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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: Folks' Thoughts on Individual Bias Pots and Emissions Testers posted by tvr2500m on September 29, 2004 at 08:43:09:
It's RAM... Roger Modjeski. There was a HUGE debate between David Manley and R.M. over individual bias pots. I'm sure you can find it on the web. For Rogers' thought on gm testers and bias pots, check RAM Labs website. Essentially, if all tubes were perfectly matched and stayed that way, one bias pot would be better. Read Hafler and Keroes' article on this in Journal of the Audio Engineering Society. But, this is not a perfect matched world, so adjustment is nice. For lowest distortion and best linearity and power, the optimum are curve-trace matched tubes with individual bias pots for SMALL tweaks as they drift apart. The main point is that some audiophiles delude themselves into thinking that radically different tubes (plate curves) can be made to operate the same by adjusting the DC idle current at a single operating point. Just because 4 tubes can be made to draw 50 ma each at idle with bias voltages of -37, -53, -29 and -40 does not mean by a long shot that they will behave equally under dynamic operation with AC voltages. Long story short; get matched tubes AND individual bias pots. Neither one is perfect by itself.
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Follow Ups
- Re: Folks' Thoughts on Individual Bias Pots and Emissions Testers - g 10:38:37 09/29/04 (0)
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