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In Reply to: BDT Preamp Schematics posted by John Swenson on May 10, 2008 at 14:34:45:
Hi John,
Great to meet you at VSAC; I'm working on the BDT-based compressor and limiter. I have a couple of questions:
"The outputs go through a custom transformer from Dave Slagle designed for this circuit."
What is the primary inductance of this transformer? I was worried about being able to drive finite inductance at low frequency and at high attenuation when the plate current is ~1mA or less. I guess it's relative to the load resistor used to set the stage gain.
"If you look at the spec sheet for the tube the plate curves look perfectly horizontal, this is true with respect to the GRID, but NOT for the deflectors. In order to get horizontal plate curves for the deflectors the plates need to be cascoded."
I think the question is how linear will the transfer function be? The attached curves show my planned operating range (different tube but same basic circuit). The curves are measured with a fixed 250V anode voltage.
Looking at the pentode curve (not attached but they all look alike), one might expect small impact of anode voltage on current *OR ON CURRENT STEERING LINEARITY*.
However, the BDT/MOSFET cascode is IMHO even cooler than the regulator design and I will certainly give it a try with and without.
Thanks!
Michael
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Follow Ups
- RE: BDT Preamp Schematics - mjk 16:02:43 06/13/08 (0)
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