[Elizabeth]

Place a steel panel under the tuner shelf. Connect it to 'ground' like a real AC plug ground and plug it into the AC duplex to 'suck up' the RFI spew. YOU could use black antistatic foam (also grounded same way) too. Just that is a little harder to find laying around. You could even lay the metal plate under your Tuner.. still grounded. (being grounded is KEY, and NOT to the chassis of any electrical equipment!) Even a sheet of aluminum foil may be enough.(again if it is grounded properly).. But I wouldn't bet on it.
It will solve the problem.

[dB Cooper]

Turn the DAC off when listening to FM.

[ohenry]

Buy an F-ing turntable... and get off my grass. 

[RickB]

I recently saw this in a customer's system using a Canary CD player beneath a MagnumDynalab tuner...turn on the CD player and FM was wiped out...replaced the Canary with a Teac and the noise blanking went away...