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Hi. I could use some advice. I've been experimenting with adding a subwoofer to my music-only two-channel system and ran into a hum problem.
The first sub I tried, a PSB Stratus 1000, gave me endless fits of feedback when playing vinyl (it was fine with digital) but had no hum issues. The new sub, a Spendor Sub-3, is working out much, much better on the feedback front.
However, when I use the Spendor's supplied AC cable, with IEC female at one end and a 3-prong plug, I get an extremely loud hum. Because the PSB's hard-wired AC plug was 2-prong, I tried an AC cable with the Spendor sub that was IEC to 2-prong plug. It was just something I had sitting around. The hum vanished.
Here's my question. Googling this ground loop issue reveals consistent warnings about using one of those 2-prong adapters to remove loops because there is potential for getting a jolt. But is using the IEC to 2-prong cable the same thing? Is it essentially just like using an adaptor only without the adaptor, or am I safe?
The sub is not plugged into the same outlet as the rest of the stereo, by the way. The rest of the stereo is plugged into an outlet that has a dedicated fuse (it powers nothing but the stereo).
Thanks in advance.
- jlp
Follow Ups:
I'm sticking with the second-hand plug and have quit worrying about it. I appreciate the help. I have no hum and, for the first time with this current set-up, bass I can really feel with no issues.
Because the PSB's hard-wired AC plug was 2-prong, I tried an AC cable with the Spendor sub that was IEC to 2-prong plug. It was just something I had sitting around. The hum vanished.
The outer case, box enclosure, of the Spendor sub is made of wood. At 120V dry wood is a good insulator. Your odds of getting hit by lightning are better than ever getting a shock from the sub.
If you are worried, replace the standard duplex wall receptacle, the sub is plugged into, with a 15 amp GFCI duplex receptacle.
Edits: 06/30/14
took a hacksaw to the ground prong on my Pangea cable,
"Man is the only animal that blushes - or needs to" Mark Twain
Amen! Safety ground=noise antenna. By the way I took advice of those a lot smarter than me in removing safety ground namely Charles Hansen and Paul McGowan.
ET
Edits: 06/30/14
None of the vintage amps and preamp had 3 prong plugs and we all survived.I only ground my preamp. I "lift" all other grounds and I'm still alive!
I'm not saying it's "safe", I'm saying it sounds good.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 07/01/14
You probably have a ground loop commonly caused by using two separate outlets. Try plugging your sub into the same AC source as the rest of the stereo and your hum will most likely disappear.
With that said, without going into details you can use a two prong cord or a three to two prong adaptor. Many AA Inmates do this and never encounter a problem.
Cheers,
Al
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