Power Output: 13 Watts RMS per Channel
● MFR: 9 Hz to 22 kKz +0/-1 dB
Input Impedance: 60 kOhms
Gain: 29 dB
Dynamic Headroom: 2 dB [Music Peaks Up To
Power Supply Storage: 280 Joules
Universal Voltage Select: 115/230 Volts 50/60
Power Consumption 125 Watts Each
Dimensions: 8.5" H X 9.5" W x 16" d
Weight" 31 Pounds/ea
● MSRP: $4,500/pair USA
When I first contacted Roger Hebert of Wyetech about reviewing his preamps
(see reviews in our archives), he proposed that I also review his Onyx
monoblock power amplifiers.
Several members of the audiophile industry whom I trust subsequently told me
that the sound of Wyetech’s top-of-the-line Topaz amps is extraordinary.
Whether they were referring to the Topaz 221A stereo ($9,000 for 18 watts
RMS/channel), the 572B stereo ($9,250 for 23 watts RMS/channel), or the
special order Topaz 572M monoblocks ($18,500 for 45 watts RMS/channel), I am
not certain. All I know is that their praise whet my appetite for the time
when I could put the 13W Onyx babies into action.
Reviewing the Onyx monoblocks constitutes my first opportunity to mate the
Khorus Talon X Mk. II (efficiency between 90.5 dB and 91 dB) with
low-powered single-ended triode amplification.
The following information is adapted from the Onyx Owner’s Manual.
Each Onyx monoblock uses a single Dual Triode 9-PIN base 5814A [JAN Military
NOS] tube in the input/driver stage, and two Dual Triode OCTAL base 6080WC
[JAN Military NOS] tubes in the output stage. 6AS7GAs can be used as a
substitute. The tubes come carefully packed in separate cardboard boxes
secured within the shipping boxes. Wyetech stocks a full supply of
replacement tubes, with prices listed on its website.
All stages of the Onyx operate in pure Class "A1" single-ended and contain
automatic self-biasing circuitry. The design employs large value Solen
polypropylene coupling capacitors, plus a custom built HAMMOND output
transformer for extended low frequency response.
Each of the output triodes is individually self-biased, with only the
plates tied together in a quasi-parallel configuration. The 11 pound output
transformer provides 13 watts RMS per monoblock with the claim of “absolute
stability into all low impedance loads.” Output windings are toggled via two
high current switches to allow selection of impedance for 2, 4, 8, or 12
Ohms. No feedback of any kind is employed in the design.
An internal toggle switch allows selection of toroidal power transformer
voltage input for 115V/230V 50-60 Hz operation. Three output windings
provide full-wave rectification using spike and noise suppression circuitry.
Separate DC power supplies are used to provide total isolation between the
input and output stages. These consist of a triple pi filter for the 300
volt output rail and a double pi filter for the 450 volt input and driver
rail. Rectified and filtered DC provides the power for the input tube
filament of the 1st and 2nd stages. The other two output tube filaments are
provided with AC connected in a balanced configuration to eliminate
Components are mounted on a PCB, designed manually
in house, which is made from FR4 glass epoxy with double sided copper traces
and plated through holes. Both sides of the board have a protective green
solder mask. A silkscreen is printed in white showing the component layout
and parts value.
The board features enlarged power and signal line traces which are said to
attain a level of analog integrity that automatic routing circuit programs
cannot attain. Wiring to the PCB is attached via screw-down crimp terminals
to allow for ease of repair should the need ever occur where the board would
need to be removed.
The signal path length on the PCB board is reduced to less than 6". Final
assembly of parts to the PCB is done by hand-soldering of all components,
which is claimed to allow more solder on joints than automated
The Onyx features a time-delay power-on relay that provides extended tube
life and proper power sequencing for stabilized circuitry. The filament
voltage is turned on for 45 seconds before applying the DC voltage. A
toggle switch enables power to the automatic sequencing circuit that delays
operation until the green [ready] LED comes on after the initial 45-second
delay. Because the design does not require warm-up, these amps are ready to
go within a minute of turning them on.
I positioned the monoblocks on maple cutting boards, isolating them from
vibration using Ganymede ball-bearing supports. All cable connections were
treated with Caig Pro Gold.
It may sound like damning with faint praise – certainly not my intent – but
I especially enjoyed the Onyx for background listening. While highs and bass
were certainly present, and the monotone coloration I once suffered
through while auditioning $18,000 Audio Note single-ended triodes was
thankfully nowhere in evidence, on my speakers, the Onyx lacked both
the treble brilliance and bass slam of more powerful amplification. In their
place, however, I discovered a feathery grace of a lower midrange and a
level of midrange fullness that, while impossible to confuse with a rich
sound, was quite musically satisfying.
I never attempted to play music as full blooded as Rachmaninoff’s Symphonic
Dances or the Berlioz Requiem. When I did try to listen to Terry Evans sing
the blues, the tight slam of percussion was not to be heard. Even on the Chesky disc of Rosa Passos and Ron Carter, the bass, while assuredly
present, lacked ultimate body. How much of what I missed was due to low
wattage, and how much to the fact that I don’t have extraordinarily
efficient speakers, I cannot say.
What I can say is that I very much enjoyed the warmth and heart of Passos’
sensual voice. Whether I was listening to string quartets or piano sonatas,
there was a specialness to the midrange too rarely experienced from high-end
amplifiers. I wouldn’t term the sound I heard “real,” but I very much
enjoyed it. Auditioning a number of the holiday recordings reviewed this
month was an especial treat.
Single-ended triodes have their own unique magic. With the Onyx, Roger
Hebert has managed to circumvent some of the most common faults encountered
in such amplification: truncation of highs and lows, with extremes replaced
by a monochromatic midrange. There is an uncommon feathery delicacy to the
Onyx’s midrange and upper bass that makes for a special listening
experience. Mated with speakers of sufficient efficiency, the Onyx
monoblocks are sure to win new converts to the world of single-ended triode
Editor's Note: For the Onyx, speakers with a sensitivity of 96 dB/w/m or higher
are really necessary for optimum performance. When so properly mated,
single-ended Class A triodes can produce a sound that is simply delightful, and
like no other you might have ever heard.
- Jason Victor Serinus -
Digital Front End
Sony 707ES transport modified by Alexander Peychev of APL Hi-Fi
Theta Gen VIII DAC/Preamp
Theta Carmen II transport (on loan)
Jadis Defy 7 Mk. II about to be upgraded to the current model
Talon Khorus X speakers MK. II (with latest modifications and Bybee
filters on woofers and tweeters)
Nordost Valhalla single-ended and balanced interconnects and balanced
Nordost Valhalla bi-wired speaker cable
Nordost Silver Shadow digital interconnect for DVD-V
Nordost Valhalla Power Cables
Also on hand and sometimes used:
Interconnects: WireWorld Gold Eclipse 5 and Gold Starlight 5 digital,
Harmonic Tech Magic One, Acoustic Zen Silver Reference II balanced, and
Nirvana BNC-terminated digital.
Power cables: Elrod EPS Signature 2 and 3 plus EPS 1, 2, and 3; WireWorld
Silver Electra 5, PS Audio X-treme Statement, Harmonic Tech, and
AudioPrism SuperNatural S2.
PS Audio P600 Power Plant power synthesizer with MultiWave II
PS Audio Ultimate Outlet; PS Audio Power Ports
Michael Green Deluxe Ultrarack, Basic Racks and Corner Tunes
Ganymede supports in main digital chain and under speakers
Michael Green Audiopoints, and Black Diamond Racing Cones elsewhere
Shakti stones on amp, Theta, and transport
Stillpoints ERS EMI/RFI sheets on most components
Bedini Dual Beam Ultraclarifier
Audioprism CD Stoplight
Marigo Signature Mat for use atop CDs
Ayre demagnetizing CD and the original Sheffield/XLO demagnetizing and
Terms and Conditions of Use