The gist of the video is that they both sound about the same.
That’s pretty close to my experience, actually–with most headphones I’ve still not heard any major differences between the two amps. Any time I think I may have, I’ve been able to A-B, volume match by ear, and get the same results.
That’s more or less the same conclusion I’ve arrived at with the Neve amp. SINAD of 101 vs 119 for the THX amp? Not making a difference to me. At least not with the sampling I’ve done. FWIW, I’m feeding both with an ADI-2 DAC (SINAD 112).
Per Wikipedia:
The 16-bit compact disc has a theoretical undithered dynamic range of about 96 dB; however, the perceived dynamic range of 16-bit audio can be 120 dB or more with noise-shaped dither, taking advantage of the frequency response of the human ear.
I’m still wrapping my head around how to best integrate that, but in simple terms it seems like ~96dB of clean signal is perfectly transparent for CD quality (16/44) audio. But that doesn’t completely line up with all of my personal experiences.
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The real trouble with measurements is that they attempt to reduce a multidimensional landscape into a 2-dimensional graph or one-dimensional number. With context they can be very informative and helpful, but they are always an incomplete picture.
For example, SINAD is a function of input amplitude and frequency. Vary either of those and the numbers will change. Use a single reference frequency and level and you get a good “thumb in the air” idea of transparency, but not enough information to call a SINAD ranking an absolute ordering of device quality.
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One thing I disagree with in the review is calling the 887 a more powerful amp. The THX amp has a linear power response. Here are the specs:
Meanwhile, RNHP:
On the THX amp as load doubles, power output is halved. The RNHP has a non-linear power output. Anecdotally, it does a better job of powering my 600 ohm Beyers than the 887 does (both SE). I think that flies in the face of the oversimplified claim that THX has more power.
Where the RNHP struggles a bit is with low impedance headphones that are also insensitive. Amir mentioned the Ether CX, which are a good example:
This is where the gobs of power from THX amps at low impedance really come in handy. With Ether CX balanced out of the 887 bass is more impactful and the overall sound signature is more coherent and clean than it is from the RNHP (SE). Interestingly enough, the RNHP will drive the CX plenty loud, but they’re just not well controlled.
Meanwhile, I’m listening to Orbital today out of the RNHP / Sundaras, and they sound pretty great. Sundaras have just a bit higher load (37 ohms) and just a bit more sensitivity (94dB). Could be that pushes them closer to RNHP’s sweet spot (or maybe they’re just better headphones), but in either case they’re a better pairing for RNHP than the CX.