In Reply to: On Capacitors.. posted by Lee of Omaha on April 24, 2016 at 07:45:43:
Air dielectric variable caps do exist; they were used for many decades in radio tuners. Air is nearly as linear as vacuum ...
I believe they have been used in RIAA circuits at fairly high impedances - I get 2.13Meg + 310K resistances with 1000pF + 343pF caps. If you have the gear, you can trim then exactly. Most often the capacitance is in the range 250pF to 500pF but they usually have at least two caps on the same shaft, which can be paralleled. Be aware that grid leakage in the next stage could easily throw things off.
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- RE: On Capacitors.. - Paul Joppa 16:02:09 04/24/16 (0)