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Audio Research VT80SE Power Amplifier

Audio Research VT80SE Power Amplifier

Audio Research Corporation, the company that almost single-handedly created high-end audio electronics, not to mention preserved the vacuum tube as an amplification device, recently revised its basic line. As it has become the foundation for ARC’s more expensive gear, it is appropriately named the Foundation Series and comprises the LS28 linestage (a 2017 Golden Ear Award recipient), DAC9 DAC, PH9 phono preamp, and VT80SE power amplifier. Each of the first three pieces of Foundation Series equipment is priced at $7500; the much larger and heavier VT80SE is $8900. Starting out as the VT80, after a short production run the amp was upgraded to the VT80SE, of which the review unit was the first production sample. The only difference between the VT80 and VT80SE is that the SE’s tubes are more expensive Tung-Sol KT150s, and the price of the amp has therefore increased. (Audio Research uses the upgraded KT150s in all its amplifiers.)

All Foundation Series equipment shares similar stylistic features, making them a recognizable family, which must be helpful at hi-fi shows. Although it’s the least expensive in Audio Research’s line, the Foundation line could hardly be called budget gear. And it doesn’t try to be, offering a rich feature set that competes with almost anything on the market, and sound quality that compares favorably with anything I’ve heard, though I deliberately avoid most of the stratospherically priced gear out there—my way of preventing severe damage to my bank account. All Foundation Series components have similarly styled front panels, along with Audio Research’s signature rack handles and black-glass windows inset into brushed aluminum (black or silver) faceplates. While the other Foundation Series components make good use of the black-glass windows to display lots of operational information, the VT80SE’s faceplate is strictly for style; the only information displayed there is a pilot light telling you if the amplifier is turned on. Otherwise, the VT80SE is a large, low, open-chassis amplifier with a typical layout: transformers and output tubes in the rear, input tubes in the center, input and output jacks on the vertical rear panel. Of the many Audio Research amplifiers I’ve seen, very few have equaled the VT80SE’s attractiveness—accolades to the ARC design team. VT80SEs sold outside North America get a tube cage, which covers both tubes and transformers. (The cage is a $500 option on North American units, but necessary if anyone in your household has tiny fingers or noses that need to be protected from hot tubes.)

The original VT80 incorporated one of the biggest tech advances in Audio Research history, an automatic biasing system aimed at reducing the routine annoying maintenance required when you use a tube amplifier—prompting a rousing hooray from me! It’s the first automatic bias system ever used in an Audio Research amplifier, making replacing the output tubes just a matter of plugging new ones into the sockets. The automatic bias circuit also adds flexibility to your amplifier; in addition to KT120 and KT150 tubes, it lets you use 6550, KT88, or KT90 output tubes. If you have a stash of compatible octal-based bottles, you will probably want to see how the VT80SE sounds with different types. However, I suspect most of us won’t ever avail ourselves of that feature. I think the most useful aspect of the automatic bias circuit is to adjust the bias to let each tube perform at its best throughout its life span, even when it starts to age.

Speaking of life spans, in the VT80SE the KT150s should last 3000 hours (versus 2000 hours for the KT120 tubes in the VT80)—a long time, depending on how you run the amplifier. But unlike some solid-state amplifiers, you don’t want to leave the unit on continuously. If you use the amplifier two hours a day, five days a week the tubes should last six years. The only change to the SE version is the tube upgrade; if you decide to upgrade the tubes yourself, a new set of KT150s will set you back $1275. Other than longer tube life, no other specifications have changed.

To track how long the tubes have been in use there is a tube-life meter, located on the rear panel next to the IEC jack for the power cord. The meter’s placement makes it rather challenging to read, but it’s not something you need to check frequently, thanks to the auto bias circuit.

Tubes eventually wear out, so when it’s time to replace them, keep this information from the VT80SE press release in mind: “It is important to mention that the KT150 tubes supplied by Audio Research for all of our products are specially produced to our high standards, are tested and measured for quality control and assurance, and are burned in for 48 hours. Then using our Certified Matched process, they are hand matched in sets with tolerances 10x tighter than standard off-the-shelf tubes, thus ensuring the finest audio quality possible.”

The VT80SE has no remote control, but since all a remote would do is turn the unit on or off, there’s no real reason for it. If remote turn-on/off is important to you, you can always use the 12-volt remote turn on/off connections. Many preamps, including the VT80SE’s Foundation Series companion, the LS28, have the necessary 12-volt output jacks that will turn the VT80SE on or off when you turn the linestage on or off with the preamp’s remote control.

When an output tube fails, it usually becomes noisy or just stops working. Occasionally, however, it will arc in a shower of sparks accompanied by loud noises, and sometimes will even destroy a nearby resistor in the circuit. To prevent such a catastrophic failure, each of the VT80SE’s output tubes has its own fuse, which blows if the tube blows, protecting the rest of the amplifier. The fuses are located on the bottom of the circuit board near the tube they protect, and aren’t externally accessible. That means you must remove the bottom panel of the amplifier to replace a fuse. This happens very rarely, fortunately. If you want to try KT88 and KT90 tubes you must purchase them from another vendor, preferably in a matched quad set.

The driver tubes are two of Audio Research’s favorite 6H30 triodes (one per channel), each equipped with two damping rings around the top of the glass envelope. Life expectancy of the 6H30 tubes is 4000 hours. Unfortunately, the tube timer can only show the time on either the output tubes or the low-level tubes, not both—so you will have to track wear on the 6H30s separately. Like most Audio Research electronics, input circuitry is really a hybrid design, with triode-like JFETs as well as tubes amplifying incoming signals.

For those who think tube amplifiers must be noisy, the VT80SE has a 112dB signal-to-noise ratio—quieter than many solid-state amplifiers. It uses the same output transformers as Audio Research’s Reference 75SE amplifier, and is rated at the same 75 watts/channel output power, although the Reference 75SE accepts only KT150 output tubes and uses its front panel meters to set bias voltage—which isn’t difficult, but isn’t automatic. I suspect some users will enjoy the Reference 75 SE’s hands-on manual bias adjustment.

On the rear panel, there’s an IEC socket for connecting a power cord. Note that it’s a 20-amp connector, so your collection of 15-amp power cords won’t work unless you use an adapter. Why does Audio Research use a 20-amp connector? Dave Gordon, brand ambassador, told me: “The 20A IEC connector makes a tighter connection than the 15A IEC. We also spent a fair amount of time comparing 20A power cords, and we think the 20A cord sounds better.”

The rear panel has both balanced and unbalanced signal connectors, along with a switch to select one or the other. The amplifier’s circuitry is balanced, so the balanced input should sound better. The VT80SE sits on standard Audio Research feet, which absorb vibration and don’t make rings on your furniture. There’s also a switch that turns the amplifier off after it’s not used for two hours. (See the next section for some comments on that feature.) Finally, there are gold-plated binding posts for connecting four-ohm or eight-ohm speakers.


Setting Up and Using the VT80SE
The first decision was where to place the VT80SE? Its 19″ by 18.45″ size would fit my rack shelves, but its 10.33″ height was challenging; tube amps produce a lot of heat and need plenty of airflow for ventilation. The only shelf on my equipment rack large enough to support the VT80SE was the top shelf, which is about 50″ high, so with some help with the heavy lifting, that’s where the amp went, a location with abundant ventilation. An unexpected benefit was that top-shelf placement positioned the otherwise hard-to-read tube-life meter at eye level from the back of the amplifier. I used Audience Au24 SX balanced interconnects to connect the VT80SE to my LS28 linestage, another Foundation Series component. Audio Research expects reviewers to use the stock power cords, which is reasonable—otherwise, reviewers would use a variety of cords, and no two VT80SEs would sound the same. The stock power cord isn’t necessarily a disadvantage; if you’re used to disposable power cords, the VT80SE’s stock cords may surprise you. I’ve seen aftermarket power cords that were flimsier. Being an audio nerd, I couldn’t resist trying an aftermarket cord, however, and liked the results I achieved with a Shunyata, which had a 20-amp IEC connector. I used my regular Crimson RM Music Link loudspeaker cables.

For normal listening, I augment my Affirm Audio Lumination horn-loaded speakers with subwoofers, but for amplifier reviews that doesn’t work, since I’d be listening to the bass from the subwoofer’s 1200-watt internal amplifier in addition to that of the VT80SE. So I disconnected the subs and ran the Lumination speakers full-range for the review. Like most horn speakers, the Luminations are quite sensitive, so to see how the VT80SE drove normal sensitivity speakers, I borrowed the KEF Q700 speakers from my smaller system. The KEFs have decent bass extension, and their 89dB sensitivity benefits from ample power. The VT80SE drove them effortlessly.

Since the VT80SE’s automatic biasing circuit is one of the main features of the amplifier, I had to try it out, replacing the stock KT150s. I’ve always liked the sound of KT88s, so I borrowed a set of those from an audio buddy. As far as I know, Audio Research has never used KT88 tubes, although they are favored by sister company McIntosh, so I figured they would be a good test of the circuit. A simple remove-and-replace operation (with the amplifier turned off, of course) was all it took, and I was soon listening to KT88s. How did they sound? I expected a rather perfunctory audition, with the KT150s blowing away the borrowed Electro-Harmonix KT88s. Hah! To my surprise, the KT88s more than held their own, sounding quite open, harmonically rich and detailed, and a bit brighter than the KT150s. I lacked the test equipment to measure power output, but with my rather sensitive horn speakers I didn’t notice a significant loss of oomph with the KT88s, although I’m sure there was one. A full review of the amplifier using KT88 tubes would be fun.

A sticker on the VT80SE’s front panel advised me of a new feature—there’s a switch on the back panel that turns off the amplifier after two hours in the absence of any input signal. That sounds like a nifty tweak, which will keep you from burning up those expensive tubes, but it turns out that this feature not only works when the signal is absent but also when the signal is lower than some unspecified level—so even when a low-level signal is present, the timer turns off the amplifier. That happened several times while I was breaking in the amp at a low volume. Fortunately, the switch can disable this feature, so that the amplifier never turns itself off. After I selected that setting I never had any more unplanned turn-offs.

The only other operational anomaly I experienced was a slight left-channel pop after the amplifier played for about a minute—nothing that would threaten a speaker. The “pops” disappeared after about 600 hours of use. Other than that, the amplifiers were silent while they were on. They ran pretty cool for tube amps, too, although I still gave them plenty of room for ventilation.

Sofa spud that I am, I longed for a remote control that would turn the VT80SE on and off from my listening seat. I found a cable terminated with 3.5mm plugs and used it to connect the 12V trigger from the LS28 linestage to the VT80SE’s trigger input. Voilà, the linestage’s remote now turned the VT80SE on and off. Actually, that arrangement was better than a separate remote control for the VT80SE: It gave me one less remote to clutter up the coffee table.

Audio Research used to recommend a flat 600 hours break-in, but apparently that scared some customers off, so it has modified its recommendation to say the amp sounds good right out of the box and gets even better with some indeterminate amount of break-in—which is true, although it still opens up and relaxes noticeably with time. So when hooked up and broken in for quite a while, how did the VT80SE sound?

With Affirm Audio Lumination speakers.
The VT80SE had a fast, wide dynamic range, which didn’t compress the music. The dynamics were uniform across the frequency spectrum, so the bass and treble had the same free-flowing power as the midrange. As a result, music exhibited the appropriate scale, either macro or micro.

First up via Roon was my old (it really is old, dating back to 1490) fave “Folia: Rodrigo Martinez, 1490—Improvisations D’Après Le Villancico Du CMP (Anonyme)” from La Folia 1490-1701, ripped to an AIF file from the Alia Vox AV 9805 CD, performed by Jordi Savall and his band of Renaissance music specialists. The piece begins with four strikes on a cascabel, or sleigh bell, each of which sounds slightly different through a transparent component, but often sound alike on a lesser component. On the VT80SE, the strikes sounded slightly but distinctly different, as if the second strike was made from a different angle, demonstrating the VT80’s excellent ability to capture detail. Next, I noticed the drum also was reproduced with plenty of detail, though it lacked the last word in impact and didn’t extend as deeply as I’ve heard from a few other amplifiers. The piece’s lively percussion instruments infuse it with energy and flow. These instruments had just the right amount of transient snap—not too much or too little, and at no time did the percussion merge into a background blur, which often happens with lesser amplifiers. Instrumental harmonics were complete and rich; Savall’s viola da gamba (an instrument which somewhat resembles a cello), sang beautifully, with gorgeous tone. The dynamics of the piece change continuously, but some components make the dynamics appear like they’re changing in discrete steps. Not so the VT80SE. It tracked the continuously changing dynamic levels superbly. The VT80SE threw a wide, open soundstage that spread continuously (there’s that word again) between speakers.

Turning to a much more recent (2016 release) piece, “Snilla Patea” by Bjørn Kåre Odde (176.4/24 MQA/FLAC, 2L), I heard a spacious, wide-open soundstage, where the composer, expertly playing a fiddle, and the Schola Cantorum chorus under the leadership of Tone Bianca Sparre Dahl spun out a simple melody and response that I found quite moving. Odde’s fiddle sounded rich and vibrant, floating in space, while the well-trained chorus was reproduced as a cohesive unit but with the ability to hear individual singers when they took a solo turn. Due to the limits of the PS Audio Bridge II card, the MQA encoding was not decoded to the original recording’s 352.8kHz, but only to 176.4kHz.

Another oldy, “Miserere” from The Tallis Scholars Allegri’s Miserere & Palestrina’s Missa Papae Marcelli (96/24 FLAC, Gimell/Gimell) features a small chorus singing in a church, with a smaller solo group some distance behind the main group. A solo tenor emerges periodically from the main group. The text is Psalm 51. With the main chorus spread across the soundstage, the unusual sense of depth is reinforced when the distant solo group comes in. Through the VT80SE, the reverberation from the intervening space clearly told me the solo group was well behind the solo group. Through some amplifiers the reverberation is overemphasized, masking the sound of the solo group, but the VT80SE makes it sound clean as a whistle. I don’t recall hearing a much better reproduction of the depth of the soundstage. The solo tenor was also reproduced well, with his phrasing and expression sounding very clean—some components make him sound a bit brittle.

Increasing the volume setting in anticipation of its low recording level, I played the title song from Shelby Lynne’s album Just a Little Lovin’ (DSD64/DSF, Acoustic Sounds). As before, I noted a wide-open presentation, with fairly deep bass, energetic cymbals, razor-sharp rim-shot transients, and a tightly dynamic overall sound. The VT80SE reproduced Lynne’s voice with tons of detail and expression, which created a very realistic sonic picture, as though she were in the room singing directly to me. Harmonics were not just rich; they were also accurate. A very enjoyable rendition of a very nice recording.


With KEF Q700 speakers.
The Q700 is a three-way speaker using a version of KEF’s justly famed Uni-Q concentric midrange/tweeter, along with a 6½” woofer with two similarly sized passive radiators. I had been driving the Q700 speakers with an integrated amplifier rated at 80Wpc. It should come as no surprise that the VT80SE was a different sonic ball game, exhibiting a much more accurate harmonic structure, lots of dynamic energy, and considerably more precise soundstaging. Of course, for almost ten times the price of the integrated amplifier, you would doggone well expect better performance.

On “Folia: Rodrigo Martinez, 1490—Improvisations D’Après Le Villancico Du CMP (Anonyme),” the opening cascabels were equally distinctive, but all exhibited more treble extension from the KEF’s Uni-Q driver. Likewise, there was more bass extension, although the bass was somewhat reverberant and echo-y sounding. I think that’s attributable to the speakers, not the amplifier. Percussion instruments were quite audible throughout, and never receded into a background mush. Harmonics were nearly as rich as those of the Affirm Audio speakers, and the dynamic variations were tracked equally well.

“Snilla Patea’s” opening fiddle sounded slightly brighter, and the chorus more wide-open, abounding with detail. There was no trace of peakiness or etch—just extended treble. “Miserere” sounded wide-open, filling the soundstage between the speakers. The distant solo group sounded even more distant, with the reverberant echo sounding quite realistic and unsmeared. The solo tenor showed no trace of hardness or brittleness.

In “Just a Little Lovin’” the opening bass extended more deeply, with more impact. The bass showed little of the echo-y character noted in “Miserere,” but then it doesn’t extend as deeply as the bass in “Folia: Rodrigo Martinez.” Lynne’s voice was quite smooth, conveying the expression with which she phrased the lyrics. Instrumental harmonics were realistic, though perhaps a smidgen less full than through the Affirm Audio speakers.

The VT80SE made the KEF speakers sound better than I’d ever heard them, very smooth, very extended, very detailed.

Rated at only 30Wpc, my David Berning ZH-230 stereo amplifier is an output-transformerless (OTL) unit that dispenses with sonically degrading transformers. Since my Affirm Audio horn speakers are quite sensitive, 30Wpc is more than enough, but many speakers will need more power. The ZH-230 uses only exotic new old stock 33JV6 output tubes—although I suppose you could make a case that the KT150 tubes are pretty exotic, too. Since the Berning amplifier only has unbalanced inputs, I used Audience Au24SX unbalanced interconnects from the linestage to the amplifier. The ZH-230 is an extremely light amplifier; having neither output transformers nor a power transformer (it uses a switching power supply) reduces the weight to 15 pounds. The Berning amplifier rests on Stillpoints OEM feet. The ZH-230 is the best amplifier I’ve heard with the Affirm Audio speakers; would the VT80SE unseat it?

On “Folia: Rodrigo Martinez, 1490—Improvisations D’Après Le Villancico Du CMP (Anonyme),” the soundstage was even wider, and the strikes on the cascabels equally distinct. The bass drum had respectable power and descended in frequency a bit lower than the VT80SE, not surprising, given the Berning’s OTL design. The difference was not substantial, but perceptible. The Berning extracted even more detail from the music than the VT80SE, and tracked dynamics at least as well. The VT80SE seemed to have a bit more harmonic richness than the Berning, which was a little matter-of-fact in comparison. Which amp you’d like better is really a matter of personal preference; on this piece, I preferred the Berning by a very tiny margin.

On “Snilla Patea” through the Berning amp, the fiddle exhibited considerable palpability and presence, with an upfront spatial perspective. When the chorus entered, it seemed to be slightly more separate from the fiddle than it was with the VT80SE. On the other hand, through the VT80SE, the fiddle sang with a richer sound. The Berning amp provided a very slightly more detailed depiction of the chorus, however.

On “Miserere” the distant chorus was slightly less distinct with the Berning amp—the reverberant echo perhaps a little smeared compared to the VT80SE. But the Berning depicted the solo tenor’s voice with a tad more detail.

“Just a Little Lovin’” opened with a strong bass, and the other instruments were more detailed through the Berning. The Berning also reproduced dynamic contrasts in Lynne’s voice more clearly, making it more expressive.

Each amplifier had its strengths. The Berning was generally slightly more detailed; the VT80SE, more harmonically rich and just prettier sounding. They were both very enjoyable, but the VT80SE produced over twice as much power as the Berning, making it more capable of driving lower-sensitivity speakers like the KEF Q700s. I don’t believe the Berning is in current production, so there’s really no choice between them. If there were, I would be happy to live with either amplifier. The differences noted were really quite slight.

To find currently produced competitors, one only has to look within Audio Research’s own lineup: the $10,000 Reference 75SE, a classically-styled Audio Research amp from the series above Foundation; and the $8500 VSi75 integrated amplifier. Both use KT150 tubes to produce a rated 75Wpc. The VSi75 is smaller and lighter than the VT80SE, but includes a full-function linestage, almost like getting a free LS28! Well, not quite; the VSi75 has only unbalanced inputs. There’s a front-panel readout that shows tube hours, and also provides a manual bias setting readout, no match for the VT80SE’s automatic bias circuit. All that’s missing is a line output for bi-amping or subwoofers. Unfortunately, I had neither of these amplifiers for a comparison. If tube rolling (tuning the amplifier’s sound by changing to other brands of tubes) appeals to you, the VT80SE is clearly the way to go.

Bottom Line
The Audio Research VT80SE looks great, sounds great, and is built like the proverbial brick outhouse. Its automatic bias circuit makes it far easier to use than most tube amps, and its individually fused tubes protect it against catastrophic tube failure. If you have a stash of favorite octal-based output tubes, the VT80SE may be able to use them, although it’s furnished with the extremely popular KT150s. The Audio Research VT80SE earns my very highest recommendation.

Specs & Pricing

Type: Tube/solid-state hybrid stereo power amplifier
Output power: 75Wpc into 4 and 8 ohms
Inputs: Unbalanced RCA jacks or balanced XLR jacks
Tube complement: Two 6H30 drivers, four KT150 power output tubes
Input impedance: 300k ohms balanced, 150k ohms unbalanced
Dimensions: 19″ x 10.33″ x 18.45″
Weight: 45.7 lbs.
Price: $8900

3900 Annapolis Lane North
Plymouth, MN 55447
(763) 577-9700

By Vade Forrester

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