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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: safest way of biasing an amplifier internally posted by afg on January 25, 2006 at 00:47:45:
Why are you guys using dummy loads to set the bias? The speaker terminates the amplifier properly. After all the amp is DESIGNED to drive a loudspeaker! When setting bias there is NO AUDIO. NONE. If you get a different reading with different loads it is because the amplifier is unstable and oscillaing with one or more load conditions.Disconnecting the input cable is also not necessary. It is not even a good idea. Most amps are stable and quiet with the input open, but not all of them. Leave the cables connected and turn the volume OFF, or select an unused input.
Meter error is certainly a concern, but calibrating it every time you use it is overkill. If the meter is of decent quality and not 800 years old it is likely fine. Especially if you know its history and know it has not been overloaded or dropped. Most of the analogue meters like the Simpson 260 are purely shunt loaded microamp meters. There is no active circuitry to go bad, no caps to leak, no tubes to get tired. If you want to verify that the meter is at least close, compare it to a friends meter that is beleived to be good or test a new D cell or C cell to see if it is near 2 volts. If you need or want a true calibration send the meter to a calibration lab and have it calibrated.
Look, setting the bias is a routine inspection and adjustment, not a space shuttle launch. It is not supposed to be difficult, complicated or a pain is the neck. Read the manufactures instructions, ask a freind to teach you, pay the over-priced repair tech to teach you. Once you get the idea it will be a simple matter to perform the task of setting the bias.
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Follow Ups
- You guys are way out there - It is not complicated - beermanpete@socal.rr.com 22:48:10 01/26/06 (0)
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