They are hard to do with speakers and headphones but very feasible for amplifiers. Yes, there is some trickiness with matching levels when output impedance of the tube amp makes variable level shifts based on frequency. Other than that, you just need an AB switch and you are ready to do the testing. You can start single blind and see how far you get. If you fail that test, i.e. get different results sighted vs unsighted then no need to worry about double blind.
Agree, and I am lenient. I say that it’s fine to match the tube to the solid state at a specific frequency or pink noise. Once you add the variable frequency response, it SHOULD make it even easier to show a difference in the blind testing. Part of the variable frequency response is part of the effect.
But it will be very hard to identify the tube in double blind testing even then.
If we consider whether it is possible to measure something, we must define what are we measuring.
Unless you’re doing null comparisons between recordings — which I have used to document differences that are vanishingly small but potentially real.
That is, false positive differences can occur but false negatives are rare. When the null comparisons hit -120 dB or more, then you can confidently say that there is not difference.
You can quote a distortion figure in percentage for an amplifier. You must quote the frequency of the signal being measured (ok, we assume a sinusoid), its level, and we obtain a figure. A figure is a single dimension. How much information can a single figure portray?
Two different pieces of equipment with the same measured frequency response and distortion can sound radically different.
No one Rarely does anyone think that a single number (such as SINAD) is sufficient to define the performance of a product. Amir says it the best: if SINAD was the only thing we needed, why would he waste his time doing all the other tests? A poor SINAD conveys a lot less than an excellent SINAD but you also need the IMD and multitone tests.
I agree that frequency response into a resistor may not predict sound into speakers. BUT while I agree poor measuring may sound good, I would *love* to see a single example of two electrical products with similar frequency response into load and similar *low* distortion that sounds *radically* different.
Now speakers? Yes. Frequency response and distortion can sound radically different.
What is the harmonic content of that distortion, it, its spectrum?
How does it vary with level?
How does it vary with signal frequency assuming a sinusoid?
Do other complex products such as intermodulation appear when we are not playing a humble sinusoid but real music?
So, you can measure it. But good luck trying to obtain a measurement that can really characterise it in a useful way.
Sure, but Nelson Pass has made attempts to characterize it. Hobbyists have made attempts to characterize it. So why do we give up so easily when it comes to manufacturers or commercial magazines?
The best strength of measurements is identifying stuff like AC mains noise. It has zero role for beneficial audio, so it’s a very consistent goal that tube and solid state fans can agree upon. When you say that we only know a little bit about characterization and give up completely on objective measurements, it’s no good for anyone but the retailers.