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Martin, Engineer
Category: Car Electronics
Satisfied Customers: 4930
Experience:  16 years, include works in aluminium plant, industrial machinery, military weapons, programming
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Customer Question

SPECIALIZED QUESTION - AUDIO / ELECTRONICS EXPERT ONLY!! I am an Electronic Technician but do not have knowledge on the Land Rover Range Rover HSE, 2005. I need an external audio input. The car does not have one. The system is some sort of loop with fiber optics between the cd player, amp, tuner etc. I do not want to mess with the fiber optics or anything else that might disable the system, BUT, since the amplifier obviously is digital in, there has got to be a d/a converter somewhere in the amplifier. I was thinking that a very simple solution would be to put a relay or appropriate switch at the output of the d/a converter circuit and bingo! I would have my input and the system would never know it. With me so far?
If whoever answers this knows of any solid reason why this would not work, let me know.
I first need a schematic and/or service manual for the audio system, especially the amplifier. Note, if a true expert answers this and guides me / works with me on this there WILL be a substantial TIP at the end of the job.
Submitted: 1 year ago.
Category: Car Electronics
Expert:  Russell H. replied 1 year ago.

Hi, thank you for contacting My name is Russell. I will do what I can to provide the right answer to your question.

Be careful with what you are doing.

Generally speaking, applying a circuit to an output, as if it were an input, is likely to

A. not work at all


B. do some damage to the system through that output port, too.

A relay or a switch at an output, would not do any good. Esp. not at the output of a d/a converter circuit.

Customer: replied 1 year ago.

I evidently did not make myself clear.

Inside the amp there is a point that is the output from the d/a converter that goes to the input of the analog amp. What I propose to do is to have a relay switch what the analog amp is getting as far as a signal. Relay contacts (dpdt) are open so it is operating just like factory. Relay contacts closed would route my cell audio output to the input of the analog amp.

Please supply me with the service manual or at least the schematic for the sound system. I will then be more detailed in what I am hoping to do and it will probably make more sense to you.

Expert:  Russell H. replied 1 year ago.

So in other words, you'd disconnect the output from the d/a and connect an alternate connection to the input of the analog amplifier?

That could work, yes. Make sure you match impedances, roughly, from the cell audio out, to the analog amp input, and it should be workable.

(If this answers your question, please rate my answer.)

(I don't know the maker and model # ***** the sound system in that model of Land Rover, but if you either determine that for me, or let me Opt Out in favor of another Expert who does know, that would do, I think.)

Customer: replied 1 year ago.

I will go to the vehicle now and see if I can find the info for us.

Expert:  Russell H. replied 1 year ago.


Customer: replied 1 year ago.

Hi Russell, I am back from the Sahara where the vehicle was parked. (haha) Here is the label from the amplifier. Len

Expert:  Russell H. replied 1 year ago.

Obviously a

Harman Kardon Logic 7 Surround Sound system.

Customer: replied 1 year ago.

I am confused here. I need a good solid answer to my question. OBVIOUSLY it is a HK Logic 7 system. However, that information does me NO good. I need a SCHEMATIC AND PCB LAYOUT so I can perform the work.

Why would you say "Obviously a Harman Kardon Logic 7 Surround Sound system." ?? That is what the photo shows. You didn't have to tell me that. I am not vision impaired. If you wish to help me I am more than willing to award 5 stars. If your intent is to be a smartass then opt out. This is not a game to me. I pay for this service. If I want humor I an buy a comic book. And by the way, I have been an Electronic Technician and an instructor in the electronic field for FORTY FIVE YEARS. This service is one I pay for simply to save research time.

Expert:  Russell H. replied 1 year ago.

I have Opted Out, though I had no intention to offend in the least, I assure you.

I simply have no more information, and not information of the type you require, so it is right to Opt Out under the circumstances. I hope that another Expert here will have the information you need.

Expert:  Martin replied 1 year ago.

Hi. I don't have either service manual for that one but one easy way would be to use an cheap FM modulator. There is short distance privacy issue with those that said. As for doing a mod to have an input hard wired, i indeed would do a bypass but that can be tricky as it often require to cut a trace and lift a surface mount pin to an amplification chip. Analog audio signal can be easilly probed that said, so a reverse engineering starting from the speakers and going back is not impossible (you have stereo channels to account for also).