60hz hum w/ Rythmic plate amp and OB speakers

drphoto · « **on:** 2 Oct 2009, 05:08 am »

I just noticed a 60hz hum. Dunno whether it was there all along and in all the excitement I overlooked it or if something new. Could be that w/ the cooler weather, my room is much quieter, w/ no AC or fans or anything.

All the other audio gear can be off. Just the plate amp and speakers gives the hum.

Tried a 2 prong cheater plug.

Tried running power from another room via long heavy duty extension.

Turned off all fluorescent lights.

Straight from wall or via Monster filter strip no change.

Tried to move the harness as far away from power cord and inputs as possible. Although it doesn't matter whether there are imputs or not. Even pulled them out.

Now that I notice it, it is really bugging me. (it's low, but very noticeable, gotta be sucking up power and coloring the sound) Any thoughts? Bad amp?

sl_1800 · « **Reply #1 on:** 2 Oct 2009, 01:40 pm »

I don't have much to offer other than mine does not do that.

TRADERXFAN · « **Reply #2 on:** 2 Oct 2009, 02:05 pm »

Do you have anything battery powered in your system?
My amp is the red wine and when I switch it to off/charge then I hear it, and so I have to manually switch off the sub amps.

Otherwise I have had no problem on either of my rythmik amps.

I did have a problem with an old paradigm sub that developed a problem over the years. It would hum whenever any rca was connected to it. But if I went speaker level input it didn't. So maybe experiment with that to see if it is something to do with the inputs?

-Tony

MaxCast · « **Reply #3 on:** 2 Oct 2009, 03:03 pm »

Is all your gear plugged into the same outlet?

ANy video, or tv connections to the system?

sl_1800 · « **Reply #4 on:** 2 Oct 2009, 03:27 pm »

MaxCast has brought up a good thing to check, cable tv connections. A friend recently had bad 60 cycle hum, disconnected the cable tv from his system and it went away.

corndog71 · « **Reply #5 on:** 2 Oct 2009, 03:49 pm »

When plugged into my living room (with digital cable box on the same circuit) I got a pretty loud hum but a cheater plug eliminated it.

What I found interesting was when I plugged the amp into a different circuit I got no hum at all.

Also, double check all of your other connections. When I first connected the cable from my receiver to the amp I had it plugged into the sub input on the receiver.

drphoto · « **Reply #6 on:** 2 Oct 2009, 04:50 pm »

It doesn't matter what else is on. Remember, I removed the inputs to the sub amp. Just having the amp on and connected to the speakers and I get hum. It is from the speakers, I can feel the cone vibrate, not a tranny humming.

cheaters, changing cords, reversing polarity, using a different AC, circuit, no cable TV......nothing makes it stop.

ebag4 · « **Reply #7 on:** 2 Oct 2009, 05:14 pm »

Not sure why it would matter, but did you hear this issue when just two drivers were connected?

Best,
Ed

drphoto · « **Reply #8 on:** 2 Oct 2009, 05:34 pm »

Doesn't depend on # of drivers connected. As to whether it was there all along, and I didn't notice do to air conditioner noise or whether it is new....I dunno.

sl_1800 · « **Reply #9 on:** 2 Oct 2009, 08:37 pm »

I am assuming it stops when the amp is powered off and starts as soon as the amp is turned on?

drphoto · « **Reply #10 on:** 2 Oct 2009, 09:52 pm »

Correct. amp on=hum. no wallwart switching PS connected. All other equipment can be turned off. It's fairly low in volume, but you can hear it at the listening position...no need to put one's ear next to the driver

nicksgem10s · « **Reply #11 on:** 2 Oct 2009, 10:28 pm »

I wish I could think of something else that hasn't been mentioned.

I have been using the Rythmik amp with my Hawthorne Audio Augies for about 1.5 yrs w/great results (no hum)

Maybe Mr. Ding from Rythmik Audio can chime in with some advice. I think he is on AC if I remember correctly.

There has to be a explanation. Hopefully someone knows how to contact him on AC.

-Nick

markC · « **Reply #12 on:** 2 Oct 2009, 11:48 pm »

Check the power supply caps on the plate amp. A friend developed a nasty 60 cycle and it turned out to be bad caps. His were actually oozing goo. It's not a Rythmic, but maybe worth a look.

corndog71 · « **Reply #13 on:** 3 Oct 2009, 12:35 am »

also, your signal cables should be seperated from power cables as much as possible.

Bob in St. Louis · « **Reply #14 on:** 3 Oct 2009, 12:36 am »

Hey Doc,
How about trying to power the Rythmic using an extension cord plugged into other outlets in your house. Just to make sure you haven't got an issue with that circuit, or that leg of your 120? Might wanna try several different outlets to ensure you've got a good idea if it's the house, or the amp, or....??

Bob

Bob in St. Louis · « **Reply #15 on:** 3 Oct 2009, 12:38 am »

Awww crap....I just re-read your first post.

But did you try multiple rooms? (cheap attempt at self redemption).

Bob

srb · « **Reply #16 on:** 3 Oct 2009, 12:48 am »

If possible, how about a long yard extension cord plugged into your neighbor's house?

(I'm assuming that your OB with multiple drivers is quite large and isn't going anywhere, ie. to an audio buddy's house).

Steve

MaxCast · « **Reply #17 on:** 3 Oct 2009, 01:40 am »

Turn the AC and fans back on and 4getabowdit.

I find it hard to believe you have not noticed it before, therefore, something must have changed. Have you unplugged the rest of the system?
Take it to a neighbors house like srb suggests. If she hums over there send her in for a check up.

stevenkelby · « **Reply #18 on:** 3 Oct 2009, 02:12 am »

Try shorting the inputs and see if it goes away. Just scrunch up some tin foil into and on the rca plug, shorting + and - together.

Sounds to me like a bad cap or something, like the power supply is getting into the output path. Or something.

drphoto · « **Reply #19 on:** 3 Oct 2009, 08:45 pm »

Ok, you're not gonna believe this. I had moved the OB panels to the outside of my mains, because I wanted to experiment w/ putting the main monitors on the floor, tilted back ala Mapleshade's Bedrock stand. When I put the monitors back on stands, I decided to move subs back where the were, flanking the stand. To move the subs, I had to disconnect the speaker leads. When I hooked it back up.....the hum was GONE!

Dunno know why, but I'm happy anyway.

Thanks for all the feedback anyway.