The OSCAR Stand-Alone MP3 Player described in last year’s September issue appears to be very popular with our readers. So popular in fact, that a large number would also like to use it in their car, boat or caravan. Using the DC/DC-converter described here will make that easier, from the power supply perspective at least.We really have ourselves to blame for this. In the first instalment of the series of articles describing the OSCAR, we carelessly let it slip that it would be advisable to use a special DC/DC converter to power this MP3-CD-player for mobile use. As a result, one can promptly expect the question ‘when are you publishing such a converter?’ Consequently, we immediately got to work and developed one. The end result is described below. It turns out that the required electronics is actually quite reasonable.