... good question kiteboy dave!
Do we assume you are going from ipad to amp then to sub, the amp is then connected to speakers which play most of the music and the sub doing just the bottom end or low frequencies), if you don't have any music from the amp its probably nothing wrong with sub and its upstream as in the pad, cables or amp that is the problem.
Another question, if you connect to Sub direct to Ipad, what plays the rest of the frequencies, another amp? If you can't hear this music, just check by connecting the ipad direct to this amp. What we want to do is identify where the signal is stopping.
A few things to try:
- check music source (ipad) is outputting music, easily test this by throwing some headphones in, this way you check the volume level is up enough too.
- swap the interconnect cable from ipad to amp, get another one if possible.
- check amp is on and you have the correct source selected.
- check if you have the speakers on as in some amps have speakers A or B, make sure they are selected on.
- if you don't have another cable, try to connect ipad to another device such as a TV, test if the cable is good and you hear stuff normally on the TV.
- make sure the plugs are clean and not corroded ie RCA sockets on Sub are clean ect too.
The noise your getting can be a grounding problem, as in the ground wire or music signal return wire might be broken but since the left and right signals are still there, you get a bit of sound.
If you have been aggressive or plug in and out alot, the sockets in the sub might be crook or a dry solder join internally which requires it to be re-soldered.
Basically check everything else before you blame the sub.
If you have been connecting the ipad directly to sub, you may have overloaded it. If you had headphones in and at normal volume level then connected it directly, this can mean its had high level of signal input which means it may have driven itself into protection mode. Do you connect ipad directly in to SUB?
Check these things and get back to us.
cheers,
Robbie