Pianoman72

I am attaching a small portion of the EWD, but the whole thing is scanned here for your reference:

https://www.clublexus.com/forums/sho...hreadid=115421

This picture shows 5 connections going to the STOCK AMP in a 1st gen GS.

Why the TWO power wires? +B and +B2

Then there are TWO grounds? E1 and E2

Also there's ACC and (not pictured here) another ground running to the stock HU AND an AMP wire.

Can someone help me understand why all this is necessary? I thought all you needed was power, ground, and the amp wire to get an amp going.

Darnit I'll have to attach the picture in the next post.

Pianoman72

pic

engin_ear

iTrader: (1)

Typically, there are three reasons for this:

1) In equipment design, we sometimes use more than one connector pin for current carrying capability. Connector pins are rated using a continuous ampere per pin rating, and if the average current required by the amp is larger than one pin's worth, a second pin will be needed, etc. Use of a second pin also does two other important things: it keeps the overall impedance across the connector down, resulting in nice low impedance power and ground connections, and more importantly in a car setting, it provides robustness - in case one of the pins becomes a loose connection, you don't have the amp constantly resetting itself;

2) There may be both digital and analog power and ground within the amp's internal PC board. Isolation of one from the other results in lower noise (a major source of noise in anything that has mixed analog/digital signals is digital switching noise getting into the analog power and ground). The power/ground connections are sometimes separated externally, using separate pins;

3) There may be more than one circuit board inside the amp. The power/ground connections may be made externally, to each individual board.

Choices 1) and 2) are most likely, given how the wiring diagram looks. The bottom line is, when dealing with this stuff, that power is not power and ground is not ground everywhere. There is always a reason that this is done in the car environment, never arbitrarily, because saving a couple of pins in a connector is a cost-saving item, so if they used more than the obvious, there's a reason.

That should clear things up.

engin_ear

iTrader: (1)

ACC is merely 12V that is ON when the ignition is on, so that the amp is only powered up when the ig = on.

The special GND that you see from the headunit to the amp is probably a dedicated signal ground that is run in the same cable/harness as the other signal wires. This allows the amp to use the headunit's ground as a reference, and/or use that ground differentially, which means that a balanced input is used inside the amp, where the ground reference is subtracted from the actual signals. This cancels out the common-mode noise (radiated noise picked up by the cable along the way will tend to be equal in the ground and signal lines), while retaining the signal.

Pianoman72

Thanks that's making a lot more sense now. So the reason I'm asking is because I am finally hooking up this aftermarket 5 channel amp in place of the stock.

Do you think it's safe to use these doubled power and ground wires since they're already there? Is there a safe way to test them with my voltmeter? I don't want to do something stupid here.

engin_ear

iTrader: (1)

Since the aftermarket amp will use more power than the stock amp, it is way better to run new heavy gauge wire (at least 8, 4 even better, depending on amp power and distance from battery) from the battery for +12V. Also use heavy gauge wire for ground and connect to nearest heavy chassis bolt and scrape paint under any washers for good connection. Don't forget to fuse it, or add a circuit breaker. Remote wire gauge not critical, I usually use 16 or 18.

Pianoman72

POWER:

Ok, I'm sure 8 gauge will be enough for my application. I think I'll leave the ACC wire alone and use the "AMP" wire as the remote wire. That way the amp is only on when the HU is on I assume.

MAKING RCAs:

I'm going to make RCA cables out of the + and "signal ground" (labeled SE# on diagram) for each channel. So that's 4 channels I'll have of RCAs. I'll test the signal strength, and then plug those into the amp LINE IN and put the new amp in "4 channel input mode."

I guess I also don't do anything with the speaker - wires and the extra Gound wire (pin 11 on diagram).

Hmm, that's it I guess. Post up if you see any problems. Refer to the entire diagram in my CL gallery or in the link in my first post on this thread.

engin_ear

iTrader: (1)