Bella EXtreme 100 manual

Please note that all tubes are marked on their boxes and/or bases for the proper position within the amplifiers.

Installing tubes:
This procedure has been developed to better help you identify and located potentially problematic tubes.

Install each of the three 6SN7/6SL7 signal/driver tubes into their appropriate locations.

Be sure all bias pots are in their lowest setting. We have done this for you before shipping your amplifiers back to you.

With all associated equipment connected (never turn on a tube amplifier without speakers connected) and the volume control of your preamp set to minimum, turn on one amplifier (Only one amplifier should be set up at a time)

Within 30 seconds, you should hear the B+ relay click on. At this point, you will not see any readings on your bias meter.

Turn your bias selector knob to the V1 position.

At this time, with the amplifier turned on, install a power tube into the V1 position. After about 10-15 seconds, you should start to see the front panel meter show an increase in value. If you see no increase in value, make sure the bias selector is positioned on the V1 tube.

After this tube's bias reading has settled for about 45 seconds (should be between 10-200), move onto the V2 tube.

Turn your bias selector knob to the V2 position. At this time, with the amplifier turned on, install a power tube into the V2 position. After about 10-15 seconds, you should start to see the front panel meter show an increase in value. If you see no increase in value, make sure the bias selector is positioned on the V2 tube.

After this tube's bias reading has settled for about 45 seconds (should be between 10-200), move onto the V3 tube.

Continue these steps until you have all four tubes installed and seeing bias readings as mentioned above.

Once you have completed the first amplifier, complete the process with the second amplifier.

If you experience a tube bias that continues to rise and approaches a reading above 450-500 and you cannot turn this down via the adjustment pot, you could potentially have a bad tube. If this happens, quickly turn off the amplifier and remove that particular tube and try a new tube. If this continues to happen with multiple tubes, a problem may have occurred in the circuit. At this time, please contact Response Audio for further assistance.

Biasing

Allow both amps to warm up for about 20 minutes. After warm-up, start to bias each tube as indicated. Work on only one amplifier at a time.

Biasing is a simple process taking only a few minutes. To bias each tube, set the bias selector knob to the "V1" positions and adjust the bias pot for the corresponding V1 tube. Next, turn the bias selector knob to the V2 position and proceed to bias the corresponding V2 tube. You must proceed to bias all eight tubes in the same manner. Please note that to increase the bias voltage, the bias adjustment pot is turned counter clockwise. At this time, bring each tube up to 300 +/- 10. You will want to run the amp for a minimum of 1 hour at this lower setting. You will not experience the full dynamic capability of the amps at this point. Please do not try to reach high volume levels while the tubes are biased at the 300 level.

After approximately 1 hour of use, you can now repeat the bias procedure and bring each output tube up to 400-450 on the front meter. We recommend a maximum bias setting of 450mV for a safe and longer tube life. This is where you will want to run your amplifiers for normal listening. Do not be alarmed if you see a fluctuation in the bias reading of +/- 10.

After 3-4 hours of use, you can double check and adjust as necessary the bias levels as they will change within the first several hours of use. It is recommended to check and adjust the bias at approximately 50, 100 and 200 hours of use as it fluctuates for the first 200 hours of use as the tubes settle in.

Triode/Pentode switching: "T" = Triode / "P" = Pentode

Please note that when the amplifiers are run in triode mode, the power output is decreased to approximately 60 watts. You must make your selection between triode and pentode before the amplifier's power is engaged.
NEVER USE THIS SWITCH WHEN THE AMPLIFIERS ARE POWERED UP. DAMAGE TO YOUR SPEAKERS AND/OR AMPLIFIERS CAN RESULT FROM SWITCHING WHEN POWER IS APPLIED.

FULL MANUAL IS IN THE WORKS. Please call toll free 1-888-785-9773 with any questions or concerns about the setup and biasing procedures.

Sincerely,

Bill Baker