Yes, it could very well be the A820's amp section and I have been careful to point out that this is not an indictment of all AVRs. The Revel M20 bookshelf are not particularly efficient nor easy to drive:
View attachment 24056
My comparissons were at relatively low voltage which should not have exceeded a couple of watts driving the M20's.
Here are the Specs from Yamaha:
RX-A820 AV Receiver
Amplifier Section Channel 7.2
Rated Output Power (1kHz, 1ch driven) 160W (4 ohms, 0.9 % THD [European Model]), 130W (8 ohms, 0.9% THD)
Rated Output Power (20Hz-20kHz, 2ch driven) 100W (8ohms, 0.09% THD)
Maximum Effective Output Power (1kHz, 1ch driven) (JEITA) 160W (8ohms, 10% THD)
Dynamic Power per Channel (8/6/4/2 ohms) 140/180/210/250W
Nothing in the specs indicate that there should be any problem driving the M20s at low to moderate listening levels. I suspect nothing in the A860 specs indicated that AH would measure poor performance.
If SV did the review, they would have measured 1K sweeps into 4 and 8 ohm loads and I suspect there would be no problem. The student is tought the tests. Some implementations are created to squeak by.
AH detected issues with the A860 but others did not. That is the problem with specs. After a while, manufacturers become known for over-designing and therefore their spe
I had a similar experience when my brother-in-law was driving his B&W CM10's with a Pioneer Elite SC-07 Class-D (ICE) AVR. I did not like it and we replaced it with Outlaw M2200 mono-blocks directly driven by an Oppo BDP-105. Later I found that AH/Gene found issues when driving 4 ohm loads.
The good news in these cases is that if the A820 is like the A860, then it is possible to measure issues with products that have real-world performance issues. There have been amps that AH measures well did not fare as well in their listening sessions. This has also occurred
- Rich