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SCA A12-500 Series Microphone Preamp Module

SCA A12-500 Series Microphone Preamp Module


This is the 500 series module only! It will not work in any of the SCA chassis! There is an SCA only version of the A12 available as well in the Classic series section. The 500 Series kits require voltage measurement and calibration which can be easier with the use of a 500 series extender kit. We recommend this:


The Seventh Circle Audio A12 is a simple, single stage preamp roughly based on classic American designs of the early '70s. Built with the suggested transformers and op-amp, the result is an amplifier with an aggressive midrange and pronounced transformer coloration. The A12 sounds fantastic with rock drums and electric guitars, but is versatile enough to be used with a wide variety of source material and microphone combinations. Available as a DIY kit or fully assembled mic preamp module.


    High Gain

    The A12 can provide 70dB of gain, including the voltage step-up provided by the transformers. This is more than enough gain for most applications, especially with modern high-output condenser microphones.

    Stepped Gain Control

    A 12 position Grayhill switch provides accurate and repeatable gain settings in 5dB steps from 15dB to 70dB.

    Gain Trim

    Since 5dB is often too big a gain step, the A12 also has a gain trim control, which provides up to 6dB of cut at any gain setting. This allows very fine adjustment of gain between steps.

    Phase Reverse

    Inverts the signal phase.

    Phantom Switch

    Slow-rise phantom power minimizes pops and thumps.

    Neutrik Connectors

    High quality PC mount connectors eliminate cabling and ease assembly.

    CineMag Input Transformer

    The A12 uses a CineMag CMMI-8-PCA to couple the microphone signal to the amplifier. Manufactured to exacting standards, this transformer gives an 18 dB voltage step-up, has excellent specifications, and provides distinctive sonic qualities that compare very favorably to vintage units.

    CineMag Output Transformer

    The steel-core CMOQ-2S gives the A12 an aggressive character virtually indistinguishable from certain vintage amplifiers.

    The A12 is available with one of three output transformers, each with a slightly different character. The 2S is the standard, which most people LOVE! The 2L and 2H are $45 and $65 additional and WILL increase order shipping timeframe.  Please email first if you would like to order a 2L or 2H transformer!

    2S 100% steel laminations, lowest cost, highest distortion
    2L 50% / 50% steel/high nickel laminations, best compromise
    2H 100% high nickel laminations, highest cost, lowest distortion

    Built-in SC25 Op-Amp

    The A12 has a high-performance discrete op-amp laid out directly on the main circuit board. The circuit is exactly the same as our very popular SC25 amplifier module.


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