Any idea whats wrong with my amp? Keeps cutting out!


Standard Member
I have this really old Denon PMA 520, it had been left under my bed for a while and was fine the last time I used it months ago. Now ever since I got it back out (this is over the space of a few weeks), it keeps cutting off and then turns back on instantly. Basically the power button is one of those push in buttons, that once the amp is on stays in unless you press it again to turn it off. When you turn it on, it by default goes to the "Tuner" channel, I then select "AUX 1" for my PC but then it switches back to tuner by itself (after I start playing some music), I'll then press AUX 1 and it switches again soon later, this is an endless cycle, sometimes it takes a while, sometimes it does it all the time. I have noticed (but it could be a coincidence) that this seems to happen more often when a bassy part of a song is playing, which obviously requires more power. I'm pretty sure its actually turning off and back on again instanly rather than switching channels. My friend came over the other day and had a look inside it, there was nothing obviously wrong, it wasnt full of dust and the fuse hasnt blown (although weirdly it looks as if it has been professionally wrapped in silver foil!!) and the amp is not overloaded (have tried basic speaker setups). Finally, if you keep pressing AUX 1 every time it cuts off, if you do it enough times the amp usually then stays on. Any ideas? Thanks.
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Distinguished Member
How much dust accumulated under your bed, and therefore inside the amp?

If it is filled with a thick layer of dust, you need to clean it out.

Next make sure all the interconnecting wire are in good shape and are making good contact. Start with the speaker wires. Then check the interconnect (PC to Amp) wires to make sure there are not opens, short, or stray strands of wire.

Next, you might have to accept that the amp is about ready to give up the ghost.

Try disconnecting the PC and see if the amps turns on and stays on.

Try driving with another source. The same cable the connects the PC to the amp can be used to connect an MP3 player to the amp. Try that and see if you still have problems.

It it switches to 'Tuner' can we assume the amp has a tuner? If so, play the radio with the other inputs disconnected and see if you still have the same problem.

Possibilities -

- Bad wiring, meaning either bad wire or operator error in connecting the wires.

- Ground loop or some similar electrical incompatibility between the PC and the amp. If it is a laptop, try running it on the battery. If it is a Desktop, try connecting both the amp and the PC to the same electrical outlet.

- Are the power cords you are using to power the PC and the Amp the original power cords that came with them, and can we assume these are polarized plugs that can only go in one way?

It is a difficult question to answer. Personally, I would just turn the amp on with no speakers or inputs connected and see if it behaves itself. Then connect the speakers - carefully - and see if the problem occurs. If you can have amp and speaker with no problems, then connect the PC and see if the cause the problem.

ALSO KEEP IN MIND, when I say connect this and disconnect that, it is ASSUMED that the amp IS POWERED OFF when these changes are being made. Never connect or disconnect anything to an amp that is turned on.



Active Member
My friend came over the other day and had a look inside it, there was nothing obviously wrong, it wasnt full of dust and the fuse hasnt blown (although weirdly it looks as if it has been professionally wrapped in silver foil!!)


Have you owned this amp from new, or did you buy it second-hand?


Standard Member
Thanks everyone for the responses, I think I have worked out the problem and it was a really weird one. I tried many of the suggestions above and was still getting the problem, so I put it away and was ready to give up. I then decided to have one last go, plugged it into a different socket in my room and the problem vanished. Before I had been running it on one of those PC (belkin) 4 way surge protector extension leads (as it was next to the PC), but after switching it to a regular 4 way power extension, the problem seems to have disappeared. I have been using it all day with no faults at all. Its weird that the extension lead could cause this issue.

The amp was not mine from new, it belonged to a friend originally and I have no idea where he got it from, the silver foil is also very weird though.

So thanks everyone for the advice, I think its sorted now.

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