Monitor humm only when idle?

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DAS19

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Hey, I just got a new pair of Samson Rubicon R5as and when I plug in via rca to 1/8 into my macbook I get a really bad HUM that seems to change when I plug it into various outlet combinations but as soon as I hit play on itunes or any sound the hum goes away and it palyss music and when I pause theres no hum either.

Does anyone have any idea why this might be? is it becuase of the rca to 1/8 into my macbook and something abou unbalanced inputs and outputs? I left my speakres on by accident adn the hum was on full blast for probably 20 min. When I came back to my dorm room it was like shaking hte room but I play the speakrs now and thye dont sound harmed. Do you think any damage was done. I just bought these speakers a couple of days ago.

Any help would be greatly appreciated. I just want to hear what you guys thnk of my predictiment.
 
ground loops are a strange bear.

could the laptop internal switching be doing something?

try a different cable...try different ac sockets, try a rf shunt,

I keep watching this thread because i like the groundy loop "type" troubleshooting threads.

Try the Rubicons with a plain old CD player, partition the problem and you'll find it.

Try some different speakers...

Try a different media player...

just throwing ideas out there.

Once you find if its the speakers or the Laptop or the cable etc...then you can go to LEVEL 2 of the troubleshooting game.
 
Yeah but idk I thought ground loop problems mean it hums even when playing its weird. When it is playing music and I press pause there is no hum and its perfectly silent but when I just turn them on and dont play anything the hum is there.
 
so that sounds more like a laptop internal issue, possibly by design?
maybe the software does a mute once you have the media player going?

hmmmm?:p
 
I vote laptop. If you have settings for muting computer sounds like beeps when you get email and similar warning chimes I would try that. If you can do a selective start up and keep certain operations from running you may want mess with that and see if there is an operation causing the issue.

Checking with apple to see if there is a fix for the problem would be a good step too.


Good luck

F.S.
 
Both my laptops (Dell's) make some God awful noise when running on AC power without a ground lift.

I put a groundlift (3 prong to 2 prong adapter) on my power supply plug and the noise is gone.

Incedentally, I've noticed of late that Dell no longer uses 3 prong grounded power cables on their new line of latitudes.

It doesn't sound like this is your problem but I thought I'd throw it out there just in case.

Good Luck.
 
The hum might go away when I try to plug it in via my interface.

Does anyone know if the humming being on really loud for like 20 min would damage my speakers? They sound unharmed but do you think any damage was done?
 
DAS19 said:
The hum might go away when I try to plug it in via my interface.

Does anyone know if the humming being on really loud for like 20 min would damage my speakers? They sound unharmed but do you think any damage was done?
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Really loud is pretty subjective. I would say if your speakers sound fine, your fine. A hum would have to be on really really loud to do any damage:D

F.S.
 
Thanks FS

Im going to try connecting them through my interface and see if that does anything and also maybe try some ground lift 3 to 2 thingys.

Thanks to everyone that tried to help :D.
 
My laptop does that at the studio but not at home. No hum if I disconnect the power. It seems to be a laptop thing.
 
RocknRollOver said:
Both my laptops (Dell's) make some God awful noise when running on AC power without a ground lift.

I put a groundlift (3 prong to 2 prong adapter) on my power supply plug and the noise is gone.

Incedentally, I've noticed of late that Dell no longer uses 3 prong grounded power cables on their new line of latitudes.
Click to expand...

That's just because Dell wouldn't know how to design a proper power supply if an EE bit them in the ass. Two-prong power adapters are inherently less safe than three-prong, so if Dell changed from three to two, that's a really stupid decision.

You should NEVER EVER lift the ground on a power supply. It is potentially dangerous. Where do you think that hum goes now? Into you when you touch the computer. Is it harmful? Depends on what device is causing the hum and how much voltage is involved.
 
DAS19 said:
Hey, I just got a new pair of Samson Rubicon R5as and when I plug in via rca to 1/8 into my macbook I get a really bad HUM that seems to change when I plug it into various outlet combinations but as soon as I hit play on itunes or any sound the hum goes away and it palyss music and when I pause theres no hum either.

Does anyone have any idea why this might be?
Click to expand...

Yes. You're using the internal audio hardware. To conserve power, power to the built-in audio hardware is disconnected when not in use, and is only turned on when a piece of software actually tries to use the audio hardware. When you pause it, the hardware is not turned off. If you quit iTunes, though, the hum will come back after a period of idle time.

I don't know why you're getting hum with the audio hardware powered off but not with it powered on, but I'm pretty sure that's what is happening anyway.

Be sure you are using the three-prong cord that comes with the laptop and not the two-prong flip-out thing.

As for the underlying cause, my suspicion is that the speakers are actually generating the hum in their amp stage and it is coming out through the shield on the cable due to insufficient grounding in the speakers' power supply. When the audio hardware in the laptop is powered down, I suspect that the ground to the audio hardware is also getting disconnected, so the shortest path for that hum to take is through some output resistor between the signal wire and the now-floating ground. By contrast, when the hardware is powered up, the ground is connected to your system ground, and gets shunted through your power supply and out.

This is just a theory, though. I'd try a different set of active monitors. That said, those amps were designed for balanced input signals, and if you haven't tied the other side of the balanced input to ground... oh, crap, that's the problem. You are plugging in a mono cable, thus tying it to ground, which is now floating and humming. Okay, get an adaptor that adapts stereo 1/4" to a pair of mono 1/4" connectors, then use one of those (and be consistent about which one or your speakers will be out of phase with each other).
 
dgatwood said:
You should NEVER EVER lift the ground on a power supply. It is potentially dangerous. Where do you think that hum goes now? Into you when you touch the computer. Is it harmful? Depends on what device is causing the hum and how much voltage is involved.
Click to expand...
Agreed, definitely not something you want to do, but may have to.
 
dgatwood said:
That's just because Dell wouldn't know how to design a proper power supply if an EE bit them in the ass. Two-prong power adapters are inherently less safe than three-prong, so if Dell changed from three to two, that's a really stupid decision.
Click to expand...

That struck me as odd too.
I've set up a few here in the last year or so and they are without ground.
Being familiar with their noisy power supplies, I've been wondering if that had anything to do with their decision.

As someone mentioned earlier, you can tell if this is your problem by simply switching to battery power and see if the noise goes away.
 
DAS19 said:
Thanks FS

Im going to try connecting them through my interface and see if that does anything and also maybe try some ground lift 3 to 2 thingys.

Thanks to everyone that tried to help :D.
Click to expand...


How'd this one ever end?

and you owe us a review on those Rubicons....with pictures and RTA graphs, and mixes before and after, and..did you plug the ports?..:p
 
when I plug in via rca to 1/8
Click to expand...

did nobody else pick up on this?

$5 says that's where the hum comes from

run an XLR or TRS cable from your interface to the monitors, and the hum will likely go away
 
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