Noise Suppression Help

Discussion in 'General Electronics Chat' started by Saintwithatie, Oct 2, 2012.

  1. Saintwithatie

    Thread Starter New Member

    Oct 2, 2012
    I recently designed a lighting and audio system for a bicycle powered by a 12V Lead Acid Battery. The problem I have is that the (cheap) amplifier picks up every little voltage transient caused by the other loads.

    After doing research and browsing the forums, I'm guessing that I'll need some form of transient suppression, probably capacitors. I just need help in determining the capacitance, voltage, and placement of the capacitors.

    Last edited: Oct 2, 2012
  2. crutschow


    Mar 14, 2008
    You could try a large capacitor directly across the amplifer from power to ground with as short leads as possible. Try about a thousand μF, 16V or greater to start.

    If that doesn't work you might also try adding an inductor in series with the power to the amp, such as this in addition to the capacitor (series inductor, then capacitor).
  3. bountyhunter

    Well-Known Member

    Sep 7, 2009
    Definitely use some series inductance and as huge a cap as you can get. I don't think 1000uF is enough, I'd say more like 10k uF, but try it and see.

    NOTE: another source of noise is the ground lead. make sure the amp has a heavy ground lead that goes directly back to the negative post of the battery.
  4. Audioguru


    Dec 20, 2007
    How can your audio amplifier produce a whopping 100W when its power supply voltage is only about 13.2V? A single-ended amplifier will clip at only 2W into 8 ohms or 3.6W into 4 ohms. If the amplifier is bridged then it clips at about 12W into 4 ohms.

    I think your amplifier is rated at 100 Whats, not 100 Watts. Maybe it is stereo with 50 Whats per channel.
  5. Saintwithatie

    Thread Starter New Member

    Oct 2, 2012
    Yes, it is 50W per channel, but the whole shebang only uses 6 watts at a comfortable listening level.

    I performed this test:

    I disconnected everything from the battery, then I only hooked up the amplifier directly to the battery terminals. No audio playing, volume set to half.

    Now, my tail light has 2 modes: strobe and solid. I set it to strobe and touched its leads to the battery terminals. When I did this, I could hear a oscillating hum corresponding to the pattern of the strobe being amplified through the speakers:

    Keep in mind that the leads from both the tail light and the amp are stock (about 20 and 18 gauge, respectively) and are each less than a foot long.

    I have a a noise filter with 16 gauge leads that I disassembled to verify its contents being an inductance coil and a 16V 1000 uF cap. I tried putting it in-line with 1.) the strobe light, 2.) the amp, and 3.) both. In all placements it did nothing.