MULTIMEDIA

Krell S-550i – Not An Amplifier, It’s A Kind Of A Beast. (Part 2)

9/11/2013 11:11:24 AM

Going all spinal tap

Without wishing to contradict my oft-stated aversion to ear-bleeding levels, I must admit that – on occasion – I do go all Spinal Tap on my system, if both the mood and the music invite it. Oddly (another admission) I do not necessarily mean music that begs copious levels, such as ‘I Can’t Explain’ by the Who, or ZZ Top’s ‘Gimme All Your Lovin’’, songs that simply cannot be played softly. Instead, I base my volume settings according to the vocalist’s angst.

 
Krell’s S-550i will be the potent 2 x 275-watt “big brother” to the firm’s current S-300i integrated amp.

Krell’s S-550i will be the potent 2 x 275-watt “big brother” to the firm’s current S-300i integrated amp.

Why I am currently undergoing a Glen Campbell obsession has much to do with his acclaimed farewell album of last year. As one of the most intensely tortured songs I’ve ever savored from the country milieu is Conway Twitty’s sublime ‘It’s Only Make Believe’: I was delighted to find it on Campbell’s Collection [EMI Gold 243 5 77507 2 1], and played it to death while reviewing the MyDAC.

It builds to an intensity that is almost disturbing, a mass of instruments and voices as grandiose as the J Geils Band’s ‘I Can’t Believe You’ or Dolly Parton’s reading of ‘Put A Little Love In Your Heart’. Campbell soars, the key changes lifting him up, up, up to a point where you think his voice just has to crack. It doesn’t.

Neither does the Krell. The form, the scale, the sheer power were so capably, competently resolved that to ask more would be to exhibit the selfishness of some cretin on The Only Way Is Essex.

Never did the Krell miss a beat. And never did I miss separates.

Never did the Krell miss a beat. And never did I miss separates.

Inevitably, though, one must bang head if one is to exploit the power of the Krell in a brutal manner, rather than as a means of preserving dynamic swings or other bombast-free uses of a surfeit of wattage. With iPod in hand, I played Led Zeppelin’s ‘Good Times Bad Times’ from the Mother ship collection, an MP3 download.

Aaah, Bonham’s percussion! ‘Massive’ is one of those words like ‘awesome’ or ‘epic’ that has become robbed it of its true meaning and impact, but there is no other word to describe the sensation. The man abused those drums; beat them like a crazed version of a Roman galley’s pausarius, and the power was palpable. Beneath it was Join Paul Jones’ rich, mellifluous bass. The Krell offers both a podium.

Never did the Krell miss a beat. And never did I miss separates.

Krell’s Legacy

Krell’s enduring legacy is that of a high-end brand with a penchant for power. I’ve lost count of the number of Krell amplifiers that have served time in my system, but not one can be recalled for any lack of power.

Krell’s enduring legacy is that of a high-end brand with a penchant for power.

Krell’s enduring legacy is that of a high-end brand with a penchant for power.

It must be remembered that Krell first made its presence known by being able to drive seemingly impossible loads, most notably the various Apogee full-range ribbon speakers (especially the Scintilla). Thirty years ago, Krell amps were the default choice for something unbreakable, unbowed by ‘difficult’ oats. The S-550i continues this tradition, but with one or two nods to the 21st Century, including its iPod dock. For those who might wonder how so much can be offered for a relatively reasonable $7547 – and that is ‘reasonable’ in the context of amplifiers of this power delivery – one needs to look at the small print at the back. ‘Made in China’ it says.

Lab report

The amplifiers may be separated by some four years but the new S-550i bears a striking technical resemblance, extra power notwithstanding, to Krell’s own S-300i [HFN Feb ‘09]. Both amplifiers share a distinctive distortion pattern of 3rd, 5th, 7th and further odd harmonics that are highest at low power (~0.065% at 1W/8ohm) but then reduce with increasing power to ~0.035% at 10W, ~0.012% at 100W and 0.008% at the rated 275W/8ohm. This trend, incidentally, is also shared by darTZeel’s extraordinary NHB-458 monoblocks [HFN Jun ‘12] and is consistent under continuous or dynamic output conditions [see Graph 1, below]. The latter graph also illustrates the S-550i’s prodigious capacity, its 2x275W/8ohm rating exceeded to the tune of 2x335W/8ohm and 2x600W/4ohm and lifted still further to 390W, 750W, 1370W and 2400W into 8, 4, 2 and 1ohm loads under dynamic conditions. This makes the S-550i the most powerful and load-tolerant integrated that we’ve tested in HFN for many a year (if not ever).

Dynamic power versus distortion into 8ohm (black trace), 4ohm (red), 2ohm (cyan) and 1ohm (green) speaker loads. THD falls as power increases

Dynamic power versus distortion into 8ohm (black trace), 4ohm (red), 2ohm (cyan) and 1ohm (green) speaker loads. THD falls as power increases

The amp’s output impedance is not vanishingly low at ~0.075ohm but it is very uniform across the audio range, as is its frequency response almost irrespective of load (-2.05dB/100kHz into 8ohm to -2.25dB/100kHz into 1ohm). Like the S-300i, however, the S-550i also shows an ‘engineered’ mid-bass bump of up to +0.05dB from 50Hz-300Hz just as its overall A-wtd S/N ratio is about 10dB lower than the ‘average’ integrated at just 73.4dB (re.0dBW). Like the S-300i this is not hum but a broad white noise that may exert some pleasing subjective influence. Readers may view an in-depth QC Suite report for Krell’s S-550i integrated amp by navigating to www.hifinews.co.uk and clicking on the red ‘download’ button.

 
Distortion versus extended frequency from 5Hz-40 kHz at 10W/8ohm. Trend is fairly uniform

Distortion versus extended frequency from 5Hz-40 kHz at 10W/8ohm. Trend is fairly uniform

Specifications

·         Power out (<1% THD, 8/4ohm): 335/600W

·         Dynamic power (<1% THD, 8/4/2/1 ohm: 390W/ 750W/ 1.37kW/ 2.4kW

·         Output impedance (20Hz – 20kHz): 0.070 – 0.083ohm

·         Frequency response (20Hz – 100kHz): +0.05dB to -2.0dB

·         Input sensitivity (for odBW/275W): 71mV/ 1200mV (balanced)

·         A-wtd S/N ratio (re.0dBW/275W): 73.4dB/97.8dB

·         Distortion (20Hz – 20kHz re.10W/8ohm): 0.055 – 0.016%

·         Power consumption (Idle/Rated o/p): 81W/978W (2W standby)

·         Dimensions (WHD): 438 x 148 x 450mm

Verdict

There have been massive integrated amplifiers int eh past, such as Perreaux’s Eloquence 250i, which obviate a need for separates. Without hesitation, I nominate the S-550i as a perfect choice for those who want unbridled power yet will not or cannot house two components. It is a beast of an amp, such that I think I’ve found something currently available to drive even Scintillas. Yes, that kind of beast.

Sound quality: 87%

Sound quality

 

 

 

 

 

 

 

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