Line stage preamplifier
The Coral line stage preamp offers the best price/performance in the industry, while maintaining the accuracy and musicality you expect from a Wyetech Labs product.
The Coral uses a grounded grid configuration which we deem to be the best possible circuit topology for line level amplification This circuit maintains an exceptional bandwidth that extends beyond 250,000Hz
The buffered output is capable of driving two pairs of outputs to accommodate bi-wiring or bi-amping. All stages are DC coupled and only one Film Capacitor is used in the output stage for DC blocking. No feedback and mirror image circuitry is implemented in the audio section for best channel separation.
The 250 Volt DC power supply uses a Pye RC filter network, that eliminates all noise and ripple to below what our test instruments can detect. This was accomplished by the use of larger electrolytic reservoir capacitors than would normally be used. A 12 Volt DC power supply, that consist of a double Pye 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. An AC power line filter is also used to prevent unwanted noise and hash from entering into the unit.
The Coral's double sided printed circuit board (PCB) has been manufactured with the same high standards as that found in the Onyx amplifier. It has full solder masking on both sides of it's premium glass epoxy board with white silk screening that identifies parts and their placement for fast efficient hand soldering and assembling. These boards are held elevated from the surrounding metal chassis to avoid any capacitive coupling between components.
We import from Denmark our stepped ELMA volume controls that use 0.1% precision metal film surface mount resistors that is second best in life expectancy only to the Shallco military switches used in the Opal. It is the same quality volume and balance controls as that found in the Jade linestage.
The black knobs have a white dot indicator to match the precision markings on the face plate that allow easy visual settings for all functions. This is especially useful for resetting previous levels of desired loudness control on the volume attenuator.
We also use WECO screw terminal connections to fasten most wires to the PCB to facilitate easier replacement of parts for future reparability and long service life. All 18 RCA connectors are gold plated with Teflon insulating sleeves and are bolted to the chassis and not the PCB board to facilitate individual replacement if or when necessary.
A Toroid power transformer with dual primary windings, allow for 115/230 Volt universal usage that is switch selectable on the PCB board. The best quality NKK (Japan) toggle switches adorn the front panel using decorative knurled nuts differentiate the Coral as being a premium product. Large 8 mm LED's, the same as in found in all our other equipment, adds to that elegant rugged retro appearance.
Since perfection is our goal, we don't think parts should impart a signature sound but rather allow the sound to flow through unaltered. The type of parts used therefore must have a synergistic relationship to the circuit they are placed in. It is this relationship of which type of part to use where, that ranks our products apart from the crowd!
This line amp uses a grounded grid configuration which is isolated by a cathode follower stage before and after it. All three stages are non-inverting thereby maintaining absolute phase. The grounded grid configuration is known for its extremely wide bandwidth and high speed! The cathode follower output has a very low output impedance capable of driving two pairs of RCA output jacks to accommodate bi-wiring or bi-amping. All stages are DC coupled and only one capacitor is used in the output stage for DC blocking. No feedback is used and mirror image circuitry is implemented on the printed circuit board for the audio section. Overall amplifier gain is selectable via internal jumpers for 4.5db or 12.5 dB.
The power supply uses a Toroid power transformer for low noise and reduced magnetic field radiation to surrounding areas. A Pi RC filter is used for the 250 Volt plate supply and a dual Pi RC filter is used for the 12 Volt filament supply. These filters, like the OPAL & JADE, are designed using only passive components that allow the speed of the power supply to keep up with the analog circuitry.
- Machined aluminum plates (1/4” & 1/8” thick) bolted together with stainless steel machine screws is used to construct the preamp chassis. This provides excellent shielding from external radio frequency fields.
- Black molded knobs with white indentations allow for precise settings. These knobs have dual hex set screws to secure to shaft that insure accurate calibration and smooth operation of switches
- The stepped DACT dual Volume control has 24 gold plated contacts with surface mounted 0.1% precision resistors to maintain channel balance to within +/- 0.05db
- Selector switch engages relays located near RCA jacks to switch all inputs
- Balance control uses a sealed Electroswitch with silver plated contacts and 1% precision resistor networks
- NKK toggle switches for Tape monitor, Muting & Power on functions
- Noiseless TOROIDAL power transformer
- Non magnetic stainless steel and brass hardware is used throughout.
- Automotive high gloss paint finish.
- Polished Brass Handles accentuate the aesthetics of the front panel
The components are soldered by hand on a dual layer Printed Circuit board that is masked on both sides to protect & insulate the circuit paths as well as a silk screened layer on top to label the components and their position on the board. High quality Teflon coated Silver plated OFHC copper wiring is used in all analog wiring to and from the circuit board.
Automatic Power Sequencing and Muting
To allow for extended tube life a 30 second delay is applied before the high voltage plate supply is engaged. To allow circuit stabilization and quite operation a 60 second automatic muting is activated during power up. Muting is accomplished using a 2-pole relay that shorts the preamp outputs. When disengaged the muting circuit is not in the signal path.
- 2 x 5814A
- 1 x 5687WB NOS JAN military dual triodes
(reference to a sine wave at 3.5 Vrms output)
- +/- 0 dB FLAT - 20 Hz to 120 KHz
- + 0 dB/ -1 dB - 9 Hz to 425 KHz
- + 0 dB/ -3 dB - 4 Hz to 825 KHz
50 Kohms minimum
Channel Balance Control
11 position for +/- 5 dB adjustment in 1 dB steps
24 position stepped volume control (-60 dB to 0 dB)
3.5 Vrms (maximum = 7.5 Vrms)
High = 12.5 db. Low = 4.5 db (Internal Jumper)
2 pre-amp outputs, 1 tape output, 1 line level output
4 line level inputs, 1 tape input.
Switch selectable 115/230 Volt 50/60 Hz 35 Watts
12 lbs ( 5.5 kg)
16 lbs ( 7 kg)
15" W x 10.875" D x 3 3/4" H
July 2004 - Reviewed by Srajan Ebaen
…Even in its high-gain setting, the Coral via my 103dB Avantgardes was very quiet…
…Everything about Wyetech screams value and rock-solid engineering…
…surround the Coral with transistors fore and aft and you might be in heaven…
…There is no $2,000 preamp on the market I'm familiar with that comes even close to matching its mindboggling bandwidth…
Secrets of Home Theater and High Fidelity
February 2004 - Reviewed by Jason Victor Serinus
"It is liquid, smooth, and consistently musical."
The Inner Ear Report
Volume 15, #3 2003, pp. 17-20 - Reviewed by Ernie Fisher
Highs are sweet, transparent and unimpeded… midrange information is clear of sonic impurities and allows listeners to hear musical subtleties, delicate inner detail and resolution.
The Coral offers tight, fast and resolute bass… It's powerful, full-bodied…
…the price/performance ratio is exceptionally high…
Tubes - 1 year parts
Components - 5 years parts & labor