Velodyne CT-100 when switched on connected to nothing else makes a very loud humming sound & the speaker is pushed outwards

The loud humming could be caused by a cable on the input that is not grounded. It could also be caused by some sort of power supply failure.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/david_29ad5d1dd86564b0

Get the manual.

http://www.retrevo.com/support/Velodyne-CT-100-Subwoofers-manual/id/866dj578/t/2/

The source plays a part in this, too. Get ITS manual.

If I understand this correctly: with NO input or cable attached it hums; with an RCA cable attached it works. (What does 'some' mean in this regard?)

You say that connecting the RCA cable improves its sound. That tells me you're supplying a ground through the RCA cable for stray voltage in the sub.

It seems there may be a basic power issue if it hums with no input. Sometimes a given power source in a home may be wired differently than others or may insufficient grounding, which can result in hum. Try reversing the sub's power plug or move it somewhere else.

Since the sub contains its own electronics it is also susceptible to strong external magnetic fields. Keep it and any signal cables leading to it some distance away from other electrical devices like TV's.

You can go buy a audioquest SUB-X subwoofer cable with a additional ground wire on it an connect the ground cable to the ground slot of the receiver an the other end to a screw on the sub or into one of the high output terminals on the woofer if it has them an this will take that humming sound right away but the cable is around $90

One of two things may be going on.

The amp has a fuse mounted on the PC board. The fuse may be blown.

The speaker may be bad. that may have blown the fuse.

You can test the speaker with a "D" battery.
Take the amp section out of the back, disconnect the speaker leads.
Touch the speaker leads to the poles of the battery. it should make a little thump and the cone should move freely.

Contact Velodyne for service.

humming sound when on is usual if the volume is turned up.
humming sound the same when on or off could be transformer plates fluxing.
if loud recommend replacement of power supply.
if ok then recommend unplugging the device after use.

Amplifier problem.

You will need to contact Velodyne for service.

Sounds like a dead amp. You could check the xformer output and the amp IC's with a VOM.

These amps do not cost a lot, about $40.00. and are easy to replace.

Contact Velodyne

hi, on the onkyo check the speaker out , each channel has its own -ev & +ev, each speaker to its appropriate polarity, thats it, its simple.. let me know

Bad amp

Contact Velodyne