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Thread: Low Stock Audio and Charging Issue

  1. #1
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    Low Stock Audio and Charging Issue

    I have hit 2 road bumps in my installation.

    First issue is a low audio output from the factory Bose system (relative to the Head Unit and no car pc).
    I am 90% sure the bottle neck is the Metra wiring harness.
    Code:
    Relevant system specs:
    2007 New Body Silverado Ext. Cab w/ Bose
    Metra Axxess GMOS Lan 02 wiring harness -- used to work onstar+chimes and connect pc front/rear channel audio out to factory bose.
    I say the low audio is the wiring harness because I had to rma one and the audio level was sufficient with the old unit (the replacement is a newer model with 'speaker level inputs' as opposed to RCA). With the harness' attenuator turned all the way up on the new one I get approx. 50-75% audio from the system. I also have 2 10" subs connected direct from sound card to a mono amp with no audio issues (so it is not the pc sound output).
    I plan to remove the small factory sub under my center consol and put the car pc there. Would that cause the factory door speakers to get higher output from the amp and potentially fix the issue?
    Any suggestions?
    Is there some pre-amp-amplifier that I could run between the pc and the wiring harness to boost the gain? Or bad idea?
    Its looking like live with it or buy aftermarket amp but I'd rather save the cash/time if I can.

    Second issue is dimming lights when the subs hit (noticeable with gain under 50%).
    There is virtually no feedback/noise from the engine so I'm inclined to say my ground is solid. Is that a correct assumption?
    I think the issue is from the alternator struggling to charge a second battery I put in.
    Here is my check list to try and narrow down the issue:
    • -remove second battery from the charging system and see if problem persists
    • -check amp ground
    • -check/replace battery terminals
    • -check gauge and upgrade big 3 if necessary (I have roughly 15ft of red 2/0 I could use)
    • -check alternator output w/ voltmeter

    The alternator is a 145amp. Would upgrading this to a HO fix things if I exhaust the checklist or would it be overkill for the approx 750 additional watts my system draws (500w bass rms, 250w pc PSU)? How many amps does my alternator need for this system?

    Ignorant on much of these topics if you cant tell!
    Thanks!

  2. #2
    MySQL Error soundman98's Avatar
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    for the first issue, yes a preamp will work--try any of them-- i think there is a PAC model, but there are tons everywhere.

    for the second issue--have you done the 'big 3' upgrade yet? it is very possible that is part of your issue. but i would still check your ground point-- whine is only a indicator of a difference in ground 'level'(potential) from another point in the system. it is entirely possible that your entire system has a poor ground point, but has the same ground potential.

  3. #3
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    x2.
    Removing the 2nd battery should make the dimming worse.

    The alternator is not struggling to charge the 2nd battery, but it might be struggling to power the load.


    What do you want to do - prevent the lights dimming, or prevent the amp's output dipping?

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    Most OEM alternators are rated "cold" and when they get warmed up to operating temps they lose a lot of capacity from rated amount. But this is different depending on the alternator. It is not uncommon for instance for a GM 130 amp alternator to only put out 90 amps when warm or a rated 90 amp alternator to put out only 60 amps.

    But for your system you should be fine.

    Upgrading the wire size would likely help you out dramatically but make sure you upgrade ALL of your wires. Not just the ones for your Amplifiers. Dimming lights with no whine is a good indication of undersized wires.

    If you don't have any whine or pops and clicks your probably on a good ground.

    You could also use a Capacitor near your Amplifier to help.

    Also make sure you use good quality connectors wherever the wires connect.

    Problem is that when you have too small of a wire or poor quality connectors the resistance of the wire or connector raises dramatically and if the resistance rises then you have less voltage making it through the line. Less voltage with same power requirements means more current needs to go through the wire. Your amplifier is likely to get very warm and you will be drawing way more current than you should be... A Capactior is more of a bandaid but provides the short burst of power you may need for the "thumps".

    Probably a 1 farad capacitor would be best.

  5. #5
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    ^ while i've gotten away from the "CAPACITORS ARE HORRIBLE!!" that i used to preach, i still think they are unnecessary in cars. sometimes they are unavoidable, but i think every measure should be taken before resorting to using them.

    caps are commonly used in household appliances like air conditioners for the main reason that you can't control the input power coming into your house-- so they get put on the a/c motor to reduce the momentary voltage sag that occurs when the a/c kicks on--there is just nothing else you can do to correct for it without getting the power company to do a massive upgrade...

    but in the car, you have complete control over the entire power system. if any single component is not up to the current task, then it can be upgraded far more easily then the power grid leading up to your house.

    for me, this makes capacitors a band-aid in car audio-- as in they fix things that have better ways of being corrected--like upgrading your power and ground connections, upgrading your battery(s). or upgrading your alternator. all of these things have the potential to correct for the same thing the capacitor appears to be doing, but allows for a much more stable power system overall.

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    Quote Originally Posted by soundman98 View Post
    ^

    for me, this makes capacitors a band-aid in car audio-- as in they fix things that have better ways of being corrected--like upgrading your power and ground connections, upgrading your battery(s). or upgrading your alternator. all of these things have the potential to correct for the same thing the capacitor appears to be doing, but allows for a much more stable power system overall.
    Well said, I would use it as a temporary diagnostic tool. If you DO use a Capacitor you also have to make sure you follow the directions that come with it as a capacitor can discharge all of its energy in an instant.

    In most cases you can not have too big of wires. Just make sure you use good quality cables. In a lot of cases a 4 gauge high quality cable for your car will be MUCH smaller in diameter than a low cost, low quality cable and will likely last longer as well.

  7. #7
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    Quote Originally Posted by OldSpark View Post
    What do you want to do - prevent the lights dimming, or prevent the amp's output dipping?
    IMO without an answer, it's pointless arguing for or against caps - or any particular solution.
    As I've written countless times, a 1.2AH battery will outlast a 1F or 10F cap. As far as audio systems are concerned, their only use is to protect AGM batteries for big systems with a few kW output. As redheadedrod
    alludes, caps are a "short burst" or "discharged in an instant".
    But to prevent headlights dimming, place the cap near the headlights, not the amp.


    The general solution order for these types of issue are:
    - the big 3 or 4 - ie, copious or redundant grounds; good alt and battery power feeds;
    - alternator sized to handle peak else average loading;
    - st'd wet cell battery for cranking & isolatable remote battery/s as required (AGM if internal), else whatever compromise battery system.
    - caps to protect AGMs from high current busrts, or for smoothing when batteries cannot be used or are otherwise undesirable.

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    Wow, you guys rock. I need to spread some reputation when I have a chance to process everything.

    The charging issue, I am embarrassed to say looks like big3. I never bothered to check, but it looks like 8awg stock from alternator and to ground. I ran 2/0 to the second battery, 0 to ground it--should have addressed the first battery cabling right away. Ignorance is bliss.
    But I'm learning a lot about troubleshooting this stuff... and who knows, there could be more going on then just that 8awg.
    Also, one of the battery terminal leads melted onto the terminal so I guess I'll have to break out a pry bar, chisel or rotary disc to cut it off.

    I'm still not sure how to best proceed with the low audio on the stock bose though.
    a little caveat:
    Code:
    I can boost the volume output past 100% using vlc, but some tracks get distortion from that.  It's odd because I can boost vlc to 150% and have sound card volume set at ~10% and even with audio low u can hear the distortion.  I guess it's just from the gain already being set too high in the source audio?
    I can't find any car audio pre-amps using google. Unless all the EQ's it spits back are preamps--though I assumed they did not boost source volume, but adjust output gain to different channels. Is that somewhat on track?
    Either way I'm not sure how much I want to fool with it.

    I'm almost ready to just rip it out and put in all aftermarket because I know that will work and it will save time, but for ~500$ it doesn't come cheap.
    Any creative solutions? (save cutting the stock radio connector off too tie into the bose audio cables directly)
    Thanks again for all the info. It's very helpful!

  9. #9
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    for preamps, how much are you looking to spend and how much space do you have to install them?


    and don't give up now! you're nearly there! you don't know how many times i nearly smashed my setup with a hammer for similar reasons while trying to set it up...

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    Quote Originally Posted by soundman98 View Post
    for preamps, how much are you looking to spend and how much space do you have to install them?


    and don't give up now! you're nearly there! you don't know how many times i nearly smashed my setup with a hammer for similar reasons while trying to set it up...
    Ideally, I would put a preamp in the dash however I'm happy to run cables where ever necessary (Under center consol or behind the backseat if I must). There isn't a ton of room behind the backseat but I managed to fit a small fosgate amp there.

    After giving it more thought I am leaning towards pulling the stock audio and going with aftermarket as the long term solution. It will probably end up saving some hassle and sound better overall.
    Any suggestions on smaller (physical size) amplifiers + front, rear door speakers?

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