Power For Amplifier

This section is where Audio / Telematics Posts will be placed temporarily

Moderator: RichardW

maynap
Posts: 11
Joined: 03 Oct 2018, 18:59

Re: Power For Amplifier

Post by maynap »

Hello everyone
I still haven't done the wiring of the amp yet, however by looking at the BSI there is 2 blue wires that goes in 2 connections, is it a +12v ?
What about taking the power from there ?? knowing that I have a fuse on my amp cable
Couldn't find a piggyback fuse in the local store
IMG_20181007_172636.jpg

User avatar
EDC5
Donor 2020
Posts: 1221
Joined: 01 Jul 2017, 21:48
x 104

Re: Power For Amplifier

Post by EDC5 »

If you look at my thread that I linked to before I used one of those two big 12v cables (white and blue) before I found a more permanent piggyback fuse solution.

I think when I checked they were both +12V

maynap
Posts: 11
Joined: 03 Oct 2018, 18:59

Re: Power For Amplifier

Post by maynap »

Yeah i saw that on your thread and would like to do the same I must check which one is the +12v

Xantippa
Posts: 447
Joined: 05 Feb 2012, 16:51
x 17

Re: Power For Amplifier

Post by Xantippa »

Now I have to very much disagree with GiveMeABreak. Always connect car amplifier directly to battery, and install fuse near (30cm or less) the battery. I would never connect amplifier to car´s own fusebox, unless it´s some very small amp that uses only couple of amps.

User avatar
Paul-R
Donor 2020
Posts: 5180
Joined: 07 May 2009, 16:24
x 706

Re: Power For Amplifier

Post by Paul-R »

There are some other devices which should be connected directly to the battery. One that I am aware of is a radio transceiver such as an amateur radio rig.

The idea is to reduce the possibility of injecting radio interference into the car wiring. There's even an argument that the negative lead should be taken to the battery as well.

User avatar
EDC5
Donor 2020
Posts: 1221
Joined: 01 Jul 2017, 21:48
x 104

Re: Power For Amplifier

Post by EDC5 »

I understand the point but I'm not sure on the technical reason for a power amplifier to need super thick cabling and direct connection to the battery.

The first stage of most amps is a PWM controlled DC-DC converter, so any noise on the car's wiring will pale in comparison to that and will be filtered out by the output capacitance inside of the amplifier itself.

As to the power draw, I understand that this might be really high momentarily driving the speakers, but these surges will be supplied from the post DC-DC converter capacitance and not directly from the 12v.

Demand on the 12v should be less 'spiky', and, as long as the cable is thick enough to match the fuse rating on the amp itself, I can't see any reason to go thicker.

User avatar
white exec
Moderating Team
Posts: 6564
Joined: 21 Dec 2015, 13:46
x 1133

Re: Power For Amplifier

Post by white exec »

That's right: the capacitors are key.

Xantippa
Posts: 447
Joined: 05 Feb 2012, 16:51
x 17

Re: Power For Amplifier

Post by Xantippa »

Amps really need thick cables (10mm2 and above in many cases) especially if you run them all the way to the trunk. Car´s internal wiring isn´t just up to that. And grounding should always be made with as short cable as possible directly to car´s body.

User avatar
GiveMeABreak
Forum Admin Team
Posts: 22614
Joined: 15 Sep 2015, 19:38
x 2341

Re: Power For Amplifier

Post by GiveMeABreak »

Xantippa wrote:
08 Oct 2018, 19:10
Now I have to very much disagree with GiveMeABreak. Always connect car amplifier directly to battery, and install fuse near (30cm or less) the battery. I would never connect amplifier to car´s own fusebox, unless it´s some very small amp that uses only couple of amps.
Marko - the suggestion was really to use the car's own fuse specifically for the Factory Fit Philips Amp option as that was already there. No point in drilling holes through the firewall - unless of course he's planning to put a 10,000W amp in!

User avatar
white exec
Moderating Team
Posts: 6564
Joined: 21 Dec 2015, 13:46
x 1133

Re: Power For Amplifier

Post by white exec »

10mm² copper will carry 80A. 80A at 13.5v equates to 1080 watt.
What sort of amp are you planning on? And please don't quote peak music power; RMS is what matters.
As said, it's a good amp's PSU capacitors that provide for peaks of power output (bass thumps, etc), and not principally the power supply cables.
Sorry, but some of have been working with high quality audio for a long time now, and are well able to spot gold-plated myth when we see it, and see the difference between Conrad and Maplin.

maynap
Posts: 11
Joined: 03 Oct 2018, 18:59

Re: Power For Amplifier

Post by maynap »

white exec wrote:
08 Oct 2018, 21:34
10mm² copper will carry 80A. 80A at 13.5v equates to 1080 watt.
What sort of amp are you planning on? And please don't quote peak music power; RMS is what matters.
As said, it's a good amp's PSU capacitors that provide for peaks of power output (bass thumps, etc), and not principally the power supply cables.
Sorry, but some of have been working with high quality audio for a long time now, and are well able to spot gold-plated myth when we see it, and see the difference between Conrad and Maplin.


It's a little amp nothing crazy, just enough to run my subwoofer
Pioneer GM-3500T rated at 180w x 1 @4ohm, Im running it in bridge mode, it has a 25A fuse on it form factory

Xantippa
Posts: 447
Joined: 05 Feb 2012, 16:51
x 17

Re: Power For Amplifier

Post by Xantippa »

Easy way is to look at how big fuse car amp has got.

Here´s a good calculator you can use: https://www.12voltplanet.co.uk/cable-si ... ction.html

For example a quite normal 30A amp with 10mm2 5m long powercable has got too big drop in voltage (over 4% or 0,5V). So 10mm2 is way too thin cable for 80A.

EDIT: For maynap´s amp 10mm2 cable from battery to trunk would be just enough, though 16mm2 wouldn´t be overkill either. And on C5 X7 there´s no need drilling holes, there are readymade holes on firewall already.

User avatar
GiveMeABreak
Forum Admin Team
Posts: 22614
Joined: 15 Sep 2015, 19:38
x 2341

Re: Power For Amplifier

Post by GiveMeABreak »

I think most of us just want a bit better sound, not necessarily a boy-racer setup: :shock:
car Amp.jpg
car Amp.jpg (13.02 KiB) Viewed 269 times

maynap
Posts: 11
Joined: 03 Oct 2018, 18:59

Re: Power For Amplifier

Post by maynap »

Xantippa wrote:
09 Oct 2018, 18:15
Easy way is to look at how big fuse car amp has got.

Here´s a good calculator you can use: https://www.12voltplanet.co.uk/cable-si ... ction.html

For example a quite normal 30A amp with 10mm2 5m long powercable has got too big drop in voltage (over 4% or 0,5V). So 10mm2 is way too thin cable for 80A.

EDIT: For maynap´s amp 10mm2 cable from battery to trunk would be just enough, though 16mm2 wouldn´t be overkill either. And on C5 X7 there´s no need drilling holes, there are readymade holes on firewall already.


Thanks , I have a 5m 10mm cable ready to be used
Do you have a picture of one of the holes ? have you done a similar install on yours ?

Xantippa
Posts: 447
Joined: 05 Feb 2012, 16:51
x 17

Re: Power For Amplifier

Post by Xantippa »

Look at driver´s side behind front suspension sphere, there should be hole that leads to driver´s footwell.

Now I have battery in the boot and amplifier inside dash (Match M5DSP), so a little different install. :lol: No pics unfortunately.