Much of what is wrong with transistor amplifiers can be surmised in two words; switching distortion. The sound of those little three legged semiconductors turning themselves on and off on demand is omnipresent, and most people get used to it – rather like rain in winter. It has a similar effect on the sound too; it becomes grey and dull, and less than pleasant to be out in. Indeed, switching distortion creates a kind of ‘hash’ or ‘mush’; it’s like a dreary, cloying fog that simply takes the fun out of life.
In most of the better designed solid-staters, it’s relatively benign, and manifests itself as a sort of gentle cloudiness, a bit like twiddling your camera lens out of focus slightly and knocking the shutter speed up a bit, as if to create an ‘underlit’ photograph. Often, in good mid-price amplifiers, you really don’t notice it so much, enjoying instead the bits of the sound that the amp gets right, such as bass grip and transient speed. Still, move to the likes of a full Class A and again the Class AB design sounds a tad dull and mushy.
So why not use Class A all the time? Well, one twiddle of the volume control holds the answer. In order to run full Class A, you need the output transistors constantly switched on (hence no switching distortion). This creates vast amounts of heat, and so your output power is limited by the amount of heat your casing can dissipate. As most amps are just 430mm wide (and not half as deep), then you’ll be lucky if you even get the 20W the Sugden squeezes out. The result is that you seem to be stuck between high powered and punchy Class AB amplifiers like Naims, or open and spacious sounding but weak kneed curios like the Sugden.
Constrained by cost and cooling issues, the only way to get real wallop is to throw vast amounts of money at the problem by building a massive powerhouse of a thing, such as a Krell, capable of dissipating several bonfires-worth of heat without so much as an expired output device. But JungSon’s JA-88D seems to have found a way around this. Despite its £900 price tag it runs 80W per channel of pure Class A (claimed), and is built like a Russian tank. Chinese made, you get a lot of metal for the money. It is huge at 470x430x190mm, but the detailing is poorer than some similarly priced amplifiers; the cooling slats have slightly rough, abrasive edges for example.
Another downside is the garish fascia, which sports large bright blue backlit VU meters which won’t be to all tastes. The volume control is a little noisy as it runs up from 0 to 99 – there’s the odd click and pop through the speakers, and disappointingly at close to full whack some feint signs of mains hum too. Other detail touches are nicer, not least the natural hardwood remote control. The massive chunk of brushed aluminium used for the fascia looks thick enough to resist the best efforts of a sniper rifle.
The JA-88D sounds clear in a way that no Class AB amplifier can be, with a wonderfully open but brightly lit sound. It’s not bright in the sense of harsh or forward, and not even glassy, it’s just that it throws the soundstage into sharp relief. It scythes through multi-layered rock music and cuts right to the heart of the music. Vocals are smooth, not in the euphonic, valve-sense, but in the sense that there’s no discernible glare, brittleness or grain. Here we have a transparent, smooth and couth transistor amplifier that is both powerful and punchy enough to aspirate big, hard-to-drive loudspeakers. Better still, its midband is truly emotionally articulate, and doesn’t shy away from dynamic contrasts.
Wound up to really high levels, the JungSon does take on a slightly harder and edgier sound. Happily, the point at which this happens far exceeds normal listening levels. Bass remains truly tuneful, whilst keeping its sledgehammer quality. In essence it sounds like a Sugden A21a on steroids; one that’s been working out in the gym for a very long time, and has emerged into a rather different beast. The JA-88D lacks that last fraction of the A21a’s joyful tunefulness in the midrange, but the extra dynamic confidence more than makes up for it.
A beguilingly clean design right across the frequency band, its treble glint means it shouldn’t ideally be used with bright ancillaries, but smooth ones work great – especially as the amplifier ages, runs in and smoothes out. At under £900 in 2006, it had to be one of the best budget audiophile buys in a very long time.