Longdog Audio P6100M Monoblock Amplifier Review
David Price gets hot under the collar with this classy pair of power amps…
P6100M Monoblock Power Amplifiers
Freedom of choice is the greatest weapon that consumers have because it keeps the market honest. People vote with their cheque books or credit cards, and if enough of them don't go for mainstream designs, then major manufacturers find themselves forced to rise to the challenge of making things that folk actually want to buy. This is only possible when there's a healthy, fast-moving and nimble specialist scene, with smaller manufacturers doing interesting and quirky products that get the hobbyists hot under the collar.
Longdog Audio fits bang-slap into the latter category. Run by the highly knowledgeable Nick Gorham, it makes seriously good products that, were they from 'premium' brands would have far heavier price tags. He also designs and manufactures under the Hi-Fi Collective and MCRU brands, plus a range of pro audio products including ultra-low noise stompbox power supplies. These are unfailingly utilitarian; they're devoid of frills, with the money spent inside of the case, where it matters. I've used an LDA power supply with my Audiolab M-DAC for nearly a decade, and it's been faultless.
His new P6100M monoblock power amplifier is an attractively styled thing, but we're not quite in Devialet territory – yet that's not the point. Once again, it's what's under the hood that counts, and here we have a 100W RMS amplifier that's heavily biased into Class A. It uses reliable and rugged MOSFET output devices, and when sold as a pair costs just £3,500. That's the sort of money that serious audiophiles routinely stretch to, providing the product gives the desired result. “Each amplifier runs 400mA of bias current, and so is good for about 10-15W of Class A before moving into B”, Nick tells me – so in most people's listening typical listening conditions, they'll rarely get out of Class A.
He's a serious tube amp fan, but real-world enough to know that this technology isn't a universal panacea. “When I originally started the design work, I wanted to make something that sounded like a good 2A3 direct heated triode valve amp in the midrange and treble, but with solid-state power in the bass”, he told me. That's why he chose a particular type of MOSFET output device, to get a claimed 100W RMS per channel into 8 ohms, and 190W into 4. Instead of using multiple arrays of output devices paralleled up to achieve its rated power output, this amplifier sports true single-die, high power MOSFETs, run in complementary pairs to give a balanced output stage. Before this, a special driver stage feeds each of the two MOSFET output devices in each amplifier.
The 100M part of its this amplifier's name refers to its output power and the fact that it's a monoblock; however, the naming system actually appeared with “the parent that produced this offspring”, a 200W monoblock which was downsized to create this but never productionised. The P6 part of the name refers to the fact that it's a small push-pull amplifier; Nick says it's, “push (driven by push, pull), pull (driven by push, pull) – so that's six Ps…”
The thick aluminium fascia panel sports a sturdy backlit metal power switch. Round the back, you'll find chunky binding posts for one set of speakers, an IEC mains inlet plus RCA and XLR inputs; a small switch lets you toggle between the two. Inside there's a large capacity power supply with help from, “as big a UK-wound transformer as we can fit in the case”, Nick tells me. Non-ferrous casework is used, and extra care has been taken to manage thermal memory effects, he says. This amp comes in a choice of silver or black finishes, and the overall standard of build is very good for a small manufacturer. Vital statistics are 430x110x260mm and 8.5kg per amp.
Three small niggles let the side down slightly. First is the rather low rent gel name badge on the fascia, and second is the sharpness of the heatsinks. In all fairness, many rivals suffer from the latter – I had an identical issue with a Musical Fidelity AMS35i I once ran – but it means you need to wear gloves when moving it around. Finally, the pointy cone-type feet run the risk of damaging the surface they're sitting on, so pay close attention during installation.
When I review power amplifiers, I often love their grunt but wish they could be sweeter and more musical, or I adore their musicality but yearn for more watts. The Longdog Audio P6100M treads a thoughtful balance between these two extremes giving – for me at least – pretty much the best of both worlds. In amplifier terms, it's akin to a velvet fist, with power and punch when called upon, plus a passionate side that brings out the emotion in the music. That's impressive at this price.
When assessing kit, I like to steer well clear of typical 'hi-fi' recordings and hit review products with far from ideal productions. The Jam's This is the Modern World is a case in point, being a grungy slice of late seventies new wave that you'd not normally hear playing at the Munich High End Show. Yet it sounded surprisingly good here through my Yamaha NS-1000M monitor speakers. The Longdog seemed to scythe through the recording's general grime and mush to unlock the authentic low budget, late seventies analogue recording studio sound hidden beneath.
This is only possible due to the P6100M's speed, power, transparency and musicality; all four facets are well balanced here, and together they're able to get a great handle on the musical event. I found myself hearing small production details I wouldn't usually pick out, yet the purity of tone of singer Paul Weller's gruff voice was quite a thing. This monoblock also conveyed the drum work very well, imbuing it with a slam and a speed that you wouldn't think was ever on the recording. At the same time, it conveyed the distinctive tone of the lead guitars in a really earthy and realistic way. The result was a dramatic, authentic and rousing sound.
The P6100M can do more than just remove the gunk from old punk rock records though. Feed it some classic nineties drum'n'bass like Nookie's Give A Little Love, and it really thrives. This time, the amp's claimed high damping factor and prodigious power came into play, as it gripped the 12-inch bass drivers of my speakers and pummelled them with power. The track's sub-bass is quite a thing to hear through full-range loudspeakers, as this pair of LDA amps showed. Vast tracts of air seemed to be moving around the room all of a sudden, as my eyes wandered to the hairline cracks in the plaster of my listening room walls. At the same time, these monoblocks were resolutely tuneful; there was no sense that the track's cracking bass drum and synth bassline were causing problems, even at highish volumes.
Indeed, on tracks like this, I could really appreciate the superlative timing of my reference Chord Hugo TT2 DAC (driven by a CD Xt Signature silver disc transport). The interplay between the drum machine's hi-hat, bass drum and snare pattern was quite a thing to behold, as was the way the vocal samples were woven into the song in such a way as to push the groove along. Yet you don't just need banging techno to hear this, as Rose Royce's beautiful Wishing On a Star had precisely the same effect. As well as wanting to bask in the sumptuous seventies soul production, I found myself smiling at the brilliance of the vocal phrasing, and how it was absolutely central to the song. The P6100M is a powerful unlocking device, yet fascinatingly it never sounds forensic. So many other punchy power amps do bass and dynamics well yet still manage to sit on all the song's natural emotion – but not this.
Even with more traditional high-end hi-fi attributes like soundstaging, the P6100M worked very well. The Rose Royce track showed superb stage depth, with a cavernous recorded acoustic. But, when I moved to one of my favourite classical recordings – Ralph Vaughan Williams' Symphony No.2 (Haitink/London Symphony Orchestra) – the soundstage opened up further. The Lento sounded glorious – a living, breathing, swelling mass of music that had my loudspeakers dissolving away before my very ears.
It's nigh on impossible to fault this pair of Longdog Audio P6100M monoblocks on sonic grounds, considering the cost to buy. Tonally smooth, detailed and transparent, tight and punchy and unfailingly organic sounding, there's an awful lot to like at the price. I'll wager that if you're prepared to put away your preconceptions about small specialist manufacturers and go and listen for yourself, you'll fast become a fan. The only thing is that badge snobs need not apply!
David started his career in 1993 writing for Hi-Fi World and went on to edit the magazine for nearly a decade. He was then made Editor of Hi-Fi Choice and continued to freelance for it and Hi-Fi News until becoming StereoNET’s Editor-in-Chief.
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