Amplifier Help

[ThomasBrentnall]

Hello,

I’ve decided to amplify the speakers in my car. All 4 speakers are amplified the rear set are coaxial and the front set are component. I am using none of the standard Renault wiring. Sound quality is excellent however I am getting a buzzing noise through the speakers.

This noise only occurs when the engine is switched on and takes about 5 minutes to start. This does not happen with just the ignition switched on. To rule things out I’ve tried a different grounding location but this has not changed a thing. I have also tried disconnecting the RCA’s from the amplifier, but no avail. The video below demonstrates the sound; you will need to use headphones to hear it correctly.

http://www.flickr.com/photos/94289585@N02/9495408147/

So I thought it may be down to a damaged speaker wire, so I decided to disconnect all of the wires from the amplifier excluding 12+, remote and ground. I then got one of my spare speakers and a short piece of speaker wire and connected it straight into the amp. You can still hear the sound in the video below (sounds louder than the first video due to the speaker being exposed). Also things like flashing the headlights change the pitch of the sound so I’m guessing its alternator related.

http://www.flickr.com/photos/94289585@N02/9498257676/

(Sorry can't embed Flickr video directly)

Cheers guys

 

[Ryanph1rs]

Could be interference from the engine some place like a coil or something you can get noise suppressors.... It could and most likely be the amp I'd try another amp check and if its that.... What gauge power wire are u using too thin a wire could cause alot of resistance is a demanding system... Also clean up the earth make sure it's not near any other earths or power sources where it can pick up interference

 

[Dink]

it will be a bad earth somewhere i'd check all earths in the engine bay first (have you upgraded the one from chassis to battery as that is the first to upgrade)

 

[ThomasBrentnall]

Could be interference from the engine some place like a coil or something you can get noise suppressors.... It could and most likely be the amp I'd try another amp check and if its that.... What gauge power wire are u using too thin a wire could cause alot of resistance is a demanding system... Also clean up the earth make sure it's not near any other earths or power sources where it can pick up interference

Hi Ryan,

Unfortunately I don't have another amp to test, or another car to test mine in. Wiring kit is 8AWG however the noise occurs when no rca's are plugged in so there is no load on the system, I have also tried turning gains down but that has made no difference even though they was set correctly in the first place (not just turned up fully). I have tried two earth locations and cables, one onto the rear light screw thingy and the other on the isofix bar bolt.

​Thinking it may be to do with the power cable but I'm unsure

 

[ThomasBrentnall]

it will be a bad earth somewhere i'd check all earths in the engine bay first (have you upgraded the one from chassis to battery as that is the first to upgrade)

I haven't checked any earths yet (excluding amp to chassis). Currently not upgraded battery to chassis however I was thinking about doing 'the big three' to see if that will cure anything. However I will check all the earths first before I do anything else tomorrow.

Thanks for the advice so far guys!

 

[James28]

Yea I'd do the big three.

 

[l33th3tr33]

Big three?

 

[bionic]

im going to be taking a guess on this since i cannot watch the vids you have posted

try grounding your headunit rca's as you could have blown an earth track

 

[ThomasBrentnall]

im going to be taking a guess on this since i cannot watch the vids you have posted

try grounding your headunit rca's as you could have blown an earth track

Cheers for the help, but as mentioned no rca are plugged in!

 

[Harbinger]

The Buzzing is caused by the AMP, playing around with the settings such as bass control etc will stop it, what fuse does the AMP have? is the buzz constant like over music or only in between tracks etc?

 

[ThomasBrentnall]

UPDATE.

I decided to do some testing on the amplifier. To do this I took the amp out the car and plugged it into my test gear (see below) with no RCA's connected. Left plugged in for 10 minutes to see if the sound from the previous videos happened. Which it didn't so I know there are no issues with the amplifier. I also did some stress testing by hooking it up to two full range speakers and playing some music. Adjusting the HPF and gain settings to get the correct sound for the speakers. The sound quality from this amplifier is pretty incredible! I've uploaded a video here. (My phone does not pick up bass very well so it sounds a little 'thumpy'. Anyway I've had no feedback / interference through the speakers at all.

Amp Testing Gear by Thomas Brentnall, on Flickr


So I have put it down to the wiring in my car, I know that it's not the RCA or speaker cables as I unplugged all of that and used a single speaker and short piece of wire and still got the same effect. As previously mentioned I have also moved the ground and also tried a different ground cable from chassis to amp so I know this is fine.

Next steps

This has already been previously suggested, but I just wanted to confirm the amplifier was okay first. I will check all of the connections on the charging circuit to ensure no damaged wires. And potentially then do the 'big three' upgrade (however I can't see how the size of the cables will matter at this stage as no music was being played through the system so there is only a tiny current draw)

Cheers for you help!

 

[Dink]

the noise comes from the alternator but should be adsorbed by the battery

so that i why it is a dodgy earth/ground somewhere

if you have a multi meter set it up for current and start the car and put the amp on(loud enough so you can just hear it) til the noise occurs (try to turn everything else electrical off like lights, wipers, fan etc)

then put it between the batt - post and the chassis then move it to engine block then move to the amp and try it between the - terminal on amp and try various metal points in the boot to pick a ground

if at any point the noise goes away

 

[ThomasBrentnall]

the noise comes from the alternator but should be adsorbed by the battery

so that i why it is a dodgy earth/ground somewhere

if you have a multi meter set it up for current and start the car and put the amp on(loud enough so you can just hear it) til the noise occurs (try to turn everything else electrical off like lights, wipers, fan etc)

then put it between the batt - post and the chassis then move it to engine block then move to the amp and try it between the - terminal on amp and try various metal points in the boot to pick a ground

if at any point the noise goes away

I will give this a shot, however my multimeter is only rated for up to 10a and I'm guessing it's going to be higher than that?

​Thanks

 

[Dink]

you'd be surprised how little power amps use at low levels

just make sure everything is off in the car and you shouldn't have any problems

 

[ThomasBrentnall]

Okay what about between chassis and battery. Won't the draw more than 5with the car running?

Thanks again!

 

[l33th3tr33]

Seeing as I didn't get an answer the first time round, can I ask what the 'big 3' is?

 

[Dink]

it wouldn't run if you didn't already have some sort of earth so it won't see all the current


the big 3. is the cable from alt to batt +, from chassis to batt - and from chassis to engine iirc

i found just upgrading the chassis to batt - was enough to sort out most of the volt drop i was getting (i was running a 1000w amp @ 1200w lol)