Xin Reference

 

The Xin Reference is an evolution and extension of the Xin Micro, which in its own right has been a very highly regarded instrument, despite the tiny size and somewhat fragile appearance.   The Reference is housed in the same size case as the Xin Super Macro and LE.   The approximate case size is about 3.25" L X 2" W by 7/8" thick. 
 
The front panel controls are limited to an On/Off switch and a volume knob, located in the center of the front panel.   The input is on the right side of the front panel, while the headphone receptacle is on the left side. (when facing the amp)  There is also a blue "on" light that dims, then extinguishes when the batteries near exhaustion.
 
One very unique feature of this amp is that one can order it with 1/8" stereo miniplug input and output, 1/4" input and output, or both.  One can also specify that the output is both size, while the input can be a single receptacle of your choice of size.
 
The Reference is powered by (4) AAA cells with no provision for onboard charging or external power sources.  This is by no means is a disadvantage, as the 4 cells will provide power for several hundred hours of operation.
 
Now, on to what is the most important characteristic of any amplifier...How does it sound??

 

Sound
 
In one word, SUPERB!   The sound can best be described as open and spacious.  Bass is very tightly controlled and deep.  Whatever the source delivers, the Reference will deliver.   The better the source, the better the sound.  The audio performance of this amp, regardless of the genre of music sourced, belies its small size and lack of bells and whistles. 
 
There have been several beta versions of the Reference made available during the time that Dr Xin was refining and perfecting the circuit of this amplifier.  Mine has a very large 22,000 uf electrolytic capacitor, while others have had 12,000 uf caps.   There are reported to be very small differences between the two cap sizes, but both sound superb.  I am uncertain at this time which cap will be in the final production version.
 
The Reference lives up to its name, providing a truly accurate, natural soundstage that somehow is able to extend beyond the confines of ones head.  One soon forgets that it is headphone sound rather than a live performance that is being heard.
 
I have found during comparisons with my other headphone amplifiers that there is absolutely no need for any bass or loudness contour or enhancement with this amp.   If one needs to correct for a deficiency of source or phone, slight EQ changes in the source player can easily shape the resultant sound to ones individual preferences.   I find that the output thru all of my evaluation phones sounded quite good without any need for EQ. 
 
The Reference is able to drive both my efficient and sensitive IEMs as well as my Sennheiser HD650/Revelation without any strain, audible artifacts or effort.   The background with all of my phones is totally silent, no hiss, hum at all, just total blackness.
 
I am often asked to describe the sound of the Reference...is it warm, cool, punchy bass, etc etc...My answer is none of the above, or all of the above.  The Reference is precisely what its name implies.  The sound signature is exactly what is fed into the input.   Instruments with complex harmonics such as oboe, violin, piano, etc are rendered in a most lifelike fashion.  Vocals are realistic with accurate placement of vocalist and instruments

 

Conclusion

 

My summary would be that it ranks with the best portable amps as far as quality of sound and ability to drive most any headphone to a level that would be damaging to ones hearing over a period of time.   Deep bass response, given an accurate source, is nearly unbelievable for such a small, seemingly simple amp.   Soundstage is also remarkable, extending beyond the confines of the headphones.
 
About the only drawback of the Reference than I can think of is that it has fixed opamps, and those who like to roll opamps are just out of luck!  Neither are there any other user controls to play with.  Just turn it on and enjoy!
 
I believe that Dr Xin has spent more time developing this amplifier than any he has previously designed.  His design intent was to provide the absolute best sound possible from a portable amp.  IMO, he has succeeded in not only reaching the pinnacle of portable amps, but it also compares very favorably with much higher priced audiophile headphone amps that are nowhere near as small and portable. 
 
Ron Kerlin
(HiFlight)