How should I wire a HU with 2 pre-outs?

I think I am going to buy a Pioneer AppRadio 3, but noticed it only has 2 RCA pre-outs at 2V. The higher end units have 3 outputs at 4V. I am not sure what effect it'll have for me having 2V vs. 4V. One of the RCA outputs you can set to be subwoofer output, or you can have it as rear. I was wondering how could I have an amplifier for 4 channels + one for the sub and only have the 2 RCA's?

If I went with a JL amplifier such as their XD700/5, took the one RCA that is for front, put a "Y" splitter on it, plugged them in to channels 1,2,3,4, then used the other set of RCA's and set it to sub; would that be the advised approach? I am also thinking of buying the JL Stealthbox for the 2012+ Tacoma, replacing my front and rear speakers. If the headunit had 3 sets of RCA's this could be easier.

I don't know if losing the "fader" control is a huge deal. I would still have "balance" (left/right), but not fader for front to rear. Is there a way to control that on the amplifier somehow so that while it cant be controlled on the HU, I could get it to the right spot and then set-it and forget-it?

AppRadio3


JL XD700/5
http://www.jlaudio.com/xd700-5-car-audio-xd-amplifiers-98264

 

A higher pre-out voltage allows you to set your amp gains lower to achieve a desired sound level. Lower amp gain equates to lower noise floor (i.e. less electronic "noise" being amplified). However, people have achieved great sound quality and loud levels using only 2V pre-outs. Noise is mainly a function of how clean your HU and amplifier are. Pioneer and JL Audio are known for producing good quality electronics. If you love the features of the HU and the JL is within your budget, then go for it.

The XD700 allows you to use only four RCA inputs for all five channels. The sub will be a sum of all your inputs. Unfortunately, you won't be able to fade the sub level from the HU with this configuration. See page 6 of the manual: http://mediacdn.jlaudio.com/media/mfg/9013/media_document/live_1/XD700_5_MAN.pdf?1346971741

In order to control sub level from the HU you will need Y splitters like you described. You can use the amp's gains to act as the front/rear fader control. If you want control of your sub level for various types of music, then this is the approach I'd take.

 

I found those sections, thank you.
"Input connections are via up to three pairs of
traditional RCA-type jacks."

"If you wish to send six discrete channels into
the XD700/5, simply use all six inputs and set the
“Input Mode” switch in the “6 Ch.” position. The
amplifier will automatically combine the Sub Ch.
input signals to mono."

What I don't understand is the control of fading you say from the HU vs the amp in the various configs.
This sub does have that "Remote Level Control" option. That seems pretty nice so In my mind I would use the headunit standard volume to control volume to the 4 various channels (derived from the one set of RCA's with a "Y" splitter going to channels 1/2/3/4 in the amp) and then the other set of RCA's for the sub, then could I use the remote level control to simply control the sub?

 

It looks like you're on the right track. Use one set of RCA outputs run through two Y splitters that input into channels 1 thru 4, then use the other set of RCA outputs as input to channels 5 and 6. The second set of RCA outputs can be set to subwoofer output from the HU and you can then use the HU to adjust crossover frequency, phase, and level. See page 61 of the manual http://www.pioneerelectronics.com/StaticFiles/Manuals/Car/SPH-DA210_OperationManual051713.pdf#page59

You will then use the amps gains to act as your "fader". Channel 1 and 2 of the amp will have its own gain knob for your fronts, and channels 3 and 4 will have its own gain knob for your rears. You will use the two gain knobs to set levels for fronts and rears, then use the HU to set the level for your sub.

 

The sub will have its own gain, too. In reality, you will set all gains to achieve a strong signal, then fine tune your "fader" using the gain knob. Always turn down the gain of whichever set you want quieter (fronts or rears) rather than turning gain up to be louder.

Clear as mud?

 

It actually seems quite clear. Now I just need to buy stuff. I am not in any rush, but it's on the agenda for this year. Thank you, all.

 

Any option you pick is going to take HU control away from one of the channels (fr, back, sub). You need to pick which channel you think you'll want to mess with least from the HU and use your Y to include that channel.

If you think the rear channel would be best, as discussed, you can use the amp gains to control that level. If you think it's the sub, you can run a Y off of the front RCAs, then feed that into the front and sub channel.

Again, you just need to figure out which one is the least painful for you and go with it. ...or, pick another HU with 3 pre-outs.

 

Or you could opt for the Alpine ICS-X7HD which offers 6 channel outputs.

 

I bought the HD-RLC remote level control for my JL Audio amp and I'm very happy I did. Many HUs have subwoofer volume control burried in the menus somewhere so it is possible to not use the HD-RLC. But life is much easier with it.