Wilsons Sandbox

I build an amplifier for the KLR last night so the problem of low helmet speaker volume seems to be solved. The issue was that earplugs are needed on the highway or the wind and other noise levels make my ears ring. Any of the ear bud type speakers don't work for me because they often don't exclude the wind noise enough, are hard to keep in place (especially when putting on the helmet) and can make my ear canal sore after several hours. Chatterbox make a neat little AM-FM radio which is smaller than the first two sections of my index and second fingers. The kit comes with ear buds, helmet speakers & Velcro, and a curly cable which also doubles as an antenna for the radio. AM is hopeless but FM is clear, steady and reasonably loud- good around town. Much searching failed to locate a suitable amplifier in the three cities near us so I gave up and made one up. Rather than build an amp from scratch it was easier and cheaper to scavenge an old pair of computer speakers. Look for a set which operate on 12 volts or close so a power supply isn't needed. Pull the one with the controls apart and the circuit board is maybe 2" x 3 1/2". Clip off the speaker leads and look for the two resistors which are in series with the headphone jack. These resistors drop the output to the headphones so they need to be jumpered by soldering a bit of wire across each one. This can be confirmed by plugging speakers into the headphone jack and jumpering the resistors, making volume jump up. A small plastic food box with locking lid was obtained to hold the board and holes were drilled for the wires. A spot of silicone RTV sealed the holes and a 2.5mm male plug was soldered to the power lead. A female 2.5mm was wired to the power lead on the back of the bike's dash. a long audio lead with stereo jack was already part of the speaker set so that is simply plugged into the CD player or Chatterbox as desired. The volume on the amplifier is set at maximum since the CD/Chatterbox volume control will provide enough control. An old set of head phones were scavenged to install into my MX helmet but a better set my be needed. Time will tell as I usually don't wear ear plugs in the MX helmet. The only area which seems to be able to hold the amp is behind the radiator overflow tank so the amp will ride in the tank bag for now. I may simply pot the amp with rubber and mount it somewhere sans box but not for now. Hope this is helpful to someone else. Norm __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com