SPL Atmos is a fully analogue, stand-alone surround miking preamplifier system designed for high-definition surround sound production in any known format. Conceived as a system-independent solution, SPL Atmos is ideally matched with the ASM5 indoor microphone system using selected Brauner VM1 capsules, or the INA5-R microphone array manufactured by Microtech Gefell for both indoor and outdoor applications. Drawing on more than a decade of SPL experience in surround miking technology, SPL Atmos was developed as a reference system for transparent, coherent and phase-stable surround recording, free from dependency on any digital storage or transmission format.
At the heart of SPL Atmos is the Atmos Controller, which integrates five matched, remotely controllable microphone preamplifiers, an internally generated LFE channel with level control, and comprehensive monitoring facilities including headphone output and PPM metering. The design focus is deliberately streamlined, concentrating on essential functions to reduce complexity and cost while preserving maximum audio quality. The preamplifier section ensures identical gain behaviour across all five channels, maintaining precise spatial imaging and accurate room representation.
Each microphone preamplifier is based on SPL’s Triple Gain Stage architecture. The first stage employs a Lundahl input transformer for galvanic isolation and passive 1:5 voltage amplification. The following stages provide active gain and DC offset compensation using SPL ServoDrive technology, which continuously detects and minimises DC offsets between signal paths. By reducing offsets to between 0 mV and 2 mV, noise, distortion and tonal coloration are minimised, resulting in extremely transparent and uncoloured amplification ideally suited to high-resolution surround capture.
The ASM5 microphone system uses five carefully selected and matched Brauner VM1 large-diaphragm capsules, with each microphone head adjustable over a ±90 degree range to allow precise spatial alignment. The INA5-R system, produced by Microtech Gefell, employs five matched M930 microphones, each independently adjustable to achieve optimal positioning. In addition to these dedicated arrays, SPL Atmos also supports custom microphone solutions, offering parallel balanced XLR and DB25 outputs for maximum flexibility.
Operational features include illuminated, relay-switched controls with gold-plated contacts throughout. Each channel provides phantom power, pad, phase reverse, low-cut filtering, insert points and tape send and return functionality. A unique five-layer gain control system ensures that any gain adjustment preserves the relative level relationships between all microphones. A Master Gain control allows simultaneous motorised adjustment of all five preamps, which is critical when gain changes are required during recording without compromising spatial coherence or phase stability.
The LFE channel is automatically derived from all five microphone channels, with a fixed crossover frequency of 80 Hz and adjustable output level from −32 dB to 0 dB. Output levels are displayed via PPM meters ranging from −48 dBu to +9 dBu in 3 dB steps. The SPL Atmos system operates entirely in the analogue domain, ensuring long-term compatibility and independence from evolving digital formats.
Features
- Five matched high-precision microphone preamplifiers with identical gain behaviour
- SPL Triple Gain Stage design with Lundahl input transformers
- ServoDrive technology for minimised DC offset, noise and distortion
- Five-layer gain control with master gain adjustment
- Integrated LFE channel with level control and fixed 80 Hz crossover
- Fully analogue signal path for format-independent operation
- Support for ASM5 and INA5-R microphone arrays and custom microphone solutions
- Parallel balanced XLR and DB25 outputs
- Illuminated switches and relay-based signal routing with gold-plated contacts