Spectra Sonics 101 Microphone Preamp Circuit
The STX 100 is a 500 Series version of the classic Spectra 101 amplifier circuit. The STX 100 is a high-bandwidth microphone preamp with 64dB of gain and a 10Hz to 50KHz frequency response. A 10dB input pad and a dual potentiometer offers continuously variable input pad and output level controls allow the STX 100 to be used with both microphone and line level sources.
The STX 100 represents an affordable alternative for employing the same Spectra technology of our famous recording desks made over 40 years ago. The unique circuit topology of the STX 100 utilizes a 100 series discrete preamplifier design that was at the heart of every console built by the company. The result is unequaled performance in terms of expanded dynamic range, (headroom), low noise and distortion, as well as extended harmonic content of the amplified signal.
Most, if not all, conventional analog audio amplifiers live in a world whereby dynamic range limitations are dictated by audio program peaks. Audio program peaks, which can average 6dB to over 20dB, effectively reduce the undistorted output of a given amplifier by that peak to average ratio. The reduction in output limits headroom, (dynamic range), increases numerous forms of distortion, and limits the harmonic content of the amplified audio signal.
The STX series lives in the VU world, irrespective of peak to average transient audio program signal material. When a percussion instrument is the source, it is not uncommon to measure transient peaks that are 12dB-24dB above the program material average. Again, the STX series products are not affected by the high transient peak excursions. The first and second stages of the STX 100 utilize independent LED overload indicators to monitor program overload conditions. The result is faster set-up time with consistent and definable results. Drums sound like you are positioned next to them. Guitars have full harmonic content. The dynamic range of vocals is preserved.
STX 100 SPECIFICATIONS:
Gain: 64dB
THD: Less than .01% @ 20Hz-20KHz
Signal/Noise: Better than 120dB, (unweighted)
Maximum Output: +18dBm, 20Hz–20KHz
Power Requirement: Less than 50mA, +18dBm
Input/Output Control: Continuously Variable/10dB Pad
Input Impedance: 5K Ohms, Nominal
Output Impedance: Less than 50 Ohms
Frequency Response: 10Hz-50KHz
Phantom: 48 Volts
Polarity: 180 Degrees/Reverse/Mic or Line Input
