Related Manuals for Bandwidth Audio 2845
Summary of Contents for Bandwidth Audio 2845
- Page 1 2845 Monaural Amplifier Owner’s Manual www.bandwidthaudio.com sales@bandwidthaudio.com...
- Page 2 THE AMPLIFIER CONTAINS VOLTAGES WHICH CAN CAUSE SERIOUS INJURY OR DEATH Do not operate with the covers removed. High voltage can be stored in the power supply even if it is unplugged and not in use. For service, contact Bandwidth Audio. HIGH VACUUM TUBE TEMPERATURES MAY RESULT IN BURNS 845 vacuum tubes are some of the hottest running tubes found in audio amplifiers.
- Page 3 REPLACEMENT GZ34 / 5AR4 RECTIFIER TUBES MUST BE EITHER PURCHASED FROM BANDWIDTH AUDIO OR TESTED BY BANDWIDTH AUDIO PRIOR TO INSTALLATION IN THE AMPLIFIER. Quality control issues with modern rectifiers and/or old used rectifiers have been known to cause rectifier tube arcing.
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Page 4: Table Of Contents
3.4.2 Not all 845 Tubes have the same plate dissipation ..........19 3.4.3 Bias Drift ........................20 3.4.4 Bias Ranges and Operating with Incorrect Bias ............20 3.5 Internal Fuses – For Qualified Service Technicians Only ............ 21 3.4 Typical Specifications ........................23 2845 Monaural Amplifier Rev 1.0... -
Page 5: Amplifier Setup
Likewise, always unplug the amplifier from the outlet before removing the speaker load. This amplifier comes equipped with 4Ω, 8Ω, and 16Ω output impedance binding posts for maximum flexibility. If you are unsure of your speaker’s impedance, contact the manufacturer. 2845 Monaural Amplifier Rev 1.0... -
Page 6: Powering On And Off
Heat is one of the biggest factors in the lifespan of electronic components. This is especially true of the expensive power supply capacitors. 2845 Monaural Amplifier Rev 1.0... -
Page 7: Input Setup
If the optional balanced input is not equipped, the XLR Jack, input selection switch, and line input transformer mounting locations will be blocked off with black decorative plugs. This allows the option to be installed in the future, if so desired. 2845 Monaural Amplifier Rev 1.0... -
Page 8: Controls And Layout
The backlight also illuminates when the amplifier is on. The VU meter is calibrated to indicate the amplifier’s maximum rated RMS output power (approximately 50 Watts) when it is indicating +0dB. 2845 Monaural Amplifier Rev 1.0... -
Page 9: Back Features
IEC Mains AC receptacle to connect removable power cord to the amplifier. Use only the mains voltage indicated on the serial number tag below the mains input. This will be listed as either 115/120VAC or 230/240VAC. 2845 Monaural Amplifier Rev 1.0... -
Page 10: Top Features
Offers true differential to SE conversion through a high-performance line input transformer for high Common Mode Rejection Ratio (CMRR) to remove noise picked up on long input cable runs. See Section 1.5 – Input Setup. Top Features 2845 Monaural Amplifier Rev 1.0... - Page 11 12. Bias Meters Switch: This switch enables or disables the bias current monitoring meters. With the switch off, the meters are bypassed and therefore removed from the signal path. 13. Input Select Switch: *If Equipped* This switch selects either the Single Ended RCA input source or the Balanced XLR input source. 2845 Monaural Amplifier Rev 1.0...
- Page 12 The increased linearity and reduction of distortion is not caused by the change in volume, but instead by sampling the output and correcting for error. Increasing the volume back after moving to “Closed Loop” mode will still realize all the benefits of a feedback topology. 2845 Monaural Amplifier Rev 1.0...
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Page 13: Technical Information
845 Tubes (V4 & V5) - These jumbo 4-pin tubes use a bayonet style ‘twist-to-lock’ socket. To install, align the pin in the tube base with the slot in the socket. The tube should easily “fall” into the socket. DO NOT PUSH. 2845 Monaural Amplifier Rev 1.0... -
Page 14: Replacing Tubes
• The tube rectifiers in the 2845 amplifier should be replaced every 3-4 years. This is especially required if the amplifier sees a high number of power cycles, or the amplifier has seen a lot of vibration from... - Page 15 This is critical in the 2845 Amplifier, especially when running in Open Loop Mode due to the lack of negative feedback.
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Page 16: Setting Hum Balance Pots
The 2845 Amplifier uses precision 10-turn potentiometers. These take very little force to turn, so use a light touch. If you feel the hum balance settings are out of whack, with the amplifier off, you can find the approximate starting point by first turning the pots in one direction until they stop. -
Page 17: Biasing
If the 845 tubes show any signs of glowing red (red plating) in a normally illuminated room, reduce the bias setting immediately. A very dull red glow in a fully dark room is acceptable. Note: Preamp tubes are automatically biased. No adjustment is needed. 2845 Monaural Amplifier Rev 1.0... -
Page 18: Checking The Bias
845 tube mismatch will limit how high you can set the overall bias. The tube with the higher bias current must not be set greater than the recommended limit. The 2845 Amplifier has dual ammeters so this tube mismatch can be readily observed. -
Page 19: Not All 845 Tubes Have The Same Plate Dissipation
57W and can only handle a power supply voltage of 1000V or less. These tubes are not suitable in the 2845 Amplifier, regardless of bias settings! DON’T RUN THEM! See Figure 4 for the bias setting (mA) vs 845 plate dissipation (W). -
Page 20: Bias Drift
100W rated tubes which have first been closely monitored and do not show signs of red plating at these power levels, however tube life is uncertain. Regardless of tube lifespan tradeoffs, 75mA is the maximum continuous bias the 2845 Amplifier can handle due to its power supply ratings. -
Page 21: Internal Fuses - For Qualified Service Technicians Only
RECEPTICAL ON THE BACK OF THE UNIT Since the 2845 requires such a massive power transformer with many different internal power supplies, a fault with any one of the power supply circuits may not necessarily blow the mains fuse fast enough to prevent damage. - Page 22 Internal Fuse Locations: DC Filament Fuse HVB+ LVB+ 2845 Monaural Amplifier Rev 1.0...
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Page 23: Typical Specifications
Negative Feedback (in Closed Loop mode only) 5.5 dB Input Impedance 100K ohms Speaker Taps 4, 8, & 16 ohms Power Tubes 2x 845 Preamp Tubes 1x 6SN7, 1x 6AH4, 1x EL34/6CA7 (triode connected) Rectifier Tube 3x GZ34/5AR4 2845 Monaural Amplifier Rev 1.0... - Page 24 Bias Current: V4______________ V5_____________ Date: __________________ Bias Current: V4______________ V5_____________ Date: __________________ Bias Current: V4______________ V5_____________ Date: __________________ Bias Current: V4______________ V5_____________ Notes: ___________________________________________________________________________________ ___________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 2845 Monaural Amplifier Rev 1.0...
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