Tuesday, February 21, 2017

Variable proximity effect compensation by varying the load of the output transformer

This is in reference to the previous euroelectron post.


The Pleiades V6 microphone preamplifier  with the EF183 electron tube is in a single ended output transformer configuration. It operates in class A, ie electrons flowing all the time. DC current is passing through the primary of the output transformer as it is connected directly to the anode instead of using an anode load resistor.


It was verified as expected that by decreasing the load connected to the secondary of the output transformer the bass responce increases while gain decreases.


It may prove simple and effective to have a potentiometer as a variable load resistor at the output.


In this way the cutoff frequency can be adjusted compensating for the proximity effect at various distances from mic to source.


Effectively it behaves as an equivalent to the focusing adjustment of a camera for close up (macro) photography.


Different time constant for different sound object distance for a flat (focused) frequency responce.

No comments:

Post a Comment