2. amps-preamps
  3. 169435-165413

Deciding if I like Class D.

I recently purchased Goldenear 1R towers. I was powering them with my Oultlaw 770 initially. I’ve also used a 350 wpc McIntosh a friend owns.. I realize the Outlaw is not audiophile grade, but it’s actually better than most give credit for.  Anyway...

Even though the built in subs are powered, the towers still benifet from a good amount of power, up to 650 rated, so I have been on a quest to find the right amp.

I purchased a set of Hypex Ncore NC1200 Monoblocks with custom buffer boards, and it came with Sparkos 2590s Opamps as per my request. The Goldenears are slightly forward, and I was told Sparkos was the way to go because the were warmer in presentation .

So, I let the amp break in, playing it when I wasn’t home at 85 to 95 DBs for a few days, and gave it some good material to assess it.

I was immediately disenchanted, because the amps sounded very dull, and the highs were rolled off considerably. When compared to the A/B amp the D was not pleasing to my ears. My hearing is slightly diminished from combat, but the A/B was much more detailed.

So I called the company that made amp, and he was very polite and helpful. He sent out a set of Weiss OP2 and Sonic Imagery 990 opamps,to see if I preferred the sound characteristics. Well, the difference was significant.

I am using a Marantz 8805 preamp in pure direct mode . Using BlueOs Streamer, using both optical, and a analog outputs for the testing.. Analog is required to get the MQA files to give full resolution.

To me, the Sparkos just killed the sound. I could honestly see why reviewers would say the treble in particular, was not musical. If I had to live with that sound, I would not..

The Sonic 990 was much better. Much more detailed, better sound stage, just better overall.. Then, I tried the Weiss. Well, that was another level altogether. It sounded like the McIntosh, perhaps better in some regards, but to be honest, it takes a lot time and A-B testing to really be sure. None the less, after hearing the Weiss, it was obvious that they were superior to everything else.

So, I called the manufacturer to let him know my findings, and he said, well, I should give the Sonic 990 another try. I asked why. He said the Weiss would add over 600 dollars for the two pair over the Sparkos and Sonic Imagery.

So, that would bring this setup to over 3100 for the pair. And I could buy a ’good’ high power A/B for that used or even new.

I’ve read a lot of opinions on this forum, and I know the consensus is that D is good, but not great. I know people usually defend what they own, so I needed to hear it for myself. Without a basis of comparison, I’d probably never know the difference, but to be honest, aside from the Hypex getting much louder, and without any audible distortion, I really think the A/B *may* still be more musical, but dammit, I’m not 100% sure. It’s subtle at best.

After hearing the Weiss Opamps, I’d not be satisfied with anything else, but with them, the price is commensurate to A/B.

I’d really appreciate your input on this subject..

BTW, I have purposely left out the company I bought it from, because I think component wise, they are all pretty similar,and I don’t want to start any BS.

I will say though, at the end of the day, the op amps make-or-break the amplifier.

Thank you
Rick




knowitall
georgehifi's avatar
georgehifi
10,312 posts
 

knowitall OP
I purchased a set of Hypex Ncore NC1200 Monoblocks with custom buffer boards, and it came with Sparkos 2590s Opamps as per my request.
I was immediately disenchanted, because the amps sounded very dull, and the highs were rolled off considerably. When compared to the A/B amp, the D was not pleasing to my ears. My hearing is slightly diminished from combat, but the A/B was much more detailed.


This is probably the reason for what you heard (red trace) with Class-D a massive phase shift starting at 1khz and getting to 70 degrees!! out of phase by 10khz!!! with rapidly increasing distortion (blue trace).
https://ibb.co/3Sg9bZY

All this is put down to the low order output filter, that has to filter out the 600khz switching frequency from the output.

Simple, if the switching frequency was made far higher from 600khz to 1.5mhz as in the (GaN Technics SE-R1), then the output filter can be moved up accordingly 3 x higher along with the "phase shift" and "distortions" and as a result most of those two nasties will then be well out out of the audio band.

Cheers George
knowitall OP
12 posts
 
If that’s the case George, then why does the op amps make such a significant difference, and in a positive way?
georgehifi's avatar
georgehifi
10,312 posts
 


knowitall OPIf that’s the case George, then why does the op amps make such a significant difference, and in a positive way?




All input buffer opamps on the input of Class-D’s have their own sounds. The Hypex NC500 monoblocks (same as Belcanto Reference 600 monos) but with linear power supplies that I also use, I changed and chopped around those input opamps also and got "different" sounds also.
BTW the best sound now from the NC500’s is "no opamps at all", as I can feed my MSB Discrete R2R dac's very high balanced 6v output that has volume control, directly into the NC500’s balanced amplifier stage without having their input opamp buffer stage in the signal path at all.

But they still never get rid of the problem of that phase shift and rising distortion, which to me "sounds like" theirs a different amp from what’s playing the lower part of the music, it’s like there’s a segregation of bass/mids to upper/ mids highs, like two different amps are playing, it’s very listenable still, but not as good as the very best big linear power amps I have.

Cheers George
mike_in_nc
1,154 posts
 
>> The purpose of this post is to give my opinion . . . and ask if the price tag on the Weiss, which brings the cost over 3000, is worth it or not. <<

As @russ69 said, SURE it’s worth if, given you much prefer the sound.

I’ve bought many components in my 55+ years of audio fever. Not once have I looked back and said: "Oh, I wish I’d bought the cheaper one."

Not that expense is always a marker of value; but when you find something you like and can afford, a delta in the cost is not a big consideration. At least that’s my way of thinking.

P.S. Unless I’m missing something, the detailed spec sheet of the 1ET400A module does not bear out the claims George is making about phase shift and distortion. He may prefer other amps, but that’s a different question.
knowitall OP
12 posts
 
Well, money is not the issue. As I said, it's what the money gets me that matters. 

George, my Goldenears, as you may know, have a bass section that is powered by its own built in class  D '1600 watt' amp. So the Hypex is basically a line preamp. I'm wondering if perhaps that negates the issue you describe with the phase shift ? Honestly, I'm not sure how that would shake out. 
More to discover