Graham Slee Proprius Monobloc Power Amp

Graham Slee Proprius Monobloc Power Amp

The Graham Slee Proprius Monobloc power amplifier delivers 25 watts into 8 Ohms (RMS) and 45 watts into 4 Ohms.

It's a mono-block amp so two are required for stereo. We made it this way for a variety of reasons — one of which allows them to be used remotely at, or fixed to, the loudspeakers for powered monitor performance from your favourite passive speakers — see speaker mount tab. The great thing about mono-blocks is they give you true dual-mono amplification for improved stereo separation. They're perfect for use with high sensitivity speakers where quality comes before quantity. However, they're not short on quantity and sound louder than their 25-watt rating would suggest, even using speakers as low as 83dB sensitivity — including the Stirling Broadcast/BBC 11 Ohm LS3/5A.

The balanced XLR input works just as well single ended with shorter interconnects so using them side by side like a normal amp isn't a problem — you can find suitable interconnects in our Cables & DIY section. For remote or speaker mounted placement requiring long cable runs, you'll need a source with balanced outs and our balanced audio cables. Unusually for a power amp, the Proprius is equipped with its own volume control meaning it can be used from a fixed output source. When using it with a control preamp the volume control is put "out of circuit" by parking it at full rotation.

The input is based on the balanced topology by David Birt of the BBC, modified to "all-inverting" making it free of common mode distortion. Absolute phase is accomplished by "phase swapping".

Who is Graham Slee?

Graham Slee is a small, enthusiastic manufacturer of realistically priced, high-performance phono stages and headphone amplifiers, designed and built by hand in Yorkshire since 2003. Very positively reviewed by the UK and international magazines, demand for these products has been overwhelming as the world's hifi enthusiasts can't believe the performance on offer for the price asked.