Lightning Boy Audio MC15 microphone input transformer for tube preamps.

The MC15 was specially designed as a high performance 1.4k:15k mic input transformer for tube preamp stages.  A gapped nickel-alloy core helps facilitate the MC15's relatively flat frequency response of 10Hz-23kHz, while also preventing DC saturation of the core. The other part of the frequency response comes from a complex winding geometry, which adds to the labor. The winding is nothing without a bobbin. The bobbin on which the coils are wound is manufactured in-house. The finished transformer is sealed in a MuMetal shielding can, which is packed with a chemically-stable vibration absorbing compound. The added compound helps prevent internal breakage of the transformer from external impacts. Combined with the expensive core and can materials, the MC15 is a complex design to wind and hand-assemble, which leads to its price. I like to think the subtle randomness of hand crafting something adds a bit of character to the sound. 

The MC15 is a dual purpose design in that it can be wired in reverse (primary and secondary coils swapped) in order to act as a DI output transformer.  When used almost the same way, but as an output transformer for a preamp circuit, the MC15 can have a very subtle effect on tone, with an extremely gentle softening of notes.  That said, it can also be used as a stand-alone, passive DI transformer.  In this case it's all about color and it definitely adds some with passive instruments.  Used in this manner, it can create a louder DI signal than any typical big-name passive DI boxes on the market.  All LBA input transformers come mounted in a MuMetal can for magnetic shielding, and they feature PC pins.

Included with the transformer is one custom circuit board for mounting the transformer, along with two female connectors with 6" wire leads, two male connectors, and 4 adhesive standoffs .

For KiCad design tools for the MC15, visit my website or email me. There are schematic symbols, footprints, and 3D renderings of the MC15 available for free.

Use caution when soldering the PC pins as to not overheat them. I typically work between 530-700°F with dwell times that average under 2 seconds. Avoid bending or forcefully pushing on the pc pins, as this could break their internal connections. More information is available on my website.