So according to your conception, tube amps have no reason to exist? if an amplifier does not have a SINAD worthy of ASR, does it mean that it should be thrown away and bought only Topping?
Now you are fishing!
What has ASR or SINAD have anything to do with this discussion?
Any decent amp, be it Valve or SS will do, for as long as it is up to the task (low distortion/noise, adequate output drive capability, flat frequency response).
Not all amps
are up to the task, for any headphone, though. some amps do not have enough juice for inefficient headphones, some have too much noise for very sensitive IEMs, so care
should be taken there.
But to choose an amp, because it sounds bright to counter dull headphones, is like using a butter knife as a screwdriver! I bet any amp, that has a bright or dull sound, is badly engineered, and the flaws don't end there. They most probably, are distortion boxes too.
A properly engineered device (of any kind), will not have an issue with tonality, which is such an obvious flaw.
You want to EQ, use an equaliser, not an amp with substandard tonality.
Valve, SS, OTL all are good, if properly designed and made.
As an OTL designer and DIYer, I can assure you, a valve OTL amp sounds just as bright (or dull) as any other amp.
Valve amplification sounding warm, is a myth! bad ones do, good ones are indistinguishable from any good SS amps.
