Audio Research GSi75 Integrated Amplifier

It’s been a couple of years now since the Audio Research GS series have been introduced, and both the GS Pre and GS 150 have received multiple awards from magazines around the world (including us).

With its gorgeous, artisan style, the GSi75 shows off a welded chassis, thick front plate and the combination of new and old ARC cues. Some deeply embedded in the way Audio Research used to do things see the GSi75 as anomalous, but ARC’s Dave Gordon sets me straight, “Don’t think about the GSi75 as you do our other components. Yes this is a lifestyle piece, but it is one for someone who truly cares about sound quality.” It only takes about 2 minutes of listening to see he’s spot on.

Streaming Teenage Fanclub’s “Don’t Look Back,” with it’s layered, grungy sound and simple pop hooks gets to the heart of the matter immediately. This combination of DAC, phonostage, headphone amplifier, and 75 watt per channel power amplifier has a very spacious sound. Segueing to “The Journey” from Boston’s Don’t Look Back, the deep bass riff at the end of the track convincingly illustrates this amplifiers ability to move some air.

Having spent the better part of the year listening to the GS Pre and the GS 150, it’s intriguing that the overall voice of the GSi75 feels closer to that of the last generation REF series than the slightly mellower voice of the GS Pre/GS 150 combo. With four KT150 power tubes and a pair of 6H30s, nothing deviates from the current ARC cookbook. The power supply has a capacity of 330 joules instead of the 500 supplying the REF 75, so don’t expect quite the drive of the REF amplifier, even though both are specified to produce 75 watts per channel. At all but brain damage volume levels though, the GSi75 comes very, very close.

What, no XLR’s?

In the effort to keep things tidy, the usual balanced inputs are absent. No doubt because the phonostage and DAC are already on board, it makes sense that the options can be kept easy for other components. Other than a tuner, what else would you connect, except maybe another phonostage or a tape deck? Yet in typical Audio Research fashion there are still three single ended RCA analog inputs, to go with the single phono input.

The phonostage in the GSi75 is a marvel of compactness and again, showcases ARC’s ability to design world class products in either arena; tube or solid-state. Gordon laughs as he says, “We just didn’t have the room inside the chassis for a tube phono.”

Compact as it is, the on-board phono section still features low and high gain settings (45 and 62db) along with the ability to set phono loading at 100, 200, 500, 1000 or 47k ohms. And, it’s adjustable from the remote control. Impressive.

A powerful soul

Dropping the needle down on a fresh copy of Crowded House’s Woodface, the room is immediately filled with the big, broad, engaging soundfield that I’m used to listening to a full compliment of REF components in my larger listening room. The core competencies of ARC still come through brilliantly, with mix of dynamics, speed, transparency and an incredibly natural tonal balance.

Where all but the REF Phono 3 and REF Phono 10 phonostages ($14,000 and $30,000 respectively) offer high and low gain settings, the rest of ARC’s phonostages all have settled on a fixed gain setting of 58db, which is more than adequate for most cartridges and situations, I found the two gain settings helpful, especially with my Dynavector 17D3 and Denon DL-103r cartridges.

The onboard phonostage, is quiet and dynamic. A perfect match for the rest of the amplifier, and putting it to work with a wide variety of phono cartridges from the $100 Shure M97 all the way to the $10,000 Koetsu Jade Platinum, I never found the onboard phono to be limiting, though with the big boy cartridges, there is a slight bit of resolution and ultimate dynamic drive that is better served by the REF Phono 3. However, I suspect that most building a system around the GSi75 are going to be bridging the gap between “really good” and “sky is the limit” systems. In the context of a nice $3,000 – $15,000 turntable/arm/cartridge combo, I doubt you’ll be aching for more phono performance.

At all but maximum volume through inefficient speakers, you’ll be hard pressed to tell the GSi75 from the GS Pre and GS 150 amplifiers. Driving the Focal Sopra no.3s, which have a sensitivity of 92db/1watt, I can’t drive the amplifier into clipping, it plays plenty loud for my needs. It proves equally capable driving the Quad 2812s, which are notoriously tough, because of their heavy capacitive load. The loopy, spacy, electronic vibe of the first Neu! album is a sonic treat, with little sounds bouncing all around my listening room with the Quads, it’s almost like being in a gigantic pair of headphones.

Again, Gordon tells me “the heart of this amplifier is a REF75 circuit – same tubes and transformers with a passive preamp section, that’s why there is no preamp out. The DAC is all new and one of the best we’ve ever done. It’s what formed the heart of the DAC 9.”


Catering heavily to the new music consumer, that DAC allows you to access whatever files you have on hand; 16-bit/44khz all the way up to 2x DSD, so you won’t be left out in the cold. There are a bevy of digital inputs as well; RCA, Toslink and USB all help make the GSi75 the hub of your digital music world. Having the DAC 9 on hand for review, it was easy to compare between the two and the

GSi75 is indeed highly capable. Thanks to Roon, my digital library is a gaggle of files on a 13TB NAS drive, with no particular segregation from low to high resolution. The GSi75 sailed through playlist after playlist, consisting of every resolution possible, without so much as a pause.

Using a Mac Book Pro, dCS Paganini transport, a Meridian/Sooloos MC200 Core and an Aurender A10 allowed checking every input and all worked flawlessly. No matter what you have at your disposal, rest assured the GSi75 can handle it.


If all of this weren’t enough, the GSi75 also has a headphone jack, and again, the solution was done from the ground up. Even this aspect of the GSi75s performance was by no means an afterthought. While this reviewer is not a huge headphone listener, the quality of the sound heard through Audeze LCD-2s and the current Oppo PM-1 phones is top notch.

All but the most maniacal headphone listener will not need an outboard headphone amplifier. The GSi75 has much more sheer drive than is necessary to achieve the volume level you require, and the level of refinement is exceptional. Going through all of my favorite prog and electronica tracks made for an aural playground with the GSi75. Cheech and Chong’s Big Bambu was not only a great throwback, but fully illustrated the high level of imaging prowess that placed the people speaking everywhere in the room. Big fun.

The Audeze and Oppo phones are not terribly hard to drive, but the planar magnetic phones seem to deliver a more sophisticated presentation, the better your gear is. Again the GSi75 did not disappoint in any way. Bass was always solid and full of tonal richness, with the high frequencies tight, defined and (for me, anyway) a perfect mix of extension and resolution without ever sounding strident.

Complex yet simple

The $16,000 price tag may stun a few at first, but when you realize what the team at ARC has packed inside the GSi75, and the fact that you don’t have to buy three sets of interconnects and power cords, it’s an amazing bargain – for the right customer. Because everything is inside and there is no preamp out, this is either a piece you will live with forever, or the upgrade bug will sour you. A cursory survey of a few friends with mega ARC systems reveals more than one have bought a GSi75 as the core of their second system, or vacation home system and are thrilled.

Careful inspection of the chassis, and the parts quality inside, it becomes immediately obvious that the GSi75 was built to a standard – with no compromise rather than scaled up from a price point business model. The GSi75 is Audio Research through and through.

The “ears” of Audio Research, Warren Gehl is quick to add that an integrated was part of the product mix with the G Series all along. “We wanted to see how far we could take the G Series with this concept.” It ends up being a fairly dense circuit board when you remove the bottom cover, but again, Gehl backs up their decision to use PCBs instead of point to point wiring, simply saying “We take a very logical perspective to circuit board layout and construction quality. We don’t feel our designs take a back seat sonically to an amplifier that is wired point to point.”

Quantifying the value in the GSi75 is an easy task for someone who’s been living with ARC electronics for nearly as long as they’ve been making them. Perhaps a result of getting a bit older, I’ve experienced a number of friends when listening to a large rack of gear ask the question, “can’t I just get this kind of performance in one box?” And this comment is usually followed with something like, “I want really great sound quality, I just don’t play music as loud as I used to.”

It’s like the dining room of my favorite local hotel. They’ve started offering just a spoonful sized portion of their favorite deserts. This is the essence of the Audio Research GSi75 – it’s a heaping tablespoon of a full REF stack. And for many people, that will be all you need.

The Audio Research GSi75 Integrated Amplifier

MSRP:  $16,000


Analog Source               Brinkmann Bardo Turntable/Koetsu Onyx Platinum Cart

Speakers                         Focal Sopra no. 1, Quad 2812, GamuT RS5i

Cable                               Cardas Clear

iFi Retro 50

Knowing that a quartet of EL-84 tubes lurk under the hood of the iFi Retro 50, I knew it was time to break out the JBLs – and it was good. Just as with the Dynaco SQA-35 and even the Manley Stingrays, there’s just nothing like the sound of a pair of JBL L-100s driven by an EL-84 amplifier. Those little tubes have a soft-spoken magic about them that can’t be duplicated by the EL-34 or even an SET amplifier. And the slightly soft character of this output tube goes miles towards taming the upper register of the L-100s.

Listening to the bongos bounce around the listening room during the opening of Curtis Mayfield’s “Pusherman” is delightful, and when his voice folds into the mix, it comes across much larger than life. If I didn’t know better, I’d swear the Retro 50 was something that has been in a box for 50 years, the dust just shaken off. It really does groove, with an abundance of musical detail as well – it doesn’t just round all the transient attack off to sound groovy. The sound is just more saturated throughout.

Regular readers of TONEAudio know that we’ve given iFi’s compact DAC and phonostage rave reviews. They pack major performance in a small form factor and keep the price down as well. So far, we’ve seen no downside to any of their products that we’ve sampled. The Retro 50 has both of these and a great headphone amplifier – all on this compact chassis, encased in a bamboo enclosure. Now that’s something you never saw on a vintage receiver from the ’70s!

The Retro 50 comes packaged with a pair of iFi’s Retro 3.5 speakers for $1,995. Unfortunately at this time, you must buy the combo; the Retro 50 is not available by itself.

Investigating those little speakers

iFi calls the speakers accompanying the Retro 50 “Retro 3.5” in homage to the legendary LS3/5A BBC monitors. The similarity to the LS3/5A ends with the form factor. They don’t really suck, but they don’t really rock either. Judicious use of the tone controls and signal processing at your disposal on the front panel of the Retro 50 mitigates this, but they perform much better in a desktop system than out in the listening room. Sold alone, they carry a retail price of $795 – forget about them at this price, but as part of the Retro 50 system, not bad.

Fortunately, the Retro 50 is so undervalued, even if you throw the speakers out, it is still more than worth the $1,995 that’s asked. $1,500 for the Retro 50 alone would be the audio bargain of the 21st century, maybe forever!

Even after a lot of break-in time, the Retro 3.5 speakers still sound small. Discerning use of the tone controls and the 3D sound processor help tremendously, yet using them in a room much larger than 11 x 14 feet for anything more than background fill is not suggested. Nearfield in my small second listening room is pleasurable, but the speakers still sound overly polite, without having the body that a real pair of LS3/5As possesses.

The best place for the Retro 3.5s proves to be on the desktop, flanking a 27-inch computer monitor, with a slight tip-up. A bit of toe-in goes a long way, looking for a balance between soundstage width and bass reinforcement. iFi makes it painless for the audio enthusiast to get down to business with audio, USB and speaker cables included in the box. Obsessed audiophiles will want to upgrade these later, and the Retro 50 responds well to a premium wire upgrade.

No matter how you enjoy music, you’re covered

Whether digital, analog or wireless, the Retro 50 can handle your source components. In addition to a cracking MM/MC phonostage and DAC, there is an antenna to stream digital files via your smart device, too. For the foreseeable future, the Retro 50 is “obsolete-proof.”

The Retro 50 is capable of decoding both DSD and DXD files, and this was the only part of the Retro 50 that I did not explore. With all the rage surrounding this, I just can’t get conned into buying my favorite music again. But for those of you who are new to the game and investing in these files, you are good to go. If the 24/192 performance of the Retro 50 is any indication, you will not be disappointed with DSD reproduction.

The coaxial and optical digital inputs accommodate files up to 24/192, while the USB input goes all the way up to DSD 512. With 24/192 files, it is virtually a dead heat between the inputs in terms of sound quality, so whatever strikes your fancy will work well. The gadget geeks in the audience will appreciate the digital input logo changing color with file resolution, just like AudioQuest’s Dragonfly. iFi’s choice of the aptX codec is a great move, so those using other than Apple iDevices will be very happy. Streaming from a Galaxy phone over Bluetooth is stunningly good with Tidal, and for this writer, all I’d ever need on a desert island are the Retro 50, a pair of JBL L-100s and a Galaxy phone with a Tidal subscription (along with good reception, of course!).

Inputting via analog sources works equally well for those feeling more traditional. The phono section of the Retro 50 is identical to that of the iPhono that Richard Mak reviewed here. It’s worth noting that separate MM and MC inputs with 50 and 62 dB of gain are offered, proving perfect for the AVID Ingenium turntable with two tonearms – one utilizing an Ortofon SPU cartridge and the other a vintage Ortofon VMS20 Mk.II. As Mak found in his review of the iPhono, this phonostage is quiet, dynamic and tonally correct. I also had excellent luck with the Denon 103r, Ortofon 2M Black and Grado Statement cartridges. Unfortunately, the Retro 50’s phonostage does not offer the gain and loading adjustments of the iPhono, but only so much can fit on this small chassis. Regardless, it provides an excellent avenue for your vinyl journey.

Further listening

The Retro 50, regardless of input, is dead quiet. Even with ears placed right against the tweeters, there is no noise or tube rush coming from the speakers. Though the Retro 50 claims 25 watts per channel, considering that most other amplifiers designed around a pair of EL84 tubes produce about 15–17 watts per channel, I’m guessing the numbers here are slightly optimistic.

What is important is the quality of the sound that the Retro 50 does produce. Regardless of speakers used from the $88,000/pair Dynaudio Evidence Platinums all the way down to my JBL L-100s, the extended high end and LF control is surprisingly good. By contrast, a vintage Dynaco SCA-35 (also using a pair of EL84s per channel) sounds extremely soft and much noisier. Because the iFi uses a more modern implementation of the circuit and a beefier power supply than my SCA-35, it sounds louder, even though both hit the same sound pressure level. Remember, volume is the difference between loud and quiet, so while the Retro 50 may not actually produce 25 watts per channel, because it is incredibly quiet, it sure sounds like it puts out that kind of power.

This amplifier is all about quality and delicacy. Regardless of the speakers you choose, the Retro 50 conjures up a soundfield that is both wide and deep. Tracking through Neu! is an amazing exercise in trippiness, with cool sound effects all over the room as if you were nestled in between a six-foot-tall pair of headphones.

The Retro 50 doesn’t so much color the lush midrange as maximize texture and tonal saturation. This amplifier is perfect for listening at low to moderate levels.

Acoustic guitars have an extra dash of ambience and thickness about them. Listening to the snap of the acoustic guitar on the title track of Michael Hedges’s Aerial Boundaries is simply breathtaking. And, of course, solo female vocals are incredibly sexy as well.

Perfect for personal fidelity

Auditioning a small cache of headphones also proves the Retro 50 fabulous. Thanks to its 3D holographic image processor (with three settings) and XBass processor, you can fine tune your headphone experience. The Audeze and OPPO phones sounded the most natural with no processing applied, but with some lower end Grados and a few in-ear phones, the option for extra bass really came in handy. The 3D processor was fun, but it felt more like a slight sampling of an illegal substance rather than realistic. And for some that will be a good thing – sample to taste. Fortunately the Retro 50 gives you plenty of options, along with a very useful bass and treble control.

Whether you find joy in this ability to alter your system’s playback with loudspeakers is up to you, but it is wonderful that iFi has included them, especially at this price. The only thing lacking a bit is the aesthetics. The bamboo casework is a home run, but the front panel, printing and control knobs are slightly cheesy, reminiscent of early Chinese hifi – and not a reflection of the sound quality inside the box. I’d happily pay an extra 100 bucks for an upgraded front panel, but that’s my inner interior designer screaming for order.

Like every other iFi product we’ve used or reviewed, the Retro 50 screams high performance and high value – more than worthy of one of our Exceptional Value Awards for 2015. Whether you use the speakers or give them to a friend, the Retro 50 is one of the greatest combinations in the audiophile world today. I can’t think of a better place to start your high end audio journey.

iFi Retro 50

MSRP:  $1,995 (with Retro 3.5 speakers)


Analog source AVID Ingenium turntable w/SME 3009 and 309 tonearms    Denon 103   Ortofon SPU     VMS Mk. II cartridges
Digital source OPPO 105 (as transport) MacBook Pro
Speaker JBL-L100    Dali Rubicon 2    Dali Epicon 8    GamuT RS5
Cable Cardas Clear Light

TJ Music Full Music Vacuum Tubes


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  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.

tj_2Second 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.