restorer-john
Grand Contributor
It works! Hum is entirely gone - ear up against the speaker, nothing.
That's fabulous.
It works! Hum is entirely gone - ear up against the speaker, nothing.
Double insulation (class ii) is just a cop-out and not remotely as safe as a correctly earthed device. It's been watered down over the years to the point where I see multiple flaws inside most pieces of inexpensive gear that could easily render the items highly unsafe in predictable failure scenarios.
My attitude is, if the item has ANY exposed metal than can be touched, the item should be safety earthed. Period.
The double insulation plague in audio started in the late 1970s, prior to that, pretty much all HiFi was correctly earthed. A lot of gear coming into Australia in the 1970s and 1980s had to be rewired here to our standards. In fact several HiFi brands had perforated trapdoors in the packaging, that you hinged out, changed the plug and the voltage switch and folded the flap back- all without removing the product from the package.
Ironically, Pioneer Australia 'created' hum problems in some high end HiFi amplifiers by rewiring multivoltage class ii (double insulated) products with an Australian compliant three core earthed lead. In those cases, yes, the earth lead shouldn't have been there.
Double insulation gave lazy designers an 'out' in terms of hum related issues on the typical single ended (RCA) designs of the time.
Absolutely true, and I have made a mistake resulting in a GFCI trip which may well have saved my life. I guess I'm trying to say there are risks in deliberately removing inherent safety devices (ie disconnecting earths).But people trust there lives to them everyday in every bathroom.
Yes. The current on the ground loop don't have to be only 50/60Hz.could a ground loop have created that audible hiss in addition to the hum?
@DonH56 @restorer-john and anyone else who's interested: I've re-checked my speakers a couple of times since installing the Hum-X to break the ground loop, and I've made a strange realization - a positive one, but one that is nevertheless puzzling to me given my limited knowledge of this aspect of our hobby.
I have realized that when I put my ear up against the speaker with all the equipment powered up, it's not just the hum that's gone. The hiss has been radically reduced as well.
Previously the power amp was silent - no hiss when it was the only powered-on component in the chain. Then turning on the EQ would add hiss - not audible from more than about 12-16 inches away, but definitely there and easily detectable when listening for it at the mid-woofer or the tweeter (my speakers are two-way stand-mounts). Turning on the Oppo would slightly increase the hiss level further, but only a little. So I had assumed (reasonably I think) that the EQ had some self-noise that would come through, followed by the Oppo, which as a newer component and notably excellent performer, would add much less self-noise to the signal than the EQ did.
But now when I put my ear up against the mid-woofer I literally hear nothing - no sound of any kind at all. I can still hear some hiss at the tweeter, but I have to raise my head to be in line with the tweeter and get my ear within 4-5 inches of the tweeter to hear it, and even then the hiss is at a low level and seems to have a "softer" more attenuated quality to it.
So my question is, could a ground loop have created that audible hiss in addition to the hum? Or alternatively, is there something in the way a device like the Hum-X works that can also radically reduce the level of self-noise that gets to the amp and into the speakers?
As noted above, I am thrilled with this unexpected additional benefit of the Hum-X, but I'd also like to understand it. Thanks for any insight and perspective folks can provide!
Hi Lambda - as one of those "internet experts" you are referencing, I have to tell you I've done some more research (including your own measurements) and I have to say....Yes. The current on the ground loop don't have to be only 50/60Hz.
Its/can be also lots of Noise from switch mode power supply's and also inductively pickt up as well as RF noise.
You might not hear the RF directly but if it is modulate you might hear this and it can also increases the noises floor/his.
This is a reason why i often say Ferrite common mode cokes can in some cease make a huge difference.
But the "internet experts" here already made there mind up an say they can't make an Audible difference...
Re: the hiss level change. Are you sure the gain/volume settings are the same as before (when you had the hum too)?
The audible shift in the spectral output of the 'hiss' is interesting. All analogue EQs make noise, each slider has a dedicated opamp (usually) and they are all cascaded together when the EQ is active (even if they are sitting at "0"dB. Depending on the frequency bands you adjust, the self noise (hiss) will also change its character whether you boost or cut.
It's also possible the Hum-X has broken some path where PSU noise was infecting your audio.
But whatever the reason, you have solved your hum, still get to use your EQ and have some bonus improvement as well.
I have had similar experiences i.e. when I have had a ground loop and "broken it" all noise from all sources is radically reduced including hums, buzzes, hisses, computer noises, WiFi noises, and pops from turning on and off lights in other rooms. I am not 100% sure of the physics but my understanding is a ground loop and the attached components can act as an "antenna" and pick up noise from many sources and inject it directly into the signal path. In any case I am glad you found a solution.@DonH56 @restorer-john and anyone else who's interested: I've re-checked my speakers a couple of times since installing the Hum-X to break the ground loop, and I've made a strange realization - a positive one, but one that is nevertheless puzzling to me given my limited knowledge of this aspect of our hobby.
I have realized that when I put my ear up against the speaker with all the equipment powered up, it's not just the hum that's gone. The hiss has been radically reduced as well.
Previously the power amp was silent - no hiss when it was the only powered-on component in the chain. Then turning on the EQ would add hiss - not audible from more than about 12-16 inches away, but definitely there and easily detectable when listening for it at the mid-woofer or the tweeter (my speakers are two-way stand-mounts). Turning on the Oppo would slightly increase the hiss level further, but only a little. So I had assumed (reasonably I think) that the EQ had some self-noise that would come through, followed by the Oppo, which as a newer component and notably excellent performer, would add much less self-noise to the signal than the EQ did.
But now when I put my ear up against the mid-woofer I literally hear nothing - no sound of any kind at all. I can still hear some hiss at the tweeter, but I have to raise my head to be in line with the tweeter and get my ear within 4-5 inches of the tweeter to hear it, and even then the hiss is at a low level and seems to have a "softer" more attenuated quality to it.
So my question is, could a ground loop have created that audible hiss in addition to the hum? Or alternatively, is there something in the way a device like the Hum-X works that can also radically reduce the level of self-noise that gets to the amp and into the speakers?
As noted above, I am thrilled with this unexpected additional benefit of the Hum-X, but I'd also like to understand it. Thanks for any insight and perspective folks can provide!
That shouldn't be happening, at least in any device that has actually undergone certification (UL etc.). DIYers don't like Class II much, as it requires higher standards for internal construction (no exposed wires, double insulated mains cable to power switch etc.), not to mention that the kind of mains transformers required for integrated or power amplifiers (shield winding to keep leakage currents down) tend to be at least uncommon or even custom order.Double insulation (class ii) is just a cop-out and not remotely as safe as a correctly earthed device. It's been watered down over the years to the point where I see multiple flaws inside most pieces of inexpensive gear that could easily render the items highly unsafe in predictable failure scenarios.
Nothing to do with laziness. Cost-cutting, perhaps. Trying to keep the case insulated from the jacks and internals typically results in a huge mess with loads of small RF bypass capacitors, and that still does a worse job keeping RF out than the cheaper standard approach of using the backplate as a star ground. Our German hi-fi brands kept the older style of construction up into the 1980s, but no manufacturer of bread and butter components would be keeping on doing something long-term that's more expensive and performs worse.Double insulation gave lazy designers an 'out' in terms of hum related issues on the typical single ended (RCA) designs of the time.
And the fact that you have to circumvent a safety feature don't give you the feeling that something might be wrong?But, any and all other devices in my system with a 3-prong plug must have the ground pin floated to eliminate hum.
Well they are connected together via RCA cables or something? how can there be voltage?I have never measured voltage across the various chassis, but I have never felt so much as a tingle.
It's almost never the voltage that kills. It's the secondary effect like the fall from the leader or most often a house fire.We’re on 120VAC here, and I don’t think I’d risk this in a 220/230/240VAC region. I’d probably call an electrician to change a light bulb there.
You'll probably be fine until something breaks and shorts the chassis to 120 Vac. It's not the fall that kills, it's the stop at the end. Read the rest of the thread.In the manual of every Hafler amplifier I own:
“Never remove the round grounding pin on the plug in an attempt to mate to a two wire ungrounded receptacle: use a grounding adaptor with the grounding tab or wire suitably connected to earth ground.”
Now, in the house we’re currently in, built in the USA in 2013, my Pioneer AVR has an IEC 3-prong plug and is plugged into a UPS. EVERYTHING in the system is running on UPSes on the same breaker. But, any and all other devices in my system with a 3-prong plug must have the ground pin floated to eliminate hum. By that I mean, they have to be ungrounded. I have never measured voltage across the various chassis, but I have never felt so much as a tingle. I honestly don’t know exactly what’s going on here. We’re on 120VAC here, and I don’t think I’d risk this in a 220/230/240VAC region. I’d probably call an electrician to change a light bulb there.
Of course I know something is wrong.And the fact that you have to circumvent a safety feature don't give you the feeling that something might be wrong?
Well they are connected together via RCA cables or something? how can there be voltage?
It's almost never the voltage that kills. It's the secondary effect like the fall from the leader or most often a house fire.
You think The RCA and devices can safely handle the fault current and there combined impedance is low enough to trip the barker at 120V?
This can be save if you have a fast blowing low current fuse for this outlet and an GFCI.Ask yourself, what happens to either of the diodes or the 1/2 watt resistor when there is a 150 A, 2.5 second line to chassis fault before the breaker trips? Which device fails first? What happens if there is a 1000 A, 100 ms line to chassis fault before the breaker trips? After any of those components fails open or goes up in smoke, do you think that the breaker will trip without a ground connection? Where will current flow in the now line-voltage energized chassis?
you need to figure this out by systematically testing all devices/connections.What’s the cause
don't think this is necessary. only on the connections that cause problems by passing common mode currents.Am I expected to install isolation transformers at every connection?