V1 versus iPod -- Can There Be Peace?

[Jack Olsen]

Or at least quiet?

Here's my problem. On long drives in my 911, I wear noise-cancelling headphones to reduce long-term damage to my hearing. I also use a Valentine 1 radar detector to reduce long-term damage to my driving record and insurance rates. I listen to music through the headphones, although not too loudly. But it's enough that it sometimes makes me less likely to hear my V1 sounding off.

Now, my first plan to address this worked pretty well. I got the V1 remote display, and mounted it between my tach and the oil gauge. I can see it light up without having to turn my head at all. The V1 itself is mounted to my roll cage, and is a little bit out of my line of sight.

But I still worried about the sound not alerting me, so I came up with an idea: what if I could pump the V1's alert tone into the same line that runs to my headphones?

The first step of this was the most painful. I had to spring for the $49 remote audio unit from V1. I'm sure many of you could have tapped into one of the V1's cable lines and managed this for a tenth the cost -- but I thought I'd keep it simple. And I liked that the remote audio thingy would also allow me to turn the main unit on and off, and also control the volume of the tone.

So here was my plan: get a Y-adapter, like you use to share two sets of headphones with a Walkman, and run one line to the V1 audio box, another to the iPod, and the third to my headphones. When the V1 was being quiet, I'd only hear music, and when it sounded the alarm, I'd hear it through my headphones.

It all works fine, except that then the two units are connected together, there's a rhythmic noise that comes over the line, even when there's no noise coming from the V1. As long as it has power, I get the rhythmic clicking and humming.

Electronics make my brain hurt, so I thought I'd see if there's a simple thing I could do to get rid of this noise. I tried an in-line volume control from Radio Shack, figuring I'd crank the volume control on the V1 way up and the volume control would act like a filter of the quieter stuff, but it still doesn't eliminate all the chatter.

Any ideas?

[MichiganMat]

You're essentially mixing two signals on the same line which, without isolating the two, could cause problems. By joining the lines you're introducing a load on each amplifier (the iPod and the V1) which is going to screw with how they operate.

I've got to assume it can be done, but you're probably going to need some kind of basic mixing circuit that probably won't require any power. Im sure somebody on here has some electronics experience, hopefully they can dig something up for you.

I bet if you tied the grounds together and used a small diode inline with each set of outputs (maybe just the V1s will work also), then I bet you could get it working.

[84porsche]

Jack,

A couple of ideas depending on expenses would first be a noise canceling headset.
But as far as the splitter, the longer the distance of cabling the longer the more noise in the line. I would say first try different sets of earphones and it seems like you need to find a way to turn down the volume on the V1 but enough so you still hear it. Put your inline volume control before the splitter on the V1 and tune it down but so you can still hear it and that will reduce some of the noise portion. Also try a couple of different splitters (gold plated etc.).

Chris

[MichiganMat]

something like this:



Grounds tied together.
The diode will stop "back flow" of signals into each of the amps. Crude, but I think it will be effective. Anybody willing to prototype this?

[greglepore]

Yeah, the diode is the key, the ipod is likely backfeeding the audio output device of the V1.

[TOO RUF]

You need to isolate the the V1 from the Ipod using 2 Ground loop isolators. This should work. The diode will only start to work with a .7 Volt input.

[david914]

What you need is a small headphone amp with a 2 input stereo passive mixer on the front end. The diode idea won't work with an audio signal unless you want to introduce some distortion into the audio (this is one way some electric guitar "fuzz boxes" work).

There are headphone amps all over the internet. Do a search on "CMOY Headphone amp". The mixer portion can just be a couple of 100K stereo pots and a few resistors.

[masraum]

Just connect the audio out from the V1 to a relay that turns the fuel pump off. So when the V1 sounds and your fuel shuts off you'll know whether you hear it or not.

Simple really.

[Jack Olsen]

Okay. It looks like I need to spend more money.

Something like this?

[scottb]

If you're only using the iPod and the V-1, you'll need the two input version for $39.95. As such, it looks like a cheap and simple solution to your problem.

[Jack Olsen]

More to the point, the page addresses my mistake:

Q: I saw a "Y-Adapter" at Radio Shack._ It looks like I can connect my 2 audio devices into the "Y" and run them into my headphones that way._ Why not do this instead of using a mixer?


A: Don't do this!_ You can damage your audio devices by doing this._ Those Y-Adapters are intended to run 1 source into 2 outputs, not vice-versa!_ A Y-Adapter provides no isolation to protect the components from one another._ Using a Y-Adapter in a backwards fashion like this may result in one audio device trying to force a current backwards up into the other audio input device and damaging the audio jack of one or both of your audio devices--not a good thing to do._ It's trying force a current to drive the wrong way up a 1-way street._ The 2 audio devices need to be properly isolated so that the current will flow in the right direction (towards the headphones) and not damage the components, and that's what a mixer does.

[greglepore]

Yeah, didn't think about the voltage limitations on the diode.

BTW, if you haven't tried a CMOY or other (I like the dbPRO) headphone amp w/ your Ipod, you owe it to yourself to listen. Huge difference in bass and transient response.

[david914]

Jack, that passive mixer just might do the job. You will lose some volume from your IPOD, but if you feel you have enough "reserve" it should work fine. I have read about a way to increase the volume out of the IPOD by way of a software utility, but I have not tried it (no need - I'm not that deaf yet...).

[Jack Olsen]

I know that an amp would improve the sound of the iPod, but I try to listen to it at a pretty low volume. If someone honks, or the car starts making a noise, I still want to hear it.

[Gordo2]

Jack,

Non-technical approach, similar problem but inversed: I drive with my stereo turned up loud and can't hear the radar go off ( I can't discern the beeping due to my tinnitus anyway )

I mount the radar detector in my field of view vice center windshield and count on the lights to catch my attention vice sound. If you suction cup mount the radar slighly below the visor but not directly in your line of sight it will catch your eye.

An option that costs less than my 2 cents.

Gordo

BTW, appreciate your write up on your track day. Good enough to feel like I was shotgun.

[Walko]

Jack,

Dont worry about hooking up the audio just modify it to give you an electric shock each time it goes off that way you will lift off teh gas in a hurry,

My 2 cents

Michael

[stealthn]

Get the FM transmitter and play the ipod through your stereo (if you have one) then you can hear the V1 going off and the siren coming up behind you

[Don Plumley]

Noise cancelling headphones are great. However, from the CA DMV:

"...wearing headphones or earplugs (illegal in California and most states)"

While your V1 might prevent you from getting pulled over, your headphones may increase the likelihood...

[j. brian mulloy]

Geez Jack

You just added to my 'things to do' list before my project car gets on the road. My wife, in her own quaint way, says "I know you are doing something to the car as it seems to be disintegrating on a daily basis". It will be at least a year before I get it on the road.
I will post the 'rite of passage' photo (the one where a guy stands in his engine bay) soon.

Seriously, we share the same dilemma and once again, the august members of this board come through with some interesting comments and suggestions as how to resolve your question. Thanks Jack

Cheers
Brian

[Jack Olsen]

Double-post.