The superb A-S700 Shares many merits with the award winning AS-1000, at less than half the cost.

Yamaha is now one of the only large multinational manufacturers that continues to offer an extensive range of high-quality two-channel amplifiers and if the incredible success of its flagship stereo amplifiers, the AS-2000 and AS-1000 are any indication, the other companies are already ruing the day they decided to exit the two-channel market. The good news for everyone else is that Yamaha is now offering even more of the same, in the shape of the A-S700, at less than half the cost of the award winning AS-1000 (it picked up a ‘Best Product Award 2008–9’ from the European Imaging and Sound Association).

The Equipment

Visually, the A-S700 is almost a clone of the flagship model A-S2000, with what appears to be an identical front-panel layout. However, when you investigate more closely, you will see that although the control locations are identical, different front panel controls are fitted to those locations. If you look at the photograph above, the two switches below the input selector are for ‘CD Direct’ and ‘Pure Direct’, whereas on the A-S2000 these front panel positions are used for phono stage switching (MC/MM) and audio muting. And whereas on the A-S700 the small rotary controls to the right of the headphone socket are for speaker selection (Off, A, B, A+B) and record output switching (Line 1/2/3, CD, Phono, Tuner), the two on the A-S2000 are for headphone volume and record output switching. Take your ruler to the amplifiers and you’ll find that although the A-S700’s front panel is the same width (435mm) and a little higher (151mm), it’s not nearly as deep (the A-S700 is only 382mm deep, compared to the A-S2000’s depth of 465mm). And if you resort to weighing the two amplifiers to differentiate them, you’ll discover that the A-S700 is only half the weight (10.9kg vs. 22.7kg).

Despite this difference in weight (which would seem to indicate at least some economies in the A-S700’s power supply), Yamaha rates the power output of the A-S700 at 90- watts per channel (into 8Ω), which is exactly the same output it specifies for the A-S2000. To skip ahead of myself slightly, the reason Yamaha has been able to pull this trick is found on the rear panel, where a user-adjustable speaker impedance selector must be manually switched between ‘Low’ (for speakers with a nominal impedance rating lower than 6Ω) and ‘High’ (for speakers rated at 6Ω or higher). This switch adjusts the circuitry inside the amplifier for either maximum current drive or maximum voltage, so it’s an ‘either/or’ proposition, whereas the AS2000 doesn’t have a switch, so you get both maximum current and maximum voltage, no matter what the impedance of the speakers you connect.

Activate the ‘Pure Direct’ switch on the AS700 and the signal at the CD input goes through the input selector switch and the volume control but bypasses the tone controls, loudness control and balance control. 22-

Activate the ‘CD Direct Amp’ switch and the signal at the CD input bypasses the input selector as well, so that only the volume control lies between it and the output.

As you have probably realised from my description of the Record Output selector, the AS700 isn’t short of inputs! There are three Line inputs, a CD input, a Tuner input and a Phono input (this last being for a moving magnet phono cartridge only). The input selector is a rotary encoder type, with LEDs indicating the selected input. To the left of the input selector is a rotary loudness contour control. As most readers of Australian Hi-FiMagazine will already know, the human ear’s sensitivity to low frequencies varies depending on the volume level of the music you’re listening to. At normal listening levels, the ear hears a properly balanced sound, and detects the low frequencies in the correct balance with the midrange and high frequencies. However, if you turn the volume down, the ear’s low-frequency perception becomes worse, and percentage-wise, you’ll be hearing less bass than you should. (What’s actually happening is that the ear is discriminating in favour of the midrange, because this is where speech frequencies lie, but the end result is the same… you hear less bass.) Loudness controls attempt to rectify this physiological fact by boosting the level of the low bass sounds when you’re playing at low volumes. The loudness controls that do this by means of a single button all fall ‘way short of what is most desirable. Yamaha’s rotary loudness control is the best implementation of loudness compensation, and I am pleased that it’s fitted to the A-S700.