Line Ouput Converter vs High Level Input (adding amp/sub)

This is actually referring to my IS300, but I'm just trying to understand this whole thing in general.

Like the alltrac, it has a stock head unit (HU) with NO preamp outputs stock, which goes to a stock amp, then goes to stock speakers.

I want to add a subwoofer with an aftermarket amp to drive it, simple.

I have several options:

1) Splice in a line output converter (LOC) from the HU output wires, send RCA cables from the LOC to the aftermarket amp, then power the sub.

2) Splice speaker-level wires from the HU, run the speaker wires to the High Level input on my aftermarket amp, and then power the sub.

3) Same as #2, but splice from the rear speaker wire (post-amp) - I hear preamp is better b/c you don't risk losing anything in case there are HP/LP filters in place in the amp if you don't use the correct post-amp speaker wire.

So...which is better, using a LOC with RCA cables to aftermarket amp, or just tapping off the speaker-level wires and run speaker wires to the high level input on my aftermarket amp?

Another question...in general, what does the amp (factory or stock) do with the speaker-level signal? Does it convert it to a lower signal, then amplify the signal for the speakers? If so, is this why using preamp outputs (on an aftermarket HU of course, since this doesnt' apply to my situation, but i'm just curious) to a factory amp (using a metra harness)/aftermarket amp generally better, b/c it keeps things/the signal "simpler/cleaner" (with noise reduction/signal distortion reduced)?

Thanks guys...i'm adding a sub (i've had BNIB for years) and got a free amp from my friend. The IS300 I bought has all the cables needed ran to the trunk (but the factory HU was put back in I assume when he sold the car), so I believe he ran a sub/amp in the back along with an aftermarket HU since no existing LOC is hooked up to my factory HU.

Thanks for the help guys. Never been TOO big into audio on my car, but figured I'd start learning some of the "slightly more advanced than your elementary knowledge of car audio" right now.

Bryan

toayoztan":2np6s2n0 said:

This is actually referring to my IS300, but I'm just trying to understand this whole thing in general.

So...which is better, using a LOC with RCA cables to aftermarket amp, or just tapping off the speaker-level wires and run speaker wires to the high level input on my aftermarket amp?

Another question...in general, what does the amp (factory or stock) do with the speaker-level signal? Does it convert it to a lower signal, then amplify the signal for the speakers? If so, is this why using preamp outputs (on an aftermarket HU of course, since this doesnt' apply to my situation, but i'm just curious) to a factory amp (using a metra harness)/aftermarket amp generally better, b/c it keeps things/the signal "simpler/cleaner" (with noise reduction/signal distortion reduced)?

Thanks guys...i'm adding a sub (i've had BNIB for years) and got a free amp from my friend. The IS300 I bought has all the cables needed ran to the trunk (but the factory HU was put back in I assume when he sold the car), so I believe he ran a sub/amp in the back along with an aftermarket HU since no existing LOC is hooked up to my factory HU.

Bryan

Click to expand...

Giving a good answer is easier if you tell us what amplifier you want to use. If the sub amp has high level inputs for front and rear speaker level signals, that is going to be the best option. Reason is that it is better to run a high voltage signal to the back of the car. It will be less sensitive to radiated noise from the alternator and other devices in the Lexus. In most installs, you will have a better signal to noise ratio at the input to the sub amp with speaker level inputs. The amp will attenuate the speaker level signal to an appropriate voltage internally.

I can't speak to the rest of your questions because I don't know what the outputs are from your stock radio in terms of voltage level and whether the stock radio has any internal filters. If you do not have a factory subwoofer, I doubt there are any internal filters on the OEM radio outputs. I also don't know what the Metra harness adapter for your car is like and can't comment on that.

LOC should be avoided unless it is a very high quality one that uses active electronics. LOCs that use transformers (most cheap ones do) are very susceptible to radiated noise. A superior method is to use a high quality preamp to condition the speaker level outputs from the factory head unit. Audio Control makes two good ones that provide some useful tone controls and aux input for MP3 player or other source. One of their models has a subwoofer output with filter and level control. If you have room in your dash, these are nice ways to adapt a factory head unit to aftermarket amps. There are other more sophisticated models made by JBL and others that include digital processors for EQ and filtering if you really want to explore higher end options.

If you plan on adding a sub and amp to the stock unit then you will be ok with using a hilow converter at either the stock sub or rear speakers post amp there is no problem that's the easiest and less expensive route if you want a nice set up with full control over everything look into either using the r.e.q. made by mtx or the 3sixty.2or 3 wich will do just about everything even add a mids and high amp look into it