AKG D130 and Electro-Voice 635a revisited

They were connected to an inline transformer with an input inductance of 220mH.


This transformer comes inside an XLR adapter in 2 versions. XLR female to XLR male, or XLR female to 1/4in jack.


The box on the first version says: Audio GSM 1, e+p Elektrik, 559423 Unna, Germany
The other one was bought without a box.


They both have a switch to choose from either 500Ω : 600Ω or 500Ω : 50KΩ.


The nearly 1 : (1 plus something) setting is very interesting too as effectively one has a Pleiades filter and at the same time a transformer isolating the mic while also stepping up the signal a little.


The Pleiades filter is made by the relatively low inductance itself and compensates for perceived increase in bass making the mic sound flat from vocal chords of singer to brain of listener.


The stepup option is very nice too.


Setup:


D130 or 635a - German transformer 1:16? - Pleiades V4, 3.4volts - Realistic Disco Mixer - HD580


With the 635a there were no s problems while with the D130 there were sibilant problems.


Then for another reason the mics were connected directly to Sony TCD5 pro II, (to check if phase makes a difference in sound on the Sony, and also whether the phase difference is due to interference from the direct acoustic wave and the wave coming from the headphones.


The Sony sounded the same on either phase connection.


Setup :


D130 - Sony TCD5 Pro II.Or
D130 - GSM 1 transformer at 500:600 - Sony TCD5 Pro II


The sound was very nice with the GSM trasformer on line for the reason explained above.


An interesting observation was that with the Sony recorder amplifier the D130 did not show any s problem.


The s problem happened only when playing back the cassette recording.


So it seems the s problem on the Pleiades setup comes either from V4 (not likely as it is the first stage) or the Realistic mixer overloading.


On the 635a there are no such problems on either setup. The D130 used has only its excellent metal mesh and nothing between it and the capsule. Is this how this microphone was originally made?


It seems the sibilant problem is an additive effect of mic and preamp combination. If for example a mic creates high spiky peaks, the problem is revealed in an amplifier with smaller transient overload headroom. More investigation is needed.