Thanks Jeff.
In response to your PM(s) about installing for your 6 amplifiers and using a separate switch to power the system on/off my system (ie, bypassing the keyed ignition switch)...
Firstly, apologies for posting publicly, but since this is a typical question and useful for others, and IMO it should be "public" based on the intent of this forum, and IMO there is nothing embarrassing nor personal nor private in your PM (noting the politeness of your request - with appreciation!).
Secondly, I can't post diagrams unless they are copies or simple mods to existing pics. (My fault - I still haven't found an "up to speed" replacement for my old Windows2k MS Draw since I upgraded to this Win7 beast.)
However, there should be no need for diagrams. This should be quite simple - merely the use of "standard" fused switch and relay circuits which can be gleaned from other threads if not the Reference links at the top of the12volt pages (above).
But anyhow, before that, some general blurb & issues...
Now, I'll assume your amps (their power terminals) are all wired direct to the battery - thru fuses and cabling as per my previous reply (and a plethora of other the12volt threads) and noting that GND may be to solid chassis/body point(s) rather than - or in addition to - GND cable(s) to the battery or engine etc.
[ Whether to ground "in theory" to the engine (ie, hence alternator) or battery depends what is more important from a maximum voltage POV. IE - if running with engine off, or if the alternator is incapable of supplying the load or peaks, then the battery supplies the power.
In practice, the chassis/body is usually used as GND because (1) GND wiring from the engine/alternator and battery- should be appropriately sized for negligible voltage drop at the highest load; (2) the chassis is a good compromise for both battery- and alternator-supplied situations; (3) lots of or big GNDs to the battery- can be impractical and the same to the engine may have heat & vibration issues, and likewise to the alternator body plus its added cable-joining difficulty (and there should be negligible voltage drop between the metal-metal alternator body and engine - though my neighbor's Toyota 4WD with its angled Nippon Denso alternator and up to 1.5V between alternator body and engine block is testament to exceptions, but its solution lies in proper mounting of the alternator and maybe additional bonding - NOT routing all GNDs to the alternator body. ]
BTW, though fuses etc and the +12V supply can be lost, losing GND can be VERY destructive. (Alternate GND paths will carry the load current and associated wiring and circuitry burns out - eg, RCA connections and internal "signal" GNDs in audio systems; alternator to external body-mounted voltage regulators (in old vehicles), throttle cables, sensor shields etc for engine GND to battery- losses.)
Hence the attraction of chassis/body grounding points, else distribution blocks from the battery-/GND.
And except for exceptionally high currents (and allegedly some vehicles with poor inter-panel weld bonding), the chassis/body should be a good low resistance "equally grounded" circuit. (Being aware of loosely bonded and bolted panel and
thin panel limitations.)
Back to your
circuit details...
Hence presumably all your amps are turned on thru their remotes.
And if all the remotes are +12V to turn on (as I expect they all are), then you merely need a switch and relay to turn the on.
That could be a battery +12V fused switch to a relay's #86 (with #85 to GND) and fused battery +12V to #30 and out from #87 to the remotes.
If the remotes are low current, the relay may not be required if the switch can handle the total current. (I know of some remotes that apparently take 2A (in normal circumstances!). IMO that is ridiculous! At most it should be a relay coil (up to 250mA, ie 1.5A for 6 remotes) but IMO it should be of the order of mA to maybe 10mA, maybe ~50mA.)
Isolation diodes from #87 to each remote may be required depending on the remote circuit. EG - if the remotes are relays (coils) and one or more amps is unpowered, then the resulting +12V connection of series relay coils (with the remote-ON switch OFF) could cause some amps to turn on. The same could occur for other (IMO) badly designed remote circuits.
(There is a workaround by using an SPDT aka changeover or "5 pin" relay and connecting #30 to the remotes with 87 from +12V and #87a to GND, but that could mean +12V leakage thru the remote circuit and hence battery flattening...)
(BTW - most of us by SPDT relays even if using as an SPST (on-off). That's because they are usually the same price, and the one relay suits all SPST & SPDT applications.)
But the audio & amp aficionados hereon should be able to advise on the above given the amp model number(s). I am merely into electrics.
That's it - in principle a +12V switch and maybe a relay that connects to the amp remotes. (A relay may be good since it could be mounted with or near the amps and manually bypassed for testing or if the switch circuit fails.)
Whether you use secondary batteries for the above (as I expect you would be!) and their isolation when not in use is a different issue and topic.
I hope that hasn't confustigated you, but in the interests of related background and issues...
If unclear or extra info is required, just ask.
And others may contribute their ideas.
As to relay terminal numbering etc, refer to the
Relay link above or search other threads. (Remember that a relay is just an "amplifier" for a switch - ie, it allows a 1A switch to control a 30A or 300A load etc - though they can do much more, ie voltage or circuit isolation, signal inversion, etc.)
BTW - a common 30A relay should be more than adequate. The switch or relay must be rated to carry the total remote-circuit load.
Of course, you might want to use multiple switches etc if not selecting all the amps...