An very interesting site with one electron tube RIAA schematics

Is the www.tube-classics.de website.


Feeding back from anode to the grid of the same electron tube should be a great way for de emphasis. It can also be seen on the EMI BTR2 playback amplifier where the 6dB per octave low pass filtering de emphasis is done by a series resistor capacitor combination from the front end tube anode to its grid. Part of the circuit is the input transformer of the reproducing head. One of the best tape recorders of all time used by EMI at its studios around the world. We can tell the quality sound from the 50s? 60s? recordings we all know.


Another interesting circuit of RIAA de emphasis for MM cartridges with feedback form the anode of the front end tube to its grid can be found on the VTL book.


References:


E.M.I. Professional Tape Recorder Model BTR/2AM and BTR/2AMR Instruction Manual


The Vacuum Tube Logic Book - David Manley - VTL