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Positive Feedback ISSUE 69
Burson Timekeeper Power Amplifier (or even two…)
What is this: it's small, silver and loud? If your answer was Burson, you got it right. However, for a component to be just small and loud is no feat in this day and age. Hence, if you replaced Burson with any other name, you also got it right. To get 100 Watts and more from a tiny amp is no big deal now, thanks to Class D design and integrated switched-mode power supplies. It's enough to mention Audiomatus, a Polish manufacturer whose mighty power amplifiers I once reviewed, including the 500-watt AM500 (see HERE). This excellent inexpensive amplifier turned out to be based on the ICEPower modules from Bang & Olufsen, modified in Poland. Its dimensions resembled what we see unpacking the Timekeeper from Burson. With the front panel half the width of a studio rack, the amplifier was quite low and not very deep or heavy. It was the steel enclosure that largely contributed to its weight.
Such level of miniaturization in high-end audio equipment has been made possible by advances in Class D amplifier design, in which power transistors are either fully "on" or fully "off". Since low signal level periods constitute a large part of music, Class D amplifier power transistors remain "off" most of the time, in which state they do not conduct current and hence do not heat up. This in turns means that they do not require expensive, large, heavy heat sinks that dissipate heat in conventional amplifier designs. It also means a significant cost saving, as large heat sinks simply come at a premium.
The other component that is often associated with Class D is a switched-mode power supply. That is not a strict rule, though. The first known Class D amplifiers from TacT used linear power supply, and the best—in my opinion—currently available units manufactured by Japanese SPEC Corporation are powered by a heavy toroidal transformer and capacitor bank. However, the ICEPower modules mentioned above are small PCBs that house both the amplifier and switched power supply. This is another area that allows for cost and space savings. The transformer used in such power supply is tiny as instead of mains frequency, i.e. 50 or 60Hz, it operates at several times higher frequencies (even hundreds of kHz), which means high voltages and low currents. And low weight. All these advantages are currently utilized by many manufacturers that offer really great designs of this type, from the cheapest entry-level amplifiers through to true high-end.
The above paragraph has been written with one intention—to demonstrate that a cool amp can be designed this way or another. What's important is to be consistent in this and try to develop a given technology and to advance the so-called state of knowledge. The Burson Timekeeper is different than what I wrote above—its gain path includes no integrated circuit (an integrated modulator, usually PWM, is mandatory in Class D), the output stage is in Class AB, the power supply is classic and the power output is high. In spite of all that, the amplifier is small—its dimensions are 265mm x 250mm x 80mm.
It may be small but is very solidly built. The entire enclosure is made of aluminum. Its side panels are heat sinks, rather small for the power they need to dissipate. They heat up considerably during playback, as does the entire enclosure that is used to heat sink the output transistors. When we look at the rear panel it turns out that passive cooling is aided by a small fan mounted inside. I could not hear it during the auditions. The manufacturer explains that the fan is microprocessor controlled and only goes on in really extreme cases, such as in "sunny California". The fan stays idle over 95 percent of time. Efficient cooling is ensured by a specially redesigned enclosure that sports several dozen screws less compared to the previous generation design. The whole enclosure is a unified heat sink that acts like a compact block of aluminum. It consists of four aluminum plates, up to 6 mm thick—top, bottom, front and back (no, it's not a bent metal sheet) and heat sinks that play the role of side panels. Their small fins are corrugated to increase dissipation surface.
The front panel only sports a small blue LED and deep milled manufacturer's logo. As customary for a power amplifier, the rear panel is not overly crowded. It features a pair of RCA input connectors and a single XLR input connector. A word of explanation: the Timekeeper is a stereo amplifier with asymmetric topology and as such is driven through RCA inputs. However, it can also operate as a monoblock in bridged mode, with each channels forming one branch of the symmetric topology. Then it uses the XLR input. If our source or preamplifier is not equipped with XLR outputs, we can connect it to one of the RCA inputs. The input signal is first symmetrized before further processing takes place.
The gold input connectors are really solid. So are the speaker terminals. Below the XLR connector is a selector to switch between the XLR and RCA inputs and the Bridge mode. There is also an IEC mains socket with a mechanical power-off switch. The unit rests on small feet made of aluminum with rubber hemispheres. I know this solution from many audio components manufactured in China, such as those from Xindak.
The electronic circuit is mounted on three main and one auxiliary printed boards. While opening the unit to get to them, we will be pleased to look at the solid plates that make up the enclosure and their precise assembly.
Right in the center we have the power supply. At its core is a large 300W toroidal transformer housed in a metal can for EMI shielding. The single transformer sports five secondary windings, and hence five separate power supplies. Apparently, the left and right channel input and output stages and the auxiliary circuits are powered separately. Power supply capacitors provide the total capacitance of 40,000μF. The output stage boards are bolted to the heat sinks. Quality passive components are used throughout, with different types of Wima polypropylene capacitors as well as Elna Silmic II electrolytic caps and another, equally good, Elna series. Some of precision resistors are from Dale. Each channel sports two pairs of output transistors in parallel. The whole looks fantastic.
This circuit design has been carefully improved over many years. It started with a FET (Field Effect Transistor) based input stage, but during the work on the Soloist headphone amplifier / preamplifier six months were spent to develop a symmetric bipolar transistor input stage. Further comparison, however, proved that the new bipolar input resulted in a bland, lifeless midrange. The project was therefore abandoned. The Timekeeper actually employs bipolar transistors, but only in the voltage gain stage. Apparently, Burson designers managed to reach a balance between the superb tonality of FETs and the greater dynamics and resolution of bipolars. FETs are used in the input stage, both in the RCA bridge mode symmetrizing circuit and as input buffers. The Burson is capable of operating in two modes. In stereo mode it provides 2 x 80W (8Ω) which goes up to a whopping 240-watt continuous (8Ω; 270W/4 Ω) and 300-watt peak power in monoblock bridge mode!
The rear panel reveals that its full name is Timekeeper Power Amp, Model No. PA-160, and that it was designed by Burson Audio Melbourne. There is no information about where it was made, but a careful look at the unit and at its price makes it clear that it had to be China. It is evident by some enclosure parts, including the characteristic feet and speaker terminals as well as sandblasted radiators, not to be confused with anything else.
The testing had a character of an A/B comparison with the A and B known, where A constituted the Soulution 710 and the Jeff Rowland 625 (see HERE) power amplifiers. Additionally, I used the SPEC RSA-V1 (see HERE) integrated amplifier. I also used three different pairs of speakers: the Harbeth M40.1, Divine Acoustics Proxima (New) and Castle Richmond Anniversary Edition. The preamplifier was the Ayon Audio Polaris III [Custom Version], connected via the Acoustic Revive RCA-2.0PA interconnect (stereo mode) or the Acoustic Revive XLR-2.0PA II (dual-mono). Speaker cables were the Acoustic Revive SPC-PA. The system was powered via two Oyaide GPX-R power cords plugged directly into a dedicated power line in the wall. The amplifiers sat on the M3X-1921 RD anti-vibration platform from Harmonic Resolution Systems - (see HERE).
Albums auditioned during this review
• Ariel Ramirez, Misa Criolla, José Carreras, Philips/Lasting Impression Music LIM K2HD 040, K2HD Mastering, "24 Gold Direct-from-Master Edition UDM", CD-R (1964/2009), see HERE .
• Puccini, Tosca, Maria Callas, Georges Prêtre, Orchestre de la Société Des Concerts du Conservatoire, EMI/Esoteric ESSE-90079, "Esoteric 25th Anniversary", SACD/CD (1965/2012).
• The Oscar Peterson Trio, We Get Request, Verve/Lasting Impression Music LIM K2HD 032, K2HD Mastering, "24 Gold Direct-from-Master Edition UDM", CD-R (1964/2009), see HERE.
• Et Cetera, Et Cetera, Global Records/Long Hair LHC00071, CD (1971/2008).
• Foreigner, Inside Information, Atlantic Records/Warner Music Japan WPCR12566, "Atlantic 60th", CD (1987/2007).
• Savage, Tonight, Extravaganza Publishing/Klub80 Records CD001, "25th Anniversary Limited Edition No59/150, CD (1984/2009).
• Hilary Hahn, Hilary Hahn Plays Bach, "Best Classics 100", Sony Classical/Sony Music Japan Entertainment SICC 30087, 2 x Blu-spec2 CD (1997/2012).
The Australian amplifiers are characterized by specific technical solutions that result from the manufacturer's preferred approach. It includes the refusal to use integrated circuits, the choice of Class AB over Class D output stage, the use of linear power supply and very expensive, superbly-made enclosure. The same can be said about their sound: it is "made up" in a way that is fairly easy to notice. Selecting albums and listening to the amplifier and—then—two amplifiers paired with various speakers, I could almost see a smile of satisfaction on designers' faces, when they'd sat down in front of speakers with a beer in hand, getting ready for a long "sit-down" night. Their satisfaction came from a well done job—they got what they wanted.
I assume that stereo mode is the basic operation mode of this amplifier. That means we need a single unit for an audition and that was how I conducted the first part of my review. Ultimately, however, Burson people had rather envisaged a system consisting of two monoblocks, with each stereo amplifier working in bridge mode as a fully balanced unit, and driving one speaker. Hence, the second part of the review was devoted to this case. The audition results proved very interesting and not as black and white as one might have initially thought.
Timekeeper Stereo Mode
I think that without long deliberation, after a few tracks one can say that the amplifier coming from Down Under favors beauty over truth. Of course, as long as these notions are—philosophically—different for us. They are not identical in audio, and I think that the very first step to take in designing any product is the choice of direction to go. One can choose the "truth", or in other words the pursuit of lowest possible coloration and the flattest frequency response, as well as the most "neutral" tonality. It is a good track to follow and I know many components of this type that sound insanely good, taking the listener as close to the performers as possible. That is the sound of the Soulution 710 power amplifier and the Bakoon Products HPA21 headphone amplifier, both part of my reference system. But there is another way that is based on specific euphony, on well-selected distribution of distortion (thus agreeing with its inevitability), modeling the sound so that it meets OUR expectations, not necessarily synonymous with the best measurement results. And such components can also sound spectacular, to name for example Kondo amplifiers (Audio Note Japan), and the Ayon Polaris III [Custom Version] preamplifier and Leben CS300 XS [Custom Version] headphone amplifier in my system. I assume that the more expensive the gear, the closer the two asymptotes are. Reaching perfection (only temporary, of course, and available to us at the given moment) we stop paying attention to HOW it is done. The lower the price list, however, the more they diverge and the harder we need to think what WE expect of our audio system.
As I said, the Timekeeper has its distinct "personality". It is, of course, the vision of its designer and its implementation, but I find it easier to anthropomorphize the product and have it within arm's reach. The amplifier under review has its tonal balance shifted quite low, to upper bass. No, the treble is not missing; there is as much of it as needed to convey the texture of cymbals or wind instruments, or the harmonics creating unique violin sound. I listened with special attention to Hilary Hahn playing Bach's Partitas and the album (in the Blu-spec CD2 release) sounded beautiful, bringing to view violin timbre and its surrounding acoustic, but also large space in which the recording was made. It's just that the listener's attention is focused lower. This way we get a solemn, dense and mature sound. All the albums I listened to sounded at least good and some were spectacular. Some of them have their weaknesses exposed by more analytical, brighter amplifiers, and are not as pleasant in listening. It is a paradox, but in audio it is sometimes better to hear less than more, provided there is some idea behind it. Here the idea is clear and consistently executed.
The album that sounded best was Savage's Tonight, which is not really the first choice of an educated, seasoned jazz or classical music lover. Italo disco has a rather poor reputation in the music world, but what the heck. For me, music is associated with memories of a particular album, of specific tracks. Savage is my early youth, first discos and girls. Damian Lipinski (VinylMagic.pl) who produced the latest 32-bit remaster of that album has done a really great job. Even the original vinyl does not—in my opinion—sound as good as the CD. I have a unique numbered edition signed by Savage and listen to it quite often. On the Burson amplifier it was smooth and vivid, with proper bass "grunt". Treble had sweet tonality, without any discernible trace of harshness that appear on the album from time to time. But the most important thing was that the Australian amplifier made it easy for me to bring back memories and to recall how I'd used to listen to these tracks at home on a reel-to-reel tape recorder and tube amplifier. It was as if all the problems of the source material had disappeared, as if they'd had no significance. It comes at a price, but it's worth it!
Last but not least, I got a strong, deep and boosted bass. In absolute terms, against my reference amplifier and other best amplifiers I know, Timekeeper's bass is emphasized and there is lots of it. That does not affect the overall reception but it clearly directs it. We start listening to the bass guitar, double bass, and bass drum kicks. It's quite cool and many systems do not allow that, instead focusing our attention on small details. But I repeat, there is abundance of bass. Perhaps it was the reason why electric guitar recordings, notorious for being dry and thinned out, here sounded so well. The 1971 album Et Cetera by the krautrock band Et Cetera proved to be a unique performance. German jazz-rock experiments are close to my heart for many reasons, and Et Cetera explores every one last of them. Its intelligent, multi-layered music has not become at all dated and with each listen sounds as interesting as the first time. The problem of early krautrock recordings is their sound quality. Et Cetera is different in that it shows great dynamics, outstanding treble and meaty guitars. It so happens that the Timekeeper holds exactly the same "cards". Consequently, I got a large soundstage and momentum, strong deep bass and fantastic cymbals—sweet, but well-positioned on the soundstage and combined with the rest of the frequency band through a kind of "fluid".
Timekeeper Bridge Mode
Switching from stereo mode to dual-mono is as easy as having a good pint on a hot afternoon and brings an equally intense sensory experience. We take another Burson out of the box, once again being impressed by its design quality and appreciating its weight. We put it next to the unit we already used and start by disconnecting all cables. Just as a safety precaution. Then we connect our interconnects either to the balanced input—only active in bridge mode—or to the left RCA input (white), and hook up the speaker cables to the top two speaker terminals. The latter are properly marked and identifying the "hot" (+) and "cold" (-) terminal should pose no problem. Actually, in bridge mode they are both "hot" (in reference to ground). And finally, two identical and best quality power cords—a necessary expense. This way we have a whole new system.
The sound will be significantly different. All within certain limits, naturally, as it's still a Timekeeper, yet music presentation from two monoblocks is different than from a single stereo unit. Their tripled output wattage seems to open up a door in our mind that is labeled "power" understood as thundering bass, huge dynamics, and gut punch. Anyone who had some experience with high-end amplifiers knows it's rubbish. If that's what happens and if doubling the power output only results in those sonic characteristics, we'd better pull out the power cord from the wall, spin the amplifier round over our head and smash it against the wall. That will save us a lot of time. Shame to waste it on crap. Most listening takes place within the first few watts, anyway. Yet additional headroom, provided it is properly managed, gives us something completely unique with any type of speakers, regardless of their sensitivity.
The Timekeeper shows what it's really about: the sound has more life to it, is better differentiated and simply more resolving. Not in the sense of being more detailed, though—that's not the point. If we listen to the fantastic release of Oscar Peterson Trio's We Get Request prepared by Mr. Winston Ma (Ultimate Disc Collector's Edition), burned on a gold CD-R from high resolution audio files stored on a hard drive, with negligible block errors, we will hear that the cymbals are now clearer; that the double bass (sometimes bowed) has a more distinct "body" and that the underlying bass drum beat, surprisingly seldom so well audible, is an important part of the presentation. Generally, it is "more, stronger and deeper." But we will understand it as a better detailness only if we focus on it. If we approach the audition without such an assumption, everything I've mentioned translates into a better vividness and differentiation. Showing how various albums have been recorded, revealing differences in their miking-up technique, tonality and dynamics is, after all, part of what differentiation is. A single Timekeeper does it pretty well, at a really high quality. Yet when it must choose between pretty and faithful sound, it goes for the former. It is not quite capable of sounding both pretty and faithful, at least not on the level of more expensive amplifiers. Two Timekeepers are much better in this regard. The amp duo brings deeper soundstaging that—for example—results in a great perspective when listening to Puccini's "Tosca" performed by Maria Callas, as well as incomparable "breath" or air of the church where Ramirez's "Misa Criolla" with José Carreras was recorded.
Bass delivery changes, too. Previously, there was lots of bass which was not particularly differentiated. It was not annoyingly boomy or sloppy, but there was no breakthrough in terms of its definition, either. Now, without emphasizing the attack, we get a better differentiated bass range and much better treble imaging, with more substantial, weighty and natural cymbals.
Small, silver and sounds loud—many of the current amplifiers can be described this way. The Timekeeper stands out from the crowd with its very good mechanical and electrical design, and an interesting, engaging way of playing music. Aimed at keeping the listener happy, by refining the recordings where necessary while being forgiving of their shortcomings and flaws it allows to listen comfortably to any album. This way it meets all the basic requirements expected of an amplifier in this price range. Its tonality is geared towards the mid and upper bass, yet not at the cost of withdrawn treble. The dynamics is very good, as is the bass extension. A single amplifier in stereo mode already brings a lot of fun. However, adding another unit to operate in bridge mode changes the perspective—the sound is much more mature and "free" (in the sense of "freedom" from pressure, stress and muffling), with a deep breath. Bass definition and soundstage depth are improved. The price for that, however, is a slightly poorer midrange, and hence vocals, definition. The difference is not large but is important to know about—there is nothing for free. I have learnt that from many other components that allow bridge mode, which usually results in a similar midrange modification. The advantages, however, are much more important and "weightier". You can start with a single Timekeeper, then later buy another—it is really worth it. In terms of tonality and dynamics the Australian unit resembles Japanese SPEC amplifiers, and that is great news. Small, silver and sounds great? You got it, the correct answer is two Burson amplifiers.
THD: (1khz @ 8 Ohm) 0.03%
Price: $2600 each