How to adjust BIAS on Audio Research D160?

Only the 6550's need bias adjustment. You will need a voltmeter and screwdriver. And the amp MUST be connected to a pair of speakers before turn on!

 How long has it been since the amplifier was used? What is the condition of the caps? Have they ever been replaced? If the caps are original they most likely need to be replaced. If it has been a while since the amp has been used and even if it has not, I would bring it to an ARC authorized tech and have it looked over. He can bring it up slowly an a variac. A tech can make sure the amp is up to spec and it is working properly. It is a great old amp so you don't want to take the chance of it being damaged.

 If you don't have the manual a pdf version is available online. Jim McShane can help you with the best tubes for the amp. Just do a search for Jim McShane tubes to find his website and send him an email.