VTA20S 20 Watt Stereo Amplifier OWNERS MANUAL
This manual provides general, ongoing use and safety information for the VTA20S Stereo Amplifier also known at the Black Magic 20 Stereo Amplifier. GENERAL The Black Magic 20 stereo amplifier is the perfect blend of form and function and the ideal choice for serious music listeners. It is conservatively rated at 20 watts per channel in stereo mode and 40 watts in monoblock mode.
CIRCUIT DESCRIPTION The input stage of these amplifiers consists of a 12AX7 current sourced, long-tailed balanced pair direct coupled to the complimentary pair of EL84M tubes. An internal DC restorer ensures that the bias voltage remains correct over the entire audio signal cycle. Each set of output tubes are arranged in a push pull configuration. The EL84M screen grids are operated at approximately 340 volts, the output tube plate voltage is about 408 volts.
REAR PANEL CONNECTIONS POWER SWITCH Up is on, down is off. There is no power-on indicator except for the glow of the tubes; you will have to remember whether you turned it on until you can see the tubes glow. It is safe to switch the amplifier on and off at will. We recommend that you turn the amplifier off when not in use to extend the life of the tubes. LINE VOLTAGE This amplifier is configured for operation with 120V 50/60 Hz. FUSES The rear panel main fuse is a 2.
COOLING Convection cooling - Cool air is drawn from under the chassis by the heat from the tubes acting as an air pump, and exhausting the warm air out the chassis through the side vents. Do not place the amplifier on a carpet or in a closed cabinet. You must allow the feet to do their job by keeping the bottom raised, allowing unimpeded airflow. NEW AMPLIFIER SMELL We burn-in these amplifier in for 72 hours using a 1 KHZ sine wave driving 4 ohm loads.
Black Magic 20 Amplifier Specifications Number of Line Inputs Input Impedance Input Stage Automatic DC Restoration Nominal Voltage Gain Output Stage Configuration 1 100K Ohms 12AX7 current sourced low noise valve Yes 26dB (into 8 ohms) 1 Complementary set of EL84M’s per channel Regulated Screen Supply Voltage 340V Output Tube Plate Voltage 408V Output Tube Idle Power Bias Adjustment Rated Power Output Impedance Noise Hum Less than 9W each Automatic 20 watts per channel in stereo mode 40 watts in sing
IMPORTANT SAFETY INFORMATION Read Information — All the safety and operating information should be read before the amplifier is plugged in. Follow Information — All operating and use information should be followed. Retain Information — Retain the safety and operating information for future reference. Heed Warnings — All warnings on the amplifier & in the operating instructions should be heeded.
CAUTION: - Changes or modifications not expressly approved by BOB CARVER LLC will void the manufacturer’s warranty.
WARRANTIES: Bob Carver LLC warrants that all equipment manufactured by us to be free from defects in materials and workmanship for seven (7) years (vacuum tubes – one (1) year).
