I was recently given a MA Cotter Co. Moving Coil Pickup Transformer Mk2L. That's all it says on it. Accept for the Serial number on the bottom. Does anyone know anything about this unit? How to use it? How much it is worth? I know absolutely nothing about step-up transformers. Any help would be appreciated. Oh the unit also has on it what looks like a Clearaudio logo.

Thanks in advance.

A pickup transformer is used to step up voltage about 10x. Of course, this also provides an impedance transformation. Source impedance of a MC cartridge is much lower than a MM cartridge, so it works out. Most MM cartridges are loaded with 47KΩ, but the best load for a MC cartridge is usually between 100Ω and 1KΩ.

Since a transformer giving a 10-fold voltage increase provides a 100-fold impedance increase, the typical 47KΩ load is transformed to a 470Ω load on the cartridge. You can decrease load impedance by adding a shunt resistor, or increase impedance by decreasing the turns ratio of the transformer.

Moving coil cartridges are usually pretty sensitive to load impedance, so it is worthwhile to match load to whatever the manufacturer specifies using a shunt resistor. You might even try a few values above and below the manufacturer recommended load to see what sounds best.

"How they accomplish this, we do not know. But Mitch Cotter is on the trail." Mitch Cotter, for readers who are younger than I—which seems like just about everybody these days—is an audio engineer who developed an especially nice series of phono products back in the 1970s, including a superb and still-competitive moving-coil step-up transformer". - Art Dudley; Stereophile

• Stereophile article

I e-mailed you but received no response. Did you receive my e-mail? Thanks for any information you can provide.

Mr Vinyl

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