Expressive Technologies SU-1 moving-coil step-up transformer
Before getting to the SU-1, a few words about Expressive Technologies are in order. In many ways, they are like the small tweaky outfits that started the high-end audio business; they have a zeal for achieving the best possible sound without regard for user convenience or what the product costs. Unlike shaky garage operations, however, Expressive Technologies builds their products to the highest mechanical standards and fit'n'finish. Further, because the company is a labor of love by three audiophiles who have achieved financial success in other fields, Expressive Technologies is likely to be around for some time.
The SU-1 moving-coil step-up transformer is an offshoot of Expressive Technologies' research into designing a very ambitious electrostatic loudspeaker. Part of that design effort included building a step-up transformer for the electrostatic panel. The knowledge gained in transformer design was applied to stepping up a moving-coil cartridge's output signal. Incidentally, the SU-1 step-up was designed by a Bell Labs researcher who holds a PhD in analog circuit design.
The SU-1 step-up is one of only two products offered by Expressive Technologies. The other is the IC-1 interconnect. Because virtually all SU-1s are sold with two pairs of IC-1 (for reasons described later), this review is in essence an assessment of both products. In addition, I will comment briefly on the IC-1's sonic qualities when used with other products.
The SU-1 is definitely not what one expects a moving-coil step-up transformer to look like. At 19" wide, over 5" high, and weighing 35 lbs, the SU-1 is clearly a serious product. The rear panel holds two pairs of gold-plated RCA jacks and a ground terminal. There isn't much to talk about inside the unit; the SU-1 is a black box that contains two other black boxes—the left- and right-channel transformers. Build quality is excellent.
A few other technical notes: the SU-1 works best with low-output moving-coils, especially those with output voltages of less than 0.5mV. The relatively low-output (0.3mV) AudioQuest AQ7000 cartridge I used was a good match for the SU-1, while many of the newer high-end moving-coils have output voltages of 0.18mV, making them good candidates for use with the SU-1. However, cartridges with a high output impedance (above a few ohms) should be avoided. Not all phono stages work well with the SU-1; the phono stage input impedance should be high (47k ohms is ideal). Phono preamp gain is also a critical factor in how much difference the SU-1 can make to the system. High-gain phono stages don't need the stepped-up voltage, and some may be overloaded by the SU-1 when driven by even moderate-output moving-coil cartridges. The ideal conditions for the SU-1 are a very low-output moving-coil and a 47k ohms input impedance moving-magnet phono stage.
The SU-1's effect on the musical presentation varied from the dramatic to the subtle, depending on the phono preamp used with it. I'll start with the dramatic, heard when auditioned with an Audio Research SP11 Mk.II. The combination of the fairly low-output AQ7000 and the moderate-gain SP11 really benefited from the SU-1. First, the dynamic contrast was greatly improved, with a wider range between loud and soft. The background was "blacker," and high-level transients were sharper and more lifelike. In addition, there seemed to be greater resolution of dynamic gradation, the music taking on finer degrees of dynamic shading. Overall punch and slam were greatly improved; inserting the SU-1 in the phono chain was like giving the system a shot of steroids. Drums had more impact (especially kick and snare), contributing to a greater feeling of life.
Because much less gain was needed in the SP11's line stage with the SU-1, the noise floor was noticeably lower. Soft passages were more clearly delineated, rather than having a light hiss superimposed on them. This was especially apparent with records cut with low signals and music with very wide dynamic range. This improvement alone may be worth the price of admission.
I also found the SU-1 increased the "see-through" transparency of the presentation. There was a greater clarity that provided a clearer view into the soundstage. Soundstage depth, width, and focus were all improved by the SU-1. The impression of instruments and voices hanging in three-dimensional space was heightened, as was the feeling that a slightly opaque veil had been removed from between me and the music. The SU-1 was the antithesis of murky and congested.
The SU-1 also made instrumental textures more liquid and smooth. The treble, in particular, was more gentle and relaxed. Despite the softer presentation, there was a distinct impression of hearing more detail and information. The SU-1 uncovered another layer of minute detail and subtlety in the music. The enhanced detail, however, tended to reveal the subtle fabric of finely woven textures, rather than merely emphasize etch and grain.
The bass also benefited from the SU-1, becoming rounder and more liquid, with a greater naturalness. Acoustic bass had a warmer, less sterile and stultified character. Pitch definition improved, allowing greater resolution of individual notes. This was especially apparent during Ray Brown's playing on the Bill Evans record Quintessence (Fantasy F-9529). The instrument had a "fuller" sound, and was just more natural and right. Overall, the SU-1 step-up and IC-1 interconnect did wonders for the AQ7000/SP11 combination.
Next up was the Mod Squad Phono Drive. With both moving-magnet and moving-coil inputs, and front-panel selectable loading, the Phono Drive provided a wider range of conditions. I compared the sound of the AQ7000 going directly into the moving-coil input vs the SU-1 in the signal path connected to the moving-magnet input. This is a typical real-world condition; the SU-1's voltage gain replaces the additional circuitry of an active moving-coil stage.
Like my impressions with the SP11, adding the SU-1 was a revelation. The Hales Signatures seemed to have another octave of bass extension. The greater weight and power in the bass was not a subtle improvement. Transient leading edges were much more sharply defined, giving the presentation a greater sense of immediacy. The drums and percussion on the LP Roland Vasquez and the Urban Ensemble (Arista/GRP 5002), for example, took on new life and drive.
The SU-1 also had a dramatic effect on soundstage depth and apparent hall size. The presentation became deeper and more spacious, with a feeling of instruments floating in three-dimensional space. On the Robert Lucas album Usin' Man Blues (AudioQuest AQ-LP1001), for example, the space surrounding the harmonica and vocal bloomed to give a wider and more open perspective. There was a greater sense of the loudspeakers falling away and being replaced by images hanging in space. The sound was just more palpable and real with the SU-1. After hearing the SU-1, it was not easy to go back to listening without it.
To see what the effect of the SU-1 would be on an excellent MC stage, I used it to drive John Curl's Vendetta Research SCP2B (footnote 2). Despite the fact that the Vendetta SCP2B is designed to accept a moving-coil output without a step-up device, it was not overloaded by the SU-1 when driven by the relatively low-output (0.3mV) AudioQuest AQ7000 cartridge. However, as the Vendetta has more gain than the SP11 Mk.II, the improvement in S/N ratio was less meaningful. The Vendetta was quiet with or without the SU-1. I didn't hear the dramatic increase in dynamic contrast with the SCP2B that I did with the SP11, and with the Vendetta's variable input impedance adjustment set too low, the sound was rolled off in the treble and lacking life. The presentation was also a little on the lightweight side, the opposite character heard with the SP11. Not a recommended combination.
I must point out that I was unable to audition the SU-1 with any interconnects other than the IC-1 because of high hum levels with other interconnects. Whatever the grounding arrangement, I got an unacceptable amount of hum without the IC-1 interconnect (which has separate ground wires).
While I'm on the subject of the IC-1 interconnect, which costs $595/meter pair, terminated, I'll take this opportunity to relate my experiences with it. First, I can say without hesitation that the IC-1 is the best-sounding interconnect I've auditioned. I've had much experience with it over the past several months, and recently experimented with various interconnects between the Mark Levinson No.30 digital processor and the Audio Research LS2. In all cases, the IC-1 was clearly superior. There was a more natural portrayal of instrumental and vocal timbres. The IC-1's crystal transparency provided a more realistic feeling of the actual instruments' sound. There was also more inner detail and greater resolution of fine textures. The IC-1 presented another level of detail and nuance in the music. The bass was full and rich, yet tuneful and articulate. The treble was more laid-back than many interconnects, yet never sounded lacking in life. In short, the IC-1 excelled in every area, especially the first two noted: natural presentation of timbres and resolution of inner detail.
Despite the IC-1's superb sonics, it's not for everyone. Not only is it thick, bulky, heavy, and very difficult to bend, it's absurdly so—like a garden hose filled with ice (footnote 3). If you're going to set up your system once and not change interconnects, the IC-1's unequaled musical characteristics will make the effort worthwhile. Those who, like reviewers, constantly change equipment and interconnects, are cautioned about the decidedly user-unfriendly nature of the IC-1. Why is it the best-sounding stuff always seems to be the most difficult to use?
In suitable systems, the Expressive Technologies SU-1 step-up transformer can dramatically improve the quality of LP replay. The lower noise level, increased dynamics, more spacious soundstage, greater transparency, and more natural presentation of instrumental textures rendered by the SU-1 were nothing short of stunning. In fact, I found it hard to go back to the SP11 and Phono Drive without the SU-1 in the chain. These impressions will not hold true for all phono stages, however. Because the degree of improvement rendered by the SU-1 varies greatly with the phono section, prospective buyers are urged to audition the SU-1 with their preamp and cartridge before making a buying decision.
Would I spend $2950 for the SU-1? Without hesitation. It really was a quantum improvement, one I believe justified by the SU-1's not insignificant price. I should reiterate that using Expressive Technologies IC-1 interconnect in the phono chain is essential, both because of the potential for hum and the synergistic sonic effects of the two products. The cost of two pairs of IC-1 should therefore be factored into the SU-1's price.
If you love LPs and have a low-output moving-coil and a preamp with a high impedance input, the SU-1/IC-1 is a "must hear" product. But I'll warn you: Once you hear your favorite LPs through the SU-1 step-up and IC-1 interconnect, you may not want to live without them.
Footnote 1: It's ironic that the current era of great advances in LP playback technology coincides with the decline of LP availability.
Footnote 2: Though John Curl's house burned down in the devastating Oakland fire last fall, with all the meticulously selected components used in building the SCP2 going up in smoke, John says that he will build SCP2s—probably the finest phono preamp ever made—to order.
Footnote 3: Because the interconnect can only take on a limited radius of curvature, it may be unusable in your system due to such a trivial matter as the distance between your equipment rack and the wall behind it; this was the case in my system. You should also take care not to break the center pin of the Tiffany RCA plugs with which the cable is fitted.—John Atkinson