I get this as well in my Mk2 have not tryed the Mk2a but it is not a problem for me as i never actually use the aux input but i get radio bleeding into it.

i will try the Mk2a later once i have upgraded it to 3.0 and it has stopped raining (scotland could be a long time)
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P.Allison fixer of big engines Mk2+Mk2a signed by God / Hacked by the Lord Aberdeen Scotland