The Truth about Modern Class D

I agree with most here that you can no longer define Class D as a particular "sound" and that the sound quality varies tremendously depending on module selection and implementation. I have Thiel 2.4s and Aesthetix preamps with a Direcstream. An unusually large proportion of Thiel owners (the vintage speakers not the ’new’ Thiel) ended up with Bel Canto Ref 1000 Mk II mono blocks as their amplifiers of choice. For a brief period I used an even older version of the Bel Canto amps: the 300M monblocks. More recently I tried the Bel Canto Ref 600s expecting great things but I was REALLY disappointed. On those amps I heard a recessed upper midrange and slightly rolled off highs. I also tried a pair of Red Dragon monos based on the recent ice power modules as well as one of their stereo amps based on the Pascal modules. Those units didn’t sound bad necessarily, but were in my system rather one dimensional. I eventually ended up trying non-class D amps including the Bryston cubed series and the Pass Labs products and ended up with Pass Labs which tick just about all the boxes for me. In my system the Pass Labs .8 series tonal balance is a little on the warm side but the detail and depth and general musicality of those products is difficult to match. I wouldn’t care if my Pass Labs amp was Class D, Class A, or Class QXZ, I would still love love love what they do.

@guidocorona 

"Thank you so much Merrill!" - Most Welcome. 

"Indeed I had suggested a few small things... I believe that you actually implement my recommendation to use 20A IEC to maximize stability of connection with heavy power cords.... Well, at least now, if anyone complains about 20A inlets, you can refer their  lamentations all to me *Grins!*"   - You are rather modest. You have more other subtle contributions which I have valued over the years.

"BTW, have you published pricing for Element 116 and 114?"  Soon to be priced. The ELEMENT 116 will be announced shortly. It will be priced at $22k. This is mean to be the replacement of the VERITAS Monoblocks, although as you heard, a very significant upgrade. 

The ELEMENT 114 will be a stereo version to keep the price down and give those with space constraints what they want. The price will be announced Q4 of this year.

 

Let me begin by saying I am by no means an "expert" on class D power amps, but here are my impressions.

I first auditioned a class D amp around 10 years ago, driving a pair of larger, floor standing B&W speakers, and thought the result was somewhat harsh for acoustic music, but "exciting" for rock and roll.

Fast forward to last Fall and I had the pleasure of auditioning a Mytek Brooklyn amp driving a pair of bookshelf sized KEFs and thought the result was very good!  I also auditioned one of the PS Audio Stellar DAC/amp combinations and that also didn't have that harsh sound of the class D amps of yesteryear.  In both cases, these amps sounded "fast" and "clean".  One thing both owners said to me was that it took much longer than normal for these amps to break in and sound their best.

If I were in the market for a new amplifier, I'd give class D some serious consideration.

Cyrill Hammer (Souloution)

"if you want to have your product performing at the cutting edge it is not possible with today’s known switching technologies. In order to come close to the performance of the best linear design we would need high-current semiconductors that provide switching frequencies of several MHz or even GHz."

This is the one, that I believe hits the nail on the head, and why to some that hear it Class-D sound in the upper ranges hasn’t come of age yet.

Only Technics with their unobtainable $30k SE-R1 comes close with a 1.5mHz switching frequency instead of what all the other are using today 400-600kHz. But as Cyrill Hammer states it should be even higher.

The quote from Mr. Hammer is false. Here's why:

As @merrilaudio states, the problem is dead time. Dead Time is the delay time that has to be inserted in the circuit so that both output devices are prevented from being partially on at the same time. If this isn't done, a phenomena called 'shoot through current' occurs. This causes the output devices to heat up and fail.  The problem is that dead time causes distortion. So with any given output device, there is always a certain minimum distortion and associated maximum switching speed.

Technics sort of got around the problem by brute force- going to an output device that was so much faster that they could reduce deadtime and also switch faster (BTW their 150 watt version of this is about $18,000....). However eliminating dead time is what works- you can actually have lower switching frequencies with lower distortion if you don't have to have deadtime circuits!
As some of you may know, we've been working on a class D for a bit over a year and a half. Although we are known for tube gear, in particular OTLs and balanced tube preamps with direct coupled outputs, it turned out that we seemed to have something to bring to the class D table. May a year ago we had working concept, today we have prototypes that demonstrate how a class D sounds if deadtime is eliminated. Our amp is not based on anyone's modules and we have a patent filed with another on the way. So far the prototypes have switching speeds between 250KHz and 500KHz. The amp is very smooth and extended, lacking grain or harshness. It easily compares to many tube amplifiers in that regard. It is zero feedback and exhibits soft clipping.

We don't think its ready for prime time yet; in that regard I've yet to hear a class D (including the Technics) that is, but we are very excited about our class D as it sounds better than any we've heard. I think merrilaudio knows what we are talking about; eliminating deadtime is the single most important hurdle to cross in class D amp design (especially if you can run MHz+ switching speeds), and I'm going to go on record that any amp that employs deadtime to work is an amp that will become obsolete.

merrillaudio said... "The ELEMENT 116 will be announced shortly. It will be priced at $22k. This is mean to be the replacement of the VERITAS Monoblocks, although as you heard, a very significant upgrade."

Hi Merrill. The new amps sound like they will be awesome...congratulations!!! Now... if I can only figure out where to come up with $22 K ..ouch ! Me thinks my Veritas monos will have to do. 8)