YAMAHA A-S701 - tear-down, thoughts about the internals & few measurements

[JohnBooty]

Agreed, this site has some amazing deals, especially on refurbs and B stock. I got a Yamaha RS202 integrated from them for a second system on sale for $89. Been very tempted to send it to Amir for testing, but shipping would probably cost half as much as the unit.

Included remote, built in bluetooth, plenty of power. Distortion rating a bit high for audiophile use - but $89!

I agree. I bought a S200 or S201 for my father in law a few years back; I think the 202 is virtually unchanged. It's fine! I suspect it'd do really poorly in ASR-style instrumented testing. But for a system where the total budget is a few hundred bucks (a second system, a starter system, etc) and the buyer isn't willing to scour through used amps/receivers I think it's a good choice. Then they can spend the rest of their money on speakers.

 

[maty]

https://www.audiosciencereview.com/...yamaha-a-s500-vs-used-a-s700.9569/post-253850

From the PDF: https://www.hifiengine.com/manual_library/yamaha/a-s700.shtml
https://europe.yamaha.com/files/download/other_assets/0/332210/A-S701_S501_S301_om_G-1.pdf

The old A-S700 has better SNR IHF-A Network (CD Direct) than new A-S701. 110 dB vs 104 dB -> 6 dB more!!!

Yamaha A-S700

Yamaha A-S701

Residual noise (IHF-A network): 30 uV (CD Direct) versus 40 uV.

 

[leonroy]

It's a little eye opening to read the specs on older Yamaha gear like the AX-890:
https://www.hifiengine.com/manual_library/yamaha/ax-890.shtml

And then read the specs of their new gear like their £4000 AS-3000 which seems to have lower specs in some areas.

How can their newer, much more expensive gear have worse specs than their stuff from 25 years ago?

 

[maty]

Yamaha A-S701

Yamaha A-S700

Without DAC board and... much better wiring than A-S701 -> sure that peak at 50/60 Hz is lower -> biggest SNR.


https://www.hifishark.com/search?q=Yamaha+A-S701
https://www.hifishark.com/search?q=Yamaha+A-S700

 

[maty]

Yamaha AX-890

http://www.hifi-forum.de/viewthread-220-7581.html

 

[trl]

A-S700 & A-S701 & A-S801 have identical power amp schematic, which is about identical with AX-890 schematic too. I found few cap "mods" here too: http://bilder.hifi-forum.de/max/588660/yamaha-ax-892-schematic-detail-main-amp-recap_787087.png. Given that freq response is perfect, I'm not sure the recap will help in any way.

If there are some differences on the specs of these amps/receiver, then it's probably due to different measurement setup or different gain used inside these amplifiers ot probably due to different preamp, volume control and switch selector, but not from the power amp itself.

As for the mains hum from my pics, it's from my measurement cable and setup, not from the amp itself. Like I said, with volume to the max there's absolutely zero hum on my speakers (inputs not shorted, but no audio source connected).

 

[Martin Takamine]

Thanks for the detailed review.

 

[peng]

Just fyi, from what I could see in the service manuals, the volume control chip of the A-S701 is the BD3473KS2, a LSI IC made by Rohm.
https://www.datasheets360.com/pdf/-7050642505570214478

The same is used in the A-S801. The newer Yamaha RX-A AVRs use a newer version BD34703KS2 but the specs look the same.
As for the DAC, the A-S801's ES9010K2M is used for the USB-DAC input only and the optical/coax inputs use the PCM5101 (this part isn't clearly shown in the schematics, but it is shown in the block diagram). Overall, I have the impression that the A-S701/801 are closely related to the AVRs, but not the A-S700 that looks more like a real integrated amp without much shared electronics with the AVRs. I suspect the A-S700 would measured quite differently (probably better) whereas the A-S701/S801 would likely be extremely similar.

 

[trl]

A-S701 & A-S801 are sharing identical analogue parts inside (input cards, preamp, amplifier and PSUs), so will measure identical when feed with analogue signals. Only the internal DAC is different. About the same can be told for the A-S700 where only few components are different from the input selector and the input cards. A-S700 measurements have been posted on the first page of this thread: https://www.excelia-hifi.cz/yamaha/test/yamaha-a-s700-australian_hifi_03_10.pdf; impressive measurements for such a low-priced amplifier, especially the square-waves plotted on the scope while driving capacitive loads.

The BD3473KS2 chip has interesting features and specs, indeed:
- 12ch input selectors
- Micro-step volume can reduce the switching pop noise during volume attenuation
- Total harmonic distortion: 0.0004%(Typ)
- Maximum output voltage: 4.2Vrms(Typ)
- Output noise voltage: 1.2μVrms(Typ)
- Residual output noise voltage: 1.0μVrms(Typ)
- Cross-talk between channels: -105dB(Typ)
- Cross-talk between selectors: -105dB(Typ)

 

[peng]

A-S701 & A-S801 are sharing identical analogue parts inside (input cards, preamp, amplifier and PSUs), so will measure identical when feed with analogue signals. Only the internal DAC is different. About the same can be told for the A-S700 where only few components are different from the input selector and the input cards. A-S700 measurements have been posted on the first page of this thread: https://www.excelia-hifi.cz/yamaha/test/yamaha-a-s700-australian_hifi_03_10.pdf; impressive measurements for such a low-priced amplifier, especially the square-waves plotted on the scope while driving capacitive loads.

The BD3473KS2 chip has interesting features and specs, indeed:
- 12ch input selectors
- Micro-step volume can reduce the switching pop noise during volume attenuation
- Total harmonic distortion: 0.0004%(Typ)
- Maximum output voltage: 4.2Vrms(Typ)
- Output noise voltage: 1.2μVrms(Typ)
- Residual output noise voltage: 1.0μVrms(Typ)
- Cross-talk between channels: -105dB(Typ)
- Cross-talk between selectors: -105dB(Typ)

Your hyperlink is for the 34704 that appears to be a newer version of the 3473 linked in post#48, but the audio specs does look identical (at least appear to be on a quick glance).

Agreed that the A-S701 should measure the same (or almost) as the A-S801 (if the USB DAC is not used for the comparison). I would disagree that the A-S700 would measure the same as well, I think the A-S700 may measure better because a) the schematics show its preamp is quite different, much more free from those LSI chips, has simpler/cleaner signal chain, b) it has better specs. My choice would be the A-S700+external DAC, that's just my opinion.

 

[Willem]

So we need measurements: https://www.audioholics.com/amplifi...1-amplifier-review/yamaha-a-s801-measurements

 

[maty]

My choice would be the A-S700+external DAC, that's just my opinion.

Me too, if one is in good condition and at a reasonable price.

https://www.hifishark.com/search?q=Yamaha+A-S700

 

[jaco61]

Thanks a lot for this report, @trl.

I bought an a-s700 used for TV and a new s701 for my stereo system. I sold my Musical Fidelity m3i at the end because the yamaha is able to control my Audiophysic Yara´s a lot better as the previous amp all alone due to more power. Moreover there is a big step in authoroty regarding bass department und a touch more depth in soundstage and separation.
This is really an outstanding good amp and also prices are very attractive so much the more for this quality.

 

[maty]

Thanks a lot for this report, @trl.

I bought an a-s700 used for TV and a new one for my stereo system. I sold my Musical Fidelity m3i...

[Polish] https://audio.com.pl/testy/stereo/wzmacniacze-stereo/2447-musical-fidelity-m3si

Graphs only in the Polish PDF: https://audio.com.pl/files/apy/1904-musical_fidelity_m3si.pdf

but m3si

SNR-A at 1 watt.... 72 dB

 

[ripmixburn]

I am curious how the built-in phono stage measurements would fare against stand alone models.

 

[jeroboam]

Thanks for your comprehensive review trl. Just wondering if you know whether the amp sections in the Yamaha NP series are the same as the AS series. Thanks.

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[/QUOTE]

 

[trl]

I am curious how the built-in phono stage measurements would fare against stand alone models.

I will do my best to find a way to measure this, just not sure when...sorry.

Thanks for your comprehensive review trl. Just wondering if you know whether the amp sections in the Yamaha NP series are the same as the AS series. Thanks.

AFAIK, NT devices are network streamers, so please be more specific.
https://audio.com.pl/testy/stereo/amplitunery-stereo/2984-yamaha-r-n803d seems to have the same amplifier inside, hope this helps.

Courtesy of audio.com.pl​

 

[NTomokawa]

This thing was once on my shortlist, along with the A-S1100.

Many thanks to your detailed pictures and measurements.

 

[trl]

This thing was once on my shortlist, along with the A-S1100.

Very good amps, indeed, but completely different schematics. While A-S2xx/3xx/5xx/7xx/801 are based on standard bi-polar output stage, the A-S1xxx/2xxx/3xxx series are J-FET input Circlotron technology with floating ground. Theoretically, the floating ground should be less prone to ground-loops and also to mains hum (which is inaudible to my A-S701, even with volume to the max. and music not playing).

So different technologies and definitely different prices.

 

[jeroboam]

I will do my best to find a way to measure this, just not sure when...sorry.


AFAIK, NT devices are network streamers, so please be more specific.
https://audio.com.pl/testy/stereo/amplitunery-stereo/2984-yamaha-r-n803d seems to have the same amplifier inside, hope this helps.

Courtesy of audio.com.pl​

Sorry tri i meant R-N series. Thanks thats good to know .