I am installing a second amplifier in my '68. It will run the front speakers. The primary power for the amp running the rear speakers is connected directly to the battery.

Can I connect the primary power for the second amp running the front speakers to the starter connection which is at the other end of the positive cable from the battery. ( I can run it through the firewall, which will be a very short run). Otherwise I will need to run a very long power line from the front of the car all the way to the battery.

Thanks for any replies.

 

What gauge power wire do you have run to the amp in there now?

What you need to do is, run 4-gauge power wire from the battery to a “fused distribution block”, (fused at what each amps fuse rating is), then from there to each amp. Remember to fuse main power wire within 12” of battery, just total both amps fuse rating together to get the size fuse you need, I recommend you use ANL, also known as, “wafer” fuse for this.

For ground, run the ground wire from the amps to a “non-fused” distribution block and from there use at least 4-gauge ground wire run to the battery since it is located in the back. The battery is the best place to ground on that body style, especially since it is in the back and will be a short run.

Remember that your ground wire needs to be the same size or larger than your power wire.

That is how you run power and ground to multiple amps. Do you need help with running RCA to two amps? Let us know if you do, it is quite simple as well. Your REM should be sufficient to cut on two amps, just splice into the existing wire and run to both amps. If it isn’t, then you will need a relay inline but I doubt just two amps will be too much for the HU to turn on.

Let us know how it works out or if you have any more questions.

:seeya

 

Nomad. Wow. What a cornucopia of information. Thanks so much. Let me give you my current and proposed set-up and maybe you can help me do it a better way.

Current set-up:

Headunit: Kenwood - 15W RMS/25W max (only one pair of RCA pre-outs)
Speakers: Rear - ADS 300i (Powered by 50W RMS/100W max Kenwood amp)
Front: Boston Acoustics 4" (powered by Headunit)

The RCA pre-outs from the headunit go to the Kenwood Amp which powers the ADS speakers. The amp is wired directly to the battery (both positive and negative) with 10 gauge wire (no separate fuse, I assumed the amp itself had a fuse which I have been relying on).

Proposed Set-up: Kenwood amp runs Boston Acoustics front speakers using speaker level inputs, a new US Acoustics 80W RMS/160W max runs the ADS speakers from the RCA preouts.

For the amps power lead: What you are telling me to do is to add up the fuse rating for both units (let's say 20A for the Kenwood and 30A for the US Acoustics for a total of 50A) and add a 50A fused distribution block within 12 inches of the battery and then from there to each amplifier. 4 gauge wire should be used between the distribution block and the battery.

For the amps ground: You are telling me to add a non-fused distrbution block off of the negative battery post and then from there to each amplifier. 4 gauge wire should be used between the distribution block and the battery.

For the switched power to the amps: You are telling me I should be able to splice the switched power lead from the headunit and run one lead to each amp.


Questions:

(1) Since I only have one pair of RCA preouts can I use "Y" connectors to create two pair and run RCA to each amp? If I split the RCA preouts won't I lose the ability to fade front to back.
(2) Is it a bad idea to use the speaker level inputs on the Kenwood amp for the front speakers?
(3) What gauge wire should I use from the distribution blocks to the amps? 10 gauge, 8 gauge, 6 gauge?

Thanks again for all the help.


[Modified by BB68Vett, 2:32 PM 9/23/2002]

 

When figuring the fuses, remmeber you are protecting the wire, and not the amps themselves.

Check this out..
0 awg = 325 amps
1 awg = 250 amps
2 awg = 200 amps
4 awg = 125 amps
6 awg = 80 amps
8 awg = 50 amps
10 awg = 30 amps
12 awg = 20 amps
14 awg = 15 amps
16 awg = 7.5 amps

(stolen from http://www.electronixwarehouse.com/e...s/wiresize.htm )

Theres also a wire size guide there.



[Modified by Kale, 12:35 PM 9/23/2002]

 

Ouch, that sux. Yes, you could use a “Y” splitter to run RCA to each amp and yes, you will lose fade, unless you have a 4-channel amp which will split the channels for you. The HU might need upgrading. There are several nice HU’s on the market with both front and rear low line outputs for under $200.

Yes, ordinarily amps have their own fuse (sometimes internal) and do not require an additional fuse inline before it, simply fusing at the battery will suffice, however, you will now be running two amps which means a distro block, the fuses are to protect the wire (always fuse power wire when you step down in size). It’s just easy to fuse the wire to each amp with that amps fuse rating, that way you know you will have plenty of protection for the wire since the amp will shut down long before the wire burns.

No, I guess I wasn't clear on this point. You essentially will be fusing twice inline before you get to the amps. First you will fuse within 12” of the battery with a fuse large enough to handle both amps (like you said a 50 amp fuse) then you will be fusing again at the distro block like I described above to protect the step down in wire gauge to the amps. Remember, you will be stepping down from 4-gauge coming from the battery at the distro block to about 8-gauge going to the amps.

Correct. :yesnod:

Correct. Like the power wire just run 4-gauge from battery to the distro block, then from distro block to amps. Remember you do not fuse ground wires and ground wires should always be at least the same size or larger than your power wire is.

Correct, simply take the existing REM wire you have now and splice another one onto it and run one to each amp.

Yes and Yes, unless like I mentioned above, you have a 4-channel amp.

I wouldn't, besides, you would have the same fade problem.

Just look to see what the instructions recommend each amp use. I would assume it is most likely 8 or 10-gauge power/ground input, but the instructions will tell you.

Any time. :seeya

 

Nomad, thanks for the clarification. I believe I understand it now. Just two comments. First, since my car is a '68 I will have trouble finding a spot for these distribution blocks and second, I have retained my 3 hole bezel for the HU and there are no three hole radios on the market that I can find that have two pair of RCA preouts. The Kenwood was a good choice because it has good features and is a high power unit. I may in the future cut my bezel to accept a DIN opening but that won't happen until this radio craps out on me.

 

Actually, distro blocks are so small you can fit them just about anywhere, like next to your amp in that pic you showed. However, after learning more about your situation, you may not need them.

I understand the problems faced when trying to fit an aftermarket HU with that old of a car, I have a '67 Vette in my stable. Since you have no glove box in a ’68 model, that eliminates putting a Din size HU in there.
As I see it, you have two options:

1) Look into A Custom Autosound HU, they might have one that will fit your Vette and have two sets of low line outputs.

2) This is probably your best option, in fact, this is what I would do. Instead of buying another 2-channel amp, get a 4-channel amp instead. Take out the amp you now have and replace it with the 4-channel. You can put a "Y" split on the RCA out, hook it to the amp and it will separate the front and rear channels for you. By going this rout, you can keep your current HU; you won't need any distro blocks and will be able to power all four speakers while keeping the ability to fade. You won't have to splice in a second REM wire either. In fact, the system will be wired the exact same way it is now. The only drawback to this option will be that you have a 2-channel amp sitting in the closet unused. However, it can always be used for another car or perhaps even sold. If you do this, I would still recommend that you upgrade to at least 8-gauge power and ground wire and don't forget to fuse at the battery with what that amp should be fused at. This is by far your easiest solution, less work and less money involved.

:cheers: