Pre/Power Amplifiers

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Hi-Fi News Staff  |  Nov 13, 2014
McIntosh’s original MC275 featured as an ‘Audio Milestone’ [HFN Dec ’10], but what’s reviewed here is the current production version of this most famous power amplifier. It’s the same as the 2011 Anniversary Edition but with stainless steel rather than a gold chassis. Its most spectacular outward feature, described in staid McIntosh tech-speak as ‘small tube illumination for amplifier status operation’, comprises LEDs indicating status or output tube failure. This is a part of a protection circuit system which will also shut the amp down if speaker wires are shorted or there is a gross impedance mismatch.
Hi-Fi News Staff  |  Nov 13, 2014
Enter Musical Fidelity’s latest ultra-high-power creation, described as ‘a true heir to the [2008] Titan, delivering near-identical sound’. It’s a monoblock design that’s considerably more bank-balance friendly, rated at 700W/8ohm, although this transpired to be conservative. It is part of a new series of high-end components, also including the M8PRE preamplifier. The sturdy casework has a finely-textured black finish and thick aluminium fascias while the M8700m’s heatsinks are smoothly finished.
Hi-Fi News Staff  |  Nov 13, 2014
On seeing Siltech’s pre/power combo you might think it incorporates a separate power supply. In fact, this unusual design splits the power amplifier into separate interstage (voltage gain) and current amplifier sections. The combo’s C1 tube preamplifier (pictured) features a rechargeable battery power supply as does the V1 voltage stage of the two-box power amplifier. Of course, running the complete V1/P1 amplifier from a battery would be wholly impractical, so the P1 is mains powered.
Hi-Fi News Staff  |  Nov 13, 2014
At the heart of Simaudio’s 380D DAC/preamp is its M-AJiC32 processing (Moon Asynchronous Jitter Control in 32-bit mode) and at the core of this is an eight-channel ES9016S Sabre DAC from ESS. Simaudio claims to have further improved jitter performance with its own ‘Alpha Clocking System’. The 380D has separate power supplies, each with a toroidal transformer and 11 stages of voltage regulation, for its digital and analogue sections. The analogue stage is a fully differential circuit and balanced XLR connections are strongly recommended, although RCAs are also provided.
Hi-Fi News Staff  |  Nov 11, 2014
The Virgo preamplifier and Centaur monoblocks reviewed here are models from Constellation’s ‘economy’ Performance range, yet total £72,500. As for Reference prices, we shudder to think… While a pretty enough design, the Virgo is rather anodyne, its greyness John Major-like. A plain-Jane outboard power supply feeds it via two umbilical cables, connecting at the back where you find rows of both XLRs and phono sockets for every input and output – four sources, two sets of outputs and RS232 and USB inputs for networks and firmware upgrades. At the front, the central panel’s 432x230-pixel screen is flanked by rotaries for balance and volume, while other operations are accessed through menus activated by a row of buttons under the display panel.
John Bamford and Paul Miller  |  Jan 15, 2012
New to the British hi-fi scene, this exquisitely formed pre/power amp combo is highly compact thanks to the use of Class D modules and switched mode power supplies Once you’ve got the hi-fi bug it seems it’s impossible to shake it off. Certainly this is the case for John Young, who has recently launched a new electronics marque, Acoustic Imagery, based in Warminster. Acoustic Imagery’s first products are these D400M Class D monoblock power amplifiers and a partnering active preamp called, simply, the Pre Amplifier. With a sharp eye, as ever, on the latest developments on the hi-fi scene, HFN has secured the first samples for a world exclusive test.
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.

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