Hello.

Just wondering if the AUX inputs are subject to picking up any noise, or
put another way: Will I benefit from putting a resistor on the AUX inputs???

TommyE

I'm not sure I understand your question... Do you mean "should I somehow terminate the aux inputs if there's nothing plugged into them?"

No, don't bother. Even if they did pick up noise, you wouldn't hear it unless you switched to the aux inputs from the remote control. Make sure they're covered and/or not touching metal, but other than that you don't need to worry about it.

If you mean "Are the aux inputs noisy when I plug another device into them?", then the answer is also no. They shouldn't be any more noisy than a set of aux inputs on any other car stereo. If you get noise, there are some standard car-stereo noise troubleshooting documents I could link you to.

___________
Tony Fabris

Thanks.

It was your first answer I meant.
It's just that I never get happy with my noise. It's not much, but I'm looking for ways to improve. Oh well, I'll live with it.


TommyE

It's just that I never get happy with my noise. It's not much, but I'm looking for ways to improve.

What sort of noise are you having, and what have you done so far to troubleshoot it?

___________
Tony Fabris

If you're using a non-grounded device on the aux input (eg, a portable CD player or MD player) then you need to connect the AUX ground to the car ground; it's designed to connect to other in-car components which share a common ground.

Hugo

Hello Tony.

The noise I'm having is probably from the alternator.
It's a whine from the speakers that is variable when I rev. up
the engine. (It is a diesel engine so I don't think it's anything
from the ignition system. I don't know this, but so I've been told.)


This is what I've done so far. If you look at the drawing it will
be easier to understand. (I hope.)


PowerSupply:
I've run a thick (4gauge) plus and minus wire from the battery. There is
a fuse on the plus wire in the enigneroom.
(there is a fuse on the plus to the empeg and all other units as well)
The wires are run under the drivers seat where it is split 4-ways into some thinner
wires. (8 gauge) Then the wires are drawn into the two amps, empeg and
elextronic x-over.

SignalPath:
I'm using both front and rear iutputs from the Empeg.
(Blue front, purple rear) They're are left/right, but I didn't
bother drawing it.
These are fed into the three way electronic x-over. This is
set up to split the signal into my preference for front/back.
I've connected the supplied earthlead on the AMP. for SUB.
This was the only place I could put it without a lot of funny
noises.

The gain on the amps. are not max'ex, so I can barely hear
the 'computer' sound from the Empeg, but as I said earlier
I have this alternator whine. (I think).

From your drawing, it looks like you have a Mk 1. Is this the case?

If so, you should add in the line filter (supplied with the unit) to the power feed to the empeg.

Also, you should have the Small inline RCA grounding cables inserted into the audio output path, at the amp end, with the earth leads attached to the earthing points for the amps (which should be common anyway). Also be sure to check that the amp earthing points are connected to the DC ground if your installation instructions say so - otherwise your amps could start to float above ground when delivering a lot of power (high return current) and cause noise problems due to earth differentials, grounding loops, etc.

One of the few remaining Mk1 owners... #00015

Things to try:

- Put a heavy-duty noise filter on the main power lead coming from the battery. Radio shack sells a 20-amp noise filter and it seems to be handling the load from my 3 amplifiers okay. This should happen fairly close to the firewall, before the power is split four ways.

- Make sure that all of your audio cables are routed far away from your power cables. Alternator whine is quite commonly caused by inductive noise from the cables.

- Locate any ground loop problems. This is tricky and arcane, but in your case, I'd start by disconnecting the crossover and one of the amps. See if the remaining single amplifier has any noise. If not, then add back in components one at a time (other amp, crossover) until the noise reappears. Then re-ground that component. If you need a "primer" on ground loops, let me know and I'll try to find one or write one.

- Go through these documents carefully:

http://www.installdr.com/TechDocs/999501.pdf
http://www.installdr.com/TechDocs/999502.pdf
http://www.audiocontrol.com/techpapers/tech1002.pdf



___________
Tony Fabris

I would like to second Tony's comment on keeping the signal wires away from the power wires. This is the most common cause of audio noise I have seen over the years and it will happen ever time if you aren't careful.

Keep them at least 1 foot apart. Don't even let them cross perpendicularly. Thats the distance I have found will work pretty good but it depends on a few things.

Alex Lear

then you need to connect the AUX ground to the car ground; it's designed to connect to other in-car components which share a common ground.

Hugo, can you elaborate a bit on this?

I have been unhappy with the results of my portable CD player feeding into the auxilliary input of the empeg, because when I turn the gain down on the portable player the floor noise (sounds like a 60-cycle hum) becomes quite noticeable, particularly if I am running the portable player by means of its AC power brick instead of on batteries.

How do I connect the AUX ground to the car ground? Am I supposed to somehow ground the portable player as well?

I apologize if these are silly questions, but as you know by now, I am not all that technically inclined.

tanstaafl.



"There Ain't No Such Thing As A Free Lunch"

To check that this is what is affecting your sound, just touch the shield of the aux input to the metal of the empeg case (or another grounded bit of car) and see if it affects the noise. If it helps, then you need to ground it more permanently - a loop of wire is the easiest way.

Hugo

just touch the shield of the aux input to the metal of the empeg case

Hugo, remember you are talking to a technical ignoramus here.

By "shield of the aux input" you must be talking about the outer (bare metal) portion of the coaxial lead where it plugs into the sled, right? Do I have to do this for both the left and the right channel inputs, or would just one be sufficient? Does it have to be done at the empeg end of the cable, or could I do it at the portable player end, where access is easier? (I'd have to unbend the bendy-tabs (technical term) and remove the sled to do it at the empeg end although making the actual electrical connection would be more difficult at the portable player end)

tanstaafl.

"There Ain't No Such Thing As A Free Lunch"

Hi,

On my sled, there are exposed shield from the AUX where the wires are crimped to the sled. Its the middle of the three wires running into the empeg.

Solder a wire from this to the black wire (ground) going into the empeg.




Lars

You can do the grounding anywhere along the cable - on the connection to the portable player, etc. The shield is the outer of the RCA socket, left and right grounds are connected together.

Hugo

Thanks for your tips.

I know I've crossed the wires a couple of places, and I think I have
no more than 15-20cm between them. I'll separate them and see what happens.

I thought I'd get hold of some spare powerleads, and disconnect the ones I use know. Put the spare ones directly to the battery, thru the window and see (listen) what happens.

TommyE

Thanks.

I'll be sure to read thru the PDF's. I checked with a local stereo shop
they didn't have any noise filters that could take as much as 20 amps.
I'll try alears tips about the distance between power/signal wires first, if this doesn't help I'll shop around the net.

TommyE

Hello.

Ok, I haven't used the AUX'es yet. I just wondered if I needed to 'terminate'
them, as I thought maybe they could pick up some noise hanging around in the back of the dash.

I'll probably use the for my laptop and some DIVX movies next time I'm going for a long trip. Nice to have someone to drive, and just relax in the vack with a movie or two. :)

TommyE

Or DVD's........

TommyE