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car amplifier for battery powered rig

Discussion in 'Amps and Cabs [BG]' started by cultrvultr, Oct 12, 2017.


  1. cultrvultr

    cultrvultr Supporting Member

    Jun 16, 2008
    Oakland, California
    I see tons of posts about battery-powered rigs here. Has anyone tried using an automotive amplifier? This one looks cool: NVX MVPA4 Micro-V 400W RMS 4-Channel Car Amp with Small Footprint

    It seems like a pedal preamp, car amp and small USB battery pack with a 12V step up cable would make for a decent portable rig that would fit on a nano pedalboard. Pair with a small cab and it could be a great little setup.

    Any reason this isn't more common?
     
  2. two fingers

    two fingers Opinionated blowhard. But not mad about it. Gold Supporting Member

    Feb 7, 2005
    Eastern NC USA
    Things to consider....

    Input impedance - The output of the preamp and input of the amp must be compatible.

    Power - You can't run a 400W amp at full blast for very long on one car battery. Try running your car stereo very loud without the car running and see how long it lasts. I did it recently waxing my truck and running the stereo with a sub pretty loud. I got about 45 minutes in and the battery died.

    Practicality- With all kinds of car amps being very common and for sale cheap on every Craigslist on Earth, if it worked, we would know it by now.
     
    Old Garage-Bander likes this.
  3. eJake

    eJake

    May 22, 2011
    New Orleans
    As I understand it you want an RV battery not a car battery. And an inverter.
     
    InhumanResource likes this.
  4. Ampslut

    Ampslut

    May 15, 2017
    Killed_by_Death likes this.
  5. waveman

    waveman Supporting Member

    Sep 25, 2008
    You would be better off with a GK-MB200 + 150 watt inverter + 105AH Marine Battery from Academy Sports. The amp draw on the GK will be very small. The size of the inverter matters, because larger ones will have more no-load continuous draw.
     
  6. cultrvultr

    cultrvultr Supporting Member

    Jun 16, 2008
    Oakland, California
    Not interested in powering a regular AC-powered bass amp meant for wall power with a giant battery and inverter.

    Why not use the auto amplifiers already designed to use lower 12v voltage DC and battery power? Stay DC-to-DC and lower voltage

    Most pedal preamps already run off battery or something like a Volto, so it’s really just a matter of switching out the amplifier right?
     
  7. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    If only it were that simple. Sadly the laws of physics tend to be immutable. ;(
     
    packhowitzer and two fingers like this.
  8. SaucyJackBass

    SaucyJackBass Supporting Member

    May 6, 2009
    Pignose battery operated amp is the bomb. I use it for campfire jams all the time.
     
    Killed_by_Death likes this.
  9. Killed_by_Death

    Killed_by_Death Snaggletooth

    Jan 2, 2015
    heart of darkness
    That's only 50 watts per channel at 4 Ohms:

    MVPA4: 4-Channel Compact Car Amplifier, 400W RMS

    So, if you go near max volume, you're talking 4 Amperes of current to the amplifier.

    If you're running two channels, double that.

    Your options for powering it are a UPS battery or a automotive battery.

    UPS batteries are cheaper, but with less output. (single digit Amps/Hour)

    Automotive (or boat) batteries are much higher output, but also larger & heavier.

    Start doing the calculations based on the power you'll need & the amp/hour of the battery & you'll most likely abandon this project.
     
  10. cultrvultr

    cultrvultr Supporting Member

    Jun 16, 2008
    Oakland, California
    Thanks @Killed_by_Death , what about a 50000mAh/185Wh battery with a 20V/3A output like this:
    http://a.co/aORcyqW

    Wouldn't you be able to get like 2 hours of playtime at least?
     
  11. Killed_by_Death

    Killed_by_Death Snaggletooth

    Jan 2, 2015
    heart of darkness
    read the fine print:

    "It Has 6 Output Ports. One 20V/3A for Laptops, one 12V/2.5A"

    A 2.5 Ampere port is not enough to be safe. If you turn the volume up you risk going over 2.5 Amperes & then that thing is going to blow up or start melting wires.
     
  12. two fingers

    two fingers Opinionated blowhard. But not mad about it. Gold Supporting Member

    Feb 7, 2005
    Eastern NC USA
    Have you settled the input/output impedance issues yet? Did you find out the input impedance of the car amp? If it doesn't match the output of the preamp you are in a much more complicated situation.

    Here's some light reading. You can't just plug anything into anything else. You can't just plug a bass into a stereo, a mic into a car radio, any power amp into any speaker, etc. There's math and engineering involved.

    http://www.electronics-tutorials.ws/amplifier/input-impedance-of-an-amplifier.html

    I promise you, if it were practical, this crowd would have done it. I promise you, you aren't the first to scratch your head over it.

    Wouldn't it be super cool a light to be able to run a preamp pedal into a tiny car amp into a neo driver cab? Of course. Heck, you could even bolt it all together to a cart. But there are issues to consider other than just will it all fit on the cab.
     
  13. brianrost

    brianrost Gold Supporting Member

    Apr 26, 2000
    Boston, Taxachusetts
    Passinwind likes this.
  14. Killed_by_Death

    Killed_by_Death Snaggletooth

    Jan 2, 2015
    heart of darkness
    Good point about the input impedance. I've got no idea what sort of impedance a automobile's head unit would be using.

    I did notice that amp has a bridged output that does 175 watts x 2 channels.
     
  15. AcridSaint

    AcridSaint ベーシスト Supporting Member

    Jan 30, 2012
    Raleigh
    I don't play well.
    I saw a video of a street performer doing something similar with bass, but he was running into a car stereo deck. If you have a headphone amp, Pandora, or similar, you can go into the aux-in on a deck. With the amp, you could probably get around this by using a cheap EQ that has an aux/3.5mm input.
     
  16. if you want any sort of real volume, you need a very large & heavy battery like the ones posted. You can use a regular car battery and a power inverter to run a combo amp or something.
    I still prefer the little red honda generator solution over any battery powered options.
     
  17. cultrvultr

    cultrvultr Supporting Member

    Jun 16, 2008
    Oakland, California
    Thanks for the replies guys. Not worried about input impedance since all of the car audio products work at line level and most preamp pedals will send line level. I realize there is a wide range of definitions of "Line Level" - even when it should mean +4dbu, but pretty confident that it would not be an issue. Make up gain and padding available to deal with any input/output sensitivity issues.

    I will say I have run some of the cheap T-Amps with a much smaller USB battery pack before. A 20W T-amp like the Lepai 2020 will run at 12/2A quite happily on a 10,000MAH USB battery for some time. Plug it into any 8ohm cab and it seems to work quite well.
     
  18. Killed_by_Death

    Killed_by_Death Snaggletooth

    Jan 2, 2015
    heart of darkness
    Wait,
    Line Level infers a range of impedance?
     
  19. cultrvultr

    cultrvultr Supporting Member

    Jun 16, 2008
    Oakland, California
    no, but I don't think there is an impedance mismatch between the preamplifier output and the amplifier input. The amplifier/battery issue seems to be the real question.
     
  20. StatesideRambler

    StatesideRambler

    Jul 1, 2015
    I've considered using car amps for podium PA, the goal being a simple, low cost PA for lecturers, but I haven't looked into it yet. Time is always at a premium. I am curious if car amps can handle the dynamic range that's presented by a musical instrument. Instruments have a much wider dynamic range than radio/satellite tuners or MP3 players. You might be forced to use a compressor or accept clipping of your signal.