High (Speaker) v. Low level inputs on Amp

Custom Jim

I would really suggest using an LOC behind the radio and using an external crossover/line driver(like AudioControl's 24XS) in the trunk if you're worried about the voltage of your preamp outputs. This would give you superior sound over the high level inputs on the amp and more control over the signal also. You could also use this to improve the sound when you buy an aftermarket head-unit.

If you were going to run rca cables to the factory head-unit why not just use them with an external LOC behind the radio anyway. If he buys another amp he shouldn't have to adjust the LOC either. They usually output around 4 volts, all he would need to adjust is his gain on his new amplifier(it isn't like he is going to have his gain all the way up just because he bought a new amp).

If I had a radio that did not have pre-amp outputs and wanted to wire it to an amplifier that had RCA and line level inputs I would wire it up using the high level inputs and allow the internal LOC inside the amp to do it's thing. If it works and performs like it should then were done. I have no need to add or spend any more money on external LOC's, RCA cables, or processors from other companies.

If later I change just my amplifier to one that only has RCA inputs then I would place the external LOC back by the amplifier and not have the added expense of long RCA cables going from the front to the back of the car and by doing it this way I'm not having to pull the radio back out again and another thing is if it's an adjustable LOC those controls are easily adjusted should any other amp be used later. With long RCA cables being run here I would have a greater chance of noise being induced into the cabling vs the shorter ones from the LOC to the amp with the LOC by the amp and not up front.

If even later I then changed the radio to one that has RCA output's THEN I would take out the LOC and run the RCA cables from the radio to the amp.

If the radio did not have enough signal coming out of it then I would put the line driver up front behind the radio so the low level cabling is kept as short as possible.  

I just think RichmondR needs to see how it works by hooking up his radio to his 4 channel amp the easiest way possible with the least amount of parts and without having to use external LOC, front to rear RCA cables or anything else. If it works and performs without these things, great. Time for a beer.

RicmondR, Here is my suggestions. Try having it wired with the speaker wires off of the radio to the high level inputs of the amplifier. If it works, your done. If for some reason they find out the radio has too much signal output for the amplifier's input, then have them install a LOC in the area that the amp is located. If they find out the radio does not have enough signal out of it, then have a line driver installed behind the radio. You just want the least amount or length of small signal between the radio and the amplifier. 

If you do replace your factory radio get one with a higher output pre-amp voltage and then run RCA's directly to the amp you have.

If later I change just my amplifier to one that only has RCA inputs then I would place the external LOC back by the amplifier and not have the added expense of long RCA cables going from the front to the back of the car and by doing it this way I'm not having to pull the radio back out again and another thing is if it's an adjustable LOC those controls are easily adjusted should any other amp be used later. With long RCA cables being run here I would have a greater chance of noise being induced into the cabling vs the shorter ones from the LOC to the amp with the LOC by the amp and not up front.

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If all you are trying to do is save money on rca cables by putting your LOC in back you arn't going to save much. For instance Streetwires Zero Noise 2 6.5' cable is $17 compared to the same type of cable that is $22 and 16.4' long. You also should not have noise problems as long as you dont route your rca cable right next to your power cable or with the brake light cable. Finally, YOU should not have to adjust your LOC every time you buy a new amp. Besides if you use rca cables and an LOC you won't have to worry about the amp's internal LOC not producing satisfactory sound. If he was running subs I would use the internal LOC on the amp because you can't really hear a difference with the lows, but he is running some high quality speakers so why not just go with the best sounding option, the LOC, which is usually your best way to go.