Phantom powered FET preamp cable with output buffer

Posted on Feb 7, 2014

This is a phantom-powered FET preamplifier built into a 1/4` guitar cable, similar to the one on the Tillman site. There are only a couple of parts to the amplifier, so the difficulty was being able to trim and solder component leads to fit within the space of a 1/4` plug. The phantom-power end of the cable plugs into a small Hammond 1590A box. I went with battery power to keep the leads clutter-free. It draws less than 3mA (I'm not using an LED).

Phantom powered FET preamp cable with output buffer
Click here to download the full size of the above Circuit.

I added a buffer at the phantom-power end for better line driver capability to the pedal train or amplifier. A small improvement to the Tillman circuit, but it throws a shout out to better noise immunity with a low drive impedance while also buffering the preamp circuit output. It's a nice unbalanced mini-DI/Line Driver.

An FET's high input impedance (read:buffer) makes it the best example of where an FET amplifier should be placed in terms of S/N benefit: close to the pick-ups. The just-a-guitar-and-cable crowd should be completely enchanted by a cable with gain. It's also friendly with effects because the...

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