Puresound M845 Monoblock Amplifier

The M845 mono power amplifier is a single ended design based around the 845 power triode. Operating in Class A and giving 27 Watts of output power, it will complement a wide range of medium to high efficiency loudspeakers.

Implementing the 845 in a sympathetic circuit which takes full advantage of its capabilities is not straightforward. The filament draws a significant amount of power and also forms a part of the signal path so energising it correctly is a critical part of the design.

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The valve also operates with very high voltages across it so again, a careful choice of filtering components for that high voltage supply is essential such that adequate current is available to the valve at all audio frequencies instantaneously. In the M845 this supply includes a hybrid Graetz bridge for the initial rectification and a substantial smoothing choke as part of its CLC type filter.

The other difficulty in using the 845 is in the design of a stage capable of cleanly delivering the voltage swing necessary at its grid to take it to full output. The M845 incorporates a driver stage based on the 6SN7 triode coupled via a custom wound, wide band, inter-stage transformer. The amplifier’s input stage is directly coupled to this driver meaning that there are no coupling capacitors used in the circuit at all.

The end result is an amplifier capable of reproducing the full measure of instrument tone with extraordinary dynamic contrast, energy and colour. When partnered with appropriate loudspeakers the M845 will deliver an unparalleled reproduction of all types of music.

Puresound M845 Monoblock amplifier specifications

  • Freq Response…………………………………….-3 dB 7Hz-50KHz
  • Signal to noise:…………………………………>77dB (full output)
  • Input sensitivity:…………………………….460mV to full output
  • Input connections:…………………………1 Rca phono per amp
  • Output taps:…………………………………………………4 & 8 ohms
  • Valves compliment:…………………. 5Z3 x 1, 6SN7 x 1, 845 x 1
  • Output power:………………………………………………….27Wrms
  • Power consumption…………………………………………150Watts
  • Line in impedance:…………………………………………..1M Ohm
  • Dimensions…………………W260 mm x D470 mm x H240 mm
  • Weight……………………………………………………………22Kg each

Price £7499.95 (pair)

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