Analog simulation of magnetic tape analog sound recording part 10

This part is about connecting just an inductor or a transformer at the line output of a Sony CD Walkman and thereby create a 70μs recording characteristic at this line output. (Ie rising output across the inductor at 6dB per octave until the frequency corresponding to 70μs ie 1:70:2:3.17 or 2.27KHz).


Calculation of primary inductance.


Assuming the line out output impedance is 370Ω.


If the wanted time constant is 70μs so as to simulate reel to reel 1/4in 7.5ips then


Since T=L/R


L=TR ie inductance is time constant times output impedance


Therefore


L=70μs x 370Ω       or


L=26mH


So firstly will be connected a Pleiades filter of 26mH, just an 26mH inductor in parallel to get an idea of how it sounds or corresponding measurements taken by playing a test CD with sine tones of constsnt amplitude.


Can the simulation be done with just one coil? Or an autotransformer?
It may be possible since on previous exoeriments inductors or transformers were deliberately overloaded with large sinewave input signals and the sound was similar in harmonic production.


But stepping up the signal that will go to the instantaneous reproduction amplifier by an auto transformer or a transformer may have the advantage of leading to even better signsl to noise ratio.


So the above process (stepping up) should simulate the playback head step up transformer too. The high signal will help to achieve low noise and possibly leading to de emphasis be done passively. For example with a series resistor and then a capacitor shunt to ground. Another resistor in series with the shunt capacitor should stop the high cut action (integration) at a frequency corresponding to 70μs ie 2.27KHz, -3dB turnover point.






L=26mH