Hello everybody,
I have been reflecting on differences between NAB and IEC equalisations, which are usually found on Revox and Studer tape recorders. My B77 MkII (9,5/19 cm/s) is NAB version. During my years at Radio Belgrade, which was using exclusively IEC tape equalisation, I had the opportunity to directly compare the two equalisations and to draw my own conclusion that IEC sounds better, more open, more airy and natural and less "compressed". These comparisons were made on 19 and 38 cm/s speeds on Studer A8xx recorders. Now, going back to my B77, I notice that the 9,5/19 cm/s IEC versions of recording and repro amplifiers do not exist in the service manual. I was told that the reason is that NAB and IEC equalisations for these speeds are the same. But then I looked at the table published by IASA (international Association of Sound and Audiovisual Archives) which states the following:
19 cm/s
IEC1 (1968 current standard) = DIN Studio (1965) = CCIR (1966): 70us
IEC2 (current standard) = NAB (1966) = DIN Home (1963): 3180us, 50us
9,5 cm/s
IEC2 (current standard) = NAB (1965): 3180us, 90us
The table clearly shows that IEC2 and NAB use the same time constants at both speeds.
The B77 manual mentions the following equalisation standards:
19 cm/s
NAB: 3180us, 50us
IEC: N/A
9,5 cm/s
NAB: 3180us, 90us
IEC: N/A
My question is: have IEC2 and NAB standards for both 9,5 and 19 cm/s become equal, so that it does not make any difference and that NAB designations for recording and playback amps could as well be named IEC?
You can see the whole table of equalisation standards here:
I have been reflecting on differences between NAB and IEC equalisations, which are usually found on Revox and Studer tape recorders. My B77 MkII (9,5/19 cm/s) is NAB version. During my years at Radio Belgrade, which was using exclusively IEC tape equalisation, I had the opportunity to directly compare the two equalisations and to draw my own conclusion that IEC sounds better, more open, more airy and natural and less "compressed". These comparisons were made on 19 and 38 cm/s speeds on Studer A8xx recorders. Now, going back to my B77, I notice that the 9,5/19 cm/s IEC versions of recording and repro amplifiers do not exist in the service manual. I was told that the reason is that NAB and IEC equalisations for these speeds are the same. But then I looked at the table published by IASA (international Association of Sound and Audiovisual Archives) which states the following:
19 cm/s
IEC1 (1968 current standard) = DIN Studio (1965) = CCIR (1966): 70us
IEC2 (current standard) = NAB (1966) = DIN Home (1963): 3180us, 50us
9,5 cm/s
IEC2 (current standard) = NAB (1965): 3180us, 90us
The table clearly shows that IEC2 and NAB use the same time constants at both speeds.
The B77 manual mentions the following equalisation standards:
19 cm/s
NAB: 3180us, 50us
IEC: N/A
9,5 cm/s
NAB: 3180us, 90us
IEC: N/A
My question is: have IEC2 and NAB standards for both 9,5 and 19 cm/s become equal, so that it does not make any difference and that NAB designations for recording and playback amps could as well be named IEC?
You can see the whole table of equalisation standards here:
