Sub Hum recently my Tannoy TS10 started to hum. I have read up on ground loop problems. If the sub is powered on by itself there is no hum, it is only when I connect the sub cable to the amp the hum starts. Playing music/dvds the sub is unresponsive and just sits there and hums. If I turn the gain up the hum gets a lot louder until it will try and bounce the sub off the tiled floor. Things I have tried. New cable from amp to sub - no luck Different power cable - no luck Cutting the earth off the power cable - no luck unplugging each component one at a time including antenna - no luck. At wits end, can only think it may be the internal power supply has lost it's earth

Hum is tough. It is often caused by quite a variety of things. First, address the basics:
1. Make sure that none of your signal cables run near to power cabels.
2. If possible, feed all power from the same receptacle.
3. If your plugs are not polarized, try reversing one at a time.

If none of those basic checks uncovers your demon, verify the path of the noise by disconnecting the signal from the preamp at the input to the sub. If is still hums, then look closely at the power feed to the sub, More likely, the hum will stop (along with the music.) In this case, try breaking the shield ground at the sub input (e.g. with a ground isolation adapter.)

You should also confirm that the hum is limited to the sub. Subs tend to exaggerate hum because playing signals in the 60Hz is their forte. So with the sub turned off and bypassed, listen for the hum in your main speakers. If it is there, too, then start checking your sources. Remember, even a source device other than the one selected for play could be the source ... completely disconnect each source at the preamp to track it down.

if you have a hum, then your fuse is ok.

you have a ground loop issue you could purchase a ground loop isolator, jensen makes them for about 40 bucks.I have discovered that if you have cable tv, unplug the incoming cable in your cable box and see if hum disappears.

I would replace the largest electrolytic capacitor(s) in it, these are known for causing your problem.

Check that it properly grounded so that you don't have "ground loop hum" and that you have no power cords crossing other connections.

Neither the amp or the sub have grounded power cords.

I have discovered the ML Dynamo takes about 30 minutes to switch to standby in auto mode.

With speaker level inputs connected to the Onkyo A807 amp, both units powered from the same wall outlet, Dynamo sub on Auto, the sub hums for about half an hour after the Onkyo is switched off, then the sub goes quiet. Not so good.

I connected a bonding wire between the two units on 3_7_09. If I smoked some old audio gear I could just look at that as an opportunity, right?

Works fine. Now I have the ML powered from the wall and working normally.

Rita's Vintage Audio Repair is a Bob Carver Company & can repairs & updates Subs at a reasonable cost try calling them.

A few more questions-
Does the sub hum without anything plugged into it except for power? If it makes a real loud hum almost a squeal then I think the rca cable between the receiver and the sub is dead shorted and needs to be replaced. If it's more of a low level hum, then it's a ground hum caused by many things, ie........the receiver and the sub being on different power circuits in the house.......sometimes diconnecting the cable tv feed as it enters the room while the sub is connected and humming to see if it stops........the easy fix sometimes is using a 3 to 2 prong ac adapter but lifting the ground on such a powerful amp could be a fire hazard.

I suspect you have a bad cable, a poor ground or a bad
power supply inside the speaker amplifier. The amplifier
(inside the sub-woofer) could also be defective.
===
1) Bad cable or connector:
If the (braided shield/outer tube) of the coaxial input cable is
not grounded, the cable will pickup line frequency "hum"
from surrounding power lines, house wires, lights and
appliances.

This hum is then amplified by the speaker's amplifier
causing the constant bass sound you speak of.

Because the hum frequency fundamental is 60 Hertz in
North America, 50 Hertz in Europe, you hear it coming
mostly out of the sub-woofer, because the midrange and
high speaker circuits filter it out.

Check the input connectors, cable at both ends, wiggle
the jacks at a low volume setting to see if it changes.

Make sure that you are indeed using a properly shielded
coaxial cable.

A coaxial cable consists of a thin inner conductor, surrounded
by a flexible tube made up of a braided metal shield, which
must be grounded. This prevents hum from being picked up
by the sensitive amplifier inputs.
===

2) If the power supply within the sub-woofer's internal amplifier
is defective, the the power supply hum will also get coupled
into the amplifier and speaker with same results as above.

Power supply hum is typically twice the line frequency,
i.e. 120 Hertz, but not always, depending on what
component failed: Rectifier diode, filter capacitor, or
the voltage regulator.

3) Ground loops:
When you run very long cables between the source and
destination of an audio signal, multiple ground paths (must)
exist between the two points in space, creating complete
loop circuits.

Power line hum from the environment can (will) induce
heavy AC currents around these loops, creating a voltage
gradient across these cables, and in-between the end
devices.

Once again, this AC hum is coupled into the amplifier inputs.

Ground loops become a problem with cables over 10
feet long, and an astronomical problem for stage audio
engineers. To avoid ground loops, they must break
the circuit's continuity by using isolation transformers,
optical isolators, and/or differential input amplifiers.

So how long are your cables?

Most house stereo components are only designed to
handle 6 to 10 feet of cabling max.

30 feet is already asking for major trouble.

4) Feed back oscillation: This occurs when the output of
an amplifier is fed back to the inputs with a round trip
gain greater or equal to unity. The tiniest little electrical
disturbance is then amplified and re-amplified, over and
over again, usually at one preferred frequency, causing
the typical (ear-splitting) microphone squeal or howl.

In your situation feedback and/ loss of original signal
could be the result of mis-wiring the input cables.

Note that this is NOT as silly nor as unlikely as it sounds,
because many computer audio cards and even some
home stereo systems have re-configurable inputs and
outputs.

SOFTWARE configuration decides which jack at the
back does what !!!!

On my computer, for example, the Realtek audio driver
tries to automatically figure out what cable is connected
to each jack (usually it gets it wrong)

Using the Realtek control panel applet, I can then
manually re-configure the gray jack as input,
the green jack as bass, pink jack as center.... etc.

If this situation also applies to your system, please check
the software configuration. Connecting an output cable to
an input jack will certainly cause a lot of HUM and not
much music.

5) Finally, don't rule out internal sub-woofer failure. Unlike
the passive stereo/hi-fi speakers of days gone by, modern
multi-channel theater systems with front, center, rear and
sub-woofer speakers are internally amplified, with active
frequency cross-over filters and special effect/ surround
sound capabilities.

Usually, the large sub-woofer contains most of the
electronics, amplifiers and filters.

It feeds the other speakers, and it is controlled by
an external volume control module which can be separate
or built into one of the tweeters.

These sub-woofer electronics are prone to poor design,
overheating and early failure. (Even fresh out of the box
like yours)

If you cannot get it working, take it back to the store,
and make the NICE salesmen **** with it.

Good luck
Please rate my answers
Martin.

The input filter capacitor of ur sub may be damaged,the possibility is upto 99%.u can identify the capacitor easily as it will be the the larger capacitor in that board and is located near the power supply entrance.the component costs within a dollar