"CORAL" line stage preamplifier

Coral front viewCoral rear view

AUDIO CIRCUITS

This is a world class linestage at a most affordable price. The Coral undeniably offers the best price/performance in the industry while maintaining the accuracy and musicality consistent with any Wyetech 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.

POWER SUPPLY

The 250 Volt DC power supply uses an 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 and large resistors

A 12 Volt DC power supply is used to power the tube filaments thus reducing hum levels even further. An AC power line filter is also used to prevent unwanted RF noise and hash from entering into the unit.

PARTS

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 resistor. It is the same quality volume controls as that found in the Ruby 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!

TECHNICAL SPECIFICATIONS

TUBE COMPLEMENT

[2] 5814A [1] - 5687WB NOS JAN militrary dual Triodes

CIRCUIT DESCRIPTION

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.

MECHANICAL CONSTRUCTION

CIRCUIT BOARDS

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 & 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.

FREQUENCY RESPONSE

[ reference to a sine wave at 3.5 Vrms output ]

1. +/- 0 dB FLAT … 20 Hz to 120 KHz
2. + 0 dB/ -1 dB … 9 Hz to 425 KHz
3. + 0 dB/ -3 dB … 4 Hz to 825 KHz

INPUT IMPEDANCE: 50K ohms minimum
ABSOLUTE PHASE: non-inverting
CHANNEL BALANCE CONTROL: 11 position for +/- 5 dB adjustment in 1 dB steps
ATTENUATION: 24 position stepped volume control [ -60 dB to 0 dB]
OUTPUT IMPEDANCE: 150 Ohms
RATED OUTPUT: 3.5 Vrms [ maximum = 7.5 Vrms ]
SELECTABLE GAIN: High = 12.5 db. Low = 4.5 db [ Internal Jumper ]
OUTPUTS: 2 pre-amp outputs, 1 tape output, 1 line level output
INPUTS: 4 line level inputs, 1 tape input.
POWER REQUIREMENTS: Switch selectable 115/230 Volt 50/60 Hz 35 Watts
NET WEIGHT: 12 lbs ( 5.5 kg)
SHIPPING: 16 lbs ( 7 kg)
DIMENSIONS: 15" W x 10.875" D x 3 3/4" H
LIMITED WARRANTY: TUBES - 1 YEAR PARTS
COMPONENTS - 5 YEARS PARTS & LABOR