Yamaha A-S701 Stereo Amplifier Review

[BlueMax]

My sources apart from the Ultra are Oppo BDP-105D, Yamaha CD-S303, Apple TV box and TV decoder box. No analogue sources in this setup.

I don’t use subwoofer since Harbeth SHL5 XD have plenty of bass for music that I listen to and I don’t apply any DSP room correction in the Ultra since bass from my speakers in my room is OK and I don’t believe DSP is any good for frequencies above Schroeder.

Yes, I find volume control and remote on the Yamaha to be very convenient to use, especially that I control my Yamaha CD player from the same remote.

PS I have another Harbeth based system (M30.3 XD2) with analogue sources too. I use QUAD 34 as phono preamp and some Elite mono power amps there but I’m just thinking about getting a used Yamaha A-S1200 for that system and use its in-built phono preamp for convenience and a little bit of luxury.

 

[ZolaIII]

@BlueMax let's just say I DSP a lot, it's not true DSP isn't useful above shoulder and I tried to explain to you how bass is a live thing. You do need limited accustic treatment to focus highs and even mids a bit, DSP can't focus such diffusion. I moved mostly to use server and PC with JRiver as its AV setup and control most of the things including volume trough phone app but that's me and it's 2.2 setup. To get automatic loudness compensation on the amp you nead to go with higher end Yamaha R-N (2000A) and it still ain't neither as good as proper ISO 226 2003 or 2.2. I use EBU R128 on sources I have and synced DX Show for movie's (it's a beemer setup) but some input sources which are far off still need quick adjustments. I try to use as least remotes I can (and I can with a phone and WiFi outlets for sub's). Follow strict I/O when I can (even setup is far from complied as it can be).

 

[bob77]

I'm truly interested in this amp to drive DALI Oberon 5 loudspeakers.
I have got an old Yamaha Pianocraft E600 paired with those speakers and I typically listen with volume knob set lower than 9 o'clock. Hardly ever I turn it higher than 11 o'clock because then it is really loud and neighbours might be upset. Pianocraft doesn't have loudness, so for my typical volumes I need to use bass knob.
I wonder if it makes any sense to upgrade Pianocraft amp to A-S701. Will I hear any difference?

 

[Ruediger]

I'm truly interested in this amp to drive DALI Oberon 5 loudspeakers.
I have got an old Yamaha Pianocraft E600 paired with those speakers and I typically listen with volume knob set lower than 9 o'clock. Hardly ever I turn it higher than 11 o'clock because then it is really loud and neighbours might be upset. Pianocraft doesn't have loudness, so for my typical volumes I need to use bass knob.
I wonder if it makes any sense to upgrade Pianocraft amp to A-S701. Will I hear any difference?

The Dali Oberon 5 are no difficult to drive speakers.

If you would hear a difference depends mainly on your sources in my opinion. The A-S701 is a superb amp capable of making a lot out of a good signal you feed it.

Don't expect too much of a change. But I would get the better amp nonetheless. I had a lot of Yamaha amps and in my eyes the A-S amps are real keepers.

 

[Mrtn77]

Hello all, I've been using my 6 year old Yamaha A-S701 to drive a pair of Ascilab F6B for the last week or two and I was surprised to find it cut all sounds out, with a blinking power light, when listening fairly loud (though not excessively so). The top of it was very hot, I assume it was overheating. It had never behaved this way before, though I'd listened at this volume often enough.
Another thing, perhaps more worrisome, is that the right channel is now much quitter than the left one. I've checked balance control, wiring, etc., nothing is amiss as far as I can tell.
The amp is seating in a rack with 4 centimeters of free space above it. I'd never felt this to be a problem before.
I've never touched the impedance switch. Should I change this ?

 

[ZolaIII]

Hello all, I've been using my 6 year old Yamaha A-S701 to drive a pair of Ascilab F6B for the last week or two and I was surprised to find it cut all sounds out, with a blinking power light, when listening fairly loud (though not excessively so). The top of it was very hot, I assume it was overheating. It had never behaved this way before, though I'd listened at this volume often enough.
The amp is seating in a rack with 4 centimeters of free space above it. I'd never felt this to be a problem before.
I've never touched the impedance switch. Should I change this ?

No impedance switch will lower output power (to prevent such). It's relatively low impedance (3.4 Ohms) and sensitivity speaker (about - 3 dB to average similar one's) that can pass mid field (2m) calibration at best and still recommendation is 200W at 4 Ohms amplifier (Yamaha comes close) with them or more. In W +3 dB is 2x power. High cut won't do much as impedance deep is from uper bass all across the mid range. Perhaps some Brunos more powerful regarding output power SoM power amplifier is what you need.

 

[JRob1125]

I've never felt safe with anything less than about 6 inches of clearance above my amp. I wouldn't be surprised if that what went wrong

 

[Randolf]

Hello all, I've been using my 6 year old Yamaha A-S701 to drive a pair of Ascilab F6B for the last week or two and I was surprised to find it cut all sounds out, with a blinking power light, when listening fairly loud (though not excessively so). The top of it was very hot, I assume it was overheating. It had never behaved this way before, though I'd listened at this volume often enough.
Another thing, perhaps more worrisome, is that the right channel is now much quitter than the left one. I've checked balance control, wiring, etc., nothing is amiss as far as I can tell.
The amp is seating in a rack with 4 centimeters of free space above it. I'd never felt this to be a problem before.
I've never touched the impedance switch. Should I change this ?

The flashing pattern of the power led of the A-S701 provides detailed protection information:

It also has a protection history of the last 4 failures. Unfortunately the A-S701 has no display, so the procedure to decode the information is pretty complicated. It it described in the service manual (e.g. on hifiengine).
If one channel is now significantly quitter and you have ruled out that this is caused by input or loudspeakers by swapping left and right channel cables, the unit is proably broken now and needs to be repaired.

 

[Spkrdctr]

It does sound broken and needs repair.

 

[Mrtn77]

So I tried switching the speaker cables from binding posts A to binfing posts B and, oddly, the amp is working fine now. I've also added a good 25 cm of clearance.
Both channels are now matched in volume and the amp remains cool to the touch when played as loud as I'm liable to go. What happened there ? Is this a temporary respite or a lasting solution ?

 

[Randolf]

So I tried switching the speaker cables from binding posts A to binfing posts B and, oddly, the amp is working fine now. I've also added a good 25 cm of clearance.
Both channels are now matched in volume and the amp remains cool to the touch when played as loud as I'm liable to go. What happened there ? Is this a temporary respite or a lasting solution ?

If it is permanent that speaker port A has problems (on one channel) and port B works fine than the problem might be located in relay RY101, which switches port A. Port B is switched by RY102. I would suggest to double check that port A is permanently broken and port B works fine. Both relays are located on the main board close to the speaker ports:

A visual inspection of the relays and soldering (check from below) might be helpful.

 

[Mrtn77]

If it is permanent that speaker port A has problems (on one channel) and port B works fine than the problem might be located in relay RY101, which switches port A. Port B is switched by RY102. I would suggest to double check that port A is permanently broken and port B works fine. Both relays are located on the main board close to the speaker ports:

View attachment 553214

A visual inspection of the relays and soldering (check from below) might be helpful.

Thanks ! Would a broken port A explain the overheating that the amp experienced ?

 

[Ruediger]

So I tried switching the speaker cables from binding posts A to binfing posts B and, oddly, the amp is working fine now. I've also added a good 25 cm of clearance.
Both channels are now matched in volume and the amp remains cool to the touch when played as loud as I'm liable to go. What happened there ? Is this a temporary respite or a lasting solution ?

The clearance helps for sure. Make sure there is space above but also to the sides, so air convection can work. Some amps have recommendations in the manual as per their thermal design.

With the overheating problem watch out for external issues. Bad fit on the speaker cable/banana, poor connection to the terminal, corroded banana or cable, bad fit with the binding post screws. However you fit the cable there. Also look at the cable itself if there is a problem. When not using bananas or other endings with isolation, be very careful not a single wire is lose somewhere.

 

[Roland68]

Thanks ! Would a broken port A explain the overheating that the amp experienced ?

To me, this all sounds like a short circuit at the speaker terminals or in the cables. However, the issue could also be internal, involving the relays or the A/B switching mechanism.

Do you happen to have stranded speaker wire connected to the amplifier terminals, or have you clamped the speaker wire directly into the terminals?