Adding Amps to Factory System without a LOC

[RKPsk8er 10+ year member]

I have an 06 bmw 325i and I want to add a 4 channel amp for mids/highs and a separate amp for my sub. I basically want to avoid using a LOC because the only speaker-level source comes from the factory amp that induces heavy equalization and limited range per channel. The factory radio uses twisted pair (balanced differential) low-level outputs to the factory amp and my question is how do I properly source those. I know it would be easier to just add an aftermarket HU but I would lose way too much function going that route.

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[sobe3yourself. 10+ year member]

use wires from factory sub?

 

[BnGRacing 10+ year member]

The factory radio uses twisted pair (balanced differential) low-level outputs to the factory amp and my question is how do I properly source those.

Solder an RCA end on it, plug it in your amp, be merry //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Even if it was a high level output like the older BMWs had, you can hack up a cheap set of RCA's and splice those into that line.

 

[RKPsk8er 10+ year member]

I wouldn't pick up a lot of interference/engine noise like this?

 

[audiobaun 5,000+ posts]

Most amps have a high level input for this reason, and generally come with the plugs/or? Not sure exactly what amps being used, but old school amp can be done this way,as I have done before

 

[winkychevelle 10+ year member]

ive god an tx req5 that can take th source after the amp and sum it for total frequency range 20-20k. gives u 3 sets of rca jacks front rear and sub. id be willing to send it your way for 50shipped

 

[infamous_e46 5,000+ posts]

splice into wires before amp

 

[maylar 10+ year member]

The factory radio uses twisted pair (balanced differential) low-level outputs to the factory amp and my question is how do I properly source those.

If it's truly low level differential and not speaker level then you can use use them directly. Just be sure that whatever amp you choose has differential inputs on its RCAs (most do nowadays) - you don't want to short the minus side HU line with a grounded RCA input.

 

[BnGRacing 10+ year member]

I wouldn't pick up a lot of interference/engine noise like this?

Yes it would...but your amp will filter it out. It's called 'common mode rejection ratio' and is why you can get away with hi level inputs, as well as poor RCAs, and not have noise issues. The hardest thing about splicing into the OEM signal wires is figuring out which is which so you're not out of phase. The easy way is to not really care about that until you're about done and you give things a listen. It's a lot easier to flip RCA jacks than beating your head trying to make sure you dotted your i's and crossed your t's.

 

[RKPsk8er 10+ year member]

Most amps have a high level input for this reason, and generally come with the plugs/or? Not sure exactly what amps being used, but old school amp can be done this way,as I have done before

I'm talking about using low level outputs between the factory radio and factory amp.

ive god an tx req5 that can take th source after the amp and sum it for total frequency range 20-20k. gives u 3 sets of rca jacks front rear and sub. id be willing to send it your way for 50shipped

The factory amp induces heavy equalization thats varies on volume which is the reason behind be avoiding the factory amp outputs.

splice into wires before amp

via soldered RCA ends?

If it's truly low level differential and not speaker level then you can use use them directly. Just be sure that whatever amp you choose has differential inputs on its RCAs (most do nowadays) - you don't want to short the minus side HU line with a grounded RCA input.

I haven't decided on an amp yet- considering the sundown sae-1000 or an AQ-1200.

 

[scott0482 10+ year member]

Have you figured this out?

I am pretty sure the Stock BMW Business CD player is amped. They use the exact same Headunit for all E46s. Most do not have the Harman Kardon amp.

I have a $4 LOC and a PPI PC2100 amp (1997 ish) that accepts "Balanced Differential Inputs". I will try both methods and note the differences, if any.

I am about to rip out all of my HK stuff in the next few days or weeks.. I will hopefully remember to come back here and follow up.

I have a 2002 330i with HK, just for reference.