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SCA J99 Microphone Preamp Module SC90

SCA J99 Microphone Preamp Module SC90


Available without opamps (Add your own) or buy with SCA SC90 (John Hardy 990C-style opamps) included! (John Hardy 990C-style opamps currently unavailable)


The Seventh Circle Audio J99 is a flexible, high-gain, low-noise, low-distortion microphone preamplifier, based on the classic Jensen Twin Servo design. This is a great preamp to use when a neutral sonic character is required, but the slightest amount of euphonic transformer coloration is desired. Available as a DIY kit or fully assembled mic preamp module.


CH02-SP-J99 subpanel must be ordered separately.


    High Gain

    The J99B can provide 70dB of gain which includes the voltage step-up provided by the input transformer. Jumpered for 300 ohms input impedance, the maximum gain available is not quite 76dB.

    Low Noise

    With an EIN approaching -130dB, the J99 is quiet enough to use in virtually any recording application, especially with low-output ribbon mics.

    Dual DC Servos

    The J99B has a DC servo for each op-amp and uses no capacitors in the signal path.

    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.

    Lundahl Input Transformers

    The J99 uses a Lundahl 1538XL to couple the microphone signal to the amplifier. This transformer is used in a number of high-end preamps and it provides superior performance in a compact package.

    Cinemag Output Transformer

    The CineMag CMOB-2H output transformer provides a balanced, floating output with extremely low distortion and wide bandwidth.

    Flexible Power Supply

    On-board voltage regulators can accommodate power supplies from +/-27VDC up to +/-35VDC, allowing the use of op-amps with +/-24VDC requirements. Potentiometers allow easy voltage adjustment, making experimenting fast and simple. Local regulation also keeps inter-channel crosstalk extremely low when multiple preamps share the same power supply.

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