Graham Slee Proprius Monobloc Power Amp

Graham Slee Proprius Monobloc Power Amp

Free UK Delivery



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 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.

Each unit is designed by owner/ engineer Graham Slee and then hand constructed by two skilled electronics engineers before being thoroughly tested to check it meets it's specification and is 100% reliable.

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 direct 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".



 Power output (rms) measured 26 Watts into 8 Ohms;
45.5 Watts into 4 Ohms
(ref 1% THD+N at 1kHz)
Power bandwidth at rated power into 8 Ohms  10Hz - 47kHz (-3dB), 20Hz - 25kHz (-1dB) 
 Power bandwidth at rated power into 4 Ohms 12Hz - 40kHz (-3dB) 
Total harmonic distortion and noise at 8 Ohms  100Hz: 0.043%;
1kHz: 0.047%;
5kHz: 0.061%;
10kHz: 0.085%;
20kHz: 0.125%
Total harmonic distortion and noise at 4 Ohms  100Hz: 0.066%;
1kHz: 0.071%;
5kHz: 0.094%;
10kHz: 0.129%;
20kHz: 0.181%
Signal to noise ratio in dB  "A-weighted": 87dB; 22Hz-22kHz "Q-pk": 80dB 
Bias type  Class Ab; Bias current: 60mA (approx.) 
 Input sensitivity for rated output 575mV rms 
 Short circuit protection  Fuse and power supply shut-down
(short circuits should be avoided to prevent
component stresses)
Fuse  F2A 5mm x 20mm
(glass "quick-blow" fuse rated at 2A)
 Power supply 48V DC, 120 Watt - self adjusting to AC mains
100V - 240V, 47 - 63 Hz;
IEC cord supplied
Size (approx.) Amp W105 x H55 x D205 mm;
Power supply W65 H40 D170 mm

Providing your item is in stock, the order is usually dispatched within 24 hours. Please remember that postage and packing is completely free for orders over £50*. Out of stock items will be dispatched as soon as they become available, out of stock items can take between 4 to 21 days for dispatch.

Deliveries usually take 1-3 working days. The majority of orders are sent via our couriers'; Interlink Express on a next-day-delivery service. Smaller, low value or light-weight items are normally posted using Royal Mail Recorded or Royal Mail Special Delivery.

Once your product has been dispatched, you will be notified via email and sent a unique consignment number, you can use this number at to check the status of your delivery. If you have provided a mobile telephone number, Interlink's Predict service will notify you by text (and email) of a one-hour delivery window. If the window they suggest is inconvenient, you can change the date of delivery to a later one via text or email.

*We ship free of charge to mainland UK addresses, excluding the Scottish Highlands or 'Out-Of-Reach' Scottish locations. Please consult the post-codes below to see if your location falls within this category. If you are still unsure, please contact us on 01432 354921. We also ship to Northern Ireland, Channel Islands, Scilly Isles, Scottish Isles and Scottish Highlands, however delivery to these locations will incur a charge and can only be sent via a 2-day service.

Shipping CostsMainland UK (Next-Day)Offshore/Out-of-reach (2-day)Northern Ireland, Channel Islands, Isle of Man, Scottish Islands, Scilly IslandsRepublic of Ireland (2-day)
Under £50 Orders £7.50 £12.50 £15.00
Over £50 Orders FREE £19.99 £29.99
Surcharge Orders £50.00 £69.99 £79.99
Saturday Delivery £12.99 N/A N/A
Sunday Delivery £12.99 N/A N/A
Saturday by 12 Delivery £35 N/A N/A


Post codes exempt from the free delivery service include:

Scottish Highlands Post Codes: AB30-38, AB41-42, AB44-56, FK17-99, G83, IV1-28, IV30-39, IV52-54, IV63, KW1-14, PA21-33, PA34-40, PH15-26, PH31-41, PH49-50
Islands Post Codes: HS1-9, IV40-51, IV55-56, KA27-28, KW15-17, PA20, PA41-49, PA60-78, PH42-44, ZE1-3
Northern Ireland: All BT postcodes
Channel Islands Post Codes: JE, GY
Scilly Isles Post Codes: TR21, TR22, TR23, TR24, TR25

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