Wondering if anyone else has resorted to something similar?
I have been noticing some ‘tingles’ on the exposed metal across my devices. According to my multimeter I had about 9VAC on all the grounds. Not sure why…
This pulls everything to earth.
I hope it is REALLY impossible to plug that ground prong into a live socket…
(I know it is bigger, but it’s just a thin piece of plastic which define de size of what can be plugged in the live ones… and everybody knows how sturdy thin plastic is !)
Measured relative to what?
Measured against earth. I was picking up between 6-9vac depending on which devices I unplugged.
I was definitely picking up a ‘sensation’ when touching the metal, sort of a slight vibration that was sometimes like a mild prickle. Just enough to make you want to move your hand away. Which was what made me investigate…
There’s a lot of different devices all plugged in, none of which have a path to earth.
I had done some troubleshooting and thought initially it was an issue with the budget guitar pedal power supply I was using, or the second hand and aged budget mixer. I ended up trying every combination of things being plugged in and nothing resolved it.
But I realised I was previously running out to an amplifier with an earthed chassis ground, whereas now I’m going to powered speakers.
I connected the chassis to earth as a test, and the sensation went away. So I’ve ended up doing this for now.
I should emphasise that it’ll be a temporary fix.
You probably could force it into a live hole, but you’d have to really, really want to… and I don’t. In addition to being physically challenging, the plug would also have to be sideways.
When I’ve built devices for other people, I’ve used an external transformer and ran earth to the chassis via a three pin kettle lead, rather than the cheap wall warts I’ve used for my own bits. In the near future I’ll pick up a transformer and convert the two synths - one would be more than powerful enough for both.
If anyone has any other troubleshooting tips I could try or has a similar experience, I’m up for trying to work out a solution.
Those using 12vac wall warts, do you just ensure there’s no exposed metal or do you run a separate earth? Or do you just not have the same issue?
I have two synth cases powered by wall warts, with no deliberate connection to earth. The third is powered by a Bel DC power supply, 3 conductor mains powered, and I think it too has no connection from output ground to earth.
I also have a Moog Mother-32 and a Behringer 2600 both of which operate off (manufacturer supplied) wall warts, have exposed metal (the jacks), and have no connection to earth. Nothing I can see in the manual suggests an earth connection is needed.
None of these have given me any “tingles”. All but the 2600 are in the basement, so the (concrete) floor is in good contact with (literal) earth. Though typically I’m wearing rubber sole shoes.
I suppose I should measure the voltages. But I haven’t had any problems of that sort.
You should not encounter this issue. It sounds like there is something wrong with one of your power supplies. When you say that you have “a lot of different devices all plugged in,” do you mean patched together? If so, have you checked the individual wall warts/supplies to see whether they are behaving themselves? Are you drawing too much current from one or more of them? Have you measured your (alleged) 0V on each device relative to earth? You could expect some noise with cheap power supplies, but nothing remotely like 6-9V. If your synth is not patched into all of those different devices, but you are getting that amount of AC solely from your synth power supply, it sounds like you should stop using it until it’s fixed.
If your power supply is wall wart > rectifier > capacitors > regulator, are you are getting ±12V from it relative to what should be 0V? Is that “0V” still 6-9VAC when you have unplugged all of your modules?
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My system is two DIY synths, one modular one not, both powered by wall warts. One runs straight into an EHX Memory Man clone.
These run to a Behringer mixer, which runs out to Presonus powered speakers.
In the mixer effects loop, I have an EHX Freeze and a Reverberation Machine clone, both powered by the same guitar pedal power supply.
I have a Casio SDP-110 keyboard, which connects to the synths via a Dore midi host, and I sometimes use an iRig 2 midi device and an iPad.
The devices all share ground via audio cable shields.
I’ve done some further digging - I switched off and unplugged all my devices, then plugged them in one at a time.
There seems to be an issue with the three SMPS devices I have plugged in. If I plug either my keyboard, the speakers, or the guitar power supply, I get AC on the grounds. Actually measured 100VAC relative to earth today, so whether whatever is wrong is getting worse, I’m not sure. Sure would like to figure it out though.
Picture is my synth chassis relative to earth with just the guitar power supply plugged in. It’s the same regardless of which of the three mentioned devices I plug in.
From reading about a bit, it sounds like the ‘tingling’ I’m describing is known as ‘touch current’ and is something that occurs when you don’t pull any exposed metal grounds to earth?
I can do that, and am, but if there’s something else I’m missing that could cause an issue further down the line I’d like to know.
Ive checked the sockets with a tester, tried powering the system from a different socket, and tried different extension cables.
Is that JUST the keyboard, speakers, or PSU? Without the wall wart supplies, or with?
If you disconnect the audio cables, do all grounds still show voltage?
What’s the simplest configuration, with fewest devices connected or powered, that shows the problem?
This is potentially life threatening. Be very very careful, and if you are not sure you know what you’re doing, turn it off, unplug it, and leave it that way until someone with electrician qualifications looks at it.
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I would really double that. If this is real ( as in ~100V live), you should really stop using it until it is safe to do so.
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I pick up something when anything is plugged in. But my linear power supply devices show between 5-7vac, whereas the smps devices show 90-100vac.
Plugging in any, and only one of, my powered speakers, keyboard, or guitar pedal power produces the higher reading.
Reading about smps devices led me to the concept of ghost voltages, which are read by high impedance multimeters but not ones with low impedance settings (which mine does not have…). If I put a load from a resistor in parallel to simulate this (as suggested here) the voltage drops from 90vac to 0.1vac.
If I remove the resistor and change everything over to measure current, the multimeter doesn’t pick up anything at all.
I did also wonder about an issue with the neutral wiring, though the socket tester didn’t show anything. I can’t find my proper probes for the multimeter, just the clip style ones, so have ordered another pair. When they arrive I’ll test the socket at the wall with the meter to rule that out too.
Actually I have an old filament light bulb somewhere I used to use as a current limiting device when fixing valve amps…
I could connect that between the chassis and earth to see if it lights up.
The filament light bulb does not light up if inserted between the chassis and earth.