Since relocating recently I’ve found I’m picking up that irritating mobile phone noise on my HiFi- that familiar tick-a-tick-a-tick-a-tick fzzzzzzzz every few minutes. Switched all phones off and it still occurs. I know there are various ways to guard against interference but what puzzles me is where is it coming from if our phones are switched off? Could it be the neighbours phone or some other device? Any mobile phone/tech experts out there can advise?
ATM : Mobile phone interference on the HiFi
Is it only vinyl or other sources as well? If you unplug everything from the amplifier except the speakers, does it still do it?
Vinyl preamps have massive gain (60-70dB) because the signal coming off a cartridge is tiny (roughly the same level as a mobile phone radio signal) so, when amplified, they are about the same level too.
It could be a neighbour’s phone (the RF signal in omnidirectional and travels miles, by design, as far as the nearest base station). Do you have a mobile phone mast nearby?
Screened leads, ferrites on leads, filters can help. Use balanced connections (usually XLR connectors like those found on microphones) if you can. My PC monitor at work uses an unscreened DVI cable and, if I place my phone on my desk, the screen goes blank every few seconds.
I spent some of my Xmas/NY break running Ethernet cable around my house. Offspring The Younger got a PS4 and, because the WiFi signal is poor in his room, installed a PowerLine adaptor on the mains. I could not play vinyl for the noise, similar to that of a 56k modem.
Let me know how you get on, Doc. This is an area of professional expertise. I have to have something going for me…
Some clues here?
http://www.enjoythemusic.com/magazine/manufacture/0712/
Unlikely to be the carrier of mobile phone noise as the mains impedance is so low (13A 240V) compared to the input impedance of a line input of the amplifier (50mA 2V). But other local grot (e.g. from TV & PC power supplies), then yes.
Hair dryers, washing machines, tumble dryers, light dimmers…
The noise from commutating motors tends to be airbourne RF (each turn creates a small spark & ionising crack, c.f. lighting & thunder) rather than conducting up the mains. Light dimmers, up to a point – depending on coupling from lighting circuit to ring main.
These are usually (best) addressed with shunt capacitors at source, but if Doc doesn’t don’t know where the noise source is, that’s going to be tricky!
Thanks for the advice Fentonsteve. I wasn’t aware the interference could travel that far. According to mastdata.com there’s some sort of Vodafone installation (can’t see a mast as such) about 1/2 a mile away but our old place was much closer to a proper mast on the roof of a church and wasn’t an issue there. We’re on EE and the reception is pretty poor up here actually.
I think the vinyl record player is the culprit. It’s a Technics 1200 where the phono cables are hard-wired so don’t think I can do anything about it?
In which case, there are a few options.
Firstly, establish it is the turntable/leads and not the phono stage of the amp.
Unplug all of the other inputs from the amp. Simulate plugging the cartridge directly into the amp (without any leads) with 100 Ohm resistors soldered across two phono connectors. If you still have the noise, it is not the turntable or phono leads and there’s not much to be done other than to try another amp.
If the amp is not noisy, but gets noisy again when you reconnect the turntable, there are other options.
1. Try some ferrite clamps on the turntable phono leads, placed about an inch or so from the amp inputs. These have the effect of shortening the effective length (at RF) of the cable. They don’t actually filter out any energy, so it’s a bit like squashing a balloon – another noise source might bet louder. Relatively cheap – a few quid. These are what are inside plastic lumps you see on wall-wart leads, DVI cables, etc.
2. Try wrapping the cables in aluminium foil and copper tape. If that works, contact one of the SL1200 pimping places (e.g. Timestep) and ask them to fit double-screened after-market cables to your deck.
3. If using a Moving Magnet cartridge, try a high-output Moving Coil type. These have lower source impedance so are better balanced and less noisy (and, because of lower tip mass, sound better too) but still work into a MM phono stage.
4. If using a MC cartridge, try balanced cartridge transformers (which boost the signal to that of MM level) into a MM phono stage. These specialist transformers tend to not be very cheap.
PM me, I can help you source parts to experiment with.
@fentonsteve
You’re making this up as you go along!
I wish I was… RF compliance is one of the less dull parts of my job, which just goes to tell you how tedious the worst parts are.
RF is best measured away from other sources of noise, which is why I sometimes go to a shed full of posh measuring equipment deep in the Fens.
Puts me in mind of … https://youtu.be/qn9ggmbovVE
Yep. One turnup of becoming my employer’s RF compliance expert is, what with all the time spent in a shed on the Fens, I’ve become a moderate-level twitcher. Is that a Kestrel or a Sparrow-hawk?
Thanks FS. I’m actually running my turntable into a little Spirit desktop mixer and studio monitors (I have more of a home studio setup than a hi-fi tbh). I think that is the culprit as it’s pretty cheap, may be time to invest in a proper hifi amp for my turntable. Not picking up any noise at the moment (sods law) but I’ll try unplugging things when it starts up again.
If it’s intermittent doesn’t that suggest it’s environmental rather than a connectivity problem?
My hifi amp in my music room hums periodically, and it’s always on stand by which is annoying so it hums when it’s off but that’s a design “feature”. Probably nothing I can do about it other than ignore it. It’s 25 years old so probably struggling a bit.
The source of the noise is definitely environmental but could be picked up by poorly-shielded RCA cables or phono stage circuit. It is possible to run phono cartridges in balanced mode, with XLR connectors, but balanced phono stages tend not to be cheap.
The hum your amp might be mechanical from the transformer. During high-demand times of the day (when civilians of the nation are boiling their kettles) the mains becomes less of a sine wave and more of a square. Transformers physically shake if you put a square wave through them. There is sometimes a DC component, too, which saturates the transformer ferrite.
There’s not much you can do, apart from buy a mains power regenerator (think a big PC power supply bolted to a high-powered audio amp, which generates a low-distortion 240V 50Hz sine wave), a bit like a high-spec UPS without a battery.
The phono stages in mixers are generally little more than an afterthought add-on and not well shielded. Try something like the Pro-Ject PHONOBOX (£79), or similar from Cambridge Audio, both available at Richer Sounds.
Do try to isolate the problem first, though. Happy to help.
@fentonsteve thanks – yep – it was the mixer. I solved the problem by purchasing a nice new Amp from Richer Sounds with a decent Phono stage and a nice DAC which can play my ripped CDs from my hard drive – I’m now enjoying better quality sounds without my neighbours mobile phone joining in on percussion.
Hurrah. Coincidentally, I bought myself an upgraded phono stage last week (turns out January is a good month for bagging hi-fi bargains on eBay).
Guys, my head hurts.
This is the kind of thing I encounter almost daily at work. No wonder I’m dull.
After reading this I suggest bring a mates amp in replace with existing stuff. If noise not gone do same thing only with someone else’s turntable.
I have nothing useful to contribute to this thread but may I just thank the contributors for an engrossing read? @fentonsteve your comments are fascinating and impressive.
I love this site!
Thanks, Steve. I will show that to Mrs F the next time she tells me I am wasting my time on the AW.
The first time she saw @Skirky‘s band Helen and the Neighbourhood Dogs, she said “So all that time you spend on the Afterword isn’t wasted after all”.