I just got a Little Dot MK III and it's about 30 hours into the burn in. I noticed when I got it that the two small driver tubes had a bit of a ringing sound that comes through the headphones when I tapped on them with my fingernail. It's not a sustained ringing. I tried a couple replacements for the 5654's and it's the same deal. The amp is sounding good and it's hard to imagine that four 5654's could all be microphonic. The power tubes don't emitt this same sound.
Is it just the nature of the driver tubes to do this?
