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Thread: Is there always a hum in the audio when you use a regular psu w/an inverter?

  1. 01-05-2003, 12:39 AM #1
    wysiwyg
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    Is there always a hum in the audio when you use a regular psu w/an inverter?

    Is it possible to have this setup and not have a hum? Thats with a psu and inverter that would cost less than the cost of a dc/dc psu. I have purchased just about everything for my car mp3/dvd system but the power supply and am trying to decide which route to take. If you have a regular psu and an inverter and have no hum let me know what setup you have and how you eliminated the hum. I don't what any hum at all, is this realistic with any setup, dc/dc included?

    *edit BTW here is the psu i was looking at from PC Power & Cooling
    97 Mazda MX6 LS lowered with some Zoom Zoom, Alpine 7894, Via Epia M 9000, Western Digital 60 gig 7200rpm, 256 mb pc2100 ddr ram, 5" LCD, PC P&C PSU, Gyration Ultra cordless optical suite
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  2. 01-05-2003, 01:13 AM #2
    magnetik
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    Re: Is there always a hum in the audio when you use a regular psu w/an inverter?

    you really can search for thyis info....

    short answer - yes. can be done quite easily.... and I have achived this.


    1. proper grounding of computer, psu, auido equipment.
    2. good quality supply/power lines (NO cig lighter crap!) run a wire from the battery direct.
    3. good qual sound card
    4. remove filter components from PSU (documented on my website)

    check my (old) system at my website. I say old cause im about 30% thru buiding my new system with DC-DC....
    Project - GAME OVER :(
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  3. 01-05-2003, 01:46 AM #3
    bosstone74
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    VERY possible,

    ground the motherboard and the PSU....
    should be good after that!
    BossTone74
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  4. 01-05-2003, 02:03 AM #4
    wysiwyg
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    Thanks for the quick feedback. Magnetik you obviously know you stuff when it comes to electronics, I checked out your sight its pretty nice. Anyway I myself would not feel comfortable taking apart my PSU and pulling parts out of it for fear of zapping myself. I will take the rest of your advice though. I did search and have been researching this a little but still wanted to ask what I did before spend I around $100 on the power for my computer. I know its annoying but thanks for taking the time to answer.
    97 Mazda MX6 LS lowered with some Zoom Zoom, Alpine 7894, Via Epia M 9000, Western Digital 60 gig 7200rpm, 256 mb pc2100 ddr ram, 5" LCD, PC P&C PSU, Gyration Ultra cordless optical suite
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  5. 01-05-2003, 06:17 PM #5
    magnetik
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    not a problem.... glad to help
    Project - GAME OVER :(
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  6. 01-05-2003, 11:00 PM #6
    cproaudio
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    You guys are forgetting one of the most important part. The sinewave that the inverter puts out. If you can get a pure sinewave inverter (very expensive), chances for humming noise and engine noise will be very unlikely, even if you dont ground the motherboard. the outlet of your house is pure sinewave. If you power the computer using the home outlet and hook up the audio to your car, you'll notice that there's no hum or engine noise. Modified sinewave will get a little hum and engine noise. The inverter you want to stay away from is the squarewave inverters. Those are the worst inverters to get. When you read the inverter package, make sure it says "modified sinewave" You should get Opus DC PSU. I don't have any special wiring or filter for my system. I have no noise at all. Stay away from the sleekline DC PSU from power and cooling.
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  7. 01-05-2003, 11:42 PM #7
    Charliey
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    i dont know if youve read magnetiks website, but on it he has a mod for an atx power supply to take out the filters for the sine wave, so that they work better with power inverters.
    Project AutoBoxen: Coming along, almost ready to hook up in the car.
    Celeron 500, 192mb ram, 8gb hdd, other stuff.
    '91 Mazda 626: Its free, so ill use it.
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  8. 01-08-2003, 09:23 PM #8
    starfox
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    A pure sinewave inverter is nice, but there's a few problems with them too: prohibitive costs and low effiency... they also have a tendency to warm up really quickly as well.

    and aren't modified sinewave inverters pretty close to square wave inverters, with a few more harmonics to make it slightly more 'sine like'?

    If you do magnetik's PSU mod you're directly rectifying the output from the inverter (in most PSUs), so using a pure sine wave inverter isn't competely necessary... Many people here (myself included) don't find noise to be a problem after grounding and ensuring your wiring's done correctly!
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  9. 01-09-2003, 10:18 PM #9
    Defiler
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    Slapped one of These on my inverter and TOTALLY removed any hum or buzz I had.
    Aura MR62 (F and R)
    My Current MP3s
    IamDefiler.com
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  10. 01-10-2003, 12:53 AM #10
    Sir_Pyro
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    magnetik, you mention on your website that your mod the efficiency of the PSU. Do you have any actual measure (amps drawn by inverter before and after mod) of this or is it just speculation?
    Comp. Specs:Shuttle SS40G, Athlon XP 1700+, 256MB DDR, 40GB HD, Belkin Desktop 802.11b card (good range), SB 128 sound (onboard is a bit noisy), DVD ROM
    Toshiba 100CS laptop, P75 40mb ram, 550MB HD, Megahertz LAN/modem PC card, modified to run off 12VDC
    Other stuff:Generic USB hub & USB to serial adapters, BS2SX power control system w/battery buffer, Jazz 300W Inverter, FM Modulator, Palm Vx, & GPS

    Status: 80% complete (Almost done with the controle boxes)
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