microphone CAD equitek E100

CAD`s original E100 microphone was an inexpensive (for its time) multi-purpose studio condenser microphone, with an electret capsule and a neutral sound profile. Part of CAD`s Equitek  series, the E100 had an innovative transformerless amplifier circuit design. Typical FET (field effect transistor) condenser microphones use discrete designs. Thi
microphone CAD equitek E100 - schematic

s means they use individual transistors that must be carefully matched for proper characteristics. Even with careful matching, discrete designs are inherently nonlinear. Equitek microphones use a different approach. We do not use any discrete FETs. Instead, we use advanced high speed OpAmps (Operational Amplifiers). These OpAmps are individually laser trimmed for optimum performance and have very high gain. This allows a large amount of negative feedback to be used to significantly reduce any non-linearity. During transients, these OpAmps may require more current than typical phantom power supplies can deliver. The extra current demands are accommodated by our unique power supply design. Instead of using phantom power to operate the microphone, we use it to charge a pair of rechargeable batteries. This system creates a huge current reserve for the microphone`s electronics, yet there is no maintenance involved because the microphone automatically keeps the batteries charged during use. The OpAmp in the mic`s output circuit is an OPA2107, according to the schematics. The OPA2107 was manufactured by Burr-Brown, and is currently made by Texas Instruments. The mic could be powered by 48V phantom power, or by two 9V user-supplied batteries (not to be confused with the rechargeable batteries built into the amp circuit). The E100 capsule was a back-electret design manufactured by a company called Primo. (The capsule was eventually...

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