4 Channel Amp wiring issue

[PumaNoob]

Hi all, i attempted wiring my amp up today, but it didnt work out, the speakers croak a little to the beat, but thats about it!!!

The AMP is a 4 channel Philips DAP 6040, and the head unit is an old Kenwood KDC W7031.

The head unit has 4 amp outputs on the rear, 2 front, and 2 back, so should be an easy set up, but it seems not. Ive wired the amp up with a perm 12v, remote from head unit, & earth. There is an additional input for a +12v acc, which im assuming is for a switched ignition live. It all powers up as it should, as soon as i put the head unit on, it powers up, and the little LED light comes on to show its powered. The outputs from the head unit are connected, and ive connected 1 car speaker to it just to check that everything it working as it should. But its not. There is a slight croaking but thats about it, even when i turn the volume right up.

There are a few questions i wanted to ask those in the know.

Do i need to disconnect all the standard speakers before it will work?

Is it possible that this amp was supposed to have the speaker outputs from the head unit going into the inputs on the amp rather then the Pre outs?

Ive plugged my Ipod directly into the AMP, as an input, and put the volume at max. This sounds better, and the music plays ok, but nowhere near the volume it should be playing at. Ive tried every different setting on the amp, hi and low pass filters, every different frequency setting, and all the mono and stereo settings, and it just wont go any louder. So i think it might work if the input signal was louder, but im looking for any other possible suggestions.

Thanks in advance

 

[evilrob]

I reckon you probably need to disconnect your speakers from the head unit - I imagine that croaking is just some kind of interference making its way out of your pre-outs.

I'd probably connect at least two speakers to the amp as well - they usually behave differently depending on what you've got connected (e.g. four speakers or two speakers and a sub etc.)

Other than that it certainly sounds like you've done everything by the book.

 

[PumaNoob]

Thanks for the reply Rob.

The croaking im sure is the sound coming from the headset, it goes with the bass line of a song, its sort of like when you dont plug a headphone properly in a socket, i think ill make a video and show you what i mean! Even so, when i plug the ipod directly into the input of the amp, its a known good source, and the AMP still doesnt go anywhere near the volume its supposed to, im not talking about minimal volume, i mean its about as loud as the average person talking. I might try putting a guitar amp between my ipod and the amp input, and see if it goes to the correct volume then. If it does, then maybe the outputs from the stereo arent strong enough, and i need to use the speaker outputs.

The other thing i was thinking is perhaps theres a setting on the head set that needs to be switched on or off to get the amp outputs working properly, or the amp will only output through the pre outs when the corresponding speaker isnt connected. Or the impedance of the ipod signal is wrong so its never going to be loud enough from that, i just dont know.

Is there a way i can check the pre outs for correct signal? If i wired the pre outs from the head unit directly to the speakers, should i not still get music, but at a lower level??

 

[evilrob]

The croaking im sure is the sound coming from the headset, it goes with the bass line of a song, its sort of like when you dont plug a headphone properly in a socket [...] the amp will only output through the pre outs when the corresponding speaker isnt connected.

Yeah, I reckon the croaking is signal leaking through the pre-outs, even though you have speakers connected so even though we're guessing that the headunit isn't supposed to be outputting anything via the pre-outs, apparently there is some signal getting out. You have used a decent quality interconnect cable between the headunit and amp right?

Or the impedance of the ipod signal is wrong so its never going to be loud enough from that, i just dont know.

I plugged my iPhone directly into my amp once and that also didn't go very loud even on full volume, though it was louder than a conversation.

Is there a way i can check the pre outs for correct signal? If i wired the pre outs from the head unit directly to the speakers, should i not still get music, but at a lower level??

I think the pre-out output would be way too low to power a speaker, not even quietly. I think the normal output is something like 2v.

You could try taking your stereo phono to 3.5mm cable (that you used to connect the iPod to the amp) and connecting the pre-outs to the line-in on your laptop?

 

[PumaNoob]

The phono cables are just cheap cables, i had them new with something i brought a while ago, i think a sony blu-ray player, but i wanted to make sure everything was cool with the amp before i spend on better ones. they are gold on the ends, but they dont look like top of the range jobbies! They work fine on my hifi, and there are no shorts when moving the cables about, so although they might not be perfect sound, they should get me in the ball park, at the moment im not even in the right postcode!!!

Ill give that a go, but rather then plugging the pre outs into my laptop mic input, ill plug it into my guitar amp input. Thanks for the idea. Yours might have been louder because the speakers were in the bins and there was more then 1 of them, mine was just a speaker on the seat!! :lol:

 

[evilrob]

Ill give that a go, but rather then plugging the pre outs into my laptop mic input, ill plug it into my guitar amp input. Thanks for the idea. Yours might have been louder because the speakers were in the bins and there was more then 1 of them, mine was just a speaker on the seat!! :lol:

Good call - I suggested the laptop for portability, but if it's just as easy to hook your guitar amp up, that's even better.

If you find that the head unit is outputting as expected via the pre-outs (or outputs as expected after disconnecting the speakers) and you're still not getting any volume from the amp, I reckon it might be worthwhile hooking a pair of speakers up to the amp - it might not be outputting because it's not detecting a circuit on both channels.

It's a long shot, I know, but my amp has various ways of wiring up the speakers that causes it to output differently; like if you wire the negative of the left channel to the positive of the right channel it triggers 'bridged' mode for delivering higher power to a subwoofer.

If you're still getting no joy, I think you're down to looking through all the settings on the headunit and seeing if the pre-out gain has been set to zero or something silly like that.

 

[evilrob]

Have you tried plugging your phono leads into the other pair of pre-outs - i.e. are you sure the outputs are front and rear stereo? It might be that one pair of phono jacks is a dedicated subwoofer out or aux in, and you only have one set of stereo pre outs?

 

[evilrob]

I found the manual online in case you don't have a printed copy handy / lost it / whatever.

Had a quick skim through - looks like all sorts of bonky settings in there you might want to play with.

 

[PumaNoob]

Yeah, I plugger all 4 pre outs into the amp, and then tried the speaker on all the different channels, incase it was a channel down or something. Ill re-check all the connections, and have another look tomorrow at the settings. Ill also try unplugging the speakers too and report back. Thanks for your help mate, at least I have a few ideas I can try out!

I've wired amps for mates before, but only mono block amps for subs, I don't want a sub, I just want better quality sound from my car!

 

[madhillbilly17]

i had this problem years back and ive been trying to rack my brain what it was! i think mine was a the ground connection wasnt good.

 

[PumaNoob]

i had this problem years back and ive been trying to rack my brain what it was! i think mine was a the ground connection wasnt good.

Thanks mate, ive double checked the connections an im getting zero resistance at ground terminal, and full voltage of the battery at the positive, so i think the connections are all ok.

I took a vidoe of how its sounding now, as my description wasnt very goodt sounds like ive got it turned way up and thats whats distorting it, but i play my ipod at the end, and the built in ipod speaker is louder!!!

Video:

 

[evilrob]

Hang on - in the video it still sounds awful when you plug your iPod in?

 

[PumaNoob]

Its only playing from the ipod through the stereo, not directly to the amp.

 

[evilrob]

Ah - gotcha. How does it sound if you play a CD from the headunit? i.e. have you tried another source other than aux in on the head unit?

 

[martinthrapston]

have you checked settings on headunit as some you can change the output for either sub or speakers k:

 

[evilrob]

Function of the KDC-W7031 In Standby mode

Switching preout
Switching the preout between the rear and subwoofer. (In subwoofer it outputs without effect from the fader control.)

Key: "Display" - Setting

• "SWPRE : Rear" - Rear preout.
  "SWPRE : Sub-W" - Subwoofer preout.

 

[evilrob]

Function of the KDC-W7031 In Standby mode

Built-in Amp Setting
Built-in amplifier is controlled.
Turning OFF this control enhances the preout quality.

Key: "Display" - Setting

• "AMP : ON" - The built-in amplifier activates.
  "AMP : OFF" - The built-in amplifier deactivates.

 

[evilrob]

Dual Zone System Setting

Setting the Front channel and Rear channel sound in the Dual Zone System.

Key: "Display" - Setting
"Zone 2 : Rear" - Sub source (Auxiliary input source) is to be rear channel.
"Zone 2 : Front" - Sub source (Auxiliary input source) is to be front channel.

 

[evilrob]

This manual is terrible - wtf do these things mean and/or do!?

 

[PumaNoob]

Ah - gotcha. How does it sound if you play a CD from the headunit? i.e. have you tried another source other than aux in on the head unit?

Its exactly the same with a cd or the radio, i just didnt have a cd to hand for the vid and wanted to show the ipod internal sound as a comparison for volume.

Ive played with the dual zone settings, they change nothing, i think its something to do with bass in the rear speakers.

have you checked settings on headunit as some you can change the output for either sub or speakers k:

Ive not done that, i really need to check the manual for different settings. What i have messed with so far is different built in high pass and low pass filters in the head unit, bass frequency, but to no avail, but i think you could be on to something ill have another play with the settings. Just has a quick look over the manual and found there is an additional menu ive not looked at, but ive not managed to find how to swap from sub to speakers.

But wouldnt the sub still play music, or would the different frequency make it sound like this???