Pre/Power Amplifiers

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Ken Kessler and Paul Miller  |  Jan 15, 2012
You want big valves? Really big? NAT has cooked up a monoblock with a mortadella-fat QB 5/1750 tetrode, and a preamp worthy of the honour. Enter Utopia and Transmitter Any reservations I may have had about Eastern European amplifiers were put to rest by the NAT Se1 MkII reviewed in Aug ’10. It was time, I thought, to stop treating the former Communist Bloc as if it were the equivalent of China circa 1993. If anything, countries like Serbia, Bulgaria and others under the grip of the Commies for a half-century had a much better chance at conquering the high-end than the Chinese did, because they had greater hands-on experience.
Steve Harris and Paul Miller  |  Dec 01, 2011
The original ‘Electro’ was a milestone design, even if it was not quite what it seemed. Does this legendary 25W pre/power combination really live up to its cult status? Back in 1966, a Norwegian pop band called Mojo Blues topped the local charts with their first single, a cover of The Stones’ ‘Lady Jane’. They followed up with more hits, but eventually disbanded. By 1972, Mojo Blues’ frontman Per ‘Abe’ Abrahamsen had started Electrocompaniet as a small business, importing cheap Bulgarian speakers and building basic PA electronics.
Ed Selley  |  Nov 20, 2011
Anniversary edition of the Reference five splits into two boxes for improved performance Released to commemorate the 40th anniversary of the company’s Reference preamp, the Anniversary Ref 5 promises to address the few solutions not available in its recently unveiled single-chassis version. This two-chassis model sees the valve power supply relegated to a box of its own and, being a true dual-mono layout, two fat umbilical cords connect it to the chassis. Under the lid can be found an all-valve, zero feedback, pure Class A circuit employing four 6H30 triodes per channel, again dual-mono, while mounted on the bottom of the main board are four massive custom Teflon coupling capacitors, weighing around a kilo apiece. Each valve is fitted with a now-familiar damping ring; the main circuitry is fitted to a large mother board; daughter boards deal with the front panel and the socketry.
Ed Selley  |  Nov 20, 2011
The appearance might be retro but the performance is right up to date Deliciously retro in appearance, Icon’s huge flagship power amps began life in 2009 as the MB845s: so-called because they utilise a pair of the mighty 845 direct heated triodes. Still in production, the MB845s cost just half the price of these latest MkII versions, designer David Shaw significantly reworking an original design rated at 65W and ‘repositioning’ the model as a more prestigious high-end product. The MkII also employs an improved high current driver circuit employing two 6SN7 dual-triodes. High power output from the two 845 valves requires a truly massive power supply design too, so the MkII’s mains transformer has grown in size compared with that of the original MB845.
Ed Selley  |  Nov 20, 2011
The latest Levinson product is a consummate music maker New electronics bearing the Mark Levinson badge don’t appear too often. When they do, the world of high-end audio expects them to be exemplary. In producing its first switching amplifier, the ML design team has been able to scale things down to (almost) manageable proportions. The benefits of Class D amplifiers include increased efficiency enabling greater power output while requiring less heat dissipation in smaller, lighter and more affordable packages.
Ed Selley  |  Nov 20, 2011
The largest AMS amplifier is a true giant in all senses of the word You can read all the specs, but nothing can quite prepare you for the arrival of Musical Fidelity’s AMS100. It stands over a foot tall, a foot-and-a-half wide, and by the time it’s plugged in and connected well over three-foot deep. The circuit is a hybrid between that of the company’s smaller AMS50 and range-topping Titan. This new unit has the same topology as the Titan, but is Class A.
Paul Miller  |  Nov 20, 2011
Dan D'Agostino returns with a product half amplifier, half sculpture, all genius With his new company’s first product, the Momentum Monoblock Power Amplifier, Dan D’Agostino hopes to re-write the rules of solid-state amplifier design. Most notable is a concern for green issues, by addressing the amp’s power consumption when not in use. It’s a claimed 1W – not bad for a 300W amp that thinks it’s a kilowatt. Running in Class AB, and merely warm to the touch after a long session reflects a cooling system which provides much of the Momentum’s visual presence: solidcopper bars (venturis) that form the amplifier’s flanks.
Ed Selley  |  Nov 19, 2011
A sumptuous Italian pairing with sonics to match the exquisite looks You have to hand it to Italian designers: they sure do know how to make a statement. These mightily imposing valve power amplifiers dubbed 845 Monoblock and accompanying PhL-5 preamplifier simply ooze luxury. At £9995 per pair, the monoblock employs twin 845 tubes in parallel single-ended pure Class A mode, with two 6SN7 dual-triodes used as drivers and, as you might expect, zero negative feedback. The transformers are hand-wound with litz wire to avoid the use of solder and are ‘potted’ in a mix of resin and gravel to provide mass damping.
Ed Selley  |  Nov 17, 2011
The first solid-state Quad remains a classic of the genre Exemplifying all that was admirable in British hi-fi, the 33 preamp (£43) and 303 power amp (£55) were Quad’s first commercial solid-state offerings, the company having waited for the new-fangled transistor to settle down before embracing it in 1967. It was in many ways ‘a solid-state Quad 22’. Any previous customer would have immediately recognised the control locations, the flushmounted rotaries, the balance control under the volume control, the press buttons that also offered Quad’s unique, fully cancellable filter and tone controls and RIAA selectors. In size, the 303 and the Quad II power amps were nearly interchangeable.
Ed Selley  |  Nov 01, 2011
A very substantial design indeed with impressive performance to match Owned by Paradigm, Canada’s largest speaker manufacturer, the Anthem electronics brand is renowned for its high value AV offerings. While its ‘bread and butter’ receivers are made in China, its premium Statement components are built entirely in-house, this massive P2 power amp sharing the same case as the company’s five-channel P5 [see HFN June ’09] that draws so much current it needs two power cords. Just as in the P5, each channel of the P2 is built as a monoblock on its own PCB with substantial heatsinks fitted with thermal sensors to monitor operating temperature. And each channel has its own toroidal transformer and regulated power supply.
Ed Selley  |  Nov 01, 2011
A very potent performer considering the accessible price In its most recent 15-Series line-up Rotel entered the brave new world of efficient Class D amplification with some of its models. It promotes them more for home cinema and custom installation duties rather than ‘pure audio’ systems, however. For high fidelity music reproduction Rotel still prefers to focus on tried-and-tested Class A/B solid-state designs, in which it has a fine pedigree. Cosmetically, the RB-1552 is identical to the more powerful ’1582, only the chassis’ reduced depth and lighter weight suggesting a smaller power rating here.
Ed Selley  |  Nov 01, 2011
The entry level Belles power amp has some charming characteristics This midi-sized power amplifier from American designer Dave Belles’ Power Modules company naturally has a similarly compact preamplifier to partner it, dubbed Soloist 3; there’s also an MM/MC phono stage. This is ideal for enthusiasts desiring a separates combo that requires precious little space. There are no frills here – while better known for its high-end amplifiers, the Soloist components are Belles’ entry-level models. Build quality is staid and workmanlike, without the gloss of more costly designs.
Ed Selley  |  Nov 01, 2011
A robust design that produces a sound noticeably free of adornment Famous for its uncoloured, bomb-proof monitors beloved of recording engineers the world over, ATC builds not just speaker drive units but also the amplifier power packs for its active speakers in true artisan fashion in its Gloucestershire workshops, populating circuit boards entirely by hand. Similarly, the company’s standalone pre- and power amps are individually hand crafted, only the metal casework is bought in from an external supplier. As mentioned on page 43, we reviewed the P1 and its partnering CA2 Mk2 preamp in March ’10. Since then the power amp has unfortunately crept up in price by some £250.
Ed Selley  |  Nov 01, 2011
The Baby Bryston has many of the behavioural traits of the brand and some likeable sonic qualities Based a couple of hours’ drive north-east of Toronto, Bryston builds its audio components fully in-house. Next year will see the company celebrate 50 years since its initial foundation as a manufacturer of blood analysis equipment. It made its first amplifier in 1973 and progressed into the audio business soon thereafter. Luton’s Professional Monitor Company (PMC loudspeakers) has been Bryston’s UK distributor since the early 1990s – and naturally it’s Bryston amplifier modules that power PMC active monitors.
Paul Miller  |  Oct 01, 2011
Better known for multichannel, the A21 demonstrates that Parasound knows a thing or two about stereo too As with Canada’s Anthem electronics, San Francisco’s Parasound components are often found powering luxurious multichannel ‘home theatre’ systems. Unlike Anthem, however, Parasound does make pure audio (as well as AV) preamps to partner some of its power amps, especially its two-channel models. Designed in the US by John Curl, a veteran whose CV includes classic Mark Levinson and Vendetta designs in years gone by, Parasound’s amps are outsourced to Taiwan for manufacture – which might explain the keen pricing. This A21 power amp from the flagship Halo range suggests a lot for the money, weighing 27kg and resplendent in classy casework.

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