Many other 845 amplifiers use 4 stages, often using 300B valves as driver valves, but this more complicated design does not allow the 845 to reach its full potential in terms of transparency and maximum output of 110w, useful if your speakers need a lot of power. But the power is secondary to the large bandwidth and low distortion available.
For some people only a large triode valve like the 845 can give the golden warm tone which is so pleasing, with its feeling of air and space and sense of realism.
The MB845 MK I has truly become a legend in the UK, but hi fi fans were soon asking if there was more we could do to improve the performance. With the MB845 MK II, we have used all our expertise to create our ultimate triode PP amplifier. The MB845 MK II has an improved power supply, an upgraded driver stage, more linear driver chokes, and our new series of bigger LDT series of low distortion transformers. These have caused the MB845s to put on 11kg each to 37Kg each, so be careful lifting!
A feature of the MB845s is the high and low sensitivity. This enables MB845s to work with both “Passive” and conventional pre amplifiers. This is not done by attenuation which reduces quality, but genuinely changes the gain of the input.
The sound is best described at “an iron fist in a velvet glove”. These amplifiers will suit almost any speaker and situation. They have no particular down side other than size and weight.
The “ultimate” triode PP monoblock amplifier.
Specifications and Features
Improved LDT Tertiary winding output transformer
Improved dual 6SN7 high current driver circuit
Choke regulated power supply
All hand wired point to point
No printed circuit board to ‘colour’ sound
Class A, all Triode front end
2x 845B precisely matched for best performance
1x 6SL7 first stage gain valves
2x 6SN7 driver valves, choke loaded plates
845 AC heating for max life and max reliability
30.5V (typical) output at clipping point 8 Ohms*
Giving approx 20 Watts of Pure Class A
Can be used with passive or active pre-amp
450mv (high) & 1000mv (low) input sensitivity.
Signal to noise level -90db* (approx)
Hum and noise 0.5mv (low sensitivity)*
6SL7/6SN7 DC heater circuit for minimum hum
Freq response -1db points= 6Hz 27khz
Freq response -3db points= 6Hz-57kHz
Source impedance 0.7Ω (8Ω taps, low sensitivity)
Damping factor 13
Gain 67 (high) 30 (Low)
THD typically less than 0.1% @ 1w. 0.14% @ 8w (1kHz)
4 & 8 ohm loudspeaker taps
Custom tertiary hand-wound mains/output transformers
Attractive Plexiglass cover included in the price
Audiophile quality 2W precision resistors throughout
Solen audio capacitors (or optional Jensen Copper foil)
Silver PTFE audio cable
Gold plated Input & speaker terminals
220/240volts (115 v adjustable)
Comprehensive manual supplied
Full instructions for DIY valve change included
Power consumption: 180w min, (290w max sine wave) each
Size in cm W24, D57, H28 mm ( inc cover), 37kg each (Allow space for connections and ventilation)
Carton 2x 66x35x38cm + 1x 57x31x32 Total 84kg
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