Voltage on DENON X3700H Chassis

[mainframe]

I have had it with these motherf***ing Volts, on these motherf***ing frames!!


I've seen it for years. Vintage, modern or new. All these supposed "Class II" electronic devices. And I've got 70V AC here on my 6 month old DENON's chassis.

• From Wikipedia:

1. A Class II or double insulated electrical appliance uses reinforced protective insulation in addition to basic insulation. Hence, it has been designed in such a way that it does not require a safety connection to electrical earth (ground).

Yet, when they are plugged in and running and my arm is reaching over them to plug in a cable, I feel tingling in my arm hairs and in some cases my eyeballs vibrate. So I whip out the multimeter. Plug the black lead of the multimeter into the earth point of the nearest power outlet, and the red lead of the multimeter onto the offending frame. Sure enough, 70-110VAC on the frame.

Whats worse - I've had this with iPhone and iPad chargers, rendering the damn thing unusable while charging because I can feel the voltage.

Yes - this is only "ghost" voltage and while supposedly not harmful, its damn annoying. I have had this on a few previous amplifiers I eventually just move them on. Now I don't know the exact cause of these voltages, but I suspect in amplifiers it may be eddy currents generating in the chassis from being next to a large transformer, (phone chargers are SMPS so I have no idea)

NOW YOU MIGHT SAY just forget about the voltage as its not doing any harm right? WRONG. I plugged an integrated amplifier with an "AV Bypass" function into the denons front pre-outs to use as an external power amplifier. The speakers. Hummed. Like. Crazy. Classic 'ground loop' hum.

Completely unusable.

So, I did a test with a lead with crocodile clips and linked the DENON frame to earth, the hum VANISHED. The integrated amp in AV bypass was dead silent. couldn't detect/hear any issues. The Denon frame voltage vanished.

Anyway that brings me to the solution - convert the device to electrical class I, that is to connect the frame to mains earth. Not only does this make the device much safer (if your house circuits aren't GFLI protected) but the voltage and any external amp hum completely disappears.

-----

So to get to my question, do any of the wiser heads here object to me replacing the IEC mains inlet on the Denon with a 3 pin one and connecting the frame to mains earth? Normally I would do this on any old device, but because the negative terminals for all the speaker outlets on the DENON are electrically continuous with the frame (I assume the frame is being used for all the audio amp ground returns) I am a bit hesitant it may affect performance or cause something to fail.

I've opened the DENON and removed the mains inlet/standby board and found the exact replacement IEC inlet WITH earth terminal from Rich Bay R-30190(B00) and I could just link the earth terminal to the frame support screw on the standby board. Any objections?


TIA.

Disclaimer: I am an electrical engineer but I have limited knowledge of audio amplifier circuits

 

[Kremmen]

I have also experienced a pulsing, tingling sensation when rubbing my finger across the chassis of various bits of audio equipment and often wondered what caused this and whether it is safe. I'm looking forward to responses to your very interesting post from those who can enlighten us.

 

[airborne]

when i touch my QSC PLX ( 3-prong ) i get shocked but i assumed this was static electricity ...

yet i have a whole house steam humidifier maintaining optimal humidity and i don't get shocked touching things that aren't electronics ...

i also get shocked by Benchmark DAC but i use the same plastic ( or "fiberglass composite" if you prefer ) chair when it happens so maybe it's the chair ...

when the HVAC starts i can literally see steam coming out of the vents - that humidifier is a monster - you need a dedicated electrical circuit to run it because of how powerful it is ... it helps with static a lot and helps even more with dry skin etc ...

anyway i am so dumb i never even considered that the voltage might be coming from the amp not from me ...

i have already been telling everybody to only use XLR cables - never RCA cables ( due to ground loops ) - but i guess now i will have to also tell people not to buy anything that doesn't have 3-prong power adapter too ?

then again, i already don't have anything that has a 2 prong power plug because i basically have been following this practice already for ages, even though it wasn't a formal rule or anything. i just consider stuff that doesn't have a ground pin as lower quality.

all my gear either has an external AC adapter or a 3-pin plug.

i suppose having an external AC adapter that has 2 pins is no different than having an internal power supply with 2 pins ...

but at least with external AC adapter there is a legitimate reason for doing it this way - you want to be able to use interchangeable AC adapters and standard plug. on other hand what can possibly be the reason for using 2-pin power cable ? only to save money on the third conductor. but how much does it actually save - $0.5 ? why should i pay hundreds for a piece of electronics that is too cheap to spend $0.5 for proper grounding ?

i think it may be their way to differentiate entry level from higher end models just like in cars entry level models will get steel rims or black unpainted mirrors etc. i doubt they really save all that much by using steel rims versus aluminum ones - it's just their way to hint you should get a more expensive model.

now that i think about it 2-prong cables are typically flat while 3-prong are typically round. there may actually be significant price differential in their cost. a round cable has insulators inside then some kind of padding and then external protection. a flat cable is one piece of plastic - MUCH cheaper. perhaps 3 times cheaper. as such the temptation to use it may be understandable.

my 97 year old grandma got an el-cheapo Insignia microwave for her birthday so she doesn't have to walk all the way to the kitchen to heat up food and can do it in her room. the microwave has a cable that is less than 2 feet long ! cheap hair dryers also have too-short cables. these capitalist bastards really do try to save money by using inferior power cables - either too short or not round or missing ground pin etc.

anyway screw 3-prong IEC - go all the way and do a Neutrik Powercon ! ! !

 

[restorer-john]

Safety and pursuing the best "on paper" specificiations for HiFi have never gone hand in hand.

True chassis earths and star grounding went out the window in the interests of unlinked (via metal chassis and interconnects) 'double insulated' implementations in the 80s and 90s. Basically, you can rule out any type of earth/ground loop in a well designed product if, it in itself, is not attached to mains earth and is not measured with respect to mains earth. Hardly a representative or typical test or implementation in the real world.

Stray (nuisance) currents and shocks similar to what the OP experienced are typical, and yet faulty and potentially dangerous in their ubiquity.

I'm struggling to see any situation where a double insulated, non-chassis earthed piece of Hi-Fi gear, when connected in a system, to other pieces of similar Hi-Fi, can be safer than a properly, chassis-earthed piece of gear. Certainly, stray leakage currents are banished, and sent to ground where they belong.

 

[airborne]

I'm struggling to see any situation where a double insulated, non-chassis earthed piece of Hi-Fi gear, when connected in a system, to other pieces of similar Hi-Fi, can be safer than a properly, chassis-earthed piece of gear. Certainly, stray leakage currents are banished, and sent to ground where they belong.

right ... i mean you can ground the chassis and simply not use that ground in your signal chain.

but that will probably add a dollar or so to the manufacturing cost which means the price you pay has to go up by maybe a few hundred dollars ...

just like if alloy rims cost maybe $100 more to make than steel rims it means you will pay extra $5,000 or so for the car.

or if 20" rims cost maybe $50 more to make than 17" rims it means you will pay another $5,000 for that as well.

their logic is if you're smart enough to know what you need you're also smart enough to make the money to pay for it.

they will sell you trash by default as their philosophy is to make sure you don't accidentally get anything good without paying for it even if it costs nothing to make.

they are in business to make money not to make the world a better place.

they would rather destroy their product and pay to dump it in a landfill than sell it at discount and therefore lower the perceived value of their brand.

 

[JeffS7444]

I have had it with these motherf***ing Volts, on these motherf***ing frames!!

I've seen it for years. Vintage, modern or new. All these supposed "Class II" electronic devices. And I've got 70V AC here on my 6 month old DENON's chassis.

Any possibility that the power sockets in your house are wired incorrectly or otherwise faulty? USA standard is for the narrower of the flat prongs to be Live, and the wider one, Neutral. And N to Earth voltage should be nil. Because the last time I experienced what you're describing was years ago, with older gear which created it's chassis ground by tying one of the power leads to chassis via a high-value resistor or capacitor, and then plugging the device into the power socket the "wrong" way (we're talking older non-polarized plugs here). Even in the 1980s, this was common enough that devices like Namiki's Direction Finder gained some popularity. And even with such older gear, once you plugged it in the correct way, all the symptoms that you described would typically disappear.

 

[mainframe]

I should have clarified - my electrical background is LV up to HV - 50V AC all the way up to 33kV AC. I did some time as an electrician. Nothing wrong with the sockets in my house, and I can still legally rewire houses. Where I am our house mains voltage is 230V AC single phase.

Let me be clear - the voltage on the chassis is not a result of direct connection to the mains. There is no contact or continuity from any mains AC voltage inside the unit to the frame. I understand (the sheer stupidity of) someone grounding the chassis to the neutral. You are right, all it takes is someone to have a socket wired incorrectly or insert the appliance lead the wrong way and you'd get full mains voltage on the chassis. Absolute suicide machine.

Back to the DENON and other references in my argument. The AC voltage on the frame is induced, by means of magnetic fields within the unit. There is no contact or continuity from any mains AC voltage inside the unit to the frame.

You can test any of your audio gear yourself with two prong IEC inlets or flat 2 pin AC leads, just make sure the unit is plugged in by itself and not connected via any means to any other piece of audio equipment. With a digital multimeter on volts AC measure from an earth pin in a socket outlet to the frame of your DUT.

True chassis earths and star grounding went out the window in the interests of unlinked (via metal chassis and interconnects) 'double insulated' implementations in the 80s and 90s. Basically, you can rule out any type of earth/ground loop in a well designed product if, it in itself, is not attached to mains earth and is not measured with respect to mains earth. Hardly a representative or typical test or implementation in the real world.

Stray (nuisance) currents and shocks similar to what the OP experienced are typical, and yet faulty and potentially dangerous in their ubiquity.

John in your opinion, will earthing the chassis have an effect on the device due to the grounding arrangement in the X3700H - being the negatives of all speaker terminals are connected to the frame?

I have a focusrite solo here - I might be able to take some measurements of the Denon before and after.

 

[restorer-john]

John in your opinion, will earthing the chassis have an effect on the device due to the grounding arrangement in the X3700H - being the negatives of all speaker terminals are connected to the frame?

Bear in mind, the voltage you read with your DMM is real, but the current that voltage could support is miniscule. Your DMM likely has a ~10Meg ohm input impedance, so it isn't dragging it down.

That said, earthing the chassis will remove the nuisance tingling you feel on the rear panel/casework etc. It depends how many connected devices are also earthed as to whether you get/create loops through the interconnects between the AVR and the devices. But when it comes to safety, I'd rather be counting on a proper earth connection, screwed to a chassis than relying on the shields of a few RCAs daisy-chained from component to component.

Plenty of supposedly double insulated HiFi gear also comes fitted with a chassis earth screw terminal for the purpose of removing hum. Most AVRs, receivers and amplifiers with phono stages have the terminal on the chassis rear panel. It is expected that it is connected, and, ironically, the entire system then is earthed via the turntable's power lead earth pin...

Back in the day, double insulated gear used to have a message that said "Double Insulated, no not earth" stickers. They were usually plastic encased power tools, some CRT TVs etc. I prefer correctly earthed gear, correctly designed so it doesn't hum. Especially if it has any exposed metal casework.

 

[mainframe]

Ill earth it. I'm getting the ground loop hum NOW with the chassis NOT EARTHED. The hum goes away when I attach a temporary earth.

 

[Gringoaudio1]

Any possibility that the power sockets in your house are wired incorrectly or otherwise faulty? USA standard is for the narrower of the flat prongs to be Live, and the wider one, Neutral. And N to Earth voltage should be nil. Because the last time I experienced what you're describing was years ago, with older gear which created it's chassis ground by tying one of the power leads to chassis via a high-value resistor or capacitor, and then plugging the device into the power socket the "wrong" way (we're talking older non-polarized plugs here). Even in the 1980s, this was common enough that devices like Namiki's Direction Finder gained some popularity. And even with such older gear, once you plugged it in the correct way, all the symptoms that you described would typically disappear.

Same happened to me with an Arcam Diva 350 AVR. House wiring was the problem.

 

[DavidMcRoy]

I've only noticed this when I had no galvanic isolation from cable TV service. Unless I install an isolation transformer ahead of cable entrance, I even have issues, including hum, even through an Ethernet connection if that Ethernet gear is getting a cable TV/wideband feed.

 

[Sokel]

If in Europe that plugs go either way,try to measure it both ways.
Talking about BIG surprises.

 

[Jasperous]

Ill earth it. I'm getting the ground loop hum NOW with the chassis NOT EARTHED. The hum goes away when I attach a temporary earth.

how did you earth it? I'm getting the crackling on my KEF R400B Subwoofer. I'm starting to run at my wit's end trying to fix this.