Yamaha T-700 User Manual download pdf (Page 4)

Australian Hi-Fi

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equipmenT review Yamaha A-S700 Integrated Ampliﬁer

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Graph 4 Total harmonic distortion (THD) at 1kHz referenced to 105-watts across a 4-ohm

non-inductive load using high-Z output impedance setting. [Yamaha A-S700 Integrated Amplifier]

Newport Test Labs

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Graph 5: Intermodulation distortion (CCIF-IMD) using test signals at 19kHz and 20kHz, referenced

to a 1-watt output (at 0dB) across an 8-ohm non-inductive load. [Yamaha A-S700 Int. Amplifier]

Newport Test Labs

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Graph 6: Loudness control action referenced to 0dB at 1kHz. [Yamaha A-S700 Integrated Amplifier]

Newport Test Labs

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Graph 7: Channel separation referenced to a 1-watt output (at 0dB) across and 8-ohm

non-inductive load using high-Z output impedance setting. [Yamaha A-S700 Integrated Amplifier]

Newport Test Labs

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Graph 8: Tone control action referenced to 0dB at 1kHz. [Yamaha A-S700 Integrated Amplifier]

Newport Test Labs

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Graph 9: Frequency response of CD input via CD Direct circuit path (red trace), via Pure

Direct circuit path (black trace), and through the standard CD input with both direct paths

switched off (blue trace). All measured using 8-ohm non-inductive load. [Yamaha A-S700.]

Newport Test Labs

lift is so small—and at such a low frequency—

that it would not be audible. What might just

be audible is the slight increase in level you’d

hear when switching from CD Direct to Pure

Direct or from the ordinary CD path to the

Pure Direct path. As you can see, the ﬂattest,

most linear response is provided via the Pure

Direct path, closely followed by the CD Direct

path…just as you’d expect, really!

Channel separation was not the A-S700’s

strong point, as you can see from the traces

crossing Graph 7. Channel separation is a good

86dB at 20Hz and still a very respectable 64dB

at 1kHz, but it eventually decreases to just 40dB

at 20kHz. This is more than adequate to ensure

perfect stereo imaging but shows there’s likely

a little capacitive coupling inside the ampli-

ﬁer. HF channel separation improved when

either of the direct modes was deployed. The

graph showing the action of Yamaha’s loud-

ness contour shows that Yamaha is compen-

sating for both the low- and high-frequency

roll-off issues that affect the human ear. (Some

loudness contours address only the low-fre-

quency hearing problem.) The curve’s shape

is excellent, giving a maximum 18dB boost at

low frequencies that is nicely shelved at 40Hz

and just on 8dB of boost at high frequen-

cies, shelved at 20kHz. The action of the tone

controls is also beautifully constrained, with

the A-S700’s circuit offering around +12dB of

boost and –12dB of cut. If you use extreme set-

tings of the controls there will be an audible

effect on the midrange level, but that’s pretty

much what I’d expect.

The input sensitivities are spot-on for in-

terfacing with other hi-ﬁ components, while

the very high damping factor shows that the

Yamaha A-S700’s own ‘sound’ will not change

at the whim of the speakers you connect, so

you will be hearing the true response of what-

ever speakers are connected. The square wave

performance is excellent, with the 100Hz

waveform showing the tilt expected from a

frequency response that does not extend to

d.c. but no evidence of phase inaccuracies. The

1kHz waveform is close to perfect (a little snip

off the leading edge mars it) while the 10kHz

waveform reﬂects the fact that the Yamaha A-

S700’s frequency response is only 3dB down

at 159kHz. There is quite a deal of overshoot

and some ringing evident when driving a se-

vere capacitive load, but the ampliﬁer’s output

stage settles down quickly and is demonstra-

bly completely stable.

I was pleased to ﬁnd that the Yamaha A-

S700’s standby power consumption is so low

that it already meets the Australian laws that

will come into force two years from now.

However you can see that the circuit is also

relatively efﬁcient, as the ampliﬁer draws just

a shade over 300-watts from the mains when

operating at its maximum output and mostly

will draw less than 100-watts even when it’s

working hard. Overall, I’d have to say that

Yamaha’s A-S700 delivers a truly outstanding

level of performance.

Steve Holding

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Australian Hi-Fi

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result

equipmenT review Yamaha A-S700 Integrated Ampliﬁer

0.00 Hz 4000.00 8000.00 12000.00 16000.00 20000.00

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Graph 3: Total harmonic distortion (THD) at 1kHz referenced to 90-watts across an 8-ohm

non-inductive load using high-Z output impedance setting. [Yamaha A-S700 Integrated Amplifier]

Newport Test Labs

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Graph 2: Total harmonic distortion (THD) at 1kHz referenced to 1-watt across a 4-ohm

non-inductive load using high-Z output impedance setting. [Yamaha A-S700 Integrated Amplifier]

Newport Test Labs

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Graph 3: Total harmonic distortion (THD) at 1kHz referenced to 90-watts across an 8-ohm

non-inductive load using high-Z output impedance setting. [Yamaha A-S700 Integrated Amplifier]

Newport Test Labs

Yamaha A-S700 Integrated Ampliﬁer - Test Results for Power Output

Channels Driven Load (Ω) 20Hz (watts) 20Hz (dBW) 1kHz (watts) 1kHz (dBW) 20kHz (watts) 20kHz (dBW)

1 8Ω (HiZ) 145 21.6 153 21.8 153 21.8

2 8Ω (HiZ) 115 20.6 130 21.1 127 21.0

1 4Ω (HiZ) 240 23.8 256 24.0 232 23.6

2 4Ω (HiZ) 162 22.0 190 22.7 182 22.6

1 8Ω (LoZ 100 20.0 100 20.0 100 20.0

2 8Ω (LoZ) 82 19.1 90 19.5 90 19.5

1 4Ω (LoZ) 156 21.9 169 22.3 167 22.2

2 4Ω (LoZ) 115 20.6 135 21.3 126 21.0

Note: Figures in the dBW column represent the output level, in decibels, referred to one watt output.

Yamaha A-S700 Integrated Ampliﬁer - Test Results Serial No: Y011018TV

Test Measured Result Units/Comments

Frequency Response @ 1 watt 2.5Hz–91kHz –1dB

Frequency Response @ 1 watt 1.2Hz–159kHz –3dB

Channel Separation 86dB / 64dB / 40dB (20Hz/1kHz/20kHz)

Channel Balance 0.076dB @ 1kHz

Interchannel Phase 0.27 / 0.03 / 0.59 deg (20Hz/1k/20k)

THD+N 0.0006% / 0.004% 1 watt/rated o/p

S/N Ratio (unweighted/weighted) 87dB/93dB dB re 1 watt output

S/N Ratio (unweighted/weighted) 98dB/103dB dB re rated output

Input Sensitivity (CD input) 18.4mV/177mV (1 watt/rated output)

Output Impedance 0.0371Ω OC = 2.8292V

Damping Factor 215 @ 1kHz

Power Consumption 0.82/23 watts Standby/On

Power Consumption 53 watts /303 watts 1-watt/Rated O/P

Mains Voltage Variation 242–252 volts Min–Max

Laboratory Test Results

The Dr Jekyll and Mr Hyde nature of the

Yamaha A-S700’s power supply/output stage

management has meant that when it’s driving

loads greater than 8Ω, using the ‘High’ setting

of the impedance selector, its power output

is very high indeed. As you can see from the

tabulated ﬁgures, and also from the bar graphs

accompanying the main part of the review,

when only a single channel is driven into a

4Ω load, using a 1kHz test signal, the A-S700

puts out a stunning 256-watts continuous

per channel. Under such load conditions the

power output drops a little at the frequency

extremes, but it’s still greater than 200-watts

per channel. Using the usual ‘both channels

driven into 8Ω’ criteria that is the accepted in-

dustry standard for measuring power output,

the Yamaha A-S700 delivers a minimum power

output of 115-watts per channel at 20kHz, but

can manage a little more at higher frequen-

cies, to the tune of 130-watts at 1kHz and 127-

watts at 20kHz. The only situation in which

the Yamaha didn’t deliver at least 90-watts per

channel into the test loads was when its im-

pedance selector was set to ‘Low’ and it was

being driven by a very low-frequency (20Hz)

test signal, under which conditions it fell a

little shy, returning just 82-watts per channel,

which as you can see by comparing the dBW

columns, is just 0.4dB down on rated output.

Total harmonic distortion was very low,

as you can see on Graphs 1 through 4, which

show THD at an output of 1-watt into both

4Ω and 8Ω loads, and THD at 90-watts into an

8Ω load, and at 105-watts across a 4Ω load. At

one watt output, the primary harmonic distor-

tion component is the second harmonic, and

it’s around 90dB down (0.003%) when driving

8Ω loads and a little higher (–85dB/0.005%)

when the ampliﬁer is driving a 4Ω load. The

third harmonic is sitting at around –95dB

(0.001% THD) for both loads. All higher dis-

tortion components are more than 100dB

down (0.001%) though there are more higher-

order components visible when it’s driving 4Ω

than when it’s driving 8Ω. Overall THD+N was

measured at just 0.006%. Note that on both

graphs, the noise ﬂoor is sitting right down

at –120dB above the fundamental (at 1kHz),

while even at the extreme left of the graph,

where you’d expect to ﬁnd power supply

noise, the LF noise is at 99dB and 95dB respec-

tively. At higher outputs, the ‘skirts’ around

the fundamental show that these output lev-

els are stretching the limits of the A-S700’s

power supply’s ability to deliver both voltage

and current, but despite this, the harmonic

distortion components are still very low (all

more than 90dB down) and low-order. Note

the noise ﬂoor has dropped even lower over

most of the graph, though at the extreme left,

the stress on the power supply has resulted

in increased power supply noise. However, as

you can see from the overall signal-to-noise

ratios, the Yamaha A-S700 is an exceptionally

quiet integrated ampliﬁer, returning a best re-

sult of –103dB A-weighted, referenced to rated

output. Referenced to 1-watt output (which al-

lows easy comparisons with other ampliﬁers…

or at least easy if their S/N ratios are referenced

to the same output) the Yamaha’s S/N was

measured by Newport Test Labs as 93dB.

CCIF IMD was also very low, as you can see

for yourself from Graph 5. There is very little

regenerated signal at 1kHz, and even the up-

per sidebands at 18kHz and 21kHz are around

95dB down.

Frequency response was extended, with the

A-S700 returning a result of 1.2Hz to 159kHz

±1.5dB. Across the audio band it was superb-

ly ﬂat, as you can see from Graph 9. On this

graph, Newport Test Labs has compared the CD

Direct circuit path with that of the Pure Di-

rect. As you can see, the Pure Direct trace is

the ﬂatter of the two, due to the CD Direct re-

sponse rising around 1.5dB below 20Hz. This

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