To understand both the SR-71B’s strengths and limitations, let me suggest that you listen to excerpt of John Tavener’s Icons of Eros, performed by the Minnesota Orchestra and Chorale as conducted by Paul Goodwin, from the Reference Recordings 30th Anniversary Sampler [Reference Recordings, HDCD]. This unusual composition at once sound modern and yet almost medieval, with some passages that are driven forward by a percussion ensemble captured in the highly reverberant interior of the Cathedral of Saint Paul in Minnesota. What I’ve always found fascinating about this particular track is that its beauty and complexity derive not only from the sound of the instruments at play, but also from the way their sound lingers on the air, reverberating in the Cathedral long after they have stopped playing (by design, the composition features a number of short, interleaved musical passages with carefully spaced pauses in between).
The SR-71B sounds very, very sophisticated on this track—better by far than most competing portable amps. In particular, neatly delineates the complex instrumental voices and reveals the reverberant qualities of the recording space. However, if you do a side-by-side comparison between the Ray Samuels amp and a really first-rate mid-priced desktop amp (e.g., the Burson Soloist), it becomes apparent that some can potentially provide better resolution of low-level details, even more nuanced handling of transient sounds, and thus greater realism overall. On Icons of Eros, one hears these differences as an increase in overall three-dimensionality and especially as a heightened sense of the “air” surrounding the instruments and filling the interior of the cathedral. While the SR-71B can and does hold its own in comparison with like-priced desktop units (arguably surpassing many of them), those willing to invest a bit more will discover an even higher level of performance can be had. This comment, however, in no way diminishes what Ray Samuels has achieved with the SR-71B; for its size and price, this tiny Titan is flat-out amazing.
CONCLUSION
Consider this portable headphone amp:
Look further if:
Ratings (relative to comparably priced portable headphone amps):

BOTTOM LINE:
Given the veritable explosion of high-performance, high-end earphones and headphones we’ve seen over the past few years (some of which are quite challenging to drive), the Ray Samuels Audio SR-71B fully balanced portable headphone amp is plainly an idea whose time has come. What we have here is a beautifully made little portable amp that, in terms of I/O features and sound quality, seems more like a sophisticated desktop amp than a typical portable. If you want one of the two best portables ever made, consider this a must-hear option.
Comments
Thanks for a great review Chris. I have owned this amp since November last year. I have an iPod/CLAS using Wav files and connected with silver interconnects. I have been listening with the LCD2's, FAD Heaven S, Etymotic ER4S. Recently I purchased the Final Audio Design Piano Forte IX's and right now I think I have reached the pinnacle of what I am going to experience with this set up. The inclusion of the IX's has really shown me what a capable and musical amp this is. I have found the low gain setting to be perfect for all the headphones I use the highest I have found I have had to dial the knob is to around 2pm for the LCD's but for everything else pretty much noon is all I need to go. In fact I have found that the IX's do not require huge volumes to explore subtleties and dynamics in music.
I think the ALO ( I have had an extended audition of it) and this one are so close as to it being not so much which is better but more the type of musical presentation one likes. Also, after many hundreds of hours of listening I do not find the difference between single ended and balanced output to be that great, especially as you have said, it is more dependent on which headphones your listening through. I get more space and sense of occasion listening single ended though the IX's than I do balanced ( with custom silver/gold toxic cables HP cable) with the LCD's.
If you ever get a chance I really recommend a listen of the IX's, they are not for everyone but if you 'get' what they are about nothing else comes close!