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johnny p.
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Pure-Digital Amplifiers

Though available for the past 14 years, there has been very little discussion of pure-digital amplifiers. These are essentially DACs with built-in volume control and sufficient power to drive loudspeakers. One reason for this absence was that very few companies produced them. TacT was the only one from 1998 to 2005 (with their "Millennium" & 2150 amps). Then Lyngdorf came in - but this brand was simply a split from TacT. These co. used the same DSP-algorithms but had different power supplies, etc. so produced different sound. The TacT was favorably reviewed in Europe and the U.S.

Elsewhere, Wadia had their PowerDAC - but it cost a small fortune, was gigantic in size and (probably) due to this, was never reviewed in the press. It was discontinued less than 2 years after it came out.

Sharp and Yamaha had pure digital amps (which were reviewed) but they seemed to have a problem with PCM inputs. As a result, the reviewers used analog inputs, from either LP or CD. This produced an extra conversion, which probably hurt the sound in the end. These were also discontinued.

More recently, many in our community thought that the Behold and Devialet integrateds were all-digital. A closer look reveals they aren't. Behold simply does the DSP in the digital domain, before D/A conversion while the Devialet combines separate analog components in one chassis.

So we're left with TacT, Lyngdorf and two newer entries - NAD an Core Audio. The NAD has been raved in the press, while Core's units are just coming out (and are the first all-digitals to use a linear power supply).

When the TacT came out, some must have thought that analog separates would die off. But few expected these designs would improve so dramatically - look at the latest Ayre, MBL and Constellation gear, for example. The rise of analog switching amps also confused things, as they looked like a better idea than (pure) digital-switching. The sheer number of them for one, but also that these co.'s bad-mouthed their "pure" cousins on technology - and seemed to get away with it. (Their claims that pure-digitals have decimation errors and "can't use feedback" have been overcome, as of late).

Analog interconnects, too, might be gone - despite their dramatic improvement since the TacT.

So - an all-new product category. But it's really our old playback system, greatly simplified. Is the future all-digital ? Or will analog separates continue to improve while their price drops ? I'd say that our separates have a lot of work to do - if they're going to match pure-digital's S/N ratio and cost competitiveness. In his review of the NAD M2, JA stated that it "competed with the best separates". This, at roughly 1/10th the cost.

With pure-digitals (finally) off and running, I believe this concept could be a boon to high-end audio. They offer a fantastic one-box alternate to the high cost, large size and (still) not-perfect-sounding analog separates which have pervaded audio since the 1960s. They make it much more attractive for average folks to become an "audiophile".

Who would have thought that a format war would erupt amongst our (entire) playback system ?!!

jackfish
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Is it "pure digital" if the end product of its output

is an amplified analog signal being fed to the loudspeakers?

johnny p.
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Yes - because they amplify in

Yes - because they amplify in the digital domain.

J.Manrique
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I'm amazed why this technology doesn't take off

I had the chance to set up and listen to a Sonus Faber Guarneri Homage + NAD C 390DD and it blowed my mind, the amount of detail, lack of noise, transient response and dynamics was surprising.

The article is missing some makers like sumoh tinyamps based on TI chips, as well as HFX RipAmp

http://www.hfx.at/index.php?option=com_content&view=article&id=376&Itemid=185

http://www.sumoh.dk/

 

both desings come from the same place:

 

http://www.dxco.dk/

gadgety
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Reasons Digital Amps haven't taken over the world yet

Tact had the Millennium out in 1998. That's as you say 14 years ago. Then there was the RCS and later RCS 2.2x, the Room Correction preamp, which included a x/o to subs. It was incredible value for money. After a delay the 2150, the son of Millennium amp was out. In fact it was more advanced, but much cheaper in a less stunning visual package than the Millennium. Stereophile at the time only reviewed the RCS. Amazingly they never pulled together the RCS to audition with either the Millennium or the 2150. It was done by Scandiavian audio magazine High Fidelity who conceded it was the most transparent sound they had ever heard. They thoroughly tested and measured it as well. I believe Hifi News did some testing as well. After another few years there was the 2150XDM with built in room correction, that didn't even need a pc attached to measure the room response and program the filters, and the filter could be changed on a fly. Never saw that tested in Stereophile, or in TAS. I find that amazing, because it was just incredible value for money and should have made the cover of both magazines, in my opinion. Here are my top 5 reasons why Tact and digital amplification didn't break through:

#1 Lack of knowledgeable distribution/channels who know how to demo the product. Even Lyngdorf, who owns his own distribution network in Scandinavia couldn't get his staff to demo and sell Tact convincingly.

#2 An aging and shrinking target population who a) care about sound quality rather than convenience (streamed mp3s that the growing segment of audio consumers appreciate) b) don't understand computers or the complexity of computerized pre amp and ampc) are conservative - these generations (I'm on the verge of it) have been brought up on analog audio, and interpret new digital products from an analog viewpoint.

#3 The growth segment in audio was in home theaters audio/visual. Tact went for that as well, but the home theater room correction amp was the most pricey product, was delayed, quite complex and didn't have Firewire input. I think they ran out of capital to pay all the licenses. I e undercapitalized and in a non growing segment.

#4 At the same time, Texas Instruments bought the technology ip and went for the mass market. They have good chips out there, but naturally they seem to focus on volume and lowering cost rather than tweaking the hell out of the PCM-PWM chips. Suddenly there were cheap amps, such as Panasonic's XR range with highly similar chips out as the way more expensive Tact amps. These amps weren't as carefully engineered but may have brought the wrong aura to digital amps as "affordable", making the Tacts seem overpriced.

#5 Power struggle internally in Tact eventually leading to a split up, where Lyngdorf the marketing man, split from Boz, the engineer. They lost a lot of time in this. And momey. It seems Boz, who kept the Tact brand hasn't been able to sell and market his stuff quite convincingly, and with too small an organisation around him, temporary staff, high staff turnover, resulting in poor customer service, despite him being extremely dedicated. My personal belief is he misjudged what it would take to sell this new technology. Simply having a superior product is not sufficient, as high end audio is a lot of packaging and mumbo jumbo.

Finally, as a closing comment, digital amps may still prevail. When companies like NAD bring out a product like this, which also looks like decent value, although in my view nothing beats the Tact M2150XDM which brings everything the NAD brings, PLUS room correction... for less money. The NAD C390DD is cheaper, but doesn't have the same power, nor the room correction. What the NADs do have, though is a bigger name from a stable player in the audio scene.

mrvco
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I think some of the problem

I think some of the problem is that at first look, at least after looking at the NAD unit, it appears to be a rather mundane looking $2,500+ integrated amplifier with a built-in DAC and lot of spin from the marketing department.  To warm the market up to this technology I'd probably start with a more modest unit targeted at the second-system / desktop / headphone amplifier market.

tmsorosk
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Pure Digital

Pure Digital , isn't that an oxymoron?

gadgety
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Digital amps - and who does the marketing spin?
mrvco wrote:

I think some of the problem is that at first look, at least after looking at the NAD unit, it appears to be a rather mundane looking $2,500+ integrated amplifier with a built-in DAC and lot of spin from the marketing department. 

 

 

No, the NAD unit is a Power-DAC. At its base it's using Zetex/CSR chip. That is an all digital class amplifier. The only analog is at the speaker output terminals. What evidence to you have that this is an integrated amp with a built-in dac, i e implying its a conventional DAC followed by an amplifier?

Kjeldsen
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digital or not

The main difference is if the PWM signal i generated digital og analog. If a class d powerstage can ever be digital is not an easy task to determine. You can't define the signal to a digital word. But, experts i digital transmission do not really agree that digital have to be defined as words. I don't care, but I have heard a lot of both analog and digital controlled class D. One similarity with digital controlled class d, is how detailed and relaxed a digital source can be. I find complex recordings easier to listen to with digital controlled class D amplifier.

By the way, TACT Milennium is also with at linear power supply so Core is not the first.

My references (only amps I know really well)

Analog: TACT 2175/Linear PSU, CAD audio CAD400S/SMPS PSU, Connexelectronic NXP8950TH/Linear PSU, Arjen Helder Tripath 2024/SMPS PSU

Digital: TACT Millenium MrkII/Linear PSU, Panasonic SA-XR50/SMPS PSU, MiniAMP/SMPS PSU

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