Deutsche Version 
Fill in the box above and click at the appropriate 'calculate' below. The Greek letter for the time constant is tau = τ and 1 microsecond is 10^{−6} seconds. 
Time constant τ in µs 
Cutoff frequency f_{c} in Hz 
Equalization emphasis 
7958  20  • (RIAA) 
3183  50  • RIAA, NAB 
1592  100  
318  500  • RIAA 
200  796  
140  1137  
120  1326  MC 
100  1592  
90  1768  MC 
75  2122  • RIAA, FM 
70  2274  
50  3183  NAB, PCM, FM 
35  4547  DIN 
25  6366  
17.5  9095  AES 
15  10610  PCM 
12.5  12732  
10  15915 
Cutoff frequency:
Time constant:
Conditional equations:
Cutoff frequency f_{c} in Hz = 159155 / τ in µs
Time constant τ in µs = 159155 / f_{c} in Hz
The possible preemphasis/deemphasis of a PCM recording for DAT or CD (15/50 µs EIAJ DAT/CD).
Cutoff frequency:
Time constant:
Conditional equations:
Cutoff frequency f_{c} in Hz = 159155 / τ in µs
Time constant τ in µs = 159155 / f_{c} in Hz

Time constant and cutoff frequency
AME  Ampex Master Equalization Curve
There was also an "Ampex Master Equalization" around the year 1958, called AME. It was
based on modifying the NAB response with an auditory (hearing) curve, which resulted in a
recorded flux that had a "hump" (re the NAB EQ) from about +3 dB at 630 Hz to +8 dB at 2 kHz, back to +3 dB at 5 kHz, and down to −12 dB at 16 kHz; see the AME curve: http://home.comcast.net/~mrltapes/pubame.pdf http://www.richardhess.com/tape/ame_equalizer_20040412.pdf 
In USA FM radio has a time constant of 75 µs, but also in Korea,
Taiwan, Thailand, AFN worldwide and the rest of America. In Europe FM radio has a time constant of 50 µs, but also in Africa, Asia (without Korea, Taiwan, Thailand), Pacific. 
To use the calculator, simply enter a value. The calculator works in both directions of the ↔ sign. 
Time constant τ = R × C R = τ / C C = τ / R
Time constant in seconds = Resistance in ohms × Capacitance in Farad
Please enter two values, the third value will be calculated.
Corner angular frequency ω_{c} = Angular frequency ω_{c} The corner angular frequency ω_{c} is developed from the corner frequency f_{c}: ω_{c} = 2 π × f_{c} Corner frequency f_{c} = Cutoff frequency f_{c} For systems that correspond to a differential equation of first grades the cutoff point is the intersection of the horizontal asymptote with the asymptote of the falling branch of the Bode diagram. At this point, the level is −3 dB and the phase shift is 45°. This means that the amplitude drop of the output value reached 30% of the input size. At the same time the time constant τ of such system is: τ = 1 / ω_{c} = 1 / 2 π × f_{c} 
To use the calculator, simply enter a value. The calculator works in both directions of the ↔ sign. 
The increase of 20 dB per decade is equivalent to the increase of 6 dB per octave
6 dB/octave = 20 dB/decade 12 dB/octave = 40 dB/decade 18 dB/octave = 60 dB/decade 24 dB/octave = 80 dB/decade 20/6.0206 = 3.3219 There are 3.322 octaves in 1 decade, so 1 dB/decade = 3.322 × dB/octave. 
To use the calculator, simply enter a value. The calculator works in both directions of the ↔ sign. 
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