Thanks Rambles, Leelo and Gibbsy for your time in replying to my question. I will try to answer your queries here. excuse me for a long reply and please ignore that parts that look irrelevant.
I think I didn't explain my setup clearly. I have Focal Chorus 726 for front speakers and Focal Sub 300P. The sub can be configured (I guess like most other subs) in 3 different ways -
1. High level input from Amp and front speaker output from Sub
2. Low level input from Amp
3. LFE input from Amp
With high level input (as per the sub's manual), the front speaker (R&L) output from the receiver are connected to the high level input (R&L) of the sub. The speaker output from the sub will be connected to the right and left front speakers. In this case, the Amp will have sub/LFE turned off and will be sending the full frequency spectrum for front channels to the sub. The sub will have 80Hz crossover setting and so will send everything above 80 to the front speakers.
Please refer to page 17/18 in the manual to see what I'm referring to
https://www.focal.com/sites/www.foc...talog/document/sub300p-user_manual-notice.pdf
earlier I have also tried the LFE input to sub and front channels connected directly to the Amp (crossover set to 80Hz in Amp for front channels) but found the high level input setup more enjoyable especially while listing stereo music. Either way the Amp has failed in both setups at different occasions and so this may not be a point of interest for the fault? But I most welcome your suggestion on an optimal setup.
I'm not using ARC and I just adjust channel volume levels based on the movie content since they are not the same for different movie sources.
To give some timeline, the Amp and speakers were bought about 3 years ago. The Amp was an ex-demo model I bought for a discounted price and it first failed in about 3 months. The dealer fixed it for me and it failed again in another 2-3 months. I asked the dealer at that time if it was anything to do with the speakers/wiring I'm using and he told me that even if it was the case, it shouldn't fry the board and the Amp should be able to protect itself. He spoke to the distributor and arranged me a replacement Amp. This went on well for good 2 years and failed in December last year. In the meantime, the dealership was bought by another company and they are not accepting it as part of warranty and do not believe that its a fault with the Amp. Like Leelo says with Yamaha, I too was expecting that the protection mechanism must be something that we can reset ourself rather than spending for repair. I tried to raise a case with Anthem directly through their website asking why such an expensive Amp would fry its components and if they can provide any firmware update but they just said that its an external fault and they can't do much about it.
All the 3 times when it failed, the issue occurred while I was watching an action sequence in a movie and so the sound level was going up and down across the channels. I listen to music like 2-3 hours a day with the front channels and in fact with much louder volume than movies but never had an issue. When it failed last time, the unit was extremely hot and I left it to cool down overnight. In the morning, it was powering on and I was able to listen to music for a good couple of hours. Later in the evening, I tried to continue the movie again and it failed at the exact scene and never recovered:-(
The Amp has gone for paid repair and I will upload the repair report to see if you can find any clue there. I will receive it sometime next week and in the meantime will try to check the wirings, add a cooling fan and replace the rear speakers with KEF. Then I can try to play the same action sequence again and if it goes into protection mode again (which should hopefully not fry the board), I will go for adding the power amp or just decide to use the setup for listening to music and buy a Yamaha for watching movies
Thank you very much guys for your patience and time.