Sounds weird but I toying with the idea of putting a 2.1 plate amp into a passive sub cabinet But I want to keep the passive input. What do I need to do with a wiring? Is it as simple as a switch or do I need diodes?
You could try making up some attenuator plugs to bring the signal down and let the new amps re-amplify them.
No, that doesn't fit my objective. I'm considering: Mode 1 - 150w passive sub. Mode 2: 30w, battery powered 2.1 sound system.
A DPDT switch could shift between the plate amplifier's output and external amplifier input, center poles wired to the driver +/-.
If you add a switch to speaker-level wiring be careful with the electrical resistance of the switch in the closed position. A couple of ohms in the switch will attenuate the signal and perhaps dissipate some heat in the switch. I tired some switches in speaker level wires once and was surprised at the amount of resistance in my switch.
to avoid the risk of connecting amp to amp I would install a dual speakon connector dish:
Tuff Cab Large recessed connector dish for 2 x Speakon 4 pin from Tuff Cab PS2.48
then I would install speakon combo sockets:
NLJ2MD-H | Neutrik
I would connect the internal amplifier to the jack terminals of one connector and the speaker to both the speakon and the jack terminals of the other connector. When wanting to use the internal amp a jack to jack lead is installed between the two connectors. When wanting to use an external amp a speakon lead is connected to the speaker connector. Doing it this way it's impossible to make an inadvertent mistake.
Tuff Cab Large recessed connector dish for 2 x Speakon 4 pin from Tuff Cab PS2.48
then I would install speakon combo sockets:
NLJ2MD-H | Neutrik
I would connect the internal amplifier to the jack terminals of one connector and the speaker to both the speakon and the jack terminals of the other connector. When wanting to use the internal amp a jack to jack lead is installed between the two connectors. When wanting to use an external amp a speakon lead is connected to the speaker connector. Doing it this way it's impossible to make an inadvertent mistake.
Is the plate amp single ended or bridge? One wire to the speaker (other terminal ground) or two, both floating? What about the direct input?
Don't allow two amplifier outputs to be connected together, as that could cause serious damage.
My advice would be to use a relay rated for the speaker current to switch the speaker wires between the direct speaker input and the output of the plate amp. You can use a suitable input socket to turn on the relay when a jack is plugged into the plate input. Take care to avoid turn on and switching thumps. You could also use an electrical switch - a big switch capable of handling 20A. Don't use diodes or SSRs - they would cause distortion.
Use a shielded cage for the relay to avoid the magnetic field from interfering with the speaker. Ditto for the plate amp.
Don't allow two amplifier outputs to be connected together, as that could cause serious damage.
My advice would be to use a relay rated for the speaker current to switch the speaker wires between the direct speaker input and the output of the plate amp. You can use a suitable input socket to turn on the relay when a jack is plugged into the plate input. Take care to avoid turn on and switching thumps. You could also use an electrical switch - a big switch capable of handling 20A. Don't use diodes or SSRs - they would cause distortion.
Use a shielded cage for the relay to avoid the magnetic field from interfering with the speaker. Ditto for the plate amp.