Dolby S – S is for surprise

After having watched Techmoan’s Cassette video I couldn’t resist and bought myself a cassette deck with Dolby S. In my case it was a Yamaha KX-580.

How I used to use cassettes

Before I bought a Minidisc recorder in 1996 or 1997 I used Metal cassettes, recorded them on my Telefunken twin deck and played them on the Alpine stereo in my car. The sound was usually fine, except the very annoying tape hiss you got all the time.

First impressions

My first impression with the Dolby S deck: Great! Much less hiss than I remember, despite only using a ‘Normal’ cassette. It was a Maxell UR 90 tape I had lying around, still shrink-wrapped. I think my wife got it when her previous university phased out tape recorders. Reasons for the better sound compared to what I remembered? I guess I either remember there being more hiss than there actually was, my ears got worse or my Telefunken deck or Alpine stereo had a problem – or maybe it’s a combination of all of these reasons.

Dolby S

I was however brought back down to earth when I tried did a comparison and tried out Dolby S.

I was expecting a lot – having watched Techmoan’s video my expectations were pretty high, but then there were also other documents, like this PDF, which doesn’t have an author, but seemed pretty well written and said things like:

“We have found that, at the highest playback levels likely to be encountered in the home, sophisticated listeners subjected to A/B comparisons of CDs and Dolby S-type cassettes are unable to identify which is which with any regularity.”

or

Dolby S-type Cassette Decks provide performance comparable to that of a Compact Disc, utilizing standard (Type I) blank cassette tapes.

There’s also this diagram in my cassette decks’ manual:

responce
from the Yamaha KX-580 manual

It also gives the impression that Dolby S will outperform Dolby C in terms of noise reduction.

Reality / the test

What I got was very different though. For my test I recorded two songs from YouTube’s audio library on a new Maxell UR 90 cassette: Far Away by MK2 and I’m Fly by Gunnar Olsen. Both were burned on a CD-R and played back on my SEG DVD player (also available as a Yamakawa, these were affordable multi region DVD players from the 1990s that actually use an ATA DVD drive). I recorded the same two songs without Dolby, with Dolby B, then Dolby C, then Dolby S. I then played them back using the same type of Dolby used for recording, i.e. the Dolby B recording was played back using Dolby B, etc. and recorded the output using 96 kHz and 24 bit.

To my surprise the noise floor of the Dolby S recording was higher than that of the Dolby B recording. If you adjust the input levels for these songs, maybe slightly conservative, then the noise floor level without noise reduction is -48 dB, with Dolby B it’s -57 dB, with Dolby C -59 dB and with Dolby S -54 dB.

The cassette deck seemed to be in great condition, so I wonder whether something is broken or whether this is normal behaviour. It would be great to hear from you if you have a Dolby S deck.

noisefloor
Noise floor comparison

I put the recordings on YouTube, if you want to listen for yourself, but I should add that even though I recorded them with 96 kHz and 24 bit I had to use AAC with 48kHz and 320 kbps for encoding the video. I don’t know whether YouTube will then reencode the sound again. I guess what quality is sent to your machine will depend on the quality of your internet connection, so what you hear is only to some extent representative.

Here are the videos

No noise reduction

Dolby B

Dolby C

Dolby S

 


Techmoan also mentioned cassettes in his blog.

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One thought on “Dolby S – S is for surprise

  1. Tape quality is probably the biggest factor. I personally can’t tell any of the Dolby cassette formats apart. When I do it’s probably a placebo because I’ve been told S sounds a lot better. My first deck was a Technics with Dolby B in 1979. I think the biggest improvement in cassette sound was Dolby HX, S was only slightly better.

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