Pre/Power Amplifiers

There's nothing terribly unusual about a big, hefty US-made power amp: after all, it's almost an archetype of what we think the US high-end is all about. Long cable runs from preamp to power amp(s), short tails to the speakers – it's just the way they do things over there, and at first glance the Parasound Halo JC5 seems to conform to all those preconceptions.

Except it isn't quite what it seems, for while the £6999 amp, available in black or a rather more subtle silver, has the big, bluff looks of a Stateside powerhouse, it's neither that huge nor excessively heavy and is even vaguely sensibly priced when placed beside the five-figure tags you'll find elsewhere. OK, so it will dwarf your average European integrated amp, and £7k is hardly chicken feed, just as its 33kg deadweight means it's a two-person lift.

The latter feat is helped by grab-handles to the rear, hindered by sharp heatsink fins and not much to get hold of at the front. But once you and a willing assistant have it in position – I found my trusty leather rigger's gloves came in handy – it's not exactly a monster, at under 45cm wide (so not much more than a 'normal' hi-fi component) and 20cm tall, putting it in 'big AV receiver' territory. Only the depth may give you some problems when it comes to positioning, as it's just over 50cm front to back, meaning it overhung the shelves on my favoured Quadraspire rack.

Mind Your Manners
Then again this is a well-mannered big amplifier, despite its 400W/8ohm rating, rising to 600W/4ohm, and capable of handling dips down to 1.5ohm [see PM's Lab Report, p75]. Those heatsinks manage to keep things working reliably without either the assistance of fan-cooling or warning notices to keep animals and children at a safe distance, and there's no drama involved in turning the amp on: none of that 'lights dimming throughout the house' or 'now the storm is at its height, throw the switch, Igor' stuff.

Instead, a push on the power button sees its illumination change from the soft blue indicating standby to red for a few moments while the amp stabilises, and then shows a brighter blue when you are ready to play music, accompanied by the illumination of the two channel indicators low down in the centre of the front panel. One other lamp indicates a temperature problem, at which point the amp will drop into protection, something I failed to provoke even during arduous use.

In fact, there's a range of ways to turn the amplifier on: either manually, via a 12V trigger or via (music) signal-sensing. A potentiometer allows the user to select the sensitivity of this mode of operation, and avoid it being affected by noise on the mains, which might otherwise switch the amp on when not required.

Volume Controls
The RCA phono and balanced XLR inputs also have their own level adjustments, not unlike little volume controls, although using these is a little hit and miss given the slight channel imbalance PM also notes in his Lab Report, and the fact the knobs aren't click-stopped to give some precision in their setting. The JC5 includes loop outputs to allow additional amplification to be used, for example when bi-amping suitable speakers, or to feed one or more active subwoofers. However, its input level adjustment doesn't affect the signal level being output from these sockets, so if you were using two JC5s to drive your speakers, you might have to juggle these little input level controls or, I suspect, leave them all rotated to maximum.

Switches select between the RCA and XLR inputs, with one for each channel, while between this socketry another small toggle allows the user to bridge the amplifier into mono. The two red '+' terminals – 'propeller' combination binding posts custom-made by CHK Infinium – are then used for connection to the loudspeaker (and are labelled accordingly). At this point the JC5 becomes a monoblock amplifier rated at a heady 1.2kW/8ohm!

Whether one would ever feel the need for such capacity is open to discussion, for the Halo JC5 is hardly short of power or dynamic ability in its standard stereo guise, as one might expect of an amplifier based on the John Curl-designed JC1 monoblock power amps. But this isn't a pair of JC1s crammed into one package, as PM discusses in his boxout, below. Parasound says it is the result of challenging Curl to 'distil the essence of two JC1 monoblocks into a single chassis' in response to demand from customers who 'often tell us they love everything the JC1 offers while wondering if we could deliver comparable performance from a no-compromise stereo chassis, to save money and space.'