Proprius High Fidelity Monoblock Power Amplifier
Please note: Due to the large volume of orders and the impact of COVID 19 in the UK, your order that would normally take 2 - 3 weeks to arrive, could be delayed and lead times of 4 - 6 weeks are to be expected in 2021/2022.
The Proprius has all the sonic hallmarks you expect from a Graham Slee design.Listening is riveting, involving and fatigue-free. Using two for stereo, imaging is spatially focused and "walk-through" - transcending the speakers, but importantly, the music remains cohesive. The Proprius is tonally accurate producing a silky and fluid treble with no hint of brightness or grain. Good bass extension and articulation meters out appropriately scaled slam and "grunt", as well as rhythmic satisfaction. Vibrant dynamics with impeccable timing keep a grip on the performance, with no loss of underlying subtle melodies.
You may think a 25 watt amplifier is too frail, but the Proprius is anything but! Each output transistor can handle 25 amp peaks and 200 watts, and at 30MHz their high frequency performance is ten times higher than regular output transistors. The Proprius outboard power supply is 120 watts to provide unassisted the 2.5 amps its 20 volt peaks demand. Only with impedance dips and when driving 4 Ohms are its reservoir capacitors called on to release stored energy required to ride transient peaks.
Finding space for all your hi-fi gear can be tricky, but at just 10.5cm (4.1") x 6cm (2.4") x 20cm (7.9") you'll easily find the space for a pair!
Why not? We gave the Proprius a volume control to give you more flexibility. In a frugal single source system you don't need a line-stage, just a pair of Proprius. In a surround system you might wish to balance the sound levels on each amp. The same if you're bi-amping or tri-amping. What if your preamp doesn't have a balance control? But if you don't need a volume control, just set it to max!
A single XLR input connector accepts both balanced and single ended feeds. Connect it to a balanced source and the interconnect length can be considerably longer meaning you can place the Proprius at the speaker, or even screw it to the speaker back with the supplied adaptor plates.
Most domestic listening is done at around 1 watt. With medium sensitivity speakers that single watt produces around 80-90dB of sound pressure one metre in front of the speakers. The emotional signature and spatial information in the music is much lower in level - perhaps a tenth of a watt or less. Unless properly biased into conduction, an amplifier output stage will distort and sound "dry" (Class-B). Give it more bias and the sound is clearer with more body, but give it too much bias (Class-A) and the bandwidth is curtailed often resulting in a "warm" and "syrupy" sound. High-Bias provides just the right amount, bringing out the emotional signature and spatial information your music craves.
Untypically the Proprius behaves impeccably during power-up and power-down - no loud "thuds" so it doesn't have or need any current stealing output relays. There are no damaging DC offsets so you can plug and unplug its XLR without fear. It has intelligent output protection (which incidentally doesn't act prematurely) and because it doesn't have any nasty DC offsets on its output, it allows you to connect and disconnect speakers while it's on. And because there is no DC on its output it cannot damage your speaker voice coils.
25 Watts into 8 Ohms / 45 Watts into 4 Ohms
High-bias class AB — not class D or T
Rugged 25 Amp 30MHz output transistors
Balanced or single-ended line level input
Volume control for use as standalone amp (set at max when under preamp control)
Effective heat radiator case for comfortable high-bias running
No DC offset on output
|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|