I’ve tested two different brands of microSD cards in my ER-301 both with a fresh formatting under firmware v0.3.13. Here are the results:
PNY Pro Elite 32GB U3 Class 10 rated at 95MB/s Read and 90MB/s Write
Actual results: 11.72MB/s Read and 5.19MB/s Write
SanDisk Extreme 32GB U3 Class 10 rated at 95MB/s Read and 90MB/s Write
Actual results: 16.31MB/s Read and 7.33MB/s Write
Point here is that while the specs are identical the results are significantly different and can impact how effective your ER-301 is going to be while recording at the highest rates. Also, having a nearly 30% faster read time is helpful for workflow efficiency.
I’d like to ask others who have recently formatted their microSD card with at least version 0.3.08 firmware and above to post the results of their card.
my numbers are below, but i notice they slightly shift with each measurement. after using SD cards for many years, i don’t trust anything aside from the best Sandisk card I can find for the given device specs and format.
SanDisk Extreme Pro U3 - 32GB before card format:
FYI, in this case, most of the variability is due to FAT maintenance which depends heavily on the card’s ability to perform random (as opposed to sequential) reads & writes as well as the distribution of free clusters on your card.
Another important point is that the the SD card communication bus for the ER-301 is 4-bits wide and runs at 50MHz. This is a maximum theoretical throughput of 25MB/s which puts it at slightly below USB2.0 rates (35MB/s). So you won’t really be benefiting by any sequential read/write speeds above approximately 50MB/s. At that point, you will get more benefit by finding a card that excels at randomized reads & writes (i.e. the 4KiB measurements in CrystalDiskMark). Good luck with that though because card manufacturers seem to never publish that information. Tom’s Hardware does have some benchmarks though:
Notice in particular how a top-of-the-line card with a measured sequential write speed of over 60MB/s will have a random write speed of less than 2MB/s. This means that real-life write speeds to the non-sequential clusters of a FAT-based file system will fluctuate between these two speeds depending on a number of factors that change over time.
Regarding the link @odevices posted for a recommended microSD card, when you click the link it displays a 128GB card - DO NOT buy a card larger than 32GB. There are three choices of card size on that page, choose the 32GB version ONLY!