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Old 27th December 2005, 01:40 AM   #1
MarkZ is offline MarkZ  United States
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Default Seeking a "pure digital amplifier" ...

I am at a distinct disadvantage in not having an electrical/electronic engineering degree. Nor do I have much of an electronics hobbyist background (I do have an engineering degree, but am not a EE.) So be patient with me.

Anyway, I am looking around for a "pure digital amplifier" for my audio system. I define a "pure digital amplifier" as one which takes, as input, an S/PDIF (or similar digital signal) and during amplification no internal conversion to analog takes place except at the very final PWM stage feeding the speakers.

It is difficult for me to ascertain whether an advertised "digital amplifier" is a pure digital amplifier, or is some kind of analog/digital hybrid. Even if a "digital amplifier" has S/PDIF inputs, this does not guarantee it is a "pure digital amplifier."

I believe the Tact Audio digital amplifiers are pure digital, but they are fairly pricey. Who else makes audiophile (and near-audiophile) grade "pure digital amplifiers? Are there any that don't break the bank? Also, does there exist a DIY schematic or kit to build a high-end pure digital amplifier? Or are such things still something "in the future"?

My interest in a "pure digital amplifier" was whetted when, for Christmas, Santa delivered a Slim Devices SqueezeBox 3. I'd like to go "all digital" and use its digital out to go directly into a pure digital amplifier. For what it's worth in this discussion, my current speakers are Vandersteen 2's, which are not exactly efficient, so the "pure digital amplifier" needs to have enough oomph to effortlessly drive the Vandies at loud volume in a typical living room setting.

Thanks in advance for your feedback.

Mark
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Old 27th December 2005, 02:35 AM   #2
john65b is offline john65b  United States
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Default Fully Digital Receiver

For a quick foray into Digital Amps for not-so-much-cash, you can pick up a Panasonic SA-XR series 6.1 HT receiver. I have the SA-XR25, SA-XR45 and SA-XR50. They are FULLY DIGITAL, cheap (most likely under $200 on ebay), and well worth the $$. Or you can pick up the newer model SA-XR55 and SA-XR70 for around $300.

My SA-XR45 is hooked up to my inefficient 4 ohm 86db/watt Magnepan MMG's and I am very happy with the sound - no (and I mean NO) Noise Floor, dynamic and crisp sound. Perferct fo HT too because dialog comes in crystal clear.

Many receivers claim Fully Digital, but if the DAC is done BEFORE Amplification, then it is NOT fully Digital...only the amps that amplify DIGITAL signal is truely Fully Digital, like the Panasonic. Hell, it says so right on the front of the receiver.

What have you got to lose? Buy a SA-XR50 on eBay (I would go for the XR45, then XR50, and lastly th XR25). You no like the sound, you sell it back on AUDIOGON and you will make a buck or two!

BTW, two years ago I laughed at the thought of selling my trusted and EXPENSIVE Carver Amp/Preamp for a chinsy Panasonic receiver. I was plesantly surprised and wound up with a heap of cash left over. I got to wondering if Audiophilia has strayed from the pursuit of sonic perfection to snob apeal. I won't wow any audio purist talking about my Panasonic Receiver, but again they don't have to know its a Panasonic.
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Old 27th December 2005, 02:44 PM   #3
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Ohnoes! Here we go again with the Oxymoron of the century, "Digitital Amplification".
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Old 27th December 2005, 03:39 PM   #4
badman is offline badman  United States
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Default Re: Fully Digital Receiver

Quote:
Originally posted by john65b

Many receivers claim Fully Digital, but if the DAC is done BEFORE Amplification, then it is NOT fully Digital...only the amps that amplify DIGITAL signal is truely Fully Digital, like the Panasonic. Hell, it says so right on the front of the receiver.

The idea of a digital amplifier has been discussed to death around here. A little searching would reveal Bruno Putzeys (one of the premier class D designers) explaining why class D isn't digital. Some amps move the DAC extremely close to the output stage, but it's still by nature an analog output stage.

Oh, and I'm a big fan of Class D, some class D stuff makes very good amps indeed!
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Old 27th December 2005, 04:25 PM   #5
rha61 is offline rha61  France
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yes the saxr45 with some little mods ( power caps of course ! ) is a very good amp
it seems that the saxr55 is better , it has special caps ( water caps...), it can parallel the output stages or bi amplify

alain
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Old 27th December 2005, 04:29 PM   #6
MarkZ is offline MarkZ  United States
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Default O.k., how about a "power DAC"?

In defining "digital amplification", I suppose it's a semantic issue, with a little bit of "politics" thrown in for good measure.

Anyway, maybe the better term for "pure digital amplifier" would be a "power DAC", where the signal remains in the digital domain until the very last stage where the digital signal is converted to analog with sufficient power to drive speakers. Is this more correct terminology?

So, what brands/models of amplifiers fall into this category? It'd be nice if someone knowledgeable in this area would put together a complete list, along with links to reviews and related information.

Again, thanks!

Mark
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Old 27th December 2005, 05:40 PM   #7
rha61 is offline rha61  France
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Default Re: O.k., how about a "power DAC"?

Quote:
Originally posted by MarkZ
In defining "digital amplification", I suppose it's a semantic issue, with a little bit of "politics" thrown in for good measure.

Anyway, maybe the better term for "pure digital amplifier" would be a "power DAC", where the signal remains in the digital domain until the very last stage where the digital signal is converted to analog with sufficient power to drive speakers. Is this more correct terminology?

So, what brands/models of amplifiers fall into this category? It'd be nice if someone knowledgeable in this area would put together a complete list, along with links to reviews and related information.

Again, thanks!

Mark
if you call the Tact S/M2150 a digital amplifier , the saxr are digital because they use the same Texas Instrument Equibit chips (tas5182)(digital to PWM control ), the main difference is the power supply , linear fot Tact and switchingPSU for Panasonic

alain
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Old 27th December 2005, 08:41 PM   #8
bob123 is offline bob123  United Kingdom
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While on the subject of pure digital amplifiers i was just messing about with good old crocclips and i came up with what is essentail a pure digital amplifier, It is basicaly a ADC with a power output stage but the signal remains digital until it gets to the speaker.

in my simultions it seems to work but i dont know if it would in real life.
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Old 27th December 2005, 09:20 PM   #9
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How about this old Sharp sota model?

http://sharp-world.com/products/1-bi...100/index.html

http://www.hometheaterhifi.com/volum...mp-1-2002.html

(if you can still find it, you probably still have to break the piggy bank)
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Old 27th December 2005, 11:25 PM   #10
Pano is offline Pano  United States
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Quote:
Originally posted by bob123
i was just messing about with good old crocclips and i came up with what is essentail a pure digital amplifier,
Interesting idea, Bob. I tried to build something similar about 10 years ago, but it had ultrasonic transducers for each bit/channel. Never could get it to work right.

The idea was to use the air as the low pass filter / intergrator with drivers that were optimised for one, and only one, signal level and frequency. Nice idea, but I could never get it to work.

Is anyone else doing the sort of amp Bob came up with?
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