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Positive Feedback ISSUE 55
Pulsare Phono stage - The New Kid on American Shores?
as reviewed by Myles B. Astor
High-end audio designers have literally attempted since the dawn of time to transcend that elusive sonic gap between the sound of solid-state and tube electronics. So great the gulf in fact, that it wasn't until the arrival of Avid HIFI's new Pulsare phono section did I think the two technologies would ever narrow their differences. This solid-state phono section, designed and manufactured by the UK company better known for its turntables, is a more than a worthy competitor to the tube phono sections that have passed through or are now ensconced in my reference system. Avid HIFI's Pulsare doesn't exhibit the stereotypical whitish, bleached, thin, cold and edgy solid-state sound. Moreso, this phono stage does many things that didn't think possible from a solid-state phono sections such as spatiality, low level resolution and imaging. Where the Pulsare falls slightly short of ultimate is in the areas of midrange presence and harmonic overtones, sense of instrumental body and upper octave bloom. But that's not a fixed quality as we shall see later.
Now selecting that phono stage to complete the analog front-end isn't a trivial task. Obviously, the first and foremost consideration is sound quality, closely followed by price. The next concern is whether the total gain of the phono plus line stage is up to the task of handling the output of your cartridge (a problem nowadays since the gain of many of today's line stage's gain fall in the 10 to mid-teen levels in order to integrate with the higher output of digital equipment) without the intrusion of noise or loss of dynamics. On the whole, most modern day phono sections work quite well with cartridges down to 0.5 mV output. It's when the cartridge's output dips below 0.5 mV, however, that things, principally with tube units, often become a little dicey. So why choose a low output moving coil cartridge if gain and noise are a problem? Simply, many vinyl lovers feel that these low output voltage cartridges represent the ultimate in transparency, resolution and musicality.
So the choices for a high gain, phono stage basically boil down to this: a "pure," all tube based circuit, a hybrid tube plus solid-state circuit, a tube circuit plus step-up transformer or a completely solid-state circuit. The problem simply stated: very few (pure) tube phono sections can successfully amplify very low output voltage cartridges without running into noise, hiss and a host of other issues (though the ear is able to filter out a lot of things; once hears the drop in background noise, especially with solo instruments, however, it's near impossible to go back).
Nor does the quality of present day tubes help the situation either (Remember manufacturer's have to select and stock vacuum tubes that will be available in large quantities for the foreseeable future for their customers; tube stocks can add up to significant overhead costs for a small high-end company!). So even though manufacturers specially select low noise, low microphonic tubes for their phono section, there's absolutely no guarantee for how long they'll remain that way. Of course, one can dabble in tube rolling using NOS tubes; realistically though, unless a tube comes in a sealed package, more often than not these tubes have seen plenty of use. Many times these "NOS" tubes may sound wonderful but have one small problem: they lack any balls eg. dynamics. (after all, did the claimed 10,000 hour lifetimes refer to how a tube would function or how long a tube would be sonically viable?) And just as with new tubes, NOS tubes won't be up to the task of being used in phono section unless they're specially selected. Hence to get adequate gain to amplify the low voltages—and without the intrusion of noise—of low output moving coil cartridges, many tube phono section manufacturers turn to the use of hybrid circuitry or step-up transformers, each of which offers their own unique set of advantages (as well as disadvantages) over pure, all tube phono sections.
Last but not least is opting for a solid-state phono section. In yesteryears, this often meant sacrificing harmonic integrity, low level resolution, ambient space and instrumental three dimensionality for low noise and dynamics. In retrospect, this was a very unfair trade-off. Clearly the Pulsare breaks with this stereotype and is the harbinger of even better things to come with future solid-state phono stages.
Crossing the Big Pond
Avid's founder and designer Conrad Mas is no Johnny-come-lately to the high-end audio or analog scene. Mas, a self confessed analog devotee tracing back to his days working at Acoustic Arts in Watford, UK, has designed and built turntables for close to 25 years. The Pulsare phono section is however, if you don't count the power supply/motor drive for the Avid turntables, Mas's first foray into electronics realm.
The Pulsare phono stage consists of two roughly square black boxes, one housing the beefy outboard power supply unit and the other the ever so critical phono circuitry. Needless to say, the two units should be situated as far away from each other as possible to minimize noise, hum, etc. No, the Pulsare won't be found on display at MOMA any time soon but it's a whole ‘nother story when it comes to user friendliness with the all controls (including six capacitive and nine resistive loading options, selectable gain, and input selection [RCA, XLR balanced]) conveniently located on the front panel of the control unit. Mas chose to situate the controls on the front of unit for ease of use, flexibility and shortening the signal path. (On the whole, most cartridges in my experience is that cartridges prefer to loaded at 47 K and that held true with the Pulsare.) While MC cartridges are generally considered insensitive to capacitive loading, one cartridge, the Air Tight PC1, did benefit from loading at 1 nF resulting in improved resolution, speed and openness.
In addition, the Pulsare is a fully balanced design, even if using a single-ended input. Running balanced allowed Mas to "maintain the purity and integrity of the miniscule signals flowing thru the phono section." Other benefits of running balanced include "low distortion across the audio spectrum, large headroom and preventing the phono stage from running out of steam regardless of the music." Mas also opted for a passive RIAA with Neumann HF correction circuit w/audiophile grade caps for optimal linearity (see interview for more information on the RIAA curve).
Not to be forgotten is the second, rather hefty 14 pounds power supply consisting of a doubly regulated, dual mono 300 VA power supply. Separating the circuitry allowed Mas to reduce noise, vibration and susceptibility to outside interference. In addition, this decision also allow Mas to build a much larger, higher current power supply, crucial he feels to the unit's ability to portray rhythmic integrity and dynamic range.
Finally, it's painfully obvious that the choice of AC power cord is paramount for extracting the last few percent of performance from phono sections (as well as digital gear). This observation holds true for all the phono sections in house including the Pulsare, conrad-johnson TEA1bc, Allnic H3000V or Doshi. (In fact, it is next to impossible to go back and listen to the unit using the stock, supplied AC cord.) To date, the best results were obtained mating the Kubla-Sosna Emotion AC power cords with the Pulsare. Using the Emotion, the Pulsare's low level resolution, reproduction of instrumental harmonic structure and an uncanny ability to recreate the three dimensional sense of an instrument playing in the room were all improved. Moreso, the Emotion AC power cord just fleshed out that midrange quite a bit more than the stock or ESP Reference AC power cords. When it came to phono cables, excellent results were obtained with either MIT's Oracle MA-X phono cable or Kubala Sosna's Emotion IC/phono cables.
Making a Splash
In some respects, the solid-state Pulsare challenged tube electronic's long standing hegemony in the areas of low level information and detail retrieval, spatial recreation and soundstaging. Not unexpectedly, the Pulsare also scores high marks for where the best of solid-state designs excel: a vanishingly low noise floor, transparency, dynamics, transient attack and frequency extension. All without having to deal with tube noise and rush or when a tube would eventually go microphonic or noisy.
And then again, there's the Pulsare's dynamics, that continued to grow on me as time went on. There's no question that having adjustable and adequate gain and drive at the phono section end really improved the sound. When the Pulsare's gain was dropped from 60 to 50dB (producing a total gain now of 74dB—and still realistically capable of working with a 0.5 mV cartridge), the unit did not exhibit the same sense of dynamic freedom. Yes, the music still sounded pretty but bordered on boring. This extra "horsepower" manifested itself in a sense of ease to the music, a freedom from dynamic constriction, much like one hears on a good 15 ips tape. On wonderfully recorded Decca operas such as Puccini's Tosca (Decca Stereo Set 5BB 123-4), one is constantly adjusting, albeit annoyingly so sometimes, the volume, say in the opening aria of Act 1. Voices and we're talking about stars like Leontyne Price, were effortlessly reproduced and projected out toward the listener.
What really stood out in the end, however, was the Pulsare's neutrality and ability to extract the most from, yet clearly define the sonic differences among, the ZYX Omega G, Haniwa, Lyra Titan i and Air Tight PC1 cartridges. While the Pulsare phono stage lacked the thinness, coldness and edginess of some solid-state phono sections, neither did the Pulsare exhibit the romantic lushness and syrupiness other tube phono stages either. In the case of the Titan i, this neutrality translated into an uncanny ability to resolve the finest of nuances—especially in the upper registers—as well as an unfettered sense of ease and unmatched transparency. For the Haniwa, it was revealing the cartridge's midrange and upper octave purity. For the ZYX, it was tightening up the cartridge's mid and upper bass. Alas, even using the Pulsare, the Air Tight PC1 just never sounded right in my system (and the VPI arm).
A perfect album that both the Pulsare and Martin-Logan Summit-Xs eat for breakfast and nicely illustrates the phono section's neutrality is the movie soundtrack Missouri Breaks (United Artists UA29971). With the ZYX Omega G, there's a slight rounding and softening of the banjo. By contrast, the Titan i was far more neutral, faster and detailed and the lower octaves considerably tauter. The banjo is less smeared and exhibits more of its characteristic "twang." The Titan i also far more convincingly recreates the eerie atmosphere of "Bizarre Wake." Really losing out in these comparisons was once again, the Air Tight. Despite numerous attempts at adjusting the SRA, capacitive and resistive loading, could, I could never get the proper upper octave extension. Missouri Breaks sounded ponderous, especially in the low end.
Another must-have LP is the spectacular 1966 recording of Benjamin Britten's Rejoice in the Lamb (Argo ZRG 5440—and the best pressing of the lot and one to hunt down is the earliest round Argo label, thick pressing). Using the ZYX Omega G, one hears, as with the finest phono sections, the boys entering from the back left of the church, coming closer to the microphones and filing onto and spreading out over a vast soundstage. With the Pulsare, one can almost feel the boys making a sharp left to enter the stage. Individual voices in the choir are rendered with precision; when the various soloists enter—especially the luscious Maria Robles on harp—there's no image wander. Moreso, it's clear that this is a boys, not a men's choir, by the higher pitch of their voices (even more intonation of voices is heard using the Titan i.)
One of the hallmarks of this church—and this recording in particular—is how the engineer captured the rich sense of ambience and space of St. Johns Church, along with the decay of the performer's voices (as this long and narrow church does so wonderfully live!). Clearly it was no easy task for the recording engineer to balance the direct with reflected sound on this recording. And here, the Pulsare's vanishingly low noise floor allows for even more of the music, ambience, detail and space to emerge. For instance, it's now possible to identify the low frequency rumble on the recording being trucks passing by on the street, not the "blower" for organ!
Of course, nothing is perfect and there are a couple of areas where the Pulsare falls somewhat short of ultimate, most notably in the areas of resolving the finest overtones and sense of space and to a lesser extent, the palpability of performers. For example, the Pulare's transparency allows the mind's eye to see to the back of the stage but there's not as much retrieval of the solidity of back and side walls as with the best tube phono sections.
Then there's one of my long time reference—and fun discs—Saul Goodman's Mallets, Melody and Mayhem (Columbia CS8333). Few albums prove a greater torture test for each and every component in the chain, beginning with the transducer and continuing down the line to the speakers, than Mallets, Melody and Mayhem. Each and every track on this LP is an absolute blockbuster (I don't know why someone hasn't reissued this recording; perhaps the tapes are missing or damaged?), thoroughly testing a component's ability to reproduce every nuance, instrumental frequency response, transient attack, macro- and micro-dynamics and complex palette of tonal colors. Of late, Adolph Schreiner's "The Worried Drummer" is seeing a lot of play time but Morton Gould's "Parade" will do in a pinch! Practically every component loses something on these cuts and it only the ne plus ultra system that reverses that trend and begins to show that there's even more in the record grooves than previously heard.
What really stood out about the Pulsare when playing Mallets, Melody and Mayhem was the unit's shocking sense of transparency, dynamics and detail. There was an unmistakable sense of the mallets striking the drum head, the drum size and the decay of the instrument. Yes, the fatness of the Columbia pressing was still there, but markedly reduced in amplitude. At the other end of the frequency spectrum, percussion instruments had limitless extension and a good sense of dynamic snap and freedom from smearing. Interestingly, what had appeared to be high frequency cartridge mistracking on certain records with other phono sections disappeared or was greatly reduced with the Pulsare.
The first cartridge cued up on "The Worried Drummer" was the ZYX Omega G. Here the Pulsare nicely recreated the recording's exceptional soundstage and layering of instruments. On "The Worried Drummer," the Pulsare's vanishingly low noise floor contributed to the unit's excellent, overall sense of transparency and the ability to "see" the space between the piano and drum. Chimes were slightly blunted, yet very dynamic with a nice decay. Wood blocks had a solid, knotty quality. Drum whacks were far tighter with good decay.
Inserting the Air Tight PC1 proved disappointing. Despite playing with loading (both capacitive and resistive), SRA and azimuth, the cartridge refused to sing. No matter what, this cut from Mallets, Melody and Mayhem just sounded sluggish, boring and dark.
Swapping out tonearms once again (of course adjusting SRA) and now playing back "The Worried Drummer" using the ultra-neutral Haniwa cartridge into the system (review forthcoming) resulted in much better upper octave extension than with the two previous transducers. The ringing and decay of triangles and sleigh bells—as well as the sudden damping of the triangles—were clearly revealed. With the Haniwa, there was a greater sense of individual sleigh bells being shaken with the Haniwa than with the ZYX accompanied by a greater sense of openness and transparency. No, not that black coloration so often now described in equipment reviews. Black never enters into my mind when I hear live classical, jazz or rock music. All I hear at the best halls or clubs in a colorless, unfettered, expansive sense of openness.
The cartridge though, that really brought this disc to life and really showed off the Avid's transparency, neutrality, resolution and speed (or vice versa) was the Lyra Titan i. In fact, the Avid phono stage kicked the Titan i's performance up several notches and gave it a new lease on life. As a result, the Titan i is now far and away my favorite and reference cartridge. What's special about Avid/Titan i combination? The Pulsare now allows the Titan i's ability to retrieve the finest of low level information without any trace of etching to shine through. With this combo, there's far more inner detail and air surrounding the piano without any trace of hardness or coldness. This combo allows for an unfettered sense of being able to see to the back of the stage and literally reach out and touch the drums. Chimes and other percussion instruments on Mallets, Melody and Mayhem float on a bed of air. Sleigh bells display more upper octave extension and individual bells jingle and jangle than the three previous cartridges.
Another area where the Pulsare proved slightly subtractive was the ability to recreate an instrument's sense of body and to a lesser extent, the air and overtones surrounding the piano. The tambourine occupied a real space on the stage but the Pulsare feel slightly short of ideal in recreating the tambourine's characteristic ‘pop', body and the feeling of the metal jingles eg. zils shaking. That prevented the mind's eye from totally visualizing the instrument and in particular, the edges of the tambourine. The same quality is even more apparent on either Musik fur Flote and Laute au Renasissance und Barock (Deutsche Harmonia Mundi HM 1C-65-99859) where the wooden flute loses a bit of the air surrounding the instrument and the lute loses some of sense of body and harmonic overtones or Getz /Gilberto (MFSL 1-208), namely "The Girl from Ipanema," where Astrud's voice loses a little of its ethereal and breathy quality.
This effect though, was greatly dependent upon the AC cord mated to the Pulsare. First of all, don't even bother with the stock, throwaway AC cord; with this cord, the piano's midrange was slightly lacking. Substituting the ESP Reference AC power cord for the stock AC power cord improved transparency, transient attack and frequency extension but the piano was still a little lean sounding. Kubala-Sosna's Emotion AC cord proved the lifesaver, significantly aiding in fleshing out the midrange and in particular, the overtones of the piano and other instruments.
Nor does the Pulsare quake at the sight of other musical genres either. The Titan i/Pulsare duo reveals dynamics on "Better We're Right" from Supertramp's classic rock album Crime of the Century (Mobile Fidelity 1-005), that today's rock combination can only sadly dream about. The soundstage is incredibly deep and wide. There's a kaleidoscope of dense orchestration without any bloody hint of congestion. Individual voices are nicely separated and float in the mix. On "Bloody Well Right," this combination has an amazing ability to localize both piano/synthesizer and guitars as well as recreate the distinctive tone of each guitar.
At the risk of being excommunicated from Sunday morning music listening sessions by my tube loving audiobuddies, there's no denying the fact that the Pulsare is one of the most musical and revealing solid-state phono sections that I've had the pleasure to audition. Where the unit is right, it's nothing short of thrilling; where it falls short of ultimate, the Pulsare never detracts from the listening experience. You owe it to yourself to give a listen to this phono section before choosing any other moderately priced—or even top of the line phono stage. Myles B. Astor
Pulsare Phono Stage
Avid HIFI Pulsare Phono Stage, distributed by Music Direct, 318 No. Laflin Street, Chicago, IL. 60607. Tel.: (312) 433-0200.
Conversations with Conrad Mas of Avid HiFi:
1. Conrad, could you tell me what led your company's decision to expand your product offering from turntables to electronics?
This is something we find ourselves being asked frequently. We already make electronics! They're called turntable ‘power supplies' and ours are essentially fixed output, two channel integrated amplifiers. If you take a look, especially at our Reference PSU, it puts a lot of amplifier manufacturers to shame. However, I can see your point that most don't see the power supply and just see a turntable, so a stand alone electronic box is different. It's a bit like asking a company who makes active speakers what made them go into power amps.
However in essence there are a few reasons for starting into electronics per se.
Making source components makes you reliant on other components down the chain; over the years, we have seen mixed results from customers using our equipment. Mostly they are favorable, accounting for our ever increasing turnover. Over the past few years, however, we have seen a steady, in our opinion, decline in the quality of electronics.
There seems to be a drive to ever higher levels of detail resolution, typically at the expense of music sounding real. At a live performance, especially pop/rock, distortion and other noise is huge, but the performance still has power and a solidity to the sound whereas of late, electronics seem to sound like high resolution transistor radios with about as much balls as a castrated choir boy!
As our turntables are known for deep, realistic, clean tight bass we wanted something to allow this through, whilst keeping noise extremely low so the mid/high detail remained and didn't make it sound harsh. Many have remarked that the Pulsare sounds smooth like valves, but clean, deep and tight like solid-state. A lot of the design technology that has gone into the Pulsare is directly derived from the Reference Acutus PSU, so you see there is a strong connection already with electronic design.
The other reason is a business decision to expand through diversification and electronics is a logical stage, especially as we already manufacture our own cables and accessories. We did the same some years ago when we diversified into commercial engineering which now accounts for some 30% of our business. These days there's no standing still. You either progress forward or you'll be left behind.
2. Where did you think current phono section fall short of ultimate and how did you think you could improve on that?
This one's simple: sound quality; it's what drives everything we do. The facilities offered on the Pulsare make set-up and fine tuning easy, but the main goal was sound quality. Specifically we wanted to put the ‘balls' back into sound reproduction. Like when you hear a kick drum, you also feel it in the chest. Noise levels had to be extremely low, because again like our turntables, we want you to hear the music not the equipment.
3. What were your major design objectives in the Pulsare?
Firstly to produce a Reference Standard unit that would redefine phono quality and put Avid on the map as a serious electronics manufacturer.
Apart from sound
quality, there were certain key elements we wanted to include. First,
the design should run fully balanced, but allow for XLR and RCA
connections both in and out. Next, resistance and capacitance should be
adjustable from the front panel for ease of use. Then, we wanted to
totally eliminate the use of microprocessors so as to avoid noise.
Finally, was the use of a separate, dedicated, power supply.
The internal electronics of the Pulsare run fully balanced. This is done to keep the vital and delicate signal free of interference, hum or RF noise. Obviously when a balanced input is used the signal passes unaltered; however if an unbalanced RCA input is used the signal is automatically converted into a balanced signal through to the output. At this stage there is a choice of either balanced output or its converted back to an unbalanced output.
There is a sound difference between balanced and unbalanced, but the question is confused as the Pulsare only works balanced and not unbalanced as suggested. The difference in sound quality comes from the use of either balanced or unbalanced input from the cartridge. Ideally to obtain the best quality sound, fully balanced connections should be used from the cartridge to the phono stage. By doing this, the sound is clearer, more dynamic and simply more realistic. Why the audio industry ever used RCA connections for a turntable defies logic and it's almost criminal (If I had a dollar for each time I've heard that comment, I'd have a custom built listening room and 150K speakers—MBA).
5. Why did you opt for a separate power supply and could you talk about the power supply design and its importance with the phono section and electronics/parts selection, etc?
The power supply of any electronic equipment is critical to its performance. A separate PSU was decided upon from the outset to make sure any potential noise was kept away from the phono electronics. As with the phono section itself, component choice is important and everything from the mains transformer to capacitor to resistor selection is critical.
Describing the importance of a PSU can never be under-played and again our turntables are testament to this. A good analogy would be a high performance car engine. Most these days are designed to run on high octane fuel, however they'll still run on low performance fuel but just not give such a good result. The same with electronics; given the right size, design and component selection and you'll reach a whole new level.
6. I've found that the Pulsare sounds much better with a after market power cord. Many of the issues I was hearing were remedied by a better power cord. What are your thoughts on choosing a proper AC power cord to mate with the Pulsare?
This does not surprise me and customers should experiment with suitable mains cables. Depending upon their supply, cables will sometimes make a limited difference but on other occasions the improvement can be dramatic.
7. Could you talk about the RIAA curve you chose and how designing a RIAA section is not such a trivial matter?
When the Pulsare was originally conceived, we did consider offering various RIAA curves to cover the period before the mid-1950's when each record company applied its own equalization curve. We considered this option for about 5 seconds, as when you think there were over 100 combinations of turnover and roll-off frequencies in use, the only way of doing this would have been the use of a microprocessor, something we did not want to use. As AVID makes pioneering ‘new' technology turntables and in all the years of doing shows and speaking to customers, none have mentioned these older recordings. Consequently, we decided to use the RIAA equalization curve industry standard for the recording and playback of vinyl records since 1954. That should cover it!
When we looked into this matter further, however, we realized that most recording studios whilst sticking very closely to the standard curve, used treble emphasis limitation in recording for decades (there is a quasi-standard defined by the leading record-cutting-machine manufacturer Neumann). Applying a correction according to Neumann standard makes a small but very audible difference. Whilst it's important to follow the RIAA curve, not doing so only alters the tonal balance of the sound; there are actually other items and components within a phono-stage that alter or make a bigger sonic difference than slight deviations off the correct curve. For instance if you played a record that was not cut with a perfect RIAA setting, say 1 dB difference between 1 K and 5 K, you'd be hard pressed to even notice. If we, however, changed the type of capacitors used in the phono stage, there would be a much bigger and totally noticeable difference.
8. What are you feelings about loading cartridges, pro and con, at 47 K or lower?
Correct cartridge loading is simply essential. Every cartridge is different and requires the phono stage to be optimized to it to get the best performance. I was at a show recently where we had our turntable and phono stage playing within a system. Typically one listener remarked that the speakers were fantastic, as if it were the only thing making the sound quality. A quick adjustment of the resistance loading soon showed the importance of the phono stage and easily proves the system is only as good as the weakest link.
9. What does the future hold in store for Avid electronics?
Like our other products, the electronics we design will have their design philosophy and technical side and we appreciate that as a hobby to many, they wish to know, learn and discuss these aspects. However our goal with all our products is to bring a new level of sound quality to the listener were rather than simply listening to music: they experience it.
Phono stages were a logical step for us and we quickly launched the more economical PULSUS phono stage. In 2011 we'll see our Reference Pre-Amp and Reference Mono Amplifiers, followed by other preamps and stereo amplifiers and even an A/D converter. Our electronic design road map extends all the way into 2012, and with other analogue products, cables and supports in design we'll soon not been seen solely as a turntable company, but as a audio solutions provider at different budget levels with its roots firmly planted in high quality sound experience and not just making a noise.