LOC vs Line Level Inputs on Amp

[JasonK94Z 10+ year member]

I will soon be installing an Alpine MRX-M50 Amp and a sub in my new Dodge Ram. I will retain the factory head unit. I'm curious to know if I will be better off using a LOC or just tapping into my speaker wires and running wire to the line level inputs on my amp. For some reason, the Alpine MRX-M50 has 4 line level inputs, but it is a monoblock. Is it ok to just just tap into the 2 rears?

If a LOC is necessary, could you please suggest a decent one.

Thanks!

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[fasfocus00 5,000+ posts]

it's the same thing either way.

 

[JasonK94Z 10+ year member]

it's the same thing either way.

Good to hear. I figure the less crap I have to use, the less chance for noise and other issues.

Still not sure why the 4 speaker level inputs on this amp though. I'll just use the 2 rears and be done with it.

 

[fasfocus00 5,000+ posts]

there's a chance you may still encounter noise as there are other factors that cause that. a lot of amplifier companies are putting line level in put on their amps to respond to the increasing use of car makers having head units that are integrated into the dash and console of the car as opposed to something that can just be replaced.

 

[Flex68 10+ year member]

Using a LOC would likely make ur amp much happier...nice clean signal at a higher V level

 

[JasonK94Z 10+ year member]

there's a chance you may still encounter noise as there are other factors that cause that. a lot of amplifier companies are putting line level in put on their amps to respond to the increasing use of car makers having head units that are integrated into the dash and console of the car as opposed to something that can just be replaced.

Is there anything I can do first off to avoide any chance of noise?

Just a thought that pops up in my head is shielded wire I have here at work everywhere. Worth the effort?

 

[fasfocus00 5,000+ posts]

little to nothing you can do other than doing the install and see what happens. i've used $50 triple shielded RCAs and got noise, also used $5 single shielded RCAs and got no noise. not saying that quality RCAs don't help, just saying that you can still get noise with quality RCAs. just take your time and don't cut corners. i am one of the slower installers but almost never have problems due to my install.

 

[JasonK94Z 10+ year member]

I found a plug and play LOC from PAC that will give me a set of RCA's. Better? Or still just use speaker level inputs on the amp?

So confused. Some say no LOC, some say use a LOC. I need to just pick one and roll with it I guess.

 

[vaiboy 10+ year member]

Using a LOC would likely make ur amp much happier...nice clean signal at a higher V level

Where do you get this stuff? A LOC drops the voltage of the speaker output from the head unit, then outputs the lower voltage signal through RCA cables to the amp. It will be more likely to introduce noise through the lower voltage RCAs than using the speaker level input on the amp. The OP should just use the speaker level inputs on the alpine, it has signal sensing too so there's no need to run a remote wire.

 

[Team Maxxsonics 10+ year member]

The LOC's in amplifiers are typically not very good because of the cost it adds to every amp and because they are rarely needed, they are the least expensive solution available.

You may want to consider the Maxxsonics MX-1 Add-A-Sub.

It is specifically designed for adding a sub amp to a factory head unit.

It taps into the rear factory speaker wires, auto-sums the L/R signal to mono, has a built signal enhancer and has a variable level output to the amp.

They are available at onlinecarstereo.com and sonicelectronix.com

 

[JoeK 10+ year member]

I prefer the LC2i myself. Factory decks block out the bass at a certain volume which this unit can correct and restore that lost bass. Hook up L and R and then power and ground and bam. It has a remote out so you can connect your amp to it and it will turn it on or off with the head unit

 

[Flex68 10+ year member]

Where do you get this stuff? A LOC drops the voltage of the speaker output from the head unit, then outputs the lower voltage signal through RCA cables to the amp. It will be more likely to introduce noise through the lower voltage RCAs than using the speaker level input on the amp. The OP should just use the speaker level inputs on the alpine, it has signal sensing too so there's no need to run a remote wire.

You better do some more reading.

Just one example (and a good one) is the LC6i, which offers individually adjustable outputs up to 9.5V.....no OEM HU is going to output anywhere close to that V. And at a THD of 0.01%.

Troll fail

 

[Flex68 10+ year member]

Where do you get this stuff? A LOC drops the voltage of the speaker output from the head unit, then outputs the lower voltage signal through RCA cables to the amp. It will be more likely to introduce noise through the lower voltage RCAs than using the speaker level input on the amp. The OP should just use the speaker level inputs on the alpine, it has signal sensing too so there's no need to run a remote wire.

You better do some more reading.

Just one example (and a good one) is the LC6i, which offers individually adjustable outputs up to 9.5V.....no OEM HU is going to output anywhere close to that V. And at a THD of 0.01%.

Troll fail

 

[maylar 10+ year member]

You better do some more reading.Just one example (and a good one) is the LC6i, which offers individually adjustable outputs up to 9.5V.....no OEM HU is going to output anywhere close to that V. And at a THD of 0.01%.

So what? A Class D monobloc sub amp doesn't give a rat's ass about any of that. The high level inputs on an amp are designed for the right levels to match the amp's input sensitivity. You won't improve that with an external LOC. You also get ground isolation by default and no chance of turn on/off thump that's possible with external devices. And as mentioned, you get remote sensing for free.

As for the circuitry being cheap, it only takes a few resistors and a couple of caps to impliment line inputs. The preamp is already there.

 

[Flex68 10+ year member]

One word: flexibility.

2V from HU vs/ up to 9.5V from the one example. Monoblock or multi-channel, doesn't matter, the higher input V should result in less noise amplification. Add to that all the additional features, a couple of which you mentioned.

To each their own, but if I were wanting to keep OEM HU and couldn't/wouldn't install a CleanSweep, the higher-end LOC's would be attractive to me just for the individually adjustable outputs, both voltage and gain.

But , then again , I was also looking at what could be accomplished for substage and front stage via a LOC... those factory door speakers would be sounding like a whole new system with an LC6i, or comparable unit