Microphone Preamp Input Transformers

Microphone preamp circuits often feature a transformer on their frontend to take advantage of the almost noiseless gain that a well designed transformer can supply. When used properly, transformers can add 6 to 24dB of gain in the critical first stage. As with most components there is a trade off involved as the gain increases. As the turns ratio increases, high frequency response tends to roll off. Also there is less room inside the transformer for the input winding which can result in raising the distortion level at low frequencies. Lastly, the higher turns ratio requires that the impedance the transformer is terminated with be increased, which can create its own set of issues.

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Crimson offers 2 standard versions. The CT-110mp has a 1:10 ratio for a 20dB gain,and the CT-108mp is a 1:8 for a gain of 18dB. Both are wound with a high degree of interleaving between the windings to produce a very flat frequency response. They each have high nickel alloy laminations, and the units are encapsulated in a mu-metal can for EMI noise reduction. They have a standard PCB mounting pattern.

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We can also manufacture many custom versions for OEM applications. Turns ratios can be varied from 1:2 to 1:18. Different interleaving techniques can be used to produce a more “peaky” response curve. They can be configured with dual input or output windings for selectable gain. Flying leads, or other PCB mountings with other mu-metal cans are also available.