The Audio Research PH9

Audio Research always has something new under the hood of any new release, but their new Foundation series is a major step up aesthetically as well.

We’ve just received the entire series in for full review, but we’ve started with the PH9 phono stage. At $7,500 it will be an interesting comparison to the REF PHONO 3, also in for review (and destined to stay here after as a reference component) to see what the extra $5,500 buys you beyond a second input and balanced outputs.

Stay tuned!

Coffman Labs G1-A Preamplifier

With the renaissance that vacuum tubes have been undergoing for the last decade or so, it’s more challenging than ever to create a tube preamp that stands out from the pack.

So when engineer, musician, physicist and Portland local Damon Coffman told me he designed a new preamp that’s “amazing,” I was a bit skeptical.  But when I saw Coffman’s creation, the G-1A, upon a recent trip to local gear shop Echo Audio, it was like catnip.  The unique casework caught my eye instantly, where fledgling manufacturers usually fall short—think steampunk meets art deco, fused with some mid-century modern.  The shop’s wry owner, Kurt Doslu, who is usually the one curbing my enthusiasm, showed me the nifty little preamp.

“Kurt, what’s this?” I asked. “Oh, it’s this new preamp that we’re going to be distributing,” he replied. “It’s pretty good, want to take it home and give it a listen?”  And so the adventure began.

The G-1A has an MSRP of $5,495 and, at present, is only available through Echo Audio in Portland.  There will be a total production run of just 500 units and the first 25 have already been pre-sold—impressive for a new product.

A two-box design, with an outboard, tube-rectified power supply, the G-1A is a full-function preamplifier.  It has a phonostage, with moving-coil (via step up transformer) and moving-magnet inputs and a headphone amplifier built in, which is a lot of capability for that price point.  The G-1A features a single-ended design throughout, with premium RCA connectors for the four high-level inputs and two phono inputs, along with two fixed high-level outputs and a tape out, which makes life easier for this tape enthusiast.

Circuit Basics

The G-1A uses six vacuum tubes in the main circuit: two 12AX7s, two 12AU7s and two 5687s, with a 5AR4 in the rectifier position.  The preamp  ships with standard-issue, current-day production tubes, leaving things wide open for tube rolling—but the G-1A was so enjoyable as delivered, I’ll leave tube rolling for a future blog post.

Coffman says that much of the impetus for the design of the G-1A came from revisiting classic tube designs from the 1920s, when “the original concepts in tube audio” were born.  As a result, his preamplifier is a masterpiece of simplicity, even down to the number of screws holding its case together.  Inside, we see a mix of new and classic parts.  Coffman sourced a number of oil and paper capacitors (“NOS KGB items”) and an input selector switch from the aerospace industry.  He also went so far as to hand-select and measure every single component for sound quality and durability.  Yet, even with this bespoke approach, Coffman’s training in the medical-instrumentation field drove him to streamline the manufacturing approach to assure consistency from unit to unit.

A concert violinist with a master’s degree in physics, Coffman made his mark in the medical electronics industry by producing digital stethoscopes.  A hi-fi guy since his early teens, he admits that building this preamplifier was, in many ways, even tougher than building his stethoscopes.  And most importantly, Coffman is a music guy through and through; his wife, daughter and parents are also musicians. So he is constantly asking himself if the sound is natural.  With the G-1A, a result of two years and countless prototypes, Coffman has finally answered that burning question in the affirmative.

Stunning Musicality

Wanda Jackson’s 2011 release The Party Ain’t Over is a dense recording and, as the first album on my long listening list, established that the G-1A has a timbral clarity that is unmistakable.  The upright bass at the beginning of “Rum and Coca Cola” has a loose, resonant, almost unturned quality such that you can actually hear the bass rattle—and the G-1A brings all this detail front and center, capturing every bit of texture available.

Zooming through some audiophile standards proves equally rewarding.  Listening to the Doors and the Grateful Dead in 24/96 was a spectacular experience with this preamp.  The soundstage that the G-1A presents is enveloping, dishing up the magic you usually have to spend five figures to achieve.  This preamplifier produces a stereo image that extends well beyond speaker boundaries on all axis—of course, the better the source material, the better the result.

The true triumph of the G-1A is its effortless reproduction of acoustic instruments.  Acoustic playback is a must considering Coffman’s background.  The tonal accuracy of piano, violin and drums must be experienced to be believed.   The gentle tap of Phil Collins’ drumstick on the snare frame in the title track of Brand X’s album Unorthodox Behaviour was scarily real. That extra dollop of texture the G-1A provides seems to come from nowhere and yet still makes itself known.

The sparse drumming and percussion in this record, with its almost Zappa-like triangle taps and bells at the far corners of the soundstage, show off the immediacy that the G-1A delivers.  No matter how complex the musical passage, there’s always enough headroom to accommodate another instrument in the mix.  This level of dynamic competence at both ends of the scale is rarely found without spending a lot more money.

Not Terribly Tubey

While you won’t mistake the G-1A for a solid-state preamplifier, much like my Audio Research REF5 SE, the Coffman preamp is highly accurate, with that extra bit of airiness suggesting vacuum tubes under the hood (or, in this case, poking out of the top of the hood)—and nothing more.  Where a few of my favorite tube preamplifiers of old injected their share of warmth and often coloration, the G-1A plays it clean all the way.  It is worth noting, however, that this one really needs a good hour to warm up.  At initial power-up, it does sound a bit thinner than some of the other tube preamplifiers we’ve experienced.  But to complement the highly resolving nature of the G-1A, it is equally well represented in the lowest octave.

Because the G-1A offers such a great balance, I did not spend any time tolling tubes in search of a different “tuning.”  I’m sure it would be fun to swap the phonostage tubes, because the 12AX7 allows so many different variations on the theme, but we’ll leave that for another day.  Plus, the tall, spun-aluminum towers that ensconce each of the tubes do not make for easy tube swaps, and perhaps it’s for the best.

At this point, we could call the G-1A a “best buy” without the phonostage and headphone amplifier.  As both of these segments practically warrant full reviews on their own, I will go into greater depth on our Analogaholic and Macro sites.

Full Function Phono and Phones

The G-1A includes inputs for MM and MC cartridges.  While everything in the preamp is so carefully thought out, this vinyl junkie would love to see that as a function addressable from the front panel.  Coffman does thoughtfully include a loading switch for the MM input, giving 47K, 70K and 90K ohms, allowing most of my favorite cartridges to shine.  The Shure and some of the Ortofon MM range have a much more open sound when loaded to 70k than at 47k, so this is a nice touch.

The phonostage is excellent, easily on par with anything I’ve heard in the $2,500 range, including the outstanding Manley Chinook, and the G-1A is head and shoulders above the EAR 834P, which is fairly colored in comparison.  Most impressive is the sheer dynamic drive that the G-1A provides, with the same tonality as the linestage.

Soundstage width and depth are enormous, making the freshly rebuilt Quad 57s in my second listening sound like a pair of stacked Quads.  Spinning the recent MoFi remaster of Dead Can Dance’s Into The Labyrinth, the level of detail revealed was no less than stunning.  With a diverse combination of acoustic and electronic elements, featuring male and female vocals, this record gives a quick and accurate read on a component’s spatial abilities.

Sampling a wide range of cartridges, including the Denon DL-103R (and the Zu Audio variation), Ortofon Cadenza Bronze, Ortofon SPU and Clearaudio da Vinci all proved excellent matches with the G-1A.  Unfortunately, the Lyra family of cartridges was not as exciting.  The Atlas, Titan i and Kleos all offered the same result: slightly slow and rolled off, which is likely the result of an obvious impedance mismatch.  There are still a few more on the audition list, so stay tuned for a follow-up on the Analogaholic site.

As this was the first sample from the production line, the headphone stage was not complete at this time, so for now we are concentrating on linestage and phono performance.  A full review of the G-1A’s headphone stage will occur on our website very soon as a follow-up review.

The lack of a remote control proved not to be an issue, especially when moving the G-1A into room two, where the listening chair is directly in front of the main rack, so volume adjustment is easily handled.  Coffman assured me that the output stage of this preamplifier would drive “anything” and, after mixing it up with about eight different power amplifiers and driving 20-foot interconnects, I concur.  Driving a few of my test power amplifiers with one-meter and seven-meter lengths of ALO Audio’s newest premium interconnects reveals no change in sound quality or high-frequency rolloff.

So What Makes This Thing Awesome?

The Coffman G-1A has a unique and striking look and it’s built by a man with a plan.  Some might be surprised by the $5,495 price, but consider this: In the best old-school tradition, the G-1A includes an onboard phonostage (MM and MC) and an onboard headphone amplifier—remember when you could buy a full-function preamplifier with all of this under the hood?

With vinyl still growing in popularity and headphones a full-fledged sub-genre of audio, a preamplifier incorporating these two elements is exciting.  Considering that you won’t have to purchase an outboard phonostage, headphone amplifier or a pair of power cords, the G-1A is fantastic if you value sound quality above everything else. The design is so pure it even lacks a remote control.

Judged strictly as a linestage for $5,495, the Coffman G-1A is at the top of its class.  The fact that it includes an excellent phonostage and headphone amplifier makes it the bargain of the year.  All of the tubes are easily found and those predisposed to tube rolling can tune and tweak until Election Day.   Coffman has plans to expand the lineup, possibly making the phonostage and linestage separate boxes. When I asked him if there might be a companion power amplifier in the works, he smiled that evasive smile that usually means “yes, but I don’t want to talk about it now.”

So with that in mind, we award the Coffman Labs G-1A one of our Exceptional Value Awards for 2012 and look forward to the company’s future offerings.  Coffman is certainly off to a brilliant start.  I have purchased the review sample, so that it can become an anchor component in room two, and so that we can do a long-term report when a year has passed.

The Coffman Labs G-1A Preamplifier

MSRP: $5,495


Analog Source               AVID Volvere SP turntable/SME V, various cartridges

Digital Source                dCS Paganini stack, Sooloos Control 15, Aurender C10

Power Amplifier             Conrad Johnson MV-50C1

Speakers                       Quad 57

Cable                            ALO Audio, Cardas

Power                           Audience AR-6TS

Unison Research S6 Integrated

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   (mfr.) (US distributor)


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