Both radios go quiet - oh no!

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   I'm posting this in the Audio Panel space because it's the only hardware common to both radios.  Read my story and let me know if I need to call for an exorcism.

I have an Avidyne 540
 for a #1 comm and a KY-97 for a #2 comm.  Both are connected through 
the Avidyne 240 audio panel but as far as I'm currently aware that's the
 only common element in the radios.
I was 
flying about 1000 nm last week (yes, home from OSH) and at least half a 
dozen times I lost the ability to hear incoming comm on BOTH radios!  It
 happened while with Chicago center, Minneapolis center, Kansas City 
center, and Fort Worth center; I don't think there were all having
transmission issues on the same day.  Here's what I know -

1.
 All would be quiet and I would get an urgent call from either center or
 another airplane center had pressed into service to help contact me.  
When I would answer I could always hear fine and the transmissions from 
other aircraft and center with both strong and clear.

2.
 Other times it was the reverse, things would be quiet and I would key 
up for a radio check.  Two or three calls later I would hear the 
response and they would always tell me they heard every request and 
responded each time.  I only heard after several responses.

3. I switched to my backup radio and had the same thing happen!

4.
 At one point I turned an ATIS freq that was nearby and monitored.  
Things were fine for a while and then the transmission stopped.  The RX 
indicator on the 540 was not lit.  When ATIS was again audible it was 
the same broadcast as before.  The time was not the appropriate time for
 a change to ATIS.

5. While I do not believe my
 airplane was hit by lightening, it was parked in the North 40 at OSH 
all during the week and there were a few strong storms that passed near 
the area.  Heavy rain and strong winds were common and a few rumbles of 
thunder.  I don't camp at the airplane so I wouldn't know how it was at 
that exact spot during the storms.

As far 
as I know now there are no common parts between the radios other than 
the 240 audio panel.  However, that should not inhibit the RX light on 
the 540 even if it blocked the audio from coming through.  Also, my with
 was with me and we could always talk to each other - which was easy in 
times of silent radios!

Lastly, being a long 
trip I brought an MP3 player and plugged it in through a music input 
jack through the 540.  The music never stopped playing (I pressed the 
'music' button on the 240 so the music doesn't mute during radio 
transmissions) so I know there wasn't a loss of all sound.

My
 avionics guy who installed all the systems is stumped.  Does anyone 
have any idea that could explain everything?  At this time I'm willing 
to entertain advice from other pilots, avionics professionals, and any 
witch doctors who may be able to cast the appropriate spell to cure my 
ailing airplane!

Edited by M20Kid - 06 Aug 2018 at 8:22pm