Guys, we need to separate a few things here: physics, biology, and the human brain. No one is trying to take away anyone’s enjoyment of the hobby, but comparisons like the capacitor one are fundamentally flawed from a physics standpoint.
1. Why the capacitor comparison doesn’t hold up:
A capacitor (like a 3.3µF cap) works passively in the signal path and comes with component tolerances of often 5% to 10%. A cheap capacitor might actually measure at 3.0µF, while a precision one sits right at 3.3µF. This shifts the crossover frequency in a circuit in a way that is both measurable and audible! Plus, different designs (electrolytic, film, ceramic) have different internal resistances (ESR).
A modern operational amplifier (op-amp), however, is an active, highly complex integrated circuit made of hundreds of transistors. Its sole purpose is to amplify the signal one-to-one without altering it. When Amir at ASR measures two different modern op-amps and the distortion and noise floor of both are well below -110 dB, they are both absolutely transparent. Physics-wise, there is simply no signal left at the output that could possibly be different.
2. Biology beats us all (A reality check):
I’m over 55 myself. As a truck driver, I’ve had to undergo official, medical hearing tests every five years since turning 50 to keep my commercial driver’s license. That’s where you see the naked truth in black and white. My hearing rolls off right around 12 to a maximum of 13 kHz—which is actually an excellent biological value for our age group!
When people in forums claim that an op-amp swap suddenly opens up whole new worlds and ‘lifts veils’ in the upper treble—where the airy details and the proverbial ‘harp-playing elves in the moonlight’ live—it is biologically impossible for our age group. We simply cannot hear those frequencies anymore.
3. The human factor and the room:
On top of that, our hearing is extremely dependent on our daily condition. If I’ve been sitting in the truck cab all day or working with a weed whacker, my hearing biologically switches into a protective mode (Temporary Threshold Shift). Anyone comparing audio components after that is mostly measuring the fatigue of their own ears. Furthermore, our acoustic memory only lasts for a few seconds. The time it takes to power down, open the chassis, swap the chip, and boot everything back up is way too long for an objective comparison.
In the end, room acoustics (lack of calibration) and your own daily physical condition alter the sound by orders of magnitude more than a tiny silicon chip with measurably perfect specs ever could. If someone hears a difference, it is often just a tiny volume mismatch of 0.1 dB (which the brain instantly interprets as ‘better’) or simply the psychological desire for the mod to be a success.
Amir provides reproducible measurement data. Anyone claiming the opposite should subject themselves to a properly level-matched blind test. This isn’t about ‘opinions’—it’s about science.
Prost
