T-power, also known as Parallel, A-B, or Tonaderspeisung powering, was one of the original techniques used to power condenser microphones remotely from mixing consoles. It uses the microphone cable as the power conductor, eliminating the need for batteries or external power supplies. Phantom powering has effectively displaced T-powering as the standard microphone powering technique.
T-power requires voltage (9-12 VDC) across pin-2 and pin-3 (pin-2 positive, pin-3 negative across 180 ohms) of the balanced mic cable to power the microphone. T-powered microphones from manufacturers such as Schoeps and the Sennheiser are still in use by sound engineers today. Some T-powered microphones can consume less power than the equivalent 48 V phantom powered version. Additionally, T-powered microphone users argue that T-powered microphones are less susceptible to hum and RF noise. For these reason, some production sound mixers still consider their T-powered microphones relevant tools and have no need to remove them from their kits. Because of these legacy microphones, Sound Devices continues to offer T-power on select field mixers. The Sound Devices 302, 442, and MM-1 offer the ability to power T-powered microphones.
Things to Consider
- Phantom power and T-power circuits are not compatible. Only apply T-power to T-powered microphones. Applying T-power to non-T-powered microphones (including ribbon, dynamic, and Phantom powered mics) may potentially damage the microphone.
- In general, Phantom power applied to a T-powered microphones will not do any damage. It is best practice, however, to not apply phantom to T-powered microphones.
- When using “red dot” T-powered microphones (reverse polarity T-power) with Sound Devices mixers use a polarity-reversing adapter on the input, otherwise damage to the microphone may occur.