Pre/Power Amplifiers

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Hi-Fi News Staff  |  Jan 20, 2015
Like the hardy perennials of audio horticulture, the standard valve amplifier circuits keep coming up fresh year after every year. And there’s been a new flowering in the family of beam tetrode tubes that started with the venerable KT66. This is the new Tung-Sol KT150, and the first manufacturer to feature it is Icon Audio, showing this tube off to good advantage in its MB90 MkIIm monoblock power amp. Built in Icon’s factory in China but finished and tested in Leicester, the MB90 MkIIm looks solid and handsomely-proportioned.
Hi-Fi News Staff  |  Jan 20, 2015
Krell’s new iBias range is claimed to be more efficient, or less power-hungry, than pure Class A. Paul Miller suggests that iBias is a modern take on the popular sliding bias circuits of the 1980s. So what is the motivation for it? Statements from the company suggest that Krell is doing its part to modernise the high-end, to increase its appeal to audiophiles who are not comfortable with bulky intrusions into their living spaces in a manner acceptable in the past. And yet nothing differentiates the Duo 300, physically, from hundreds of other ball-buster amps.
Hi-Fi News Staff  |  Jan 20, 2015
User-friendly features are a major aspect of the current VTL Signature Series, including the power amp reviewed here. Based on four 6550 output tubes per channel, it has newly-designed output transformers, a larger power supply, and the Signature Series control electronics. When running, the tubes can be seen discreetly glowing through the smoked glass front window. (Our sample was fitted with KT88s, an option that adds £200 to the price.
Hi-Fi News Staff  |  Jan 20, 2015
ModWright’s owner Dan Wright argues that ‘Valves are great voltage amplifiers and solid-state devices are great current amplifiers. ’ Hence the combination here: the top of the range ‘DM’ dual-mono version of the LS 36. 5 preamp, with its separate PS 36. 5 power supply, and the KWA 150 Signature Edition power amplifier.
Hi-Fi News Staff  |  Jan 20, 2015
Each of these three units – preamplifier, two-channel power amp and a power supply to ‘beef up’ the power amp’s performance – is housed in an all-aluminium chassis identical in size and appearance. Pre and power amp are ‘double mono’, the left and right channels both electrically and mechanically separated, with power supply sections, audio circuits and control electronics all in shielded chambers. The new P3000HV preamplifier has a comprehensive functionality that includes an analogue tone processor module to provide bass/treble adjustment, a user-variable ‘loudness’ control to suit your loudspeakers’ sensitivity, and parametric equalisers for tuning your speakers’ bass performance to your listening room. Illuminated touch-sensitive controls allow access to the preamp’s configuration menu, and a headphone amp is built in as well.
Richard Holliss  |  Dec 22, 2014
In Tony Michaelson’s company started with one diminutive but memorable product, called simply ‘The Preamp’. He started by making them on his kitchen table… What made the product so eyecatching was the acrylic front, with the product name illuminated in red. In its original form, The Preamp had an appeal all of its own. It was so tiny, so simple, yet so businesslike.
Hi-Fi News Staff  |  Dec 22, 2014
Furutech’s Alpha Design Lab range includes cables, headphones and earphones, a portable headphone amplifier and stylish system equivalents of the ADL X1 here. This appears to be a portable miniature music centre, offering USB and iDevice functionality, plus a built-in rechargeable battery giving around five hours of operation. Six top-mounted LEDs display sampling frequency, and there’s a front fascia volume control – which sadly proved just a little too easy to accidentally move when out and about. Those on the Number 41 bus will doubtless prefer the ergonomic simplicity of, say, an Arcam rPAC or Cambridge Audio DacMagic XS, which are truly portable devices.
Hi-Fi News Staff  |  Nov 13, 2014
This lavishly-built C600 preamplifier and unusual looking partnering M600 monoblocks [not shown] are TAD Labs’ ‘Reference’ amplifiers. The C600 preamp’s aluminium subchassis is 33mm thick and weighs 15kg alone, designed to resist acoustic vibration and provide a ‘low and stable ground potential’, says the company. Removing the preamp’s top plate reveals its dual mono construction and all-discrete signal path; it’s a fully balanced design. The power supply, with its massive transformer, is a separate ‘hideaway’ unit.
Hi-Fi News Staff  |  Nov 13, 2014
Yes, they’re expensive – but Nagra’s electronic jewels are gloriously timeless and beautifully engineered. The new Jazz preamplifier maintains the compact form factor and familiar brushed aluminium casework synonymous with the marque – it’s a Nagra through-and-through. And Nagra says the preamp’s circuitry – which employs 2x12AX7/ECC83s and 1x12AT7/ECC81 dual-triode valves – has been completely rethought to improve stability and reduce noise to the point where its engineers no longer consider a battery power supply a necessity. The Jazz is powered by a hideaway PSU that delivers DC to the main unit via a cable terminated with a Lemo connector.
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.

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