Jeff Rowland Corus preamplifier and 625 power amplifier review


Although in some circles there is a notion, that it does not matter how something looks as long as it sounds good, I came to a point in my audiophile searches, that I can confess to myself having a different opinion in that matter. Maybe this is the first sign of audiophile mannerism, or snobbery, but I would rather attribute that to genetically defined hedonism, which states, that a human, being a thinking being, and having some kind of taste, likes to surround him or herself with things, that are not only aesthetic, but also plain beautiful. This is the reason, that, putting sound aside, I value more the design of Dr. Feickert to Kuzma, or Accuphase to Hegel. It is just how I see it – and I do not intend to fight it, at least for now, as I am absolutely fine with this, and in addition, my wife sees my hobby with a much better eye.

This overly long, and seemingly not related to the current test introduction, should prepare you for what is coming next. I am talking about a manufacturer, who cannot be confused with anyone else. Ladies and Gentlemen – enter the beautiful separated amplifier from a company that makes products being a feast for the ears and eyes – Jeff Rowland: the preamplifier Corus, and the stereophonic power amplifier 625.

After unpacking both units can be placed in a prominent spot in our saloons, and we can just sit and enjoy their looks, uttering from time to time some sounds of appreciation. Although I was enchanted with the manufacturing quality and sublime design (each in its own style) when I was testing the Jubilee Accuphase and the Alluxity, but Jeff’s design is just stunning, overthrowing and make us re-evaluate everything that we have seen in our systems, and in a way, also heard in our systems. Please believe me, even if the tested set would not produce any sound, or would sound bad, I would still understand people buying it for its looks. Is this absurd? Not really – we just crossed the magic barrier of 100.000 zlotys, and behind it is hard to talk about reason when making a purchase, and the decision is usually based on emotion and design (spouses are usually also involved), and the Jeffs have a lot to offer in that aspect. The company special are the chassis cut from aluminium blocks, where the top, sides and back are black and the thick fronts glitter with a laser created wave patterns. A similar pattern can be found on the top covers, at least when we are talking about the offered DACs, preamplifiers and smaller integrates.

The Corus preamplifier is quite small, for a High-End device. In the middle of the front panel we have a big, readable, and dimmable, pearl coloured VFD display. Below the display we have a row of ten small buttons allowing us to chose the active input, select the recording input, enter the menu, dim the display or activate mute. To the right there is a nice knob for volume control, which allows for very comfortable, and much more precise than with the remote, volume setting in 0.5dB steps. Mentioning the remote, I have to say, that not everything is as easy as it may seem. The Corus can be controlled by a nice looking and solid, aluminium remote, but to do this, we need to connect a separate IR received to the unit, using a dedicated, and directional (!) cable.

The mentioned cable is plugged into a socket on the back plate on one side, and into a stylish, aluminium receiver, which is not the only accessory we need to connect first. The second one is the elegant and sturdy external power supply, which connects to the main unit with two cables, separately for the right and left channel.

The back of the Corus, reflects the symmetrical internal setup, looks like two mirror inverted parts glued together. The top row is taken by inputs, four XLRs and two RCAs, and in the lower row we have outputs. The two outputs are also balanced and un-balanced, there is also a recording-out in XLR and RCA version. So no cost-cutting here.

The 625 power amplifier looks much more richly, and at the same time very elegant. The front bears only a centrally placed, surrounded with a while ring, indicating the power state, power button. Also the remote controller (via 12V 3.5mm jack) can be used to toggle between power-on and standby. The “wavey” fronts are very attractive, but we need also to mention the heat sinks, cut with phenomenal precision, which are an integral part of the chassis, which are nicely looking, but also very helpful when we need to move the device. Their presence is not only aesthetic, but rather a result of the internal setup of the amplifier, which offers 300 W per channel at 8 and 550 W at 4 Ohm, using its 6 pairs of Darlington transistors and a pair of National Semiconductors LME49810 per channel. The bolted top cover is slightly embossed and has an engraved manufacturer logo.
The back of the unit, similar to the preamplifier, was designed with symmetry, and the mirror line is running in the middle of the unit, through the centrally placed remote and power sockets. The latter is a 20A version. It is worth mentioning, that while the happy owner gets two sets of loudspeaker terminals, in the form of the characteristic, bolted Cardas units, dedicated to spade connectors, to connect the speakers, the signal can be supplied to the amplifier by an XLR connection only.

So we are approaching the moment, when it would be advisable to concentrate on the sound of this visibly stunning combo. If you are bugged by the question, if it worth to spend over 100.000 PLNs to buy this amplifier, then the response would be… it depends on your personal taste. If you are searching for finesse, refinement and musicality then for sure yes, but if you like to split a hair in two and measure the freshness of the resin based on the sound of the violin – then… please listen first, before clicking the “buy now” button. And now completely seriously I would like to use the previous tests as reference. This American set sounds with a very dense, refined sound, which finds itself somewhere between the Alluxity and the jubilee Accuphase system in terms of aesthetics. But to come to this conclusion you need to allow the Jeff Rowland combo to play for about 45 minutes – 1 hour first. This time is required for it to catch temperature, form and breath. Well the set seems to sound OK immediately after power-on, but paying 100.000 PLNs we expect a little more than just ‘OK’, do we not? So when arranging a listening session in an audio shop, although tests at home should be the standard way of listening, we should clearly (and at best a few times) insist on warming the amplifier up before the session. This will allow us not to be bothered by traces of harshness and dullness, which can destroy the first impression of this amplifier. And you can make a first impression only once.

Assuming, that the above condition is met, we can sit down in a comfortable armchair and allow us to be carried by the music, as music is the most important thing for the Jeffs. A wealth of timbres, structure of the tissue between the precise, but not over-precise, contours and emotions, which make the difference between enjoying music and just listening to it. Do you think, that this is only a minor difference? Wrong! The so called background noise – the sound of traffic outside the window, the sounds made by neighbors – you can hear them, but (at least I hope so) you do not listen to them. The Jeff Rowland combo is above that noise, above everything that could disperse your attention; it concentrates, it calls for attention more than a beautiful girl on a promenade, or Maserati Quattroporte GTS cruising down a boulevard. If somebody is surprised, that I did not use a “more super” two-seater super car for comparison, I will now explain why. The Jeff Rowland breaks the stereotype of alienation, that is usually associated with the audiophile hobby – the loneliness of an old nutcase, pointed out by the rest of his family and remaining few friends, not sharing the same hobby. Instead it offers intuitive user-friendliness and a sound, you are willing to share with others. Not only it can seduce uninitiated people with its looks, but it can also show what High-End means, with ease, taste and nobleness. In appropriate conditions, adding the Corus and the 625 to the home stereo system may be the equivalent of buying the first TV set by our parents. Am I exaggerating? Well, everything depends on the sensitivity of the people that surround us, and our relationships with them.

Without the nonsensical dazzling with details extracted from the furthest parts of the sound stage, without any offensive, non-forgiving presentation of not only the soloists, but the whole symphonic orchestra, without the laboratory, antiseptic hyper-detail it can enchant the listener and make him or her not leave the listening chair for hours and hours. Regardless of the chosen repertoire, we could hear an incredible, almost tube-like, silky smoothness, which made listening to music nicer, better, while not veiling the resolution. It was like moving from the CD to LP while having a very good analog system.

Putting the technicalities aside, which claim, that the ‘digital’ is better, listening to the good old LP we are able to receive more information in a more natural, organic way, have stronger emotions and have a resolution of the sound close, and I underline this word, close to what we know from live music. Of course the differentiations of the medium listened to (LP, CD, files) were evident, as well as differentiation of different mastering within a given medium, but instead of a shock therapy, the American amplifier tried first to present the assets of a given recording, and only then discreetly hint to some eventual shortcomings. For example – on the monophonic “Jam Session” (RCA) with Benny Goodma, Gene Krupa and Artie Shaw, there is a incredible performance of “Ochi Chornya”, interpreted by Wingy Manone and His Orchestra, which kills completely, as modern teenagers would say. It does not matter, that the sound stage is between the speakers, that the noise of the disc is high and we have to get used to it, when the timbre, dynamics and naturalness, ease with which the music fills the room can only be described as phenomenal. Can this be done better? Of course, staying in the analog jazzy-swinging climates, you can just put on the platter of the turntable the disc “Satchmo plays King Oliver” – and we get shiny, and at the same time naturally coarse treble, incredible feeling and something often missing from the modern recordings – authenticity. It is similar with the first, monophonic version of “Paint it Black” The Rolling Stones, as when listening to it we have the idea, that almost half a century passed since it was recorded till today, but the music did not lose anything from its authenticity and topicality.

So is it the ideal? For some lovers of good sound for sure it is, but being absolutely frank, I cannot go around mentioning a few native characteristics of the tested combo. I am talking about the control and speed of the bass. It can be done in a more immediate way, keeping the lowest octaves in an iron grip and sadistically precisely control the movement of the bass membranes only in accordance to the source data. Similarly with the holographic transfer of the musicians into our listening room, or our transfer to a studio, concert room or stadium. Jeff Rowland offers an incredibly attractive, and almost palpable, illusion. With unusual grace it enchants and delights, but it knows, that we know, that it is an illusion. It is a clear gentlemen’s agreement, nobody forces no one to do anything against his or her will.

If somebody would like to verify with his or her own ears, how musicians can materialize at home, how we can have them for reach, then I warmly recommend listening to amplifiers like the Vitus SS-101 with the dedicated preamplifier SL-102, or the tube power amplifier Kondo Souga or even better the Kagura monoblocks.

There is also “a little” less painful way of upgrading, giving a foretaste of what can be expected a level or two higher – it is called Furutech Pure Power 6, and if somebody thinks, switching power supplies are not sensitive to the quality of power supplied, then such a person should visit an ENT specialist and have an audiometry performed. If the measurements are fine, then you have to listen to this power strip. With this seemingly soulless, milled piece of aluminum, the tested set got another dose of energy, and a breath, which was not expected before.

The almost two week long adventure with the Corus preamplifier and the stereo power amplifier 625 by Jeff Rowland allowed me to assess another idea for the sound, music and something called High-End. In case of this American manufacturer, the emotions were all positive, as the music amplified by those products only soothed souls.

Marcin Olszewski

Distributor: Chillout Studio
Corus – 54 900 PLN
Model 625 – 58 900 PLN

Technical Details:


Overall Gain: Independently Programmable 0 to 20 dB on each input
Gain Range: 99.5 dB, 199 Equal Increments
Gain Resolution: 0.5 dB, +/- 0.03 dB Over Entire Range
Frequency Response: 10 Hz – 300 kHz, -3 dB @ 8 Ω
Maximum Input Level: 13.5 volts (RMS) @ 0 dB Gain
Maximum Output Level: 13.5 volts (RMS)
THD + Noise: < .003% @ 2 volt (RMS) Output, 50 Hz – 20 kHz
Signal-to-Noise Ratio: > 100 dB
Common Mode Rejection Ratio: > 90 dB, 20 Hz – 20 kHz
Channel Separation: 99.5 dB
Input Impedance: 40k ohms Balanced or Unbalanced
Output Impedance: 60 ohms Balanced or Unbalanced
Inputs: 4 pair Balanced (XLR), 2 pair Unbalanced (RCA)
Outputs: 2 pair Balanced (XLR), 2 pair Unbalanced (RCA) for Main Out, 1 pair Balanced (XLR), 1 pair Unbalanced (RCA) for Record Out
Power Consumption: 15 W
Power Supply: Universal Voltage Input Power Factor Corrected Power Supply
Display: 320 x 32 dot Vacuum Fluorescent Display (VFD)
Preamplifier Weight: 22 lbs / 10 kg
Preamplifier Dimensions H/W/D: 3.9” x 15.5” x 12.3” (99mm x 394mm x 311mm)
Power Supply Dimensions H/W/D: 3.9” x 4.7” x 11” (99mm x 119mm x 279mm)

Model 625

Output Power: 300 W @ 8 Ω/ 550 W @ 4 Ω
Frequency Response: 5 Hz – 350 kHz
S/N Ratio: 95 dB, ref. 1.0 W @ 8 Ω load
Output Noise: <55 20="" hz="" i="" khz="" unweighted="" v="">
Crosstalk: >91 dB @ 1 kHz, 74 dB @ 20 kHz
Input Impedance: 10 kΩ
THD + Noise: 0.005% @ 1 kHz, 8 Ω
Damping Factor: >200, 20 Hz – 20 kHz
Overall Gain / Bal. or Unbal.: 27 dB
Common Mode Rejection Ratio: >90 dB, 20 Hz – 20 kHz
Absolute Phase Non-inverting: Pin 2 Positive
Inputs: 1 pair balanced (XLR)
Outputs: 2 pair parallel binding posts per channel
Power Consumption Idle: 100 W
Power Consumption Standby: 1 W
Amplifier Weight: 54 lbs. / 24.5 kg
Amplifier Shipping Weight: 64 lbs. / 29 kg
Amplifier Dimensions (h/w/d): 5.75” x 15.5” x 16.25” / 146mm x 394 mm x 413mm

System used in this test:
- CD/DAC: Ayon 1sc
- Digital source selector: Audio Authority 1177
- Network Music Player: Olive O2M; laptop Dell Inspiron 1764 + JRiver Media Center
- Turntable: Double synchronous motor Transrotor ZET 3 + 12"SME + Transrotor MC Merlo Reference + external power supply Transrotor Konstant M-1 Reference
- Phonostage: RCM Audio Sensor Prelude IC
- Integrated Amplifier: Electrocompaniet ECI 5; :Leben CS300F; Accuphase E-600
- Preamplifier: Jeff Rowland Corus
- Power Amplifier: Jeff Rowland 625
- Speakers: Gauder Akustik Arcona 80 + spike extenders; Trenner & Friedl ART
- IC RCA: Antipodes Audio Katipo
- IC XLR: LessLoss Anchorwave; Organic Audio
- Digital IC: Fadel art DigiLitz; Harmonic Technology Cyberlink Copper; Apogee Wyde Eye; Monster Cable Interlink LightSpeed 200
- USB Cable: Wireworld Starlight; Goldenote Firenze Silver
- Speaker Cables: Organic Audio; Signal Projects Hydra
- Power Cables: Furutech FP-3TS762 / FI-28R / FI-E38R; Organic Audio Power
- Power distribution board: GigaWatt PF-2 + Furutech FP-3TS762 / FI-28R / FI-E38R;Furutech Pure Power 6
- Table: Rogoz Audio 4SM3
- Ethernet cables: Neyton CAT7+
- Accessories: Sevenrods Dust-caps; Furutech CF-080 Damping Ring; HighEndNovum PMR Premium; Albat Revolution Loudspeaker Chips; Acoustic Revive RAF-48H

Opinion 2

America is a big, and wealthy country, so it is understandable, that so many High-End products come to life there. Only a small amount of those come to Europe, especially to Poland, and the reason for that are, for most part, the prizes, which are horrendous, at least from our point of view. Fortunately, there are some brands, which, despite the significant number of zeros in the price tag, manage to get over the ocean, and are offered by local distributors. For them, this is a challenge requiring lots of funding, but good press and positive opinions, allow to assume, that initial spending will be profitable on the long run. It will not be easy, because an audiophile, is the least loved (and most grumbling) client in an audio shop, unfortunately, he might be the only client, who can be interested by a brand name not present among the common brands in a supermarket. Anyway, as long as the products coming from the New World are as good, as may be assumed by their prices, the distributors can sleep well. Together with Marcin we were trying to lay our hands on some of that gear, and finally we managed to get for testing a separated amplifier from the cult brand Jeff Rowland: the line preamplifier Corus and the stereo power amplifier 625, distributed in Poland by the Krakow based Chillout Studio.

It is being said, that good audio gear does not need to look well, as long as it sounds well, but the influence of the external design on how a brand name is regarded in the audiophile world, is higher than one might expect. The manufacturers use different tricks, some are remembered better, some worse. The tested set has a design, that seems to surpass many of its competitors, as here we have a combination of modern simplicity with a nice sanding of the chassis, the visit card  of Jeff Rowland. The cabinets of both the products are black and silver pieces of sanding art, which glitter in light like neon lights, due to careful grinding of the aluminum. The waves on the front panel move, when we look at them from different angles. The effect is so nice, that I recommend to potential buyers, to test with your wives around you, because the looks of the units may become a more decisive element than the sound. This will not matter much, when the sound is to our liking, but if the amplifier would not catch any synergy with our system, then it may be worse. So be warned. The preamplifier looks as an almost solid piece of aluminum, with the front made from a three centimeter thick plate. This has a window in the middle, that houses a nicely readable dot matrix display, topping a row of ten buttons used to control the preamplifier. The volume knob is placed to the right. The size of the preamplifier is resembling a standard CD player. The back plate is covered by inputs and outputs in two formats – XLR and RCA, with two special sockets for connecting it to the external power supply. The latter is a narrow and long box, where in the front we have the sockets to connect to the preamplifier, and on the back an IEC power socket combined with a power switch. The power amplifier is bigger than the pre, about 1/3 higher and longer. The heat sinks are milled from one block of aluminum, what results in stunning visuals, but also allows to be very efficient in heat dissipation. After a few hours of playing, the power amp got only slightly warm. The front is similar to the preamplifier, with the difference, that instead of the display, we have here only one power button, with a white border. On the back panel there are four loudspeaker terminals (two per channel), made by Cardas, XLR inputs and a 20 ampere power socket. The necessary minimum. In addition to the set, we get also an external small box with a cable, which turned out to be a receiver for the remote controller, packed with the preamplifier. So this is a short description, of how the Jeff Rowland combo looks. How this matches the more important aspect of its presence, we will learn below.

When I received the set from Marcin, he informed me about giving it some time to warm-up in my system, as initially the sound is a bit dull. From experience I also know, that each change in the Reimyo system requires time to get acquainted with the new devices, so I did that, allowing them to play in the background during the time I wrote the introduction. When time came to start listening, the player was spinning a disc with ambient music Eivind Aarset, called “Dream Logic”. Electronic samples supported by guitars and drums strolled slowly along the virtual stage. Due to the different setup of the stage in such recordings I concentrated on things happening around timbre. I am writing “around timbre” on purpose, because computer generated sounds do not allow to fully assess it, every nuances need to be confirmed with material containing only natural instruments. But my attention was caught by slight direction of the sound toward the lower frequencies with a small correction of the treble. Please do not think, that the sound became muffled and muddy, absolutely not, this was rather that the edgy, electronic sounds became more civilized. Usually I am tired when listening to 3-4 pieces of that genre, and here the laser came to the end of the last track. The whole disc sounded with a fleshy and low reaching bass, saturated midrange and treble fitting to the whole picture. I heard such things many times, sometimes such tricks ended bad, sometimes well, so I did not experiment longer and took a disk much more demanding from the shelf. The material from “Skala” Mathias Eick responded to all my questions. The sound stage reflected very well the intentions of the sound engineers, every instrumentalist had its asylum in the virtual space. The depth of the stage was similar to my reference system, and did not allow the formations to come to close to each other. Even the realism of the virtual sound sources was on a similar level. The confrontation of the individual frequency ranges confirmed positive impressions I had. The weight put to the whole gave bass a bit more presence without any slowdown, the midrange was going in the same direction, while not losing any readability, and the treble, although less ethereal, still shone with microdynamics of the vibrating cymbals. As a whole we perceive this as thickening of the sound, but in the good meaning of the word, this can bring life back to systems without good timbre. I would like to remind here, that my loudspeakers have a tendency to color music a little, which influences also the perception of the American combo, yet the final effect was on a very high level. Where needed the amplifier smoothens a bit (electronics), while in other places it increases the palpability of music (acoustic jazz). Now being convinced, that the American engineers did their job well, I switched to the extremely expensive analog system I was testing in parallel. I am talking about the set from the company Thales, with the Simplicity tonearm, which showed where the unexplored by my turntable (Dr. Feickert Twin) areas of dynamics, musicality and resolution are hidden within the analog homogeneity. People, who did not experience this will just shake their heads, telling that they would never spend so much money on a turntable, but I say to all non-believers – never say never, listen for yourselves. If I would have enough balance on my bank account I would have purchased the tested set immediately. But this is not the tested device here, so I will return to the pre-power combination from Jeff Rowland. Knowing the abilities of the Jeff, I took the well known disc of the Antonio Forcione Quartet with his live recordings. On many presentations the first piece, opening the disc, is presented, “Heart Beat”, which is a certain trademark of this artist. The solo presentation of guitar virtuosity, interpreted by the musicians from the other side of the ocean, were the essence of a saturated, open and well sounding guitar. The quick riffs as well as melodic phrases were masterfully recorded and mixed and later mastered onto the vinyl disc. Starting with the artist, through the sound engineer, mastering and finally the playing stereo set everything fell in place creating a synergetic whole. So I used the character of the Jeff Rowland amplifier to stroll through my library, as an extra load on the bass and no garish on the treble allowed many of my discs come to full shine. I am happy, that my guests from America proved to have a well deserved place among Hi End, and were not just a marketing hype.

Trying to assess the tested separates, I would compare them with a chameleon. From outside it teases the potential clients with a memorable design, while during an intimate contact with music soothe the nerves of the listeners. The amplifier handled my, not so easy to handle, loudspeakers very well, showing that it knows its ways around. The observed sound aspects are a well balanced compromised between openness and weight. Too much of levity in any of the sound spectra, would destroy the detailed plan laid out by the engineers and would result in an unacceptable, teasing sound, what would kill the products. Looking back at the time spent with the Corus and the 625, I think it will be able to handle most of the loudspeakers available on the market, and the buying decision will be made only based on the expectations we have as to the final result. I really encourage you to try the tested amplifier, it may happen that it will match your taste fully, and the above average design you will get free of charge.

Jacek Pazio

The system used in the test, a complete set of Combak Corporation.

Electronics Reimyo:
- Separate DAC + CD player: CDT - 777 + DAP - 999 EX
- Tube preamp: CAT - 777 MK II
- Solid state power amp: KAP - 777
Speakers: Bravo Consequence +
Power cables: Harmonix X-DC-350M2R Improved Version
Speaker Cables: Harmonix HS 101-EXQ (mid-high section); Harmonix HS-101 SLC (bass section)
IC RCA Harmonix HS 101-GP
Digital IC: Harmonix HS 102
Table: Rogoz Audio
Accessories: Antivibration stand for the power amp by Harmonix TU-505EX MK2, Harmonix Enacom improved for AC 100-240V; Harmonix Tuning Room Mini Disk RFA-80i

Analog stage:
- Turntable:
drive: Dr. Feickert Analogue "Twin"
arm: SME V
cartridge: Dynavector XX-2 MK II
- Phonostage: RCM „THERIAA”

Original article: link

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