ULTRA AUDIO -- Archived Article

February 15, 2005

Tube Technology Unisis Signature Integrated Amplifier

A tube integrated amplifier can and should be a beautiful thing for the space-challenged or budget-conscious audiophile. These elegant one-box solutions eliminate the potential of an impedance mismatch between preamp and amp, and obviate the angst and expense of investing in an additional pair of interconnects. Nowadays, virtually all well-known makers of tube electronics proffer integrated models. I think this is a noble thing -- it is unlikely to make any of these firms rich. Rather, I suspect that tube integrateds are often fruits borne of technology trickled down from more ambitious designs; we consumers stand to benefit from the inherent value that they can represent.

How does one go about choosing an integrated amp from the myriad offerings? If one is downsizing to a piece from the same manufacturer, one might anticipate a similar "house" sound. More often, the move to a tube integrated represents an opportunity to expand one’s sonic horizons.

An obvious place to start comparing is the choice of output tube -- the different types tend to have different sonic traits. Then there are the output stages: single-ended vs. push-pull, class-A vs. class-AB, triode vs. ultralinear operation. While these features may allow the audiophile to develop a hazy sense of an amp’s overall sound and performance, purchasing one based solely on these criteria can be folly. The quality and build of the power supplies and output transformers also influence the sound, as will the selection of passive parts such as capacitors and resistors. However, these features are less often specified, and even when they are, the names and numbers would mean little to most of us who do not build amps. But the implementation of all of these parts into a circuit design is where magic can occur, and where a designer’s talents are most challenged.

Ideally, you should audition the amp with your speakers in your room. Unfortunately, this is often not possible, especially in light of the sheer number of models and the shift of the shopping paradigm toward the Internet and used markets. Manufacturers’ information, demos at dealers (if you plan to buy from one), and presumably unbiased reviews, whether "professional" or anecdotal, may be your only buying guides.

In a recent writeup, I waxed enthusiastic about the Unison Research S6 integrated amplifier. Although a good number of tube separates and several solid-state integrateds have graced my systems over the past 30-odd years, the S6 is the first tube integrated I’ve owned. It was on this background that I was presented with the Tube Technology Unisis Signature integrated amplifier.

Tube Technology, based in Wales, UK, has been building audio electronics since 1988. More recently they have entered the digital fray with the development of a well-regarded CD player, the Fusion CD64. The Unisis Signature ($5200 USD) is a direct descendant of the Unisis, an EL84-powered integrated amp that was one of the company’s earliest efforts. For the Signature edition, the preamplifier and driver stages were improved, and a new output transformer developed.

The amp’s 35Wpc of output is derived from two pairs of Russian Reflektor EL84 tubes per channel, driven in a push-pull fashion and operating in class-AB, ultralinear mode. (The output tubes are also labeled "6n14n," the ns printed in Cyrillic.) A pair of 12AX7s enclosed within the chassis work as the preamplification tubes, and two exposed 12AT7s serve in the driver stage. An optional phono stage (add $200), not included in my sample, adds a second pair of 12AX7s and is said to accommodate cartridges with outputs of at least 0.8mV. The Unisis Signature accepts five single-ended, line-level inputs; those equipped with the phono stage take four. A tape loop and preamp output are provided; power delivery, optimized for a load of 6-8 ohms, is by way of a single pair of speaker binding posts per channel. The amp is powered up by a rotary knob on the front panel; no remote control is available.

My sample arrived with all of its tubes in situ. The Unisis uses a "fixed-bias system" -- Tube Technology claims that tube bias need be adjusted only when replacing the output tubes with new ones. Should this happen, or should you wish to experiment with other EL84s, you must use a proprietary bias meter from Tube Technology. The biasing procedure itself seems straightforward; the pots are easily accessed from the top plate of the chassis.

The Unisis occupies a small footprint 14" wide by 9" deep and weighs about 35 pounds. The shiny, reflective surfaces of its classic, somewhat "retro" appearance brought out the primal audiophile in me -- I found the generous amounts of chrome finish appealing without being garish. The build quality, at least from the exterior, appears to be more than acceptable, as the 10-year transferable warranty attests.

I installed the Unisis Signature in my 14’ x 22’ x 9’ basement listening room. The system was fronted by the venerable Sony SCD-1 SACD/CD player. The even more venerable Cardas Hexlink 5s served as interconnects and speaker cables. I listened mostly to the Sonus Faber Guarneri Homage speakers, as well as others as noted below. To make comparisons, at various times I inserted the Unison Research S6 integrated, used through its 8-ohm outputs.


I started off with Norah Jones’ Come Away With Me [Blue Note 32088 2]. Okay, please stifle the groans. I’m aware that many of us have been overexposed to this disc, but despite having used this music for some particularly tedious cable auditioning a short while back, I never seem to tire of Jones’ sultry voice or the mellow riffs of her Handsome Band. Through the Unisis, this music was presented in a clear, cohesive manner with no part of the frequency spectrum lacking or overemphasized. Her voice was reproduced naturally, with none of the sense of edginess that some setups bring out. A back-of-the-hall perspective was provided, the image size being smaller and placed farther back between the speakers than I’m accustomed to. Imaging was sharply focused and precisely localized. But while everything sounded nice, I found myself fast-forwarding track after track rather than being ensnared in this music, as is the norm. Could the local critic who dubbed Jones "Snorah" in a review of her summer concert have been right after all?

In went the Unison S6. Immediately, the Handsome Band sounded more dimensional and Jones came to life, her voice taking on considerably more body and texture. Her phrasing became more tangible, and the fragility of her voice on "The Nearness of You" yielded an emotional connection to the music that was sorely missing with the Unisis Signature in the chain.

I listened to Schubert’s Octet, performed by the Academy Chamber Ensemble [Philips 416 497-2]. This work -- scored for clarinet, horn, bassoon, two violins, viola, cello, and double bass -- presents a rich palette of tonal colors that sounded relatively washed out through the Unisis. The horn and woodwinds were a bit pallid, and "bloom" was attenuated. The Allegro vivace’s rhythmic dynamics sounded fine at first, but only after I’d reinstalled the Unison S6 could I appreciate how engaged the musicians were in playing this music with each other, as opposed to simply going through the motions. Listen to the start of the last movement, which features tremulous strings building to crescendos. The sense of foreboding this motif invokes -- the kind of stuff a superior amp should convey -- is much better brought out by the Unison.

Pace and rhythm are somewhat abstruse audiophile concepts. Another war-horse, Dave Brubeck’s Take Five [Columbia CK 65122], continues to captivate in large part because of its unique rhythmic structures based on unusual time signatures. Nowhere is this more apparent than on "Everybody’s Jumpin’," whose tempo moves like a roller-coaster. Listen to the repetitive piano chords near the beginning of the piece and see if you can feel how Brubeck varies his intensity of attack to reinforce the rhythm. Listen to the last few seconds of the tune and see if you can feel the quartet playing to a frenzied climax. With the Unisis in the chain, I had to try too hard to appreciate this. Combine that with the barren sound of Paul Desmond’s alto sax and a less-impactful sense of Joe Morello’s drum thwacks and cymbal crashes, and the presentation was pedestrian. In a good setup, one shouldn’t have to listen analytically to appreciate good pace and rhythm. Rather, these attributes make themselves apparent to the subconscious, and manifest by foot-tapping and goosebumps when the occasion presents itself.

I listened to a variety of other material, and it became obvious that I had serious issues with the Unisis Signature. I considered that the Tube Technology device might have some bizarre incompatibility with the Guarneri Homages, which in general perform quite well with a variety of amplifier types. So I hooked the Unisis up to a pair of Wilson Audio Sophias. The Guarneris are said to present a nominal load of 8 ohms, dipping down to around 6 ohms, and are 88dB efficient; the Sophias present a fairly stable 4-ohm load and are 86dB efficient. The Wilsons were perhaps not the ideal match for the Unisis’ output transformer, but I normally use the speakers with 50Wpc push-pull tube monoblocks and feel that I lack for little.

The Unisis did make music through the Sophias, including acceptable control of their woofers, but duplicated the shortcomings that were apparent with the Sonus Fabers. The most egregious were the lacks of midrange body and presence, but blunted microdynamic shading, limited macrodynamics, and a subtle sense of restrained pace and rhythm all added up to a generally ho-hum impression. The Unisis seemed to do best with both speakers when playing amplified music, though particularly with the Sophias. I put on the likes of Stevie Ray Vaughan and Keb’ Mo’ and enjoyed the tunes, forgetting for the moment about such minutiae as air and bloom -- and, I suppose, these qualities are less important to the enjoyment of this type of music. Sure, when powered by the Unison S6, this music became more dynamic and intense -- but it also had a more "in your face" quality that may or may not appeal, depending on your musical sensibilities.

I wanted to try the Unisis on some high-efficiency speakers. I had no horns in my closet, but I did have a pair of 91dB-efficient B&W DM 302s, sweet-sounding bookshelf monitors acquired a few years back at a closeout price too good to pass up. It quickly became evident that the Unisis was most at home driving the B&Ws. The sound opened up and the music becoming more lively and tuneful, especially pop and blues tracks. Despite this, however, Norah Jones remained ever so soporific, the Academy Chamber Ensemble still moved along in perfunctory fashion, and Brubeck and his buddies sounded as if they were thinking about the next night’s gig.

The Unisis Signature didn’t sound bad. It was clean and neutral, with no trace of hardness. It struck me as offering a somewhat anachronistic sound that would mate very nicely with the original Harbeth HL Monitors, a pair of which I owned and loved years ago. Its polite, spare presentation would complement highly efficient, "colored" speakers, which are less commonplace today. On my present speakers, its sound simply lacked the flesh that should accompany the bones; as such, it consistently failed to draw me into the kinds of music I enjoy.

I reckon that judicious substitution of both the small-signal tubes and the stock Russian power tubes with other brands might improve but would probably not transform the Tube Technology’s sound. The difference in sound between the Unison S6 and the Unisis Signature could probably be partly explained by the inherent qualities of the output tubes -- despite the amps’ identical power ratings, the EL34’s meatier, more powerful-sounding midrange simply overwhelms that of the little EL84. Tube Technology does make EL34-based power amps; it would be interesting to hear them.


Audio enthusiasts are living in fortuitous times. New makers of tube electronics offering innovative and high-value products seem to materialize daily. Couple this with ongoing efforts from the established manufacturers, and we have a vital and highly competitive marketplace in which to explore the integrated tube amplifier.

Still, at a list price of $5200, the Tube Technology Unisis Signature cannot be considered inexpensive. The option of a built-in phono stage is a welcome and uncommon feature for an integrated amplifier in this price class, but partly due to current exchange rates that are unfavorable to the US dollar, the value of the Unisis Signature relative to its peers must be questioned.

…Ken Choi

Tube Technology Unisis Signature Integrated Amplifier
Price: $5200 USD.
Warranty: Ten years parts and labor (transferable); six months for tubes.

Tube Technology
Compton House, Drefach
Carmarthenshire, Wales SA14 7BA
Phone: (44) 01269 844771
Fax: (44) 01269 833538

E-mail: info@tubetechnology.co.uk
Website: www.tubetechnology.co.uk

North American distributor:
British Hifi
1336 Lorne Street
Regina, Saskatchewan
S4R 2K1
Phone: (306) 522-4454
Fax: (306) 522-4435

E-mail: kristen@britishhifi.com
Website: www.britishhifi.com

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