Vacuum Tube Direct Interface

Requires that DC power be brought into the instrument, either through special cabling or an internal battery. Should not be done to collectible instruments if they didn`t come with onboard electronics. Conveniently implemented as a field effect transistor (FET) or bipolar junction transistor (BJT) follower, or perhaps an amplifier with modest gain. Can drive any impedance input,
Vacuum Tube Direct Interface - schematic

while eliminating stray capacitance in cabling and connectors. First made popular by Alembic in the late `60s and Music Man in the `70s. Active electronics inside the cable. Next best solution, allows a simple follower or amplifier to be placed very close to the instrument, for instance inside the plug backshell at the instrument end of the cable. Can drive any impedance input, while eliminating stray capacitance except for one plug and one jack. The instrument itself is unmodified. I have previously developed solutions of this type, which I call Active Plug technology. So-called "Active Cable" solutions are also commercially available. High input impedance amplifier. This is usually the least desirable solution, as it takes no account of cable capacitance. For some artists, of course, the cable is part of their sound and shouldn`t be messed with. But in applications where the desired signal is the voltage source inside the pickup, this just won`t do. Unless, that is, a way can be found to cancel out the cable capacitance. The remainder of this page describes a solution I`ve developed which does just that. Coaxial cable is commonly available and universally used for musical instrument pickups, often with 1/4" phone plugs on each end. But did you know that triaxial cable is also available Like coaxial cable, the triaxial form has an inner center conductor and an outer braided shield, but it also has an inner braided shield...

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