Weight Tank has released a new updated version of its WT-72 tube microphone preamp and DI.
Best known for their use at Abbey Road on Beatles albums, original V72 amplifier modules had a factory set fixed gain of 34 dB (modified to 40 dB at Abbey Road). With further modification, they could be set to even higher amounts of gain.
Other than input or output attenuation, it is difficult to change audio level running through the modules on-the-fly.
“I always felt that a V72-style amplifier could be designed in a way that could use input attenuation, but also feedback manipulation to change gain within the actual amplifier,” says Locomotive owner Eric Strouth.
“This can help decrease the noise floor at almost all gain settings and keep the AC and DC feedback of the original design intact—but this poses a big problem. When changing amplifier gain with a switch, huge transient pops would occur, like a gun going off in your monitors. Not the best for your gear or hearing! Designing a circuit that could do the gain changing and deal with the side effects was challenging.”
Ultimately, a circuit design with muting capabilities was the answer. In the new Weight Tank WT-72, each time the user rotates the gain knob, the output mutes, the gain is changed and then the output is un-muted, all with the loud pops eliminated.
“With this new switching system, the WT-72 is able to offer the familiar frequency response and overall performance of the original at each of the 10 gain settings, all the way up 56 dB of gain,” says Strouth, “and it still has the character of the previous WT-72, but the lower noise floor is just icing on the cake.”
Check out the new WT72 Rev C here.