Integrated Amp Reviews

Once upon a time, reviews of Musical Fidelity components frequently filled pages in Stereophile. But in all my years covering audio shows, I can't recall blogging about any of the company's products, not even once. So, when my editor offered a review of the new M8xi ($6490), a hefty 101lb dual-mono integrated amplifier that includes a DAC, I seized the opportunity to fill a black hole in my consciousness. (Kindly cast aside thoughts that it would take more than a hunk of audio equipment to fill the black hole in my brain.) As long as I didn't break my back lifting the M8xi, solo, to the top shelf of my rack—for this I humbly beg assistance from spouses, neighbors, and friends—new vistas were in store.

I had no way of knowing if the M8xi would lead me down the Yellow Brick Road to Oz, but I did know that, power-wise, it would have no trouble propelling my Wilson Alexia 2 loudspeakers in that direction: The M8xi is specified to output a whopping 870W into 4 ohms. It arrived at the perfect time to compare its amplification section with my reference D'Agostino Progression monoblocks ($38,000/pair), which are specified to output 1000W into the same 4 ohms, and to compare its DAC with both my reference dCS Rossini DACClock combo ($23,999 + $7499) and the Weiss DAC502 ($9850). Given that the price differences among these products are wider than the fabled parting of the Red Sea that allowed the people of Israel to escape from Egypt, the prospect of using the money saved to buy a few coveted yellow bricks proved so tempting that I gleefully mixed mythologies as I prepared myself to ignore the possible consequences of my metaphorical sins.

When I mentioned the Progressions to Austria-based Musical Fidelity President and CEO Heinz Lichtenegger during our cellular exchange, he set the stage for the comparison I had in mind. "I have the D'Agostino Momentums here. Dan is a very good friend of mine. I don't want to compete with Dan's products, which are in a different price range. We call the Musical Fidelity brand 'affordable high end,' and our Pro-Ject brand 'affordable hi-fi stereo.' Musical Fidelity prices will never rise to $20k; it's not the brand for it. We have to know what we are and want to maintain our tradition."

Musical Fidelity's tradition is certainly ambitious. "To me, Musical Fidelity was always the best product to find your way into high-end audio without spending crazy money," Lichtenegger continued. "It has very nice musicality, which it made a priority. Our design philosophy includes minimal feedback to ensure that we don't overdamp—we want to keep the life of the sound—and huge dynamic possibilities. The idea is to have huge, huge power to drive any speaker you wish while avoiding the pitfall of most high-power amplifiers that produce a hard, unmusical sound at low volume levels. You can use our [products] in a normal environment where you can't make head-banging sound."

Lichtenegger was equally forthright about the M8xi's limitations. "There may be a preamplifier in the M8xi, but mainly it is two mono amplifiers. It's not so far away from the Progression, but the Progression is for sure better and has more components inside. But any good amplifier with a radical design such as ours should have the same channel separation and the same power as two monos." That kind of talk makes me eager to see John Atkinson's measurements report.

Lichtenegger entered the business almost 40 years ago as a small retailer who wanted to sell hi-fi to his friends without having to jack up prices because of import fees. Soon, he began to sell and distribute Triangle loudspeakers from France and Musical Fidelity from the UK. In 1991, he founded Pro-Ject.

As he became one of Musical Fidelity's largest European distributors, Lichtenegger developed a friendship with company founder Antony Michaelson. Two years ago, when Michaelson opted to retire, Lichtenegger took over the company with the promise to rebuild the line while maintaining the Musical Fidelity tradition.

"Antony was never a designer," Lichtenegger said. "He was the idea holder, the man behind the sound whose specialty was electronic and analog design. For 10 years, I'd already been producing his digital and software line using Pro-Ject's digital engineers."

As part of the ownership shift, Lichtenegger welcomed the original designer of the company's analog layouts, Musical Fidelity's technical director and main engineer, Simon Quarry. David Popeck, who was involved in designing the digital side of the M8xi, also remained with the company and focuses mainly on software design for the Encore line of streaming music systems.

"Our philosophy involves both circuitry and components. You can take the best circuitry and components, put them together, and build something that measures really well but doesn't sound good. Antony knew how to balance circuitry with components. It took us two years to fine-tune the M8xi to its current level, which required finding the correct placement for components. The layout of every wire and transistor has a huge impact on distortion and sound. You don't just put something in and solder it and consider it done; sonic balance is only achieved by play, play, play.

It's very difficult to combine a certain warmth and sweetness with musicality in solid-state. Antony, whose first products were tube amplifiers, worked to get tube sound from solid-state amplifiers that could power big speakers. I'm very happy that I still have Simon and Antony on board to fine-tune the circuitry and components that create the famous Musical Fidelity sound."

The M8xi's DAC handles PCM up to 24/192 and does neither DSD nor MQA. More characteristic forthrightness from Lichtenegger: "We decided to put a DAC inside the M-series because some people want one without adding an extra box. But we have to say that it's not possible to include a proper-sounding DAC in an amplifier with a design that requires so much current and power. ... So, if you want a DAC that performs on the same level as the amplifier, you need a separate DAC."

Lichtenegger invited me to submit queries for Quarry, the M8xi's main engineer. Given my own fortes, I decided to limit my questions to basic information about the amp and preamp design. Having frequently read claims that a particular class-AB amplifier may produce its first 30W in class-A before switching over to class-B, I asked how the M8xi operates.

"Standing current in the M8xi is set so that 0.25W into 8 ohms would be within class-A region," Quarry wrote. "This is the point at which the audio transistors ... slide into zero glitching (crossover distortion) at the crossover point. Increasing the standing current beyond this point makes distortion rise again.

Quarry corrected my use of the phrase "switching over."

"Everyone says 'switches to class-B.' This is incorrect. The transistor supplying the current simply increases the output current into the speaker. Even the transistor that is 'not in use' on each alternate half cycle is not switched off—it is still drawing the standing current. So, no 'switching' is really occurring anywhere.

"The M8xi has a large power capacitor next to each of the output devices, separate from the main supply reservoir capacitors. This allows a huge amount of energy to be available to draw very quickly and close to the amplifier circuits. This in turn gives great output drive capability and much-improved transient response and dynamics, particularly into lower-impedance speakers.

"The preamplifier features all-analogue circuitry with a laser-trimmed, digitally controlled volume control. This allows 0.5dB steps matched to within less than 0.1dB between channels, from bottom to top [of the] volume range. So, no more increasing mismatch at the bottom end of the scale! The preamp section is set up so [that] no op-amp outputs more than its standing current, thus maintaining 'class-A operation' at all input levels. Pre-outputs would be class-A for next-stage inputs over 5k ohm impedance—nearly all are well above this; 10k ohm is standard lowest—but still keep distortion low [into loads below] below 600 ohms."

Musical Fidelity's Lubor J. Grigorescu subsequently wrote that the M8xi's analog volume control, which is digitally controlled by the front-panel knob, resides on a T1 PGA2320 chip. The company claims "channel and frequency matching less than 0.1dB, even at lower levels, which are normally problematic for usual mechanical pot." The preamp is separately powered to prevent high-current leakage from the mono amplifiers. The DAC and sample-rate–conversion parts are fed by a filtered 5V power supply.

Romping around the playground
When I first set eyes on the massive M8xi's front panel, with its two oversized knobs glaring at me from either side of an easily readable, dimmable input/volume display, the thought "This is a man's amp" came to mind. I admonished myself for such sexist terminology and asked the husband what he thought.

"Everything you've got looks like men's gear," he said rather dismissively. Well, at least he didn't call my components "boys' toys."

The back panel includes two sets of speaker outputs, two sets of balanced inputs, and one set of balanced line-level outputs. Unbalanced line-level connections (RCA) include four analog inputs (labeled CD, tuner, AUX1, and AUX2/ HT; there's a switch to turn the latter into a home-theater bypass) and two analog outputs (labeled LINE and PRE; the former is fixed while the latter is variable). Digital inputs include USB, S/PDIF optical (2), and RCA (2). There are also one RCA and one TosLink digital out, Trigger in and out, and a 20A-capable IEC receptor.