No output from any inputs. Before it quit, we heard low, slow buzz out of speakers. Next time we turned it on, silence.

Possible shorted speaker wiring or a shorted voice coil in one of the speakers.

Things to check:
1. With your multi meter, measure from left ground to right ground. What do you get? Measure from each input ground to chassis. What do you get there.

2. Get or make a pair of shorting plugs. Plug those into the inputs. Power on. Hum there or gone?

3. Turn the pre-amp on. Connect. Level of hum change with preamp on?

4 additional information. How efficient are your speakers? This is a big amp, high-efficiency speakers may show some noise, while low-efficiency speakers won't.

A trip back to the shop may be indicated, too.

RX represents "receive" This indication will be present whenever the speaker is producing audio. The "buzz" you're talking about is probably static, and is technically audio from the speaker. To silence the "buzz" adjust the squelch just until the speaker falls silent. The RX indication should be off at this point.

It is important to note that the squelch is designed to keep the speaker silent until a signal is detected. You adjust the squelch based on the level of static at a particular time and at a particular location. The static level may change depending on those variables. If you adjust the squelch well beyond the point that the speaker is silenced, you may not be able to hear transmissions or calls to you unless the caller's transmitter is physically close to you. This is why the squelch should be adjusted only until the static is stopped and the speaker is silenced.

I hope this helps and good luck!

You've made a statement, please give full information if you would like help. Is the buzz heard from the speakers or the mixer? Do you get normal sound too? Is it there with no input? Does it change with the output setting? Help yourself to get help and let us know properly what's going on.

If it buzzes when you have no inputs AND no output leads connected, there is a problem with the power supply... HOWEVER if you have used UNBALANCED output cables instead of the REQUIRED TRS BALANCED output cables, it is possible the noise is being driven backwards and that is what you are hearing. Note that at full gains, there often is a tiny bit of noise, usually hiss. Also make sure the supply is powered from the SAME receptacle as the equipment this drives such as an amp or powered speakers.

I was trying to find an owner's manual or picture of the rear panel of the sub, but had no luck. The subwoofer is a powered type - or "active" speaker. This means it has a built in amplifier. These active subs usually provide for one or both "low level" and "high level" inputs. Low level signals are usually carried by shielded coaxial cables and have RCA type plugs on the end. The low level is also called "line level". This is an un-amplified signal that might be heard on cheap earphones - but that's about it. It is similar to the output of a tape deck, DVD or phonograph. These signals require an amplifier to be heard. If you have a sub woofer output on your receiver or amplifier, you could run a patch cable between the low level input on the subwoofer and the subwoofer output of the amp or receiver. You receiver or amp may call this output "low frequency effects" or similar. The front and rear speakers would then connect directly to the receiver or amp's corresponding connections.

If you lack low level outputs on the amp or subwoofer, you'll need to run speaker wires from the amplifier or receiver's front left and right speaker output terminals to the subwoofer's high level input terminals. High level signals are speaker connections or amplified signals. These are typically connections that accept bare wire connections. The front speakers would then connect to the subwoofer's front left and right speaker output terminals. The rear speakers connect to the amplifier.

I hope this helps - and good luck!

It probably buzzes all the time, you just notice it when it is outputting little volume. Check the cables for loose connections or replace them with other cable as a test.

sounds like bad audio pcb if buzz comes thru
the speakers,

Your problem is quite simple. The low input is for feeding a lead straight from the output of your receiver IE sub out and the high input is for connecting the sub directly to your speaker output where the alternative is not possible. Hope this helps

I would not think the speakers are defective but rather faulty capacitors in the power supply circuitry if the TV works good for some time.