Tuesday, February 23, 2016

GSM 1 impedance matching transformer with Pleiades K117 pre preamplifier

A GSM 1 transformer was tested with very promising results.


It is housed in an XLR male to female adaptor with switch for low and high output impedance.


There is a black tape with gold letters that reads Line Transformer 500Ω --- 600 Ω/ 50kΩ.


The case carton reads Audio GSM1 e+p Mikrofonadapter, Mitch umschaltbarer Impedanz, e + p Elektrik, 59423 Unna, Germany


Primary inductance was measured 219mH and low secondary 263mH and high secondary 50.3H.


It worked great with Electrovoice RE16 and Shure Unidyne III. It did some proximity effect compensation and the mics sounded best at about 9in.


The hi low switch was very useful and fun to use acting like a boost turbo switch.


For smaller microphone distance lower primary inductance is needed as used in some Pleiades filters and transformers.


Signal Path:


Mic - GSM 1 - Pleiades K177 - Realistic Stereo Mixer - Sennheiser HD -580


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