Advent 100A Dolby B noise reduction.

adrianywu said:

Since this thread has been resurrected, I just want to share my recent experience with the Dolby B tapes. I have some Dolby B tapes from Stereotape, Ampex (DGG recordings) and Barclay-Crocker. Interestingly, most of the squeaky tapes I have encountered are Dolby B encoded (Ampex and Stereotape). The older tapes from the 1960s do not suffer from this problem, so it could be due to a change in the tape formulation during the 1970s. Liquid silicone took care of the problem. I also find that the Dolby tapes are more prone to crosstalk, probably because they were transferred at a higher level. One tape of Pollini Chopin Etudes (DGG) made by Ampex has obvious pumping during the quiet bits, which is frustrating because the louder pieces sound great. I am using the Nakamichi NR-200, and some Barclay Crocker tapes can sound excellent. Overall though, I find it is unnecessary to use Dolby for these 4 track tapes. I have some non-Dolby tapes that sound astoundingly good, with very little noise and excellent dynamics.

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murugan19 said:

Hi adrainywu,
Unfortunately, I have a couple of Barklay Crocker 4 ch tapes, and although they sound astounding (compared to their age), I do need to use Dolby B to eliminate the tape hiss on my Dokorder 8140. Maybe I'm doing something wrong?
I don't have any crosstalk (maybe because I have my headstack aligned) but the hiss is apparent during the "quiet" parts of the symphonies.
Sincerely,
John Graham

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adrianywu said:

Dolby NR will only eliminate the hiss coming from the tape being played realtime. It will not eliminate the hiss inherent in the recording. If the source tape has hiss, which is typical of recordings from Mercury, for example, Dolby will not fix it. You would need a single ended noise reduction system such as the Behringer SNR2000, which works very well in these situations.

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tapepath said:

Hello,
Unfortunately the HiFi Engine doesn't have the owner's manual for the 100A, only the service manual. Here is a link to Keith Snook's excellent web site with the complete, three part, article in Wireless World explaining the operation (including calibration) of the Dolby B noise reduction system. Dolby Laboratory was fairly controlling in how each licensed manufacturer would develop their commercial units and how they would function. In other words, if you understand how one company's Dolby B was setup then the method for everyone's else's followed the same arrangement. Anyway here is the link:

https://keith-snook.info/wireless-world-articles/Wireless-World-1975/Wireless%20World%20Dolby%20noise%20reducer.pdf

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