Product Review

Wyetech Labs Coral Stereo Tube Line Stage Preamplifier

February, 2004

Jason Victor Serinus



● Tube Compliment: Two 5814A, One 5687 WB NOS Jan Military Dual Triode
● MFR: [reference to a sine wave at 3.5 Vrms output]: 9 Hz to 425 KHz + 0 dB/ -1 dB
● Input Impedance: 50 kOhms
● Non-Inverting
● 24 position stepped volume control [-60 dB to 0 dB]
● Output Impedance: 150 Ohms
● Rated Output: 3.5 Vrms [maximum = 7.5 Vrms]
● Outputs: 2 Preamp Out, 1 Tape Out, 1 Line Level Out
● Inputs: 4 Line Level, 1 Tape
● Size: 3 3/4" H x 15" W x 10.875" D
● Shipping Weight: 16 lbs (7 kg)

●  MSRP: $2,300 USA

Wyetech Labs


Not long after I obtained my much-appreciated Jadis Defy 7 Mk. IV amp, the much-respected reviewer and critic Scot Markwell asked me if I wanted to hear a preamp that would mate perfectly with the Jadis. The Wyetech Labs Coral had come to him for review, and he wanted me to hear it before he shipped it back to the distributor.

Scot also knew that I was hunting for a new preamp. As you can see from my recent reviews in the Secrets archives, I have been on and remain on a preamp review kick, learning much in the process. Preamps from Bruce Moore, BAT, and Audio Note have been reviewed of late; the Manley, Reflection Audio, new Edge, PS Audio, Messenger, and others are expected for review in the next number of months. Auditioning and possibly reviewing the Coral, far more reasonably priced than most of the preamps in this list, seemed an ideal way to go.

I had already read much commentary about the top-of-the-line Wyetech Opal line preamplifier ($7,800). Many reviewers of repute consider it one of the finest under $10,000 preamps on the market. Since Scot and the author of the one review of the Coral I've found on the web both suggested that the Coral's sonic signature was remarkably close to the Opal's, I was eager to have a listen.

What Wyetech Has to Say

Since releasing their statement piece Opal line preamp four years ago, Wyetech's Roger Hebert has experimented with ways to retain the Opal's sought after sonic signature, while offering lower price alternatives. He first issued the Jade line preamplifier ($3,800) two years ago. The Coral line preamplifier ($2,300) followed in November 2002, with the Pearl line preamplifier ($5,300) making its début in the fall of 2003.

Roger has done a great job filling Wyetech's website with information rather than splash. The initial news release for the Coral states:

“The Coral uses the same precision stepped volume and balance controls found in the Jade, allowing precise settings and functions not seen before in a moderately priced preamplifier. Implementing three low noise military specification NOS dual triode vacuum tubes without the use of feedback, this preamplifier is compatible with both solid state and tube amplifiers. Calibrated switch settings allow precise control over all volume and balance settings. The inputs use relay switching located next to RCA jacks to keep the signal path as short as possible. Internal jumpers allow for high gain [12.5 db] or low gain [4.5 db] overall operation.”

Most importantly, Wyetech provides a complete line stage comparison chart:
Please examine this page, because it explains the difference in parts quality between Wyetech's four line preamps. (Wyetech calls them “line preamps,” but common parlance uses the term “linestage”).

As someone who has spent more hours than I wish to recall auditioning upgrades to the Bruce Moore Companion III preamp, I have become quite familiar with the difference a resistor, capacitor, or attenuator upgrade makes to performance. The better the equipment design to begin with, and the better the overall equipment/cable assemblage, the more one is able to hear the results of such upgrades.

Upgrades cost money. If a manufacturer upgrades 20 resistors from a brand that costs $0.20/each to another that costs $2/each, that upgrade alone adds at least $400 to the retail price. Throw in a more complex circuit, more NOS tubes, a change of wiring and cabinetry, etc., and you've got differences of many thousands of dollars. And of course, in the case of small operations such as Wyetech and Bruce Moore, you must figure in the costs of research, development, repair, and advertising if you are to stay afloat in the high-end game.

Design and manufacture of the Coral was only made possible after Wyetech obtained what they term a “lifetime supply of quality military new old stock [NOS] tubes.” This enabled them to implement “pure triode technology” for a reasonable price. Wyetech even lists the cost of tube replacement on their website, something you will rarely find in the high-end arena. Even rarer is the reality that the tubes are reasonably priced.

Here is some more of Wyetech's technical description of the Coral, with grammatical revision by yours truly:

“We've retained the grounded grid configuration which we deem to be the best possible circuit topology for line level amplification. This circuit, like the Opal and Jade, maintains an exceptional bandwidth that extends well beyond 250,000 Hz.

“The 250 Volt DC power supply uses a Pi RC filter network that eliminates all noise and ripple to below what our test instruments can detect. This was accomplished by utilizing larger electrolytic reservoir capacitors than would normally be employed. A 12 Volt DC power supply that consists of a double Pi RC filter is used to power the tube filaments, thus reducing hum levels even further.

“We have again avoided using active feedback [regulation] in order to maintain the speed of the power supply in relation to the extremely fast analog circuitry.

“We import from Denmark our stepped ELMA volume controls that use 0.1% precision metal film surface mount resistors that are second best in life expectancy only to the Shallco military switches used in the Opal. The Coral uses the same quality volume and balance controls as that found in the Jade linestage.

The preamp includes two coaxial outputs, which is great for systems with separate subwoofers, as well as the usual complement of coaxial inputs. I shall let you be the final judge in terms of design. A sophisticated appearance is not, IMHO, high on the list of Wyetech priorities. The sound, however, is another matter.

Setup and Listening

The Coral arrived already broken in. Auditioning the unit was a simple case of isolating it from vibration, attaching an excellent Elrod EPS-2 Signature power cord and Nordost Valhalla interconnects, warming it up for an hour (the same time I give my Jadis), playing Ayre break-in and demagnetizing tones, and taking a listen. All comparisons were performed with the same interconnects and speaker cables. Switching back and forth multiple times during listening evaluations assured me that one preamp was not at a disadvantage to the other because the cables had been recently shifted.

I did find the preamp's Mute switch useful. The Coral sometimes makes a little pop when turned on and off. The sound is soft and doesn't seem harmful to one's speakers. But it's nicer to turn a preamp on and off in silence.

I had hoped to compare the $2,300 Coral with another tubed preamp, the $4,000 Bruce Moore Companion III. Alas, the Moore was away for yet another upgrade, this time a change of diodes in the power supply. The only preamp on hand was my reference preamp of late, the $6000+ solid state Reflection Audio OM-1 Quantum with an optional battery pack (not used) that raises its price to close to $8,000. Clearly, putting one against the other is not a fair comparison. But with judicious listening, it does provide a means of reference.

My first impression of the Wyetech Coral remains my overriding impression. This is a beautiful sounding preamp. None of the criticism you read below should be seen as altering my basic take on the Coral preamp. It is liquid, smooth, and consistently musical.

My first selection was my old standby, Terry Evans' “Blues No More” from Puttin' It Down (JVC-XRCD; also available in SACD). Terry's voice was extremely clear. Nonetheless, his voice and the instruments surrounding it, including Ry Cooder's guitar, exhibited less fullness and body than I was accustomed to hearing. The cymbals sounded a little thinner than usual, and there was less overall color to the presentation. Edges around the electric guitar were not ideally sharp; there was a tube-like softness to them that is not a necessary component of tube gear. The bass, on the other hand, was quite good, the soundstage very large, open and satisfying, and the entire presentation very smooth. I didn't hear everything I was accustomed to hearing, but what I did hear was a delight.

Then came another old standby, Hilary Hahn's Brahms Violin Concerto (Sony). Having just heard Hilary Hahn live in recital last night from Orchestra Row L, I can attest that this DSD recording is far more truthful than earlier Sony PCM recordings of Ms. Hahn, regardless of 20- or 24-bit Super Bit Mapping. I also discovered that Hahn's violin sounds nowhere as sweet in person, at least not in Zellerbach Hall (which does have a high frequency roll-off), as it sounds on virtually every system I've played the disc on. (My system is far less sweet - that's far more neutral - than most encountered at CES and HE 2003). But as a recording, the Brahms is very, very good, and undoubtedly better in single-layer SACD.

Hahn's orchestral accompaniment sounded quite warm on the bottom; the opening of the concerto was beautiful. The strings were not as brilliant as I would like, sounding as though they were heard farther back in the hall rather than from the best seats in the orchestra. Nor was their attack on declamatory passages as strong as I was accustomed to hearing. I wanted more color around Hahn's violin and a blacker background. But again, the presentation was so smooth and beautiful that it won me over.

Next came the beginning of Reference Recordings' Rachmaninoff Symphonic Dances. The same positives apply. As for negatives, the drum thwaps were not as startling and clearly delineated as I would have liked, and the trumpets lacked the cutting edge one experiences live and on the best systems.

At CES 2004, I came by David Chesky's Entre Amigos/Among Friends, a new recording featuring bossa nova vocalist sensation Rosa Passos and bassist Ron Carter. Back-up, besides Carter's bass, includes Lula's guitar solos, Passos' guitar, Paulo Braga's percussion, and Billy Drewes' tenor sax and clarinet. I hope to review this recording in the next month or two.

What I missed here were the crispness and ultimate color I hear using the Reflection Audio preamp. I also heard less breath around Passos' voice than with the preamp that costs almost three times as much. But I could really sense the body of the guitar and its resonance. That is quite an impressive feat for a preamp that costs $2,300.

Finally, I returned to the disc I dragged from room to room at HE 2003, Karina Gauvin's Songs of the Auvergne with chamber orchestra accompaniment (CBC Records). The drum thwacks on Lou Coucut were not as full as I would have wished, and I did not hear the usual sharp edge on Gauvin's soprano. Highs were not as extended, and there was less color to the instruments than I would have liked. There was more gray and uniformity of color, and less brilliance on top than I'm used to hearing on disc and live.

Making Sense of it All

If you'd be good enough to open another window on your browser, please reference the comparison chart mentioned above:

Note the difference in parts quality in preamps when it comes to resistors, capacitors, switches, controls, and even the board construction and input wiring.

I have played with upgrades enough to know something about differences in parts quality. I don't know enough to be dangerous, but I do know enough to be able to state with certainty that when you upgrade resistors, capacitors, and attenuators, you get:

1. Far greater detail

2. Greater extension at high and low frequencies

3. Blacker background

4. Sharper images (not etched, but more clearly defined)

5. Sharper and clearer attacks

6. More color and three dimensionality because everything stands out more.

7. As an equal consequence of same, more three-dimensionality.

In short, what we are hearing with the Coral is an entry-level preamp whose design, when taken to its ultimate realization, could well deliver the exceptional sound attributed to the Opal. Despite its parts shortcomings, there is an overriding musicality and smoothness to this preamp that makes it most desirable.

I can also state with surety that few cables are as revealing as Nordost Valhalla. If there are differences between components, Nordost Valhalla makes them abundantly clear. The differences I hear between components will be far less apparent on the more modest systems in which the Coral will most likely find a place. I would especially think that the Coral would prove a great match for a solid state amp that lacks warmth and smoothness. Having heard several iterations of the much-vaunted Audible Illusions Modulus 3A, for example, I can tell you that as a linestage, the Coral preamp is far more musical and has far more user-friendly attenuator settings.


Wyetech has done a stunning job with this baby. For an entry-level linestage preamp, its musicality and smoothness override any shortcomings. Its deficiencies, which are frequently encountered in preamps in its price range, are sins of omission rather than of commission. In many systems, the Coral will prove most desirable. If it's in your price range, by all means take advantage of the 30-day trial period and give it a listen. Few if any preamps I've encountered for under $2,500 sound as smooth, musical, and rewarding.

- Jason Victor Serinus -

Associated Equipment:

Digital Front End
Sony 707ES transport modified by Alexander Peychev of APL Hi-Fi
Theta Gen Va single-ended DAC (to be replaced shortly by the Gen VIII)

Perpetual Technologies P-1A with Modwright modified Monolithic Power Supply and Revelation Audio umbilical power cable (not used for this review)

Jadis Defy 7 Mk IV modified with a Siltech silver harness

Bruce Moore Companion III tube preamp with Electro-Harmonix gold pin 6922s and Jan Philips 12AU7 equivalents;
Reflection Audio OM-1 Quantum battery-powered preamp in non-battery mode (used for this review)

Talon Khorus X speakers (with latest modifications and Bybee filters that render its response even across the spectrum and greatly improve the bass)

Nordost Valhalla interconnects and digital interconnects
Nordost Valhalla bi-wired speaker cable
Powercables: Elrod EPS-1, 2, and 3 and EPS-2 and -3 Signature on main chain plus Harmonic Tech, Nordost, and AudioPrism SuperNatural S2 elsewhere

PS Audio P600 Power Plant power synthesizer with MultiWave II
PS Audio Ultimate Outlet; PS Audio Power Ports
Michael Green Deluxe Ultrarack, Basic Racks, room treatment, and Audiopoints
Ganymede supports under amp and transport
Black Diamond Racing Cones
Shakti stones on Amp, Monolithic/P-1A and Theta
Bedini Quadra Beam Ultraclarifier
Audioprism Stoplight and latest, Marigo Stealth Mat for CDs
Sheffield/XLO degmagnetiser and break-in disc and Ayre demagnetizing disc

Analog (hardly the strong suit of the system, not used for review purposes)
Dual 1219
Sumiko Blue Point cartridge
Classe 6 phono preamp with optional umbilical cord
Interconnects: Tara Decade and Nirvana SL-1 to phono preamp


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