-88) in my amp to light up. I didn't even play a recording and this would occur. I then used a solid state amp and instead of the amp reacting, the problem manifested itself in my speakers where the mid range drivers extended way out then retracted as Tooter has experienced. Note that the woofers didn't move.
I was told that it must be the amp, the tubes, the interconnects, the power conditioner etc.. I checked everything but the problem kepted happenning. At the time, BAT didn't believe that the problem was coming from the P5, so I sent the P5 to a 3rd party & they said the there was an excessive DC leak out of the P5 and they called BAT to convince them. Additionally, I was told that since only the mid range drivers reacted and that no sound was heard lent itself to a frequency that was inaudible.
Anyhow, a DC filter was put on the P5 and the problem was solved. BAT had never seen anything like this at the time, which was 2 years ago.
Fortunatly, Tooter is getting a replacement and hopefully this will be a happy ending.
Steve
