June 1999 TacT Millennium Digital Amplifier by Robert Jørgensen

"Amplifier of the year -- and perhaps quite a few years to come."

Many SoundStage! readers have been waiting for a review of the TacT Millennium, and taking my emotional gushing in the report from last year's Frankfurt High End ’98 exhibition as well as reports in other publications into account, I can't blame you. But getting a Millennium for review is not a quick process. In spite of real efforts by Peter Lyngdorf of TacT and his cohorts last summer, the number of units available was small, and several magazines had them for tests, making for a decidedly harder time. Perhaps that's an indication of what's to come.

After a few months, I was starting to doubt whether the overpowering experience I had at the High End show was all just in my mind and perhaps a figment of my imagination. Fortunately, I spent a couple of weeks in Denmark in late August and was able to pay a short visit to Toccata Technology, the small engineering company/design team behind the EQUIBIT technology, which forms the basis for the TacT Millennium. I came away from this visit having achieved two things: (1) Having listened for just 15 minutes under less-than-ideal circumstances, I was sure that I had not been imagining things when I waxed so rhapsodically about the Millennium in my report from High End '98; (2) it had been a fine opportunity for a discussion with Lars Risbo, the founder and president of Toccata Technology. In spite of a very tight schedule, he made the time to spend a couple of hours with me, walking through the background of the design, the specific solutions chosen with regard to the many obstacles faced when implementing this technology.

In spite of what we usually associate with PWM or class-D amps, it is decidedly not cheap to implement an animal like the TacT Millennium. The power supply, for instance, has to be very stable, and due to the high-frequency switching involved, extra attention must be paid to not radiate RF noise either inside or outside the Millennium. But I’m getting ahead of myself….

What is the TacT Millennium?

Well, let me start by saying (again) that it is the first of a kind, but it certainly won't be the last. Very briefly, it is a class-D or Pulse Width Modulation (PWM) amplifier driven directly from a digital signal. What is so special about this? The concept of class-D amplifiers or PWM is not new. Quite a few companies have made such products before, but the problem associated with them has always been a sharply rising amount of distortion with rising frequency. That’s the reason that with only a few exceptions you don't find any designs in the audiophile arena. The biggest problems lie in sampling the signal and creating the different width pulses used to switch a steady voltage on the output. Most implementations have suffered from substantial levels of distortion created during this conversion.

Well, Toccata Technology, whose designs lie at the heart of the TacT Millennium, have found not only an effective way around this problem, but also one so elegant that it must warm your heart if you have the least affinity for the overall technology and the clever application of it. Through signal processing, the PCM signal is converted and pre-shaped into the pulses of varying width that will form the output of the amplifier. This is a basic difference with other forms of amplification. Instead of outputting a signal of varying voltage, the PWM amplifier outputs a series of pulses of varying width but of steady voltage. These pulses are the filtered by a low-pass filter in order to make them into a musical signal. You need to switch the voltage, in the Millennium's case a maximum of 58 volts, at a relatively high frequency, otherwise reproduction really suffers (and that was a major problem in earlier PWM amps). In the case of the Millennium, this done at 352.8kHz, and the low-pass filter sets in at a comparatively mild 60kHz with 12dB-per-octave roll-off.

But if you output a steady voltage, how do you handle the volume? Not without reason have digital volume controls been looked upon with suspicion. You actually need an awful lot of bits to implement them without a very real loss of resolution. Well again, TacT has come up with a very clever solution. Since the output voltage is fixed from the power supply during replay, they simply vary the power-supply voltage to the output stage. Thus, the volume control is not in the signal path at all. Neat.

Did you catch the real implication of all this? There is no amplification, as we know it traditionally, involved at all. The signal stays in the digital domain all the way up to the filter, which folds the PWM signal back into an analog feed for the speakers.

There is so much to say that I could go on for a very long time. Compared to the work of other manufacturers, there is a surprising lack of hocus-pocus and arm-waving involved with the TacT Millennium, and this is thoroughly refreshing.

Physical description

Weighing in at over 70 pounds, the Millennium is an impressively heavy device. The chassis is milled from blocks of aluminum, which together with a substantial cover and bottom plate of sheet aluminum provide a very stable base as well as protection from stray RF noise. This is, of course, important since there is a lot of high-frequency stuff going on inside and the requirements for this sort of control have been raised severely in the European Union. This is probably not such a bad thing, although it has certain amplifier designers pulling their hair out.

The most eye-catching feature is the Cyclopean eye on the front containing the Millennium's display, with the ring around it being a superbly executed volume control. This is hung in dual ball-race bearings, giving the smoothest operation you have ever felt. Of course, you are not forced to use the manual volume control. The remote control will do as well. Until now a preliminary NAD remote has been shipped, with which I am not on so friendly terms, but a reworked and very tasty TacT remote is in the works, and all buyers are promised one when it appears.

The Millennium is equipped with a rather small number of controls on its sparse front panel. If ever you could talk about cool Scandinavian design, this must be it. Three buttons have been sunk into the front plate. A larger one on the left-hand side is the main power switch, and on both sides of the big eye you find analog and digital input selectors. The analog inputs are not really available yet but will be with the forthcoming analog-input module. The digital selector gives access to the four digital inputs found on the back of the Millennium, one of which is a special Clock-Gate input providing the means for locking the clock-rate of the CD-drive to the clock-rate of Millennium. I have been playing the Millennium with an inexpensive NAD CD player modified for output of its digital signal via Clock-Gate. This has not been bettered by any of the much more expensive drives I have had connected.

How does it sound?

Let me start out by confirming that I fell in love with the Millennium fast and hard during my first exposure to it in Frankfurt. By the time I arrived home, I was so starry-eyed that my wife's immediate reaction was "How much is that going to cost"? Isn't she a dear? I've mentioned above that as a couple of months had gone by, I started to entertain some doubts as to the depth of my feelings, but the visit to Toccata Technology and having lived with the Millennium for a couple of months now have made things very clear. I have so many times sat down to do some listening and found that all thoughts of analysis have evaporated. That's how enticing the Millennium is.

In most of the areas where the Millennium stands out it's not so much the perceived frequency performance that sets it apart. It's something much more exciting, at least for me. First and foremost, the Millennium makes music as if it is being played right in front of you. You might say, "I have had this experience with really good systems before." I don't doubt that for a minute -- so have I (or I thought so at least). The TacT Millennium, though, reproduces a musical event in such a real manner (I know this sounds old already, but what can I say?) that time after time it excites me to no end. What creates this effect for me?

It certainly has something to do with a lack of hash or noise -- call it what you will -- that seems to be present below the level of easy awareness when listening to other systems. The awareness only arises when I then listen to the Millennium -- and don’t hear what I’m talking about. Suddenly something quite intangible but nonetheless disturbing is gone. It's like some blanket of whiteness that seems present in most, if not all, other systems disappears. Everything sounds decidedly less like hi-fi reproduction and more like a live performance. Alternatively, you could say that notes arise out of a pitch-black darkness that does pretty outstanding job of simulating live music being played.

At the same time you observe a richness of detail that in no way resembles the sound of other amplification devices, where a little lift here and a little dip there conspires to fool you into believing that you are presented with more detail. Conveying the full force of this experience comes with difficulty, and I have found myself simply forgetting to listen and instead just flowing along with the music

It cannot come as a surprise that excellent recordings like Janis Ian's Breaking Silence [Analogue Productions ANLG-0000027], which is superbly natural in its presentation to begin with, now literally invites you to believe that she is present with all the musicians in an enlarged version of your living room stretching quite a few meters out behind the speakers. Classical works where the scale and scope are very large are presented in a way that time after time makes me say to myself that I have never heard anything like this outside of a concert hall. I have allowed Pomp & Pipes [Reference Recordings REF-0000058] the full run of the house and never has the Millennium seemed the least bit belabored or stressed.

I'm sorry if anybody should feel that I have gone completely to town in my enthusiasm. I suppose I have done so, but let me declare that it is not blindly. My only excuse is that I honestly feel quite compelled to express my very real enthusiasm. Quite a few friends, relatives and others who have experienced the Millennium have been left stunned at the realistic presentation. Several people of the non-audiophile variety have commented on how this sounded so much like live music.

Another CD that has had me in rapture is A Toda Cuba Le Gusta by the Afro-Cuban All Stars [Nonesuch 79476], which is a companion recording to the superb Buena Vista Social Club [Nonesuch 79478] with Ry Cooder and a number of brilliant Cuban musicians. The full force of the horn section comes across as sharp, but never artificially so. It’s so right!

The spectral balance is indeed excellent (with the right speakers). This goes for most amplifiers of course, but I will attempt to clarify what I mean. Two things have kept me busy in this area. The first one, and I have not really been able to ascertain to my complete satisfaction whether it is really a "but," is the bass. Compared to other high-quality amps, the Millennium does not seem to have the rock-solid bottom of, for instance, the Sirius D200 or other amps with a similar grunt factor.

The reason I'm loath to brand this as a weakness is that I also find the bass remarkably agile with excellent definition and speed. This sort of terminology drives some people up the wall, so I presume one could also talk about well-defined transients and no overhang. My initial reaction was to count the bass as weaker than other parts of the presentation, but after living with it for several months I'm almost sure that is not the case. Then again, I might just have grown used to it. The fact, though, is that I have never been able to follow the bass line on "Way Down Deep" from Jennifer Warnes' The Hunter [Private Music 82089] as well as I can with the Millennium and the Dali Grand Diva speakers. Also, the Grand Organ on several of the Jean Guillou recordings on Dorian like the Saint-Saëns Third Symphony [Dorian DOR-90200] and Mussorgsky’s Pictures at an Exhibition [Dorian DOR-90117] come across with both verve and majesty.

The second "but" that applies is the fact that the treble response is dependent on the impedance of the speaker. Because the output is coupled via the second-order filter at 60kHz, the actual load of the speaker connected cannot help but become part of the filter function. If the speaker impedance is around 6 ohms, then the Millennium is ruler straight. If it is 8 ohms, the response is up by 0.3dB at 20kHz, at 16 ohms a tad under 1dB, but at 2 ohms will leave the output more than 3dB down. This is certainly no worse than a lot of single-ended tube amps, and TacT's point is that this is easily corrected with a bit of (dare I say digital) equalization.

The fact is that not every speaker sounds wonderful with the Millennium. My trusty old Rogers LS 3/5a sounded very thin, which I suppose (and it's my best shot since they are not defective) could be traced back to their 15-ohm impedance. Otherwise, most speakers I have tried showed pretty much their basic character with a slightly varying final result. A pair of B&W 803s played better than they ever had. So did my old ribbon-hybrids, which do tend to lack some sparkle up top. Another lovely combination was made with a pair of Martin-Logan Sequel 2s that have been retrofitted with SL3 panels.

The best speaker/amp combination in this house was achieved with the beautiful Dali Grand Diva, which I shamefully underestimated in my Frankfurt report. It turned out to be a much better speaker than I had expected, not just with Millennium. I hope to provide you with a separate report on this. Another speaker that I have just heard fleetingly is the B&W Nautilus 802, which showed tremendous promise together with the Millennium.

Truth is, the Millennium plays so cleanly and with no discernible distortion products that it leaves all other amplification far behind. It's more than the proverbial "open window." You can simply listen so much more deeply into the recording space as well as details of the mixing and mastering. But the Millennium is never sharp or tizzy, but some listeners may feel that it does not provide the warmth that they heard with other amplifier/speaker/room combinations. Of course, this means that as with all amplifiers, you must look out for the right combination of source, amplifier, speaker and room.

I feel that it is quite possible to find a speaker that complements the Millennium’s undeniable strengths to such a degree that the combination still is miles ahead of anything else I have heard in 30 years of audiophilia. The Dali Grand Diva is a case in point, but the short listen I had with a B&W Nautilus 802 makes me think this might be even better.

Conclusion

It is not just that I really can't find fault with the TacT Millennium. It truly provides me with greater insight into the music and an experience of being present where the music is played. In the Millennium’s design, compromises have been made, as in all human endeavors, but they are made with knowledge and insight. I applaud the designers.

From a technology point of view, its conceptual elegance continues to woo me as no other device in years has done, and although you can be certain that it will not remain the only one of its kind for that long, it has been built to last a long time. Peter Lyngdorf goes out of his way to explain that the Millennium has been made in such a modular manner that it can be upgraded and live on for a goodly number of years, providing its owners with a more than a fair investment. The first of these upgrades has been announced as a very reasonably priced Mk II iteration, allowing (among other things) the Millennium to play as much as 10dB louder, which will be welcome in the case of some CDs that have mastered at relatively low levels. SoundStage! will be publishing a follow-up review soon. Further upgrades accepting 24-bit/96kHz directly as well as perhaps DSD are looming on the horizon, so the fun is not over yet.

While $9800 is not in any way peanuts, if you add up the prices of an upper-echelon high-end DAC, preamp and power amp, you will not have any difficulty at all in passing this amount. So I suppose in a certain way you can still say that the Millennium is excellent value for money. In case any doubt persists, let me state clearly that I consider the TacT Millennium a true milestone product both in terms of technology and performance, and I can without hesitation nominate it as my amplifier of the year -- and perhaps quite a few years to come.

...Robert Jørgensen
robert@soundstage.com

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