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what is a "Digital Amplifier" and why should we care?

1152 Views 19 Replies 10 Participants Last post by Clepto, Oct 4, 2006

aag

Discussion Starter · Oct 2, 2006

I would be exceedingly grateful to anybody who would take the time + effort of defining, in layman's - yet physically precise - terms, what exactly is a "digital amplifier".

I know that there is a mammoth thread out there with some 7K posts, yet I wasn't able to find a simple and clear definition. Consequently, I still do not quite understand the usage of the term "digital" in this context.

Digital Amps are said to be much smaller than conventional amps. What makes an integrated amp "big" is typically its power stage. However, as loudspeakers cannot be fed a bitstream, wouldn't any power stage have by necessity to be located downstream of a Digital/Analog Converter - and therefore be entirely analog?

...

If the above were true, I can only imagine that "digital" refers to the preamp section - which however is not what makes "non-digital" high-end amplifiers so monstruous...

Hence i am fully at loss here! I find the topic interesting, but I fail to understand it. Anybody cares to help?

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1 - 20 of 20 Posts

cschang

· #2 · Oct 2, 2006

"digital" is a bit of a misnomer. What you want is "class D".

Here is a starter for you:
http://www.answers.com/topic/class-d-amplifier

ehlarson

· #3 · Oct 2, 2006

You can tell a digital amp because the power switch has a 0 and 1 on it.

Clepto

· #4 · Oct 3, 2006

As for the why should we care portion, digital (class d) amps are nearly 2x as efficient as their a/b bretheren...

If a typical amp is 60% efficient, then a comparable class d amp might be 95% efficient... which means less power drawn, and less heat... Not to mention occupying less space/weight.

i.e. a 100% efficient amp would be able to convert all the electricity it draws to amplification, with no heat generation.

zan789

· #5 · Oct 3, 2006

There are also Class-T digital amps as well as some interesting designs like Sunfire and Jeff Rowland, which may qualify as digital switching amps.

SiriuslyCold

· #6 · Oct 3, 2006

Quote:

Originally Posted by ehlarson
You can tell a digital amp because the power switch has a 0 and 1 on it.

ROFL!

anyway PS Audio has a nice analogy in their explanation

cschang

· #7 · Oct 3, 2006

Quote:

Originally Posted by zan789
There are also Class-T digital amps as well as some interesting designs like Sunfire and Jeff Rowland, which may qualify as digital switching amps.

As far as I know, Jeff Roland uses ICEpower modules.

SiriuslyCold

· #8 · Oct 3, 2006

and Sunfire is class-H

Felgar

· #9 · Oct 3, 2006

Aag, it also might help to research SACD, because it works in a very similar way from what I understand. Both the audio format and the amplifier output are working to replicate the original analog waveform (just at different power levels), and both do it in basically the same way.

aag

Discussion Starter · #10 · Oct 3, 2006

thank you to all for these informative links. I now have a much clearer understanding. I still do not see why reproducing waveforms by digital pulse modulation would lead to higher thermal efficiency - but then I do not really need to know, as long as that's true...

I now have a 6-yr old Yamaha behemoth which has given me a lot of disappointments (the ultimate of which may well end up beind a slipped disk when I will finally get rid of it...).

So, which D-class AV receiver (or amplifier) would you recommend? I am prepared to spend serious money (well, let's say up to 4000 US$) if it's worth it. I don't care about exterior design (it will go into a cabinet) but the technology should be really state-of-the-art. One feature that I dream of, e.g., would be IP-addressable, LAN-switchable inputs.

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EJRothman

· #11 · Oct 3, 2006

Quote:

Originally Posted by aag
thank you to all for these informative links. I now have a much clearer understanding. I still do not see why reproducing waveforms by digital pulse modulation would lead to higher thermal efficiency - but then I do not really need to know, as long as that's true...

I now have a 6-yr old Yamaha behemoth which has given me a lot of disappointments (the ultimate of which may well end up beind a slipped disk when I will finally get rid of it...).

So, which D-class AV receiver (or amplifier) would you recommend? I am prepared to spend serious money (well, let's say up to 4000 US$) if it's worth it. I don't care about exterior design (it will go into a cabinet) but the technology should be really state-of-the-art. One feature that I dream of, e.g., would be IP-addressable, LAN-switchable inputs.

I'm not one to speak to digital receivers in that price range (a good class-D amp in a much lower price range is the Panasonic SA-XR57), but if you have that much money to spend you would be much better served sound-wise to get better speakers than a new receiver. If you already have very expensive speakers ($10k range), then it might make sense to buy a receiver in this price range. If you have more modest speakers it is foolish, in my opinion, to spend that much money on a receiver.

-Eric

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aag

Discussion Starter · #12 · Oct 3, 2006

Eric: your point is - of course - very well-taken. My speaker setup consists of 5 Magnepans (two very large ones for fronts, smaller ones for rears, and an arc-like Magnepan center), and two Velodyne digital drive subwoofers. The total cost of the loudspeakers is, indeed, in the range of approx. 10'000 US$.

This doesn't mean, however, that I feel any urge to throw $$$ out of the window! If the Panasonic SA-XR57 is the best D-class amp around, I shall gladly buy it and use the rest of my budget for other nice things...

Clepto

· #13 · Oct 3, 2006

I just picked up a Rotel RMB-1077... it's a 7-channel, 7x100 model... They also have digital mono and stereo models. The 7x100 can drive nearly anything, so if you can get a demo of them on some hard to drive speakers, you might be pleasantly surprised.

The 1077 runs $2500

hhcibtpaun

· #14 · Oct 3, 2006

I went with the NHT Power5.....

Mike

SiriuslyCold

· #15 · Oct 3, 2006

wonder why Rotel doesn't do a 200Wx7 ICEPowered amp - most people seeking power amplification would tend to go higher than 100W per channel

aag, there aren't many class-D receivers around for the amount of power needed for maggies all around. You might want to check out Sony's 7100ES (100x7 into 8Ω) but it is, like your Yamaha, a behemoth.

of the current crop - HK seems to have dropped its DPR line, Kenwood's defunct, only JVC and Panasonic remain. Samsung announced an ICEpowered receiver in your price range but dropped it before it even surfaced.

The Panasonic XR57 is an excellent little receiver for under $300 - plus if you run it in 5.1 mode it will automatically use the surround back channel amps to power the fronts. That having said I'm not sure it will have enough (100x7 into 6Ω) to feed 5 Maggies. Perhaps Clepto's Rotel 1077 has a better chance

have no clue as to pricing but ThetaDigital's Virtu PowerDAC looks interesting

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Felgar

· #16 · Oct 3, 2006

Aag, just be absolutely sure to audition and compare your purchase. A normal $4000 amp can be absolutely amazing and although possible, I don't see it as probable that a Class D amp at 10% the cost can compare. But if you do make some very detailed comparisions I'd love to hear them!

SiriuslyCold

· #17 · Oct 3, 2006

also check out some of these other class-D power amps

dsmith901

· #18 · Oct 3, 2006

Here is a good article that will clear up some of the misunderstandings about digital amps:

http://www.audioholics.com/techtips/...mplifiers.html

And if that is not enough here is a whole page of articles on amps for you to peruse, including many on digital and Class D amps.

http://www.ecoustics.com/Home/Home_A...fier_Articles/

EJRothman

· #19 · Oct 3, 2006

Given your setup, I think that separates are the way to go. Those speakers need power and I don't think getting a receiver to power them is as good a solution as separate amps with a pre-pro. That said I know nothing about separates, but I'm sure others do!

Clepto

· #20 · Oct 4, 2006

Quote:

Originally Posted by SiriuslyCold
wonder why Rotel doesn't do a 200Wx7 ICEPowered amp - most people seeking power amplification would tend to go higher than 100W per channel

I think if you're talking 4ohm speakers, the 100x7 ends up doing 200x7... But yeah, 200x7 into 8ohms would have been nice.

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