While microSD cards inside a micro-to-full-size SD card adapter can be used in some of our recorders, such as the SM4 and SM Mini families, we do not recommend them. The use of the adapter adds a potential point of failure between the recorder and the SD card itself. Wide fluctuations in temperature or jostling the recorder might momentarily break the connection to the SD card which could cause card corruption and data loss. This is more likely when using a microSD card inside an adapter than with a full-size SD card.
Unlike the other Song Meter models, the SM Micro recorder is built with a slot that fits a microSD card directly; therefore it is okay to use a microSD card in a SM Micro.