13 years ago, Dan Wright was building his first product, the SWL 9.0, named after his son and I had just begun my career of reviewing audio gear for The Absolute Sound.

I was building my first major system and wasn’t getting quite the sound I wanted. My ARC LS-3 was a bit on the thin side and my CJ PV-12 just a bit too warm for the rest of the components in my reference system (back then: a pair of ARC Classic 120 mono blocks, a pair of Vandersteen 2Ce’s and a Rega P25). Kurt Doslu from Echo Audio suggested a preamp from “the new guy in town,” Dan Wright.

It only took a quick listen to see that the SWL 9.0 was Goldilocks. i.e., it was “just right.” With simple, clean and understated aesthetics and amazing sound for the then $1,999 price, Dan Wright’s first effort was a winner. Had we given out Exceptional Value Awards in our first year or two, this product would certainly have won one.

Thirteen years later, the SWL 9.0 Anniversary Edition celebrates everything ModWright stands for: great sound, great build quality, and great value. And like a thirteen year old BMW 3-series, the original SWL 9.0s continue to delight audiophiles the world over.

Now that ModWright has broadened their product offerings considerably, the 9.0 SWL, according to Dan is “the perfect way to introduce music lovers to our brand for the first time.” Expect a matching power amplifier somewhere down the road, as Dan Wright is always brainstorming something new…

With the price only going up $900 in 13 years, the new SWL 9.0 has more functionality, better casework and incorporates everything they’ve learned in 13 years of building quality gear. Watch for our review in issue #78.

Click here to go to their website.

Perhaps the most enjoyable part of the hifi journey is discovering something new, especially on a heavily traveled road.  It’s like discovering that cool coffee shop down the street, only to find that it’s been there for years and you just passed it by.  The same could be said for the Unison Research S6 integrated amplifier, now in production for over a decade.

Moderately powered tube amplifiers based on the EL34/6CA7 output tubes have a legion of followers, myself included.  I’ve owned many variations on the theme – from the legendary Marantz Model 8 and the Dynaco Stereo 70, to current production amplifiers from Conrad Johnson, Prima Luna, Octave and now the S6, reviewed here.  I’ve even built a few in my younger days.  While I’ve never met an EL34 amplifier I can’t enjoy, the folks at Unison or Conrad Johnson need not lose sleep over my making a career change anytime soon.

This pentode tube almost always produces a more mellow sound than the 6550/KT88, which usually delivers about twice as much output power per tube.  The midrange of the EL34 is usually described as having a warmer, more romantic, tonally rich sound than many of the other output tubes, these lower powered amplifiers often render inner detail with more delicacy than most of the higher powered tube amplifiers.  (Those thinking 6550’s can’t offer subtle inner detail, look no further than the Octave Jubilee monoblocks)

Design Differences

Regardless of the flavor you choose, amplifiers built around the EL34 tube rarely disappoint when it comes to midrange magic – and the Unison Research S6 is no slouch, yet it offers so much more.

Rather than a traditional push-pull configuration, the S6 employs three EL34 tubes per side, in parallel, driven in single-ended, Class-A triode mode.  Mixing it up even further, the S6 features a combination of auto bias and adjustable bias, fine-tuning the operating point of the output tubes to perfection.  With a pair of stylish meters and front panel adjustability, no tools are needed – meaning no tools to lose or misplace before a listening session.  It’s wise to keep an eye on bias when your S6 is brand new, checking every few days. After about a month, the tubes settle in and a casual check now and then will suffice.

Standard issue tubes continue to improve and the current TungSol EL34’s supplied with the S6 proved close enough to the megabuck vintage EL34s on hand for comparison, that for all but the most fanatic and well heeled tube roller, you can rest assured the S6 sounds great right out of the box.  The controlled biasing combined with not running the output tubes terribly hard should make for ample tube life.  The 12AX7 driver tubes should last in the 10,000 hour range, making this an easy amplifier to live with long term.

I did not spend a lot of time tube rolling, and swapping a few different EL-34s for the Tung Sols provided different sound but no overall improvement, so I submit the designers have done an excellent job voicing around current tubes.   This amplifiers character can be changed more (and for less money) successfully merely substituting the two 12AX7s.  A pair of Telefunkens or Bugle Boys will push the sound more towards the classic syrupy tube sound, while my favorite 12AX7, the EAT gives the S6 a lower noise floor and even more HF extension and less grain.  Regardless of where you stand on tube rolling, the stock tubes are an excellent choice and should be fine for all but the most OCD tube roller.

The rest of the amplifier is straightforward, with volume, power and input selector on the front panel and five single ended inputs around back.  Unison claims the S6 compatible with speakers in the 4-8 ohm range and provides a single set of output binding posts.  Even the remote is unique, eschewing the standard kids meal remote that many products at this price feature, in favor of a more stylish remote with a wooden body.  The S6 covers all the bases to be qualified as a premium product.

Mightier Than Its Power Rating Suggests

Audiophiles fixated on specs might pass on the S6 because of its modest power rating – yet its 35 watts per channel will suffice for all but the most inefficient speakers when playing at reasonable levels.  This robust amplifier works well with all of the test speakers at our disposal, from the 85db Dynaudio Confidence C1s, to the 91 db Sonus Faber Ellipsa SEs.

The S6 produces some of the most lifelike bass response I’ve heard from an EL34 design – tonally rich, yet controlled throughout the range.  Put to the full test with my reference GamuT S9 speakers that are only down 3db at 18hz, the Unison amp proved it could deliver major bass grunt when required.  Whether I was playing Genesis, Snoop Dogg or Stanley Clarke, it was always easy to discern what was being played.

The S6 is also a perfect companion for my freshly refurbished Quad 57s.  After a recent attack of audiophile nervosa, auditioning over a dozen amplifiers with the Quads, the S6 enchants with a mix of solid, well-controlled bass, a three dimensional soundfield and an extended high end – the latter the most tough to achieve with these speakers.  If you happen to be a 57 owner, you know what I mean. The S6 did not have enough juice for the woefully inefficient Acoustat 1+1s, (81db) or the power hungry Magnepan 1.7s to more than a whisper, but that is a challenge no low power amplifier can pass.

However, the S6 is perfection for a listener in a modest room with a high quality pair of small speakers.  In room two, (which is 13 x 15 feet) mating the S6 with either the Harbeth Compact 7ES-3s, Dynaudio C1’s or the Penaudio Cenyas makes for a symbiotic relationship far greater than the sum of its parts.   Combining the S6s liquid midrange with the imaging of these speakers in a small room makes for an immersive listening experience that’s tough to argue with. It’s almost like a giant pair of Stax headphones.

That’s just my take on the bass and imaging.  The true beauty of the Unison Research S6 is the smooth, yet defined midrange and the ease that it transitions into the upper registers.  Cymbals sound reach out and touch them real and solo vocalists are divine.  A quick spin of the latest Doors remasters from Acoustic Sounds on 45 rpm vinyl reveal layer upon layer of vocal and instrumental texture in a way that most vintage gear does not.  The S6 follows the musical pace well, producing texture and tonal contrast without sounding warm, syrupy and slow.  A perfect match of old and new school design ethos.

Simplicity, Form and Function

I love the simplicity that a great integrated amplifier provides.  Add a source or two, your favorite pair of speakers and call it a day.  $4,895 spent elsewhere will no doubt buy you more power, but you’ll be hard pressed to find the finesse, both electronically and aesthetically that the S6 offers.  This amplifier is more than just a nice tube integrated; it is a work of audio art.  It’s an amplifier that should be put on a pedestal with a wonderful painting above it.

Unison supplies tube cages for the S6 to protect kids, cats and pups, but the amplifier is so much more attractive with them removed, it seems a shame to have to use them.

If 30-35 watts per channel is enough to rock your world and you’ve been itching for something special, audition the Unison Research S6.  I think you will agree that this is a unique product.

Unison Research S6 Integrated Amplifier

MSRP:  $4,895

en.unisonresearch.com   (mfr.)

www.colleencardasimports.com (US distributor)

Peripherals

Analog Source: AVID Volvere SP/Durand Talea arm/Miyajima Kansui

Phonostage: Zesto Andros PS1

Digital Source: dCS Paganini Stack, Sooloos Control 15

Speakers: Harbeth Compact 7SE-3, Penaudio Cenya, Dynaudio Confidence C1 II

Cable: Cardas Clear

If you love tubes as much as I do, you know the lure of finding great NOS tubes.  There aren’t that many lurking in garage sales anymore, so the chance of finding a cache of Mullards or Telefunkens for five bucks is slim to non-existent.  Even the old ham radio operators know about eBay now and price their booty accordingly.

The designer and end user face the same dilemma; where to get the good tubes without breaking the bank.  Many love the sound of the old Telefunkens, Mullards and Phillips 12AX7s, but the best examples can fetch 200 – 300 dollars on the right day.  Just like buying parts to restore a vintage Porsche 356, there are only so many NOS parts to go around and those remaining get more expensive by the day.  Fortunately all but the very best 12AU7’s are still below 100 dollars each, but again as supply goes down and demand goes up, the end result is inevitable.

New New Stock

Having had excellent luck in the past with the TJ Music 300B’s, I was anxious to try their small signal tubes and was pleased with the results.   The folks at Grant Fidelity are now the North American importers for these tubes and you can see their full selection at www.grantfidelity.com  These are brand new tubes, manufactured in Tianjin City, China.

Both the 12AX7 and 12AU7’s are 55 dollars each and for an extra 10 dollars per tube you can get the standard 30-day warranty extended to 12 months.  If you listen to your system fairly frequently, I suggest spending the extra 10 dollars, as tubes will usually fail around 1000 hours if they do not exhibit immediate defects.

First test: Phono

The low noise requirements of a moving coil phono preamplifier seemed like the best place to start with the TJ’s, if they could pass this test, I figured they would probably ace serving as driver tubes.  Unfortunately, my Nagra VPS phono stage uses a 12AX7 and a 12AT7, so I’m going to keep my fingers crossed that TJ comes out with a 12AT7 (and a 6922) soon.

The Nagra VPS is a rare component that does not respond well to tube rolling.  I’ve yet to use a vintage NOS tube that has done a better job than the standard, handpicked EH tubes that Nagra chose for duty in this preamplifier.  Swapping the EH 12AX7 for a very expensive Telefunken just muddied up the midrange and switching to a Mullard slowed down the presentation and increased background noise.

The TJ was a much different story, this tube showed an improvement across the board.  Dynamics were increased, with extension at both ends of the frequency scale, without any harshness.  I dragged out a few favorite warhorses that I’ve heard quite a few times to make the judgment as easy as possible. Right from the first record, Dire Straits Communique, I was impressed.  My copy of this is just an average pressing that you can purchase in any used record store for about $5 and is somewhat compressed.  Just swapping in the TJ 12AX7 gave this record much more impact and I was hearing some low level detail throughout the record that I had to strain to hear before.  Moving on to the second Chicago album (the current Rhino remaster) had the same result.  When using the stock 12AX7, the horns in “25 or 6 to 4” seemed to be on the same plane as my MartinLogan CLX’s, but with the TJ 12AX7, the horns jumped out of the speaker plane and were right in front of me, with the image having much more front to back dimensionality.

Second test:  Driver

The next step was to pop a pair of TJ 12AX7’s and 12AU7’s in one of my Prima Luna Dialogue 7 monoblocks while leaving the other one as it came from the factory.  This time switching to the Harbeth Monitor 40.1’s, I played a handful of Classic Records recent mono jazz releases and switched back and forth between the left and right channels, both receiving the same mono signal, leaving no doubt to the change.

In case you are not familiar with the Prima Luna amplifiers, they are somewhat on the warm, lush side of the tonality scale, which is more often than not a good thing.  You can get a slightly more modern tube amplifier sound by swapping the KT88’s for some NOS Tung Sol’s or similar, but those tubes are fetching upwards of 250 dollars each these days.  That shakes out to almost half the original purchase price!

Fortunately, you can get very close to the same effect with the TJ’s.  If you like the more vintage sound of the Prima Lunas, stick with the stock tubes, but if you would like more punch, this is a great investment that won’t break the bank.

TJ’s for me!

The only thing that can’t be verified at this time is how long these tubes will last.  My experience with current stock Russian and Chinese tubes has shown a lifespan of about 3000-4000 hours with a failure rate of about 25%, so this will remain a question mark for now.  I’ve been running the 12AX7 in my Nagra VPS, which sees about 12 hours a day duty and my trusty Radio Shack stop watch is up to about 1400 hours with no problems so far.  I’ll be sure to report back in about a year, when I’ve run the clock beyond the 5000-hour range.

For now, the TJ’s are highly recommended if the tonal changes I’ve mentioned sound like a plus to you.  I’ve always had great luck with the folks at Grant Fidelity, so you can shop with confidence.

http://www.grantfidelity.com