De mensen van Bugera weten het zelf precies niet ...

Op hun site staat dit te lezen:
Cathode biasing is the simplest biasing method. In using this method, bias is derived directly from the valve itself via a cathode resistor. It has the advantage of its simplicity and the capability to automatically adjust itself. As current drawn by the valve increases, so does the bias produced, thereby bringing the plate current back in line to its optimal point. Conversely, as the current drawn by the valve decreases, so does the bias, thereby increasing the plate current back to its optimal point. The drawback of cathode biasing is that it is limited for low- to medium-power amplifiers not exceeding 25 watts output. Cathode biasing is also used in all low-level stages of valve amplifiers. You'll find cathode biasing in the classic amps popularized in the earliest days of the British Invasion as well as some of the earliest American tweed amps.

Dan stuur ik dit op naar de kerel die mij de mail gestuurd had, krijg ik dit als antwoord:
Yes, if both tubes were replaced they would still need to be biased. While that article certainly points out that the V5 might be cathode biased we have been told they are indeed a fixed bias of 42mA target current.