One Manley figure that could give gold-digging speculators pause is a published signal-to-noise ratio of 83dB. Referenced against modern sources that work at better than -120dB, that's a loss of at least 40dB. It factors as 14-bit resolution versus 20 bits, so a sub Redbook CD result that mirrors the retro look. For example, the noise floor of AGD's Vivace PreDac's at right is ~140dB.
How Manley's rarely encountered SPL limiter works I learnt when my loaner arrived set to less than what Susvara needed. At first I didn't understand unexpected behavior of refusing to get louder. Then I remembered. I looked for the trim pot on the back and defeated it. Instant full gain. Coming off a Bakoon AMP-13R as our best head amp, switching to the Manley no matter its NFB value or pp/se mode meant a different aesthetic.
It spoke to a warmer thicker more wall-of-sound presentation. I was used to (conditioned by, you might say) ultra lucid holography, max magnification power of micro detail, superior bandwidth and speed. Before I could approach the all-tube Manley difference on its own terms, I had to forget our house sound. I needed a brain wash so that the Absolute could overwrite my older OS. This was a rerun of Stereophile's infamous Cary/Krell cover of January 1994. It's byline read "if either of these amplifiers is right, the other must be wrong".
To escape its Spockian logic by which our own amp was right, I stopped listening to it with headphones for a stretch. As much as possible, I wanted to meet the Absolute as though I'd not done headfi in ages. I'd then immerse myself in it before switching back to the Bakoon for obligatory contrast. Would the AMP-13R register as wrong now?
Binary thinking can be quite dull. It might suit absolute sound thinkers but overlooks that like a Baskin Robbins ice cream shoppe, there are many different flavors, each with its own admirers. That renders them all equally valid.
To present two domestic favorite flavors for context, here's our Raal Requisite SR1a rig. It begins with a Soundaware A280 SD card transport which sends binary digits to a Kinki Studio DAC. That feeds the matching 200wpc integrated amp to drive Raal's impedance converter box which renders the ribbons' 0.018Ω of a virtual short as a very happy stable 6Ω instead. As an AKG K1000-style floating geometry of open baffles angled out holding transformer-less ribbons which put nothing between membrane and ear—the only magnets sit on the narrow edges above and below the ears—there are no ear pads to trap air and cause compression and reflections. That means zero energy storage and the most dynamic resolved fast sound in our entire hardware inventory.
On the other side of this room lives a compact speaker/headfi system. It also starts with a Soundaware SD card transport. Its digits are converted by a Questyle CAS192 DAC. Depending on speakers, that either drives Bakoon's AMP-13R direct; or detours through a Nagra Classic set to 0dB gain. Now a tube current buffer without voltage gain injects very minor thickening and softening over the bypass. It simply benefits inherently leaner speakers with hotter tweeters. This Swiss small-triode circuit betters a -120dB S/NR as documented by my unit's specific test results. That quite differs from Manley's engineering focus. For headfi, here HifiMan's Susvara resting on the African head are the usual loads which I run without the Nagra. Likewise for the Final Sonorous X on the canine aviator. The Audeze pre-fazor LCD-2 and LCD-XC on the shelves purely serve as back-up review comparators. For my current tastes, they are too warm, thick and fuzzy to be on any pleasure rotation.
Now you appreciate what I'm used to for headfi. Here are three more data points. On my work desk, a COS Engineering H1 drives a pair of Final D8000 planarmagnetics for a somewhat warmer slower sound best suited to lossy Spotify and YouTube streaming. In the big rig, a Vinnie Rossi L2 Signature drives HifiMan HE-1000 in balanced mode using direct-coupled Elrog ER50 in a grounded-grid circuit for 900kHz bandwidth. Sennheiser HD-800 and Beyerdynamic T-1 have gone into permanent storage. My primary headphones are the SR1a and Susvara. It's admittedly fancy fare priced accordingly but it's where two decades of doing hifi have landed me. If you can drop $4'500 on a headphone amp, chances are that your loads will be of equal pedigree.