Re; Dynamics, Class D vs tubes…

@daytrader you don't need an amplifier with a 100k input impedance with many tube preamps, there are many made today that have a low output impedance.

It’s a Shindo Aurieges, this is how Stereophile measured it…

The output impedance at 20kHz was very low, at 23 ohms. It rose to 139 ohms at 1kHz, which is still low, but at 100Hz it measured a very high 3700 ohms. It rose even further as the frequency dropped, to 11k ohms at 50Hz and 16.5k ohms at 20Hz. I assume that this drastic rise in impedance is due to the Aurieges Equalizer Amplifier’s output being taken from the tubes’ plates via a coupling capacitor. With line preamplifiers having an input impedance of less than 100k ohms, this increasing output impedance at low frequencies will roll off the bass.

On the test bench, Shindo Laboratory's Aurieges Equalizer Amplifier produced mixed results. The very low levels of distortion and extraordinarily high overload margins must be set against its nonflat RIAA response, its high level of flicker noise, and its high output impedance at low frequencies, which will make system optimization tricky.—John Atkinson

Not to forget, with a tube pre amp one would need a solid state amp with 100k input impedance to give that dull range .

@daytrader We make tube preamps that can drive 1000 Ohms no worries, with the output impedance being a straight line across the audio band, so no loss of bass impact. IOW not all tube preamps are the same.

 That is because tube amps tend to boost the “bass-slam” frequency range when mated to highly reactive loads.

@helomech This statement is false. Usually its the other way ’round. What tends to cause tube amps to seem to have more power than solid state amps of the same rating is the way they make distortion, particularly, as you alluded, near clipping.

Usually its the other way ’round. What tends to cause tube amps to seem to have more power than solid state amps of the same rating is the way they make distortion, particularly, as you alluded, near clipping.
 

My experience is otherwise. Maybe because I am more accustomed to push-pull tube amps. IME it is quite obvious when a tube amp begins to run out of steam because the dynamics suddenly go flat. 

Maybe because I am more accustomed to push-pull tube amps. IME it is quite obvious when a tube amp begins to run out of steam because the dynamics suddenly go flat. 

@helomech Its really hard to generalize how tube amps clip. Some are quite graceful; typically having little or no feedback. But if the amp has a lot of feedback the clipping point will be a lot more obvious. Some in the middle WRT to feedback will seem to just compress a bit (if the power supply is adequate) before the onset of obvious clipping.

Most tube amps with feedback have a higher output impedance than a solid state amp, but if treated properly can behave as a Voltage source on most speakers. Because of the higher output impedance they generally don't like obtuse phase angles (highly reactive loads) and tend to make less power driving them on that account Since obtuse phase angles are usually a bass issue the amp might seem a bit bass shy.... But again we are talking generalizations since not all speakers are the same in that regard!