"that does not explain why digital into tube amps produce 'warm'. Any thoughts on this?"
Most tube amps sound warm because their response rolls-off lower in frequency than SS amps. Most tube amps also have rather primitive power supplies for the plate voltages, not including fast-acting regulators or fast decoupling caps. These slower reacting power systems do not provide the power needed for high-frequency transients, so it softens the sound.
There are exceptions however. I have modded some tube equipment to fix these deficiencies and the top end softness disappears. They sound a lot more like SS, but with better midrange. The best of both worlds. Bass is always a problem with tube amps however. Its virtually impossible to get the really low impedance output required to control the bass of most speakers.
The mass of the needle assembly on a tonearm will also ultimately limit the reaction time and therefore the high-frequency dynamics. Even if the cartridge measures well beyond 20kHz using a steady-state waveform, it will fail to reproduce accurately a HF dynamic waveform, thus sounding softer.
Solid-state digital can also produce the dimensionality and smoothness of vinyl, but is requires several things:
1) very low jitter in the digital signal
2) lack of digital filtering in the DAC or minimize the effect
3) very linear I/V conversion in the DAC
4) excellent fast-reacting low-noise power supplies in the DAC
With 1-4, digital can actually beat vinyl. Makes sense because the physical limits of the cartridge are eliminated.
Steve N.
Empirical Audio
Most tube amps sound warm because their response rolls-off lower in frequency than SS amps. Most tube amps also have rather primitive power supplies for the plate voltages, not including fast-acting regulators or fast decoupling caps. These slower reacting power systems do not provide the power needed for high-frequency transients, so it softens the sound.
There are exceptions however. I have modded some tube equipment to fix these deficiencies and the top end softness disappears. They sound a lot more like SS, but with better midrange. The best of both worlds. Bass is always a problem with tube amps however. Its virtually impossible to get the really low impedance output required to control the bass of most speakers.
The mass of the needle assembly on a tonearm will also ultimately limit the reaction time and therefore the high-frequency dynamics. Even if the cartridge measures well beyond 20kHz using a steady-state waveform, it will fail to reproduce accurately a HF dynamic waveform, thus sounding softer.
Solid-state digital can also produce the dimensionality and smoothness of vinyl, but is requires several things:
1) very low jitter in the digital signal
2) lack of digital filtering in the DAC or minimize the effect
3) very linear I/V conversion in the DAC
4) excellent fast-reacting low-noise power supplies in the DAC
With 1-4, digital can actually beat vinyl. Makes sense because the physical limits of the cartridge are eliminated.
Steve N.
Empirical Audio