"JADE" line stage preamplifier by WYETECH LABS

Jade front viewJade inner view

AUDIO CIRCUITS

After having been on the market less than a year the Opal preamp has been accepted as the leading edge in sound reproduction. We have developed the Jade to mimic it as close as possible, while making it more affordable to a wider audience. We've retained the grounded grid configuration which we deem to be the best possible circuit topology for line level amplification. Having only one buffered output allowed us to reduce the tube count to three double octal based triodes. This circuit, like the Opal, maintains an exceptional bandwidth that extends well beyond 250,000Hz. Our primary design philosophy that less is better than more has been fully developed in the Jade preamp.

POWER SUPPLY

The power supply is built on a separate terminal board, and is somewhat different from the Opal in that we have implemented passive shunt regulation of the 200 volt DC supply. It uses a double p (pi) RC type filter and a 30 watt Zener diode network to shunt the current while stabilizing the DC voltage level. We have again avoided using active feedback in order to maintain the speed of the power supply in relation to the extremely fast analog circuitry. Stability is ensured by the use of a large electrolytic reservoir capacitor and speed is enhanced by using a large (30µf) polypropylene film capacitor as a final filter stage located directly on the analog terminal circuit board. The Jade 200 volt DC power supply completely eliminates all noise and ripple to below what our test instruments can detect. An AC power line filter is also used to prevent unwanted noise and hash from entering into the unit.

PARTS

We use precision quality parts throughout. Our fixed terminal hand crafted circuit boards are identical to the ones used in constructing the Opal preamp and Topaz amplifier. The ease of replacing parts and the tenfold increase in lifetime durability are added benefits resulting from this board construction. 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.

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!

SPECIFICATIONS

TUBE COMPLEMENT:

(3)    3 - 6SN7GT VALVE ART Dual Triode

CIRCUIT DESCRIPTION

The JADE has been upgraded with the analog circuit and power supply taken from the Pearl. In addition a new selector circuit board mounts to the back of the input RCA connectors and now uses relay switching for all functions. Front panel selector and tape monitor switch, now control the relays, which handle the routing of the signal. Previous coax wiring running from the rear to the front selector & monitor switch has been eliminated, reducing the length of the signal path while eliminating much wiring and labor cost. This also enhances the life expectancy and reliability.

As a consequence the Pearl name has been discontinued and the new product will retain the name of the Jade. The new unit will sport the 24K gold plated knobs previously used on the Pearl. The JADE’s former black nickel knobs will still be available while supplies last at a no cost option

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! Each channel cathode follower is provided with two 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 using a separate circuit board for the audio section.

POWER SUPPLIES

A unique design for the power supply was implemented in order to eliminate all ripple & noise while maintaining a constant voltage regulation of the 200 Volt DC power line. A dual pye filter, consisting of  two large chokes, a  large electrolytic reservoir capacitor, several polypropylene capacitors and an array of high power zener diodes are used to provide exceptional power for the analog circuitry. This filter, like the OPAL, is designed using only passive components that allow  the speed of the power supply to keep up with the analog circuitry.  DC for the filaments is supplied using a solid state 3 terminal regulator for hum free operation.

MECHANICAL CONSTRUCTION

CIRCUIT BOARDS

[ Hand crafted PCB's using precision double turret terminal posts ]

Our fixed terminal hand crafted printed circuit boards are a new technology used in construction and is a first in the industry. Again Wyetech Labs is at the forefront and is always looking for ways to improve reliability and construction.

Most of the components are mounted on double turret terminal post. The octal tube sockets are also hard wired to these fixed terminals which in turn are soldered to the printed circuit board. This makes the tube sockets easily replaceable should the need ever arise. Chips and relays are mounted in sockets which are soldered to the board.

The double sided printed circuit board [ PCB ] has been manufactured with the same high standards as that found in the Sapphire amplifier. It has full solder masking on both sides of it's premium glass epoxy board with white silk screening that identifies parts and there placement for fast efficient hand soldering and assembly. These boards are held elevated from the surrounding metal chassis to avoid any capacitive coupling between components.

We also use WECO screw terminal connectors to fasten wires to the PC board to facilitate easier replacement of parts for future reparability and long service life. This technique will result in much faster trouble shooting and repair in the event of a failure and thereby reduce the labor and cost of any necessary repair.

High quality Teflon coated silver plated OFHC copper wiring is used where appropriate to make connections to and from each board and silver solder is used throughout.

AUTOMATIC POWER SEQUENCING & MUTING: 

To allow circuit stabilization and quite operation a 45 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.

SELECTABLE GAIN CONTROL

Overall amplifier gain is controled by a toggle switch for each channel. It can be swirched between HIGH [ 13db (4.4x ] and LOW [ 5.5db ( 1.85x ] gain..

To change the gain settings, you must remove the top cover [ see page 2 for proceedure ] the analog board on the left contains the left and right channel switches to select high or low gain..

FREQUENCY RESPONSE

[ reference to a sine wave at 3.5 Vrms output ]

1. +/- 0 dB FLAT; 15 Hz to 200 kHz
2. +0 dB/-1 dB; 7 Hz to 520 kHz
3. +0 dB/-3 dB; 3 Hz to 950 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 600 Ohms
RATED OUTPUT 3.5 Vrms [ maximum = 8.5 Vrms ]
SLEW RATE Greater than 25 Volts/microsecond.
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 18 LBS. ( 7.8 KG)
SHIPPING 23 LBS. ( 10 KG.)
DIMENSIONS 17” W x 14 1/4” D x 4 1/4” H
LIMITED WARRANTY TUBES:1 YEAR PARTS
COMPONENTS: 5 YEARS PARTS & LABOR