All Of A Sudden - Hum issue!

[jdm56]

More subwoofer problems.[:@] I've had these two Velodyne DLS-4000R's in my 2-channel rig for a few months now and suddenly out of the blue, one of them won't auto-off...and it hums. I'll shut down the main stereo amp and everything is fine until I come back in a few minutes and instead of everything being powered down and quiet, the one sub will still be on and HUMMING LOUDLY with no input. Turning the amp off or unplugging it or even switching EQ modes will stop the hum. And it will power down manually. So, what the heck is going on here? Could something loose be causing the hum? I think it's still under warranty but I'm hoping it's just some silly, simple thing I can take care of so I don't have to take it to the subwoofer fixer.

[CECAA850]

If it's humming with no input attatched I would think the amp may be suspect. Disconnect the signal wire from the amp. If it still does it, I'd check into a warranty repair. If it doesn't do it any more, switch subs. If the other sub does it then there's something wrong with the wire or output to that sub. Swap wires and continue with the process of elimination.

[jdm56]

Let me clarify: There is an input attached, speaker level from the amp, but there is no signal. The amp is off. It sounds like a ground loop, 60Hz hum to me. I have contacted Velodyne, but I haven't received a response yet.

I'm really sick and tired of powered sub problems. I've had a ton! I'm thinking real hard of a move to passive subs with external electronics, specifically a Velodyne SC-1250 amp/crossover/eq, used with whatever high-quality, high-value driver I can afford in a diy box. Parts Express has the Titanic III 15" driver on sale right now for $178/each. The Velo SC-1250 lists for $1K and can drive two subs, so even at list, combined with the Titanics and a pair of home-brew 4 cu. ft. vented boxes, I should get some serious la scala-worthy bass.

[Islander]

It's possible that one of the interconnects to the sub has failed. Last year I bought a better (or at least more expensive) interconnect for my sub. It caused a hum audible across the room and the sub would not switch itself off, even after the receiver was left turned off overnight.

I re-installed the original cable and the problem went away, so I returned the cable and got my money back. The salesman was surprised and said he'd never heard of a defective cable. It was the second time for me, since I previously had an interconnect on my bedroom system that was bad right out of the package, with one of its two channels not passing any signal. That salesman didn't believe me either, but did exchange the cable for a working one.

[CECAA850]

I was trying to see if it was an amp issue. If it hums with no signal cable attatched then your amp is suspect.

The easiest way to see if you have a ground loop issue (which can happen with a passive sub and external electronics also) is to try a cheater plug on the end of the amps power cable. If the hum goes away with the cheater plug, remove it and diagnose your ground loop problem.

[jdm56]

My speaker/subwoofer connection scheme is like this: Integrated amp speaker outputs to LS2 hi-freq binding posts / LS2 low-freq binding posts to sub. LS2's run full range and subs roll off above 80Hz. That's it; pretty simple. All connections are at speaker level using 12ga. stranded copper. No problems for six months until now. And problem is intermittent even now. For instance, I listened to three CD's today with no problem at all (Bernstein/Tchaikovsky; Brian Wilson/Imagination; Rolling Stones/Emotional Rescue).[] Every time the problem as occurred was when I had one of the right subs' EQ modes engaged.

I know going to passive subs won't eliminate ground loop issues. I'm just saying I think they would be much less trouble-prone all the way around. Or let me put it another way: I've owned twelve powered subs over the last ten years or so. Seven have had functionality or reliability issues. Not a good record for the product category, in my opinion.