Class D or Tube Amplification?

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Niteshade

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Class D or Tube Amplification?
« on: 21 Mar 2010, 01:45 pm »
Class D vs. tube: Which one?

Similarities:
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

Differences:
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.  :D
« Last Edit: 22 Mar 2010, 12:32 pm by Niteshade »

Niteshade

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Re: Class D or Tube Amplification?
« Reply #1 on: 22 Mar 2010, 12:35 pm »
If you own both amplifier styles, go ahead and post your comments.

steve k

Re: Class D or Tube Amplification?
« Reply #2 on: 22 Mar 2010, 03:50 pm »
Very well said, Blair. This is pretty much what I've found in my expereinces with both. The only thing I would add is I think Class D amps have a much lower noise floor than tube amps (well at least my VTL's). I find myself enjoying classical music much more now that I can truly enjoy the full dynamic range of the music and the micro detals that used to get lost in the noise floor of my tube amps.

The other thing regarding bass response is I think Class D is faster. I get less overhang and smear in the bass as I used to get with my VTL Deluxe 300's. The transients are much faster and more lifelike in Class D.

I think your horizontal description of the soundstage with Class D is spot on.

Overall you've nailed it. I hope this makes for an interesting discussion.
steve

6SN7

Re: Class D or Tube Amplification?
« Reply #3 on: 22 Mar 2010, 05:05 pm »
I agree totally with what both of you have said.  The only thing I miss after replacing my Antique Sound Lab tube mono blocs with two of Tom's class D amps is the 3D soundstage.  Horizontal separation of instruments and total soundstage width with the new amps is great, but the depth I used to enjoy so much just isn't there, even after fiddling with speaker position. 

I listen mostly to classical music, and it's always fun to follow an instrument's line through even a complex mix, and the class D amps allow me to do that with ease.  No matter how complex things get, each instrument's sound remains clear and detailed.  I suspect, as does Steve, that a lot of that comes from the class D amps' much lower noise floor.  "Speed" is a much debated topic (what does that really mean?), but I'd have to say that the new amps' ability to provide clean and clear sound is at least partially due their increased speed over that of tubes.

Whatever the case, class D works for me.
Bob

DustyC

Re: Class D or Tube Amplification?
« Reply #4 on: 23 Mar 2010, 07:28 pm »
I looking into building one of these Class D amps for bass duty in my bi-amped system. I wonder if this loss of 3D depth that some tube users are talking about is due to the loudspeaker/amp interaction. Stereophile always shows a frequency response chart with the result of a simulated loudspeaker load in their amp tests. The midrange is usually depressed compared to the extremes and this could result in a feeling of recessed soundstage. I remember playing with a parametric equalizer years ago and a lot of the subjective terms that critics used to describe sound (midrange honk, spitty highs) I could create using this device.
Solid state amps had much less of this interaction with the speaker load and have a flatter response.  :|

Niteshade

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Re: Class D or Tube Amplification?
« Reply #5 on: 24 Mar 2010, 11:02 am »
I believe a Class D is fine for subs. These amps do have a positively stunning grip on the woofer.

What loss of 3D depth with tube amps? I haven't heard of this complaint regarding the technology as a whole. Tube amps actually have a fluid frequency response, one without holes in it. Sometimes there are speakers with literally whippy impedance plots that can mess things up- but it has to be very bad. I use variable feedback in my amps so the amplifier's response can be customized to the speaker.

jtsnead

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Re: Class D or Tube Amplification?
« Reply #6 on: 24 Mar 2010, 12:53 pm »
I just got a Virtue Tripath amp and the depth I am getting out of it
is as good as my tube amp

It would be interesting to compare these ClassDamps to the tripath
models

OzarkTom

Re: Class D or Tube Amplification?
« Reply #7 on: 29 Mar 2010, 01:27 pm »
I just got a Virtue Tripath amp and the depth I am getting out of it
is as good as my tube amp

It would be interesting to compare these ClassDamps to the tripath
models

What is the difference between Class D and Tripath? I also just bought a Virtue and having no problems with depth.

Niteshade

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Re: Class D or Tube Amplification?
« Reply #8 on: 29 Mar 2010, 11:41 pm »
They're both PWM (Pulse Width Modulation) amplifiers. Tripath is a type of Class D amplifier. Class D refers to an amplifier which uses transistors as switching devices. Class A & AB amps are referred to as linear amplifiers since they use the transistor while it is "on".

http://en.wikipedia.org/wiki/Class_T_amplifier

I like Tripath's method of making a Class D amplifier. They do sound good!