VDC at a tube preamp's output

Hi all,

Was wondering if anyone had ever been able to null out the VDC at the output of a Tube Preamp, thus doing away with the need for the coupling caps.
Yes. Two preamps, the Messenger (single-ended) and the Atma-Sphere (fully balanced and differential) have direct-coupled outputs.
The other option is a transformer, like Jensen, which Rowland used.
I have always wondered how the DC is removed in the Atmasphere design. Anyone know?
Sure. There is a patent on the process, which is very similar to the Atma-Sphere power amps. The Patent Office supported 23 claims in the patent, which allows for a very simple method of creating a balanced DC coupled output. The output uses a circuit called a Circlotron, which has two power supplies which conduct in opposite directions through the load, the net result being- nothing.

A DC servo detects any residual voltage at the output, and applies a correction to the tubes driving the outputs. The correction voltage is heavily filtered to prevent audio from being part of the voltage- it only responds to DC.

The resulting output section of the preamp has bandwidth from DC to about 500KHz, which is much more effective than using a coupling capacitor. It also has a low output impedance, so it can drive a 600 ohm line and, in the case of the MP-1, 32 ohm headphones.
Hi, interested in the "Messenger" preamp. I had a hunch that something like that would have to be done. i was thinking since on a tube preamp, there is a B+ and a B-, and maybe using both of them to null out the DC. Well, I wasn't to far wrong.