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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: Re: If tubes are sold in a sleeve... posted by 7N7 on August 29, 2001 at 09:27:15:
Hi 7N7!What I usually do for matching is to burn in the valves at a high load operating point, and than match them for gm at a given operating current. For critical cases I either do a 'three point match' - median
operating current, gm at expected minimum and maximum input voltage.For power valves I do visual matching on the curve tracer.
Important in this context is the fact that I tend to desingn circuits for a fixed idle bias current rather than for a fixed bias voltage...
the bias voltage is either set by a cathode resistor or a variable negative voltage on the grid, adjusted for the 'design bias current).Best regards,
---mb---
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PS: Matching at a fixed grid bias voltage did never make too much sense to me - it just leads to a too high (unjustified) reject rate...
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Follow Ups
- Gm matching... - mb-de 08/30/0110:54:32 08/30/01 (2)
- Re: Gm matching... - Pär 06:21:42 08/31/01 (1)
- Testers and ditching of valves... - mb-de 11:41:24 09/3/01 (0)
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