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balazer

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  1. I know this is an old thread, but I don't think the info already presented is correct. Here is what I gathered after a lot of reading, but someone who owns these mic packs will need to test: Sennheiser Evolution Wireless Transmitters These have a 2-wire mic configuration for common source mode: power through a resistor to the tip; signal on the tip; ground on the sleeve. The ring is a line-level input, which should be muted when not in use by shorting it to ground. Sennheiser EW Mics These are 2-wire devices for common source mode, with the drain on the tip and the source and case/ground on the sleeve. The plug should also short its ring to the sleeve. Sony UWP Transmitters These are meant for source follower mode, with signal on the tip, power on the ring (NOT through a resistor), and ground on the sleeve. The Sony service manual for the UTX-B2 shows the power line as 5 V with no resistor, and a load resistor from signal to ground of 10 kilo ohm. Sony UWP Mics Mics wired for Sony UWP transmitters expose their drain, source, and case/ground on separate contacts (ring, tip, and sleeve, respectively), so they're fully compatible with source follower mode and common source mode, just by changing the connector wiring. Adapting a Sennheiser EW Mic to a Sony UWP Transmitter Some mics wired for Sennheiser might actually be 3-wire devices. So it's worth disassembling the plug to check. If it's 3-wire, you'll find the source wire and shield both connected to the sleeve (and ring), and the drain wire connected to the tip, and then you could just switch the wires around to make the mic work with the Sony UWP transmitter in source follower mode (shield to sleeve, source wire to tip, drain wire to ring). But with only 2 wires, you can still build an adapter. A proper adapter would put the microphone in common source mode by having a resistor between the transmitter's ring and the mic's tip. 6.8 kilo ohm is the value suggested by Countryman for their B6 mic and Sony UWP transmitters, and I imagine that value will work with most 2-wire mics as it's a typical value for common source mode inputs with 5 V power. You do need that resistor, because it becomes the load resistor and the varying voltage across it is the signal output of the microphone. Then also connect the transmitter's tip to the mic's tip, and the transmitter's sleeve to the mic's sleeve. An improper adapter would connect the transmitter's ring (power supply) to the mic's tip (drain) and the transmitter's tip (signal) to the mic's sleeve (or ring, which is the source). The transmitter's sleeve (ground) would not be connected to anything. This puts the mic in source follower mode and you will get sound. But it's not a good configuration mainly because the signal is carried on the shield, which means it's effectively not shielded at all, and vulnerable to RF interference. Also the output signal (source) is fed back to one side of the microphone element, though I'm not sure if that would have any effect. If you had a 3-conductor cable (2 wires plus shield) from the mic plug to the mic capsule, you could have ground on the shield and still get a 2-wire capsule to work in source follower mode with a 3-wire input. That's certainly better than putting the signal on the shield, but the capsule's case would still be connected to the signal line, potentially allowing RF interference to enter through the capsule. Adapting a Sony UWP Mic to a Sennheiser EW Transmitter Wire the transmitter's tip to the mic's ring, and the transmitter's sleeve to the mic's tip and sleeve. You also need a wire from the transmitter's ring to the transmitter's sleeve, to mute the line input. Changing a mic between source follower mode and common source mode changes its performance characteristics. In common source mode, a mic will be more sensitive (by 9-10 dB), less linear, and have a lower SPL before severe distortion sets in.
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