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

[peng]

I did compare some specs of the A-S701 and C316BEE. As I mentioned, the A-S701 certainly offer more (a little more than 3 dB) power output. Only if more power is not needed, then the NAD would be just as good. It doesn't have the digital front end, but some (such as me) may actually prefer ext. DAC that will measure much better than the ones build in to the A-S701, or even the A-S801, and for less than $150. Such ext. DACs typically can play more files including DSD256, even DSD512, that those build in ones typically don't. I don't even like integrated amps in general, but am very happy with my C326BEE. The C316BEE is not as good but should be close. Even if I needed more power, I would likely opt for the C356BEE.

C316BEE:

• Signal / Noise ratio, A-weighted
• 95dB (ref. 500mV in, 8 Ohm 1W out)
• THD + Noise
• <0.01% (20Hz-20kHz, 250mW to rated output)
• SMPTE IM
• <0.02% (intermodulation distortion 60Hz-7kHz, 4:1. from 250mW to rated output)
• IHF IM
• <0.01% (CCIF IM distortion, 19 + 20kHz rated output)

A-S701:

For measurements, I could only find some for the A-S801, A-S700 and the C320BEEE.
A-S801 power output measurements based on Audioholics.com were:

2 channels driven, CFP-BW
105 watts 8 ohms, 0.01%
185 watts 4 ohms, 0.1%

In terms of SINAD, it would be 80 dB at 105 W into 8 Ohms and 60 dB at 185 W into 4 Ohms, that's actually not as good as the AVR-X3700H for 8 Ohm, but a little better for a 4 Ohm load.

I think if one needs more than 100 W 8 Ohms, for two channel stereo with build in DAC, the A-S701 and S801 are hard to beat, though for me I would definitely go with the A-S700 and get my own DAC. Unfortunately the A-S700 has been discontinued for quite some time so most likely only used ones are available.

 

[Willem]

Do you have any reason to believe that an external DAC would sound audibly better under controlled listening conditions?

 

[peng]

Do you have any reason to believe that an external DAC would sound audibly better under controlled listening conditions?

It depends, usually not. To me, it is more about playability. In my experience what matters most is the recording quality, and I found that chance is better for music files at resolution 24b/192kHz, DSD128, DSD256 to have good quality recording.

If the quality of the recording is good, 16bit/44.1 kHz using a $100 dac can sound better than one with not so good recording quality at 24bit/192 kHz using a $1000 dac. That's what I believe, based on my experience. That's why I want my dacs to be able to play any format at any available resolution.

 

[burak82]

hi everyone, i found a used one and getting as 701 this week. I am trying to find out if the internal DAC is a good quality DAC? I can get an external DAC and for the price/quality ratio, i put my eyes on TOPPING E30. is this better than Yamaha´s internal DAC? Question is, will i be able to catch the difference between two listening to TIDAL or high res FLAC files? thanks in advance

 

[Willem]

I bought an AS 501 for my daughter last Autumn, and the DAC seems perfectly fine. I would honestly be very surprised if an external DAC will sound any better. The real difference is that the E30 has a usb input as well.
I am not sure what you mean by HiRes Flac files, but the sonic advantages of anything over and above 16/44 are dubious at best.

 

[johnk]

Thank you for all of the fascinating information. I own a Yamaha A-S700 which by sheer luck appears to be the best of the bunch based on the numbers.
Given that the SNR and THD for the A-S700 appear to be better than the A-S2100, A-S2200 what are the benefits of the higher end Yamaha amps (other than the very nice VU meters)? What real difference do a toroidal PSU or the additional capacitors in the power output stage actually make?
Thanks,
John

 

[restorer-john]

Thank you for all of the fascinating information. I own a Yamaha A-S700 which by sheer luck appears to be the best of the bunch based on the numbers.
Given that the SNR and THD for the A-S700 appear to be better than the A-S2100, A-S2200 what are the benefits of the higher end Yamaha amps (other than the very nice VU meters)? What real difference do a toroidal PSU or the additional capacitors in the power output stage actually make?
Thanks,
John

Yamaha have always had a "sweet spot" for value in their ranges, and the A-S700 may well be the one to buy, based on its performance and bang for the buck. The 3, (4), 5 and 7 series were always great value. The 9 and 10 series, less so. By the time you are into 21, 22 and 30 series, the law of diminishing returns hits you hard.

The Japanese traditionally had the 3 series- good value. The 5 series- everyman very good quality. 7 series- state of the art. 9 series- no expense spared. And then 10 series was the statement stuff of dreams.

Like the car companies. 1,2,3,4,5,6,7,8 series... It's funny because companies like Mercedes and BMW have filled out their offerings to the point of complete lack of differentiation and have diluted their legacy to the point I no longer aspire to anything of theirs.

The benefits of the higher end Yamaha products are usually more of the same, better quality finishes, fit and controls. More output devices, better power supplies, more premium components and more conservative ratings.

A toroidal transformer does not automatically make a better amplifier. All transformers are expensive parts of the design, and toroidals have certain advantages and disadvantages. I would not buy or reject an amplifier based on the transformer design. Audiophiles like toroids, because they look exotic. They are considerably lower profile than a big juicy EI and can be designed into slimmer products. Personally, I like big EIs and plenty of heatsinking- something the better Yamahas do well.

 

[Willem]

The newer ASx01 series is primarily distinguished by its digital inputs, which add to their market value.

 

[trl]

The high-end ones are using a completely different schematic topology, more transformer windings, shielded transformer and individual integral power supplies (distinct for preamp, amp, digitals etc.). There's basically not even a single inch of schematic similar with the A-S700 or A-S701 maybe the power supplies are similar, but A-S701 only has one PSU while A-S2100 has at least 5...if I remember well.

Based purely on output performance, specs and price you can't easily beat this amp.

 

[johnk]

Thank you for the insights. I recently had the opportunity for a cheap deal on an A-S2100, but when I compared the specifications to my current A-S700 I was not sure that it was really worth it.
Oddly enough I never really wanted to buy the A-S700 in the first place. I had actually bought a Cambridge Audio 650a. Took it home and plugged it in and listened to it for a week and was quite unimpressed. Fortunately the store were happy to exchange it for another amp, but their range was limited and the Yamaha was the next best option. I did in AB comparisons (not level matched) between a Plinius amp and the Yamaha and my impressions were that the Yamaha was very similar. In summary, I think I was rather lucky

 

[trl]

Given that the SNR and THD for the A-S700 appear to be better than the A-S2100, A-S2200

On the first page of this thread I posted few measurements links, here's one for the A-S700: https://www.excelia-hifi.cz/yamaha/test/yamaha-a-s700-australian_hifi_03_10.pdf.

However, measurements to different amps should be done with similar measurement equipment and under the same conditions: same audio generator, same input voltage, same gain (when possible), same output voltage, same load etc. Even A-S701 might measure slightly "worse" than the A-S700, although they are sharing an identical internal schematic on the power amp and preamp, but the volume control and logic control are different, hence the slights difference in the specs (check out https://www.audiosciencereview.com/...e-internals-few-measurements.9459/post-253852).

However, with my ears at less than 0.5m in front of the tweeter, I can't hear any background noise with my A-S701 amplifier to the max. volume, so this makes it a really low-noise amplifier to me (I was using 4 Ohms 90.5 dB/1m speakers, CD-Direct setting, RCA inputs disconnected).

 

[maty]

Thank you for the insights. I recently had the opportunity for a cheap deal on an A-S2100, but when I compared the specifications to my current A-S700 I was not sure that it was really worth it.
Oddly enough I never really wanted to buy the A-S700 in the first place. I had actually bought a Cambridge Audio 650a. Took it home and plugged it in and listened to it for a week and was quite unimpressed. Fortunately the store were happy to exchange it for another amp, but their range was limited and the Yamaha was the next best option. I did in AB comparisons (not level matched) between a Plinius amp and the Yamaha and my impressions were that the Yamaha was very similar. In summary, I think I was rather lucky

If you want to detect differences between well-built amps, with the rest of the chain the same, you need to compare with very good recordings and high / very high DR (Dynamic Range): DR > or >> 10 dB. Better with acoustic recordings.

Assuming the rest of the audio chain does not act as a bottleneck, something I am afraid happens very often.

 

[ZolaIII]

I did compare some specs of the A-S701 and C316BEE. As I mentioned, the A-S701 certainly offer more (a little more than 3 dB) power output. Only if more power is not needed, then the NAD would be just as good. It doesn't have the digital front end, but some (such as me) may actually prefer ext. DAC that will measure much better than the ones build in to the A-S701, or even the A-S801, and for less than $150. Such ext. DACs typically can play more files including DSD256, even DSD512, that those build in ones typically don't. I don't even like integrated amps in general, but am very happy with my C326BEE. The C316BEE is not as good but should be close. Even if I needed more power, I would likely opt for the C356BEE.

C316BEE:

• Signal / Noise ratio, A-weighted
• 95dB (ref. 500mV in, 8 Ohm 1W out)
• THD + Noise
• <0.01% (20Hz-20kHz, 250mW to rated output)
• SMPTE IM
• <0.02% (intermodulation distortion 60Hz-7kHz, 4:1. from 250mW to rated output)
• IHF IM
• <0.01% (CCIF IM distortion, 19 + 20kHz rated output)

A-S701:

View attachment 128097

For measurements, I could only find some for the A-S801, A-S700 and the C320BEEE.
A-S801 power output measurements based on Audioholics.com were:

2 channels driven, CFP-BW
105 watts 8 ohms, 0.01%
185 watts 4 ohms, 0.1%

In terms of SINAD, it would be 80 dB at 105 W into 8 Ohms and 60 dB at 185 W into 4 Ohms, that's actually not as good as the AVR-X3700H for 8 Ohm, but a little better for a 4 Ohm load.

I think if one needs more than 100 W 8 Ohms, for two channel stereo with build in DAC, the A-S701 and S801 are hard to beat, though for me I would definitely go with the A-S700 and get my own DAC. Unfortunately the A-S700 has been discontinued for quite some time so most likely only used ones are available.

If you want to get over 60 W (57~58 ideally) 8 Ohm's with any Yamaha that uses the same output power stage and retain portion of SINAD I suggesting using a preamp as they have very tolerable 2.45 V input transistor (2$ part) as restorer-john shown elsewhere.
I got a R-N402D, aimed on older but deacent DAC which they re used a lot (Burr brown DSD 1791 [PCM 1791 with added DSD input, now Ti]) as I thought it will be ironed out implementation. Digital input is simplified (compared to R-N and A 70x and 80x series) , no sub out and no phono stage. Costs about 500$ got it used in great condition for half the price.
DAC is quite OK for the applied purpose, streaming and generally software are OK. It's not charming nor anything to write home about and remote is abomination but as a package it's hard to find better and if you do to justify to your self a price premium.

 

[ZolaIII]

@maty I would even go with DRA of 9 (I do use EBU R128) with great recording, call me brave.

 

[killdozzer]

Few basic measurements done with Xonar U7 and Focusrite Solo 3.

First measurements were done with my Picoscope that showed a 35mV DC voltage on output. This is a respectable value for an amplifier that is able to push over 30V RMS on 8-Ohms speakers. I've seen headamps with 20-30mV of DC.

View attachment 36396
Ruler flat from 10 Hz to 22 KHz


View attachment 36397
Impulse response of the built-in DAC (optical input from Xonar U7 used as USB transport)
​

The below measurements were done without vs. with speakers connected, to show the influence of the 3-ways speakers for the output stage and the measurements values differences. The voltage used was around the value of 4.5V RMS, so a 5 W was used as reference here, as Amir suggested in his own power amps reviews. However, increasing the volume will lower the THD+N and increase the final SINAD. External DAC used was Conductor V2+ on DAC-Out (PRE-Out is too noisy due to the internal pre-amp chip).

View attachment 36400
External DAC used on CD-input, CD-DIRECT pressed, no speakers connected, 1 KHz


View attachment 36398
External DAC used on CD-input, CD-DIRECT pressed, real 4-Ohms speakers connected, 1 KHz


View attachment 36404
Built-in DAC (COAX-input), CD-DIRECT pressed, no speakers connected, 1 KHz

View attachment 36402
Built-in DAC (COAX input), CD-DIRECT pressed, real 4-Ohms speakers connected, 1 KHz
​

Seems that the Conductor V2+ has a better DAC inside than the A-S701, because with speakers connected I was able to get a THD+N of 0.0046% vs. 0.0071%.

Usually, when speakers are connected, the low-end of the audio band is more impacted, so below tests are with 50 Hz sines.

View attachment 36401
External DAC used on CD-input, CD-DIRECT pressed, no speakers connected, 50 Hz

View attachment 36399
External DAC used on CD-input, CD-DIRECT pressed, real 4-Ohms speakers connected, 50 Hz

View attachment 36405
Built-in DAC (COAX-input), CD-DIRECT pressed, no speakers connected, 50 Hz
View attachment 36403
Built-in DAC (COAX input), CD-DIRECT pressed, real 4-Ohms speakers connected, 50 Hz
​

Again, the external DAC connected to CD-input was measuring a bit better than the built-in one for 50 Hz test signals as well, with a THD+N of 0.0052% vs. 0.0080%.

So, for 5 Watts of power on 4-Ohms speakers connected and external DAC playing sines I got a THD+N of 0.0046% with 1 KHz and 0.0052% with 50 Hz.

Very good post! Thanks!

 

[maty]

@maty I would even go with DRA of 9 (I do use EBU R128) with great recording, call me brave.

I can only say that years ago, carrying a USB with all kinds of music, from MP3 320 kbps to 24/96 FLAC, I only noticed differences in my two audio equipment and not in theirs, hence the bottleneck on the audio chain.

In my second team, in near field, I easily detect the differences, which have increased as I have been optimizing / tweaking the components and the W10 (to play multimedia, being unable to achieve the same with different Linux).

 

[Willem]

In conclusion, this amplifier (and probably its AS 501 and AS801 sisters) is an all in one bargain for most people. All measurements are good enough for sonic transparency, and power output is enough for most people, unless they use inefficient speakers in large rooms.

 

[ZolaIII]

I can only say that years ago, carrying a USB with all kinds of music, from MP3 320 kbps to 24/96 FLAC, I only noticed differences in my two audio equipment and not in theirs, hence the bottleneck on the audio chain.

In my second team, in near field, I easily detect the differences, which have increased as I have been optimizing / tweaking the components and the W10 (to play multimedia, being unable to achieve the same with different Linux).

Did that last night and thought what a hell whose I doing. For that purpose I didn't use filtering with which I usually exaggerate with when using PC and sort of cheated used visual enchantment (plot graphs in Foobar).

Best regards.

 

[trl]

The newer ASx01 series is primarily distinguished by its digital inputs, which add to their market value.

Worth mentioning that ASx01 series has a headphones amplifier inside, while the other series not (just couple of plain resistors tied up to speakers out). This can be seen in the schematic from the first pages of this thread.

 

[zepplock]

I'm surprised that these Yamahas don't have any circuit protection if speaker wires are shorted. Isn't it a must for any amplifier these days?