Chord Electronics SPM 1050 amplifier
Chord Electronics SPM 1050 amplifier


The SPM 1050 amplifier is a more affordable version of Chord's popular SPM 1200E stereo amplifier with both the sound quality and the power to comfortably drive most full range speakers. The nature of the output devices, power supply, energy storage management, and clever design are trickled down with additional cost savings on the casework. Several enhancements have been made in this latest design that are clear audible improvements over it's predecessor and the new engineering further improves reliability and extends life span. Power available is 200 Watts into 8 Ohms rising to 350 Watts into 4 Ohms with distorion less than 0.05% at 10kHz. As with all Chord products, to get state of the art performance, proprietory devices and methods are used because readily available ones do not meet the requirements for the best possible sound.

Output devices and power supply

Eight 150 Watt lateral dual-die MOSFET devices (made especially for Chord by a leading UK fabrication company previously in the aerospace sector) are used per channel. Each contains two silicon chips in parallel within a metal TO3 package giving significantly better thermal matching and consistent performance over a wider operating temperature range with excellent conductivity to the heat sinks. To avoid the glare that some MOSFETs introduce from hard switching ripple resonance, Chord's proprietory MOSFETs have been specifically designed with soft turn on turn off characteristics similar to tubes. The transition zone between "on and off" with these custom MOSFET devices is still much faster than most Bipolar transistors which are rather sluggish. The MOSFETs are on ± 80 volt supply rails - significantly higher than most amplifiers - helping to preserve the full range of dynamics in the signal without being scaled down.

The very generous 2 kilowatt switched mode power supply deployed in the SPM 1050 amplifier is a fifth generation design and is one of John Franks's (founder of Chord) specialities. There is no denying the technical superiority of this approach and Chord's unique versions are proven throughly reliable. In conventional designs, power from a transformer cycling at 100 or 120 times a second is rectified and supplies a bank of storage capacitors. With power supplied in cycles of this frequency, the time it takes for the storage capacitors to recharge is not fast enough for rapidly changing, power demanding, musical transient events. The size of this energy storage tank is of limited advantage, since once depleted, it is the time it takes to recharge (principally the size of the supply feed) that counts.

The energy "pipe" supplying the capacitor storage bank from Chord's switched mode supply is huge. It is ingenious because it is done in two basic stages. First the incoming mains is rectified to DC of several hundred volts which is initially stored in it's own bank of storage capacitors. AC is then regenerated, but this time at a very high frequency (80-120 kHz), by high switching MOSFETs and fed to a very specialized small ceramic cored transformer (this is where the weight saving occurs) and then rectified a second time before being passed onto the main storage bank of capacitors. Because the final bank is supplied at 80kHz cycles, the alternating current spends less time crossing over the zero voltage axis, and "turbo replenishing" takes place. Full energy is readily available for the next musical event because it is never completely depleted. More importantly continually available power preserves the complex time varying harmonic structures present in musical instruments such as pianos.

This approach to power is far superior to conventional huge and heavy toroidal linear power supplies which introduce noise, heat dissipation, and unwanted hystersis effects, and simply results in a better sounding amplifier as well as a more efficient one.

Further Ingenuity

The postive and negative power supply rails in the SPM 1050 amplifier are strongly coupled by magnetic flux so that if a large transient occurs on one rail, power is drawn from the other rail. This gyroscopic-like circuit automatically compensates and keeps the positive and negative power rails in perfect equilibrium with each other and the mid ground point. In effect this gives the power supply greater headroom and removes the need for high frequency limiting devices on the input stage (high frequency components in transients are the primary cause of instability and oscillation in most amplifier designs). All the subsequence amplifer gain stages are wide bandwidth with uniform even harmonics and fast rise times for accurate timing and clipping is abolished.

Distortion factors are low since the SPM 1050 amplifier operates in class A mode during most normal use but switches into class B mode during very demanding situations (sliding bias class A/B design) To protect the amplifier and speakers in the event of a fault condition such as short circuit or a dc offset, the SPM 1050 amplifier uses Chord's output protection technology that relies on sensing minute flux density differences between the power supply rails rather than imposing sound-degrading components that other amplifiers use.

High build quality

Internally, only very reliable industrial grade components designed to last at least 20 years are used. Externally, top quality casing, sockets, knobs are used, markings are laser-etched, and it is difficult to see any aging years and years after purchase of any Chord Electronics product.


The SPM 1050 amplifier has the power to drive all but the most difficult floorstanding speaker loads. It conveys the essence of Chord amplifiers in having a sense of ease in power delivery that is also very natural, precise, transparent and fluid sounding. Bass has a great deal of poise and the amplifier can react quickly giving a great sense of movement and propulsion. The midrange is very, very, clean revealing all textures in the music against a black background (Signal to noise >103dB, 'A' weighted two thirds power). The treble is open, smooth and well extended. The timing envelope has realistic attack and decay so, together with timbral neutrality and unrestrained dynamics, the overall musical content is accurately portrayed with neither embelishment nor restraint. The SPM 1050 is the bargain in the Chord range of amplifiers and has the buld and sound quality that easily outperforms others in it's price. It has received The Absolute Sound 2009 'Editors Choice' award and is a What HiFi '5 star' component.

U.S Retail Price: $8,000 including integra legs