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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: Biasing Question. posted by 33 1/3 on December 6, 2006 at 19:19:15:
I'm sure someone with experience using that amp will chime in...I have none. However, in general, the speakers should be connected, but the source components should be disconnected from the amp by removing the interconnects from the amp. Yes, the volume should usually be turned all the way down. It's also a good idea to turn the bias pots down (usually counter clockwise, but not always) to just above bottoming. This is to ensure that the tubes aren't immediately biased far too hot if the previous tubes have had several adjustments to the bias pots as they aged.As the amp is powered up, pay close attention to the tube plates for a minute or two and be prepared to shut her down immediately if you detect any plate redness as this is an indication of a bias supply problem in most cases.
If all goes well for the first couple of minutes, the meter will gradually indicate an increasing level of negative bias that should become somewhat stable at hopefully a lower reading than ideal. I usually let the tubes settle an additional 5 minutes or so while keeping an eye on the meter and the tube plates.
Once the tubes have run for 5 or 10 minutes, you can beging to gradually increase the negative bias. I like to do it in 3 steps...raising the negative bias about a 1/3 at a time over a period of a few minutes between each adjustment. This isn't so much for the amp, but when using NOS tubes it gives the tubes a chance to gradually be placed into full service.
Once you reach the proper bias setting, you can reconnect your source components and play some tunes for about an hour. After an hour, it's a good idea to recheck the bias on the tubes...you will likely see a small change in the settings as the tubes have aged from their new condition. I go ahead and reset the bias settings and run the amp for as much as 10 or 12 hours before rechecking and resetting the bias for a final time. Well, other than a periodic check every couple of months.
That's a broad generalization on biasing new tubes or new (or new to me) amps.
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Follow Ups
- Re: Biasing Question. - Catch22 20:09:05 12/06/06 (1)
- Re: Biasing Question. - 33 1/3 20:45:11 12/06/06 (0)
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