Halo A51 transformer hum...Need power conditioner?

Hi,

I recently purchased the Parasound Halo A51, and I am getting a hum from the transformer. The hum comes directly from the A51 unit and not through the speaker (it's not a ground loop problem). I send the A51 back to Parasound for repair and they replaced the transformer.

I just got the A51 back today, and the hum was reduced to a barely audible buzz. However, when I started using the microwave, the hum came back again. The hum disappeared when the microwave turned off. I live in a 30+ years old house, and so I think the power going to the A51 may not be clean.

I don't want to spend too much money on a power conditioner...maybe $200 or so. What kind of power conditioner will solve this A51 transformer hum? The PS Audio has a product called Humbuster AC. Would this Humbuster help me or do I need some other product?Below is a link to PS Audio website:
http://www.psaudio.com/products/humbusterac.asp

Thanks in advance for everyone's suggestions.

jeweltone