The NAD 3020 is a stereo integrated amplifier by NAD Electronics, it is an important component in the history of high fidelity audio. Launched in 1978, this product delivered a good quality sound, while being affordable. It acquired a reputation as a well known and popular audiophile amplifier. By 1998, the NAD 3020 had become the best-selling audio amplifier in history.
History Launched in 1978 when the principal preoccupation of hi-fi manufacturers was power output, the sub-£80 (US$135) low-powered solid state amplifier, created and marketed by a then little-known manufacturer, gained a reputation for excellent sound quality and exceptional value. Stereophile magazine called the NAD 3020 "ridiculously inexpensive". It was the first integrated amplifier built with convincing ability to drive difficult loudspeaker loads, and a sound quality that far exceeded other integrated amplifiers at its price point for the time. In an era when the NAD's rated power output of 20 watts per channel continuous into 8 ohms was considered anaemic, the manufacturer claimed it could deliver much stronger power output into lower impedances under dynamic conditions (music or peak power output). Indeed, it is capable of delivering 40 watts into 8 ohm, 58 watts into 4 ohm, and 72 watts into 2 ohm loads for a limited time if pushed. The amplifier's main appeal was its inherent musicality, its ability to drive difficult speaker loads, and to allow audiophile grade source components to excel. Launching the product in the US at the Consumer Electronics Show, the company wired up a battery of loudspeakers in a way which presented an impedance of 1.1 ohm, and the amplifier experienced no problems. Similarly, at its London launch, NAD successfully demonstrated it driving the Linn Isobarik, whose impedance characteristics are known to be very challenging for amplifiers. It was the best-known and best-selling amplifier in the annals of hi-fi. The NAD 3020 revolutionised the amplifier segment of the hi-fi industry.
Design principles Bjørn Erik Edvardsen, NAD's director of advanced development, set out to create an "inexpensive amplifier ... easily capable of driving the very best loudspeakers". NAD eschewed the laboratory test equipment thinking, which was prevalent at the time, and instead aimed to make their amplifiers capable of properly driving "real loudspeakers" under realistic conditions. This paradigm shift gave rise to an amplifier that cost less and sounded better. NAD was able to achieve a low cost base by foreign manufacture. The company designed the product in Europe and had it produced in factories in Taiwan – it was one of the first manufacturers to de-localise production to Asia. The design, and models following it, included "soft-clipping circuitry" that protects against over-driven signals, connections that allow splitting of the power amplifier section from the preamplifier, and "Full Disclosure" power ratings measuring output power under real-world loads.
Audio circuitry The NAD 3020 has four inputs that can be switched via the front panel – Aux, Tuner, Phono, Tape. The manufacturer claims the phono input, which can also be used with high-output moving coil cartridges, contains a 6-transistor circuit "engineered for extremely low noise and nearly distortion-free performance". Reviewers note the pre-amplifier's "decent moving-magnet phono stage". The amplifier is bandwidth-limited, incorporating infrasonic and ultrasonic filters to supposedly reduce the effects of non-musical signals such as acoustic feedback, disc warps and electromagnetic interference on the musical signals. The amplifier has bass and treble tone controls which, according to the manufacturer, are "tailored for musically effective response in the high and low frequencies without altering the critical mid-range tonal balance". A loudness switch – de rigueur in that era – boosts upper and lower frequencies; a "mute" switch reduces volume by 20 dB for low-level listening. There is also a headphone socket mounted onto the front panel. According to the manufacturer, the NAD 3020 is a high voltage design that uses the same large powerful output transistors (2N3055 and MJ2955) that "other manufacturers employ in their '60-watt' amplifiers", enabling the amplifier to deliver power headroom for musical transients. The "Soft Clipping" circuitry is intended to limit the output voltage so that the transistors do not distort when driven beyond its rated power. The innovative split of pre- and power-amplifier sections allows the use of the pre-amp stage to drive multiple power amplifiers in parallel, or use long signal cables to connect to remote power amplifiers or powered speakers. This facility became hugely popular with audiophiles, who would seek to isolate this "remarkably fine-sounding preamp section", to use with one or more external power amplifiers.
Power source The amplifier has what the manufacturer calls a "dual-mode power supply", where the output stage is only loosely regulated, so it is free to supply the high voltages needed for musical transients and the large currents at lower voltages needed for driving low-impedance loads in the power amplifier circuitry. The design also incorporates a separate regulated power supply circuit, fed from a secondary winding on the transformer, dedicated to the pre-amplifier and tone control stages. It is thus claimed that intermodulation distortion and blurring of the stereo image due to power supply functioning cannot occur.
Styling The styling of the NAD 3020 resembled that of other budget amplifiers of the time, and it was available in charcoal grey or a much rarer silver. Stereophile commented that it was "inexpensive and looked it".
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