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      10-02-2012, 07:31 AM   #1
Alistair330
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How to connect Amp after Hi-Fi Coding???

Hi all,
Please can someone answer the follow.......

If I have my Professional HU coded to Hi-Fi (Base System, coded to Hi-Fi), how would I connect it to my Alpine F640 Amp? Do you use the HU speaker wires (as it has no RCA out) and if so, do I need to use a LOC to connect them to the Alpine Amp's RCA inputs? The Amp has speaker level inputs but they are high-level and I'm assuming after the Hi-Fi coding the HU speaker wires will be low level?

Although this seems like a simple question, I haven't been able to find the answer, even after hours of searching.

The only hint I found was to use the "Technic's harness", but as I have already installed all the wiring myself (as per the Alpine Upgrade) I would rather continue that way.

Any answers greatly appreciated!!
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      10-02-2012, 07:39 AM   #2
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Hi Alastair, all the wires should be in the kit? I didnt have to cut anything, just add the link cables to the tweeter which was all done with the prefitted clips.
If I remember the return connections to the amp came from the sub connections although it was a while ago?
Here a link to the official fitting instructions;
http://f20.1addicts.com/forums/attac...7&d=1336731547
Hope that helps in some way?
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      10-02-2012, 08:56 AM   #3
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Sorry,
I think I have confused you slightly.
I don't have the official 'Alpine Upgrade Kit' which is supplied by dealers etc...

I have an aftermarket 4 channel Alpine Amp (F640) which I have installed myself using the same logic/Instructions as supplied with the official Alpine Upgrade. For Example, I have made my own wiring loom but connected it at the same points as the Alpine upgrade kit.

What I want to know is; if you use an aftermarket Amp as I have done, how do you connect it to the HU after it has been coded to Hi-Fi??

I understand the Amp in the Alpine upgrade Kit has a switch on the bottom to set the Input from Low level to high level, depending on the Headunit outputs but an aftermaret amp such as mine doesnt have this feature.
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      10-02-2012, 08:57 AM   #4
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P.s. Thanks for the reply Chedixon!!
Good to see someone else local !! (I work in Derby)
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      10-04-2012, 05:41 PM   #5
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Bump for this thread - I want to know the same thing.

Once the HU is recoded to HiFi the outputs are low level 5V outputs. Do I then need to make them into RCAs to connect to the amp, and if so, will any old RCA adaptor work?
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      10-04-2012, 06:02 PM   #6
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If your amp can take differential input, then you don't need anything.

Here is the list of amps which can accept balanced differential input.
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      10-04-2012, 07:46 PM   #7
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OK. I'm waiting for a spec sheet for the amp but let's assume it doesn't accept a balanced input. I can't use the speaker level connections on the amp because it's now a low-level signal, so I need to somehow make the bare wire ends into RCA plugs.

Will something as simple as the Autoleads PC1-601 work? Does the ground lead make them unbalanced?
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      10-06-2012, 07:12 AM   #8
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Quote:
Originally Posted by parapaul
Bump for this thread - I want to know the same thing.

Once the HU is recoded to HiFi the outputs are low level 5V outputs. Do I then need to make them into RCAs to connect to the amp, and if so, will any old RCA adaptor work?
As Makkan says you need to make sure your amp takes balanced differential inputs. Then just add RCA connectors to your speaker out from your HU and connect to the RCA in of the amp.
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      10-06-2012, 08:17 AM   #9
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Cross link to a thread I just started: http://www.e90post.com/forums/showthread.php?t=754920

The list of amps that accept balanced inputs is pretty small. I'm interested in a way (or ways) to connect the balanced signal from the HiFi HU to unbalanced inputs of any old amplifier.
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      03-25-2016, 04:44 PM   #10
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Sorry to dig out an old thread, but I have the same question as the OP but struggling to get an answer.

I am looking to add an aftermarket amp but wondering what is the best way to connect it to the HU.

Option 1 - Get an amp with high/speaker level inputs and tap into the original wiring. No HIFI coding required.

Option 2 - Recode HU to Hifi. Add RCA's to the factory wiring and connect to amp via these. Will this actually work, if so on which amp?

Thanks
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      03-26-2016, 05:32 PM   #11
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The term "balanced differential" isnt really correct.

The head unit uses a bridge tied load configuration.

This means for each output channel, there are two amplifier chips. One drives the positive wire like normal, the other drives the negative wire with an inverted signal. They do this becuase it means you can use a single 12v PSU and get a decent output power.

This poses an issue for some amplifiers, as many amps assume RCA ground and Chassis ground are the same thing, and connect them together internally. If you connect the output from the head unit to such an amp, you short out the amplifier driving the negative leg, and the amp shuts down.

Many amps however dont tie the RCA ground to chassis ground. Any of these will work fine. Just check with a multimeter between the RCA shells, and make sure they're not connected together, and also check between RCA ground and the ground power terminal on the amp. If they are all high resistance, you're good to go.

However even if your amp does connect the RCA's together, all you need to do is only connect the + to the RCA, and connect the shell of the RCA to chassis ground.. Each amplifier in the head unit is already referenced to chassis ground, so it should all work fine. You might get ground loop issues, but worth a try if its an amp you've already got etc.
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