Try this tip proposed in 2013 for the Sansa Clip+.
But there is a fix after all. It turns out that the volume is limited on the device if you set it to Europe when you turned it on the first time. This can be resolved by resetting it to factory settings, and this time choosing North America. The down side to that is that it seems to skip even numbered FM frequencies (jumping from 99.3 to 99.5 to 99.7 etc), but the stations I listen to are luckily on the odd numbers. There are other settings that you might be able to choose that could also sort the volume issue out too, but I tried North America, then went into the Volume settings and chose ‘High’. Bingo! It’s now loud enough
AND, see the advice from JK98 in this Forum concerning the Clip Jam
First of all, don’t set the region to Europe, even if you do live in Europe. Next under settings, system setting, volume, set to high. If europe is chosen as the region, then you don’t get the option to choose high. In the menu,
see if you can find reset settings. If that won’t let you reset the region, then download the latest firmware, and manually install it on the player. After that you should be able to set the region. I guess choose rest of the world for the region? If you choose the US as the region, then I think the FM tuner won’t work right.