Chord SPA 1424 Mono Power Amplifier

Although the name sounds new to most American readers, UK-based Chord Electronics has been around for more than 15 years, and are well-established in the UK, Europe and Asia (and has had a toehold in the US in select studios such as The Hit Factory, Skywalker Sound and Sony Music Studios).
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Although the name sounds new to most American readers, UK-based Chord Electronics has been around for more than 15 years, and are well-established in the UK, Europe and Asia (and has had a toehold in the US in select studios such as The Hit Factory, Skywalker Sound and Sony Music Studios). The product range includes preamps and power amplifiers, integrated amps, a CD transport, an MC phono stage and a D/A converter. Their line covers the audiophile and home theater enthusiast, with an additional dedicated Professional range designed for studio applications. Although a variety of amps is available, the chosen product for review here is the high current mono amplifier SPA 1424 ($4,750).
Product PointsApplications: Studio, post production

Key Features: Single-channel; Class A; cooling fan; mil-spec components

Price: $4,750

Contact: Chord Electronics/Independent Audio at 207-773-2424, Web Site.
This is a unique design Ð it is fairly small in size, lightweight, runs at practically room temperature, yet it is very powerful and fast, with very low distortion. The key is that the power supply operates at a higher frequency than the more common power supplies found in giant Class A amps. According to Chord Electronics, the rails of the supply are dynamically coupled, which eliminates any ground loop modulation distortion. This design of the power supply allows for efficient and ample storage of energy, which makes clipping practically impossible. The output chain has no need for any overload sensing devices or fuses that might normally degrade the sound quality. Here's a very technical description of the high frequency design power supply, which I quote from their web site:

"The rectified mains and resulting DC is stored, then chopped using mil-spec MOSFETs, the following HF waveform is passed through a ceramic-cored high-frequency transformer, with the output then being reconstituted within a truly innovative magnetic dynamic coupling system, before final storage in a massive bank of capacitors. This uniquely ties in the positive and negative rails together by a strong magnetic flux."

The result is an amp with a stress-free power supply with vast reserves of readily available energy. Herein lies Chord's solution to the dynasty of very expensive, heavy, large, and very hot running Class A format devices. The SPA series includes six models, both stereo and mono units, ranging from 120 to 480 watts per channel in stereo, and either 350 or 550 watts in the Mono version (all into 8 ohms).


Here are the vitals: 550 watts RMS into 8 ohms, 950 watts RMS into 4 ohms. Weight is a very manageable 40 pounds. The brushed aluminum front panel of this case is both elegant and practical. It has little to speak of in terms of features Ð a power switch with a two color LED (red is stand by, green is on), and a clip LED which lights green showing signal present (greater than 20 mV), and red at 3 dB below clipping. There is also a trim pot for adjusting input gain with a range of up to 27 dB, which can be locked down with a hex screw under the pot. The unit is rackmountable, taking up three rack spaces. The Chord logo appears in a recessed brass plaque that gives the case somewhat of a British Royal Navy look (polished, dignified) Ð not that most people stare at their amps while listening, but I think it is a nice touch.

The rear panel has four 30 Amp, gold plated 4mm output terminals, suitable for biwiring. Each set of posts goes to the amp through separate relays for redundancy. The relays switch on after a 15-second power-up delay to ensure output stability. There is a pair of phase reversible XLR balanced inputs, i.e. one connector is pin 3 hot, and one is pin 2 hot. The twin cooling fans run during the first 15 seconds of start-up, then they shut off. As the amp begins to heat during heavy use, the fans will come on and run silently for a period of time. This is the result of a recent modification Ð the fans used to run all the time at about 10% of full speed. Since many studios place the amps as close to the speakers as possible, the design was changed to a totally silent running operation. The fans are fitted on each side of the unit.

The output stage utilizes thirty-two dual-die MOSFETs, developed specially for Chord. John Franks, CEO and chief engineer at Chord Electronics describes the MOSFETs:

"The amplifier sections are also highly sophisticated designs that make the most of the best high-voltage, lateral structure MOSFETs available. The result is a sliding Class A/B design with all drive circuitry operating in Class A. At usual listening levels most of the music will be reproduced in Class A thus Chord amplifiers combine the subtlety and musicality of a good valve design with the punch and accuracy of 'state of the art' solid state products."

In Use

For the purpose of this review, two of the SPA 1424s were running a pair of B&W Nautilus 802 loudspeakers. Listening sources came from CD, SACD, 1/2-inch 30 ips analog, and 96 kHz multitrack (Pyramix) and DSD multitrack (Sonoma). The Chord sound is not that of a typical MOSFET design Ð it is very transparent, open, and resolved, with exceptionally fast transient response. The low end is very extended, but also very clear. Mids yield accurate imaging without aggression, and the high frequency response is extended without being hyped. I swapped out the amps with a Cello Duet (Mark Levinson design), and was very surprised with the outcome Ð the Chord had more resolution, but with the equivalent power-driving ability. I normally listen at about 75 to 80 dB, but I did check the amps at much higher levels. While the Cello became slightly aggressive with the Nautilus 802 at loud volumes, the Chord maintained its smoothness in the upper mids and even, punchy bass response. Even the air in the high end remained intact. I auditioned various program material from pop, jazz, and classical disciplines, some of which I had recorded and/or mixed myself. Similar results were obtained with all program types Ð very impressive, as this is not an easy feat (this versatility is due in part to the loudspeaker of course, and the two seem to be a very good match) .

Having compared amps, I then swapped out the speakers for a pair of ProAc Studio 100 closefields. Again, very impressive results for a small speaker, but not surprising since a small loudspeaker puts less demand on the amplifier. The Chord amps are great for location recording because of their light weight and rackmount faceplate.

I also auditioned some SACD surround program with three SPA 1424 Mono amps powering the L/C/R speakers, and a Stereo SPA 1232 amp on the rears (all five B&W Nautilus 802s, with a Genelec 1092 Sub). This particular trial emphasized the amp's ability to accurately reproduce low level detail such as reverb and subtle spatial cues. Having the high resolution of the Chord amps in surround was very satisfying.


I found the Chord 1424 to be an all round workhorse for studio applications such as mixing and mastering, and that it also holds its own in the audiophile world of high end home systems. The amplifier seems to have the perfect balance of honesty and flattery in its character Ð I have appreciated its truthfulness and accuracy while mixing, and also the sheer enjoyment of listening to final product. Along with mixing desks and loudspeakers we must be sure to include amplifiers on the list of exceptional audio equipment coming out of England.