@unbiased, i just finished to talk of avantree with
@headcoatman.
We both tried the Priva.
You should have definitely contacted their support. One of the best ever.
It may be a conflict (in which case, it is not said that the adapter is guilty! I had perfect Aptx with the Priva... Tested with an HarmanKardon BT wich also have a led which changes according to the kind of connection active).
Or it may be a defect unit.
Maybe Priva and Miccus use the same chip which is not working well with those Sony.
Anyway the Sony make strange things too, I had the MDR-10RBT and they blinked 2 times in Aptx mode.
Can you please make a comparison of those adapters about sound quality and wireless range?
I suspect that the Avantree Priva and the Miccus TX4 are using the same chipset and software/firmware and that's why they both exhibit this bug.
I use the CSR based AZIO Bluetooth AptX USB dongle and also the similar SuperTech Bluetooth AptX USB dongle on my Windows 8.1 Pro 64 bit PC's and the Sony headphone connects properly each time with those dongles.
The Sony headphone connects properly in AptX mode and also connects properly with my AptX enabled cell phones and tablets.
The Sony headphone DOES NOT connect properly with these stand-alone transmitters for some reason (the Avantree Priva and the Miccus TX4).
Something seems to be going on between the communcations protocol it seems with these devices that the Sony does not recognize it is supposed to be in AptX mode.
I suspect a software bug in these devices that got implemented wrong and causing lack of communications in AptX mode. The vendors should contact CSR to check into the software that CSR provided to them for these particular applications.
In the meantime, I have another Sony MDR-XB950BT headphone on order and I will test that headphone out in AptX pairing mode when I get it to see if it does the same thing.
As for comparing the two transmitter brands, I find that they are pretty much equal in sound quality and transmitter range. The sound quality is fine on both. However both stand-alone transmitter devices have weaker signal range than the USB Bluetooth dongles that I also have and use (the AZIO and the Supertech AptX USB Bluetooth 4.0 dongles).
The Avantree Priva is Bluetooth 3.0 whereas the Miccus TX4 is Bluetooth 4.0 (how important this is or what sonic differences it might have, I have no feel for. They both sound and perform the same to me).
The Avantree Priva seems more versatile in that it has an on/off switch for battery or power DC mode and it also shows what transmit mode it is in by flashing the LED light.
The Miccus TX4 does not give you any indication of what transmit mode it is connected in. It also does not have an power/battery on/off operating mode switch.
Both models can operate with the micro USB power plugged in so that you don't have to run down on battery power (this is a good feature for both brands).
The Avantree Priva gives you one more cabling adapter connections included in the box so is better in that respect and cost about $1.00 (USD) less than the Miccus TX4... but it is Bluetooth 3.0 vs Bluetooth 4.0 for the TX4 if that matters to you.
I think I like the Avantree Priva round shape and magnetic base mountability form factor better than the Miccus TX4 stick form factor. But both are acceptable.
That's all I can think of for now.