Comparison of JFETs for mic applications

[jp8]

Submit it to a fading low-frequency sinewave. I used to do that with a simple potentiometer, but today I can use a tone generated by a DAW.
I believe this method is documented in a Studer paper.

Or did you mean Jensen? See chapter 4.2 here.

Jan

 

[thor.zmt]

Or did you mean Jensen? See chapter 4.2 here.

Bill is in part correct.

I found the results far less subtle than he intimates, back in the 80's. Anyway, a modle from a mixing desk to be serviced could not pass basic acceptance tests with a magnetised transformer. Many that came had some gotten "magged". Must have been these wicked western imperialists magnetising upstanding socialist Transformers of the people.

Secondly, what we are trying to do is to "re-randomise" the magnetic dipoles in the magnetic material after they have become aligned into a specific polarity. This condition is kinda self-reinforcing. It usually takes to beyond saturation (hence my implied suggestion of 5Hz +20dBu) to overcome.

Another issue is that the fade must be very slow, an excessively fast fade doesn't guarantee sufficient randomisation. We "Devenir gris" pretty slowly.



As the signals drops so does the number of magnetic dipoles moved. Adding a significant amount of white noise to the VLF sinewave can be more effective and allows faster fade out.

Magnetised can's are PITA to clear, but commercial TV Tube demaggers (if they can be found) will do.

Thor

Un homme dans une gare désolée
Une valise à ses cotés
Des yeux fixes et froids
Montrent de la peur lorsqu'il
Se tourne pour se cacher

Sens la pluie comme un été anglais
Entends les notes d'une chanson lointaine
Sortant de derrière un poster
Espérant que la vie ne fut aussi longue

Devenir gris