Hello fellow enthusiasts,
My recently built ACA 1.8 amplifier works out great. It seems to operate silently without any hum whatsoever.
When I wanted to feel how hot the heat sinks get, touching the chassis (or heat sinks) resulted in a feeling alike tickling.
So, I switched off the amplifier and waited for cooling down. When I gently touch or stroke the chassis (off, being cold) it feels like the chassis is charged with static electricity.
When disconnecting the 24V power source from the kit the problem goes away. Note: my wall socket is not grounded to earth.
How should I proceed? Is this a problem at all, and how can I measure to pin point if it is and what to do exactly?
Thanks in advance!
Best regards,
Kees
My recently built ACA 1.8 amplifier works out great. It seems to operate silently without any hum whatsoever.
When I wanted to feel how hot the heat sinks get, touching the chassis (or heat sinks) resulted in a feeling alike tickling.
So, I switched off the amplifier and waited for cooling down. When I gently touch or stroke the chassis (off, being cold) it feels like the chassis is charged with static electricity.
When disconnecting the 24V power source from the kit the problem goes away. Note: my wall socket is not grounded to earth.
How should I proceed? Is this a problem at all, and how can I measure to pin point if it is and what to do exactly?
Thanks in advance!
Best regards,
Kees
This is not normally a problem and is a recognised effect on lots of equipment. If you are using the correct Meanwell PSU and it is connected to the mains correctly then all is well.
I get this effect at various times with a laptop, the top of the cooker, the front panel of my Sony Minidisc recorder... the list goes on.
I get this effect at various times with a laptop, the top of the cooker, the front panel of my Sony Minidisc recorder... the list goes on.
Can we just pick up on this point. I've never used the Meanwell PSU so can you say whether it uses a two or three core connection?
In other words is it meant to have a mains safety earth or is it double insulated.
If three (so meant to have a safety earth) then yes, it should be grounded. The effect you notice in this case is HF leakage from the SMPS. It's not dangerous in itself but if you are missing a safety ground at the wall socket then any genuine fault could be dangerous,
This is not static electricity in the amplifier, but on your synthetic clothes, plastic shoes, linoleum or laminate flooring. When you move, you get a charge, and when you touch metal objects, a discharge occurs.
It sounds like you're not earthing the 24V supply output. SMPS generate quite a large leakage current at the switching frequency if you fail to connect mains earth to the output ground. It doesn't take many picofarads at 240V and 30kHz to leak a sensible amount of current - the transformer in a SMPS has leakage capacitance between primary and secondary.
Unless you have an earthed screen in that transformer, or earth the output, you get a mild shock from the output, a fraction of a milliamp typically. Being ultrasonic this current won't be audible through the amp (though it may well be amplifying it and heating up the tweeters).
Unless you have an earthed screen in that transformer, or earth the output, you get a mild shock from the output, a fraction of a milliamp typically. Being ultrasonic this current won't be audible through the amp (though it may well be amplifying it and heating up the tweeters).
I suspect it is 60Hz based on your description, although I am not sure what leakage at 50KHz+ feels like. Tickling sounds more like what I have felt with ungrounded 60Hz leakage. An easy test is if you have something near that is at earth ground, and ground the case to that object with a wire.
Thank you very much for the numerous replies.
When I connect the Meanwell power supply to a properly grounded (earth) wall socket there's no issue.
So no, it's not me being static but indeed leakage from the power supply.
I'll see if I can manage to install proper earthing nearby the audio set-up, which is a good idea in general.
When I connect the Meanwell power supply to a properly grounded (earth) wall socket there's no issue.
So no, it's not me being static but indeed leakage from the power supply.
I'll see if I can manage to install proper earthing nearby the audio set-up, which is a good idea in general.
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What happens with none earthed supplies is there some capacitance between primary and secondary of transformer and this passes a voltage into the circuit.
Yes, and often this deliberately introduced by design using small value caps between primary non isolated and secondary sides. Typically these are under 1nF and are critical safety components with regard to their specifications.
Meanwhile we've moved to a new location with a proper earthing set up. No issues anymore, at all.
I've experienced the same with SMPS power supplies on other builds.
Even the 3 pin PSUs I used had no reference between Protective Earth and the Negative output and I had the chassis floating at 90v WRT Earth.
I could feel the sensation more when running my hand across the amp case - it should have felt smooth, but it felt like there was friction or texture. A very weird sensation!
I ended up bonding that chassis to another that was connected directly to PE and happy days.
Glad to hear you got your sorted too.
Even the 3 pin PSUs I used had no reference between Protective Earth and the Negative output and I had the chassis floating at 90v WRT Earth.
I could feel the sensation more when running my hand across the amp case - it should have felt smooth, but it felt like there was friction or texture. A very weird sensation!
I ended up bonding that chassis to another that was connected directly to PE and happy days.
Glad to hear you got your sorted too.