Word on the 'tubes is that the capacities are 1nF, 2.2 nF and 3.3 nF: https://www.youtube.com/watch?v=5qYvw9J6BhY&lc=RwrLBl6NlL6kAR4jOr1qFBaY0nmyGJio4-Pl4DyO_e8 . Those values seem to be a bit too high to simulate normal levels of cable-darkening: they're more in make-your-Strat-coil-sound-like-a-humbucker territory. (For anyone who's interested, Helmuth Lemme's table is handy here: https://www.buildyourguitar.com/resources/lemme/table.htm . Lemme gives a rough range of 300 - 1000 pF (0.3 - 1 nF) for cable capacitance http://www.buildyourguitar.com/resources/lemme/ but I'm pretty sure that doesn't quite reflect the extremes of short runs of modern, high-end cable on one end and truly nasty (or deliberately high-capacitance) old cable runs on the other. http://www.sengpielaudio.com/calculator-centsratio.htm is also useful here, for converting between Hz figures and musical pitches and intervals.) But a guitar site shouldn't have to rely on the manufacturers to tell it the capacitance (or inductance) of a passive component (including passive guitars and guitar pickups) these days. Mojotone is selling the Extech 380193 LCR meter http://www.mojotone.com/guitar-parts/Pickup-Winding-Tools/Extech-LCR-Meter-Model-380193#.VlYYdHbhAb8 for $220 plus whatever as "the industry standard for measuring guitar pickups inductance, capacitance and resistance". From grey resellers on eBay you can get the DER EE DE-5000, apparently even higher-spec than the Extech, for $100 plus shipping.