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OWNER' S MANUAL
THE DAVID BERNING COMPANY
211/845
POWER AMPLIFIER
The David Berning Company
12430 McCrossin Lane
Potomac, Maryland 20854
USA
(301) 926-3371
www.davidberning.com
WARNING: For safety, the cover of this amplifier should be secured at all times. DC
voltages as high as 1700 V and peak ac voltages as high as 3000 V are present inside.
The service information in this manual is intended for trained service personnel.
Furthermore, this amplifier generates radio-frequency energy that can interfere with
communications equipment if the cover screws are not tightly secured.
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Summary of Contents for David Berning 211/845
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Page 1: Power Amplifier
OWNER' S MANUAL THE DAVID BERNING COMPANY 211/845 POWER AMPLIFIER The David Berning Company 12430 McCrossin Lane Potomac, Maryland 20854 (301) 926-3371 www.davidberning.com WARNING: For safety, the cover of this amplifier should be secured at all times. DC voltages as high as 1700 V and peak ac voltages as high as 3000 V are present inside. - Page 2 The 211/845 amplifier is unusual in that it can be operated with either choice of these tubes. The two tubes are not equivalent and will result in somewhat different amplifier characteristics.
- Page 3 the pin moves into the guide slot as it is rotated. Do not force it as it should turn moderately easily once it is in the guide slot. Rotation of the tube depresses the four stiff contact springs in the socket. To repack for shipping, reverse the process. Components are included in the amplifier packaging for a safety cage to protect the user against the hot output tubes, and to protect the tubes from being struck and broken.
- Page 4 Fig. 1. Sketch of assembly of safety cage. Tube Rolling and Cover Removal The 211/845 has its power supply and impedance converter in a shielded enclosure within the main chassis of the amplifier. This enclosure offers partial protection from high voltage, as the tubes and the AC line switch are not within this enclosure. 1700 volts dc and peak ac voltages as high as 3000 volts are present at the base of the output tubes.
- Page 5 There are two choices in the driver tubes for the 211/845 amplifier. The 6K6 is a true power pentode, and the alternative tube choice is the 6V6 which is beam-power tube.
- Page 6 Your 211/845 amplifier can handle difficult load impedances. Momentary shorts or opens at the output of the 211/845 will not damage the amplifier; however, a sustained short circuit at the output may cause overheating, and may cause the amplifier to shut down.
- Page 7 Also, the output impedance is different for the different modes and this generally does affect the sound. The 211/845 follows other Berning designs in that the tubes are operated at relatively low temperatures for long life. The exception is the operation of the output tubes if the FULL CLASS A mode is used.
- Page 8 Active line power factor correction (PFC) is used in the 211/845. This extra full power- processing stage in the power supply allows the amplifier to meet worldwide line harmonics emissions standards.
- Page 9 Non-magnetic chassis prevents skin-effect induced distortion. Power supply in separate internal shielded enclosure. Specifications Power consumption: 150 W to 500 W Line voltage required: 90-240 VAC, 50-400 Hz. Signal to noise: broadband (typical) 50 dB, all Class settings. 20 kHz bandwidth (typical): 86 dB 845 FULL;...
- Page 10 211/845 amplifier or a battery. The high sides of these supplies are bootstrapped back to feed power to the 6SN7. Also feeding power to the 6SN7 plates is a servo- controlled voltage source that is controlled by measuring the combined cathode current of the output tubes.
- Page 11 Like other tube amps, a momentarily shorted output will not hurt the 211/845, and a momentary short will not activate the protection circuits. Note that this imposed limit does not introduce distortion or phase shift at 20 Hz.
- Page 12 The high frequency prevents audible hum that would be present if heated with line-frequency ac. The Zero-Hysteresis (ZH) 270--A New Kind of Amplifier, Now the 211/845 The design of the Berning ZH270 power amplifier and its release in 1996 represented a radical departure from that of other amplifiers.
- Page 13 neither one is anywhere near the actual speaker impedance. In the Futterman style amplifier, a large amount of negative feedback is required to force the push and the pull to work together properly, and to provide sufficient damping for the speaker. Some of the alternative OTLs that use the low-impedance triodes can operate without requiring feedback because the gain of these triodes is so low that there is little difference between the plate impedance and the cathode impedance, so the mismatch between the push and...
- Page 14 with age, the current capability is reduced, but the voltage capability is not affected. Longer useful tube life is expected because less current is required for a given output power. The opposite situation applies to the traditional OTL amplifier. Audio-output transformer-coupled amplifiers should not be operated without a load connected because the inductance of the transformer’s primary can cause the plate voltage to reach a sufficiently high voltage to break down insulating materials, resulting in amplifier failure and even fire.
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