abbey road d enfer said:
Quote
In the AKG circuit the spring is driven from both ends so that the primary signal is nulled in the spring itself.
I'm not so sure about it. Thorough analysis of coil/magnet orientation and coil polarity is needed to confirm that.
to be more precise:
-there is two coils per end sealed together at 90° (like blumlein...just for the mechanical representation...) in a single magnet field.
at electronic side:
-input amp is splited at output to two driver (with a balance trim), where each driver drive one end of the spring.
-the spring return amp(two of them), coming from opposite spring end coil, is also splited at is output, part of the signal go back to the inverted input of the coil driver amp, an also feed the sum/output line amp !
-at the output amp, one spring end drive the inverted input, and the other the non-inverted input, with also a "balance" trim
-the "time setting" is a variable DC which adjust gain/bias at 3 amp simultaneously, the input, and the two buffer used for the spring feedback in the inverted coil driver input
this is for one side of the reverb....you ave all this twice, stereo unit
the electro-mechanical spring assembly, use two sprigs (around 1.5m each) 4 magnet and 8 coils :
So...there is chance that "boing" nulling is mainly done at sum/output amp, wile the internal feedback (inverted) is the damping
But as there is a complex mix of spring feedback and phase inversion summing in various location of the signal path (including coil ?), "boing" shaping should be complex too...
Best
Zam