I recently purchased a DRRI and have some questions I hope you guys can help me with: 1. I want to replace the power tubes so I will have to re-bias the amp. The manual doesn't cover this other than saying to take it to a tech. I have a multi-meter to test with, but I need to know what the test points are, what the correct bias voltage is, and where the bias adjustment pots are located? If anyone knows of a site with step by step procedures that would be great. 2. I've read that you can jumper between the two channels. Why do people do this and what is the advantage? How is it done? 3. For you tube rollers, what have you found to work well with the DRRI? I don't want to spend a fortune on NOS tubes, but would like to put in some quality tubes that can be had a reasonable price. I would like to roll in something that would tame the brightness and bit and get warmer a more round sound if possible. Your help is appreciated and if you have any other suggestions on how to get the most out of this amp I would love to hear them. Thanks.