Class D vs. tube: Which one?
1] Neither is clinical
2] Both are very fast
3] Micro details can't hide from either one
4] Nothing like the 'standard' solid state stereotypical sound
1] Imaging, sound staging
2] Bass management
3] Low efficiency speaker performance
Tube amplifiers do a wonderful job in the imaging department. It is difficult to beat a well designed tube amplifier that places sound in front of the speakers and can represent the spatial characteristics of a recording. You could call it sonic holography. Speed and the ability to reproduce a linear, contiguous frequency spectrum are ingredients required for good spatial representation. Where do Class D amps and tube amps differ in their spatial makeup? I feel that Class D amps have less of a forward representation and more of a horizontal one. They leave more space in between instrumentation. Highs are crisp and fast, providing a feeling of in-the-room presence. A tube amplifier, such as a SEP-30 will provide vocals with more presence, extend imaging infront of the speakers and less horizontal. The entire spectrum is more fluid. Bass output is accurate and there on demand, while the Class D's is more pronounced and can obtain bone jarring intensity. Class D's do have superb superb woofer control.
Keep in mind that amplifier power can have an enormous influence over delivery performance. The Class D module we're using can provide up to 250 watts per channel into a 4 ohm load! Power is not all about volume, it can have a major impact on representation. Some speakers are both very dynamic and sensitive while others are very dynamic and insensitive. Either model requires a special amplifier to perform at their peak. I chose the NS-60 as the top performer for high end Zu's and the RF-83 by Klipsch. These speakers perform exceptionally well under the dynamic demands of movie sound tracks and music with a wide volume separation between low and high passages. If the speaker can absorb it, make sure it is there for it to take advantage of. That's all there is to it. Class D as well as mid-power tube amplifiers are great for these applications.
Low efficiency speakers should stick with either high power Class D or large tube mono blocks. Look at it this way: If a Zu MKII recommends an amplifier that can produce 60 watts per channel and is
100db efficient, what do you suppose an 88db efficient
speaker should have for available power? I would recommend an amplifier that is no less than 100 watts per channel. That equates to a high power Class D or tube mono blocks. My Von Schweikert VR-2's can absorb allot of power. They play remarkably well with amps from 20 to 60 watts per channel, but perform miracles with amps that are at least 100 watts per channel. The VR-2's require at least 60 watts per channel for a high impact listening session. The added 40 watts of headroom increases clarity two-fold. Why butt the poor 60 watt amplifier against the stops? That does not work very well.
What you choose for an amplifier depends on several factors, more than I have stated above. This is a good start. People often ask me what will work best with their systems. They include room size, past and present amplifiers used, kind of music listened to and naturally the speaker system. This is ALL very important information and it is required to make a proper decision. Potential customers tell me their sonic preferences as well. Some people like crisp, extended highs, other like smooth highs. Others want special attention to vocals. I had one individual who plays kick drums and wanted something that could respond well to them. Everybody is different. Note that I would recommend our Class D amplifier for kick drums.
We will be coming out with some tube/Class D hybrid systems soon that have unique capabilities.