PLDS

Novice Member
Hi! I have a Denon AVR-X1300W amplifier along with a pair of Klipsch bookshelf speakers and a Klipsch R-100SW subwoofer.

I just into a new house and upon setting up my system, I notice that my subwoofer is producing a low volume bass like sound (I suppose that's what humming is).
If the subwoofer is just plugged in (it uses a two prong plug) with no other cable attached, the hum is barely audible (you have to put your ear next to the sub to hear it.
If the LFE cable is then connected to the sub, the humming becomes louder. If the amplifier is then turned on, the humming becomes even louder. Turning the gain and low pass knobs up or down affects the humming, more gain - louder humming, more low filter - louder humming and vice versa.

I have searched all over the internet for solutions and have tried the following with no success:
I have tried a ground loop isolator on the LFE cable, no change.
I have disconnected or other sources from the amp except for the sub and speakers, no change.
I have tried different LFE cables, no change.
I have tried different electrical outlets around my house for both the sub and amp, also tried plugging them in on the same power strip, no change (amp uses three prong plug).
I also disconnected the ground cable from the electrical outlet where my amp is plugged in, no change.
Unplugged my fridge and switched off two transformers that power my garden lights just to be sure (they are not on the same electrical line), no change.
I don't have satellite TV or cable TV, just plain old aerial and that is only connected to my TV which in turn is only connected to the amp via an optical cable.

I was thinking of trying an AC cheater plug, but to my understanding, that's the same as disconnecting the ground cable from the outlet, which I tried already (correct me if I'm wrong).

Any help would be greatly appreciated, thank you!
 

CountachLP5000s

Active Member
I had this on some old subwoofers and changing over to a Tacima CS947 fixed the issue. Not saying it will fix yours, sorry, but just an idea for you.
We live in a maisonette and the mains power is split inside the Butcher's below us; hence, numerous electrical compressors may be affecting our mains (don't know) haha.
 

jwlawler

Active Member
Is the hum a very steady low note? Not erratic or crackly? The mains, assuming you're not in the US or Canada, is 50Hz. As a note, this is close to the lowest note of a bass guitar or double bass; it's between G and G# on the E string.

The barely audible hum with nothing connected was probably always there but you never listened so carefully. If it has got worse then the capacitors in the power supply may be wearing out. I had this on a 12 year old BK Gemini I. BK repaired it for £45 including return shipping. It's as good as new. However, this does not seem to fit your symptoms.

Did it get handled roughly in the move? If a connection has come loose inside, it might explain it. The connections to the LFE input would be a suspect. I don't know your sub but mine has two: L and R. One is labelled mono and is normally used if you have a single input, you could try the other. However, if one is damaged then probably both are. Mine also has what is called a high level input which connects to the speakers. The LFE input is preferable but this would be an interesting diagnostic step. Don't connect the speakers to the normal input. Only do this if your sub, like mine, is designed for it. Read the manual.

You could look inside but this is in the territory of: if you don't know what you are doing then don't do it. Try calling the manufacturer, I did. I considered attempting my own repair but I called first. At just £45 for the repair, it did not seem worth doing myself.
 

CountachLP5000s

Active Member
I had this on some old subwoofers and changing over to a Tacima CS947 fixed the issue. Not saying it will fix yours, sorry, but just an idea for you.
We live in a maisonette and the mains power is split inside the Butcher's below us; hence, numerous electrical compressors may be affecting our mains (don't know) haha.

Right I have no idea why this is... my old REL Storms hummed and the Tacima almost removed the hum. My old REL Stratas have had (directly under sub) a 41dB hum at exactly 50Hz. This has been there for ages. Only audible at listening position when it is really quiet! This weekend, wait for it... I removed them from the Tacimas and plugged them in the wall. The hum has gone hahaha...
 

PLDS

Novice Member
Hi to everyone and thank you very much for your help. After trying everything mentioned above, it turned out that it was just the cable. I tried an old 5 meter rca I had lying around and it worked properly.

Once again thank you!
 

The latest video from AVForums

Podcast: Samsung HW-Q800A Soundbar & Rotel Michi X3 Reviews + TV show and Movie News & Reviews
Subscribe to our YouTube channel
Support AVForums with Patreon

Top Bottom