Ever since I got into sound systems I have been fascinated with amplifiers, integrated ones, pre- and power amplifiers, tubes and transistors. I’ll never forget buying my first real amplifier at the age of 15, it had EL84 tubes in the output stage and the front panel had as many knobs as possible, including tone controls. At that age I was less interested in the sound quality of EL84 tubes and far more interested in all those controls. This amplifier became the start of a endless quest for the best powerhouse to drive a pair of loudspeakers. Another memorable moment was when I visited someone who had some small monitor loudspeakers driven by a Phase Linear 700B power amplifier capable of producing 350 Watts per channel, this proved that a standmount speaker driven by an enormous amount of high quality power can deliver an amazing sound. This was around 1975 when I had upgraded my own amplification to Dynaco transistor pre- and power kits.
Some 30 years later I had tried a stack of amplifiers before I returned to tubes, this time with an Ayon integrated running 300B triodes and delivering 18 Watts a side to a pair of high efficiency Focal floorstanders. It was a highly detailed and very delicate sound, but after a few years I changed my loudspeakers to more demanding monitors and it had to go. At that time I reviewed two very different power amplifiers, one being Manley Labs Snappers with EL34 tubes in Ultra Linear mode while the other amp was a full Class A solid state Pass Labs XA30.5. In combination with an unbalanced preamp and the monitor speakers I chose the Manleys although I also fell deeply in love with Pass Labs. A love that never faded but it would take a long time before Pass and I started a relationship. In the meantime the Manleys were replaced with PrimaLuna monoblocks, still using the EL34 tube that I favoured for their midrange over, for instance, KT-88s. Another loudspeaker change and many reviews later NAD came up with the Master Series M2 full digital amplifier, an amp that suited all my needs at the time, and was capable of keeping a firm grip on the woofers. I used it as a DAC/pre/power amp for digital sources, while an external preamp with tubes was still my favourite for playing records. The M2 delivered the power but nothing else in that mode. Somehow digital amplifiers and I are not a good long term match, not even today with all those shiny ‘pizza boxes’ or small footprint class D designs available on the market. Except for one Japanese product developed by Shirokazu Yazaki (Real Sound) that I recently reviewed for another magazine (note the word ‘recently’ – Ed). Between my first buy at the age of 15 and today I have often returned to either class A or class AB solid state designs. The former for the sheer joy of music and fluidity, the latter for pure muscle power. I found a good compromise with an Audia Flight 50, delivering a healthy 50 Watt per channel into a pair of PMC fact.12 loudspeakers. The only thing that kept my mind busy were the results achieved with more powerful amplifiers that came and went, because they only stayed long enough to write about. Nevertheless none could convince me to change from full class A to class AB until the summer of 2015.
An old flame
Old love never dies and when a Dutch dealer offered a hardly used Pass Labs X250.5 amplifier at a fair price I jumped into my car to collect it. The beauty, or should I say the beast, was carried upstairs with the help of a friendly neighbour and powered up. The current gauge in the centre turned blue and music played. The result was a disappointing absence of deep bass but they said in the shop that it still needed running in because it had been in stock most of the time, so I kept it playing or on standby, although I hardly believed that an eight year old amp would need running in. Then there was far too much bass, but after about a week things turned out right. Bass became deeper and more balanced, high tones rounded nicely, finally listening and comparing could begin. So why does it sound so good? Maybe because of the highly biased class A setting that keeps the X250.5 in class A for the first 15 Watts, with 250 Watts in reserve when you need deep bass, it’s just like enjoying a V8 engine while cruising down the highway. Or when you finally see the gauge move with powerful piano notes. Proving that a PMC fact.12 loves power but doesn’t need too much of it for normal listening levels. After many years my search for the ultimate amplifier seems to have come to an end. It is not only the stereo image that escapes the loudspeakers, nor the deep bass that thunders over the floor, the wide open midrange that cuddles voices or the detailed tender high notes that tinkle into the room, it is the overall presentation that fuels a deep respect for designer Nelson Pass. Music flows, I never get tired, I absorb every note and feel fortunate that I finally own a Pass Labsamp. The X250.5 is possibly/certainly not the best amp on the market, I can think of some names that are competitive, even the newer Pass Point 8 series, but still I love it.
The circuit inside uses the patented SuperSymmetric topology with its high performance, local feedback and only two gain stages: a cascaded differential pair of transistors and a large bank of complementary output followers. The topology that underlies both the X and XA amplifiers. The way it is built almost insures that it will never fail, but if it does Pass Labs’ service is among the best on the market or so I am told. The fact that the dealer offered a three year full warranty on this eight year old amplifier certainly inspires confidence.
I have a second system in my study, it’s where I review small loudspeakers and more affordable products that would be out of place in the ‘big’ system. My reference speaker here is the Harbeth P3ESR, powered by sheer value for money Exposure 3010S2 monoblocks. When I bought the X250.5 I made the mistake of temporarily putting my Audia Flight 50 in this system. It sounded wonderful but like most of us I cannot afford to keep everything. That’s why I sold the Audia to another music lover. But the more I enjoyed the Pass Labs in the living room, the more I regretted selling the Audia class A, but in a way I was as happy as ever with Exposure and accepted that you can’t have it all. Then over the Christmas holiday I spent a lot of time on the internet and when I saw a Pass Labs XA30.5 for sale in Denmark my heart started beating harder and my hands quivered! This was the amplifier that inspired my admiration of Nelson Pass products to begin with, here at last was a chance to make up for the choice of Manley over Pass in 2008. A deal was made and courier service delivered yet another big box, covered with a two year warranty from the shop. The near mint XA30.5 worked flawlessly after I swapped amplifiers, not having a preamp of comparable quality to the new power amp to hand I connected my D/A converter directly to the XA30.5 using XLR cables. After some initial play and 48 hours standby I was in for a surprise. The loudspeakers sang like never before, producing the best performance I’ve heard in the study. There are no drawbacks and no limitations except maybe one, the P3ESR is power hungry and 30 Watts of class A power is sometimes not enough. Luckily the XA30.5 has a peak output of over 60 Watts for playing really loud! But usually this headroom is kept in reserve. From simple CD rips to Q-sound, from 16/44.1 to 24/192 FLAC, WAV or ALAC files, the XA30.5 throws an exceptionally wide, deep and high stage, filled with power as well as the tiniest details. Classical chamber music written by Bach is breath-taking to say the least.
Softly glowing circles
I was asked by the editor to explain where the urge came from to change power amplifiers in both my systems despite being satisfied with what I had and having access to so many products for review. Hopefully what you’ve read so far explains this, owning powerful Nelson Pass amplifiers is a dream come true, they deliver music with a capital M. I guess I have benefited from the fact that big boxes seem no longer fashionable, likewise power hungry amplifiers (a green choice), this must be why prices are dropping on the second hand market. Most people want manageable and good looking small boxes even though they never sound as good in my opinion. Being able to compare results between 30 Watts in class A and 250 Watts in class AB on both PMC and Harbeth loudspeakers, I’d say that in both set-ups I enjoy my music. But the bigger floor standing PMC with its deep reaching bass enjoys the power reserve, while the Harbeth in the smaller room with its focus on the midrange, profits from the slightly better sounding full class A. All I could wish for now are the even more powerful Pass Labs amps from the latest XA Point 8 series, but funds do not permit and nor does my wife. For now the softly glowing blue circles make me very happy.
René van Es