The RMS5A7 Tubule from Roll Music Systems.
A real, transformer-coupled tube microphone preamplifier in the convenient package you never thought possible.
At long last, all the warm sweet satisfaction of a real transformer-coupled, high-voltage vacuum tube microphone preamplifier in the convenient and cost-effective 500-series modular format. 
With the explosion of new modular products for the 500-series frames sold by various manufacturers, user requests for a tube-based module have been met almost universally with claims by designers and engineers that it couldn't be done. We took that as a dare. The result is not only a technological achievement, but a sonic masterstroke.
The RMS5A7 Tubule from Roll Music Systems combines the full-featured convenience of a modern mike preamp module with the rich, satisfying sound of a transformer-coupled, all-tube preamp evocative of the elusive bygone classics. This is not a wimpy starved-plate design, nor is it an op-amp based preamp with a tube stuck on top for marketing appeal. It's all tubes and iron, with sophisticated modern power management circuitry to generate the high-voltage plate supply and high-current heater supply to power the tube. Careful design of this high-efficiency power circuit allows the Tubule to work within the space and power consumption limitations of a single module.
Robust transformer coupling and flexible, wide-ranging gain controls make the Tubule perfectly suited to everything from low-output vintage ribbon mikes to the hottest modern condensers. The input pad, attenuator and gain control also work together to provide a wide tonal variety. For the cleanest tones, keep the input attenuator up and the gain control low. For more rich tube coloration, engage the input pad and turn the attenuator down in order to use a higher gain setting without overloading the Tubule or other devices in the signal chain. The continuously-variable input attenuator also allows for very accurate gain settings that can be easily recalled.  The RMS5A7 Tubule from Roll Music Systems is now a part of the VPR Alliance. It has been independently confirmed to be fully compatible, both electrically and mechanically, with any enclosure that complies with the standards for the 500-series format.  

Specifications
Equivalent Input Noise (66dB gain, 150Ω source) -121dBu
Input Impedance 1200Ω balanced
Recommended Source Impedance 150Ω balanced
Maximum Input Level +22dBu rms
Maximum Output Level +25dBu rms
Output Impedance <300Ω balanced
Recommended Load Impedance >10kΩ balanced
Gain Range 3dB steps, 33-66dB
Input Attenuator Variable, -10 to 0dB
Input Pad Switchable, -20dB
Frequency Response +/-1dB, 10Hz-40kHz
Power Requirements
optional for optimal headroom +/-16V @ 0.100A
+48V @ 0.003A
Vacuum Tube 12DW7 / ECC832 / 7247