That one's easy, loss in dynamics. It's usually caused by substandard power delivery inside the component to the active devices, but can also be caused by impeding of transient current flow in the AC due to inductance, resistance and other mechanisms.
Steve N.
Empirical Audio
Actually, no. I sort of laid a trap. I knew people would say "DYNAMICS!" But even while that can be true, it isn't what you're going to get to first. The amount of capacitance in the gear is enough to keep up with most loud notes fairly well. At least in an SPL sense. You'd have to be very familiar with the music pieces, and even then with the average audio memory it can be a stretch to really know where the dynamics are at.
People often don't know/realize that breakers while rated at say 15A can give instantaneous amount for burps that are way over 15A. What actually triggers them isn't the amount of current, but how long an excess of current is being used. That's why turn on for massive amplifiers can trip them, but playing won't. The caps charging takes too long, so they trip. When playing they could exceed the ampere amount from turn on, but only for a short moment. (that doesn't mean they do)
It's all kind of funny because what we perceive as dynamics don't necessarily align with SPL readings. And I'm not talking about woofer burps or other stuff, I mean in music. Phase, feedback, and many variables can make dynamics sound loud or small with similar SPL. It's because cues are there in the music for the fundamental, that let us know when something is loud. Frankly we don't even usually know by ear when crest factor is really tested. I have one of the loudest crest factor albums ever made, and unless someone told you, you'd never know the particular sound that is going to drive the most power.
Back to a lack of current... The most evident and clear thing that happens first is the high frequencies sound softened, even muted. You may not experience any other changes until you really lose a lot more. I know, it sounds
odd but this is what shows up first when your gear can't get enough current. If you think about it, the high frequencies are occurring much faster so they are more dependent on available supply, say, from the transformer. Where as the big notes have moments between them so the capacitors can actually work with them, and recharge. This is something I've worked with by changing 1 variable at a time, instead of swapping entire pieces of gear.
stage scale, width, height and ease.
when I insert a modest powered tube amp in my system it's the scale which immediately changes that jumps out. same thing as lowered current. the leverage of the amp on the speaker is lowered.
amp headroom, or lack thereof, is musically significant.
Now this is an answer with some experience. Mike isn't just assuming it's dynamics, he actually knows that all these things sound different. Now whether or not it's because of current when comparing amps, I would not specifically assume that. It's tough when comparing totally different amps, to know exactly what all the factors are. The important thing here is that Mike can tell us what he hears, and not what he would assume for at least the changes in sonic qualities. For the most part, knowing what I do about design of amps, I'd say the DartZeels are simply a different breed than the smaller tube amps, irrespective to current.
When it comes to headroom it can be a function of voltage, as you many simply run out of ability to match the gain requested. Voltage = volume potential in watts. The current can dump into something at massive amounts but if the voltage in an amp isn't high enough then the actual SPL will never increase. And then it sounds flat when it shouldn't. (the DartZeels have
plenty of voltage)
) Also, I think as Mike said it seems like distortion occurs at a lower db level as volume is increased.
