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Re: Best inductors for RIAA?

Hi,

First, the Pultec RIAA Network (yup - Pulse Technology - an ex Bell/WE Subsidary orginally pioneered this network - don'tchahateit when you get another - invented by WE item) has a few peculiarities. First, it requires termination with 600 Ohm and 600 Ohm or less drive impedance. This effectively limits the use to transformer coupling and suitable low anode impedance, high gain Valves, which IMHO limits the usefullness. I should add that the late and great Nobu Shishido used Black Gate Caps for capacitively coupling the Tango RIAA Unit to a 6DJ8/6922 Mu-Stage.

I have thought about this myself long and hard and I am now in the process to develop with Stevens & Billington a pure RL RIAA (no f...ing capacitors here) using Inductors made exactly to this purpose, individually tuned, with defined and controlled leakage capacitances aimed at termiinating the Network in common high Gm, medium Mu Valves, build on big airgapped mumetal cores and shielded (shielding is needed for avoidance of hum pickup). The Values will be 31.8H and 7.5H....

Once fully developed these Inductors plus the whole schematic for the RL EQ after adding three resistors will be generally avaiable. The Network terminates into around 100k and requires a maximum source Impedance of around 6k rather than 600 Ohm.

Ciao T


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