Well I got an older Nakamichi where the power amp part comes off the back of the radio.
Then I got a harness so I can remote it.
... Effectively making it into a little 4ch amp.

The idea was exactly the opposite of your... similar - just opposite.
Namely use the big amps for moving. And then when parked, and it is quiet, to use the 40w/ch remote to power bookshelf speakers.
And the usual switches to the remote wires, so that one or the other, or both... can be powered or not powered.

I'm your case I don't think that HU can allow for the RCAs to send out and NOT power the 6x9s...

Maybe the big amps, and their separate speakers, can just be powered off a separate thing like an iPhone or iPad?
You cannot really power the speakers off of two amps without having some switch to select between the two amps.

 

ThankX Holmz for sharing.

I see in the pioneer amp manual it has connections for either rca preamp input Or for stereos without preamp, you can connect the amped head unit’s wires to the amp.
Maybe if I connect the head unit amped wires to the amp and not turn the amp on will allow the signal to go to the speakers as if the amp wasn’t there. Till I turn it in as desired... the manual doesn’t say hmm

Well this $16 home audio switch is intriguing that does 4 speakers to either source:
Pro-Wire IW-101 Source/Speaker Switch, White

 

That will not work, the amp does not have a pass-through feature. If the high level wires are connected to the amp you will not get any sound until the amp is on and powering the speakers.

The terminal board is also a bad idea. The head unit is probably only stable at, or just below 4 ohms. If you start adding more speakers to the circuit you will change the impedance, either you'll lower the impedance, and the head unit will fry, or if you wire in series you'll increase the impedance and drastically reduce the amount of power the head unit puts out.

Personally, I don't think your plan makes any sense at all. Just run the audio signal to the amp, and let it do the work. The amp is Class D, so it will be very efficient, and it won't draw a ton of current from the battery. The power consumption will depend on the output (SPL) you are listening at, so running off the head unit isn't necessarily going to reduce the current draw by much. I don't know the efficiency of the head unit amp, but a good Class D is around 80% efficient. There are too many things that could go wrong with your plan, and very little, if any benefit to it.

 

I'm with gijoe - ditch that internal amp, keep things simple, and never look back. If you really want to listen to stuff quiet all night without worrying about the battery, get a little bluetooth speaker or something for $20 on amazon. Just my $.02

 

Wow ThankX guys for the experience and advice!
That rings true, so I think I will follow your advice and stop thinking

This is my first amp install in many many years.
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Do you know, can I mount the class D amp behind the Plastic wall paneling in the van or does it need more air flow?

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Also what do you think of the switch idea for allowing powering the head unit’s on power from the auxiliary battery when desired without having to put the key in the ignition or accessory position so no one can steal my van while I’m parked with music playing?

The switch will need to be the type that allows the ignition acc power from the main battery to pass through as normal to the head unit but then if this switch is turned on, that connection to the ignition is opened and replaced with a connection to the auxiliary battery.
It seems a great set up for me although I suppose it would be even better if it had a reset back to normal if the ignition is turned on again feature to it so you don’t forget and leave it on.
Is this the set up others use for this desired effect?

 

You can do anything with a switch that an ignition switch does.
So you are going to leave the van playing and suring? Or how is it on but you are away?

For an RV one sometimes has a battery isolator, so that if (when) you forget, then the starting battery is still good.

 

Ok
Yes well it’s an extended van and if I’m at the drive in or camping etc with a group, doors open, music playing.
So I want to be able to turn the engine off and take the key out of the ignition and pocket it so I don’t have to worry about some stranger jumping in and driving off when my back is turned or I’m taking a leak etc.
it seems a surprising number of vehicles are stolen and they say one of the main ways a car is stolen is if you leave the keys in it.
My van has a factory auxiliary battery with the tow package.
The auxiliary battery is isolated, until the engine is running then a relay under the battery tray connects the auxiliary battery to the charging system.
So with the switch I plan on installing, I just flip it and the head unit gets powered by the auxiliary battery and amp come on powered by the auxiliary battery.
I’ll have the amp and head unit always powered to the auxiliary battery. But the head unit on power signal will come either from the ignition switch main battery or if I flip the switch, the auxiliary battery.
It’s the best set up I can think of.
This way also the main battery will never get too drained for when needed to start the van.

 

I would likely try to find a 3 pole is it, switch. That will switch a line between two other lines. Make one the radio wire and the other an always hot wire to run it when key off. Try to find a lighted switch like for driving lights, then you know its on when you get in, the led will not take much power at all. Far as killing your battery the HU will not likely but the amp can, so running it off another battery is good idea. You can put a HD relay to another battery so it closes when running (key on) and charges but opens when you turn van off. Fuse it, you could get an inrush current if you run it dead and then start it up, or use an isolator. Find a key on power that is off while starting many are. I would not bother with the HU amp I would disable it if possible, my 880 can do that. Some use it for tweeters but not really worth it. The class D amp should be as efficient or better, but will take more power at higher volumes. Or you could run some separate speakers with it and have a switch to disable the amp turn on if you really want to, but not sure why you would bother. Try to use larger speakers, as in size, that will get you some free volume if you have the room. Long ago I did boats we used 6x9, 7x10, even 8x12 would put out more sound on same amp. They really work well for open spaces.

 

Ok thank you for the input. It's also nice to know that the amp on low volume won't drain the battery any worse than the head unit amp would!

 

I think you then just keep the ign switch to the radio as normal...
And on that same same wire going into the raido/HU you have the switched wire from the switch.
Then the radio supplies the remote signal to the amps... and they are on the extra/aux battery.

That should work a treat.

I doubt you would need a diode between the ignition and the HU, but that would also isolate the two batteries trying to connect to each other... if that was the case then both the ign, and the switch... would have a diode pointing towards the HU.

That would be the bulletproof solution... and a bit safer in the event that one battery or the other was at a different voltage.

 

Ok thanks for the input!