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How dangerous is lifting the ground on a source component?

brimble

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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.

Thank you. That was my initial guess, before I posted here. Do you know why TEAC so strongly insists that my double-earthed amp must not be earthed? It's not your job to know what they're thinking, but the manual reads to me like they think it's a safety issue and I really must not earth it.

(In case you're wondering, I'm in Australia and am having this amp posted to me from Britain.)
 

MeZoX

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safety ground is there to discharge any part of the electric device that can become energized due to a failure , if the device you're talking about doesnt have a conductive enclosure or switches that you may touch then you shouldn't really need the ground that much

another work around is that you can fit your system with a GFCI that would protect you from electric shocks without the need for safety ground
 

Lambda

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You should not mess with grounding as it is an safety Feature

This said. if you have an good CFGI there are relatively save ways to make a ground lift if you have to.
Novacek301-4.jpg

The Fuses should be rated as low as Possible and the Diodes need to be Abel to handle what ever the maximum short circuit current can be.

they actually sell this as a product for boats.
"galvanic isolator"
galvanic-isolator-wire-in-wiring-diagram-nt.jpg


But i would say its not worth it.
Especially if you have to ask if it is save... it is not save if you do it.
And it is maybe also illegal depending on where your located.

All in all possible but not worth it. just get balanced gear and interconnects
 

rkbates

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But people trust there lives to them everyday in every bathroom.
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).
 
OP
tmtomh

tmtomh

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@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!
 

Lambda

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could a ground loop have created that audible hiss in addition to the hum?
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...
 

Weeb Labs

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The simplest and safest answer to this question is that if you need to ask, then you should not do it.
 

restorer-john

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@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!

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.
 
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tonycollinet

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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...
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....

I was wrong. In the specific case of ground loops where the close to zero impedance of the loop can be influenced even by very small impedance from a ferrite, then yes, audible improvements can be made.

I think even your measurements don't show much impact below about 1kHz - so probably not much use for mains hum, but in the case of the sort of hiss mentioned above, then they probably can help.

So apologies for my pre-conceived denial of what you were saying.
 
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OP
tmtomh

tmtomh

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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.

Thanks! Yes, same gain levels.
 

levimax

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@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!
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.
 

AnalogSteph

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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.
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.

I think construction standards for Class II have evolved a fair bit since the 1970s... the internal mains wiring of my ca. 1979 Kenwood KT-80 tuner struck me as a bit dodgy. (At least it already dates from a time of double-insulated mains cords being standard, still a relatively new thing then.) That sort of stuff was generally sorted out by the 1990s. With new entries from less experienced makers you never really know, of course.
Double insulation gave lazy designers an 'out' in terms of hum related issues on the typical single ended (RCA) designs of the time.
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.

You could be going all Class I while transformer-isolating all the outputs, but last time I checked, good transformers cost good money and are not generally helping the measurements either. Often, progress is just as much about finding ways to do the same thing more cheaply and efficiently.
(One of my favorite stories in this regard might be whoever found out that the cheap, low-noise but not unity gain stable NJM2122 opamp could be coaxed into making a decent balanced microphone preamp on +/-5 V (possibly the good folks at Focusrite, whose history with the part seems to date to at least the Saffire Pro series from 2009)... the mic input noise levels on cheap USB audio interfaces used to range from meh to bleh.)
 
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