The primary inductance of the input transformer used is only 140mH. Secondary inductance is 16H. It is the version 1 transformer who did not make it as an output transformer. Turn ratio 1:10.
The sound was great but a little bass light in 635A due to the low input inductance for this microohone. The mic was used at a distance of 1in. Otherwise room ambience, reverberation gets in. With D130 the sound was slightly hard.
The MD441 U3 operated greatly at a distance of a few inches. The proximity effect was compensated in an impressive way. The brilliance switch is ingenious indeed. It is a joy to hear the smooth sound and flat frequency responce curve with no increase at mid highs.
There was some electromagnetic field noise captured by the mic which disappeared when the mic was rotated. The test inviroment is very electromagnetically noisy from other parts of the building. It has to be investigated what the cause is.
The Pleiades V6 was tested in breadboard condition. The Magnetec core transformers are unshielded. There did not seem to be a problem with the Electro-Voice 635A.
The Paso M980 sounded great too. Proximity compensation is important.
References:
Pleiades V6 schematic
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