Ruby XR 300B

Voltage Stage

This stage operates in pure class "A1" single ended plate loaded with independent automatic biasing circuitry for each triode . Both triodes are wired in quasi parallel to take advantage of the 3 dB noise reduction using this configuration.

Driver Stage

This stage also operates in pure class "A1" single ended plate loaded with automatic self-biasing circuitry. This stage operates with high bias current and high voltages needed to drive the four 300B output tubes and do so without driving the 300B grids positive to insure no grid current drive is required. The AC signal is coupled to the 300B grids via 4 independent metalized high voltage, high capacitance Teflon signal capacitors with self healing ability and 1300 Volt DC rating.

300B Output Stage

All 4 output tubes also operate in pure class "A1" single ended self-biased isolated circuitry and transformer coupled output.

The 300B gain stage circuitry is exclusive, ground-breaking and unique, being only one of its kind ever to be implemented in a tube output stage.

Simply stated it is a serial - parallel single ended configuration that results in increasing the 300B stage gain by a factor of four, unprecedented and unique.

Two legs of two series connected 300B's are used in parallel by tying the top plates of each leg to drive the primary of the output transformer. The two bottom tubes of each leg is referenced to ground while the top tubes have floating biasing and signal drive.

If either leg of the series connected 300B tubes go out of range the red LED fault light will come on suggesting that these 2 tubes should be replaced. The left two tubes fault light is designated FL and the right series connected tubes is designated FR.

If the FL or RL red LED's come on then it's time to change that pair of 300B tubes.

Other Features

Dual triple digit LED bias meters read up to 99.9 Volts using a blue readout for constant monitoring.

A LCD hour meter (99,999.9 hours) is now incorporated to keep track of usage, especially important with monitoring the life of output tubes.

The 300B filaments, which also act as the cathode for each triode, require isolated pure 5 volt DC power supplies. Each of the four supplies have a separate 7 volt AC secondary winding connected to a full wave bridge rectifier followed by a 10,000uf filter capacitor and terminated using a solid state 5 volt regulator chip.

The output transformer reacts to this configuration in such a way that it thinks it has only one tube with four times the power rating of one 300B driving it. In other words this stage uses the same ratio of primary to secondary in the output transformer as would be used in an amplifier with only one 300B output tube.

Impedance settings of either 4, 8 or 16 ohms is selectable via two toggle switches located on top rear of each chassis.

Ground loop hum is not a problem - there is no ground lift switch on any Wyetech Labs amplifiers. We employ a special network that does not remove ground safety from the chassis. As a consequence Wyetech monoblock amps don't suffer from ground loop hum pickup!

Power Supplies

Three Toroid power transformers are used in each monoblock with input AC power operation for 115V-120/230-240V 50-60 Hz selected via an internal toggle switch.

Separate DC power supply filtering provide total isolation between the INPUT and OUTPUT stages. This consist of a quadruple-4 (pi) filter for the 500 Volt front end supply and a quintuple-5 (pi) filter for the 1 Kilovolt output stage power supply.

Twin bridge rectifiers rated at 12,000 Volts DC provide the needed voltage and current, that in turn feed the 6D22S (6Kv rating) rectifier tubes that enable the voltage to slowly ramp up due to the 30 second delayed warm up time of the 6D22S.

Custom made polypropylene in oil capacitors with special screw connectors allow easy assembly or removal from Printed Circuit Board

The use of pure LC filter networks with 10 very large polypropylene in oil capacitors, 3 large polypropylene capacitors and six large chokes provide an unparalleled ripple reduction and purity of design unequalled in tube SET amplifiers.

Rectified, filtered and regulated 12 Volt DC provides the power for the input tube filaments of the 1st and 2nd stage. This also contributes to lowering the noise floor.

An Analyst Plus AC Power Oval power cord is supplied with each Ruby monoblock amp.

Mechanical Construction

Extremely rugged all welded steel chassis with 4 mm aluminum top and bottom plates provide a solid firm structure by design. Think of a picture frame doubled up and back to back with the flat top and bottom pieces flush mounted and bolted with 28 stainless steel dress machine screws. This reduces any possibility of vibration induced aberrations affecting the operation of the amplifier tubes.

Top panels are CNC machined to a tolerance of 0.01mm (0.0004 in.).  All components and parts are secured to the top panel via CNC threaded holes

Highly polished 6 inch solid brass handles allow for easy handling and accentuate the chassis styling.

Very high quality powder coated chassis frame with baked on finish to further enhance the beauty of the very symmetrical arrangement of parts.

Satin black finish of the output transformer and dual power transformers mounted on top

Gold plated machined brass footers with 3M rubber feet inserts

Teflon tube sockets with machined brass gold plated tube pins for 5687, 12B4A and 300B tubes for an absolute secure connection and lifetime reliability

Ceramic tube sockets for the high voltage 6D22S rectifier tubes.

Power ON Hour Meter - count to 99,999.9 hours

Dual bias voltage Meters with blue LED readout - 0 - 99.9 Volts DC

Circuit Boards

The components are mounted on three Printed Circuit boards [PCB] which is made from FR4 glass epoxy with double sided copper traces and plated through holes. Both sides have a protective green solder mask. A silk screen is printed in white showing the component layout and parts value. All our PCB's are designed manually with CAD program in house. We use enlarged power and signal line traces to attain the best analog integrity that automatic CAD routing circuit programs cannot attain.

The final assembly of parts to the PCB is done by hand soldering of all components which is superior to automated flow-soldering techniques, by allowing more solder on each and every joint. 4% silver solder is used on all solder joints.

Wiring to the PCB is attached via screw down crimp terminals to allow for ease of repair or removal.

Auto Power Sequencing

A built in time-delay of about 30 seconds in the 6D22S rectifier tubes allows for a slow smooth ramp up in final DC voltages to maximize tube life

In addition a speaker muting circuit is engaged for 35 seconds on power up and 2 seconds before power down for dead silent operation.

Power Switches

Two toggle switches are employed for powering up the unit. The master switch enables the power and the momentary RESET switch engages the power relay to enable the automatic sequencing of operation until the green [ready] LED comes on after the initial time delay. In case of AC electrical power failure during a storm or other event the unit stays powered down until the RESET switch is again enabled. To use the RESET power switch it is important to hold down the spring loaded toggle for 3 seconds when powering up. Once you see the blue LED's light up - you can release the switch

We employ a delayed DC power sequencing that maximizes tube life by preventing cathode emission deterioration.

Power Down Sequence

The master switch is used to power down the unit. On activation of this switch a 2 second time delay occurs that mutes the speaker output before dropping power thus ensuring silence on powering down.

Impedance Matching

Triple impedance outputs for selecting which one of the three [ 4, 8, or 16 ] impedance's you require by the use of 2 toggle switches. Match the numbers to select. When the one switch is set to the 16 ohm position, it overrides the other switch for 4 & 8 ohm selection.