For over a year-and-a-half, I have been on an odyssey, listening to different tube-based amplifiers. I have heard some of the highest-regarded parallel, push/pull, and single-ended designs based on 211, 300B, and 845 power tubes on the market today. During this experience, I realized that I was finding it more and more difficult to go back to my reference solid state amplifiers. Even though these amplifiers are terrific and rank with some of the best solid state designs in their own right, they could not match two key sonic traits of very high-end tube designs. First, the density of tone, timbres, and color can sound ever so slightly washed-out. For example, a brass instrument would not have that gorgeous "brassy" sound you'd hear in a live setting. Secondly, individual players lack what I refer to as image density, palpability, or a sense of air around each instrument on the soundstage. Tubes do have their allure, but they also have their well-stated drawbacks, including maintenance, heat, warm-up and so on.
Determined and motivated, I began to search for a pure Class A solid state amplifier that might address these shortcomings and still provide what great solid-state Class A amplifiers have to offer: transparency/details, a grainless liquidity, and dynamic impact. The highly regarded, 30-year-old, Britain-based company Musical Fidelity had in its reference-level line an amplifier called the AMS50, which retails for $13,999. It is based on a pure Class A design. Unlike many solid state amplifiers that produce pure class A in their first few watts and then cross over into a Class A/B bias, the AMS50 stays in pure Class A. The AMS50 has 50 watts into eight ohms and 100 watts into four ohms throughout its total power rating. Don't let the power rating of 100 watts into four ohms fool you into thinking that the AMS50 would not do well at driving low-efficiency speakers. Its peak-to-peak current rating is a whopping 100 amps. The AMS50 has enough current to drive virtually any speaker on today's market with control and ease. The amp is based on twin high-current amplifier sections in a bridged configuration with a tremendously stiff power supply.
The Musical Fidelity AMS50 amplifier was meticulously encased for shipping and arrived in a three-layer carton with protective foam inserts. With its impressively hefty 132-pound weight and dimensions of 19 inches wide by 18 inches deep by 12 inches high, it became a two-person job to unpack it and place it on the amp rack. You should not attempt to put the AMS50 into a standard gear rack or enclosed cabinet for two reasons. Because of its sheer weight and size, it would not fit on any standard racks or in enclosed cabinets. Secondly, because it is a pure Class A design, this amp produces tremendous amounts of heat; therefore, it needs to be completely open for ample and necessary ventilation.
The AMS50 is a beautiful-looking amplifier that comes in matte gray finish with a black centerpiece. The front plate has a power switch button in the middle and two sets of discrete LEDs showing power/standby, operating status, and temperature status. Behind are two pairs of dual speaker binding posts, two pairs of either XLR or RCA inputs, a selection switch for the inputs, an on/off power switch and, finally, the IEC socket.
During its stay in my reference system, the AMS50 powered four different sets of speakers, including the Lawrence Audio Cello
, the Birch Acoustic Raven
, and the Vapor Audio Stiff Breeze
. Additionally, it was driven by three different preamps (Concert Fidelity CF-080, Raven Audio Shadow, and Burson Soloist) and three different digital front ends (Concert Fidelity DAC-040, Woo Audio WDS-1, and Grace Design M902.
The AMS50 was so transparent, with no apparent noise floor, that any changes in upstream gear could easily be heard by both the trained and untrained ear. I would not recommend leaving it on all the time, due to an increase in your electrical bill. Class A amps basically have two modes of operation: all-on or completely off. That's the beauty of the design and Energy Star ratings be damned, because this kind of amp just drinks power from the wall. It's the nature of the beast. The good news is that this amp warms up to optimal performance pretty fast - 10, maybe 15 minutes, it's ready to rock.
Click over to Page Two for The Performance (including music videos), The Downside and The Conclusion