The purpose of setting the bias of an amp is to find the optimum setting for the flow of current when the amp is idling.

1) Install the new quad of el34s

2) Turn the volume of your preamp-source down to zero

3) With the speakers hooked up etc, turn on the amp

4) Leave it on for half an hour, without any signal, so the tubes can warm up

5) Now you need to set your meter to measure low voltages -- you're aiming for a voltage of 1.56V here.

6) You want to connect the ground tip of the meter to any ground point (the sleeve of the bias-test jack or anywhere on the case.) Then attach the tip of the meter to the bias-test point (I usually start with L). You should use a small slotted screwdriver to adjust the bias-adjust pot on that channel very slightly in one direction or the other until you get roughly 1.56V. Don't worry about being too precise on this round...

7) Now do the same for the other channel (R)

8) And then go back to the L channel -- you'll often find that the bias-adjust on the R has thrown it off. Again, don't aim for super-precision at this point.

9) You can turn up the volume and listen now. Let the amp run for several hours, or even a day. Then repeat the bias adjustments.

10) You might want to readjust the bias a couple more times over the next 2 weeks or so.

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