Simulating analog tape recording with analog electronics part 3

The objective is to instantaneously peak limit in real time or simulate the sound of reel to reel tape or disc records or FM broadcasting etc.


20Hz to 20KHz is 10 octaves.


If the magnetic ring core is fed with constant current...as is done on tape recording? On the Ferrograph series 6 schematic for example the head is driven by the high impedance output of an electron tube. This is the equivalent to a Pleiades filter or low cut, high pass for recording. Constant current will get the character of the sound of the magnetic core not only on bass but on most frequency spectrum as is done on magnetic tape. (Magnetic tape, the way it is used, does not only
saturate on low frequencies in the way audio transformers are used).


There will a reduction from treble to bass at 6dB per octave. This is 60dB lower at 20Hz than 20KHz.


The integrator (high cut) after the core secondary (simulating the replay head) would have to increase 20Hz by 60dB or a million times?


This of course corresponds to a high frequency time constant of much less than what is used at 30ips tape speeds. For 30ips the turnover frequency when integration stops is roughly at 10KHz.


But a 1,000,000 voltage ratio or 60dB voltage difference from high to low seems too much. On second thought an electron tube battery powered as on Pleiades V4 preamplifier for example could easily handle more than 60dB to 120dB?


Should the experiment start of with a 70μs EQ be used as in 7.5ips reel tape machines or chrome cassette?


Or premphasising the whole spectrum by say 3dB per octave? This would change the million requirement to a thousand. Can 3dB per octave be done by a suitable series resistor to the primary?


Or should a RIAA premphasis be fed to the toroidal transformer. This has two slopes, one going down below 1KHz and one going up above 1KHz. (It is interesting to hear how a vinyl record is recorded by connecting an MM or MC cartridge to a mic input, tremendous treble that have to be EQed at playback by the phono preamp.


If RIAA premphasis is used the output from the ring core transformer will have compatibility with MM or MC phono preamps and the sound may simulate characteristics of the record sound.


The conditioned signal can then feed an ADC for example.


Or should an FM broadcasting type 70μS turnover high frequency boost be used for premphasis?