SD Card Performance

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:
15.84MB/s read
10.72MB/s write

after format
16.45MB/s read
9.19MB/s write

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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:,3477.html

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.


very interesting! did not know that about the random write speed.

um… can you just simply tell us which is the best card to use in the er-301 then brian ?

sorry, i understand it may change with different firmwares or something(?), but would be nice to just have simple answer if possible…

My recommendation is that if you are not having issues with the card provided with your ER-301, then I would definitely not worry about it. :wink:

As long as you have a class 10 card from a reputable manufacturer then you are not going to get much improvement(*) by buying that $50 SD card.

If you absolutely need a recommendation: Here is one.

(*) Maybe 10% or 15% improvement? Hard to say.

BTW, if this discussion stresses you out, I would just refrain from reading into it too much. Just some friendly tech nerds discussing tiny details. Kind of like those overclocking forums. :laughing:


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!

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Good advice.

But if you have the time and money to experiment with other card sizes, go for it. :see_no_evil::hear_no_evil::speak_no_evil:

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I’m having some problems with the provided MicroSD card – even after reformatting and copying back the stuff I had on there, I can’t record even two tracks using the 6-track recorder.

Does anyone have recommendations concerning cards that should work?

First of all you are formatting with the built-in ER-301 utility right?

I use SanDisk Extreme 32GB cards and while I don’t really have any problems with it, I do find that I have to reformat it from time to time.

Yes, using the 301’s format utility.

I have quite a bit of files there – a large collection of single cycle waves, for instance, so I’m thinking that could be the cause… Would like to have them, though.

Wonder if it would help to dedicate a card to recording? And have one for everything else…

I’m still using the original card that came with mine. Have never had to reformat. My DAW is my normal output device though, so most longer recordings are done there.

Hmm, it’s interesting you haven’t had to reformat. Maybe it is worth trying another card.

Usually the buffer underrums happen in ~5 seconds. The fact that they often happen have kept me from really using the recorder, as you can’t rely on it to work.

I think it is definitely worth it. It sounds like your SD card’s performance has deteriorated. You should never get underruns on a peformant SD card of class 10 or better.

By the way, how many files are we talking about?

Okay, I’ll try it and report back!

Its, oh, some 63 000 files :roll_eyes:. Mostly single cycles, so that can be cut down if it seems like that’s the culprit.

Well let’s just say I have not tested card performance in the presence of that many files. Although theoretically it shouldn’t matter once we know that card is not fragmented. :thinking:

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Yeah, I know it’s fairly extreme… We’ll consider this a stress test :slight_smile: We’ll see how it goes!

Has anyone confirmed if more than 32gb can be utilized in the er-301? I am trying to max baby out with long samples and the like.

I have heard that others have used larger cards with no issues, I have not myself though, still using the one that came with it.

11 card players long > 7 mins 48/32 audio files, cpu around 75% crackling start.
do i need a faster sd or that’s the limit?