UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Different Dolby B / C Calibration Standards

paulsherwin · 3rd May 2019, 8:55 pm

Ted:

The problem is the differing sensitivity of the different tape stock. BASF chrome has very low noise levels but also low MOLs. A correctly recorded BASF chrome cassette will play back 3-6dB lower than a good pseudochrome. It's quite easy to see this effect when playing back commercial cassettes recorded on different stock. There is no practical way for tape duplicators to counteract this effect. The playback machine can be Dolby calibrated for high or low MOLs but not both.

I'm not picking on BASF here - it's just that they were the biggest manufacturers of this sort of tape, and marketed it aggressively to both the commercial and domestic markets.

Of course, there are lots of other reasons why a musicassette can sound lousy. They got a lot better towards the end of the cassette era as the duplicators switched to decent ferric stock and introduced HX-Pro style variable bias.

3rd May 2019, 8:55 pm	#8
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,939	Re: Different Dolby B / C Calibration Standards Ted: The problem is the differing sensitivity of the different tape stock. BASF chrome has very low noise levels but also low MOLs. A correctly recorded BASF chrome cassette will play back 3-6dB lower than a good pseudochrome. It's quite easy to see this effect when playing back commercial cassettes recorded on different stock. There is no practical way for tape duplicators to counteract this effect. The playback machine can be Dolby calibrated for high or low MOLs but not both. I'm not picking on BASF here - it's just that they were the biggest manufacturers of this sort of tape, and marketed it aggressively to both the commercial and domestic markets. Of course, there are lots of other reasons why a musicassette can sound lousy. They got a lot better towards the end of the cassette era as the duplicators switched to decent ferric stock and introduced HX-Pro style variable bias.