[Detroyt]

Hi.............I am a newbie here , so please go careful on me .

1) What is the best multi channel class "D " Digital amp out there right now ?

2) Do Sony still do digital amplification ? if not what was the last one of their top of their line ?

Regards Barry

[andy1249]

With Class D the "D" does not stand for digital , the amp is not digital , its well explained here ,

What is Class-D amplification?

The benefits of Class D amplification are more efficiency for less weight , but you should not be buying an amp based on its electronic configuration , you should be buying on how it sounds.
The configuration should only interest the likes of Electronic Engineers like me , buyers should be interested in the results , not how they are arrived at.

[Welwynnick]

Originally Posted by andy1249

With Class D the "D" does not stand for digital , the amp is not digital , its well explained here ,

What is Class-D amplification?

As usual, I beg to differ. :-(

Anyway, Sony have made a few good digital amplifiers. I've owned or used five or six class D amplifiers, and my current one is the TA-DA9000ES, which sounds the best. The most popular class D amps are based on B&O ICEPower modules - used by Pioneer and Rotel in particular. Onkyo make some good class D amps, and NAD are getting in on the game pretty seriously, too. Many people say great things about the NuForce amplifiers, but they are quite controversial. Many of the best reviews seem to be reserved for the UcD amps.

But like Andy says, there's good and bad class D as well as Class A/B. Chose on benefits, not solutions.

Nick

[Gadgetcity]

Originally Posted by welwynnick

As usual, I beg to differ. :-(

Out of curiosity, what don't you agree with?
It might help Detroyt make a better informed decision if he understands what Class D actually refers to, its benefits and compromises, and whether or not he really wants to know what the "best class D amp" is. He may change his question to "best performing amp for the money" instead.

[Davieboy00]

Originally Posted by Detroyt

Hi.............I am a newbie here , so please go careful on me .

1) What is the best multi channel class "D " Digital amp out there right now ?

Not sure about "best" as I have little experience with class D amplification but managed a quick listen to the Rotel RMB1565 and it sounded pretty good to me. An improvement over the older Rotel stuff.

[andy1249]

Some more information here , this time from a designer ,

The Truth About Digital (Class D) Amplifiers — Reviews and News from Audioholics

His quote ,

Firstly I'd like to point out that "digital amps" is a misnomer. There are two categories:

Analog-controlled class D. Switching amplifiers with an analog input signal and an analog control system. Normally some degree of feedback error correction is present.

Digitally controlled class D. Amplifiers with a digitally generated control that switches a power stage. No error control is present. Those that do have an error control can be shown to be topologically equivalent to an analog-controlled class D with a DAC in front.

I put the word controlled in bold myself , this is the source of the " mistake " made by many in calling class D " digital " , there are many kinds of switching power circuits , just because there is a square wave involved does not make the circuit digital.

Information on this topic is plentiful , use google if you need more , should you ever decide to study the subject , the Academic world will not entertain the idea of Class D being called a Digital amp , that term applied to that configuration is misleading at best.

In terms of buying a good amp , if your going class D , note that most class D designs are sub par cheap as chips models that dont stand up very well to their more linear counterparts. You have to spend a large amount of money before you come across well designed Class D amplifiers.

[Welwynnick]

Originally Posted by Gadgetcity

Out of curiosity, what don't you agree with?

Its a matter of semantics.

It simply depends on what you mean by "digital amp".

Nick

[Welwynnick]

Originally Posted by andy1249

Some more information here , this time from a designer ,

The Truth About Digital (Class D) Amplifiers — Reviews and News from Audioholics

Its my firm belief that a lot of the "definitive information" out there is largely regurgitated marketing techno-babble. Bruno Putzys, however, along with Karsten Nielson, is one of the World's authorities on class D. However, both men have commercial interests in analogue controlled switching amplifiers, and it helps to understand where information comes from.

Switching amplifiers started with a poor reputation for sound quality because of the early applications in portable, automotive, low-frequency and low-power equipment. Manufacturers therefore go to great lengths approaching indoctrination to dissociate their switching amplifiers from what has gone before.

They have gotten a lot better, but the debate rages about whether linear or switching amplifers sound best. I shan't enter into that - I've made my choice and I'm no longer interested in burdening anyone else with my opinions - but amplifier class isn't the deciding factor. Just because something is class A or class Z doesn't mean it sounds any good.

Nick

[recruit]

I am a complete convert and love what class D amps can do, especially when you consider how efficient they are, sound wise more or less perfect to my ears, the ICE modules seem to be the most popular and also the prefered type of class D amps availible, I always had class A/B but not anymore...the Rotel 1575 is a very good example of how good they really are...and can sound.

[Medrep1]

Im tempted to buy more to add to my existing multichannel amp, but im not sure which route is best, another 1575, or additional 1572's etc etc

Ive heard whispers Rotel are going to be launching a new class a/b?? multichannel amp soon, so may hang on to see what thats all about first?

I have a Rotel 1572 driving a pair of Focal 816W floorstanders (826Ws as soon as they are replaced...) and the amp can handle anything thrown at it without a problem. Clean sound, good bass (which some critisise Class D for) and overall working well.

[Richard from USA]

Was posting about a preamp but couldn't resist jumping in here. First, I won't qualify myself as an engineer but rather, one that spends my time - day in and day out - with some very talented folks. Also, class D amplification is something we have been experimenting/utilizing for years. We have implemented a few designs as well as backed away from some returning to class A/B amplification. We currently have three class D home theater amplifiers in the works but chances are only one or two will see the light of day. Here are my overall perceptions.

Class D amplifiers are promising because they are extremely efficient. Power used is converted to sound (good or bad sound) and excess heat is limited. This makes the costs of controlling chassis temperature less expensive. As for the power consumption issue, I doubt any of us are paying that much per Kilo Watt ... yet.

We have gone to and stepped back from this technology on the multi-room level because even though our design sounded very good for class D, class A/B blew it away - especially at low power levels (background music). Also, in a multi-room system, often you need more than a pair of speakers per zone and a drawback we have experienced with class D is that distortion goes up dramatically as impedance goes down.

Our current engineering is toying with class D but for high-power home theater use and subwoofer amplification (as THD isn't that critical here). We have gotten one unit to sound nearly as good as our PTM 150 series class A-A/B amplifiers.....NEARLY. What is dramatic is the form factor - a 1RU chassis vs. a 3RU chassis and power output vs. consumption.

As others have noted, how something sounds to you should be the ultimate test, not a specification or design scheme. As for my feelings about class D, the technology is getting better but it isn't there just yet. Note that I make these comments as a manufacturer, not a consumer with a budget or design issues.

[Gadgetcity]

Originally Posted by welwynnick

Its a matter of semantics.

It simply depends on what you mean by "digital amp".

Nick

I see, Class D does not mean "digital amp" although I can see the appeal of sticking digital in front of something to make it sound 'better'.

There are however some excellent, digitally controlled, Class D amps out there, and digitally controlled Class A, Class AB, Class C and others I'm sure.

Being 'digital' doesn't make them any better, it is just an implementation choice. The amp output actually wants to be as analogue as possible!

but amplifier class isn't the deciding factor. Just because something is class A or class Z doesn't mean it sounds any good.

Now you're talking. Spot on.

[Welwynnick]

Originally Posted by Gadgetcity

I see, Class D does not mean "digital amp" although I can see the appeal of sticking digital in front of something to make it sound 'better'.

D isn't short for digital; its just the next letter in the sequence A, B, C ....

As it happens, class D amplifiers are switching amplifiers, and the output from the high-power output transistors is either on or off, so I don’t think we can say that class D means “not digital”.

The distinction between digital and analogue controlled switching is a fine one, and insignificant in my mind. The difference is that the on-time of the switching pulses is controlled digitally. So with digital sources you have the opportunity to eliminate a pair of D to A and an A to D conversion stages. In my experience that’s a good trade for doing without a negative feedback loop or two.

Many manufacturers cling to the analogue class D moniker to persuade people that that they sound better, yet the things that work against class D are still there with analogue control switching. I’ve had a variety of both analogue and digital control switching amps, and guess – the highly-reviewed “analogue” class D amps don’t actually sound better!

Nick

[andy1249]

As it happens, class D amplifiers are switching amplifiers, and the output from the high-power output transistors is either on or off, so I don’t think we can say that class D means “not digital”.

Yes we can , thats just the point , there are plenty of circuits that use high power switching as an alternative to linear. Likewise there are plenty of circuits that use PWM signals for purposes other than carrying data.

Just because the circuit uses high power switching it should not be labeled digital , just as a switch mode power supply is not labeled a Digital power supply a class D amp should not be labeled "digital " as this directly leads to the misinterpretation of data carrying signals and the benefit that such signals bring.

Labelling a Class D amplifier a " Digital" amplifier makes no sense because a Class D amplifier can be analog through and through and calling it digital misleads the layman down the mistaken path of assuming such an amplifier is immune to analog limitations in much the same way as most data carrying digital circuits, which of course , they most definitely are not.

It is wrong , its misleading , and is very bad practice.

[Welwynnick]

Originally Posted by andy1249

Labelling a Class D amplifier a " Digital" amplifier makes no sense because a Class D amplifier can be analog through and through and calling it digital misleads the layman down the mistaken path of assuming such an amplifier is immune to analog limitations in much the same way as most data carrying digital circuits, which of course , they most definitely are not.

But not as much as referring to an analogue-controlled switching amplifier as "analogue class D" makes him think its immune to the limitations of class D.

[Medrep1]

Can I ask a potentially daft question?

With regards to class D, and the way it 'delivers' its power vs a typical class A/B design with a large toroidal transformer, are there limitations in either design with regards to peak output and current?

For example, if you were to place a demanding load on a class D amp, would its reserve power be as capable as a class A/B configuration.

I am considering more class d amps to help power my 5 speakers, but am trying to figure out if class D has any limitations vs other designs.

Also, generally speaking, what are the usual signs of a class D and a class a/b amp reaching its limitations, aside the obvoius clipping?

Thanks

[Welwynnick]

Class D does have some possible advantages here.

Because they are more efficient as class A/B, they draw less power from the power supply, so the same power supply will go further with class D. Since the cost and weight of the power supply and the heat sinks are so significant, this allows the designer to tilt the balance of compromises in favour of power delivery.

Secondly, class D amps often have switch-mode power supplies, and these can be the dominant factor in performance. These have quite different characteristics to linear supplies. My impression is that they allow the amp to work better as an ideal voltge source - doubling power with halving impedance - up to a point. Then they give up supplying any more power. So ICEPower amps for example can be very load-tolerant, as long as you don't use them on really bad loads at very high volume.,

Nick

[Medrep1]

Thank you for the reply.

Im still trying to get my head around the class d concept. The amp (1575) never really gives any clues as to when im pushing my luck, until it just clips and goes into protection mode. This hasnt happened for many months though, and I seem to give in now before the amp does, it gets very very loud

Because of the absence of any tell tale signs of power limitations, its difficult to gauge what extra performance a dedicated 2ch class d amp (i.e. 1572) could do for me?

Guess im just going to have to try?

[UFN]

Originally Posted by welwynnick

Secondly, class D amps often have switch-mode power supplies, and these can be the dominant factor in performance. These have quite different characteristics to linear supplies. My impression is that they allow the amp to work better as an ideal voltge source - doubling power with halving impedance - up to a point. Then they give up supplying any more power. So ICEPower amps for example can be very load-tolerant, as long as you don't use them on really bad loads at very high volume.,

You can overload a normal transformer quite badly and all that happens is that it will get a little warmer. If you are drawing continuous power in an industrial application this can be a problem, but in a typical audio application where the energy content of the signal is typically only between 1/8th and 1/3rd of full power, it means this will never really be a problem and you can get by with a much smaller transformer for the same level of performance.
On the other hand, once you hit the current limit on a typical SMPS, it will clip very hard and give you bad distortion on the output of the amp. However, as long as you stay within the limits of the design, the SMPS should indeed behave very well.

/U.

[Medrep1]

However, as long as you stay within the limits of the design, the SMPS should indeed behave very well

How do you tell though where the safe limit is?

I am tempted to buy x2 additional stereo class d amps, one for each main L&R speaker. I am trying to gauge whether this would give me performance/dynamics etc etc comparable to say something like a Bryston 4BSST for example? Speakers are B&W 803D.

Edit: to be more clear,
Option A) 2x250 8ohm, 500w 4ohm Class D, one amp for each speaker, essentially biamping, or
Option B) 2x300 8ohm, 500w 4ohm Bryston 4BSST, one amp for the L&R speaker.

Ive seen the Bryston's 2nd hand going for around £1800ish, the Rotels new would be around £1500, and would match tonally and aesthetically.

[Welwynnick]

I would go for the Brystons, unless you can the Rotels much cheaper - just for sound quality.

Nick

[Medrep1]

I hope this isnt too off topic sorry......

Just spent the last couple of hours doing some A/B comparisons biamping my centre speaker with the class D amp. Ive tried the mains in the past, but no longer have a spare Y splitter to try again. Unfortunately with the centre speaker, the differences are slight to my ears, and this is cranking up to volume levels I am just about comfortable with? I recall a similar experience with the mains, but it was a long time ago.

If I had to guess, i'd say the sound was a touch less bright biamped, and I think the bass is a bit more authorative? For HT i'd probably not be able to tell at all?

On this basis, I dont think ill be buying more of the same to biamp?

Thanks for the input.