Hello friends,
I ran into a weird & annoying issue and wanted to share my troubleshooting experiences and solution here in the hope to help other Audio enthusiasts! =)
TLDR
Connect your active Sub to the second LFE port of your Receiver if you experience similar issues. Don't forget to configure the Receiver to use that port too, it might solve your problem!
Full story
I ran into a strange issue with my Receiver yesterday. I'm using a Denon X4500H for home theater purposes with a 5.1.4 Atmos setup that I've been using with the same speakers for years without issues.
Yesterday however, the feared Denon 'protection mode' (Receiver turns off and a fast blinking red light is shown) kicked in after about 15 minutes into a movie during a 'spaceship leaving orbit' scene (quite loud). I knew about its existence, but never experienced it before. So I initially thought my Amp was simply getting too hot, placed a strong fan next to it and started the movie again; only for the protection mode to kick in again within 2 minutes. This time the Amp had a perfectly acceptable temperature, so I verified if my speaker cabling was still alright (it was) and concluded that my Amp was probably overloaded due to the high volume. I turned the sound down by a LOT and the issue went away. Turning the volume up immediately caused the Receiver to go in protection mode again within minutes.
I then tried to access the Denon protection status log (procedure below), but unfortunately my Receiver simply boots after giving an 'enter' on option 2 'protection', even after a factory reset! >.<
So I sighed deeply and decided to test everything myself by disconnecting all of my speakers and play the same ship leaving orbital scene over and over again while reconnecting my speakers pair by pair. Long story short, it turned out to be the LFE connection to my active subwoofer, which took me completely by surprise. I mean, since it has its own power source I never suspected it to be even possible for my Receiver to break on this. But I've tested this about 5 times and I can reliably reproduce the protection mode during the orbital scene with my subwoofer on.
Once I turn the volume of the Sub all the way down, there is no issue. So it only triggers the protection mode when the Sub actually does something with the signal by producing sound. To rule out that either Sub-vibrations (I have a big Sub) and/or internal Subwoofer issues were causing the issue, I connected my Sub to another receiver (connected to my PC) and played the same movie scene on both my PC and my home theater set at the same time in the same room. Both of my setups survived the Orbital scene multiple times, so my suspicions went back to the X4500H Receiver. And of course, once the sub was reconnected to it, the issue immediately resurfaced.
That's when I had the idea to connect the Subwoofer to the second LFE port of the Receiver, configure it to use both LFE port (apparently can't just select LFE port 2) and this solved the issue completely! I ran the entire movie and the Receiver kept working fine! =) So my best guess is that the circuitry that links to LFE port 1 got damaged somehow and causes the Receiver to hit protected mode once its being used. I haven't opened the Receiver up yet to verify this, but once I do I'll make sure to post it here. =)
So that's my story! I hope it turns out to be helpful in the future! =)
To access the Denon protection status log, credits to Peng!
1) Turn off the receiver.
2) Press and hold the buttons "ZONE3 SOURCE" and "STATUS" simultaneously
3) While still doing 2), press the power button to turn on the receiver.
The receiver would start up and you will see a menu with choices 1 and 2, select "2. PROTECTION" using the cursor up/down buttons, and then press the "ENTER" button to confirm.
After that you can press the "STATUS" button in protection history display mode to see the protection history such as the following:
L2: AS0 - this indicates a short circuit occurred between the speaker terminals.
L2: DC - this indicates DC output of the power amplifier is abnormal.
L2: THERMAL E - Abnormal heat sink temperature
L2: CURRENT - Overcurrent in power amp. 