Troubleshooting sequence for subwoofer hum?

[Boomzilla]

One of my two subs has a loud hum every time I turn it on. It isn't the sub itself, because if I disconnect the cable, the sub is silent. My troubleshooting plan (to be implemented tomorrow) is as follows:

1. Switch cables between the two subs.
If the hum stays on the same sub, the sub itself or its power supply is the hum source.
If the hum is now on the different sub, it's coming from the cable, preamp or source. Leave the cables where they are.

2. Switch cables at the preamp.
If the If the hum stays on the same sub, both cables are OK & the hum is coming from the preamp or source. Leave the cables where they are.
If the hum is now on the different sub, sub, the preamp-to-subwoofer cable is defective - replace it.

3. Switch channel cables between the source and the preamp.
If the hum stays on the same sub, the preamp is defective - replace it.
If the hum is now on the different sub, it's coming from the source. The source is defective, replace it.

In between steps two & three, there's a very slight chance that the hum is coming from the source to preamp interconnects. They can be tested in the same manner as step 2.

Have I missed anything? Is this a sound strategy?

Thanks - Boomzilla

[Gary Cook]

That's the process I follow, start at the last component in the systems and work backwards.

If the hum is there from all sources then you might not have to eliminate the sources as the source.

Cheers
Gary

[mshump]

Sounds like a good plan Boom