Class D amp fans / foes ?

[gianni]

I'm still in the process of trying to find where I stand in the Class D vs traditional linear amp debate knowing that the debate may never be put to rest and that both may coexist for many years to come. In any case I need to do more listening with some different speakers.

I've been encouraged by the growing positive feedback here on Rotel's class D models. I came across this article: http://www.hificritic.com/downloads/Class-D.pdf.

I'm wondering if those of you with considerable experience with these class D amps feel that the shortcoming listed in this article are:
1) valid but mostly addressed in the newer designs
2) possible theoretical drawbacks that are not an issue in practice
3) just flat out do not apply.

Could it be that these new amps are even more system dependent than traditional linear amps? Or, are they less so and are the naysayers just skeptical of these new designs which they don't fully understand. I really want to focus purely on performance as the advantages of heat/space are pretty hard to argue.

[kmcheng]

Audioholics.com also came out with a article on Class D amplifiers. http://www.audioholics.com/education...one-amplifiers

I am using class D power (Bel Canto S300i) for my 803D and have been quite happy so far. I was considering switching to the new Krell integrated but decided against it. I figured that whatever sonic differences/improvements would have been masked by the limitations of my living room.

[mjb]

The old valve vs. solid state debate has been replaced with Class A/B vs. D scepticism. I know one of the initial problems was filtering the output to get rid of all the swtching crud without effecting the audiable frequency response. This probably gave the first amps a bad name. But, the ICE modules have been around for a while now, and I think they've sorted out most of the early problems in the latest series. I've used Rotel's ICE amps for a couple of years, and couldn't be happier with them.

[bigburner]

I'm still in the process of trying to find where I stand in the Class D vs traditional linear amp debate knowing that the debate may never be put to rest and that both may coexist for many years to come...

...I came across this article: http://www.hificritic.com/downloads/Class-D.pdf.

The two bullet points in that presentation that made the most sense to me were these ones:

* Do not make the mistake of hearing a ‘different’ sound for a ‘better’ sound.

* Human perception is notoriously difficult to quantify, especially when sound quality differences are fairly small. Carefully controlled tests are essential to overcome errors due to expectation, suggestion and prejudice.

Nigel.

[peepaj]

I went from a NAD T773 to rotel ICE amps about 9 months ago and am very happy with them so far.
Jeff

[TommyV]

I stuck with the class A/B amp on my recent upgrade on the advice of my dealer. He said that the bass freq were not there as much on Rotel Class D but class D was immune to low impedance loads. He had no reason to steer me one way or another. I was deciding between the RMB-1075 and RMB-1085 (a sale either way for him). I was leaning toward the 1085 until after I had a long discussion with him. I love the sound of my 1075 but yes it is big, heavy and mean looking. Is that a bad thing?

[ray5]

It probably is a stupid question but I'll ask anyway. Has anyone tried a class D and class a/b in the same system together?
Ray

[TommyV]

I wanted to do just this but my dealer had no loaners and I did not have enough $$ to do the experiment. BTW not a stupid ques at all.

[jalyra]

I stuck with the class A/B amp on my recent upgrade on the advice of my dealer. He said that the bass freq were not there as much on Rotel Class D but class D was immune to low impedance loads.

It was my understanding that class D were better precisely in the low frequencies, and that even some active subs included some class D amps. Are you saying that you liked the class A/B better for the low frequencies? How exactly was the sound different?

[chrispy35]

I've been encouraged by the growing positive feedback here on Rotel's class D models. I came across this article: http://www.hificritic.com/downloads/Class-D.pdf.

Some statements in and aspects of the article immediately raise flags that make me wonder about its credibility:
- class D amps are difficult to measure. Really? What's wrong with the same measurement methods used for class A/B amps?
- below average treble. A flat frequency response to 40 kHz is below average?
- have thermal dissipation limitations due to the small power module size which means that thermally associated dynamic variations are present in the performance with time and temperature. How does this differ from class A/B?

A lot of the technical claims are valid but the article then makes what I would consider logical leaps to attribute SQ deficiencies to those technical aspects of class D designs.

For reference, here is an ICEpower datasheet: http://www.icepower.bang-olufsen.com...asheet_1_1.pdf

Chris P.

[BassThatHz]

"It probably is a stupid question but I'll ask anyway. Has anyone tried a class D and class a/b in the same system together?"

Yes, but why read about it when you can just listen for yourself :P

http://www.youtube.com/watch?v=dDWXcULA6Qk

http://www.youtube.com/watch?v=Kko-pbPfrDM

http://www.youtube.com/watch?v=0kpF5-oy0Og

http://www.youtube.com/watch?v=R5Uu8rJcaMA

http://www.youtube.com/watch?v=rA3RZONH78U

http://www.youtube.com/watch?v=GZ7tbdLLCys

http://www.youtube.com/watch?v=ejMJJ72ixpA

http://www.youtube.com/watch?v=86vGgMTdQFA

Yeah I know its youtube quality, but whatever....

[mjb]

Some statements in and aspects of the article immediately raise flags that make me wonder about its credibility

I thought that too, and the author repeats the same (poor) arguments over and over.

[mjb]

It was my understanding that class D were better precisely in the low frequencies, and that even some active subs included some class D amps.

That is also my understanding.

[Bostonears]

It was my understanding that class D were better precisely in the low frequencies, and that even some active subs included some class D amps.

Many active subs use Class D amps. I think the main reason is because they can generate huge amounts of power in a small package. They don't generate much heat (because their efficiency is so high), and they don't need massive heat sinks. Those factors make Class D amps especially appropriate to build into a speaker cabinet.

[funnycar]

I was able to blind A/B test my 1090 with a Bel Canto s500 for a period of 5 weeks. I went to great lengths to make it a fair test by matching the output levels within 1 dB and keeping the required output levels below the S500's power limits. The acoustic levels were around 75 DB @ 1 meter. The ICE POWER modules failed the very first comparison when the lower mid range became complex. The loss of detail was obvious to ALL who listened. My advice...stick with your class A/B gear for now.

[TommyV]

It was my understanding that class D were better precisely in the low frequencies, and that even some active subs included some class D amps. Are you saying that you liked the class A/B better for the low frequencies? How exactly was the sound different?

I can not contradict that, I only based my decision on the trust of my dealer (he really is a good guy and cares a lot about audio) and actually one post here about someone moving from some previous Class A/B Rotel and then getting a 1560 and thought the bass (or mid bass?) was lacking. I would have to dig to find the thread.

I personally do not have experience in comparing the two so I made my judgment call based on that. I would actually appreciate the extra space and I think the 1085 was $50 cheaper but while he did not say that the 1085 was in anyway a poor amp he made a convincing case for the 1075 so that is the direction I took.

[cfrizz]

Did you have a chance to listen & compare BOTH Tommy? I would trust my ears before I trust a salesman pitch.

Of course he is going to pitch the 1075 since he wants to clear out his old stock before he has to buy the new gear from Rotel.

I read where a LOT of so called audiophiles are simply hung up on the bad class D amps of the old days, that they are not really willing or able to give the new amps a fair shake.

Even with the review done by Audioholics I could easily pick up where the reviewer listened to how well the amp did with the bass line of the music, rather than focusing on how well it did with EVERYTHING. He picked music that featured strong bass lines.

Until these ingrained biases are put aside, I don't think the class D amps will get a fair shake.

The other & more IMPORTANT problem is that Rotel & other companies are taking the technology that SOMEONE ELSE (B & O) developed, putting it in fancy boxes with their name on it, saying that they improved it & charging outrageous amounts of money for it.

Now if the reviewer in Audioholics can be believed, there is VERY little that can be done to these chips & basically nothing that can be done to justify the amount of money that is being asked for.

So the bottom line for me is if these amps give my speakers all the power that they need to operate to their full potential, I'm on board. However, I am NOT willing to spend an arm & leg for just a name on a fancy box.

It's not that I don't want these companies to make money or recoup their R & D costs. But they didn't do the R & D, they took someone elses & try to make it their own.

I stuck with the class A/B amp on my recent upgrade on the advice of my dealer. He said that the bass freq were not there as much on Rotel Class D but class D was immune to low impedance loads. He had no reason to steer me one way or another. I was deciding between the RMB-1075 and RMB-1085 (a sale either way for him). I was leaning toward the 1085 until after I had a long discussion with him. I love the sound of my 1075 but yes it is big, heavy and mean looking. Is that a bad thing?

[btf1980]

I recently purchased a 1085 for my Dad for a really low price from my dealer and he is pleased as punch.

Personally, I don't hear any sonic differences between Class A/B Rotel and Class D Rotel amps. None whatsoever. Maybe I don't have golden ears. :stupid:

[hifiguymi]

I've listened to both types of Rotel amps and have compared the RMB-1075 to the RMB-1077 back to back. While they do sound similar, there are specific differences. The RMB-1077 is a little leaner and faster sounding in the bass. It also does a better job of focus in the soundstage. Instruments and vocals are better defined in space and less diffuse. The RMB-1075 is warmer sounding and has a real easy to listen to character. With some speakers the class A/B amps work better and others the class D. It's just like everything else, it comes down to personal preference.

Eric

[TommyV]

Did you have a chance to listen & compare BOTH Tommy? I would trust my ears before I trust a salesman pitch.

Of course he is going to pitch the 1075 since he wants to clear out his old stock before he has to buy the new gear from Rotel.

Just to be clear my dealer did not have either amp in stock. Both would be a special order.

[watchnerd]

I'm quite delighted with my class D RB-1572. And it's anything but weak in the bass. Quite the opposite, in fact, the control and power in the bass was one of the first things I noticed, along with the immense and effortless dynamic range.

It doesn't get hot, it's light, it's relatively small, and it's the best amp for driving my vintage Martin Logan Sequels I've ever used. It swings current like a mofo and has no problem pumping into the <4 ohms of the Sequel.

[TommyV]

I've listened to both types of Rotel amps and have compared the RMB-1075 to the RMB-1077 back to back. While they do sound similar, there are specific differences. The RMB-1077 is a little leaner and faster sounding in the bass. It also does a better job of focus in the soundstage. Instruments and vocals are better defined in space and less diffuse. The RMB-1075 is warmer sounding and has a real easy to listen to character. With some speakers the class A/B amps work better and others the class D. It's just like everything else, it comes down to personal preference.

Eric

This kind of sums up what my dealer said. Since I already had the 1057 (Class A/B) and loved the sound, I did not want to make a special order on an item and end up regretting it. I am happy with my choice. The 1075 sounds wonderful. It is more detailed and voices are clearer than my 1057. It is also oozing power and bass is great.

I wish I had to money or option to have had both here to compare (1085 and 1075) but he had neither in stock and had sold all demos so he only had 15 series gear on display. I had to pick one or the other and I am extremely pleased with the sound of my 1075.

[Opus007]

Glad you are happy with the 1075 Tommy.I am also very happy with mine.Now if Rotel would hurry up and get my 1069 preamp back to me(having bypass board installed) I would be one happy camper. :T

[TommyV]

I am happy! Soon we will have the same combo! What do you use for interconnects between the pre/pro and amp?

I wish I had your 683s up front! I wonder how the new tweeter would mix with the 600 S3 series tweeter of my center.

Do you have Blu-ray yet? I got the Panasonic BD60 which works perfect with the 1069.

[Opus007]

I am happy! Soon we will have the same combo! What do you use for interconnects between the pre/pro and amp?

I wish I had your 683s up front! I wonder how the new tweeter would mix with the 600 S3 series tweeter of my center.

Do you have Blu-ray yet? I got the Panasonic BD60 which works perfect with the 1069.

See my signature below .. as it lists all current equipment.As for a blu ray player I use the ps3.One of my contacts at the dealer last week was telling me how he had the Panasonic bd55 player and was selling it as he was upgrading to the BD80.He tried to convince me that any of the BD series was a upgrade from the ps3.So I took home a bd80 and gave it a test drive over the weekend.I wanted to really like this player and expected massive improvements over the ps3.Well I could not find them.The ps3 did everything the bd80 did and if there was any noticeable difference...I was just not seeing it. Only thing the bd80 did that the ps3 did not do was bit steam the hd codecs and had multichannel outs and component out which I do not use...the ps3 up converted dvd's the same and blu ray looked the same so I could not justify the purchase.

[TommyV]

I did miss the PS3 in your sig, my apologies. The BD60 is cheaper than the BD80 and does not have the multi-analogs. I did not want the PS3 because : it is loud, uses lots of power, does not have IR control, and is more expensive than my BD 60 (I paid full msrp). From what I have gathered from many sources, the DVD scaling on the BD60 is superior to the PS3 as well but I have not compared them.

I use a harmony remote so IR control is big. I think everyone should have some kind of universal remote or they are missing out big time.

My game system is a 360 which hardly gets any usage.