Sugden Audio Masterclass IA-4 integrated amplifier
Sugden are survivors. There aren’t very many independent British electronics brands that have been around since the ark and Sugden go back further than Linn, Naim and Rega, all of the older brands have been bought up by international operations. Last year Sugden encountered a major set-back when MD Patrick Miller passed away after a short illness, at the time the company had an unusually long lead time for orders and getting products for review was nigh on impossible. Subsequently the new management have turned things around and are able to supply both customers and reviewers alike, having heard Sugden amps sounding great on numerous occasions but only ever having had the A21 integrated at home I requested the biggest integrated in the catalogue, the Masterclass IA-4.
The IA-4 is big but not enormous, weighing in at 20 kilos (44 lbs) and standing 16.5cm (7 inches) high it has a commanding presence but is easy to move. Like all of Sugden’s great amps the IA-4 is a Class A design so its power output of 33 Watts doesn’t sound very impressive given its bulk, but it has a lot of current capacity and will drive some surprisingly low sensitivity loudspeakers. Class A upsets the ‘more is better’ theory of amplifier hierarchy, it reveals that controlling a loudspeaker is not just about Watts as any tube/valve amp enthusiast will tell you. If you want bone crunching bass look at a Class D design but if you want finesse, filigree detail and musicality Class A designs are a good place to start.
The IA-4 like other Sugden components is available in standard Titanium (silver) and Graphite (black) finishes or, for the more adventurous, one of 13 anodised shades that include three blues, three greens and the Bronze that was sent for assessment. There is also a stealth black option that I’m told looks damn good. Given the option I think that the Red with silver controls would have been my choice but the Bronze is more opulent and contrasts well with black controls. The latter you may notice have been arranged symmetrically such that the power button is the same size as the volume and input selectors, making it the largest power button in the known universe; at least it’s not hidden under the chassis.
The input array includes a pair of XLRs, an MM phono stage, three line inputs on RCA and a tape input. Effectively this means that it offers five line inputs plus phono which is a high count by the standards of high end audio. On the output side it has pre- and tape-outs which can be used for a subwoofer or even a processor should such things be required. The speaker cable terminals are not branded but decent quality examples in the WBT style that should keep banana, spade and bare wire under control come what may.
The front panel offers switches related to the tape loop facility as well as a simple white LED light to indicate that it’s on, touching the case under this circumstance will confirm as much by being rather warmer than usual. Those helpfully rounded heatsinks are not just their for style. Class A by its very nature runs hotter than the alternatives so don’t stick the IA-4 in a cupboard. Sugden supply a slightly unusual remote handset with this amp, one that features six buttons marked with up and down arrows, these can be used to change volume and that’s it. It’s an elegant handset in its minimalist way but input selection would a nice touch, still there’s only a slight initial confusion over how it works.
Sound quality
The only problem with the remote is that only those with the lightest of touches, concert pianists maybe, will be able to make a small volume change with it. Getting it do change level by less than 3dB is an achievement. That said the knob itself isn’t a lot better. This is a characteristic I have encountered with Class A valve amps in the past and is only inconvenience in the design.
As they were in the system and impossible to move I initially tried the IA-4 with the mighty Vivid Moya M1 speakers, this proved highly engaging but a little on the soft side. It’s a very unlikely pairing but worked better than expected, the Moya has high 93dB sensitivity but a demanding impedance minimum of 2.5 Ohms at low frequencies, which meant that the bass was on the fulsome and occasionally excessive side. That said the Sugden IA-4 brought out the ethereal and cosmic side of many recordings, exchanging the precise hard edges of the Class AB amp with something more forgiving and inviting.
This is more of an emotional than a physical sounding amplifier in this company at least, one that lets you sit back as the music washes over you and carries away any anxieties. The fabulous e.s.t. 30 live album offers up plenty of energy and scale at a slightly more relaxed pace than usual, and when the flute break comes along in Tuesday Wonderland it has an intimacy that is profound. One area where the Sugden did better my usual power amp was in its low level performance, it’s a classic Class A quality and means that you can enjoy your music at a broad range of volumes.
With a slightly more price appropriate loudspeaker in the Bowers & Wilkins 702 Signature (£7,000) which has a much sharper and more forward balance than the Vivids the Sugden proved a good match. It’s inherently relaxed nature balancing out the eagerness of the speaker really well. This is a reasonably sensitive speaker with an impedance minimum of 3.1 Ohms yet the IA-4 had no difficulty driving it, extracting real energy whilst smoothing off some of the sharp edges without undermining engagement or speed. I loved the way it built tension on Fridge’s ode to Tortoise, Five Four Child Voice, which proved much more interesting and engaging with this amp/speaker pairing than usual.
It’s hard to pin down exactly why but the Sugden IA-4 makes music more absorbing than many alternatives, it’s probably because it tracks micro dynamics so well, the small changes in level that gives each instrument or voice more variety and realism. It’s what makes Class A so addictive but not all examples of the genre are as capable as this, the IA-4 has real current to back up its small scale linearity, so the bigger dynamics are not restricted. In fact it can do real punch without big volume which is very appealing when combined with a loudspeaker like the 702 Signature. Equally critical is that it times superbly, you might expect that such a relaxed demeanour would undermine immediacy but that is clearly not the case here.
While imaging is not quite as precisely defined as it might be, the sound is plenty big and not overblown, its strength lies in musical flow that is in a different league to most amps at this price. It also doesn’t have the stridency that Class AB designs can exhibit, it’s rare to find a saxophone becoming uncomfortable or a recording that sounds too sharp, even with a speaker like this B&W. The balance suits acoustic material perfectly and it’s easy to see why Class A users get turned on to classical music. The Locrian Ensemble’s Mendelssohn Octets sounded inspiring, beautiful and charming all at once.
I tried the IA-4 with a pair of Dali Rubikore 8 floorstanders (90.5dB, 4 Ohms) which work really well with my 150W Moor Amps but discovered that this wasn’t such a happy pairing, I suspect that the impedance was probably the issue but balance is also a factor. So I switched in some PMC twenty5.26is which are reference speakers in these parts, they have low 86dB sensitivity and an average 8 Ohm impedance, but this proved to be a very happy combo with a snap to its timing and welly in the low end to match. I loved the open, fast sound of Zakir Hussein’s Making Music with these speakers under the Sugden’s guidance, the attack and decay of the notes in his tabla solo were breathtaking. All too often the speed of his fingers becomes a blur but here you could appreciate the tiny spaces in between which makes the playing even more impressive. John Fahey’s Fare Forward Voyagers (1973), an album of acoustic guitar, was surprisingly the live and vigorous with the IA-4 in control of the PMCs, the sound having a presence an energy that belies its age.
Conclusion
This amplifier was recommended to me by Kevin Scott of Definitive Audio, he has been using Sugden amps with Living Voice speakers for decades and feels that the IA-4 is about as good as you can get for the money, and that includes some pure valve designs that are very competent. I wasn’t able to try a speaker that is really designed for the power on tap with the IA-4 yet got superb results with two of the four options I partnered it with. It’s more of a musically enchanting amplifier than most, and that makes you want to use it for longer, to explore new and old releases and fully engage in the results. This puts it in a select class of amps regardless of price, it delivers a result that keeps you listening and that more than makes up for its lack of digital inputs and raw power.