Some singing recordings were done with GarageBand using RE15 at 0in from mouth and its low cut off.
Signal to noise ratio was amazing and the mic could be used even outdoors at out of the city areas.
Setup:
0in - RE15 - Pleiades step up transformer (30mH:19H) inside Neutrik modular adaptor - Pleiades K117 pre preamplifier with 220 ohms Rs - iPad - GarageBand - Sennheiser HD 580
When mic was not connected one could hear hiss with a mid high content. Overall hiss almost completely disappeared when a 0 Ohms male XLR was connected instead of the mic. When a 200 Ohms male XLR was connected some hiss could be heard indicating the setup could read the Johnson noise from the 200 Ohms resistor. When the mic was connected, the more quiet the recording location the less hiss could be heard.
When the setup was changed to the vacuum tube battery V4 pre preamplifier the mid high hiss content disappeared indicating that there was an undamped reasonance in the Pleiades 1:25.5 step up transformer. The Pleiades V4 has an approximate 100KΩ input impedance due to the high Megohm positive bias resistor from anode to grid which makes possible the EF183 tube operation at just 4.8V anode voltage.
This loading in the transformer made a softer more natural sound. So a shunt resistor of 100KΩ was connected just before a K117 JFET with the same natural effect. The RE15 sounded less high frequency peakey and more natural.
An inline XLR adaptor can be made that contains an 100KΩ shunt resistor or a variable resistor for varying the bandwidth and reasonance of this setup.
Note: The Pleiades proximity compensating transformer used was made as follows:
The Magnetec 073 core was used. 700 turns for the secondary. The first 200 turns wound one next to the other occupying almost one layer. The next 500 turns were wound with deliberate sloppiness. 100 turns pre layer were wound. The primary consisted of 31 turns.
Signal to noise ratio was amazing and the mic could be used even outdoors at out of the city areas.
Setup:
0in - RE15 - Pleiades step up transformer (30mH:19H) inside Neutrik modular adaptor - Pleiades K117 pre preamplifier with 220 ohms Rs - iPad - GarageBand - Sennheiser HD 580
When mic was not connected one could hear hiss with a mid high content. Overall hiss almost completely disappeared when a 0 Ohms male XLR was connected instead of the mic. When a 200 Ohms male XLR was connected some hiss could be heard indicating the setup could read the Johnson noise from the 200 Ohms resistor. When the mic was connected, the more quiet the recording location the less hiss could be heard.
When the setup was changed to the vacuum tube battery V4 pre preamplifier the mid high hiss content disappeared indicating that there was an undamped reasonance in the Pleiades 1:25.5 step up transformer. The Pleiades V4 has an approximate 100KΩ input impedance due to the high Megohm positive bias resistor from anode to grid which makes possible the EF183 tube operation at just 4.8V anode voltage.
This loading in the transformer made a softer more natural sound. So a shunt resistor of 100KΩ was connected just before a K117 JFET with the same natural effect. The RE15 sounded less high frequency peakey and more natural.
An inline XLR adaptor can be made that contains an 100KΩ shunt resistor or a variable resistor for varying the bandwidth and reasonance of this setup.
Note: The Pleiades proximity compensating transformer used was made as follows:
The Magnetec 073 core was used. 700 turns for the secondary. The first 200 turns wound one next to the other occupying almost one layer. The next 500 turns were wound with deliberate sloppiness. 100 turns pre layer were wound. The primary consisted of 31 turns.
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