NAD C-388 w/BluOS2i WiFi Connectivity


I have a NAD C-388 w/BluOS2i (and HDM-2) MDC cards. It has worked very well for several years.
Later, I purchased a Node2i. They are both in my 2-ch music listening/concert watching system. Typically use PC, tablet, or Note phone to control the C-388 using BluOS app to stream AmazonPrimeMusicHD.

Between C-388 and Node2i, I prefer to use the C-388 because it is more direct connection, since the Node2i is connected to Coax1 input of the C-388. However, the C-388 seems to drop the WiFi connection after 5-10 minutes of play. My solution has been to switch to the Node2i - which has always been rock-solid connection.

Investigating this issue, I've found that the Node2i is always connected on 5GHz (never fails), while the C-388 is always connected on 2.5GHz. Home network is all Asus mesh, with AC3100 (master) and three AC1900 (nodes) spread throughout the house and to cover an acre of property (for IEM noise-blocking + tunes while mowing).

Question is about the C-388 WiFi being 'stuck' in 2.5GHz. Seems I need to move it to the more robust 5GHz.

Anyone know if this is possible and how to do that? Is it a C-388 setting or BluOS2i setting? 
128x128mwatsme
BTW, replacing the supplied Unex DNUA-93F (WiFi dongle that comes with BluOS2i MDC card) with  TP-Link Archer T3U Plus does not work.

I think it has to do with a feature of the Unex DNUA-93F called "Off-load capability".

Has anyone successfully replaced the WiFi dongle that comes with NAD BluOS2i MDC card?
I had issues with the bluos2i module dropping off the network at random intervals (sometimes even while streaming).  That wifi dongle that comes with the MDC module is complete garbage.  I ended up using a wifi ethernet bridge and using the wired ethernet port on the MDC module.  Has been stable ever since.
Hi, actually I have same issue now, since I recently bought NAD C388 with MDC Bluos 2i but unfortunately the usb wifi adapter was broken now and I was trying to see if I can replace with a new one. I read through your conversation and did some investigation as well. I noticed the original usb wifi is drive support with win7 and Linux (ath9k_htc), would that be possible that usb wifi adapter is like free drive and linux supported. Since I would guess Bluos is based on Linux. I also bought a TP link usb wifi adapter but that needs me to install driver, so I can not use TP link ones at all. 
@parkzhi 
Seems there are three options, listed best -> worst result:
  1. Run Ethernet cable to the unit
  2. Use a wifi bridge for improved wifi
  3. Call NAD/Lenbrook and order a replacement wifi dongle. NAD support is good when you use their website to open a ticket.
I have moved on to NAD M12, which uses the exact same dongle, and am still using that for wifi connection. Having both C388 and M12 (without built-in amp), I can say that any improvement of sound quality from the 'upgrade' is marginal.
I didn't need the amp section of C388 and wanted the M12 for its features - specifically the digital coax output and XLR in/out - M12 also has bigger, nicer, touch screen.