M845

About the M845

The PureSound M845 monoblock amplifier is a single-ended Class A design centered around the 845 power triode valve, originally developed by RCA in 1931. It delivers 27 Watts RMS output power, suitable for medium to high efficiency loudspeakers. The amplifier features a carefully designed high-voltage power supply with a hybrid Graetz bridge rectifier and a substantial smoothing choke in a CLC filter configuration to ensure instantaneous current delivery across audio frequencies. The driver stage uses a 6SN7 triode coupled via a custom wound, wideband interstage transformer, with the input stage directly coupled to the driver, eliminating coupling capacitors and negative feedback. This design approach yields extraordinary dynamic contrast, energy, and tonal color, reproducing instrument tone with high fidelity. The amplifier has a frequency response of approximately 7 Hz to 50 kHz (-3 dB), signal-to-noise ratio greater than 77 dB at full output, input sensitivity of 460 mV for full output, and input impedance of 1 MOhm. Output taps are provided for 4 and 8 Ohm loads. Dimensions are approximately 260 mm width, 470 mm depth, and 240 mm height, with a weight of 22 kg per unit. The M845 is priced at £7499.95 per pair (approx. ).