[Elecraft] KPA Cooling Fan Whine

[Trail Fox]

Recently obtained a new headphone, the Kenwood HS-5.  this phone has a communications range, 150-4000 ohm, and that is a good thing; no hiss, no bass.  It is extremely sensitive, so much so that one must turn the AF gain way down, to in the order of 8 o'clock, and one must reduce the sidetone to 003.

However, when the KAP cooling fan came on, with it arrived a nasty whine in the headfones, perhaps a very unclean 600-700 cycles.

I put my other headfones on the radio, turned the gain back up, and when the fan came on, indeed no discernable whine.

Thoughts on getting rid of the whine besides not using those headphones???

72,  Fred kt5x
K2 # 0700