Recording with Dolby C

There is a thread concerning Dolby B and C, but I couldn’t find the answers there.
I’ve got a lot of cassette tapes recorded with Dolby B and C. Although Dolby B is more or less audible when played back without Dolby B, Dolby C definitely isn’t (read Wikipedia about it if an explanation is needed).
Tapes are degrading in time depending on the quality of the tapes, but even more important: the quality of environment in which they are kept. So I’m not the only one wanting to preserve them by converting them to digital files.
The first step is to record them and that is easily done with Audacity. The problem is that I have most of my tapes recorded with either Dolby B or Dolby C. Both are better in quality when played back with the same system, because it reverses the process. Now there are two possibilities in my humble opinion.

  1. Audacity should have a codec or something with the Dolby B and C processes which can be utilized during or after the recording. I’ve asked Dolby Labs for such thing. But if they refuse, is there somebody in the public domain who can do it?
  2. Audacity could be tweaked to look like the reversed Dolby B or C process. Helas! I can not. Who can?


Now there are two possibilities

One. Play the tapes on a Dolby player. There is no post processing Dolby that I know of and the Dolby people are alive and well (Dolby was used in analog stereo television broadcasting just before digital). They are fiercely protective of their technology.

A -was 3-band processing used in analog studio audio recording.
B -was a simpler version affecting high-band (hiss) only for consumer recorders.
C -was a nuclear, weapons-grade B. You can’t listen to a C tape without processing. The pumping and compression is objectionable.

You might still be able to get a Dolby player on eBay or Craig’s List. I found a Sony TC-K611S unit that will do B, C, and S (I don’t know, either).


Thanks for your answer.
I know Dolby people are very protective and I know they still play their bit.
But I thought, “why not”, if public domain developers can build OpenOffice almost just like Microsoft Office, maybe there are enthousiastic developers who can build a Dolby B/C decoder for Audicity.
But helas, as you make clear: there is no development like this.


eBay has several Dolby B/C decks listed - I searched on “dolby c cassette deck”

There’s a couple of nice looking NADs for less than a hundred bucks an Nakamichi BX-1 (the model I have and love) for $125

Happy hunting

And you can always sell it on after you’ve finished your transcriptions …


Thinking back, I’ve never seen Dolby software from anybody. Dolby is a device or hardware, so it’s not like loading the software and doing a recursive analysis while you’re having a cup of tea. You have to get the device and using hardware generators, scopes, pulsers and sweepers, try and divine what they’re doing, and then generate software that does the same thing. Far different from being a ripper jockey.

By the way, it’s no mystery how it works, it’s a symmetrical dynamic compressor. It compresses loud sounds and expands low ones at the beginning and then puts it all back to normal at the end. Dolby was the first one to make a commercial gadget that you couldn’t hear working. Shoot a show in Dolby and 10dB of tape noise vanished. Full Stop. No other noticeable effects. Some say it made commercial tape overdubbing possible. You can’t do tape overdubbing without Dolby. Tape noise goes up as the square root of the hoo-haa every time you add a track.

You may notice that B tapes sound brighter than normal and you can apply the equalizer to bring down the brightness a bit, ignore the other effects and call it good, but you can’t do that to C.


I have a Panasonic RQ-V162 portable cassette player and AM/FM radio with Normal/CrO2 and Dolby on/off. The whole thing hides behind my hand.


[quote=“kozikowski”] … No other noticeable effects. [quote]

Except that they were noticeable, especially with the best commercially available tapes. When I bought my Nak (Pre-configured for TDK-SA) I did careful listening tests with Dolby-C and -B. I hated -C it made the music sound lifeless - and -B didn’t sound any better than no Dolby. So I recorded all my tapes with no Dolby. The only times I used the Dolby settings were when I played a commercially recorded tape or one I borrowed from a friend that was Dolby encoded :sunglasses: :slight_smile: