I am the proud owner of the fabulous Matrix M-Stage headphone amp. Immediately, out of the box, I loved this headphone amp. I am also a Radio Broadcast Engineer. I maintain radio stations, and have been, for a number of decades now. Radio stations are loaded with audio equipment. I have been listening to, and educating myself, on audio, for over 50 years. I also enjoy audio at home too, where I am better able to critically listen. My current favorite headphones are the SONY model 7506. I'm sure you have seen these everywhere. I have tried many sets of headphones over the years, but I seem to always come back to these, as I feel that they are extremely flat sounding, but at the same time, extremely revealing.
Purchasing the Matrix M-Stage has made my headphone listening take on a whole new experience. I thought this was the ultimate I've ever heard in headphone listening...until, I replaced the M-Stage's stock OPA 2134 op-amp chip, with a Burson Audio V5 SS (Supreme Sound) op-amp chip. Whoa! Immediately out of the box, I heard a difference in sound with this V5 chip. But, was the sound an improvement over the stock chip? I really had to study the sound of this chip, because it was was so dramatically different than the OPA 2134. It only took a few day days before I realized that the V5 SS chip was simply amazing, to the point, I probably couldn't live without it.
One of the most impressive aspects of the V5 is the improvement it makes in S/N ratio. Now S/N ratio is something I definitely know about. I strive for, not only in my home audio system, but also in the radio station studios I maintain, for the lowest noise floor possible. The Burson Audio V5 SS op-amp delivers an amazingly quiet noise floor. Music simply rises out of a blacker than black background. The bass response of this chip is to die for, and the high frequencies are unbelievable. I couldn't believe the texture I was hearing from violins. If you have an M-Stage, do your ears a favor, and give this op-amp a try. You won't regret it, as it is worth every cent. Changing out the op-amp is simple.