McIntosh MA6300 review

McIntosh is best known for its distinctive, retro-styled components, which now embrace multichannel as well as stereo equipment (it has begun to include loudspeakers, too). The other thing it is well known for is its advocacy of valve-based amplifiers.

A number of the oldest McIntosh designs date back almost half a century, and have legendary status. Some of those early classics are still in everyday use, while some of the newer models, including the MA2275, are closely modelled on those seminal designs. Lately, McIntosh has been spreading its wings, a move that appears to have been precipitated by its incorporation into the D&M group, whose two largest member companies are Denon and Marantz.

One of the more decisive moves the company has made, which was presaged at the last Las Vegas CES trade show in January, was to introduce some entry-level products - or at least what passes as 'entry level' for an upmarket manufacturer like McIntosh. The subject of this test is one of these more easily 'affordable' newcomers.

To produce an amplifier that doesn't cost a King's Ransom, but which still offers plenty of grunt for not excessive money, McIntosh has taken the solid-state route. This may not at first appear to be where its corporate heart lies, but the company has been using transistor-based design in some models for quite some time, so it's not an entirely new departure.

The basics are as follows. The MA6300 is an integrated stereo amplifier that delivers 100 watts per channel into 8 ohms, rising significantly to 160 watts per channel into four ohms. The unit has a moving magnet phono stage, five single-ended, line-level inputs and a tape input, plus one balanced input using the usual XLR terminals.

Rear panel links

The pre- and power amp sections communicate via removable rear panel links, and a single pair of speakers and headphones can be connected. In addition, each input has its own serial data control socket, which can be linked to a separate McIntosh source component for remote power on/off purposes. The volume control is an unindented analogue rotary control; a second with a centre detent is used to set channel balance.

The amplifier is supplied with a remote control handset of rather pedestrian styling that can also operate McIntosh source components. The amp itself has all the traditional styling cues of other models from the company, including a glass front panel with screenprinting applied on the inner surface, where it will not be subject to physical wear. Styling is determinedly retro, and as usual the front panel and its blue power meters are internally lit by LED light sources and fibre optics.

Technology highlights include an R-core transformer at the heart of the power supply, and so called ThermalTrak output transistors, which have an extra pin and an internal sensor to monitor their own temperature and to adjust bias levels to maintain thermal tracking. There's actually nothing new about these transistors - the first application that came to our attention was in Kenwood amplifiers in the mid-1980s, where the technology was unaccountably (and somewhat unfortunately) known as TRAIT-R.

In contrast, R-core transformers are more recent. Matsushita first developed them if memory serves, about a decade ago. R-core technology offers more compact packaging, less electromagnetic flux leakage and very high efficiency compared to toroidal transformers, which set the standards in pre R-core days - some would argue that toroidals still set a benchmark - their popularity in hi-fi electronics is still strong.

Input switching is by noiseless electromagnetic switches, and housekeeping electronics include the Power Assurance System, which monitors output levels, momentarily throttling the amplifier back if an over-drive condition is identified, and restoring full operation thereafter, with an attack time of one two-thousandth of a second. This is a relatively cool-running amplifier, so bias levels in the output stage are clearly not high.

We have had good experiences with the McIntosh products in the recent past, and first impressions here were in line with expectations. In general terms the MA6300 sounds like a superior sort of amp, with gravitas, dynamic range, a clean treble (not always the case with silicon-powered amps), a solid sense of midrange depth and tonal variety - all the things that mark good amplifiers out from the other kind, in fact. Except for one thing.

It took a while to recognise what we were not getting from the MA6300, in part because we started out using it for general jobbing duties, mostly at low-to-moderate volume levels - the power meter indicators rarely intruded into the space above one watt - and with speakers of quite high sensitivity, high sensitivity speakers are a disincentive to drawing too much power.

It was only when we began to stretch the amplifier by using it to drive less sensitive loudspeakers (Vienna Acoustics, Opera and so on) at higher volume levels, that we began to notice that it was inconsistent in its behaviour. While at moderate volume levels the amplifier did perform well, as described above, as soon as the leash was slipped, it was apparent that the McIntosh didn't sound as comfortable, and that a certainly granularity and harshness had crept into its voice.

Not that it sounded bad; still less anything remotely approaching unlistenable. The MA6300 remains what it appeared to be at first shot: a classy and capable amplifier. But, because its aural signature was at some level not quite consistent, the amp was also not transparent. We could hear it working, almost perceptibly drawing its breath to attack the loud passages, and this was enough to take the edge off the clarity. The harsher sound when the amplifier was running hard made the music sound synthetic.

Uncomfortable

If the same quality had been there to the same degree at all volume levels, it might have been possible to acclimatise to the effect, and mentally filter it out. Instead, what we heard - and what we think listeners generally will hear sooner or later - is an amplifier that sounds just slightly uncomfortable, one that doesn't quite rise seamlessly to crescendos in acoustically recorded music.

Paradoxically, on other electronically generated music types where the dynamic range is never permitted to get out of hand, the MA6300 performed better. Here, the music prompted less reaction from the amplifier when under duress.

Nevertheless, this remains a fine amplifier, and in many respects an excellent one. The balanced input is not as effective as its counterpart in Krell amplifiers, where the gain stages are inherently balanced throughout. That said, the McIntosh sound did gain a sense of space and light that its single-ended inputs couldn't quite aspire to, and this was when using the same cable type (Nordost Valhalla) in a single-ended/balanced mode comparison.

That same sense of air and light suffused the amplifier at lower volume levels anyway, and remained part of the equation when pumping watts too, to an only slightly lesser degree. At these elevated levels, however, the sense of an endless dynamic range was noticeably reduced. It may be that increasing levels of harmonic distortion at higher levels caused what we experienced from this amplifier here.

This is an amp with a powerful sense of tonal colour, expressiveness and - in a mark of a worthwhile amplifier - its capabilities seem more fully formed and rounded with acoustic material than electronic. Here, the more complex and subtle tonal colours, and the greater sense of expressiveness shine through, subject to the qualifications already stated.

Bass is well extended, with more of a sense of warmth and grace than expected from some solid-state amplifiers, perhaps in deliberate emulation of the strengths of the valve amplifiers in the McIntosh range.

What started out looking like another clean sweep for the expanding McIntosh stable turns out to be an attractive and generally well implemented design, at a somewhat more accessible price than usual. However, under dynamic drive conditions there are limitations that in the final analysis make the listening experience a little anticlimactic. Alvin Gold