Yamaha A-1 Vintage Amplifier Review

[restorer-john]

I see this:

From the sell sheet on page 2 of this thread, purportedly from August of 1978.

Ray, that is a preamplifier rated output, not a rated line input sensitivity.

This is the sensitivity, and typical for the era (150mV-200mV for rated output):

Most power amplifiers were 1.0-2.0V sensitivity for full rated power. Perfectly normal for the time and still the case.

 

[LuckyLuke575]

From Restorer John's archive, here's a high res scan of the original brochure (Aug/1978)

View attachment 37069

View attachment 37070

View attachment 37071

View attachment 37072

This is a top class and handsome unit. I love the old school amps and equipment.

 

[LuckyLuke575]

Fantastic to see a classic reviewed, and rather satisfying to see that measurement indicates that the reverence some of us have for classic hifi is not just rose tinted nostalgia.

In terms of what happened, in some ways we as consumers got what we wanted. The big Japanese outfits had a sort of engineering arms race in the 70's and 80's to develop the ultimate measured performance and invested serious money into their engineering and R&D. The resulting products were manufactured to a staggeringly high standard. Now you might think consumers would welcome this, but no, a culture of golden eared disdain for measured performance evolved, aided and abetted by reviewers who waxed lyrical about shoddily engineered and made boutique gear which had terrible measured performance. Products like this were derided as being "sterile", soulless, bland, lacking all the usual audiophile subjective terms blah blah blah, is it really any wonder that some Japanese companies realised which side of their bread was buttered and embraced that culture?

I actually think the mass market move away from stereo systems and towards viewing audio equipment as a commodity in the late 90's and on was actually much more rational and sensible than all the audiophile nonsense that sustains the high end bubble. I find it all very sad as a good set up (and I mean good, not expensive, it need not cost a great deal) does make listening to music more enjoyable.

I totally agree with this point of view. In hindsight, it looks like the market / industry took a weird turn at some point. It seems like the heyday of Hi-Fi was the early 90s when all the R&D up to that point had led to a great technical standard and features, and the quality was still excellent because the manufacturing was still taking place in Japan.

 

[amirm]

Thank you Amir !!!
Someday I would like a measurement of my favorite brand, Sansui.

Sansui takes me way back. My first serious audiophile amplifier was a Sansui back in 1960s! It was a terrible amp though with capacitor coupled output and not a lot of clean power. What would be a good representative model of the brand?

 

[LuckyLuke575]

I used to be a lurker until recently. While I can't speak for everyone here, so far this forum has helped me spend less on better engineered equipment not more. Most of the time I would not claim to have heard a significant difference as I'm not a trained listener, but on two occasions I was very audibly validated in my decision and ASR for providing the data that informed it (while saving money).
On a separate note, yes that thread you linked to got uncivil but that is hardly unique these days and from my experience of this forum it is not the norm here. As for people doing more than measuring, in this thread a group is organizing to get together to do listening tests.

I can echo this sentiment. Especially in an era where there's so much biased, ignorant, and paid for reviewing going on, and the whole market and discussion being online / virtual, it's difficult to really know what the true performance, design, and value of any piece of equipment is. And this site does a great service to people looking for objective reviews.

Yes there may be validity in the 'how does it sound', and audibility threshold arguments, but if I take the example of Massdrop (which I frequent), there's so much fanboy behavior and hype around certain products coupled with marketing bullshit for products that are patently badly designed and flawed in the performance, and the only real objectivity that comes through is from links to ASR (the Airist DAC is an example of this, following the ASR review). There are so many young people (including myself) coming back to Hi-Fi, but it's sad that unscrupulous people are taking advantage of people's interest and enthusiasm, only for them to get ripped off or passed bad equipment. So ASR is doing a major service in that regard.

 

[restorer-john]

What would be a good representative model of the brand?

You would have to consider the AU-Dxx series from around 1983/4 and the AU-Xxx series from later.

I can give you some suggestions later today.

 

[LuckyLuke575]

This is a review and detailed measurements of the Yamaha A-1 vintage integrated amplifier. It is on kind loan from a member. He tells me that it has been serviced and restored a couple of years ago. The Yamaha A-1 came out in 1977 during a competition to produce the best spec audio products.

Most of the controls are hidden behind a drop down door:

View attachment 37040​

On touch of the volume control and you are taken back to golden age of such mechanical controls. Boy, had I forgotten how good these used to feel compared to garbage that passes from mass market audio companies these days.

The buttons have the most solid feel, reminding me of ones we used to put on pro video products. Solid as a rock with positive feedback.

The "DISC" button is the equivalent of "pure direct" on modern AVRs and such and bypasses much of the circuitry internally. Alas, it is designed for LP playback to the phono equalization remains in the path so I did not test it for this review (may do later).

There are tone controls (but no balance). I set it to off of course for my testing.

The manual hearkens back to an area when performance indeed did matter including measurements that remind one of chip specifications:

View attachment 37041​

The rest of the manual is full of diagrams clearly showing circuit flow and topology of various stages. Shame on the audio industry for forgetting its roots.

The unit is for Japan market and as such, is rated at 100 volts. To test it here in US, I used a variac to dial down the voltage to 100. This is a beefy 2000 volt-amp unit so should not impede power. But may be responsible for some mains leakage (which I could not lower with playing with grounding).

Speaking of beefy, the A-1 is massively heavy on the left side, sporting two independent transformers, one for each channel.

View attachment 37055​

The components inside are quite rusty as you may be able to tell, having enjoyed some time in a damp shed no doubt. Despite that, at no time did the unit complain by shutting down or anything. It does have a high pitch whine if you stress it though or during warm-up.

Those metal components in the middle of the heatsink are the power transistors using the "TO-3" package. During that era, anytime you saw these transistors you knew that good money was spent on the components. TO-3 transistors with their large metal enclosure dissipate heat a lot better than the TO220 and other alternatives. Alas, they cost a fortune so they were phased out over time.

The power supply capacitors are top-brand japanese Nichicon. They did not look very fresh to me though even though they were supposed to have been replaced two years ago. Wonder if they used older parts.

One of the things I did not like was the flimsy speaker terminals that you could barely get to tighten on bare wire. I soldered my wires to give them more girth and they still barely held on to them.

Pre-amplifier Audio Measurements
The Yamaha A-1 has preamplifier out but unfortunately no input to the power amp. I thought we start with how the preamp perrforms then before testing the whole unit:

View attachment 37042

Looking to the right of our 1 kHz tone, we see that the only harmonic distortion visible is the third harmonic at -110 dB! That is very good.

Alas, SINAD which looks at both distortion and noise suffers from the power supply spikes, lowering to 90 dB or so. Still respectable but a loss of 20 dB.

FYI, 1 volt is the maximum usable input on this amp. Going beyond that severely clips. Rated input is actually much lower than this and being before the CD era, this is understood.

Amplifier Audio Measurements
I set the gain to 29 dB using the volume control and ran our usual dashboard at 5 watt into 4 ohm using a 1 kHz tone:

View attachment 37043

I should note that I had to let the unit come up to temperate at 9 watts or so for a few minutes. Prior to that one channel had a lot more distortion which gradually reduced. The A-1 has massive heatsinks and the temperature sensor is placed on the opposite side of the transistors, requiring a while for it to get a more accurate snapshot of the transistor temperature to set bias.

Once there, we see again that our harmonic distortions are quite low at below 100 dB. What is there are power supply components which heavily derate SINAD. As is, the A-1 doesn't place very high in our list of amplifiers:
View attachment 37044

Note that from audibility point of view, the power supply spikes don't matter much since our threshold of hearing is quite high there. So this is a case of SINAD showing us something that is not very representative of audible performance. Alas, we have made our bed and have to sleep in it with respect to SINAD.

Drilling more and only looking at harmonic distortion we see a far prettier picture:

View attachment 37045

Distortion products are at or below -105 dB which again, is very good. Our threshold of hearing is only -115 dB or so meaning these distortions are all but inaudible.

Alas, noise is the problem as we can see with no input to the A-1:

View attachment 37046

How much of this is due to age of this unit is hard to say. Perhaps whoever restored it did not pay enough attention to power supply output. There is no equivalent measurement from Yamaha to know for sure. The kind of FFT analysis we can do today would have been unheard of when this device came out.

The higher noise floor hurts baseline performance at 5 watt:
View attachment 37047

The owner told me that the SNR is around 112 dB or so. Clearly we are missing that by good bit but what is there is good enough at full volume to clear the 16 bit CD hurdle.

1 kHz spectrum naturally shows a very clean output:

View attachment 37048

THD+N versus level and frequency is I think the cleanest I have seen:

View attachment 37049

All the lines land on top of each other as if the frequency doesn't matter. Note however that due to high noise floor, we don't get to see the true distortion metric so perhaps that is helping here. Yamaha measurements show more of a differentiation so perhaps our sample unit is noisier than it should be.

Let's look at our power output versus distortion and noise into 8 ohm:

View attachment 37053

We meet the specification for power and do better in distortion by a mile.

Here is the same for 4 ohm load:
View attachment 37054

We clock a lot better here beating both power rating and distortion level Yamaha used.

I did not attempt to measure peak or maximum power as these keep the amplifier at full power for a while and I did not want to chance damaging the unit. Likely could have handled the load but I just did not want to take a chance of blowing the output stage and searching for devices that may not be manufactured anymore.

Conclusions
The stories of these hero amplifiers of the 1970s beating the distortion devil seems to be true. The Yamaha A-1 aces such tests, beating vast majority of amplifiers today and putting many to shame big time. What keeps it away from achieving top status is the high power supply noise. As mentioned, I am not sure if that is due to the sample I have or typical of the unit. With that included, our state-of-the-art amplifiers like Hypex/Purifi and Benchmark AHB2 provide a wide gap in performance.

I don't know how much these units go for but if they are reasonable in price, they would make a good alternative to modern amplifiers.

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As always, questions, comments, corrections, etc. are welcome.

Seeing the vintage amplifier, the panthers are demanding vintage clothing to fit in! I think they have a point so like to get them all new, 1970s era outfits. So appreciate kind donation from you all using : https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

Thanks for this review @amirm. It's great to see how well this vintage equipment performs. I'm a huge fan of equipment from the 70s/80s/90s given the quality, performance, and value they offer on the secondhand market. Keep them coming!

 

[Bamyasi]

You would have to consider the AU-Dxx series from around 1983/4 and the AU-Xxx series from later.

My vote goes to AU-D9, which was my first serious amplifier bought back in 1984.

 

[oldsysop]

Sansui takes me way back. My first serious audiophile amplifier was a Sansui back in 1960s! It was a terrible amp though with capacitor coupled output and not a lot of clean power. What would be a good representative model of the brand?

AU-9900 , AU-11000 , AU-20000 , AU-X1 , AU-777A they're my favorites. But there are many more. I would like a review of anyone.

 

[AudioSceptic]

Ray, that is a preamplifier rated output, not a rated line input sensitivity.

This is the sensitivity, and typical for the era (150mV-200mV for rated output):

View attachment 37118

Most power amplifiers were 1.0-2.0V sensitivity for full rated power. Perfectly normal for the time and still the case.

Yes, and CD players would most likely be connected to the Aux input in the early days of CD. This would be in the range 100-200 mV. Once CD became established, inputs marked "CD" appeared, along with greater headroom, and maybe with reduced sensitivity to avoid jarring volume changes.

 

[AudioSceptic]

You would have to consider the AU-Dxx series from around 1983/4 and the AU-Xxx series from later.

I can give you some suggestions later today.

Never owned any Sansui but their best FM tuners are still highly rated. I guess Amir won't bother with FM.

 

[oldsysop]

https://audiokarma.org/forums/index.php?threads/yamaha-a-1-asr.889131/#post-13175610

 

[Mnyb]

If there is a risk of overloading the input with modern sources I would recommend some kind of inline passive attenuators like the ones rothwell makes .

 

[restorer-john]

https://audiokarma.org/forums/index.php?threads/yamaha-a-1-asr.889131/#post-13175610

Study the schematic. Look at the windings, the layout and where they go. There is one bridge rectifier for the main amp rails and one for the regulated front end. The windings are arranged as a centre tapped transformer with one winding from each transformer forming each leg of the CT.

You cannot simply parallel transformer windings in any case unless you want all sorts of problems. The only safe way to do it would be to separately rectify each transformer's output and then combine at the filter caps. This is done in some other Yamaha amplifiers such as the M-80/85 and they incorporate 4 bridge rectifiers to achieve that.

 

[jsrtheta]

"Most of the controls are hidden behind a drop down door"

Indeed there are, and among them is a tone bypass switch, which will do pretty much what the "DISC" button doesn't do: Give you a line level signal output without tone controls, more or less what a "Direct" switch does.

 

[amirm]

"Most of the controls are hidden behind a drop down door"

Indeed there are, and among them is a tone bypass switch, which will do pretty much what the "DISC" button doesn't do: Give you a line level signal output without tone controls, more or less what a "Direct" switch does.

The DISC path is supposed to be DC coupled which is what I wanted to see.

 

[Georgrig]

Has anybody had the chance to play with the Yamaha M-5000? Looks beautifully made, with a price tag to match! Haven't seen any plots though!

 

[anmpr1]

I don't know if that was typical, e.g., Quad 33 was 0.5 V output, 405 was 0.5 input, or was that particularly low?

They were designed by Peter Walker's team that way, to be sold and to match as a pair for their speakers. Why he chose those electrical parameters I can't say. Maybe it was typical for British components of the era?

 

[AudioSceptic]

They were designed by Peter Walker's team that way, to be sold and to match as a pair for their speakers. Why he chose those electrical parameters I can't say. Maybe it was typical for British components of the era?

That's what I'm asking. Looking at a few other products it looks like there was no standard but preamp outs and power amp inputs tended to be in the 0.5 to 1.0 V range, while line levels were generally 100 mV. There would be quite a volume jump switching from another source to CD, even if the headroom was OK.

 

[Willem]

0.5 Volt pre amp output and power amp input was quite normal for European amplifiers of the day. I am still using (refurbished) Quad 405-2 and 606-2 power amplifiers, and all they need is inline attenuators.
The 2 Volt output of CD was a problem at the time, and Quad immediately introduced a special input board for the Quad 33 pre amplifier, just as they had supplied custom input boards for a number of MM cartridges. I am convinced that the high level of CD output and the resultant clipping of the amplifier input explains much of the complaints about CD sound at the time. In fact, this is still a real issue, particularly with those dics players and DACs that cheat in the demo room by having an even higher output level.