But the Aune T1 input is USB Type B. How to connect let's say 6.3mm to USB type B input on Aune T1?
I am not sure why you want to use your ibasso as the source if you aren't taking advantage of its internal dac. You cannot use the t1 as a portable amp/dac, so I don't see why you would want to pair it with the portable ibasso that already has a built-in dac/amp.
Since the t1 is a nonportable desktop amp/dac combo, if you want to use the t1's dac, just use your computer as a source. note the t1 is a tube-powered dac + a solid state amp. If you are looking for the tubey sound to "pair" with your ibasso's dac, shouldn't you be looking for a stand-alone tube amp?
http://www.head-fi.org/a/ibasso-dx50-faq
"Can I use my DX50 with an external amp?
Oh yes you can! The DX50 features a crystal clear analog 3.5mm lineout straight from the WM8740 DAC chip. Adding an amp can improve detail retrieval, soundstage, and add raw power.
But the lineout is variable, is it a true lineout then?
Yes, the lineout completely bypasses the Internal amp of the DX50. It just so happens that Ibasso has implemented the volume control in the digital domain, directly on the DAC chip. This ensures a perfectly controlled 255-step volume setting with zero channel imbalance or potmeter noise - just like they did on the $830 DX100. This also means that you can control the volume of the lineout. For best results, turn it all the way up to 255 when you are using an amp. Should your amp be too powerful for use with your IEMs or sensitive headphones, feel free to lower the volume on the DX50. Congratulations, you just added 255 more gain settings to your amp!
Can I use the DX50 with an external DAC?
Oh yes you can! The DX50 features a 3.5mm digital COAX output allowing you to use an external DAC of your choice. This will allow you to digitally connect the DX50 to your home setup for use as a transport only or to use a balanced portable DAC like the Ibasso DB2 for instance."
You will probably need to find something that has coax input into usb output or just find another dac that supports coax input. However, I don't see why you would bother with all that as the dac built-into the ibasso is probably about equivalent to any amp/dac combo in the sub-$200 price point.