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The Entry Level Stax Thread - Page 49

post #721 of 1196

There are a few different configurations that could cause the hum, but we need to know more about the outlets, power cables and general setup.

 

I'm starting to think it may be insufficient grounding on the laptop end. If the amp is well grounded, the path of least resistance could be going through the USB cable, DAC and then to the amp. When you touch the macbook, the path of least resistance changes to your body, thus the noise goes away. The trouble here is the ground wire coming from the wall doesn't go directly to your laptop. It's usually somewhat isolated inside the laptop powersupply so it's not a direct ground. The ground on your amplifier end may be direct to the wall.

 

Take a look at your laptop powersupply and see if it's using a 3-prong grounded plug. If so, make sure you're getting a good tight connection in the wall or powerstrip. Make sure your powerstrip has a good tight connection into the wall. If possible, use the same powerstrip for your entire audio system to avoid any differences in ground quality from using different wall outlets.

 

If your laptop has a 3-prong grounded plug and the above suggestions don't work, then bypassing the ground with an adapter on your amp will most likely solve the issue. It's perfectly OK to try this as a diagnostic tool to find the problem. It's up to you if you want to run it this way long-term. Personally, I would without hesitation. But then my house has no grounds at all so it's a moot point.

post #722 of 1196
Quote:
Originally Posted by Marleybob217 View Post

Quote:
Originally Posted by miceblue View Post

Gah, sometimes I wish I had just gone for a basic STAX setup instead of taking the usual "Head-Fi journey." XD


Anywho, I noticed that my SRS-2170 has a grounding issue and I can hear a quiet, low-frequency "ham" noise. Upon touching my aluminum MacBook, the sound goes away. I usually have my hands resting on the MacBook anyway, so I don't usually hear the noise. Can you guys think of any reason for this? I really can't imagine STAX built a poorly-designed unit.


MacBook Pro -> Monoprice USB-mini-USB cable -> JDS Labs ODAC with RCA output -> 3.5 mm-RCA cable -> SRM-252S + step-down transformer + wall wart from Japan -> SR-207
In case no one has answered this: You can either plug in your dac and amp into an ungrounded power strip, or you can plug your macbook into that one.
The ac/dc converters of laptops are known to cause these kinds of hums.
Yeah I can try plugging in the laptop and/or amp wall warts into different outlets when I get back home.

Right now, both are connected to a surge-protected power strip which has the 3-pronged connection to a house outlet. Neither the step-down transformer nor the laptop power cables have the 3-pronged connection to the power strip, they just have 2.
post #723 of 1196
It seems that there's no ground at all which could explain why the interference doesn't have anywhere to go until you touch it. I would try a laptop power supply that features a 3 pin grounded plug.
post #724 of 1196
Quote:
Originally Posted by miceblue View Post


Yeah I can try plugging in the laptop and/or amp wall warts into different outlets when I get back home.

Right now, both are connected to a surge-protected power strip which has the 3-pronged connection to a house outlet. Neither the step-down transformer nor the laptop power cables have the 3-pronged connection to the power strip, they just have 2.

Well, there is still a ground loop going on. Probably. If you unplug your laptop, does the humming go away? If so, I'm 100% sure using an ungrounded outlet will solve your problem. 

post #725 of 1196

maybe it's just "ham noise" ;)

post #726 of 1196
Thread Starter 
Quote:
Originally Posted by shipsupt View Post

I never said I would recommend removing it, I just clarified the misconceptions you created.

There is no misconception.

actually causing a fire may be an extreme case, but it is possible if you just go ahead and start blindly removing ground pins.

I've purchased equipment that hummed quite loudly, I was able to fix the problem without removing a single ground pin or even using a ground lift switch.
post #727 of 1196
Without the failure of another safety device like a fuse and circuit breaker how will it cause a fire?

Good to hear you were able to correct you hum without dealing with the ground. Hopefully the OP can do the same.
post #728 of 1196
Huh, now I don't hear any "ham" noise. Weird. XD
I did, however, unplug the power strip from the house wall outlet and plug it back in.
post #729 of 1196
Thread Starter 
Quote:
Originally Posted by shipsupt View Post

Without the failure of another safety device like a fuse and circuit breaker how will it cause a fire?

Good to hear you were able to correct you hum without dealing with the ground. Hopefully the OP can do the same.

I once stood fairly close to a high voltage capacitor that caught fire.
It happened so long ago that I no longer remember if the upstream circuit breaker or fuse opened up.
I do remember we needed to use a fire extinguisher to put the fire out.
Turns out we had purchased a Lot of defective capacitors.

I remember another instance where a high voltage capacitor failed and shorted to the enclosure causing a ground fault.
Fortunately the enclosure was grounded properly and the upstream fuses opened up, removing power from the system.

I have seen ground fault protection schemes fail to operate because the system was improperly grounded.
Result: someone received an electric shock.

Electricity is dangerous.
you can't just go around removing ground pins if you don't understand what you are doing and what the ground pins are for.
Edited by Chris J - 11/15/13 at 3:33am
post #730 of 1196
Quote:
Originally Posted by Chris J View Post


I once stood fairly close to a high voltage capacitor that caught fire.
It happened so long ago that I no longer remember if the upstream circuit breaker or guse opened up.
I do remember we needed to use a fire extinguisher to put the fire out.
Turns out we had purchased a Lot of defective capacitors.
I've seen many similar events with capacitors and many other electrical components.  The grounding would not have prevented any of them from failing or from catching fire.

I remeber another instance where a high voltage capacitor failed and shorted to the enclosure causing a ground fault.
Fortunately the enclosure was grounded properly and the upstream fuses opened up, removong power from the system.
The safety systems operated as they should.  

I have seen ground fault protection schemes fail to operate because the system was improperly grounded.
Result: someone received an electric shock.
THIS is exactly the type of incident that a properly grounded system can avoid.
Sorry to hear someone was injured.  
THIS is a good reason someone should be be very cautious about removing the ground pin from a system designed to have one and not taking other precautions.

Electricity is dangerous.
you can't just go around removing ground pins if you don't understand what you are doing and what the ground pins are for.
Agreed.

 

I'm not trying to argue that removing a ground will have no consequences, but if you're going to say "why" then it should be based on good information.  

 

Removal of a ground can create the risk of electrical shock if other precautions are not considered.  On this basis I agree that you shouldn't remove them unless you are able to understand and mitigate that risk.

 

I am not aware of how removing the ground would create a fire hazard.

post #731 of 1196
Thread Starter 
Quote:
Originally Posted by shipsupt View Post

I am not aware of how removing the ground would create a fire hazard.

There are 100s of things that can go wrong.
If you're smart, you may be able to imagine a few of those scenarios.
It is always difficult to understand the designer's design intent after the fact.
If the designer designed it in, then the safety feature has a purpose, perhaps dictated by Safety Authorities, or perhaps the grounding scheme was dictated by noise immunity and noise suppression testing.

Hard to explain if you haven't dragged a product kicking and screaming into meeting FCC # Class B or CE Industrial noise immunity standards.
post #732 of 1196
Quote:
Originally Posted by Chris J View Post


There are 100s of things that can go wrong.
If you're smart, you may be able to imagine a few of those scenarios.
It is always difficult to understand the designer's design intent after the fact.
If the designer designed it in, then the safety feature has a purpose, perhaps dictated by Safety Authorities, or perhaps the grounding scheme was dictated by noise immunity and noise suppression testing.

Hard to explain if you haven't dragged a product kicking and screaming into meeting FCC # Class B or CE Industrial noise immunity standards.

Then why are ungrounded sockets still in use/being sold? Or are there devices than just don't need that ground connection? 

I've been using ungrounded power strips for years, exactly because of the hum problem. Needless to say I never had any fires :D

post #733 of 1196
Quote:
Originally Posted by Chris J View Post



If you're smart, you may be able to imagine a few of those scenarios.
 

Ok, I'm not smart then.

 

Quote:
Originally Posted by Marleybob217 View Post
 

Then why are ungrounded sockets still in use/being sold? Or are there devices than just don't need that ground connection? 

I've been using ungrounded power strips for years, exactly because of the hum problem. Needless to say I never had any fires :D

 

Yes. A device in plastic enclosure with no path for electricity to reach the user in case the hot lead comes into contact with the chassis is a good example.  

I wouldn't worry about stuff bursting into flames because of it, but there is a chance of electrical shock.

post #734 of 1196
Quote:
Originally Posted by shipsupt View Post
 

Ok, I'm not smart then.

 

 

Yes. A device in plastic enclosure with no path for electricity to reach the user in case the hot lead comes into contact with the chassis is a good example.  

I wouldn't worry about stuff bursting into flames because of it, but there is a chance of electrical shock.

Somehow I don't think these devices would never reach the market. 

What if you use grounded sockets, but the electricity in your house isn't grounded anywhere? I don't think the electricity in my house is grounded anywhere.

post #735 of 1196
Then there won't be a third prong on your female outlet and you won't be able to plug a device with the ground in unless you defeat that protection. And yes, people do it all the time.

Check with the smart guy, he can "imagine" some more stuff, like maybe explosions or something.
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