E36 high pitch whine through speakers:GROM audio interface. HELP!

[TylerG21]

Hello there everyone,

I have googled and searched everywhere to see if there was a real or simple fix for this and all I have read is that its a grounding problem. I bought the GROM audio usb-2 android model for my e36 with the behind the radio cable. It worked as I could hear the music coming from my tablet through the speakers, but there was a very high pitch sound that fluctuated with rpm/speed that came through the speakers as well. If the rev's get higher, so does the sound. So, I contacted GROM audio, and they sent me a new box. Still got the same sound. They then proceeded to send me a new cable. Same sound. I then decided to order a new cable that connects to the CD changer cables in the back of the trunk. Doing this took away a large amount of the intensity of the sound, but its still there. I can deal with it for now because i am able to turn the volume up more without hearing more of the sound, but if I were to turn off the radio, I wouldn't be able to deal with it.

Now, I am curious if anyone has experienced this with a similar interface and has had any solutions or knows how to fix this. Do I need a new alternator? I have a 99 328i very that has the 80amp alternator which I think may be too low for a convertible? I read people talking about ground loop isolators, but didn't get many results.

If there is any useful information you may have, please help me out!

Thank you!
Tyler

[MarcoZandrini]

You alternator's capacity - 80 amps - is fine. The problem, as you have noted, is a ground loop.

Questions:
- is the whine present when you're not using your tablet?
- where in the car is the Grom interface unit installed? It could be picking up interference.
- where is the Grom's ground connected to the car? It should be using an audio ground such as the head in it's ground.

[TylerG21]

You alternator's capacity - 80 amps - is fine. The problem, as you have noted, is a ground loop.

Questions:
- is the whine present when you're not using your tablet?
- where in the car is the Grom interface unit installed? It could be picking up interference.
- where is the Grom's ground connected to the car? It should be using an audio ground such as the head in it's ground.

-yes, if i turn off the tablet music then i still get the high pitch sound.

-right now it is mounted in the rear in place of the cd changer(i got a cable that connects to the original cd changer plugs) . I dont have wires running to the front of the car (yet).

-Theres two available cables for the BMW's, one is for behind the radio where i tapped into the radio harnesses ground, bus, and power wires, and has a plug that plugs into the cd changer behind the radio. I got an insane amount of high pitched feedback so i uninstalled that cable and proceeded to buy and install the cable that goes in the rear of the car in place of the cd changer. So the ground wire on that has to be connected to the radio ground as well i assume. This cable however has a small box which i believe is a filter. Using this cable reduced the noise considerably, but the noise is still there.

[Mark185]

I use GROM audio adapter with my E39 radio and have no noise. The electronics are very similar to your car. I primarily listen to FM and USB stick with recordings I made and I have no alternator whine. Do you have the noise when the GROM is not connected to anything other than the car radio? How are you powering the tablet and how are you connecting it to the GROM? If you are powering tablet from cigarette outlet adapter and plugging into GROM with wire from headphone jack on tablet, the source of your problem is very likely the tablet power source. Does the whine appear when you run tablet off its internal battery power?

[TylerG21]

I use GROM audio adapter with my E39 radio and have no noise. The electronics are very similar to your car. I primarily listen to FM and USB stick with recordings I made and I have no alternator whine. Do you have the noise when the GROM is not connected to anything other than the car radio? How are you powering the tablet and how are you connecting it to the GROM? If you are powering tablet from cigarette outlet adapter and plugging into GROM with wire from headphone jack on tablet, the source of your problem is very likely the tablet power source. Does the whine appear when you run tablet off its internal battery power?

This is the GROM unit i have-

http://www.gromaudio.com/store/andro...the_radio.html

The unit has an aux and micro usb coming from the box to receive the audio from the tablet and power it at the same time. So i am not currently tapping into anything to power the tablet, the box is doing that itself. My fm/am works great, its only when i turn it to the cd changer do i get the sound with the grom connected. Im going to check and see if it will make the same noise with the original cd changer installed. And the whine does still occur whether its connected just the headphone jack and the micro usb, or just the headphone jack.

[Mark185]

This is the GROM unit i have-

http://www.gromaudio.com/store/andro...the_radio.html

The unit has an aux and micro usb coming from the box to receive the audio from the tablet and power it at the same time. So i am not currently tapping into anything to power the tablet, the box is doing that itself. My fm/am works great, its only when i turn it to the cd changer do i get the sound with the grom connected. Im going to check and see if it will make the same noise with the original cd changer installed. And the whine does still occur whether its connected just the headphone jack and the micro usb, or just the headphone jack.

I am thinking that the connection in the trunk may be the problem. Mine is connected directly to the back of the radio and the actual GROM unit is right under the radio in some free space in the E39 dash. Cables are very short and this probably helps noise immunity. This also means you may not have a ground loop. Ground loop happens when there is a difference between the ground at the radio and the ground at a signal source or amplifier. One or both of their grounds are at a voltage other than zero when referenced to the alternator ground connection. When grounds are not at equal potential, current flows between them and you hear it as alternator noise.

Never mind, I just re-read the first post and see that you started with a direct radio connection.

[M3C]

Same issue here with my E36, have Grom USB3 behind the radio version, the wine issue started only after adding Grom, there is no wine (high pitch) when listening from stock BMW radio CD source or AM/FM, only when switching to Grom USB source I can hear the engine wine.
Replacing cables and the unit did not help, also their noise filters did not help.
After years I'm back to their support asking for a solution, it does not appear they know or are willing to resolve.

[rallypanam]

Any resolution? I’m looking to add a grom unit to my e36/7... but don’t want to run into any feedback issues.

Same issue here with my E36, have Grom USB3 behind the radio version, the wine issue started only after adding Grom, there is no wine (high pitch) when listening from stock BMW radio CD source or AM/FM, only when switching to Grom USB source I can hear the engine wine.
Replacing cables and the unit did not help, also their noise filters did not help.
After years I'm back to their support asking for a solution, it does not appear they know or are willing to resolve.

[jamrobin]

I have the Grom unit with USB, Bluetooth, and Aux ports installed behind my radio (with USB and Aux sockets installed in the center console). I had a slight whine (matched to engine RPM) when I first installed it but I beefed up the alternator ground, got rid of the Grom vampire taps in favour of soldering the connections and it's now completely gone. I expect the grounding in your car somewhere... alternator, block to chassis, or battery to chassis (or all of them) should be cleaned up and any deteriorated wires replaced.
It's also possible that your alternator is dying... should be rock steady 14.4V as long as the engine is running. If you've added amplifiers or any other new current draw (projector xenons) you should probably not have the basic 80A alternator...

[M3C]

No resolution as of now, got their current noise filter yet to be connected and see if resolves. Nothing aftermarket added, have original factory alternator, chasing any potential grounding issues can be kind of complicated and not sure if that is the issue.

[bmwstephen]

how do you go about hookin up their noise filter? doesn't seem to have any instructions

https://gromaudio.com/store/accessor...se-filter.html