MSD Tach Apapter 8920 noise question?

[chargerbr549]

I installed an MSD 6520 ignition box on my 69 Charger which seems to work great but my old Sun Super Tach II wouldn't work the MSD box so I ended up buying a MSD 8920 Tach adapter and now the tach works like its suppose to but now I have an ignition buzzing noise coming out of the tach adapter if I turn the radio on it gets really an annoying buzzing through the speakers, if I unplug the tach adapter from the ignition box the noise goes away, is this normal? I also made sure it was wired correctly and all my grounding looks good, I have it mounted in my glove box area by the ignition box but I don't know if that would make a difference, I might end up buying a tach thats compatable with the box. I don't really want to back to the factory orange box since the MSD cleared up some of the problems I was having with factory box plus I got an adjustable rev limiter to boot.

Kevin

[A383Wing]

mine don't buzz.....just sayin'