Yamaha RX-A8A (Japanese website)

[Macfox]

For the model below the A8A, the A6A it's $3,699 Australian. That's about $500 Australian below a Denon 4700H. I'm considering the A8A, A6A or the Denon 4700H. But I'll wait for reviews on the new Yamaha's. The 4700H is fairly well reviewed and well known. I feel it will take quite a long time before it's known about these upcoming Yamaha's. I'm not sure I can wait that long. Lol.

Strange. Here in the Netherlands, the RX-A6A @ €2749 is priced above the 6700H @ €2699 and the RX-A4A @ €1679 above the 4700H @ €1549.
Also, the 4700H seems to be around 3499 AUD, which is still ridiculously expensive compared to Europe, where at the current exchange rate the price is below 2450 AUD.
On the other hand, the RX-A6A is priced @ 4330 AUD here...

 

[restorer-john]

I have no idea why Yamaha would even list such a specification.

Yamaha should be ashamed. I am ashamed for them.

I'm not sure what those T03P devices are, they look like they have 5 pins from that rendering above. That suggests they are an integrated driver/opt package or integrated darlington perhaps. There's definitely no separate pre-drivers in that pic.

Overall, the power stage block looks really cheap and nasty.

 

[restorer-john]

They may be using Sankens like these:

 

[Doodski]

They may be using Sankens like these:

View attachment 131261

I've handled many darlington transistors but these are a new breed for me.

 

[restorer-john]

I've handled many darlington transistors but these are a new breed for me.

They have an integrated thick film emitter resistor which you can use, or not use. The rendering pic above shows ceramic emitter resistors on the Yamaha board. If they are anything like the thermal track transistors from Motorola/On Semi, they will be a disaster for reliability IMO.

 

[oupee]

It will probably be Sanken. The Yamaha RX-A2A also uses Sanken.

 

[Macfox]

Yamaha should be ashamed. I am ashamed for them.

I'm not sure what those T03P devices are, they look like they have 5 pins from that rendering above. That suggests they are an integrated driver/opt package or integrated darlington perhaps. There's definitely no separate pre-drivers in that pic.

Overall, the power stage block looks really cheap and nasty.

Let's hope they haven't skimped on (pre) amplification in order to overspec on specsheet stuff like DAC's

 

[Macfox]

It appears the heatsinks are very lightweight and of a inexpensive construction. I expect more for the power capabilities of this model.

To me, the design somehow doesn't make sense. The thing weighs 20+ kg, indicating a big heavy power supply. However, the heatsinks seem relatively cheap and low mass. What is a big power supply useful for if there is no thermal capacity to get rid of the associated heat? It doesn't seem to be a class D design but a classic class A/B one. Also, Yamahas usually run cool, meaning they either have low multichannel power or extraordinarily good heatsinks. The latter doesn't seem to be the case.
The question then raises: what good is a big power supply if multichannel power is limited? Dynamic and/or stereo power doesn't need a huge power supply.
Or is it simply a case of a heavy chassis?

 

[tecnogadget]

Im disappointed too. At +$3000 I expect better construction, toroid transformer, better heatsink, more “substance”, etc. My DSP-Z9 was $5k/6k on 2004/2005 and once you open the lid, its a TOTL feast with pure high quality components, even exoteric ones.

I suspect that COVID global crisis + remote work at home + global chips/hardware supply shortage...will yield to another generation of AVR’s that are not up to the task.

I can’t get why no manufacturer gets to the bottom of it. To produce the first series of AVR’s that scores full Soccer or Golf Panther.

 

[AdamG]

Im disappointed too. At +$3000 I expect better construction, toroid transformer, better heatsink, more “substance”, etc. My DSP-Z9 was $5k/6k on 2004/2005 and once you open the lid, its a TOTL feast with pure high quality components, even exoteric ones.

I suspect that COVID global crisis + remote work at home + global chips/hardware supply shortage...will yield to another generation of AVR’s that are not up to the task.

I can’t get why no manufacturer gets to the bottom of it. To produce the first series of AVR’s that scores full Soccer or Golf Panther.

The Denon 8500h got the best review rating to date. https://www.audiosciencereview.com/forum/index.php?threads/denon-avr-x8500h-avr-review.15266/

 

[peng]

They may be using Sankens like these:

View attachment 131261

I suspect whatever they used, it would be comparable to those in its predecessors but you never know..

According to the older Yamaha top RX-A models such as the RX-A3050 and A3070, the output devices are the Darlington pairs, the Sanken STD05P and STD05N. However, in the SMs, they show STD01P/STD01N in the pin connection diagrams page but on the replacement parts list and the schematics they did show the STD05P and STD01N. I wonder why that is, any idea?

I googled but could not find the datasheet for the STD05P/N (could only find one for the STD01 and 03P/N, do you know a better way to find it?

 

[Macfox]

The Denon 8500h got the best review rating to date. https://www.audiosciencereview.com/forum/index.php?threads/denon-avr-x8500h-avr-review.15266/

True, but older even more high end flagships like the AVC-A1XVA haven't been tested. They might test better or worse. Build quality and components usage seemed to be significantly better though. On the other hand, that hasn't always proven to lead to better measurements, so who knows what they might be.

 

[Beershaun]

It appears the heatsinks are very lightweight and of a inexpensive construction. I expect more for the power capabilities of this model.

i expect this heat sink design benefits from much more surface area to transfer heat to the air compared to a solid aluminum block. Both sides of the sheet metal ribbon are exposed to the airflow. Gives you more surface area in the same space. It’s a common and effective design in most radiators. We don’t know the calculations of course but I wouldn’t necessarily worry about the heat sink design unless the reviews tell us otherwise. It will likely reject a lot of heat. Which means it’s doing it’s job.

 

[restorer-john]

i expect this heat sink design benefits from much more surface area to transfer heat to the air compared to a solid aluminum block. Both sides of the sheet metal ribbon are exposed to the airflow. Gives you more surface area in the same space. It’s a common and effective design in most radiators. We don’t know the calculations of course but I wouldn’t necessarily worry about the heat sink design unless the reviews tell us otherwise. It will likely reject a lot of heat. Which means it’s doing it’s job.

Yamaha have been using this exact cheap and nasty heatsink since the mid 1980s on everything low-mid range. They must make it themselves as it's been a staple on all their gear and nobody else uses it (for good reason). They have only ever used quality extruded large heatsinks on the absolute TOTL 2 channel gear. AV gear gets two piece crimped crap like this. There is absolutely no way each heatsink is remotely adequate for up to what looks like 6-7 amplifiers on one side and 4 on the other (hard to tell) of class AB amplification running at its rated 150W@8R/ch- that's fantasy land.

Here's a better interior shot:

Inside an AS-2100 2 channel amplifier.

 

[Macfox]

i expect this heat sink design benefits from much more surface area to transfer heat to the air compared to a solid aluminum block. Both sides of the sheet metal ribbon are exposed to the airflow. Gives you more surface area in the same space. It’s a common and effective design in most radiators. We don’t know the calculations of course but I wouldn’t necessarily worry about the heat sink design unless the reviews tell us otherwise. It will likely reject a lot of heat. Which means it’s doing it’s job.

A design with many folds is better for heat sinking. However, cast iron has a heat conductivity of around 50 w/m K. Aluminium on the other hand has a heat conductivity of around 235 w/m K, with alloys having lower conductivity but still far above cast iron and steel alloys.
In other words: you need much more heat sinking area to begin with when using cast iron, which is the reason it's usually reserved for the lower end models.

 

[peng]

D+M uses similar heatsinks in their lower end AVRs too. I think the heat sink efficiency depends on the overall design, not just folded fin vs extruded AL alloy types though it does seem cost might have been a key factor too as Yamaha does use the more heavy duty looking extruded type in their home theater 11 channel power amps, similar to those use in the Denon and Marantz flag ship AVRs.

 

[Beershaun]

are all the channels class A/B? I couldn't find anything on the website and am not qualified to tell by looking at the picture. I agree its definitely cheaper. do these lower end Yamaha amplifiers have a history of failing due to heat?

 

[Macfox]

are all the channels class A/B? I couldn't find anything on the website and am not qualified to tell by looking at the picture. I agree its definitely cheaper. do these lower end Yamaha amplifiers have a history of failing due to heat?

On the contrary: they are one of the coolest running and most reliable receivers. The way they do it though, is not by using better cooling designs, but by limiting power for multichannel and low impedance speakers.

 

[Beershaun]

On the contrary: they are one of the coolest running and most reliable receivers. The way they do it though, is not by using better cooling designs, but by limiting power for multichannel and low impedance speakers.

Ok. so it's a design choice to limit the amp's heat requirements through other means. Cool. So we should nash our teeth about the limited power and impedance requirements.

The 2 ch power is 150wrms 0.06% 2ch driven is comparable to the denon x6700 (140w 0.05% 2ch). Which seems like the closest competitor from a price/power/channel count standpoint. The Denon though is ~$300 cheaper and promises 80% rated power when all channels driven.

It also seems to promise better power and distortion at 6ohm loads
Power Output (6 ohm, 1 kHz, 0.7% 2ch Drive)175 W

But also no 4ohm spec on their website.
https://www.denon.com/en-us/product/av-receivers/avr-x6700h

So they don't seem to be winning on price, performance, quality or features compared to Denon...Did I miss something that differentiates the Yamaha? Is it just XLR input? Maybe their pre-amp section performs better at 2v than Denon? They don't have much information on THD+N @2v for the pre-amp specs.

 

[gonzoucab]

Im looking this for the double ES 9028 DAC. if it gives good SINAD and give me XLR to integrate to 2.1 and enough power for sorround speakers, its s buy.

ES9028 is much better than the DAC Denon/maratz uses, i hope they do it right