I just had a threesome. Overall. It was very disappointing.
BTR15 Bluetooth on iPhone. Next.
BTR15 on iPhone wired high gain is plenty loud. But sounds like the dead is talking to you. Flat, no dynamics. Bass is poorly defined. Where is the treble? You might as well use those earbuds that come free with your phone.
BTR15 DX260 wired. A little better, but everything above applies.
The BTR15 is capable of plenty of loud. But that is just it. It's loud, and the sonics never improve. It's just yucky soft and yucky loud.
BTR7 iPhone wired. It's much lower in volume compared to the BTR15. Drives the Titan loud enough. But dynamics is pretty poor. Imaging is poor. Treble is just sad. Blackpink sounds like Mickey Mouse.
BTR7 on DX260 wired. Much better. Only requires half the volume. Mids sound much fuller. The treble is still poor. What is supposed to be sparkly tingles in Robots in Motion, sounds like the toilet flushing. The dynamics are still poor. Very poor sound coherency.
BTR7 on an Andriod wired is acceptable. A waste of of the Titan, but acceptable.
AK HB-1 iPhone Bluetooth. Very low volume. Unusable. You have to plug in the USB and the volume will 2x.
AK HB-1 iPhone wired. Very loud, only needs half volume. Dynamics is decent. Trebel is good. Imaging is decent. Bass is decent. Mid volume is the best. Overall poor sound coherency. Beyond that is loudness with no improvement. iPhone bluetooth or wired sounds the same.
AK HB-1 DX260 wired. Sounds about the same as the iPhone overall. Bass thump sounds bigger and deeper.
I have 3 dongles and none of them drive the Titan to its full potential. In fact, the 2 Fiio dongles make it sound like a mediocre chifi offering, with poor technicals, either no treble, or sharp if it appears. Lousy imaging, bass is present but lacks quality. The AK HB-1 is better. But it still doesn't drive the Titan anywhere near what it can do.
That is about all I can endure. Hope it helps.