OK - I know this has been visited in the past, with Sat Radio and iPods, but I have a new issue that I would like some advice on...

I previously had an XM Radio RoadyXT in my Camry and had it plugged into the Aux input. I noticed the annoying hiss/whine in the audio and bought a ground loop interference filter to put in line with the aux input cable. This solved the problem with the whine/hiss.

My wife got me the Harman Kardan Drive+Play for my iPod, and I installed it yesterday. I used the same GLI filter, and it got rid of the noise, but it also seems to be filtering out ALL of the bass, making the sound very "thin". I don't understand why this is only happening with the new HK device, and not the old XM radio (which I removed). I tried it without the filter, and the whine is still there.

I am wondering if there are other options out there (filters) that might solve the problem. I thought I read somewhere that there are devices that can be applied to the power side (12v) rather than the audio side. I am also looking for some theories about why the bass is being cut on just the new HK unit...

Any electrical engineers out there that might be able to provide some ideas?

Thanks everyone!

 

Jeff,

It sounds like an impedance mismatch problem. The HK output is probably capacitively coupled (a capacitor is in series with the output) and the input impedance of the GLI filter is working aginst the capacitor to form a high-pass filter.

This can be confirmed (and fixed) by inserting a unity gain amplifier between the two devices. If you have a friend that has some electronics background, the parts to build one would cost about $5-$10.

- two 9v batteries (alkaline) and holder
- an operational amplifier IC (and socket - hooked as a voltage follower)
- a couple of 10 microfarad electrolytic capacitors (25 volt or higher rating)
- connectors for the audio input and output and a small plastic enclosure.

See: http://ourworld.compuserve.com/homep...wden/opamp.htm

It is possible that a "power line filter" could fix the whine in this case, but you'll have to purchase one to find out. Good luck.

Jeffd - EE Professor

 

Where did you get the ground loop interference filter at?

 

I got it from Crutchfield. Here is the link:

http://www.crutchfield.com/S-OqGoQjJ...op&i=127SNI135

And thanks for the feedback, Jeffd.

I might try to find an in-line powerline noise filter locally so I can return it if it doesn't work.

 

How did it work with your XM? I have a Sirrus One I have an issue with.

 

It worked just fine with the RoadyXT. No problems at all.

The HK drive+play is another issue.

 

I bought a Drive + Play also, and was VERY dissapointed by the noise/hissing.

The D+P is in it's box ,right here in my office, awaiting for a solution or a buyer..

If you find a filter that works, please let me know.. I hate to have 200$ + sitting on a shelf..

Bob

 

I will post here if I find one. My wife had ankle surgery today, so I may not be able to try one any time soon. I will try to do it before my return period is over. I really think that it CAN be solved. It is just a matter of finding a solution.

Did you really pay that much for yours? Best Buy has been selling it for $99 for the last several weeks.

 

Spiff

thanks for the update, I will try to see if I can find a solution on my side as well. Let's see who finds it first !

I bought mine on Ebay over 6 months ago.. my overall costs in Canadian Dollars was around 200$.

Future Shop Canada sells it online for 300$ as of today.. what a ripoff !

Ciao !

Bob

 

Update:

I finally got my electrical noise filter installed today, and unfotunately, it didn't help. The whine is still there.

I didn't bother removing it. It was too much hassle to try fixing it.

I don't know what else I can do here. I am afraid that if I go to the dealer they won't be able to do anything (or they will point out the fact that I tapped into the electrical system and blame the problem on me).

I haven't pursued the option that Jeffd suggested, because I would prefer something that doesn't require an additional power supply (the batteries).

Does anyone have any suggestions??

I would like to go back to filtering on the signal (audio) side - is there any way to do this without adding an additional power supply? Or if batteries are needed, do you really need two 9-volts? How long would these last if you never disconnected them?

Thanks again!