Yamaha A-1

September
1 9 7 7 september 1977
1 9 8 1 1981

Brands make such units only once :
Sony made the TA-N7B, Kenwood the Supreme 700M, Luxman the M-6000, Harman/Kardon the Citation XX, Yamaha made the B-1.

Each of those well remembered components did in some way cater to a "revolution" in sound reproduction.
Even if not a 50th anniversary commemoration, not a V-FET, not Supreme and not the last of the USA h/k, the A-1 was no different : DC is the word and the A-1 is DC from A to (almost) Z.
Also filled with select parts, two large transformers and very few buttons - a fad starting then... and very much alive today.

The A-1 is an all-DC design when the green DISC switch is on, with only one film cap linking the DC phono EQ stage and the DC power section :)

The line stage also is all-DC with a low-noise differential input followed by a current-mirror-loaded differential amplifier and an emitter-follower buffer amp ; the final stage is a Darligton-connected SEPP-OCL DC amplifier.

But DISC of course was meant to be the center key : Yamaha-developed high Gm dual-Fet first stage in differential circuit with current mirror cascode bootstrapping.

When switched on, the DISC input ignores the flat amp and tone controls section and goes direct to the power amp section, adding the necessary 20dB of gain by way of two electrically and thermally matched Fet and using the resulting Dual Fet in a differential input amplifier for the DC power amplifier.

Phono MM load adaptors can be used at will when plugged into the specially provided back terminals : 47kOhm or 68kOhm ; the input itself is rated at 100kOhm when no adaptors are used.

Using MC cartridges is possible with the built-in head-amp but no alternate settings were deemed necessary. At least not at 115,000¥ !

The two beefy transformers are connected in parallel to cancel their respective leakage flux and the two big 18,000µF Nichicon caps are bypassed with two 2,2µF metallized mylar film caps.

NDCR, Noise and Distortion Clearance Range, Yamaha's late 1970s "standard measure for everything", amounts in the A-1 to a better-than-specifications result ranging between 0,6mW and 70W. At least when the volume is set at -20dB and when... the phono MM input is used.

The simplified all-DC circuit also allows low-frequency square-wave response to remain very square !

Very few inputs, too (four in toto) and just as much front controls, of which three are backlit - another fad which would later be carried onto the 1979 A-960 series and the later M-4, C-4, C-6 or M-2. And almost everybody else but Sony.

The A-1 was only black-is-black outside Japan and only shiny sliver there.


Even if a modestly priced integrated, the A-1 embodies the quintessential Yamaha : assumed, almost deceptive discretion and an absence of sound signature.

Had the A-1 had V-FETs in its power stages, it would have been part of the true audio masterpieces ; as produced, the A-1 was already a glorious -if discrete- way to wave good-bye to the 1970s.

Yamaha A-1, image 1 Yamaha A-1, image 2 Yamaha A-1, image 3
Yamaha A-1 specifications
Title Value
Power : 2x 70W (20Hz...20Khz, 8 Ohm, 0,02% THD, WRMS)
2x 85W (20Hz...20Khz, 8 Ohm, 0,02% THD, DIN)
2x 80W (20Hz...20Khz, 4 Ohm, 0,05% THD, WRMS)
THD : < 0,005% (MM to REC OUT, 8V, 20Hz...20Khz)
< 0,001% (MC to REC OUT, 2V, 20Hz...20Khz)
< 0,005% (TUNER to Speaker OUT, 35W, 20Hz...20Khz)
IMD : < 0,003% (TUNER to Speaker OUT, 8 Ohm, 35W, 20Hz...20Khz)
Power bandwidth : 10Hz...50Khz (8 Ohm, 35W, 0,003% THD)
Damping factor : > 100 (8 Ohm / 1Khz)
Frequency response : 20Hz...20Khz (+0 / -0,2dB, line to SP OUT, 8 Ohm)
10Hz (± 0dB)...100Khz (+0 / -2dB, TONE OFF)
10Hz (± 0,5dB)...100Khz (+0 / -2dB, TONE ON)
RIAA deviation : 20Hz...20Khz (± 0,2dB)
Inputs : 2,5mV / 47kOhm standard (MM ; 200pF)
60µV / 10 Ohm (MC)
200mV / 47kOhm (lines)
Maximum input level : 230mV (MM, RMS, 1Khz, 0,01% THD)
6mV (MC, RMS, 1Khz, 0,01% THD)
Outputs : 200mV / 600 Ohm (REC OUT)
2V / 600 Ohm (PRE OUT)
S/N ratio : > 97dB (MM, at 10mV)
> 82dB (MC, at 240µV)
> 112dB (lines, tone OFF)
> 105dB (lines, tone ON)
Residual noise : < 50µV (DISC on, TONE OFF)
Bass control : 350Hz / ±10dB at 20Hz
3,5Khz / ±10dB at 20Hz
Channel separation : > 70dB (1Khz, tuner to SP OUT, 5,1 Ohm input)
> 75dB (1Khz, MM to SP OUT, 5,1kOhm input, vol. at -30dB)
> 75dB (1Khz, MC to SP OUT, input shorted, vol. at -30dB)
NDCR : 6mW...70W (Phono to SP OUT, 0,1% THD, vol. at -20dB, IHF-A network)
PC : 350W (USA)
450VA (CAN)
400W (EU)
215W (JP)
Dimensions : 43,5 x 11,7 x 38,1cm
Weight : 15,8kg.
List price : 115,000¥ (1979)
Color : silver in Japan
black elsewhere
Yamaha A-1 : 0 topic
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page online since : february 2007
page updated : july 2010
page type : LGT / KNB
page weight : 477.91 Kb / 330.27 Kb

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