I'm planning to run the Bose HU remote wire to one aftermarket amp which will power new cabin and sub speakers.

I was given a strong recommendation to run a relay in this situation.

1. What does the relay do?

2. Do I need this?

 

The remote wire acts as a relay. When it receives power, your amp turns on.

 

You don't need a relay.

 

I did a google search and see people recommending a relay and/or a fuse as a way to protect the HU in case the amp shorts. There are several places selling a relay for the remote turn on wire.

 

I never used a relay in my previous installs but the strong recommendation from an audio installer has me questioning my previous installs. I dont think I need one either.

 

I have been a professional installer for a little over 14 years now. The only time you need a relay is when you are running multiple amps or the signal is too low for your amp. Don't sweat it. Its not going to hurt anything by tapping off the turn on wire. This is only common practice on large systems. Some installers will belive everything they hear.

 

A relay is an electronic switch. It will take a low current to activate it. Once activated, it will complete the connection for a bigger line by physically moving a piece of metal through a coil which will complete a circuit (for most relays) . Thus, it you can connect a line directly from your battery or your power block to turn on your amps.

I've never used more than two amps in a car, and I never had a problem with no relay. I don't know at what point you'd want to start using one, but I'm sure you can get away with at least 2. You almost need no current to really "see" a DC signal from a voltage source, so even if your HU was turning out like 200 mA, you'd be able to turn on several devices with ease.

If you really want a relay, they're pretty easy to wire and also fairly cheap. You can get a 12V relay at radio shack for like <10. Probably cheaper online, too. All you need is a ground connection, the remote lead from the HU, and a 12V from your main power cable. Then the last pin on the relay essentially becomes a "super remote wire" which could probably turn on like 100 devices.

 

The amp turn on wire actually switches a relay inside the amp to turn it on. You would be doing the same thing by adding an external relay to the turn on wire which would probably draw more current than the relay built into the amp.

 

Well you're missing the point with having multiple devices to turn on. Each relay still uses up some current so having a whole bunch of relays actually can drain a significant amount of current. This is why some high current equipment can actually have a relay for a relay, because it takes more current to power a switch switching a higher contact.

 

He only has one device to turn on so he doesn't need an external relay to turn on the internal relay of a single amp or even two amps.

A relay may be a good idea when using more than two amplifiers though, as you stated.

 

clearbra guy said it all pretty much.

think of relay as this.

say you need to go beat the crap outta someone...and depending on how big this guy is, you may or may not need to call your freind whos a 6'5" 250lb all muscle blackbelt.

if you are beating up one guy whos about hte same size as you, then obviously you dont need to call him, but if you need to beat up quite a few dudes at the same time, you will need him to do it. you will also need to call him if you are a 50lb weakling.

so basically:

you are the remote wire's power strength

your potential victim is the amp's need to turn on

and your big buff buddy is the relay

most car's stock system turn on wire, including hte 350z?g35's, is strong enough to turn on one or a coupla amps on their own, thus meaning you remote wire is NOT a "50lb weakling". so if you are just using it to turn on a couple amps, it is strong enough that it does not need a replay (big buff buddy).

it is in situations where you need to run on many many amps and sources with the wire (beating up a bunch of guys), that you need a relay, or if your remote wire's signal is extremely weak (a 50lb weakling)....as some car's premium systems are...but not in your car's case.

so anyway, thats how i explain it to my customers, though it certian takes less time and effort saying it than typing it lol

 

^ I like that analogy

 

The relay does offer a level of protection should something short out. This protection can also be achieved by putting a 500mA fuse inline with the stock wire at the source. Don't rely on the OEM fuses to protect the wiring if something were to go wrong - chances are if it is a fused wire it's fused at 10 or 15A.

I used a relay "back in the day" on a two amp system that had a bunch of cooling fans. I ran the cooling fans off the remote wire because I couldn't afford a thermostat.

Is it necesarry for your application? No
Will it hurt anything (besides your wallet)? No