See Ayre QB-9 Twenty Upgrade Announcement

Hi, I have some negative experience with the QB-9-dsd. Here is my story.
I recently bought (on the second hand market) a QB-9 DAC (upgraded by the seller to DSD status), 1 200$ CDN (~900$US), a good deal, I believe. It plays perfect, I praise its performance, native DSD and Hi Res flacs sound beyond reproach.

    B U T  

An annoying physical hum emanates from the box -- nothing in the speakers. I am fortunate to enjoy a very quiet listening room, I sometimes hear the hum (not always) from my seating position. I communicated with Ayre, they acknowledge the issue and this was their answer:

Yes, a QB-9 with your serial number has an internal transformer for Buss Power. And they do tend to hum a little. There’s not much you can do about it unfortunately.

But… we just came out with a new Twenty upgrade for the QB-9... [skipped description] ... US retail is $1,500.

So, Ayre's  proposal is to pay almost twice as much as I already paid for my unit to "upgrade" in order to settle a hum issue... At this price point, the competition is ferocious! ... and what if ... the hum remains?

Moreover, from CANADA, custom and transport issues are getting more frequent and complicated nowadays.

I rather consider to sell my unit (should get 900$US) and shop for something else supporting DSD... At 900$US + 1500$US = 2400$US, I have many many options. I currently fancy about a second hand Meitner DA-1 for this amount.

Did anyone have issues about physical hum? 

Thank you for your answers.

I did try to plug it in a few outlets but the hum persisted. I bought an Emotiva CMX-2 to eliminate DC offset, and the hum persists.

The answer I had from Ayre does not encourage me to insist for a repair:

Yes, a QB-9 with your serial number has an internal transformer for Buss Power. And they do tend to hum a little. There’s not much you can do about it unfortunately.

All they suggest is the Twenty upgrade which, with the improved audio board does not have buss power.

For the moment, I installed the unit in behind a door in a closed furniture. It dampens the noise. I now want to try to cover it with a pillow... Most of the time, however, I don't hear it from my listening position... but when I do, it's annoying... and it is frustrating to hear it everytime I approach my installation, for example when putting vinyls for audition. This particular model does not have on/off switch, and unplugging it proves fastidious in a closed furniture.

I hope the hum is not precursor of a failure soon!
Thanks again.

Thanks all for your comments. I am now quite sure that my humming transfo is defective. My issue is related to https://forum.audiogon.com/discussions/ayre-qb9-dsd-buzzThe guy from which I bought my unit had it upgraded to DSD capabilities, as in the above link.

Ayre themselves deny the issue ("...a QB-9 with your serial number has an internal transformer for Buss Power. And they do tend to hum a little...")
I will contact my local Authorized Dealer to have a check. My belief is that the hum is not "normal little hum" but rather a buzz as described in the above forum link.
In any case, thank you all for your comments that encourage me to have my unit serviced.

@hgeifman  My dealer does not offer to address my issue, but told me to contact Ayre directly.

In the mean time, I use a pillow cleverly positioned within my closed furniture shelf with total success to muffle the annoying hum. As everyone knows, a temporary workaround may well become a permanent solution especially so when really satisfactory!