DAC repair/troubleshooting in New England


I purchased a DAC in Taiwan quite a few years ago. It’s a dual TDA1541A, with a tube output stage. Really nice construction and components. Pictures are linked below. 
It’s always had a significant hum. I love this DAC and would really like to get rid of the hum, but not savvy enough troubleshoot myself. 
Anyone know a good place within reasonable driving distance from Central CT that would be capable of this?

TIA. 
https://1drv.ms/u/s!ApgbD0vl_2nriWL64o6D3xbWDvWx

https://1drv.ms/u/s!ApgbD0vl_2nriWGrauFki7P_o_9G


jabar102
Hum is definitely there with no inputs connected. I usually use the optical. 
Try just unplugging the input cable you are using with the unit on and off. Does the hum go away? 
It does not have a USB input, just optical, coax and balanced. 
The hum does sound like a 60hz ground loop, or at least I think it does. 
Is there a usb input? Are you using it? If so, I will suggest something that may eliminate it. I am assuming you are referring to a hum through the speakers? The woofers? Like a ground loop 60 htz hummmmm.....