Interesting hum within my 7500

jrlouie

Last night I noticed a hum coming from my 7500. This isn't the infamous ground loop hum where you hear something coming out of your speakers, no sound there. This was from within the 7500, like a transformer buzz/hum. It wasn't very loud. I could hear it in my quiet living room, along with the fan on my laptop But, I could hear it from the couch, about 10 feet away.
Then I noticed something. I have a line conditioner that regulates voltage on that outlet. At the time the hum was most prevalent, the line conditioner was currently showing my apartment had a voltage boost and obviously the conditioner was compensating for that. Then when that dropped down and it showed regular voltage, the buzz/hum diminished.
Also, after that I unplugged the conditioner and 7500 and switched the actual plugs they were on within the outlet so that the 7500 was downstream from the conditioner in relation to where the juice flows into my apartment. At that time, it seemed the buzz/hum was much more faint or inaudible. Although, I wonder if unplugging and such discharges stuff and alleviates the noise temporarily.
So anyway, sounds like I have some testing/experimentation to do, to determine the cause.

jrlouie

Okay it was doing it again this evening. I rearranged everything, and no luck. This evening it is fluctuating in its buzz/hum, but unlike before the line conditioner is not displaying any voltage irregularities. It'll have 5 seconds of buzz and then 30 seconds with barely audible or no buzz. I basically have one 2-plug outlet in this corner with what appears to me to be downstream from one light and my computer stuff. Here is what I have done.
- line conditioner unplugged
- line conditioner plugged in downstream from amp (with and without amp on a power strip)
- line conditioner plugged in upstream from amp (with and without amp on a power strip)
- amp plugged into line conditioner
- unplugged computer system
- turned off upstream light
- unplugged satellite cable from wall
- used cheater adapter on amp

All of these different variations had no effect. Any ideas? Am I just stuck with it like this? I mean, it is not horrible, but I do notice it.

jrlouie

Sometimes, like now, the amp is dead quiet. Weird. I'm wondering if it is noise on the line. If so (but who knows), I'm wondering why my line conditioner didn't help.

jrlouie

Sorry, this thread should've been in the troubleshooting forum. Oops.

Airplay355

I have no idea man. My carver amp hums alot, but i think it just hums because that's how it was made. try google?

jrlouie

Hmm, maybe it's just how it is.

jrlouie

Interesting article....
http://www.psaudio.com/products/humbustermoreinfo.asp

tonyb

Try unpluging one IC at a time,some times it is as simple as a bad IC .. or a bad speaker connection.Also make sure your power cords are not crossing the other wires.If you cant avoid crossing do so on right angles.Make sure all cables have proper shielding....this is audio 101 guys.Had my share of audio hum and have found that better cables have better shielding...duh ,they better.

jrlouie

I was just thinking since the hum isn't coming from my speakers, that this was different. The hum is easy to locate coming from the amp itself, probably the transformers.

danger boy

call or email Outlaw Audio and see if that humm is normal or what.

jrlouie

Called them. Once again, they're very helpful and understanding. But from what they said, it has been their experience that this could be due to not enough voltage, or DC noise on the line.
He made a couple of suggestions to test out. We'll see what happens.
He did say you shouldn't be able to hear it from the listening position, like I can.

jrlouie

So I tried a test. Outlaw suggested I try various outlets and if possible, outlets on a different line. When I tried, I thought the different line cleaned it up. But, I was using an extension cord and when I tried it on other outlets on the original line, I couldn't hear it then either. So, I used a power strip to different outlets on the original line, and I could hear it. So, essentially somehow this one extension cord is masking the test.
Now with the power strip, I can hear the hum from the 7500, from 2 other outlets on the same line, with or without a cheater plug. I also was able to find a different extension cord that still allowed me to make the 7500 hum. Using that extension cord, going to a different line, the 7500 still buzzes/hum.
So, I guess it isn't really this one line. It is in my apartment at various locations. I wonder if the electrical stuff in this building is just noisy. I know the lights flicker a lot. I wish I could find a loaner DC filter, just to try it out and see.