Hercules

Quick question for you guys...

I was thinking about how I 'tap' my connections... as it stands I need 8 connections (Right Front/Rear, Left Front/Rear both positives and negatives) to fire up the amplifier. I was going to use the head unit and tap right off of that, however there are wires that run in the trunk -- but just the Rears. Can I tap those twice? Like, I'd wrap the high level inputs for Right Front and Right Rear onto the Right Rear output from the head unit, and then wrap both Left Front/Rear onto the Left Rear to get my inputs.

Any disadvantage to this? Will it work as I need? It will make my wiring a bit simpler but I'm trying to figure out first if I should do it

Thanks!

rx8guy86

I would not recommend at all using the high level inputs. You will have a very high chance of damaging you head unit. If I were you, I would use a LOC (I have a AudioControl LC8 that I would sell ) to tap in before the amp in the trunk. The LOC will convert the signal into RCA outputs.

David

Hercules

My amplifier accepts differential inputs for speaker level -- I asked around, and there really isn't any problem with Bose installs and this amplifier.

I have an LOC as well, but it accomplishes the same thing as the LOC, so there really seems to be no need for the LOC when my amp does exactly the same job.

forbidden

I guess the only way for you to really know this is to experience the difference between what a LOC and a interface really does. I completely understand your desire to keep things cheap, I hope you completely understand the other side of the issue that will give far better results in your system. The LC8 would be another ideal interface for this application.

Differential outputs have no bearing at all on this. The real difference in the Bose system is the lack of preout voltage on the rear channels. Your built in LOC in the amp can then only do so much.

My recommendation to use that 6XS was based on actual use of both LOC's, LC6 and the 6XS all in a RX8 for one of my customers. It was the only way to help the customer understand the difference between how to take his system from being OK at best, to one that performed the way he wanted it to.

Consider doing this as a upgrade in the future, you will not regret it.

rx8guy86

Yup, very well put

Hercules

That makes reasonable sense. I can definitely think of that as an 'upgrade' later on... right now, I want to do things that keep me in a budget.

jstkilntim

Yes, you can connect it this way and any of the numerous ways that have ran through your head and described in your other posts. Again, the front & rear inputs are in the rear of the car. Use them.

Since you have asked similar questions in numerous posts, here it is plain & simple........An amplifier can only amplify the signal it receives. Period. If you send it a low voltage signal (as in the bose pre-amp), you will have to turn the gain way up to get the volume you will probably want and you will more than likely have a noisy system. Will this work? Yes. Is it acceptable to you? Sounds like it. Is it the best route to go. Nope.

A quality line driver is designed to boost a low voltage signal (with minimum noise increase) so your amp has a strong, quality signal to amplify.

You said that you already have your LOC, and since you will splice it in the same place anyway, try it both ways and see.

Hercules

I have an LOC -- just not the $150 one. I have the David Navone one that if it works as I need, then I'll just leave it that way

I guess I'll have to see, eh?

Hercules

By the way....

https://www.rx8club.com/showthread.p...98#post1101598

That post says that there's plenty of signal before the amplifier with which to tap into. I will try it without the LOC first, and then with... and see what happens.

jstkilntim

There is plenty of signal, but a higher signal voltage is usually better. Look at most competition systems and you will usually find line drivers. Many times you will find line drivers before a processor and then again directly before the amp.

Don't forget to let us know.

Astral

Try it without the LOC. I was using the David Navone LOC and I just ditched it. I would recommend against it. It was killing my bass and the total output voltage was just somewhat lower than without using the LOC.

Like of the linked posts said, the stock HU outputs are 10V peak-to-peak at almost-max volume. That's probably approximately 4-5V RMS. I am connecting the front channels to an AudioControl DQT EQ, which is rated for about a maximum of 7.5V RMS input voltage, so I am well within spec here.

Because without the LOC, the input signal is now louder, I was able to turn the gains down a little and that reduced the noise a bit as well.

Disclaimer: I have the stock, non-Bose HU.

Hercules

I believe that's the route I will be taking... without the LOC. I have read enough between this site and the Mazda6 site (they have the same HU and Bose configuration) to feel that it will work.

I have the David Navone LOC though, so I will give it a shot on the right channels, while I use the left with high level inputs. I can fade side to side and see what sounds better. Makes an easy choice for me.

forbidden

Astral, the sole reason that your DQT is working better than the LOC is simple. It is advanced LOC like the 6XS that can take any kind of input signal. It also has a line driver built into it, same as the 6XS does, this is why you could turn your gains on the amps down. So, you have better results than the basic LOC which you ditched because you have a far superior unit acting as the interface.

Astral

forbidden, I adjusted the output signal to hit the +5V peak at 3/4 volume on my DQT (as per the gains setting procedure). Technically that's lower output voltage that what the head unit is feeding to the DQT. So am I really driving the line when I'm actually decreasing the output voltage? And if I am using the line driver, it's only over a very short run right into the amp (as opposed to a situation where the line driver is inserted right at the HU outputs and sends the louder signal all the way to the back of the car).

BTW I am not really contesting anything, I just want to understand exactly what's going on in the DQT that makes it a superior unit.

The alternator whine I had with the David Navone LOC is not there anymore with the DQT (I checked that it wasn't the amp by using a muting plug). I wonder why that is, as both the DQT and the David Navone LOC are supposed to be "isolating" (at least my DQT was set to "isolate" ground isolation setting). The DQT was set to "balanced' input, where it added up the differential signal--maybe that's something that the David Navone LOC wasn't doing? (find it hard to believe)

Astral

let me know what you find

jstkilntim

The reason for your success makes sense to me.

A standard LOC is designed to take high level signals and turn them into low level signals. (Example: non bose HU) A line driver is designed to boost the voltage on low level signals. (Example: bose pre amp signal) So, unless you actually measured the voltage berfore, you probably actually lowered your signal by using the LOC.

As forbidden posted, AudioControl (and a couple other brands) offer equipment that is both a LOC and line driver. You get the best of both worlds w/ one quality unit. You also took one component out of the system that is almost always great for reducing noise.