Bi-amp setup wiring help

kenstewart

Request assistance with wiring second amp. Here's my current setup:

Sony CDX-F7715X HU
Polk Audio DB570s in all 4 doors (60 watts RMS)
Audiobahn A2002T 2-channel amp (bridged 200RMS)
Waiting on sub (next week) to hook up to Audiobahn amp

Ok, now I want to hook up my second amp (also arriving next week) to my four speakers. It's a Profile California 4400 4-channel (50 x 4 RMS). I had the installer hook up a power distro block inside my cab for multiple amps. Now is where I come in (with no experience hooking up amps) but figure it shouldn't be too hard. I know thru reading to ground them both to the same spot and ground the highest RMS one first and then the other on top. Here's my questions for the rest of the hookup:

- Do I need to run a separate fuse, or is the one fuse intended to cover both amps since they're run off the distro block?

- What amp fuse should I get? current fuse is only 25 amps

- How should I run the remaining wires (other than the speaker wires)?

- Lastly, the installer ran both power and signal wires on the same side of my Sport Trac for my Audiobahn. He said this is not a problem for a sub, but definitely separate for speakers. Is this true? Everything else I've read says to separate power and signal wires, but nothing specific on if it's a dedicated amp to a sub.

Any help appreciated,
Ken

MacLeod

You dont need to run a seperate fuse at the distro block but it cant hurt. As long as youve got a fuse on your power wire before it passes thru the firewall, and that each amp has its own fuse youre all set. Ive never ran more than one fuse at the firewall and Ive never had a problem.

Im not sure I like running ANY signal wires alongside the power wires. It actually sounds more like and excuse to get out of doing extra work. If you have 30 minutes to kill one day you may want to switch em. However if youre not getting any noise thru it then dont worry about it.

As far as other wires, run the RCA's from your head unit to your amp and your speaker wires from the amp to your speakers. Dont forget the remote wire. Its usually the blue one or blue with a white stripe.

kenstewart

The power wire fuse is in the engine compartment before going thru the firewall. Since I'm running two amps though, guess I should get a higher amperage fuse???

For both amps to have the remote turn on, how do I go about doing that? There's only one remote wire off the head unit.

Any special things I need to know about running the speaker wires, as in do they need to be isolated from the power and signal wire of the second amp?

neomagus00

i for one am getting a bit confused about the usage of 'signal' wire here. run power cable down one side, speaker wire and remote turn on lead down the other. rca down the middle if you can, down the speaker wire side if you can't.

amperage for the fuse next to the battery, and the one in the d-block if you want one, is just the sum of the fuses in your amplifiers.

remote turn on - you can run it from the HU to one amp, then a short segment from that amp to the second amp.

kenstewart

sorry for the confusion neo, guess I'm trying to use what I thought was the correct terminology. The RCA cables are what I'm referring to as signal (as read on other forums). Ok, so I guess this is the way I should run all my wires for both amps:

Amp 1 (for sub) - already run by installer (power, remote turn on lead, and RCA cables are on the same side of the truck for now, will go w/Mac's suggestion of trying the sound first to see if there's any noise).

Amp 2 for speakers - power wire off power distro block; ground as described before; RCA cables down the middle to HU; and speakers, well directly to speakers I guess. Don't understand what you mean by running the speaker wires down the other side ... the speakers are on all four doors so will running them along the sill where the amp cable is (because of door speaker locations) cause problems? I thought the intent of separation was for the power cable and RCA cables to the HU be on separate sides of the vehicle.

exalted512

lies lies lies. Having your RCAs and power wire together is perfectly fine. Quite possibly one of the biggest myths in car audio.
-Cody

kenstewart

Alright, now I'm confused.

spwuinmk67

Depending on who you ask, depends on what answer you will get. Running them on the same side could cause noise problems, but with a quality pair of RCA's, they will be able to reject all the noise. I had a problem with my first car, but only after I added my second amp. Throw the RCA's on the other side, and no problem. Generally it's just a precaution, to be able to say I know it's not because of this.

exalted512

highly doubt it was because of the rca's being close to the power wire. ive had $10 RCAs zip tied to power wire before and never had a problem. i think its even been proven that power wire cannot interfere with signal cables.
-Cody

spwuinmk67

I'm not gonna say it was or wasn't, because in the same fix I switched RCA's to better quality ones, moved them both to the other side, and switched from my old JVC with 1 pre-out, to the DEH-960 with 3, so could've been one, or all of those.

neomagus00

a teeny bit of physics - a power line running at constant current will do nothing to a signal... as soon as it's not constant, like a big variable draw (read: bassline), then it can interfere. that goes for speaker wires, too, however they're not carrying nearly the power the powerline is.

there's no reason not to separate them, though.

MacLeod

Thats one myth I buy in to. Besides, how hard is it to keep em seperate.

Having them cross each other isnt a problem its when you run them the length of your car side by side is when the noise would come in.

And, correct me if Im wrong, but its not the current that causes the noise necessarily but the electromagnetic field generated by it. Right??

kenstewart

Thanks to y'all's help here, I'm near the point of knowing how to finish installing my bi-amp system. Something I was thinking of and would like clarification on is the actual hookup of my second amp. I have a power distro box under my seat where my one amp (for sub) is currently hooked into. I know to hook my second amp (for speakers) into the power distro box, but unclear about the RCAs. One diagram I've seen shows to hook them up to the HU, but what about daisy chaining to the first amp that has preamp outputs? Is this a possibility or should I avoid it and go to the preouts on the HU?

AustinKP

Originally posted by MacLeod
And, correct me if Im wrong, but its not the current that causes the noise necessarily but the electromagnetic field generated by it. Right??

Actually, you are wrong. Neo was right in that a steady current causes to interference. The problem is when the current changes. That is what causes a moving electromagnetic field. The lines of flux moving across a wire are what cause interference. Thus, crossing wires at right angles can help since the lines of flux aren't inducing changes in the wire.

Ken, you should have a pair of rca's on one amp that you can hook up to the other one. They just pass the signal through without amplifying it. That way you'd only need an RCA cable a couple feet long, instead of 16' or so.

-Austin

neomagus00

austin - you're both right . yes, it is the EM field, specifically the change in said field, that causes interference, and yes, changing current causes changing EM field. and also yes, because of the shape of the field surrounding the wire, crossing them at right angles induces little to no noise. same reason inductors in xovers are mounted at right angles to each other (take a look if you don't believe me ).

and ken, what austin said is (again) right, you can use a very short RCA to go from the preout of one amp to the input of another.

kenstewart

Fantastic! That definitely sounds easier. Thanks guys and I'll let you know how the install goes (and sounds).

kenstewart

Update ... after looking at the second amp again I realize I can't go with the short RCA/daisy chain option. Reason is I don't have a separate input on my Profile amp for a connection from my Audiobahn amp ... just my four channel inputs. So looks like I have to run my RCAs to the four preamp outputs on my HU right? My audiobahn is connected to the subwoofer preout of my HU. Installing tomorrow so any final help is appreciated. Thanks ...