It isn't ever clear what it takes to get a particular sound. There are many SS amps with silky top ends and each one is done differently so it appears there are several ways to achieve it.
I used to think that slightly reduced top-end frequency extension was the main way but then if you look at, for example, McIntosh MC501 in Stereophile measurements section, their -3dB point is at 120kHz - and that is with an output autotransformer! So that guess is flawed.
One reason could be that a smooth top end can be induced from the other end. A slight excess of bass can make the top end appear silkier. I have expereinced this first hand since I use a horizontal biamp configuration in my stereo. If I turn down the gain on the high amp, thereby effectively boosting the bass, the highs will seem softer eventhough the tubes are firmly in their linear region of operation. The perceived spectral balance is a relative thing.
So there is no clear answer. I think there is probably an exception to whatever rule we can come up with. Even an amplifier is a highly complex system and once you hook it up into another highly complex system such as a stereo, well, you know what happens....
In terms of whether it is good or bad, that too is entirely relative. With edgy speakers, it is good and not a coloration but perfect "neutrality." But with soft tweeters, it isn't. The fact is, nothing is perfect and everything is different so words such as "colored" and "neutral" are effectively meaningless.
Arthur
I used to think that slightly reduced top-end frequency extension was the main way but then if you look at, for example, McIntosh MC501 in Stereophile measurements section, their -3dB point is at 120kHz - and that is with an output autotransformer! So that guess is flawed.
One reason could be that a smooth top end can be induced from the other end. A slight excess of bass can make the top end appear silkier. I have expereinced this first hand since I use a horizontal biamp configuration in my stereo. If I turn down the gain on the high amp, thereby effectively boosting the bass, the highs will seem softer eventhough the tubes are firmly in their linear region of operation. The perceived spectral balance is a relative thing.
So there is no clear answer. I think there is probably an exception to whatever rule we can come up with. Even an amplifier is a highly complex system and once you hook it up into another highly complex system such as a stereo, well, you know what happens....
In terms of whether it is good or bad, that too is entirely relative. With edgy speakers, it is good and not a coloration but perfect "neutrality." But with soft tweeters, it isn't. The fact is, nothing is perfect and everything is different so words such as "colored" and "neutral" are effectively meaningless.
Arthur