Pureaudio Vinyl Phono

Transcript

ON TEST PureAudio Vinyl Phono preamplifier B eing based in earthquake-prone New Zealand, the founders of PureAudio (Gary Morrison and Ross Stevens) were probably too busy getting their company up and running to pay much attention to goings-on elsewhere the world, so they likely had no idea that the name ‘Pure Audio’ was going to be used by Universal Music Group to describe a new digital format (High Fidelity Pure Audio) or that Imagination Technologies already had a range of audio products branded ‘Pure’… or that there is retailer on Queensland’s Gold Coast called 40 Australian PureAudio (plus a recording studio in the USA). So if you think you’ve heard the name before, be advised that PureAudio (NZ) has nothing to do with any of these identicallynamed enterprises. However, if you think you’ve heard the names of the two founders of PureAudio (NZ) before, you’d be exactly right, because Gary Morrison worked at Plinius for 18 years as co-owner and head designer, and before that was the founder, owner and designer at Craft Audio before it merged with Plinius in 1987. Co-founder Ross Stevens has been an industrial designer for more than a quarter of a century, during which time he’s worked with such design luminaries as Philippe Starck and designed for B&W and Plinius, so you will have heard his name and seen and heard dozens of high-end hi-fi components that he’s designed. The naming confusion continues with the name of product under review here, because phono preamplifiers are always used to amplify the signal from vinyl LPs, so calling a product a ‘Vinyl Phono Preamplifier’ seems to me to be tautological. PureAudio Vinyl Phono Preamplifier But whatever you call it, PureAudio’s Vinyl Phono Preamplifier is (at least for the present) only the third product available from PureAudio, the other two being a stereo preamplifier and a monobloc power amplifier, both of which are styled along the same lines as the Vinyl Phono Preamplifier. The Equipment When the PureAudio’s Vinyl Phono Preamp arrived, the box was so large—and so heavy— that I thought that local distributor Cameron Pope, of Krispy Audio, had sent me PureAudio’s preamplifier instead. But no, when I’d removed the packaging, I was looking at the Vinyl Phono Preamp… and looking with my mouth agape. It’s impressively big. And the industrial design is drop-dead gorgeous… even if it does remind me of some sound reinforcement products that were around back in the 40s and 50s. As you can see from our photograph, the footprint of this preamp find that the Vinyl Phono Preamplifier has no ‘Standby’ mode, and most particularly so since the mains power switch is located on the rear panel. This means that if you put the PureAudio in an equipment rack, you’ll have a long way to reach around the back to turn the mains power on and off. The rear panel is where all the action is, and our photograph seems to speak for itself, but if you look at the cartridge loading DIP switches, you would be forgiven for thinking that there are only five possible resistance loadings (as the DIP switches show 1kΩ, 470Ω, 220Ω, 100Ω and 47Ω, the first switch being for capacitance, with the ‘down’ position loading the input with 200pF.) In fact, many more resistance loadings than this are possible, because if more than one switch is used, the indicated loads are paralleled, so that if, for example, you put both the 470Ω and 100Ω DIP switches down, your phono cartridge will see a load of 82Ω. If you then Look inside and you’ll see a printed circuit board that’s absolutely loaded with state-of-the-art resistors, capacitors, ICs and transistors... is far from conventional, being far, far deeper than it is wide. In fact the PureAudio is 210mm wide, 115mm high and fully 410mm deep. It also weighs 7.0kg, so you can see how I’d confuse it with a preamplifier. (Well at least any ordinary preamplifier, PureAudio’s own preamplifier weighs nearly twice as much!). As you can see, the front panel is bare save for a single vertical bar that serves to show the operational status of the Vinyl Phono Preamplifier: your choice of ‘On’ or ‘Off’. Actually, it’s a bit more than this because out-of-the-box, the front panel light is actually switched via signal-sensing. When the amplifier is on, the front panel light comes on and will stay on until you start playing music, upon which the light will go off. (PureAudio tells me that its research showed that customers prefer not to have distracting lights on when they’re listening to music.) This sounded like a perfectly good arrangement to me but if, contrary to the research findings, you would prefer the light to stay on, you can arrange this to happen quite easily: do-it-yourself instructions (no soldering required) are provided in the ‘Quickstart’ instructions. I was a little disconcerted to also flick the 47Ω DIP switch down, your cartridge will now see a load of 30Ω. PureAudio publishes a table of 20 possible load values on its website, but fails to give the underlying mathematical equation that would let you easily find a load that best-matches your cartridge yourself. I’d recommend you use one of the many parallel-resistance calculators available on the Internet. The one here [www.1728.org/ resistrs.htm] can do up to 10 resistors, so it can calculate every combination for the six resistors in PureAudio’s DIP switch array. With all switches up, the load is 47kΩ, so this is the maximum loading possible, since paralleling the lower-value resistors will always reduce resistance. However, if you can’t find a combination that gives you an exact match for your particular phono cartridge, you can (for a small additional charge) custom-order a Vinyl Phono Preamplifier with this exact loading factory-installed. I was a bit surprised to find there was no MM/MC switch, but apparently there’s no need of one, because the gain of the PureAudio—combined with its high overload margin—means it can handle both cartridge types without the ON TEST requirement for a switch. I was also surprised to find that the nuts holding the RCA input and output connectors are gold-plated, but the RCA terminals themselves are not. Presumably this is not a case of cost-cutting, so Morrison must have his reasons for not using gold-plated connectors. If you pop the case of the PureAudio (though I do not recommend you do this, because there are dangerous voltages inside) you’ll see a printed circuit board that’s absolutely loaded with state-of-the-art resistors, capacitors, ICs and transistors, giving an instant reason for the high asking price. PureAudio Vinyl Phono preAmplifier Brand: PureAudio Model: Vinyl Phono Preamplifier Category: Phono Preamplifier RRP: $3,250 Warranty: One Year Distributor: Krispy Audio Pty Ltd Address: PO Box 82 Berowra Heights NSW 2082 (04) 1196 8902 (02) 8006 4666 [email protected] www.krispyaudio.com.au • Superb sonics • Very high gain • Customisable • No standby mode • Power switch location • Limited capacitance adjustment LAB REPORT Readers interested in a full technical appraisal of the performance of the PureAudio Vinyl Phono Preamplifier should continue on and read the LABORATORY REPORT published on page 114. Readers should note that the results mentioned in the report, tabulated in performance charts and/ or displayed using graphs and/or photographs should be construed as applying only to the specific sample tested. Lab Report on page 114 avhub.com.au 41 ON TEST PureAudio Vinyl Phono Preamplifier But when you’re doing this, consider that you are looking at only ONE CHANNEL of the circuit. Underneath the PCB you can see is another, identical, PCB for the other channel. PureAudio has certainly spared no expense on components! The exterior casing, where it’s not stainless steel mesh, is 5mm thick alloy that appears to have been sandblasted, and has a finish that makes it look diamond-encrusted. It looks absolutely fabulous in the flesh (our photograph doesn’t do it justice) but it could, I suspect, be a little tricky to keep spotlessly clean… In Use and Listening Sessions I was a huge fan of Morrison from ‘way back in his Craft days, and also when he was at Plinius, so I was expecting great things of his PureAudio Vinyl Phono Preamplifier, and I was not disappointed. The dynamics were incredible… indeed I think this is the very first thing I noticed when I started listening. I trialled my most dynamic LPs, including precious test discs, and never once was the PureAudio the limiting factor… indeed I’d go so far as to say that you will never find any LP that will even approach the PureAudio VPP’s dynamic capabilities, even if you try some of the best direct-to-disc or half-speed mastered ones. In this regard (and several others I’ll come to in a moment) the PureAudio is in a class of its own. Tonally, the PureAudio was cleaner than any other phono stage I’ve heard, with a beautifully sweet, pristine delivery of the audio signal, particularly across the midrange and up into the high frequencies. Although I would be the first to admit that I am partial to valved phono preamplifiers, I’d also be the first to admit that they can colour the midrange and high frequency sound with nuances that, whilst beautiful-sounding, embellish what’s on the LP, creating a signal that really wasn’t there in the first place. The PureAudio, on the other hand, delivered the sound trapped in the groove perfectly, without adding any ‘colour’ of its own, but at the same time still sounded beautiful, simply thanks to its superb neutrality. What you will find almost inexplicable is that it does this so easily, particularly in the extreme highs, where the transparency is astounding. The only downside of this transparency is that it also enables you to hear the tiniest and highest-frequency details captured in the vinyl, so that if your stylus mistracks even the slightest smidgeon, you’ll hear it instantly. Stereo imaging was glorious. The PureAudio was able to provide maximal separation between the two channels—exceeding the capabilities of the LP format to deliver it—but at the same time it maintained the imaging ability that seems to be the sole domain of vinyl. Digital delivery of audio can provide better channel separation than vinyl, and better level matching between the stereo channels, but stereo itself is an aural illusion, something that ‘tricks’ the human ear and, for whatever reason, the stereo signal from LP seems to trick the ear more convincingly than the stereo signal from digital, which is one reason for vinyl’s enduring popularity with audiophiles. Deep bass was excellent: it was obvious that PureAudio had correctly implemented the RIAA curve, and it replayed perfectly my two usual test LPs for deep bass: Pink Floyd’s Dark Side of the Moon and Emerson, Lake and Palmer’s Tarkus. It also delivered outstanding performance delivering the cannon shots on Telarc’s original much-lauded LP version of Tchaikovsky’s 1812 Overture, one of which is at 38Hz. (The cannons actually sound better on vinyl by virtue of the CD version being clipped, as shown by Stephen Dawson here: http://hifi-writer.com/wpblog/?p=2504). This particular LP was Telarc’s best-selling recording. It sold more than 800,000 copies and is, thankfully, still available (for around $50) on the First Impression Music label. There are, however, few phono cartridges that can successfully track the cannon shots! Conclusion PureAudio’s Vinyl Phono Preamplifier combines exquisitely-realised musicality with the unerring accuracy that only a solid-state phono preamp can deliver and delivers it in a package that is at the cutting edge of modern greg borrowman industrial design. CONTINUED ON PAGE 114 PureAudio’s Vinyl Phono Preamplifier combines exquisitely-realised musicality with unerring accuracy 42 Australian LAB REPORT PureAudio Vinyl Phono Preamplifier CONTINUED FROM PAGE 42 Laboratory Test Results Newport Test Labs’ bench tests of the PureAudio Vinyl Phono Preamplifier revealed excellent performance, right across the board. RIAA accuracy was very good. You can see this from Graph 1, which measures from 5Hz right up to 40kHz— well beyond standard RIAA requirements. Looking at the performance across the target bandwidth (20Hz to 20kHz) the frequency response is 20Hz to 20kHz ±0.12dB. (You should ignore the small ‘wiggles’ in the response at 50Hz, which dBr 3.00 Newport Test Labs dBFS 0.00 Newport Test Labs 2.50 -20.00 2.00 1.50 -40.00 1.00 0.50 -60.00 0.00 -80.00 -0.50 -1.00 -100.00 -1.50 -2.00 -120.00 -2.50 -140.00 -3.00 10.00 Hz 100.00 1000.00 10000.00 Graph 1. RIAA frequency response, 5 volts out. [PureAudio Pure Vinyl Phono Preamplifier] 0.00 Hz 4000.00 8000.00 12000.00 16000.00 20000.00 Graph 2. THD at 1kHz. 5V output. [PureAudio Pure Vinyl Phono Preamplifier] Newport Test Labs’ bench tests of the PureAudio Vinyl Phono Preamplifier revealed excellent performance, right across the board were caused by some mains hum creeping into the measurements, which is almost inevitable when the voltages being measured are so low.) Channel separation was also excellent, particularly at low frequencies, where Newport Test Labs measured 101dB (at 20Hz). Separation ‘diminished’ to 87dB at 1kHz and to 76dB at 20kHz. All are far in excess of requirements: few phono cartridges are capable of delivering more than 20dB of separation at the frequency extremes, or more than 55dB at 1kHz. Channel balance was 0.2dB—also very accurate—and interchannel phase was perfect at 1kHz and only very slightly in error at the frequency extremes, so again, excellent measured performance from the PureAudio. Graph 2 shows THD plotted against frequency and you can see there’s a single second harmonic distortion component at –60dB, equivalent to 0.1% THD, which PureAudio Pure Vinyl Phono Preamplifier — Test Results Test Measured Result Frequency Response @ 5 volts o/p Channel Separation (dB) Channel Balance Interchannel Phase THD+N 5Hz – 40kHz 101dB / 87dB / 76dB 0.2 0.3 / 0.0 / 1.4 0.03% Units/Comment ± 0.25dB (20Hz / 1kHz / 20kHz) dB @ 1kHz degrees ( 20Hz / 1kHz / 20kHz) @ 5 volts output Signal-to-Noise (re 5mV input) 55dB dB (unweighted) Signal-to-Noise (re 5mV input) 82dB dB (A-weighted) 61dB at 1kHz 15.38V at 1kHz Gain Maximum Output Power Consumption Mains Voltage Variation during Test 114 Australian N/A / 8.55 watts (Standby / On) 241 – 252 Minimum – Maximum is right on PureAudio’s specification. The tabulated figures, however, include noise, which is why 0.4% is listed in the result table. On Graph 2 you can see some higher-order distortion components at 3kHz and 4kHz, but these are more than 100dB down, so contribute less than 0.001% THD to the total. The signal-to-noise ratio of the PureAudio Vinyl Phono Preamplifier was very low, particularly above 500Hz, where it dropped below 90dB and kept dropping to reach –140dB at high frequencies. However the summed wideband figures that are tabulated, of 55dB unweighted and 82dB A-weighted, include low frequencies, and you can see from Graph 2 (at the extreme left of the graph) there is some residual mainsfrequency noise in the output. Nonetheless, the measured wideband figure of 82dB is not only excellent, but actually exceeds PureAudio’s own noise Steve Holding specification by 2dB. 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