Note: To skip the miscellaneous spewing just jump to the last paragraph.
In the pre-digital days of analog I embarked (with my colleague) on a challenge of attempting to capture the sound field of acoustic instruments or group of instruments (piano, harp, violin, viola, cello, double bass etc) in an acoustic space (room, hall, church etc) and reproducing that performance later.
Studying the research of Alan Blumlein and others in the field of psychoacoustic and the reproduction of recorded sound using two loudspeakers (stereo) we experimented with various microphone techniques, equipment required to capture the sound, and then reproducing the performance in its acoustical environment . Critical listening of the transducers, electronics and microphone techniques led us to the conclusion that within the limitations of “stereo”, the Blumlein (X-Y) and/or Mid-Side (M-S) were the best compromises. In other words no mono multi-micing and pan pots.
Determining the least compromised recording chain (microphone, mic preamp, storage medium etc) required extensive listening tests.
Through a audio equipment review publication I had access to a vast number (fifty or more) of preamplifiers and power amplifiers and in a controlled listening environment these circuit designs were critically evaluated through extensive listening and measuring tests.
The conclusion was that a properly designed circuit (preamplifier and amplifier) with “wide bandwidth” offered the most “accurate” ability to pass through and amplify a signal and convincingly reproduce the original performance in its acoustic space. Textures, clarity, attacks, overtones, imaging left to right, perceived depth and room acoustics were more convincing or “accurate” with wide bandwidth designed electronics.
There are obviously a multitude of other factors such as negative feedback, transformers etc. that I won’t go into here. By the way, the recording chain that I settled on was completely tranformerless from microphone to storage medium. The end user/listener of the music of course used a 33 1/3 rpm phonograph disc so it was necessary to test that part of the chain via listening to the mastering of the disc process (half-speed mastering etc) and the vinyl itself (TELDEC ie Telefunken Decca virgin “pure”vinyl was vastly superior to anything. Hold it up to a light bulb and you can see light through it).
A very talented electronics designer once told me that in order to accurately reproduce audio within the human hearing range requires a circuit bandwidth of ten times the highest reproduced frequency (20kHz x 10 = 200kHz). The same applies going below 20Hz. Although we can hear up to 20kHz why go beyond? Because in order to accurately reproduce up in that range the circuit bandwidth must exceed 20kHZ significantly. The engineer/designer words, not mine.
Pulse tests, square wave test etc bear out his theory. Feed something in and watch if the circuit can accurately reproduce the impulse without overshoot and settle down again requires bandwidth. What does a 10kHZ square wave look like on the leading edge? Did not matter what the circuit topology was/is ie. transistor, IC, tubes, FET etc.
Moving forward in time to digital capture and reproduce and try this simple experiment:
Take a quality acoustic guitar (preferably a Martin made in the mid 1930s through 1944) that has responsive attack (impulse) and rich overtones and put it and the player in a nice sounding room.
Set up a high quality (Schoeps etc) condenser pair of microphones in a stereo configuration such as “crossed figure eights at 90 degrees to one another”; cardioid or super cardioid at 120 degrees; figure eight and cardioid in the MS configuration.
Record the performance at 44.1k 24 bit and at 48k 24 bit. Listen to the playback of each sample rate version over properly setup quality speakers or even quality headphones.
What does this have to do with an electric guitar plugged into a limited bandwidth tube amplifier fed into a transformer and then into an even more limited bandwidth speaker (or that same signal chain only substitute the KPA after the electric guitar)?
Accuracy is not a goal with most sound recordings. The Neumann U-47 or M-49 are considered by some to be the “best” vocal mics ever made and they were made sixty to seventy years ago. They really are not from a technical specification accurate but their euphonic colorations offer a desirable “quality” that many preferred both back in the days of Frank Sinatra and the Beatles through today even when thrown into the final end user’s listening experience ie. 128k (or less) lossy Mp3 and lastly the “in ear” “headphones”.
Long way of saying:
The KPA now allowing 48k (or higher) as the external master clock is a benefit to me because other acoustic instruments and vocals in the 48k 24 bit DAW project can/will sound better at the higher rate and the SPDIF out sounds better to my ears.
But the downplay of anything else because «I’ve done testing and know what to listen for» kind of rubs me the wrong way.