Transitioning from D Cell Batteries to 9 Volt

I am not so sure you can do this since the current draw may be too high for a 9 volt, if it does work you would likely only get a few minutes of working time per battery. Inside a 9 volt battery are actually six smaller AAAA batteries. If your boom box runs on six D cells then you could connect a 9 volt to the same terminals that the first and last D cells went to. If your boom box is meant to run on less than six D cells then you risk burning it out with a 9 volt. If you don't know much about electronics (which is likely the case) then I wouldn't try it unless you don't mind burning out your boom box and destroying the 9 volt. If your looking to reduce the weight, you could make some sort of adaptor to use an equal number of AA's instead of D's but once again the batteries won't last long.

THANK-YOU VERY MUCH

And, if you already have the 9-V, don't carry it in your pocket with change. Ouch!

I use an adapter for my bike lights, so I can use AA NIMH rechargables instead of standard D cells. The latest 2500mAH AA cells last longer than standard D batteries between charges.