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.

The A-S700 still sports bass and treble controls. Many audiophiles don’t favour these because when you use them, some distortion is inevitable, but my view is that if you need to add a little treble lift to compensate for an overly-damped room, or roll off some bass because you have no other option but to put your speakers too close to a wall for whatever reason, it’s better to correct the frequency response with tone control and put up with a tiny increase in distortion than to endure an unbalanced frequency response. (Note, however, that I am talking about very small movements of the bass and treble controls away from the midway position. If you have to move either control further than the ‘10’ or ‘2’ o’clock positions you should instead be looking at correcting the underlying issues!)

I was also pleased that the A-S700 also has a balance control. Even if you have your speakers correctly positioned so you get a perfect image at the listening position, this will only be true with well-recorded CDs, and I am always surprised at how many CDs are recorded hotter in one channel than the other, and thereby shift the image too far to the right or left. (I suspect the reason is that many recording studios do not check their monitor speakers’ accuracy as regularly as they should.) And when a recording is not correctly balanced, you will either need to adjust the balance control on your amplifier to ensure correct balance, or move your speakers. I know which I’d prefer to do!

The A-S700 is supplied with a full-function remote control that will operate other Yamaha components as well. However, although the amplifier is supplied in two different finishes (satin black or brushed aluminium), the remote control for both is brushed aluminium.

In Use and Listening Sessions

Setting up the A-S700 is relatively straightforward, but there are some things you do have to remember. The first of these is that if you choose the satin-black finish, you should make sure your hands are absolutely clean before unpacking and positioning the amplifier, because the surface shows fingerprints quite easily, and if you mark it, you will need to apply some elbow-grease to remove them. The second is that for whatever reason, I found the speaker terminals quite difficult to turn (perhaps because of their diameter and the proximity of the protective shrouds). Although they’re good quality terminals, they could have been improved, particularly given the AS700’ s price. Luckily, the terminals will accept standard banana plugs, as well as dual Pomona plugs, so I’d suggest wiring up your speaker cables with either of these fittings rather than using bare wire. Finally, you need to remember to set the speaker impedance switch before you start using the amplifier, and to do so with the amplifier switched OFF! (If you forget, and need to move the switch, you should switch the amplifier off, and then the mains power, before re-setting the switch.)

The volume control had the slightly spongy feel that is typical of motor-driven volume controls, however the benefit is that the control actually rotates when you press the volume ‘up’ and ‘down’ buttons on the remote, so you can always see the volume setting on the front panel. The input source selector has a lovely action under the fingers, thanks to the encoder circuitry, and the LEDs are bright, so you can always see what source you’ve selected from quite a distance away, but I was slightly perplexed that although the action of the control is contiguous, in that you can spin it in either direction without ever reaching an ‘end stop’, the actual switching stops once you have reached the Line 3 input when going anti-clockwise, and the Phono input when going clockwise. This isn’t a problem, it simply means that although it’s an encoder, it works like a mechanical selector. I imagined that perhaps this was deliberate, considering that the styling of the A-S700 echoes the styling of the amplifiers Yamaha was designing ‘way back in the ‘70s.

After experimenting every which way with the Yamaha A-S700’s impedance selector and a variety of different loudspeakers, every one of which I knew the exact impedance of (thanks to graphs of the impedance moduluses, and lists of the actual measured ‘nominal’ overall impedance supplied by Newport Test Labs), I eventually concluded that if you are using just a single pair of speakers with the A-S700, you should set the impedance selector to the ‘high’ position, even if the label on the rear of the speaker says ‘4Ω’. It is only if you have connected TWO pairs of speakers to the A-S700, and will be using the A+B mode regularly that I would recommend using the ‘Low’ position. (I know this is somewhat at odds with Yamaha’s recommendation, but I think Yamaha is playing it super-safe.) As a result of my investigations, all my listening sessions were conducted with the A-S700’s impedance switch set to the ‘High’ position. The A-S700 proved to be very powerful, as it was easily able to over-power even the largest and most inefficient speakers I had available, in the process creating louder sound pressure levels than most people will ever need. The A-S700 is so powerful, in fact, that even with inefficient speakers in a large room I don’t think you’ll ever be hungering after more power than it can deliver. It really is an amazingly powerful amp! Even when you’re not running it full tilt (and you won’t be), the power that is available on tap means that the bass is really solid and well-defined, so that there is a real sense of authority in the lowest frequencies. More importantly, even if there’s a lot going on in the bass region, the power available means that there are no unwanted modulations of the very highest frequencies, so the treble sound is as pure as it is when there’s very little happening down low. But the bass isn’t just big, it’s also so rhythmic and bouncy that you don’t even start to question pace and timing: they’re right there… vibrant and on the go.

overall impedance supplied by Newport Test Labs), I eventually concluded that if you are using just a single pair of speakers with the A-S700, you should set the impedance selector to the ‘high’ position, even if the label on the rear of the speaker says ‘4Ω’. It is only if you have connected TWO pairs of speakers to the A-S700, and will be using the A+B mode regularly that I would recommend using the ‘Low’ position. (I know this is somewhat at odds with Yamaha’s recommendation, but I think Yamaha is playing it super-safe.) As a result of my investigations, all my listening sessions were conducted with the A-S700’s impedance switch set to the ‘High’ position.

The A-S700 proved to be very powerful, as it was easily able to over-power even the largest and most inefficient speakers I had available, in the process creating louder sound pressure levels than most people will ever need. The A-S700 is so powerful, in fact, that even with inefficient speakers in a large room I don’t think you’ll ever be hungering after more power than it can deliver. It really is an amazingly powerful amp! Even when you’re not running it full tilt (and you won’t be), the power that is available on tap means that the bass is really solid and well-defined, so that there is a real sense of authority in the lowest frequencies. More importantly, even if there’s a lot going on in the bass region, the power available means that there are no unwanted modulations of the very highest frequencies, so the treble sound is as pure as it is when there’s very little happening down low. But the bass isn’t just big, it’s also so rhythmic and bouncy that you don’t even start to question pace and timing: they’re right there… vibrant and on the go.

Midrange sound is crystal-clear and beautifully transparent. There’s a lovely sense of clarity and ‘ease of listening’ that comes through at all times… though it is particularly obvious when auditioning lighter works that are heavy on human voice and just a few higher-pitched instruments (think typical ‘demo track’ at any hi-fishow). However, extended auditioning with complex orchestral and/or choral works will show that even when presented with such sonic difficulties, the sound of the Yamaha AS700 doesn’t ever become compressed, or even congested, so that it’s very easy to appreciate the multiple threads that are usually woven by composers, as well as the professionalism of the musicians in teasing out those threads into a performance.

The air around the high-frequencies is a joy. Individual notes seem to suspend themselves just long enough to allow you to enjoy the harmonic relationships with what lies below, yet not hang around so long that they confuse the issue by extending into unrelated multi-layered puffery. Sonic purity was at the highest level.

What you certainly won’t hear from the Yamaha A-S700 is any unwanted electronic noise, because Yamaha’s engineers have excelled themselves. There is absolutely no background circuit noise or hum at all. And, although I could hear tiny differences between the ‘normal’ mode and the two direct modes when music was playing, I couldn’t hear any differences at all in noise levels between the three when no music was playing, even when the volume level was advanced. This ultralow noise capability, combined with the high power output level, and the speed with which the amplifier was able to respond to even the fastest transients, meant that the overall sound is highly dynamic, which in turn gave musical performances the lift they need to propel them to the upper levels of the reproduced sound stakes.

Click for Test Results in PDF FormatReaders interested in a full technical appraisal of the performance of the Yamaha A-S700 Integrated Amplifier should continue on and read the LABORATORY REPORT published in the following pdf. Readers should note that the results mentioned in the report, tabulated in performance charts and/or displayed using graphs and/or photographs should be construed as applying only to the specific sample tested.

Conclusion

I can unhesitatingly recommend Yamaha’s AS700 to anyone who’s after superior sound reproduction from an integrated amplifier, not just because of its sound quality and overall performance, but also because Yamaha has such a great reputation for its product quality and its customer support… in the unlikely event that you’ll ever need it, which I doubt you ever will.

Yamaha A-S700 Integrated Amplifier

Brand: Yamaha
Model: A-S700
Category: Integrated Amplifier
RRP: $1,099
Warranty: Two Years
Distributor: Yamaha Music Australia Pty Ltd

Positive

High power output Whisper-quiet noise levels Lovely sound balance

Negative

Speaker terminals Remote only comes in silver Front panel marks easily