Stereo Noise From Wideband O2
Turbo Mini Forums

I just installed my Innovate MTX wideband and I'm getting a buzzing noise from my dash mounted speakers. I'm using a small Amp also located in the dash area. I've tried a ton of things and can't seem to eliminate or change the noise. If I unplug the gauge the noise goes away so I'm pretty sure I've narrowed it down to that
Things I've tried:
-Replace the old battery ground strap with a new one
-Wiring the gauge in with the other gauges
-Wire the gauge on it's on separate circuit
-Ground the gauge in the same place as the Amp
-Ground the gauge in a different spot as the Amp
-Sand the ground points (on the body) to shiny metal
-Verify firm connection at ground points
-Move Amp around to different places to see if any noise change.

NOTHING HAS WORKED!
I can't figure it out! I'm pretty sure it's a grounding issue but I'm really not sure how to solve it. At this point I'm debating if I just give up on the plan for the wideband. Or maybe I should try a different Amp?

What's your audio source? Was it plugged in during your testing?

Audio source is RCA->3.5mm cable to my phone or iPod.

Things I tried related to that:
-Plug in/un plug phone=no change
-Unplug RCA cables=no change
-Touch ends of RCA plug to ground=no change

Here is the amp I have:
http://www.amazon.com/gp/product/B003HH9FI...arch_detailpage

I know it's nothing special but I haven't had any issues with it until I installed this gauge.

When you say "If I unplug the gauge the noise goes away" do you mean unplugging the power to the gauge or unplugging the LSU (sensor) cable from tha gauge ?

The heater part of the LSU is usually driven by PWM (rather than linear) and PWM is well know for generating electrical noise.

Whilst it could be a grounding issue, it could equally be noise just radiating from the heater power wires in the cable down to the LSU head.
Try moving that cable away from any other wiring (not just the amp wiring but all other wiring) or even wrapping it in aluminium foil (bacofoil) and connecting the foil to ground (just wrap a bit of bare copper wire around the foil at one end and connect it to ground).

Schrödinger's cat - so which one am I ???

I'd suspect noise due to the PWM switching of the sensor's heated circuit being injected onto the power wires... But you've pretty much already tested that thoroughly.

Does the tone or volume change in the first 30 seconds, as the sensor's heater ramps up? Any estimate of the frequency?

As a test, have you tried putting them on completly different batteries?

Does the noise increase when turning up the amp's volume control?

Following up on Phil's point about the noise could easily be being carried by the power wires (rather than the grounding) - with which I agree entirely - how are they both powered ?

The LSU heater will almost certainly be controlled by an n-chanel Mosfet which means it is switched to ground rather than switching the 12V but if there is the slightest poor connection in the complete route of 12V from battery/alternator to the Innovate thing that will amplify any switching noise.

A poor connection could be as simple as dirty contacts inside the ignition switch, or on fuse holder, or spade connectors etc., the ignition switch being a major suspect if both the amp and wideband are fed directly through it.

On my setup the widebands are fed through a seperate relay and fuse wired direct from the main battery cable where it is bolted to the starter solenoid, not through the ignition switch or any of the original loom.

Final point, if the noise is being carried on the 12V wiring there are a vast range of 12V filters you can buy specifically for this scenario.

Just google "car stereo power supply filter" or similar words.

Schrödinger's cat - so which one am I ???

I may be replacing my head unit with a small amp like that, so would be interested in how effective any power filters are. Let us know how you get on?

Can't you fit an interference suppressor?

https://www.facebook.com/pages/Fusion-Fabri..._homepage_panel

www.fusionfabs.co.uk



1/4mile in 13.2sec @ 111 terminal on 15psi

Got the noise to a point that I'm happy with after this weekend.

I picked up an inline power noise suppressor for car stereos (not the RCA type) and that brought the noise down a bit but it was still there. I think the best way to describe the sound was like an old dial-up internet modem...kind of.
Anyways, I found a buddy with an AEM UEGO wideband gauge and swapped that in. Without the filter it made a really high pitched buzz but then I put the filter in and the noise dropped to a very faint level. With the engine actually running and the music playing it definitely won't be noticeable.

The noise filter made the biggest difference but I think the type of noise injected between the two gauges made a difference in its effectiveness.

Regarding the stereo setup with this Amp, I couldn't be happier. It's cheap and small but it's plenty powerful for two speakers in the dash air vent pods. I also ran some larger speakers in the parcel shelf and it worked fine to drive those but a little quiet at high RPM.
I'd highly recommend the setup, I hate the look of pretty much all headunits and I only ever use my phone for music now so I don't need anything more than the 3.5mm jack. It's pretty nice and clean to have nothing but and on-off switch for controls (plus a input cable hidden in the glovebox).