Question about gain and tuning a Lc7i and 5 channel Amp

[bando81]

I have an Lc7i running the front speakers on the main channel, rear on the 2nd channel, and then no speaker inputs for the 3rd channel but I do have a sub running from the channel 3 output. This all ends up at a kenwood xr901-5 powering 4 coaxial speakers and a 12” sub.

I know for a fact the installers didn’t take their time tuning the system. It doesn’t sound bad but I feel it could sound better. The gain settings on the LOC are all in their default setting. The gain on the amp is at about halfway for the front, rear, and sub settings There’s also a bass boost on the amp turned up to 3db.

From what I’ve read and watched, this LOC can and should be tuned so that the amp doesn’t have to have the gain turned up as high.

How would I go about matching the gain on the LC7i and my amp?

 

[JasoninDLH]

Following this thread as I’m installing an LC2i for a sub and would like tuning advice as well.

My LC2i has a Preamp output of 9.5 volts, so you’re definitely right to turn the gain down (I’m assuming your 7i has the same volts).

 

[1aespinoza]

I have an Lc7i running the front speakers on the main channel, rear on the 2nd channel, and then no speaker inputs for the 3rd channel but I do have a sub running from the channel 3 output. This all ends up at a kenwood xr901-5 powering 4 coaxial speakers and a 12” sub.

I know for a fact the installers didn’t take their time tuning the system. It doesn’t sound bad but I feel it could sound better. The gain settings on the LOC are all in their default setting. The gain on the amp is at about halfway for the front, rear, and sub settings There’s also a bass boost on the amp turned up to 3db.

From what I’ve read and watched, this LOC can and should be tuned so that the amp doesn’t have to have the gain turned up as high.

How would I go about matching the gain on the LC7i and my amp?

 

[bando81]

I watched this. I don’t know to use my multimeter the way he does. He rigged RCA cables to his multimeter probes to measure the output from the LOC. I can’t seem to figure out how to do that without the little contraption he made. If you could spell out how to measure the voltage coming out of the LOC for me I’d really appreciate I’m stumped on this one (without buying more proper equipment)

 

[bando81]

Following this thread as I’m installing an LC2i for a sub and would like tuning advice as well.

My LC2i has a Preamp output of 9.5 volts, so you’re definitely right to turn the gain down (I’m assuming your 7i has the same volts).

The LC7i has 8.5 volts output and my amp has 5v input sensitivity. So I assume that means that if the LC7i is turned to the max on the output controls, it’s going to be putting out too much voltage that my amp can handle, correct? I feel like the goal is to match the voltage output from the LOC to the max voltage input sensitivity of the amp. Am I wrong in this thinking? And if the voltage from the LOC matches the input sensitivity of the amp, would you even need to make adjustments of the amp gain?

 

[1aespinoza]

So I assume that means that if the LC7i is turned to the max on the output controls, it’s going to be putting out too much voltage that my amp can handle, correct?

Correct. From the amp, disconnect the RCAs that come from the LOC. The picture below points to where you will connect your multimeter test leads. Be cautious that positive and negative do not touch each other. The guy in the video made that pigtail to avoid this issue. Set multimeter to A/C volts. After downloading that 1000 Hz. test tone, play it on your radio at ~75% volume. Now sweep the gain on the LOC until you read the 5 volts that your amp can handle. Boom, Jalapeno solutions. Before reconnecting the RCAs to the amp, turn down the gain at the amp. Turn it up judiciously after that with the radio at ~75% volume.

 

[bando81]

Correct. From the amp, disconnect the RCAs that come from the LOC. The picture below points to where you will connect your multimeter test leads. Be cautious that positive and negative do not touch each other. The guy in the video made that pigtail to avoid this issue. Set multimeter to A/C volts. After downloading that 1000 Hz. test tone, play it on your radio at ~75% volume. Now sweep the gain on the LOC until you read the 5 volts that your amp can handle. Boom, Jalapeno solutions. Before reconnecting the RCAs to the amp, turn down the gain at the amp. Turn it up judiciously after that with the radio at ~75% volume. View attachment 47064

Perfect. Thank you. Just curious. What happens if positive and negative touch

 

[Jimi77]

Use a sine wave to set the gains, somewhere between 1-3.5khz. It will start to distort and change pitch when you start to clip. Turn the outputs on the LC7 to ~1/2 way, turn the gains on the amp all the way down. Turn the output up on the LC7 until you hear the change in pitch and then dial the output back a tiny bit.

 

[bando81]

Use a sine wave to set the gains, somewhere between 1-3.5khz. It will start to distort and change pitch when you start to clip. Turn the outputs on the LC7 to ~1/2 way, turn the gains on the amp all the way down. Turn the output up on the LC7 until you hear the change in pitch and then dial the output back a tiny bit.

I was starting to do this but the 1000hz tone was getting really loud

 

[1aespinoza]

Perfect. Thank you. Just curious. What happens if positive and negative touch

It could damage the LOC outputs.

 

[bando81]

It could damage the LOC outputs.

Would I easily be able to if they’re damaged

 

[1aespinoza]

Would I easily be able to if they’re damaged

It is just an assumption on my part. On the old Pioneer radios, if they touched, you would get a high pitched whine that had no easy fix. You had to open the radio and bypass a "pico fuse".

 

[Jimi77]

It is just an assumption on my part. On the old Pioneer radios, if they touched, you would get a high pitched whine that had no easy fix. You had to open the radio and bypass a "pico fuse".

It was an easy fix, you grounded the RCA jackets to the HU chassis.

 

[Jimi77]

I was starting to do this but the 1000hz tone was getting really loud

It should get loud, you're trying to find the maximum unclipped output of the system. Otherwise you have to do the AC voltage method with a multimeter and preferably a 2-4 ohm dummy load. I've set by ear forever.

 

[Jimi77]

Would I easily be able to if they’re damaged

Yes it would be easy to blow the outputs. Exercise caution if you're going the multimeter route.