Audio cassette to CD?!
It's amazing the amount of information packed into any analogue storage medium, even one like the 'lowly' audio cassette.
Of course, it needs to be a half decent recording job in the first place.
Of course, there is the inevitable issue of tape hiss. This can be handled with mastering software like Voxengo's Redunoise, Sonnox' DeNoiser, and the Waves X-Noise and Z-Noise plugins.
Many older audio cassettes may have lost much of their high frequency information which is where Dolby did most of it's work on. If I'm unsure about applying Dolby B on an audio cassette marked as being encoded that way, I'll make two passes if there's time: one with Dolby B engaged and one without, and decide later.
But there are times when it's pointless to engage Dolby at all because of excessive high end loss.
Either way, some restorative EQ is going to come in to play usually with software like Harbal. At times, UAD's Pultec emulation works wonders!
Speaking of Dolby...
...that will crop up very frequently with audio cassette to CD transfers, and that is the question of left-right balance of the stereo image.
Because of the thin-ness and narrow-ness of cassette tape, the left and right channels often are not recorded on with equal levels. Since Dolby is a two stage encode/decode process and 'assumes' it is printing on to tape at equal levels, at playback time there are going to be additional high frequency loss problems when Dolby 'over-decodes' the channel with lower levels!!
The solution is with a professional outboard Dolby B decoder – an increasingly rare item. This would give the ability to separately adjust the playback decoding levels so that both channels get restored properly.
Of course, if Dolby could produce a decoder type plug-in(!) that can handle independently decoding channels, a lot more projects would be restored efficiently!
Dolby and noise reduction aside, I feel the most crucial element when transferring an audio cassette to CD, - and I've already mentioned this – is the stereo image.
Get that right and half the problems are solved. Remember, we're trying to re-create a master).
It's about azimuth.
Put more simply, the left and right channels must play back in proper time alignment.
We're talking fractions of micro-seconds, folks!
The start of this problem can be caused by:
Rather than constantly fiddle with mechanical cassette head alignment, my preferred solution is in post production with Voxengo's Sample Delay.
Once finished, azimuth correction alone, done correctly, really increases the “Wow!” factor from my clients.
From here on, I'll correct the left/right balance, possibly adjust the image width, EQ and so on. Some upward multi-band expansion can work very nicely to bring back life to cassette transfers.
It's a sense of great personal satisfaction for me to watch a client go from despair to un-controllable 'enthusiasm' when recovering a lost masterpiece!
When transferring an audio cassette to CD, that little effort is well worth it!
Proud to be affiliated with these organizations: