Spectra 1964 STX 600 combines a microphone preamp with the original 601 Complimiter circuit introduced in 1969, all in one 500 series module. The input section is the same one used in the rackmount C610 and V610 processors.
Peaks caught before they reach the converter
The limiter responds in under 90 nanoseconds, fast enough to stop a snare transient or a slap bass attack that a normal VCA compressor never registers. The compressor works more slowly, from 100 nanoseconds to 1.2 milliseconds, choosing its attack time from the programme material. In practice one module covers both converter protection and everyday vocal levelling.
Metering that tells you what is happening
The input knob sets the behaviour from clean limiting, through limiting with compression, to compression up to 10:1, while the output knob makes up gain and matches level to the rest of the chain. Two separate indicators show different things: an ultra-fast input threshold circuit catches peaks shorter than a microsecond, while the output indicator only lights on genuine clipping at +18 dBu. The input pad offers 0 dB, -10 dB and -20 dB, with phantom power and phase switches mounted at the top of the panel.
KEY FEATURES
- Microphone preamp and 601 Complimiter in a single 500 series slot
- 62 dB of gain for microphone and line sources
- Limiting, limiting with compression, and compression up to 10:1
- Input pad with 0 dB, -10 dB and -20 dB settings
- Separate input threshold and output clipping indicators
- 48 V phantom power and phase switch
TECHNICAL SPECIFICATIONS
- Input impedance: 1200 Ohm
- Output loading: 600 Ohm to infinity
- Maximum gain: 62 dB
- Input level: typically -50 dBu to +10 dBu
- Maximum output: +18 dBm at 600 Ohm
- Threshold attack level: -40 dBu
- Signal to noise: 80 dBu below +4 dBu output with -40 dBu input, 20 Hz - 20 kHz
- Frequency response: 20 Hz - 20 kHz, +/- 2 dB
- Limiter attack time: less than 90 nanoseconds
- Compressor attack time: 100 nanoseconds to 1.2 milliseconds
- THD: 0.03% at 30 Hz - 20 kHz, +8 dBu
- Power requirement: less than 80 mA at +18 dBu
