Hi,
I’ve had a problem with a fairly loud 50Hz hum coming from the speakers of my home audio system, whenever my GivEnergy inverter is switched on. (I have another stereo that emits a similar hum from its chassis when it’s on, but not the speakers.)
The amp went back to the distributors, who said after testing it that it was working as expected. While i might otherwise take that with a pinch of salt, the fact that it (and the chassis hum from the other machine) stops when the inverter is switched off seems to pretty clearly indicate that the problem is being caused by some sort of electromagnetic interference from the inverter.
Does anyone have any experience with this? Does it indicate that my inverter is faulty or might have been installed incorrectly? Can anyone recommend any filters or similar that might work? (I’ve tried a couple of things, including one that the amp supplier sent as a trial, to no avail. )
Many thanks in advance,
Gareth
How close are your inverters to the amps?
Are you running your home on the EPS circuits of your inverter?
Personally not heard of that issue before, sorry
Thanks, Geoffrey. The inverter is in the loft and the amps are on the ground floor (two-storey house).
Assuming EPS = Emergency Power Supply, we don’t have that. The inverter is full-time grid-synced only.
strange, those were the obvious sources of possible interference
you said that the noise comes when the inverter is on, is it when the inverter is charging/discharging, literally just turned on and the batteries idle, and any correlation to solar generation?
when the solar is generating or batteries are discharging the grid voltage in your home will get pushed up a little and I was wondering if that was what your amp was susceptible to? You could measure that with a volt meter
wonder about one of those electrical noise suppressor plugs or extension leads you used to get for computer equipment?
It’s the same whenever the inverter is switched on. No correlation with whether it’s charging/discharging/idle; no change in the pitch or volume of the noise depending on which of these states it’s in. The activity of the solar - nor indeed whether the solar inverter is switched on - also makes no difference.
I looked at the grid voltage. It was reading very high, particularly when sunny and cold, apparently because there are quite a few solar installations in the estate. I managed to persuade the DNO to come and fix it. No change to the amp issue.
Re filters, the supplier of the amp sent out an Audiolab DC Block 6 to see if that helped. (This was actually before I’d realised that the problem was associated with the Giv-AC, because in my testing to that point I’d stupidly only turned off the solar inverter at the consumer unit, thinking both inverters were on that circuit - i blame the installer for not labeling the breakers! 
) Again, no difference at all.
I’m starting to wonder whether a filter should be installed close to the inverter, on the line from it to the consumer unit.
“no variance with volume control” - so even with the PrePro disconnected you hear the hum. Bit of a pain, but is it possible to transport the PA and Speakers to another room (i.e. different mains circuit). Maybe even a neighbours house, too?! (cf your concern about the relatively high Vac in your area.)
“I don’t think I’d describe it as having a buzz” - should be pretty clear to hear if it’s got a “high”-frequency (100Hz / 150Hz, etc.) element to it. As long as it’s just a low ‘thrum’, then it’s just pure 50Hz (so no rectification occurring somewhere).
There’s no noise if no source is plugged into the amp. I suspect this is because it essentially has a ‘sleep’ mode if no input signal is detected, though.
To be clear, the high VAC issue has now been fixed by the DNO - grid voltage readings per both my solar and Giv inverters and a clamp multimeter are consistently within an acceptable range.
Re moving to a different room, I have tried running it through an extension lead from a socket on a different main. No change. I could try running a longer extension lead from a neighbour’s house, I suppose. Moving everything will be very tricky, to say the least. I’m not really sure the value of this, anyway, as the problem is so clearly associated with the Giv inverter? Will running it noise-free at another location tell me anything that switching the inverter off at the consumer unit hasn’t already?
Buzz: yeah, there’s no discernible high frequency component.
There is a bit more information about the power amp that I’ve not mentioned previously for simplicity and because I don’t think it changes the fact the problem stems from an interaction between the inverter and this particular amp: it’s modular, with some channels run by mono, single-channel modules and some by dual-channel stereo ones. Both types use A/B class amps. The ones on the mono modules are OK. It seems that there’s something about the stereo module design in particular that interacts with the noise being put out by the inverter. I’ve tried swapping some speakers around and the problem is still linked to the module type so it’s doesn’t look like it’s anything to do with the particular speakers or speaker cabling.
I’m pretty sure there’s something about the design of these that is part of the problem - my old AVR (D-class, driving the same speakers) didn’t have this problem and I’ve not noticed problems with other stuff in the house (other than the chassis noise from the other device).
I’m increasingly starting to think that the inverter is turning the wiring of the house into a transmitting aerial that’s emitting EMI that the amp modules are sensitive to. Apparently, hammies often face the same problem. This would explain why placing a filter on the amp’s power cable wouldn’t sort the problem and is why I’m increasingly thinking about whether some kind of filter needs to be installed near the inverter.
So, you’re descending into the murky (not to say black magic) world of RF/EMI. Sorry I couldn’t help, and I wish you the best of luck. Let us know how you get on…
One thing I will say, if the issue does turn-out to be caused by the Giv inverter, then that might have implications for their CE compliance rating.
Or the amp rating. EMI compliance works both ways…
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I’m not expert but could you try and wrap a cardboard box in tinfoil and place said amp in the box for testing purposes. In essence a DIY Faraday cage to confirm your EMi interference logic. Even if it just reduces it. Along with a surge protector or even a small computer ups which would should clear up the sign wave for power going into the device.
Just an idea.
Bob
one thing to try is add a ferrite to the Amp’s power input. See if it changes.
That way you know its coming in via the power supply
Personally I would first look at ground loops rather than interference. Can you provide a block diagram for your system - what units are there and what’s connected to what? Is the power amp monoblock? Is there a preamp and if so is that monoblock? Is it balanced (XLR) or single ended (RCA).
I would work backwards through the system. I’m assuming that the speakers are passive as opposed to active (powered) and that there’s no hum in the speakers themselves (eh with the speaker cables disconnected.
With the preamp off but connected, volume zero, all sources disconnected (cables out) from the preamp, power amp on - is there hum?
Then connect one source to the preamp leaving all others disconnected, make sure that source is selected in the preamp - is there hum?
Did anything change in the system at the same time the Givenergy installation happened? Did it hum before? Did the installation result in separate circuits and are any of the components of your system on different circuits?
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Hi Mick,
Thank you for your message. It’s timely, because I’ve been replying to GivEnergy’s latest email on this subject.
I’ve been through all of these things:
Block Diagram:
- this isn’t really relevant, as the same problem happens even when I isolate everything except (1) Marantz PrePro plugged into (2) the Emotiva Power Amp. I’ve also tried plugging a small audio mixer into the Power Amp instead of the PrePro. No change at all.
Speakers are passive (plugging powered speakers into a power amp might be … interesting) and they don’t make a noise when powered by the old AVR, so I’m confident it’s not them.
With the preamp (or mixer) off but connected, volume zero, all sources disconnected, preamp and power amp on, there is hum (if the GivAC’s breaker is closed). For that reason, the “conect one source” test that follows doesn’t seem relevant.
Group loops: I’ve done quite a bit to rule this out:
- connecting the bodies of the PrePro and Power Amp together with a wire;
- ensuring both are plugged into the same power outlet (when no other sources plugged into the prePro
- most recently, powering both the PrePro and Power Amp using an (unplugged) UPS.
No change from any of these tests. I’m fairly confident it’s not a ground loop.
The GivAC installation predates the amp and, as noted above, all of the hifi system components are on the same electrical circuit (and I’ve tried them connected to the same outlet).
The UPS test, which I did in the last couple of weeks, reinforces my view that this is caused by some kind of EMI being emitted through the house’s wiring. I’m really struggling for any other explanation.
Do you have an oscilloscope? If so you might be able to see 50 or 100Hz on the mains ring.
Obviously, don’t go sticking any probes into mains sockets unless you know what you’re doing.
Even if 50/100 hum was present on the mains I would expect the PSU filtering to kill it dead. Since I retired I design and build my own amplifiers and speakers - I wouldn’t call myself an expert but I know more than the average person for sure. The filters I use would kill anything above 10Hz for sure. My amps are valve based, low power output (5W at most) and the speakers I make are around 99dB sensitivity at 1m. Hum would be a disaster if it got through.
I would be very surprised if this turns out to be a Givenergy problem. I won’t rule it out, but I just don’t see it.
Where are you based?
For completeness, the hum from the hifi is 100Hz, according to the oscilloscope app I tried a few months ago. Are you asking me to test the frequency of my grid voltage? I don’t really get what that’s going to tell me. Obviously it’s at ~50Hz. Please see the details I shared above about some of the local grid frequency issues, which have now been solved. (I’m in central Scotland, WFIF.) Am I missing something here - what would I be looking for from an oscilloscope test other than confirming the grid freq?
Re PSU filtering, unless I’m missing something it can’t be something that’s getting into the Amp through the mains supply/PSU, because it still happens when it’s being powered by a UPS. Again, am I missing something here?
Can you please expand on why you don’t see that it can be a Givenergy problem, given that it only occurs when the GivAC breaker is closed? I can see that there’s something about the Amp that makes it more susceptible to something, but surely that has to be something that’s being produced by the GivAC?
Just to add, I have been thinking about installing some filters on the line between the GivAC and the consumer unit … but there be dragons!
I was thinking of using the FFT function to see if other frequencies are being injected, which is what I thought you were suggesting.
My comments re filtering were me trying to say I don’t think the Givenergy can be injecting 100hz hum via the mains circuit. Even if it were injecting such frequencies they surely wouldn’t make it through the power supply filtering.
The only other way would be by induction but
a) that would require the frequencies to be present on the mains circuit and
b) it would require close proximity between the two sets of wires
I can’t explain why closing the inverter RCD causes the hum, but I really don’t see how it could be passing frequencies in to the amp directly or by induction.
Sorry I know that’s not helpful. Watching to see if anything comes from either your installer or Givenergy.
I beleive you have a hybrid & 2x batteries. Is it purely a problem when the inverter is on - does switching the PV off, batteries off but leaving inverter on still produce this hum (which may go some way to narrow down which side of the inverter this ringing is coming from.)