These series of quick notes are meant as stand alone tidbits of interesting data we find along while developing and polishing MDFourier. For the full documentation and the rest of the notes, please visit http://junkerhq.net/MDFourier.
Thank you for your interest in helping with the MDFourier project. You can read about our goals and results at the main site linked above, but if you are reading this we assume you already have some idea of what is going on.
We need lots of recordings from different systems in order to advance the current state and also to create a catalog for comparisons and reference.
Unfortunately, not all audio capture equipment is created equal, Don’t worry though, hardware we have already tested for this purpose is not that expensive–around 50 USD or less if you buy used–and even if you don’t want to spend money, recordings made with equipment that doesn’t have a flat frequency response are useful if you have several systems. With flat response equipment you can contribute to the catalog, and in other scenarios your recordings can be used between themselves or at least we can tell what is not reliable in them.
You can test your existing audio capture setup by playing back one of our recordings from a source and then recording with your audio capture setup.
Ideally, you can do this by using an external audio player with the file referenced in the downloads section 4, but you can also use the same computer as a source. Just remember to use an RCA cable plus any adapters needed to connect your output to your input so you can record the signal.
Another method would be to use a DVD player, Blu-ray player or any device with a USB input. Put the reference file on a burned CD or USB stick and rerecord the file via your chosen capture method. When you compare the resulting file to the original reference file in MDFourier, any differences calculated would be either your player or your capture card. In the best case scenario a wholly digital to digital path would be 100% transparent (no differences) and a chain with any analog components (though containing minor difference) would still be completely flat 20Hz - 20kHz. Completely flat is good enough!
You can provide us with such recording and we can help you evaluate how flat the response of your audio device is. If you want to do this yourself, we also have a small document detailing how to interpret the results: http://junkerhq.net/MDFourier/notes/MDF-Note02-AudioEquipment.pdf
The recommended testing file: http://junkerhq.net/MDFourier/files/A-MD1UTVA3-SCD1-A20113193-RCA-M192.flac.