Grounding an audio cable??? - autocomm & Zumo 550 setup

r12r-don · Post by **r12r-don** » Thu May 17, 2007 8:39 am

I installed my autocomm and Zumo 550 last week.

How I did it:
Nothing special.
- Powered both off the battery using stadard loop posts.
the units are hard wired to the positive terminal on the battery.
- They were grounded on the negative post of the battery.

What happened:
When the two units are running all is well if the Zumo audio isn't connected to the autocomm. However, when I connect the audio cable from Zumo to autocomm I get interference from all the engine electronics like accelleration and braking. Braking is a little chirp and accelleration is a buzzing.

What I tried:
I grounded to the frame, it was worse.

I grounded it to the seat lock bolts, separate bolt for each ground. Better than the frame but same as being ground to negative post of battery.

I thought it was where I ran the audio cable through. so I took a different audio cable and just connected it direct and even held it up away from all engine electronics as a test. Same thing

Then I figured it had something to do with completing the loop and thought maybe the audio being grounded would help. So I looped a small wire around the audio plug to test and sure enough it significantly reduced the volume of the interference.

I've setup lots of stereos but am by no means an audio or electircal pro. I've never heard of grounding an audio cable.

At this point my next step is to open up the shielding of the audio cable and splice the ground properly for a more permanent solution. However, I'm a little uncomfortable having this solution in place and not fully understanding it or being convinced it is the correct configuration.

One thing I haven't tried is taking the zumo power cable out and holding it up as well to see if it is running past something and receiving the interference. Just haven't had the time to pull it out but can try that this weekend if someone thinks that is worth trying.

Any assistance would be greatly appreciated.

Post by **ka5ysy** » Thu May 17, 2007 4:15 pm

It looks like you are actually having two problems: First is a "ground loop" which is a pretty common situation with electronics, and especially audio lines in a lot of equipment. That is probably the buzz you are describing.

Fix: Single point grounding is generally used to cure this problem. The trap here is that you may actually be picking up a ground from the Zumo mount depending on how it is mounted. Try isolating the Zumo off its mound and see if there is any change in the audio situation. If so, there is the loop through the mount hardware.

Something else to try is to replace the audio cable between the Zumo and the Autocomm. It is not unusual for pre-made cables to have bad solder joints and develop ground loop hum. That is why I build my own unless really time-pressed to do an installation. Since you have tried this one time, try one other cable to be certain you dont have two bad ones.

The other noise you are experiencing is probably a combination of the alternator whining and/or the computer used in the ignition. Unfortunately a lot of consumer electronics is not properly RF bypassed and it will give you fits correcting the source of the interference. The usual fix for induced noise is to "bypass" all the leads into an audio amp or distribution with disc ceramic capacitors, usually .01uf. Do this for the power leads also to really clean up pulse noises or alternator whine.

By all means move the power cable around on the zumo, and see if they same situation occurs.

Welcome to the hair pulling club of audio installation debugging ! You should see what we HAM operators run into doing installations of transmitters over 100 watts in mobile and fixed setups with multiple audio sources going in !

Doug

ScooterCop · Post by **ScooterCop** » Thu May 17, 2007 4:26 pm

My Streetpilot 2820 had the same problem, a buzzing sound. Test it with a regular set of headphones on the Zumo. If the buzz is still there, then you just eliminated the Autocomm as the source.

You can get a ground Loop isolator from Crutchfield, which I've heard works on another forum.

I went with Autocomm cable #1314. It has the isolator built into it, but it is a bit pricey. It fixed the problem, but I have yet to run it under the tank to the Autocomm for a permanent install.

Hope this helped.

Post by **HiOSilver** » Thu May 17, 2007 7:52 pm

This is the best way to solve the problem: http://www.crutchfield.com

r12r-don · Post by **r12r-don** » Thu May 17, 2007 8:25 pm

Thanks. This is very helpful information.

I will try unplugging the power and leaving the audio to see if that corrects the problem. If I am reading properly, if the noise goes away that confirms my ground loop problem and the source being the power.
If the noise continues then it is something else and a ground loop isolator will not help me.

I do have a follow on question:
I have yet to connect the audio in cable which will go from the autocom to the zumo microphone in.

Do I need two ground loop isolators: one for the zumo audio in and the one for the zumo audio out? Or will one ground loop isolator do?

Thanks again for all the great tips. This will take what is being predicted as being a rainy Saturday and make it productive.

ScooterCop · Post by **ScooterCop** » Thu May 17, 2007 9:50 pm

r12r-don wrote:I do have a follow on question:
I have yet to connect the audio in cable which will go from the autocom to the zumo microphone in.

Why are you connecting a microphone to the Zumo? If it is for a phone, check the link below:

http://www.autocomamerica.com/files/Int ... mo5501.pdf

r12r-don · Post by **r12r-don** » Fri May 18, 2007 6:18 am

I am connecting the microphone cable to take Autocom voice to the Zumo. This will allow me to take phone calls through the helmet with my existing auto com system. My autocom system is like 9 years old so it doesn't have a blue tooth option. Unfortunately I drew the line at upgrading the autocom system after buying the bike. Maybe next year.

Lost Rider · Post by **Lost Rider** » Fri May 18, 2007 8:02 pm

I just tried a Radio Shack isolator.
It did nothing to help my Streetpilot 2820's hum. I've talked to Garmin about it with no help. I even went into the Garmin store, they couldn't help either. I get the same noise no matter what power source, in the house or on the bike. They said it was common and there's nothing that can be done.
B.S. on Garmin's part.

I guess I could try the Crutchfield one. Any of you have a Garmin, and have actually solved this Garmin problem with the PAC SNI-1/3.5?

Post by **deilenberger** » Fri May 18, 2007 8:52 pm

ChiTown wrote:I just tried a Radio Shack isolator.
It did nothing to help my Streetpilot 2820's hum. I've talked to Garmin about it with no help. I even went into the Garmin store, they couldn't help either. I get the same noise no matter what power source, in the house or on the bike. They said it was common and there's nothing that can be done.
B.S. on Garmin's part.

I guess I could try the Crutchfield one. Any of you have a Garmin, and have actually solved this Garmin problem with the PAC SNI-1/3.5?

I'd suggest looking at "MixIt" products - a friend, John Brown makes them. They are made for motorcycle use and this sort of problem is common with Garmin products (and apparently some radar detectors) and John makes a mixer designed to fix this problem.

http://www.mixitproducts.com/home.html

r12r-don · Post by **r12r-don** » Fri May 18, 2007 9:02 pm

I may be misunderstanding the mix-it. It looks like a great product but seems like overkill to just address the ground loop issue. It does many of the things the autocom already does. I'm going to tinker some more with this tomorrow before I purchase an isolator. I'll post my findings tomorrow.

Post by **iowabeakster** » Sun May 20, 2007 7:17 pm

oops, edited-repeat info.

So I looped a small wire around the audio plug to test and sure enough it significantly reduced the volume of the interference.

Chances are you aren't "grounding" the audio at all, but are creating an ADDITIONAL ground path for the (-) external to the device. This is changing the ground plane, somewhat for the better it seems.

If you were "grounding" the audio signal you would be creating a paralell pathway and would decrease the "audio" as much as the noise (AKA: a short). Meaning you would have to increase the volume and put the output circuitry at risk.

r12r-don · Post by **r12r-don** » Thu May 24, 2007 9:44 am

I bit the bullet today and ordered teh $85 lead from Autocomm.
For my model (PRO-M1) and configuration, the 1300 lead is the correct lead.

Note on what I'm doing:
- powered zumo 550 and autocomm PRO-M1 off the battery
- phone (motorol razr v1 with Verizon) blue-toothed to zumo
- zumo audio is and will be hard wired to autcomm
- autocomm hard wired to helmets

Apparently the lines are isolated three times over inside the lead. The lead handles the cables and isolation for audio out of zumo and the audio into the mic input as well.

For $85 for what I know will be top notch cables AND isolator, I actually don't think it is that much money.

I will let you know how it goes after I receive it and install it.
They are presently out of stock and expect it in their warehouse end of next week.

r12r-don · Post by **r12r-don** » Thu May 31, 2007 8:03 am

A few things:

First, thanks to everyone for the great and quick feedback about my problem. It saved me weeks of troubleshooting and test rides.

Second, a HUGE shout out to Top Gear accessories (http://www.autocomamerica.com). They said they didn't have the leads in stock for the Zumo 550 and would send them as soon as they got them. They showed up on my doorstep last Friday evening, A DAY LATER. Don't know what they did, but am thankful for it.

Lastly, I toiled over saving some bucks or going right to the source to fix my noise problem. I opted for going to the source (you get what you pay for yadah yadah yadah...). I spent $85 for part #1300, the zumo 550 lead for Mic and audio. It works like a charm. As I mentioned before, TopGear tells me the lead is actually isolated three times over. One of the reason it drove up the price.

This story has a happy ending.
And, my recommendation - just get the appropriate lead for your configuration directly from Autocomm. $13k+ (depending) for the motorcycle + $hundreds for the autcomm + $hundreds for GPS ======> Why skimp on $50 bucks to use them all together.