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Old 15th August 2020
Gear Head

Hi Lars! As someone who has digitized hundreds of both mini & micro cassettes, there's an reasonable expectation of limited fidelity with these, so I wouldn't spend much time sweating over noise reduction for the entire collection (unless you enjoy doing it of course!). I use RX7 Advanced myself, but never have been fully satisfied with any of the auto or single-action dynamic plugins. For real effective results, it usually requires some experimenting and adjusting for each tape (and for each side of each tape).

Being hand-held devices, micro cassettes typically have some steady, narrow-band, electro-mechanical noise which can be removed most effectively with a single-band dehum at each precise frequency. There are harmonics of these noises, but it's best to do them one by one if possible.

Keep in mind, some devices had low-voltage detection and some didn't, meaning, if the batteries got low, the tape recorder got slower and slower. When you transfer back with new batteries (or a hardwired AC plug, which is highly recommended), it plays back faster and faster! This effectively shifts all of your eq/hum/noise problems up several frequencies. This can all happen over the coarse of a single side of tape, which is why noise reduction and eq efforts on micro cassettes are sometimes done in vain.

If you have the drive space, consider saving both the original transfer (Preservation Master) and then make your noise reduction edits to a separate file (Modified Master). This way, you'll always have the unmodified, original source copy to work with down the road when some amazing new plugin comes out! Most micro & mini cassettes are mono, so transferring and saving an extra file doesn't take a huge data footprint.

If this is for a client, and you do modify the original, consider documenting the technique you used and enter the data into an inventory spreadsheet or the CodingHistory of the BWF BEXT chunk. Your archivist will love you!