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The Truth about Modern Class D

All my amps right now are Class D. ICEpower in the living room, and NAD D 3020 in the bedroom.

I’ve had several audiophiles come to my home and not one has ever said "Oh, that sounds like Class D."

Having said this, if I could afford them AND had the room, I’d be tempted to switch for a pair of Ayre monoblocks or Conrad Johnson Premiere 12s and very little else.

I’m not religious about Class D. They sound great for me, low power, easy to hide, but if a lot of cash and the need to upgrade ever hits me, I could be persuaded.

The point: Good modern Class D amps just sound like really good amplifiers, with the usual speaker/source matching issues.

You don’t have to go that route, but it’s time we shrugged off the myths and descriptions of Class D that come right out of the 1980’s.
erik_squires
erik_squires OP
16,039 posts
 
Hey @jdl57 - I have heard the effects you are talking about in a number of hotel rooms. It was poor room acoustics.

IMO, one should examine the cable/speaker impedance curve when choosing ANY amplifier. Class-D can be more sensitive due to the low pass filter.

It is true that knowing both behaviors is important, however Class D output impedance is well within the range of high quality Class A/B amps with feedback.

The Class D amps I am most familiar with have lower output impedance than most tube amps, but probably not as low as some beasts like the Codas or Sander’s with their 30 transistors per output channel. :)

Keep in mind a lot of linear amps have a low pass filter on the output to prevent oscillation. Then there is the Technics amp which actually measures the speaker impedance and compensates for it with DSP. Pretty nifty.

Best,
E
tweak1
3,653 posts
 
My experience with Ric Schultz’s EVS 1200 with barely 75 hours is; it is vastly superior to my previous class D amps 2 different W4S (~ 8 years ago), Emerald Physics 100.2 SEs (3 years ago), Audio Alchemy DPA-1 which I just sold to keep the 1200, and PS Audio M700s, which sounded like the DPA-1 with 2.5xs the power, which my room demands (MSRP $2999). The EVS uses 2 of the newest 600w IcePower modules, which he then does a number of tweaks to, plus other cool tweaks an Italian chassis: $2200,

If interested, I have  thread on Agon
ieales's avatar
ieales
1,201 posts
 
It is true that knowing both behaviors is important, however Class D output impedance is well within the range of high quality Class A/B amps with feedback.
The Class-D output filter is RLC with the speaker providing the R. However, the speaker is not just R, but also has LC components. Like all things audio, the designer has to make choices. Regardless of how well designed the amplifier is, there will be loads with which it will not mate well.

Add in loudspeakers with crappy phase response and things could get ugly in hurry.

I think of it like putting an Indy engine in my motorhome. It's got boatloads of power, just in the wrong area. Put my motorhome engine in an Indy car and it will come dead last in 500 miles, but first in 5000.
erik_squires OP
16,039 posts
 
Regardless of how well designed the amplifier is, there will be loads with which it will not mate well.


Which is true of all amplifiers. The output impedance of amps without any output filtering at all is far more complicated, and the output impedance of tube amps is RL as well.

Which goes back to my original point that Class D amps are not stand outs in output impedance anymore. You have to listen for yourself.

There are a lot of tube amps which do poorly with ESL speakers, for instance. Linear SS amps tend to do better, but not in every case. Class D is somewhere in there. Depends on the specific implementation.  Despite this, there are a number of audiophiles who end up running tube amps with ESl's. Technically I'd be surprised if the Class D amp didin't measure better.

It is prejudicial to be comparing Class D in bulk with mega linear amps at all times. Lets be more realistic.
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jdl57
37 posts
 
Hey @jdl57 - I have heard the effects you are talking about in a number of hotel rooms. It was poor room acoustics.

This was in a large conference room, much bigger than any room would be in a normal house. The speakers they were using was the Sigma Acoustics MAAT Vector XAC. They weigh 750 lbs each. I doubt the room had any effect on the sound at all, there were no close walls to reflect anything except for the one behind me. The ceiling was probably 20' high.
I specifically wanted to hear these amps and the Kii speakers since I had heard such glowing reports about both of them. I will say I was much less disappointed by the Vivace amps than I was the Kii speakers.
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