Amplifier Ground Question...

[biju]

I have a question I'm hoping some of you could help me with.

Disclaimer: I know some might chime in and debate where to ground your amps. Some people say as close to the amps as possible, and some people (i.e. JL Audio) say to ground back to the battery. That's not really the question I have. With that said here's the question:

Is there any issue (cost aside) with grounding (via a dist. block) as close to the amps as possible, AND then also running a ground all the way to the battery?

I currently have four PPI amps (a100, 2xa600, a1200). Ground is provided by 4gauge from each amp to a dist. block. From the dist block I go 0/1gauge all the way to the battery. Running the ground back to the battery was PERFECT for my old two amp set up. However, the new setup there's introduced engine whine/alt noise.

I've troubleshooted the entire system, and have come to the conclusion that it must be way too much power to only depend on the 0/1gauge ground back to the battery. Fixing it will be easy, I'll just ax the ground to the battery, and ground closer to the amps.

So, back to the question. Before I take the above actions, I'd like to know if there is any 'harm' or disadvantage in keeping the ground back to the battery and ADDING a ground to the frame closer to the amps? Here's a graphic to help clarify my Q:

http://www.bijulab.com/images/GROUND2.gif

Thanks all!

-biju.

[psychos2]

I would try the short ground first.If the noise goes away, try reconnecting the battery ground so you have both connected. If no noise leave them both connected. I have always grounded close to the amp and have had no problems. shawn

[Locomigo]

Biji,

The distro is the proper way to run the ground. Technically, the current flow from ground to battery, so while it is "electrically" the same point (neg battery terminal and frame), I always liked to have ground and return hooked to the battery.

With the second possibility, there is a very good chance tht is would create a "ground loop", and cause more issue with noise. As the current with flow into the path of least resistance, I would suspect that the frame ground closer to the amps would be the most likely path (60-75%) for the ground to be utilized and the ground running to the battery will be the least utilized path (25-40%).

According to a quick lookup I did of the amps and current draws, it looks like they pull 15A, 20A, 40A respectively to your listing. This would be a conservative 75A total draw. Allowing for a 20% cap, lets just call it 100A draw.

So with 100A draw, say 25' from amp rack to battery with the routing making a 50' loop distance for the power path. This would make the sizing:
111000 CM or a little more than a 1/0 cable, based on a 1/2V drop, so that makes the need to have a 2/0 cable or 2(2AWG)cables. That or reduce the loop distance to no more than 47 feet (22.5' each conductor)

222000 CM for a 1/4V drop, which would make the cable sizing @ a MCM250, or 3(1AWG), or 2(1/0) @ 50'

Handy DC power calculator:
Vdrop = 11.1 x Length (ft) x Load (amps) / cable size (circular mills)
Transposed:
cable size (circular mills) = 11.1 x Length (ft) x Load (amps) / Vdrop

Good reference for cable sizes in circular mills. So long as your total CM add up to the result of your formula you are golden whether that is one or multiple cables.
http://www.houwire.com/products/products.asp?parentcatid=1&catid=5

Hope that helps:

[mjd709]

Here's a thought about whine/noise...

I ground close to the amp. I got rid of whine/noise with a Ground Loop Isolator from Radio Shack. Plugs in between the RCA pre-amp outputs and the amp. $15. Noise gone.

[biju]

It did help - and then some (I think. Depends on how much of what you were puttin' down I was able to pick up!)! Thanks. I owe you a beer or two when we get to Zu!

So from what I've been able to understand... You're saying it's best to just ground from the dist. block directly to the floor/frame using the 1/0ga?

If all else fails (granted I have ZERO equipment for measuring this stuff) I'll just try both schemes and report back as to what worked best audibly.

-biju.

p.s. - so, why did you quit the business? sounds like you picked up some really great knowledge/skills, etc.

[biju]

Here's a thought about whine/noise...

I ground close to the amp. I got rid of whine/noise with a Ground Loop Isolator from Radio Shack. Plugs in between the RCA pre-amp outputs and the amp. $15. Noise gone.

...Good point. I've thought about it, but doesn't adding the in-line isolator reduce signal strength (voltage), etc.? I'm asking because I honestly have no idea - and want to make sure I maintain the sound quality, etc.

Thanks.

-biju.

[Tone]

Grounds should be as close to the amps as possible - a distro there would be fine. Definitely increase the size of the ground at the battery to the frame and engine as well as the positive from the alternator to the battery. And be sure to fuse / circuit breaker the positive @ the battery with the appropriate value.

[Locomigo]

...Good point. I've thought about it, but doesn't adding the in-line isolator reduce signal strength (voltage), etc.? I'm asking because I honestly have no idea - and want to make sure I maintain the sound quality, etc.

Thanks.

-biju.

Agreed. Those are a worthy fix, its effectively a tank circuit, which takes the excess "noise" and grounds it. While I havent had experience with this adversely effecting the sound quality, it is more of a band-aid type fix rather than a permanent solution.

Just seems odd to me, that by adding a couple amps, you induced whine. This as I reference earlier is probably because you are slightly undersized in your main cables to the battery (exceed ampacity rating of the conductor).

Like I say, I like to run both ground and return to the battery.
If, for ease of attempting, you want to try to ground near the amps, then that should be acceptable, but you definitely want to disconnect the feed to the battery so as not to introduce a ground loop as I referenced previously. With your 1/0 local (to the amp) ground, then that would reduce the loop distance enough to be within the ampacity rating of the cable.

Whatever you do, ensure that both conductors (ground and return) are the same size on ALL circuits.

Feel free to give me a buzz... 303-478-7568

[Locomigo]

p.s. - so, why did you quit the business? sounds like you picked up some really great knowledge/skills, etc.

First off... The pay is pathetic.
Secondly, after completing my EE (Electronics Engineering) degree, I pursued other aspects.
I was a DC Power Engineer for 4 years, before the .com bust and 9/11 occurred which was a one-two punch for my industry and things dried up.
And now, I am back into the A/V industry, but on the commercial side.

[mjd709]

I haven't noticed any signal degradation using the GLI. It cleaned it up pretty well. Might be a good last resort for you.

[Tone]

Whine typically is coming from the head unit. Try disconnecting the rcas to the amp and see if the whine is still there. If not, then it is definitely at the headunit. Try moving the head unit ground wire from the harness to the body. We ahve also had to ground the RCAs at the deck to the body in some cased. I had this problem in the ML with both the D1 and the new AVIC-Z1 (which by the way is increadible - I look forward to showing it in Moab).