# Why does my phone hum when I plug it into an amplifier? **URL:** \ **Category:** Factual Questions\ **Created:** [December 20, 2014, 4:24pm UTC](https://boards.straightdope.com/t/why-does-my-phone-hum-when-i-plug-it-into-an-amplifier/707747 "2014-12-20T16:24:20Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Rhythmdvl](https://avatars.discourse-cdn.com/v4/letter/r/85f322/32.png) [@Rhythmdvl](https://boards.straightdope.com/u/Rhythmdvl)\ **Post date:** [December 20, 2014, 4:24pm UTC](https://boards.straightdope.com/t/why-does-my-phone-hum-when-i-plug-it-into-an-amplifier/707747/1 "2014-12-20T16:24:20Z")
(because it doesn’t know the words!) I use a Monoprice 3.5 mm to RCA cable to plug my Galaxy SIII into a simple AuidoSource 100 watt amplifier, which drives a large set of Paradigm speakers. When the phone is plugged in, I’ll often hear a very low hum/buzz from the speakers. This changes with a few things. It’s most noticeable when the amp and/or phone volume is turned up. It goes away (usually temporarily) if things change on the phone, but I’ve found no pattern. That is, sometimes it will go hmmmmmmmFLT if I hit the home or sleep key or change the running app. But then a short while later it will come back. Or it won’t be there in the first place, but starting an app or waking the phone will start it. How do I figure out why it’s doing that and how do I stop it? Bonus question: is the sound at all related to the louder hum that happens when I touch the business end of the cord’s 3.5 mm plug? Is that harmful to the amp? Super Bonus Round question: We want to use the phone as an alarm (this setup is in the bedroom), but we keep getting an “are you sure you want to turn the volume up so high?” warning (and it won’t make sufficient noise unless you click ‘yes’). Any way to disable that? ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [December 21, 2014, 1:04am UTC](https://boards.straightdope.com/t/why-does-my-phone-hum-when-i-plug-it-into-an-amplifier/707747/2 "2014-12-21T01:04:47Z")
Is the hum the same pitch, or does the pitch change? What sort of pitch is the hum? DOes the hum have the same pitch as when you touch the end of the 3.5mm plug? (Doing so won’t usually harm the amp, but if the amp is turned up you may risk your speakers.) There are quite a number of potential sources of interference within a phone - there are multiple switch mode power supplies, and there are also some interesting oddities that than occur in some DAC designs. ---
**Author:** ![analogqueen](https://avatars.discourse-cdn.com/v4/letter/a/898d66/32.png) [@analogqueen](https://boards.straightdope.com/u/analogqueen)\ **Post date:** [December 21, 2014, 1:15am UTC](https://boards.straightdope.com/t/why-does-my-phone-hum-when-i-plug-it-into-an-amplifier/707747/3 "2014-12-21T01:15:38Z")
Not grounded. Here’s a link on how to get rid of the dreaded “Mains Hum” > **[Ground Loops - Eliminating System Hum and Buzz](https://www.audioholics.com/home-theater-connection/ground-loops-eliminating-system-hum-and-buzz)** > > Got an annoying hum or buzz in your audio system? You likely have a ground loop. This article helps you diagnose the problem so it can be eliminated. Don't put up with hum. Read this article! ---
**Author:** ![Rhythmdvl](https://avatars.discourse-cdn.com/v4/letter/r/85f322/32.png) [@Rhythmdvl](https://boards.straightdope.com/u/Rhythmdvl)\ **Post date:** [December 21, 2014, 9:36am UTC](https://boards.straightdope.com/t/why-does-my-phone-hum-when-i-plug-it-into-an-amplifier/707747/4 "2014-12-21T09:36:04Z")
The pitch is constant. Tinnier than when I hold the jack directly, but I think that’s a fullness issue, not the pitch. It’s close to what I remember as sounding like that buzz from a ground loop issue, but it’s been years since I heard it. The amp is two-prong and when the phone has been plugged in, it’s with a charger that plugs into an ‘outlet’ on the back of the amp. Would either of those negate the possibility that it’s a ground loop buzz? If not, is it as simple as [one of these](http://www.amazon.com/Raptor-GL15-Ground-Loop-Isolator/dp/B0009O19LQ/ref=pd_sim_e_1?ie=UTF8&refRID=0WS3TCN6JPT3QW7D19SP)? ---
**Author:** ![Bill\_Door](https://avatars.discourse-cdn.com/v4/letter/b/50afbb/32.png) [@Bill\_Door](https://boards.straightdope.com/u/Bill_Door)\ **Post date:** [December 21, 2014, 5:17pm UTC](https://boards.straightdope.com/t/why-does-my-phone-hum-when-i-plug-it-into-an-amplifier/707747/5 "2014-12-21T17:17:14Z")
Years ago getting rid of a hum was often as simple as rotating a power plug 180 degrees to flip the neutral. Now every damn cord and outlet you find is polarized and you can’t flip most plugs. Once again convenience yields to safety. ---
**Author:** ![vd](https://avatars.discourse-cdn.com/v4/letter/v/b19c9b/32.png) [@vd](https://boards.straightdope.com/u/vd)\ **Post date:** [December 21, 2014, 8:45pm UTC](https://boards.straightdope.com/t/why-does-my-phone-hum-when-i-plug-it-into-an-amplifier/707747/6 "2014-12-21T20:45:35Z")
Because it doesn’t know the words? ---
**Author:** ![busterpickle](https://avatars.discourse-cdn.com/v4/letter/b/258eb7/32.png) [@busterpickle](https://boards.straightdope.com/u/busterpickle)\ **Post date:** [December 22, 2014, 4:26pm UTC](https://boards.straightdope.com/t/why-does-my-phone-hum-when-i-plug-it-into-an-amplifier/707747/7 "2014-12-22T16:26:45Z")
> [@Bill\_Door](#): > > Years ago getting rid of a hum was often as simple as rotating a power plug 180 degrees to flip the neutral. Now every damn cord and outlet you find is polarized and you can’t flip most plugs. Once again convenience yields to safety. Assuming all the plugs are polarized then there is no need to rotate the plugs. Any ways, does the hum only exists when you have the phone charger plugged in? I’d try both, plugged and unplugged, see if there is a difference. Another real possibility, as I look at images of your amp, is that it uses a two-prong plug. Since way back in the day, I always have a chassis ground. Either by using separate ground wire to a screw on the chassis to the center screw on the wall-plate. Or, what I prefer to do, is replace the cord with a three-prong cord and take the ground to chassis from there. ---
**Author:** ![Dag\_Otto](https://avatars.discourse-cdn.com/v4/letter/d/439d5e/32.png) [@Dag\_Otto](https://boards.straightdope.com/u/Dag_Otto)\ **Post date:** [December 23, 2014, 2:40pm UTC](https://boards.straightdope.com/t/why-does-my-phone-hum-when-i-plug-it-into-an-amplifier/707747/8 "2014-12-23T14:40:26Z")
> [@Rhythmdvl](#): > > If not, is it as simple as [one of these](http://www.amazon.com/Raptor-GL15-Ground-Loop-Isolator/dp/B0009O19LQ/ref=pd_sim_e_1?ie=UTF8&refRID=0WS3TCN6JPT3QW7D19SP)? That should work. Another option might be to take the AC phone charger out of the system and use an external battery to charge your phone at night. A bit more inelegant than the filter but you would then have an external battery which can come in handy. Just charge the external battery during the day. ---
**Author:** ![Rhythmdvl](https://avatars.discourse-cdn.com/v4/letter/r/85f322/32.png) [@Rhythmdvl](https://boards.straightdope.com/u/Rhythmdvl)\ **Post date:** [December 23, 2014, 7:03pm UTC](https://boards.straightdope.com/t/why-does-my-phone-hum-when-i-plug-it-into-an-amplifier/707747/9 "2014-12-23T19:03:11Z")
Haven’t experimented yet, but if the buzz remains after the phone is unplugged, does that point to something other than a ground loop, or is the evidence just that strong that it is? Or is it possible that the issue could persist whether or not it’s plugged in?