Transformer Hum

I noticed a hum coming from my Hegel H200 a couple weeks ago. Hadn't noticed anything like this in the 3-4 years I've owned it. Really quiet but in a totally quiet room, audible. I've done some rewiring in the basement recently to hard wire a sump pump but that's all I could figure. Did a bunch of reading about transformer hum and also contacted Hegel who told me it was probably DC offset causing it. So I went on Amazon and bought an iFi Silent Power DC Blocker. Just received it today and placed it between my H200 and the power cable and.... noise gone. Silence. Just thought I'd add my experience to the Encyclopedia Audiolactica.