bump

how has this gone? i have an audiocontrol linedriver with ground isolation that i've honestly been too lazy to play with. maybe if this damn rain would stop...

 

So I finally found some time to take the PG line driver and play with my car. The snap is pretty much eliminated when the line driver and amp both have the gain at min. That is good. The bad part is the noise that won't go away. If I turn up either gain the whine gets worse. I am 99% certain that the whine and snap are related to the balanced output of the HU, and the amp not knowing how to handle it.

I also noticed this to be the cause of minor distortion with my tweeters. Ever since I changed the amp out I noticed a very faint distorion up front. It wasn't serious, but did take away from having a totally clean sound. While playing with the line driver I noticed that the shield from one channel was driving another channel. The other thing I noticed was that if I used higher quality RCA's, the problem got worse. This all points to the problem being caused by the balanced outputs. I have tried using a GLI, and it helps a bit, but not enough. Pretty sure the GLIs I have are junk, and need to try better ones.

So - long story short - I think most of the sound issues are due to the Alpine amp not being able to accept (cleanly) a balanced input. I am not the first to bring this up, but lots of people have had different problems. They may all be related to this.

Shortly I am going to try a few different things to see if I can fix the problem. Basically I will play with different shield set ups and GLI configurations. I will post any progress I have.

 

Has anybody tried some of the audiocontrol eq's like the Four.1? It says it excepts a balanced input and you can select whether you want it to send a balanced or unbalanced output to your amps. To me this would seem to eliminate the problems but maybe someone has already tried this.

 

So I finally found time to play again, and made a few new discoveries. Nothing that really helps me, but interesting at least.

I rewired the factory amp back in, and used the speaker level as input into the line driver. No GLI - had some whine, but no noticeable snap. Threw the GLI in, stil had the whine, still no noticeable snap. Both of these had the GLI up front near the stock HU.

I was annoyed that even with the factory amp I was hearing the whine, so I went back to the RCA inputs. With HU-RCA-GLI-Line driver-aftermarket amp setup, I still had the whine, but no snap. I moved the GLI to right before the aftermarket amp, and the whine was reduced (but still there). The snap was now really noticeable.

For my setup it seems that the GLI seems to cause most of the snap problem. Unfortunately the GLI I am using doesn't fix the alt whine I hear. The next thing I am going to try is a better GLI. Right now I am using a cheap Scosche GLI.

 

Bumping this long-forgotten thread. Before I go into anything, I should ask - has anyone been able to completely eliminate this problem? It seems that all "solutions" have been more like compromises.

Anyway, the RF designers in my office recently had to take a digital design course because apparently some of us were screwing up the digital portions of our designs. The smart dude leading the class went into the subject of ground bounce fairly extensively, and it sounds like the "snapping" problem is a symptom of this phenomenon. Basically, when the air conditioning switches off, the device (head unit) ground "bounces" relative to the chasis/amp ground.

While it's gratifying (somewhat) to put a name to the issue, I'm no closer to a solution. Improved grounding of the head unit or a GLI should solve the problem... but it doesn't seem like anyone's had luck with that.

...or maybe I'm way off.

...or maybe someone has had some luck with this but hasn't shared.

 

Let me state I have no idea, but in the interest of discussion... If "ground bounce" is a problem, I'm gonna say you can't improve the ground and eliminate the problem as there isn't an earth ground in a car. I would think if anything, you'd need strict regulation to overcome the problem. But then again, maybe not. Can you explain the phenomenon a little further?

 

Does not having the problem count? Technically, it should.

We just did a 2006 TSX non-nav using the F and R outputs into a DLS 3-channel amp, and we had no problem at all.

So this makes like 4 cars with no noise, and one with no noise until the gain was turned up, which was addressed by a line driver.

This leaves the following possibilities:

1) The HU is bad in your cars.

2) The HU ground path is bad in your cars.

3) Your amps are not appropriate.

4) Your installation is the problem.

Logically, those are the only possibilities.

 

Entirely plausible, but I had my HU replaced b/c my AC lights had gone out. The snap occured(s) on both HUs. This, I'd say, rules out a problem internal to the HU.

Gets my vote. I was just hoping for some feedback from others who might have had success with this route.

Gets my second vote. But for those of us who don't have amps laying around to help with troubleshooting, we're still stuck. It wouldn't be a bad idea to make a list of amps fed that, with fed with pre-outs, don't suffer from this HVAC switching ground-bounce issue. If someone has an issue-free install with amp X and another person has snapping with amp X, then we've anecdotally ruled out amps from the equation.

There's only so many places an install can go wrong - I've gone over my install with a fine toothed comb over the past 1 1/2 years. Atleast in my case, I'm confident that the install is not causing the snapping.

 

I'm thinking DLS amps are one of the few that will work flawlessly with the TSX HU. It seems like JL and Alpine have problems with it. I still have a few problems. I treat my minor whine like its the sound of my turbo that I don't have. That kind of helps me deal with it

 

The fact that chassis ground is not earth ground is irrelevant. The real issue is the inductance between HU ground and chassis ground allows a "blip" in the ground path. If the car had a (theoretical) single-point ground, then there would be nothing in the ground path on which a voltage would develop.

 

I googled "ground bounce" and the first couple of pages deal with the phenomenon at the logic level and discusses the use of bypass caps. I'm not a EE and I don't claim to understand what I read. However, if I follow what you're saying, could you not simply test your theory by re-grounding the HU & amp to the chassis or connecting the two grounds and run a wire to the (-) battery terminal?

 

I think that whole thing is total wanking.

I had no snaps or whine in my car with a JL amp in it when the gains were low enough, and no snaps when the gains were higher.

I know people who have Alpine amps in that car who don't have snaps.

We had no snaps in Joerockt's TSX with a Kicker amp, even when we did have whine with the gain up.

Snaps are not something that "magically" goes away when a DLS amp is used.

The snaps seem symptomatic of a DC burst out of the HU. If you had a transformer in the signal path, such as in a GLI, DC shouldn't make it through.

Has ANYBODY tried an Iso Max CI-2RR yet?

 

Eh, whatever, he's not claiming that's the reason, it's just speculation. I've not experienced snaps (Alpine nor JL), but I would like him to test his theory and report back. And for that matter, you have a 'scope, you could test your DC theory as well.

 

Interesting point of view...

The snaps are independent of gain. My setup is:

(Sirius tuner -> SHOND3 aux connector)
-> HU -> female RCA -> 2 ft RCA cable
-> Audiocontrol Matrix Line Driver (has ground loop isolation, +12V from wire bundle off HU)
-> 12 ft RCA cable -> Aura 4-channel amp

There's some alt whine in the system, but this is easily handled by turning down the amp gains.

Is this another GLI?

 

thanks.

really, El D and i are talking about the same phenomenon - just using different terminology. i'm trying to find the cause of this transient voltage whereas El D accepts that it exists and wants to tame it with a GLI or by calling my setup (and others') "wanking".

i'm going to try regrounding the HU when i get a chance, but i'm doing some home renovations (putting in a bathroom) and i live 2 blocks from dozens of bars...

 

Apologies, I communicated unclearly.

I was referring to the "ground bounce" discussion. The problems being experienced are real. Delving that deep into esoteric electrical theory will not yield any workable solution that would not be doable, more directly and more easily, by following different paths.

 

back from the dead...

I actually have these exact same snaps on a COMPLETELY STOCK 06'. Snap happens when AC fan shuts off. So I believe this may be a head unit issue. It's at the dealer now, should I tell them to investigate the HU grounding?