Adding pre-amp outs to stock h/u 03 x5

[ClausVonWendel]

I just got an 03 x5 3.0 and am planning on adding an amp/subwoofer set-up.

If possible I would love to keep the "Business CD" stock head unit and i was wondering if anyone knew a good way of adding pre-amp outs/RCA jacks to the existing stereo, as i am trying to avoid an after market switch to keep the asthetic pleasure of the x5 dash

Thanks

Curtchfield sells this interface .... PAC OEM-2

[el_duderino]

With that CD I believe that your HU has preamp outs, just no RCA jacks.

You just need to get the wiring diagram for the audio system to verify the wires you need to grab.

The other thing you need to verify is that these wires change level with volume adjustment (something the DPS systems DON'T do).

You ca get a day rate at www.bmwtechinfo.com for $25 and look at the wiring diagrams for your car ath the official BMW info site.

You will have some work ahead of you to eliminate various sources of noise... but it builds character.

[ClausVonWendel]

Check out the link in my first post, has anyone seen/used one of those interfaces before, or if another way how have u done it?
thanks again

[el_duderino]

There are two types of interface:

One is to grab the output from the HU to the amp. With BMWs, the signal often has a DC component to it that needs to be removed - and I think some of them are balanced three-wire and not single-ended RCA-style two-wire. Soundgate has one that does this - it's the LOCPREB, I believe.

The other is to grab the output from the amp (either internal or external) to the speakers and lower the amplitude in order to be able to take that into an aftermarket amp. There are many that do this, but it's a problematic process (see my post about the X5 analysis). If you want to add the signals back together you need transformer islation usually, which means AudioLink or Soundgate LOCHVA or Navone L7.

But you first need to decide what kind of interface you want to, and can, do, before you can decide which LOC you need.

Hopefully next week I can get the 2006 3-series again and test that output for volume level, but my fear is that it is fixed like the 2005 X5. If it is fixed in level (and the volume changes happen in the amp, not the radio, like the X5), then you can do what the post describes for the X5, or you can buy a JL Clean Sweep and disable your steering wheel controls.

[dkl]

el duderino, your insight are much appreciated on this site. Just wished there's more audio enthusiasts like yourself who's willing to share their knowledge. I just got one question for you: What's your opinion in deciding whether to use RCAs or just speaker level feed if the amp provides the option for both? I would think the speaker level would be a better option for noise immunity since it's a stronger signal. What's your take on this?

[SuaveX5]

I think the RCA will be a better choice less distorsion and less things you have to do to manipulate the sound if you wanted to.
Speaker lever is already amplyfied and you will have to feed it into a high lever input source or get a high to low converter.

correct me if i`m wrong !

[dkl]

But if the Amp already accepts speaker level inputs, there's no need for an extra high-to-low converter (which will add to your distortion level)... why not just tap into the speakers and feed the amp for the sub directly. Besides, most class D amplifiers used for Subs are not very good in THD to begin with (I don't think you can degrade it much), so SNR would be the bigger factor here, don't you think?

[SuaveX5]

ok if the and you`r adding has speakers lever input them you can just use the speaker lever out put like you mention.

[el_duderino]

Tks for the kind words.

The LOC's inside an amp are usually not the same design as the LOC's you can buy from specialty companies like Soundgate. Since it's not often used, the amp manufacturer usually doesn't put a whole lot into the board for that function - usually a few resistors - best suited for low-power applications like the speaker wires that come off of the back fo a radio, when there's not an external OEM amp present..

Many external LOC's use transformers to isolate the outputs of the OEM amp from the inputs of the aftermarket amp. While the effects of transformers in this application can be debated from a sound quality perspective, when dealing with higher-power amplifier outputs, they are the best way to go.

Additionally, if you are doing what we did and summing multiple channels together to eliminate the OEM amp's internal crossover points occuring at frequencies we didn't want to have separate, you need transformer islolation in order to be able to "sum" these back together on the other side of your LOC output. The LOC in the amp can't accomodate this sort of application - but it's needed in many BMW systems (and others as well).

Often, the best use of the LOC inside an amp is to add a sub to an existing system - when engine noise can't be heard.

Now, SOME amps have such a wide input voltage variation (JL, for one, if you flip the switch) that you can run speaker wires straight in. THis is nice - IF the speaker wire is carrying a signal you want to amplify.