pl | en


Audio Research

Price (when reviewed): 33 000 PLN

Contact: 3900 Annapolis Lane North ǀ Plymouth
Minnesota | USA | 55447-5447



Provided for test by AUDIOFAST


translated Marek Dyba
photo ARC | Wojciech Pacuła

No 220

September 1, 2022

The American company AUDIO RESEARCH CORPORATION was founded in 1970 by WILLIAM Z. JOHNSON. It specializes in building tube amplifiers, although its offer also includes CD players and D/A converters with tube outputs. We are testing its newest integrated amplifier, the I/50, developed to celebrate manufacturer’s 50th anniversary.

HE COVID-19 PANDEMIC, BESIDE ITS TRAGIC EFFECTS, also influenced time. Its gravity created some sort of dilation. Polish writer Olga Tokarczuk received the Nobel Prize in Literature for 2018, but in 2019. The Tokyo 2020 Olympic Games were held in 2021. The same is true for the Audio Research 50th anniversary. Instead of in 2020, the celebration started in September 2021, with introduction of the first representative of the new series, the I/50 tube amplifier, but the first units left the factory only in 2022.

It is the first new device from this manufacturer that was presented after it was sold by the McIntosh Group back to its former sales director. The transaction took place in August 2020. Audio Research belonged to one capital group with the McIntosh for six years. Especially for this transaction, the already mentioned Trent Suggs founded the company called TWS Enterprises, which he fully controls.



The I/50 integrated amplifier is the first product in a completely new series from Audio Research. Handcrafted in Minnesota, the functionally simple, visually appealing, the I/50 is built with the same attention to detail as all other Audio Research products - each unit even undergoes its own listening test before being shipped, performed by the sound designer, Warren Gehl.

A different approach to this product is emphasized many times - and with good reason. On the one hand, it is a classic Audio Research integrated amplifier. The amplification path is based on tubes - 6922 double triodes in the input stage and 6550WE beam tetrodes in the output. At first glance, the device looks similar to previous designs from this company. So there are tubes on the top with transformers behind them. However, when we take a closer look at it, it turns out that it offers a new quality.

The first thing that catches the eye is the color scheme. The I/50 amplifier can be purchased with one of the six colors of the top panel. Among them there is an all-silver version, as well as one with ceramic Cerakote paint, which - as the manufacturer assures - "will look beautiful even after many years of use". A novelty is also the use of a black acrylic panel on the top and moving the knobs there - ones for input selection and volume control.

Another thing that everyone, I am sure, will notice are LED displays enclosed in tube-shaped housings, which show the volume level and the selected input. The manufacturer calls them LexieTube, thus referring to Nixie tubes, in which the cathode was formed in the shape of numbers and when voltage was applied to it, it glowed with orange light.

| Nixie

⸜ Vintage Nixie Tube Clock with six IN-14 Nixie tubes. The clock is offered by a Ukrainian company from Kiev - check out the AMAZON website, where it is available - more HERE • photo Nixie Star

NIXIE IS NOT AN ELECTRON TUBE in the classic sense. It is a "cold cathode" tube. It heats up to a maximum of 40 °C, and the tube does not emit any electrons. In a glass bulb filled with neon and argon under low pressure, there is one common anode and many cathodes. They are shaped into numbers.

The first tubes of this type were invented in the USA in 1955 by Haydu Brothers Laboratories and introduced for sale by Burroughs Corporation under the trade name NIXIE. The name was taken from the abbreviation NIX I, the extension of which would be "Numeric Indicator eXperimental No. 1 ". Tube’s lifespan is estimated at 5,000 hours for early-stage units up to 200,000 hours for tubes from the 1970s.

The successor of NIXIE were fluorescent and LED displays. The use of a LED matrix display in the I/50 as a NIXIE tube is therefore a retrofuturistic solution, a classic in the present day. As an interesting fact, let's say that the watch with tubes of this type was worn by STEVE WOZNIAK, co-founder of Apple.

THE MANUFACTURER ALSO MAKED SURE that the device was as functional as possible and thus encouraged younger fans of good sound. The I/50 features three line inputs as standard - a balanced and two unbalanced ones. Its functionality can be expanded by installing two optional modules: a phono stage and a digital-to-analog converter.

The phonostage supports a turntable with an MM cartridge, and it offers a gain of 42 dB. At some point any I/50 user can add a step up transformer and thus start using also MC cartridges. The DAC offers two digital inputs: RCA (S/PDIF) and USB, as well as Bluetooth module. At the time of the test, its parameters were not known yet. Both cards work are based on semiconductors. The phonostage module costs PLN 4,500, and the DAC will set you back PLN 9,000. In other words, they are not cheap.

The amplifier features and in-build headphone amplifier. Its output is located on the top panel, next to the volume knob. It seems to be a solid state amplifier with a tube input (6922 in the amp’s input stage). Plugging the jack in disconnects the speaker outputs. I do not know if it is important to you, but the device has a "standby" button. This is something not so common in tube amplifiers. The idea here was to make the operation of the device as similar as possible to that of a classic amplifier. Turning it off and on is therefore smooth and noiseless - you won’t hear anything coming from the speakers.

And there is also a remote control. It has a modern look, although it will be important for audiophiles that it is made of aluminum. The remote control features membrane buttons and is relatively small. It provides access to all the functions of the amplifier. In addition to the obvious, it's also supports dimming the LexieTube displays, selecting digital or Bluetooth inputs, and turning the amp off.

The I/50 is not the first so feature-rich tube amplifier. However, it is one of the first - maybe apart from McIntosh devices - that I know, that has it all mastered. Besides, it looks nice and is well-built. We know what we pay for.


⸤ HOW WE LISTETENED The Audio Research I/50 amplifier was tested in the "High Fidelity" reference system, in which it was compared to a system consisting of the Ayon Audio Spheris III tube preamplifier and the Soulution 710 transistor power amplifier. The device was placed on the top, carbon shelf of the Finite Elemente Pagode Edition Mk II, Heavy Duty version. The amplifier drove the Harbeth M40.1 speakers via Siltech Triple Crown cables or - alternately - by Western Electric WE16GA (NOS). I used the 4 Ω outputs to drive my speakers.

The signal source was the Ayon Audio CD-35 HF Edition SACD player, which was connected to the amplifier with an unbalanced Crystal Cable Absolute Dream interconnect. I usually use the Siltech Triple Crown interconnect, but the RCA sockets in the tested amplifier are not of the highest possible quality and spaces between them are quite small, so it was not possible to use Siltechs. The amplifier was powered by the Harmonix X-DC350M2R Improved-Version cable.

Recordings used for the test | a selection

⸜ JOHN COLTRANE, Blue Train, Blue Note/Esoteric ESSB-90123, SACD/CD (1957/2015) in: 6 Great Jazz, „MasterSound Works”, Blue Note/Esoteric ESSB-90122/7, 6 x SACD/CD.
⸜ BILL EVANS TRIO, Portrait in Jazz, Riverside/Fantasy RISA-1162-6, SACD/CD (1959/2003).
Cantate Domino, dyr. Torsten Nilsson, wyk. Oscar Motet Choir, Proprius/JVC Victor Company XRCD 7762, XRCD2 (1976/2003).
⸜ KING CRIMSON, In The Court of the King Crimson (An Observation by King Crimson). 50th Anniversary Box Set, Atlantic/WOWOW Entertainment [Japan] IEZP-128, „2019 Remix by Steven Wilson”, 3 x HQCD + BD Audio (1969/2019).
⸜ RED HOT CHILI PEPPERS, Californication, Warner Bros. Records 9362-47386-2, CD (1999).
⸜ SANTANA, Supernatural, Arista | BMG ‎07822 19080 2, CD (1999).


ALTHOUGH THE SOUND IN THE INDUSTRY I represent is the most important element, the sphere functionality and convenience of use, as well as the perception of the product is equally important. At least for me. Therefore, I need to start with a few words about I/50 as a luxury product. The device is very neat and pleasant to use. Everything works as intended, and the knobs on the top cover are well-balanced and have the right diameter.

Plugging the headphones into the proper input cuts the signal on the speaker outputs and does it so without making any sound. The remote control, although a membrane one, has a clear operating point for each button, so it can be operated reliably and quite comfortably. The only drawback seems to be the RCA inputs, which should be a of a bit better quality. And maybe the fixing of the tubes cover could be more sophisticated. Apart from that - it is a model example of how a tube amplifier should be built and how intuitive to use should it be in the 21st century.

This is in line with what you hear from the speakers. The I/50 designers clearly departed from the "brand’s" sound. And I would define the latter as a combination of sweetness and mass. For years, Audio Research has been offering a classically "tube" sound. With a slight tilt towards the "American sound". I reach for stereotypes, but I put them in quotation marks. And I reach for them, because in the case of this company, that truly contributed the development of the ‘tubes empire’, these are clearly positive terms.

Listening to the I/50, however, I could not help but feel that with this device, not the most expensive one, the American manufacturer was betting on a new opening. The sound of the amplifier is clean, fast and open. Similar terms will appear - below - in the section describing the sound from the headphone output. It's more of a distillation of what worked before, and it worked very well, opening up to people used to the modern sound.

With all the openness and vividness of the treble, at no time during my listening sessions I had the impression that the tonal balance was shifted upwards. Which is a paradox, because Audio Research does not deliver particularly low or dense bass. As I said - this is a different sound than the brand was known for in the past. Even JOHN COLTRANE from the Blue Train in the Esoteric remaster, released on the SACD, showed that it is a resolving, clear, open sound. In addition, playing with a well-arranged timbre and space.

It is an album with strong energy in the treble, yet the I/50 did not push it that way. Rather, it deepened the sound without warming it up. The fact that it goes towards opening the sound was confirmed by listening to the BILL EVANS TRIO’s Portrait in Jazz, in the version released in 2003 by Fantasy on the SACD. This release offers a completely different sound than the Coltrane’s, because it is less transparent, less resolving and rather muffled. The American amplifier slightly pushed it towards the opening, but it did not exceed the limits of good taste, or any limits at all. It stayed within the idiom that characterizes this album, but showed it from a fresher side, without muddying it up.

I have already mentioned dynamics shortly. Developing this thread it must be said that it is exceptionally good. The tested amplifier offers only 50 W output, but it delivers music with panache, bringing out the internal tensions between the sound sources. Moreover, it also draws a large image, extending it beyond the outer edges of the speakers. Thanks to the appropriate shaping of the timbre - I was talking about the fact that there is no bass "pumping" here - it was possible to use all its power to construct a huge space.

When a recording is an intimate one, like the Evans album, the sound is intimate too. Maybe a bit more blown up than with the reference system, but only by a little bit. But let's play something like Cantate Domino, an album released by the Swedish Proprius label, reissued in 2003 by JVC on the XRCD2 disc, and we'll be so impressed (cond. Torsten Nilsson, perf. Oscar Motet Choir). It’s a recording of organ and choir captured in a large church, so you'd expect a great space. And yet… The organ was of impressive size, and the choir stretched wide between the speakers.

The amplifier did not dilute the sound. Yes, it was still a clear presentation, but a presentation with good consistency. The space in question is constructed in a similar way to timbre. That is, there is no clear, focused image of individual sound sources. They are included in larger or smaller, but always recording dependent, acoustics. Tangibility can be described as decent. However, this is not the same type of sound as in older Audio Research amplifiers as in Leben or even PrimaLuna devices. Like I said, this is a new look at the company's heritage.

And now a curiosity - some heavily compressed recordings, from the RED HOT CHILI PEPPERS’ Californication and SANTANA’s Supernatural, both released in 1999, so in the middle of the "loudness war", massacred by compression, listened to with the I/50 sounded simply really cool. It was with them that the instruments had good focus, focus and better tangibility than with the previous albums. The stage had a depth of an ironing board, of course, but everything within it was arranged in a good way. Ultimately, the production of these albums, apart from the compression, is brilliant.

I also did not hear a brightened treble, which is common with solid-state amplifiers, even very expensive ones. But I had a really nice mid and upper bass. The emphasis was in the upper midrange that's clear. It was not, however, an unpleasant emphasis. It was arranged so that the music came first, and the problems with the sound, the problems of the disc, only second.

⸜ HEADPHONES The vast majority of headphone outputs in tube amplifiers take the signal from the tube output. In theory - it’s should offer excellent results, but in practice it is not always so. The thing is that it is not enough to put a resistor divider in the output to get good sound from both outputs. You still need proper knowledge and intuition. Both in I/50 worked perfectly.

Perhaps it was possible because the manufacturer chose a different path. Although the input section is based on tubes, on an input triode to be specific, the output section is - at least it seems to me, features transistors. It resulted in a really high quality sound. In a clean, open and fast sound. But also a very resolving one. Because, for example, the reverbs accompanying individual instruments on the Coltrane’s album were perfectly legible. Also the arrangement of the instruments in the space, taking into account the way I auditioned it, was really great.

More importantly, however, it seems to me that along with these advantages, the "connective tissue", which in music is responsible for density and fullness, is not lost. It is not as saturated sound as with the Leben CS-300X or CS-600X amplifiers, working as headphone amplifiers, but it is really very good. The treble are strong and sonorous, which gives an effect of an "illuminated" presentation. But never a bright one. On the other hand, the bass does not extend very low. But it is not a light or dry sound.

The designers managed to somehow balance it all so that we truly enjoy listening to the music and we do it with a smile on our face. So I don't see a need for an owner of the I/50 to buy an external headphone amplifier, even for headphones like HiFiMAN or Audeze.


I REALLY LIKED what I heard. The I/50’s sound combines an audiophile idiom with openness to the new. Its presentation was sonorous, extremely dynamic, but also well-ordered. There was none warmth of a stereotypical tube amplifier. It was rather the kind of warmth of a tube amplifier that connects the generations of music lovers. Because this warmth translates into coherency and speed, and not into coloration.

The amplifier can handle any kind of music and even the most compressed and devoid of dynamics recordings will sound great with it - as long as the music is fun. There is more to it. The tested device, with all its sympathy for worse sounding music, directs our attention towards the better recorded one, towards top performances and top recordings. Because it is so resolving that it shows such nuances at once.

Therefore, it is difficult for me to disagree with the manufacturer in his choices. The amplifier looks great, has a nice visual design that someone has worked hard on. It sounds great both through loudspeakers and headphones. It can be retrofitted with external modules. This is one of the most interesting amplifiers, both tube and solid-state, in this price range. So we are pleased to award him it with our ˻ RED FINGERPRINT ˺.


The AUDIO RESEARCH I/50 is a tube integrated amplifier with a semiconductor power supply. It was designed with younger users in mind - that is, less than 45-50 years old - hence, to some extent, the style differs from that in the company’s past. More importantly, however, the device is small and pretty.

⸜ CHASSIS Its housing is made of bent aluminum sheet reinforced with aluminum plates. The upper part, an anodized aluminum plate, can be chosen in one of several colors. Its central part is filled with black acrylic. The rest of the chassis is perforated, making it look "lighter" than it really is. And this is a classic tube amplifier, which means quite heavy. Most of the weight goes to the back, where, under an openwork grille, there are transformers - power supply and output ones. They are oriented towards each other so that they interfere as little as possible.

⸜ TUBES However, our attention will be drawn to the tubes and indicators located at the front. The former are simply LED matrices. They show the selected input and the volume level. The company named them LexieTube and reserved the name. Several small companies see Nixie tubes in this role - the similarity of names is not accidental - that look phenomenal. Audio Research, however, is a large manufacturer and cannot rely on older tubes, with a limited access to. LEDs seem to be a good compromise, the more so because their housing has been styled to resemble a glass tube’s bulb.

Behind them are actual tubes - three 6922 double triodes from the Russian company Electro-Harmonix and two pairs of 6550WE beam tetrodes from Sovtek, also from Russia. Manufacturers of tube devices are in a difficult position as most of the tubes were produced in Russia. So we can forgive MADE IN RUSSIA sign, but only temporarily. Ultimately, it MUST be a manufacturer from another country. The tetrodes are paired and work in an automatic bias circuit. This means that as the device ages, it will compensate itself for the changes in their parameters. The user does not have to do anything. These tubes work in AB class in push-pull mode.

⸜ TOP AND REAR There are also two large knobs on the top panel - the volume control, and input selector. Moving them from the front panel is an interesting choice. Thanks to it the amplifier looks really nice. Next to it, there is also a headphone socket for a large jack ø 6.3 mm, as well as a "standby" power switch.

On the back we find the other connectors. These are two pairs of RCA inputs and one XLR. There are plugs on the sides of the panel. This is where one can install optional modules - the MM phono preamplifier and the digital-to-analog converter. The RCA sockets are of average quality, they do not have a gold-plated positive pin, but the loudspeaker outputs look nice. XLR input is added for convenience. It is worth knowing that the signal is desymmetrized right after it and continues in an unbalanced circuit.

The amplifier rests on five large, rubber feet. We know them from earlier devices of this company. It is interesting, but in the manual, Audio Research strongly emphasizes the role of high-class connecting cables, while remaining with the simplest form of the feet.

⸜ INSIDE The electronic circuit is mounted on one large printed circuit board. The layout looks relatively simple. But the power supply is much more complex. It uses multi-leg voltage regulators and stabilizers with Zener diodes. Also, the microcomputer control circuit takes a lot of space. The circuit features Wima polypropylene capacitors, which couple the input triode with drivers, as well as Electrocube capacitors coupling the output tubes.

Although the I/50 is a tube amplifier, all the circuits except the main one, are solid state. The headphone amplifier is based on the LM833 integrated circuit in the input and a pair of transistors in the output. The transistors work in a push-pull mode. An interesting fact is that the board with a phono stage, which was included in the tested I/50, contains only input sockets. So maybe we do not pay for specific circuits, but only for unlocking them. A fan cooling the interior is mounted on the bottom panel. It will ensure lower temperatures, hence the components will age more slowly.

⸜ REMOTE The remote control is made of aluminum. However, it is different from probably all other remotes of this type I have seen. The thing is that the buttons are membrane ones and it looks as if an even thinner petal with buttons is embedded in a thin sheet of metal. Furthermore, the latch for the battery is nowhere to be seen. We the remote control one can control volume, select input, dim the LED displays, and operate the basic functions of a CD player.

Technical specifications (according to the manufacturer)

Output: 50 watts continuous from 20Hz to 20kHz. 1kHz total harmonic distortion typically 1% per channel, below 0.1% at 1 watt
Power Bandwidth: (-3dB points) 10Hz to 22kHz
Frequency Response: (-3dB points at 1 watt) 7Hz to 30kHz
Input Sensitivity: 1.25V RMS for rated output.
Input Impedance: 100K ohms Balanced, 48K ohms Single Ended
Inputs: 2 x RCA, 1 x XLR
• MM phonostage module, gain 42dB
• DAC module featuring USB, S/PDIF inputs
Input sensitivity: 1.25 V RMS for rated output 
Input impedance:
• 100 kΩ @ XLR (hot = 2, IEC-268) 
• 48 kΩ @ RCA
Output Taps: 8 ohms, 4 ohms
Maximum power consumption: 252 W @ nominal output 
Tubes: 2 pairs of 6550WE  [paired], 3 x 6922 [1 in input stage, 2 as drivers]
Dimensions: 420 x 180 x 340 mm (W x H x D)
Weight: 18.1 kg


Reference system 2022

1) Loudspeakers: HARBETH M40.1 |REVIEW|
2) Line preamplifier: AYON AUDIO Spheris III Linestage |REVIEW|
3) Super Audio CD Player: AYON AUDIO CD-35 HF Edition No. 01/50 |REVIEW|
4) Stands (loudspeakers): ACOUSTIC REVIVE (custom) |ABOUT|
5) Power amplifier: SOULUTION 710
6) Loudspeaker filter: SPEC REAL-SOUND PROCESSOR RSP-AZ9EX (prototype) |REVIEW|
7) Hi-Fi rack: FINITE ELEMENTE Pagode Edition |ABOUT|


Analog interconnect SACD Player - Line preamplifier: SILTECH Triple Crown (1 m) |ABOUT|
Analog interconnect Line preamplifier - Power amplifier: ACOUSTIC REVIVE RCA-1.0 Absolute-FM (1 m) |REVIEW|
Speaker cable: SILTECH Triple Crown (2.5 m) |ABOUT|

AC Power

Power cable | Mains Power Distribution Block - SACD Player: SILTECH Triple Crown
Power (2 m) |ARTICLE|
Power cable | Mains Power Distribution Block - Line preamplifier - ACOUSTIC REVIVE
Power Reference Triple-C (2 m) |REVIEW|
Power cable | Mains Power Distribution Block - Power amplifier - ACROLINK Mexcel 7N-PC9500 |ARTICLE|
Power cable | Power Receptacle - Mains Power Distribution Block: ACROLINK Mexcel 7N-PC9500 (2 m) |ARTICLE|
Power Receptacle: Acoustic Revive RTP-4eu ULTIMATE |REVIEW|
Anti-vibration platform under Acoustic Revive RTP-4eu ULTIMATE: Asura QUALITY RECOVERY SYSTEM Level 1 |REVIEW|
Power Supply Conditioner: Acoustic Revive RPC-1 |REVIEW|
Power Supply Conditioner: Acoustic Revive RAS-14 Triple-C |REVIEW|
Passive filter EMI/RFI: VERICTUM Block |REVIEW|


Speaker stands: ACOUSTIC REVIVE (custom)
Hi-Fi rack: FINITE ELEMENTE Pagode Edition |ABOUT|
Anti-vibration platforms: ACOUSTIC REVIVE RAF-48H |ARTICLE|

  • HARMONIX TU-666M "BeauTone" MILLION MAESTRO 20th Anniversary Edition |REVIEW|


Phono preamplifier: Phono cartridges: Tonearm (12"): Reed 3P |REVIEW|

Clamp: PATHE WINGS Titanium PW-Ti 770 | Limited Edition

Record mats:


Headphone amplifier: AYON AUDIO HA-3 |REVIEW|

Headphones: Headphone Cables: Forza AudioWorks NOIR HYBRID HPC