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#79038 - 09/03/2002 19:50 Pls Help with noise in boxster
sendero
journeyman

Registered: 04/01/2002
Posts: 74
Loc: Seattle, WA
To start, I did read the FAQ on ground loop problems, but the troubleshooting guide it points to suggested using the factory ground connections, which I am dong.

Here is basically my setup
EMPEG --> CDR220 --> AudioControl EQX --> a/d/s amp
The empeg power connections are tapped into the factory wiring for an option cell phone. (12v+, 12v switched, ground).

Here's my problem:
When I first installed my Empeg, I disconnected the factory radio's RCA outputs and instead used the Empeg. It was the only music source and things were great, no noise, just clear music.

Last week, i got the parts that allow me to use the AUX input on the boxster's factory radio. Hooked it all up and it works for sound ok, but not when listening to the empeg.

When playing the empeg thorugh the AUX input, I get horrible engine noise whine. I tried adjusting the Empegs output volume, but that did no good.

Has anyone else run into this issue? I did a search but couldn't find specific details on how to fix it.


Thanks, in advance.

_________________________
Rio Car 30gb
2000 Boxster S, <img src="/ubbthreads/images/graemlins/cool.gif" alt="" />

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#79039 - 10/03/2002 12:32 Re: Pls Help with noise in boxster [Re: sendero]
Neo_to_Rio
journeyman

Registered: 02/01/2002
Posts: 57
Loc: Silicon Valley
Sendero,
I suggest you do a search on users ellweber and clownburner in both the technical and installation forums. All three of us have done installs in our Boxsters with similar initial alternator whine and ground curent noises from the Empeg (easiest to hear when the engine is off).

You can get whine and other ground loop noise down to very low levels with aggressive (I mean AGGRESSIVE) grounding between the Becker and Empeg chassis. This means one or more heavy gauge wire or braided straps bolted to the Empeg sled and either bolted or pressure fitted at the Becker frame. BTW, it's a lot easier to work on and reinstall the Becker if you remove the A/C panel (or cupholder) above it. An additional high quality power line filter to the Empeg can help a little more with Empeg DC current noises. I ended up using a DC-DC inverter to power the Empeg and it's dead silent (but probably overkill for all practical purposes).

In both approaches, you'll still need to be very careful about routing the RCA cables (ellweber used only a male-to-male adapter to minimize signal path) between the two units since there are a number of noise sources in the console that can easily inductively couple to the audio cables.

BTW, you can also use ground loop isolators (Crutchfield, Radio Shack et al) to connect the audio. With these, you can pretty much ignore grounding issues. But these transformer coupled devices degrade the audio quality; especially at the low end (my bench tests confirmed this on the Radio Shack coupler) and still require careful routing to avoid inductive pickup that will cause alternator whine and general switching current noise.

Hope this helps. Good luck!

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#79040 - 11/03/2002 12:39 Re: Pls Help with noise in boxster [Re: sendero]
bodybag
addict

Registered: 07/03/2002
Posts: 504
Loc: Southern California
I have the RioCar in my '97 Twin Turbo, same problem. Ended up using a 12 gauge wire from the Rio mounting sleeve to a solid grond on the car, whine problem solved. Once the whine was gone I did have slight but noticable engine noise which I got rid of with a noise filter on the constant power lead.
BTW, junk the Becker and get a tuner module for the Empeg, I had nothing but trouble with the factory Becker unit and CD player/changer. I'm a happy camper now.
_________________________
Bodybag - So Cal
Not a Whiner any more!!!

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#79041 - 15/03/2002 18:51 Re: Pls Help with noise in boxster [Re: Neo_to_Rio]
ClownBurner
member

Registered: 05/09/2000
Posts: 174
Loc: Irvine, CA USA
FWIW, if you do end up needing a filter/isolator (I did, because I didn't want to spring for a DC-DC inverter), use the PAC SNI-1 and not the Radio Shack. I did some frequency tests with a RTA and determined it had 0 (!) affect from 25hz (my lf cutoff) to 19.5kHz (the highest the microphone on the RTA would measure reliably).

Oh, and if you can, Junk the becker, it's way more headache than it's worth. If I had it to do over again, it'd have been the FIRST thing I ripped out and I would have more hair left.

PS: Neo, out of curiosity which inverter did you end up with??
_________________________
_____________ James Mancini

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#79042 - 16/03/2002 12:05 Re: Pls Help with noise in boxster [Re: ClownBurner]
Neo_to_Rio
journeyman

Registered: 02/01/2002
Posts: 57
Loc: Silicon Valley
ClownBurner, although the frequency response of the Radio Shack isolator fell off at the lower frequencies, the most damaging effect was a marked increase in distortion below about 100Hz. This wouldn't show up on your RTA, but would on your ears. I didn't bench test the PAC unit, but would suggest either measuring it's low frequency distortion or giving it a critical A/B listenening test in the low frequencies.

Using the AUX in on the Becker was a headache, but extreme grounding between the Becker and Empeg chassis or a DC-DC converter can make it work without resorting to an isolator.

I used a 12V converter from an old laptop car adapter. If you go this route, make sure you get one that shows a voltage input range below 10V (and up to at least 16V) to indicate that it's really a DC-DC inverter. Otherwise, you can buy general purpose inverters from places like Jameco.com.

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#79043 - 16/03/2002 14:03 Re: Pls Help with noise in boxster [Re: Neo_to_Rio]
sendero
journeyman

Registered: 04/01/2002
Posts: 74
Loc: Seattle, WA
my current 'fix' is a 'Mobile Authority' isolator. It sorta works, but isn't acceptable long term.

Looks like I'll be heading over to the jameco.com site right now to find the inverter and I'll be going that route.

thanks for the advice!
_________________________
Rio Car 30gb
2000 Boxster S, <img src="/ubbthreads/images/graemlins/cool.gif" alt="" />

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#79044 - 16/03/2002 14:11 Re: Pls Help with noise in boxster [Re: sendero]
sendero
journeyman

Registered: 04/01/2002
Posts: 74
Loc: Seattle, WA
ok, time for me to admit I don't know that much about DC-DC invertors

There are 3, 15, and 25 watt DC-DC converters that have an input range of 9-18v and ouput of 12. Which wattage rating do I need to get?

I'd rather ask a stupid question than fry my empeg

-
_________________________
Rio Car 30gb
2000 Boxster S, <img src="/ubbthreads/images/graemlins/cool.gif" alt="" />

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#79045 - 16/03/2002 15:27 Re: Pls Help with noise in boxster [Re: sendero]
Neo_to_Rio
journeyman

Registered: 02/01/2002
Posts: 57
Loc: Silicon Valley
Sendero, have you given up on the chassis to chassis ground approach? Although it's a little more challenging to get the strong ground needed, it makes for a cleaner install.

If you go with the inverter, I'd recommend using a relay driven by the switched power output of the Becker to control power to the inverter. This will keep it from drawing current from the battery when the car is turned off.

Here's the circuit I used:



This circuit virtually floats the power and ground of the Empeg. The only solid electrical connection to the car is through the audio cable. So you actually WANT to keep the Empeg chassis electrically isolated from the car chassis.

The top relay contact ensures standby power is applied to the Empeg (to keep the clock ticking et al). The top diode blocks power from being forced into the wrong side of the inverter, and the bottom diode just makes sure that the orange voltage isn't higher than the yellow.

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#79046 - 16/03/2002 15:36 Re: Pls Help with noise in boxster [Re: sendero]
Neo_to_Rio
journeyman

Registered: 02/01/2002
Posts: 57
Loc: Silicon Valley
The peak power spec for the Empeg is ~9 Watts. So a 15 Watt unit should be fine.

Make sure you test things out in stages, making measurements before you connect to either the Becker or the Empeg. There are a lot of things that can go wrong.

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#79047 - 22/03/2002 17:18 Re: Pls Help with noise in boxster [Re: sendero]
ellweber
member

Registered: 14/01/2002
Posts: 156
Loc: Saratoga, CA, USA
Sorry I didn't see this sooner but here is the link to the inverter I used when I had a Neo 35. (Anyone looking for a used Neo )

http://www.jameco.com/cgi-bin/ncommerce3/ExecMacro/Jameco/searchResult.d2w/report?sort=BKW&search=sd-25a-12

This may be a little larger wattage wise than you need but it is physically small enough to fit behind the cubby/under the Empeg/on top of the Airbag controller in the Boxster.

This one is less expensive but I haven't seen one and don't know if the output voltage is adjustable (a handy attribute) as is true of the first one I referenced.

https://www.jameco.com/cgi-bin/ncommerce3/ProductDisplay?prmenbr=91&prrfnbr=4383&cgrfnbr=780&ctgys=503;528;780;

I ended up with a massive ground between the Becker and the Rio with good results. I don't really have a problem with the Becker other than the poor sensitivity of the radio, which I think is mostly due to the Boxster antenna. I won't be drilling any holes in the body for a conventional whip antenna!

It takes both units to cause this problem, The Becker has poor common mode rejection on the Aux inputs and the Empeg produces plenty of ground noise on the audio outputs. I have measured 3-4 mv RMS across the sled's ground wire and this noise current is happy to pass through the audio output shields right into the Becker.


Good luck,

Lynn

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