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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: Dummy's Guide to: Soft-Start posted by Larry I on April 14, 2006 at 07:23:35:
Tube rectification gives you very nice soft start of plate voltages, should be sufficient in that regard.The other area where soft start would make sense is filaments. Applying full voltages to cold filaments usually means large initial current surge. That could be addressed in a couple of ways. If you have some excess voltage (say, you have close to 7V), then you can put a resistor in series with the filament. If you size it so it dropps a few tenths of a volt under normal conditions, it will have good effect on initial surge.
For preamp tubes generally speaking a DC is recommended. Usually that DC is regulated with something like LM317 or LM350 three terminal regulators. If so, adding soft start to those is trivial.
If unregulated DC is used, then the resistor approach will also work.
One thing to keep in mind on power amps - especially if it uses fairly high plate voltages on output tubes - do not delay the filament supplies on those significantly - you want the filaments become hot enough before the plate voltage reaches its full value, else you can have cathode stripping in some tubes.
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Follow Ups
- Re: Dummy's Guide to: Soft-Start - Victor Khomenko 07:55:11 04/14/06 (1)
- Well said! - Mike Burrows 12:45:33 04/14/06 (0)
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