After reading numerous positive reviews of the On2, I took advantage of a visit to New York and stopped at Audio 46 to try them out. Tony helped me at the counter and I spent about 1/2 hour comparing them to my best on-ears, which are also highly rated. The On2s were clearly superior, and not by a small margin. The real test came when I got home and plugged them into my Burson desktop headphone amp/DAC. I had been hoping to get on-ears that gave me a similar musical experience to my beloved Sennheiser HD650s. Well, these Thinksounds do it. While on-ears can't be expected to compete in soundstage with over-ear-open phones like the HD650, the On2 does come pretty close. And they actually beat the Senns in midrange/treble clarity and detail. All the while they are very similar to the Sennheisers in easy-to-listen-to musicality - with no annoying distortions whatsoever. After two weeks of listening I am very pleased and have no problem recommending the Thinksound On2. I fully understand why Stereophile gives them a Class-A rating, right next to other brands costing several thousand dollars.

 
Disclaimer:
Bhavneet from Burson Audio offered to send me the Cable+, with no return required, asking me only to post my honest evaluation of its performance when used with the Chromecast Audio. I have no affiliation with Burson other than I purchased, at retail, their Conductor SL DAC/headphone amp with the ESS Sabre 9018 DAC back in May of 2015.
 
Also note:
I am not treating this as a full review of the Cable+ or the Chromecast Audio. Others have done a great job of covering aesthetics, build quality, electronics, and connection options of these devices. The Burson website has an excellent description of the Cable+ and Google can fill you in on the Chromecast Audio and the various streaming capabilities it offers.
 
Initial skepticism:
I first heard of the Burson Cable+ in October 2016 when I received a Burson email announcing the Cable+ and inviting me to visit their IndiGoGo page. The device was intended to better match the audio output of a smartphone or laptop to a “line level” device, like a headphone amp or home stereo amp, claiming to thereby improve the fidelity of the connection. Reading the explanation posted by Burson made me think “What a great idea. Why hasn’t someone done this before?” Every time I have used a phone or laptop as a source to drive a line level device I have been disappointed. Even when adequate volume was possible, the sound quality was always weak, flat sounding, and not at all engaging. I figured that the poor sound I heard was the product of small/cheap/low power components and that any quality in the sound was destroyed before it even got to the 3.5mm output jack. Burson claims that the quality is actually still there but is being ruined by the mismatched connection. This Cable+ could be great - if it really does what Burson says.
 
But, because it adds another device in the signal path, it seemed to me that besides making the signal stronger there was a strong chance that it would also change the overall balance and quality of the sound. That would not be good.
 
The email also contained a link to the Head-Fi discussion forum on the Cable+ started by Voxata. I began following that forum and even contributed a couple of posts. I have to admit I was skeptical of the observations some were making about the improvements the Cable+ was capable of, especially those not involving smartphone or laptop sources. Even though intrigued, I was not all that interested in getting a Cable+ as I never really need to use a smartphone or laptop as a source.
 
Chromecast Audio:
My main headphone system consists of a Squeezebox Touch streamer (with the Enhanced Digital Output mod installed) streaming mostly 44/16 and 96/24 files to a Burson Conductor SL 9018 DAC/amp, using the optical connection. To me, this setup sounds wonderful driving my Sennheiser HD 650 headphones. Being that the Squeezebox itself has been discontinued and it’s software is only partially supported, I am always wondering what I would do if it failed (maybe a Raspberry Pi?) So, when the Chromecast Audio with built-in digital optical output was offered for only $35 (and requiring no Linux tweaking) I purchased one right away. I found that streaming from the Chromecast Audio (I’ll refer to it as “CCA” from now on) to my Conductor using the digital optical connection, resulted in sound quality equal to that of the Squeezebox Touch using the same optical connection.  The CCA proved to be a possible replacement.
 
I had little interest in the CCA analog output but I did give it a try, connecting it to the line level RCA inputs on the Conductor headphone amp. It produced nowhere near as good sound as the CCA optical output, but was somewhat better than any smartphone or laptop I had tried - more volume and more fullness to the sound. Still, it was not up to what I consider hi-fi listening.
 
But, one day I tried plugging headphones directly into the CCA and found that the sound was really good. Plenty of volume and a full-bodied sound very similar to what I’m used to hearing from my main rig. Plenty listenable. Even though Google advertises the CCA for use in line level setups like home stereos, it seemed to be better matched for direct connection to headphones. This direct-to-headphone experience made me realize that the analog output of the CCA actually had the capability to produce very good sound.
 
I had also been following and contributing to the Head-Fi forum on Chromecast Audio. If you read my posts there you will see I am very enthusiastic about the CCA’s abilities as a simple inexpensive high quality streamer/headphone amp. I continue to use it often in that capacity, mostly when I’m too lazy to fire up my main system.
 
Burson Audio Cable+
I assume it is because of my posts to the Head-Fi CCA forum that Burson asked me if I would like to try the Cable+ (“C+” from now on), stating that it “pairs perfectly with the Chromecast Audio turning the CCA to a truly hi-end audio source” and that “the resulting improvement is across the entire audio spectrum and you will immediately hear the difference.” How could I pass up an offer like that?
 
I reconfigured my system, connecting the analog 3.5mm output of the CCA to the RCA inputs of the Burson Conductor SL using the Chromecast’s supplied short yellow 3.5mm male to 3.5mm male cable and a short 3.5mm female to 2-RCA male adapter1. Then the C+ could easily be inserted in place of the stock yellow cable.
 

 
Initial listening:
Going into this, I was afraid that the analytical auditioning/comparing experience would be tedious, with a lot of back and forth switching between the stock cable and the C+, while trying to identify minor sonic differences. But with the CCA/C+ combo this was not the case at all. What I was hearing right from the start with the C+ in the circuit was impressive - dynamic full spectrum balanced sound - very much like what I am used to with my Touch. A huge improvement over the stock cable, and not at all hard or tedious to identify the differences. As promised, the volume was greater with the C+, requiring a setting of about 9:30 on the Conductor’s volume knob vs 12:00 or more with the stock cable. But the most important improvements were in overall sound quality. Pretty quickly, I gave up switching cables and just immersed myself in the good sounds coming out of the C+2.
 
I could at this point in the review lapse into repeating all the usual audiophile improvement cliches - soundstage depth and width, instrument placement, dynamics, clarity, bass control, blackness of background, etc, etc, etc. But there is really no need. You name it, every one of them was drastically improved with the addition of the C+.
 
Listening to well-recorded pop music the improvement was substantial. Besides the expected increase in volume, everything just sounded better, more musical, smoother and at the same time more dynamic. I was starting to believe Burson’s claim about turning the analog CCA into “a truly hi-end source”.
 
Next I cued up some classical. The improvement in sound quality was now nothing short of astonishing. With the stock cable, high-dynamic-range material sounded pinched, small, narrow, tinny. With the C+, the orchestral sounds opened up, strings were sweet,  the bass came back in full force, the sound of the recording space returned. Solo pianos gained an exciting fullness and had none of the jangly harshness on loud passages that always seems to be the case with lower-end sources.
 
No aspect of sound reproduction got worse. I could find nothing to complain about.
 
As you might expect, my auditions of other types of music - blues, female vocals, jazz combo, big band, folk etc - were equally impressive. I am not into heavy metal, electronic, or dance but I heard nothing that would cause me to think those genres would sound any less great.
 
So, as Burson’s email had promised, I did “immediately hear the difference” and “the resulting improvement is across the entire audio spectrum”.
But, the BIG question still needed an answer…
Does the Cable+ turn the Chromecast into “a truly hi-end audio source”?
 
Critical listening:
Fortunately the Conductor SL has multiple inputs which are easily switched by a front panel control. So I fired up the Squeezebox Touch, connected through optical, and cued up the same track on it and the CCA. Switching between the CCA/C+ (RCA input) and Squeezebox (optical input) the difference in sound quality was…
   wait for it…
   wait for it…
there was NO difference. Everything sounded exactly the same as the excellent bit-perfect Squeezebox optical connection to the Conductor's Sabre 9018 internal DAC. Could this be true?
 
I should point out that at this time I was surprised to find that the CCA/C+ combo actually played LOUDER than the optical connection on the Conductor - plenty of gain - requiring a lesser setting on the volume knob (maybe 9:30 on the dial vs 10:30). When doing A/B comparisons, level matching is very important. Rather than fiddling with the analog volume knob every time I switched sources, I decided to try using the CCA’s digital volume control to set matching levels3, knowing full well that this would stray from “bit-perfectness”, and might put the CCA/C+ at a disadvantage4.
 
Tedious:
Next, I played my favorite test tracks, all different genres, over and over, again and again, listening to various parts of the sound spectrum, the quiet parts, the loud parts, the instrument and vocal timbres, all the while syncing tracks and switching between the CCA/C+ and Squeezebox Touch sources. To my surprise, there were still no differences that I could identify. Both sources sounded equally excellent. The results were so convincing that I did not feel it necessary to repeat listening tests using the analog volume control for level-matching.
 
As a final test I spent many hours just listening to my favorite music using the CCA/C+ as the only source. In the past, when trying different component setups I have always been very intolerant of long-term listening with anything exhibiting less quality than what I am used to with the Touch/Conductor SL 9018 setup. Not this time. The music from the CCA/C+/Conductor SL was and is totally satisfying.
 
Answer:
Well, “hi-end” is different things to different people, but to this skeptical audiophile the answer is...
YES, the Cable+ does turn the Chromecast Audio into a hi-end source when inserted in my system5. The combination of the DAC/amp in the Chromecast Audio and the Cable+ offers the same level of performance as the bit-perfect optical stream fed to the well respected Sabre 9018 DAC. And it does so without damaging the "audiophile" qualities of the sound in any way.
 
The C+ has earned a permanent place in this skeptic’s main system.
 

 
Cons?
The only two downsides I can think of are equipment related
   - first, I now have one more “wall wart”
   - second, I have another cable getting tangled behind my rig.
I can live with these.
 
Conclusion:
I came into this review expecting a change in sound quality similar to that experienced when swapping cables, small differences, some good, some bad. I was wrong. The Cable+ is capable of making a substantial difference - all good.
If you own (or are contemplating purchase of) a Chromecast Audio, and use the analog output connected to a line level device, I definitely recommend that you consider adding the Cable+. I can’t think of anything else that offers this level of streaming performance and audio quality at anywhere near the asking price.
And for someone wanting to put together a streaming headphone system with fine sound this Chromecast Audio/Cable+ combo would be an excellent place to start. Just add a decent headphone amp with RCA inputs and you are ready to go.
 
Footnotes:
1 I realize it is entirely possible that the native Cable+ 3.5mm to RCA would perform better than my setup with the RCA adapter.
2 Unless otherwise noted
 -All listening was done at what I consider “realistic” levels, that is, if I were at a club or concert hall, this is the SPL I would be hearing from the stage or PA system.
 -Only well recorded material was used. No over-produced over-compressed stuff. Why punish myself?
 -The Burson Conductor SL was set to High Gain - appropriate for the Sennheiser HD 650
 -The digital volume control in the Chromecast Audio was set to maximum - the analog volume knob on the Conductor was used to control listening level.
 -An Android phone running the BubbleUPnP app was used as the control point to “cast” the music stream directly from a local DLNA server to the CCA.
3 BubbleUPnP enables the use of a 50 step volume control on the CCA, making for smaller steps and allowing for more precise level matching than the typical digital volume control (some have only 20 steps). No decibels-per-step amount is specified but the setting used to match the optical connection turned out to be 43 out of 50.
4 My experience using the CCA as a headphone amp convinced me that it’s digital volume control was excellent. Used as a headphone amp, recordings generally required a setting of only ⅓ to ⅔ of the scale and the sound quality did not suffer at all. There was no disadvantage. Digital volume controls have really improved as of late.
5 Realistically, my headphone setup is rather modest as hi-end systems go. But it does produce a very good listening experience. How the Chromecast Audio/Cable+ would compare to a $$$$$ streaming system I don’t know. But also realistically, these are not SOTA devices and are not meant to compete with systems like that.

Not really a review, just an observation on the color. 
 
When I first got them I thought they were black.  Others have said they were blue.  After a while, I thought I could see some blue but they still mostly looked black.  In most online photos they look black, sometimes with a slight hint of dark blue.  I asked my wife what color they were - she said black.
 
Then, one day they were sitting on the table across the room and the sun hit them.  Blue!  Blue metalflake even!  Took this picture.
 

 
The shot doesn't really do them justice.  The flake actually has a depth like you'd see on a custom street rod.  Very cool.  And very definitely blue.