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The SPL Iron Mastering Tube Compressor combines not only the sonic virtues of legendary vintage tube compressors with the advantages of the High Dynamic 120V operating voltage in a single unit. It is also perfect for the needs of modern mastering studios and sets a new benchmark in terms of tube compressor technology, with the innovative implementation of a parallel dual-tube circuit. Thanks to the especially conceived Mu-Metal iron transformers, the signal of each channel is split across two different twin-triode tubes. The combination of the different response curves of both tubes results in a transparent and musically pleasant compression. Additionally, peak signals of the control voltage are limited by a feed-forward resistive vactrol-opto-isolator. Thus, the output signal remains lively even with a high gain reduction. The compression is only noticeable with extreme settings.
Mastering is not the only domain where the IRON sets new standards. It can also be used to process individual instruments, like vocals, bass, guitar, strings, etc. The IRON is also an excellent option for subgroups.
The IRON mastering compressor was conceived as a variable-bias limiter/compressor right from the start. However, the implementation of new technologies results in many improvements. Its basic operating principle as a variable-bias tube compressor was loosely inspired by the sonic and technical operation of Fairchild, Collins and Gates compressors, which used remote cut-off of tube biasing to achieve a well-balanced, well-compensated and musical compression.
However, the IRON compressor features a second sharp cut-off tube, a medium-variable bias triode, in its circuit design. This tube is connected in parallel to the remote cut-off tube and it has a considerably steeper characteristic curve. The tube used to process the signal depends on the amplitude of the latter. This results in a more well-balanced sound and more controllable settings of the parameters. The pair of parallel connected tubes has been specially matched for the IRON. In order to guarantee that tube selection and pairing is perfect, SPL use the Weigl Roe Test for PC. The optimal selection of the tubes guarantees that all IRONs have the same sonic characteristics.
The Tube Bias has three different settings. Together with the Input Gain of up to ±12 dB and the Threshold control, it allows the compression behavior of the tubes to be perfectly adapted to any material. The Attack and Release parameters have six different settings ranging from Slow to Fast. The times are not constant, they vary according to the Rectifier circuit selected: There are six different Rectifier settings available with different diodes (germanium, silicon, LED, mixed).
Moreover, SPL use Lundahl custom-made balanced high-level dual-coil mu-metal iron transformers in the signal flow of the variable-bias tubes, which add to the overall sound.
The second new technology implemented is the independent feed-forward resistive opto-isolator in the control path of the variable-bias tube circuit. Its function is to limit signal peaks and, thus, get a smaller THD (Total Harmonic Distortion) within the variable-bias tube section. The result is a silkier, more homogeneous sound in the higher frequencies of the music signal. This circuit has its own rectifier in the signal path. The optical control element does not work in the sense of an audio limiter, like in a conventional opto-compressor. It is built-in in the control path of the parallel connected variable-bias tube, not in the audio path itself. Time control parameters, like attack and release time, are adaptedand fixed to the variable-bias tube circuit.
The IRON compressor works as a feedback compressor when set to the variable-bias tube circuit and as a feed-forward compressor when set to the opto-control circuit.
Thirdly, the complex rectifier circuit is also worth mentioning, since it is the basis for tube control. You can use the six-position switch to choose either of the six different control characteristic curves of the diodes within the rectifier. Given the specific characteristic curve of its elements, the combination of germanium, silicon and LED diodes produces different behaviors and characteristics for the Attack and Release times.
The fourth exceptional feature is the comprehensive logical relay circuit that perfectly links both channels together, making the right channel the Master regarding Release, Attack, Threshold, Rectifier, Tube-Bias and Side-Chain EQ settings. In stereo Link mode, the Threshold, Tube Bias, Attack, Release, and Rectifier parameters, as well as the Sidechain EQs, are controlled with the right side (channel 2) of the unit. In contrast to the Dual-Mono mode, in stereo Link mode the compressor works with a sum signal. Thus, the stereo image is wider when working with the Dual-Mono mode on stereo material.
The Sidechain EQ is yet another option to adjust the Iron to the signal being processed in an optimal way. It allows you to choose between an external EQ or one of the four internal EQ presets. The EQ presets have a complex frequency response and have been conceived with different program material in mind. Only the control signal is affected, not the actual audio signal. In the Off position, the Sidechain EQ is inactive.
Both the left and right channels have separate illuminated activating switches. Further, in Auto Bypass mode you can use the Interval control to set a time frame during which the compressor automatically toggles back and forth between the processed and unprocessed signals. This makes AB comparisons between the original and compressed signals a breeze, besides making it easier to assess the settings in context.
The best gear advice always comes from those who use it the most. That's where you come in! Let the pro audio world hear your voice with a review of the SPL Iron Mastering Tube Compressor #17.1520.00113 (Used) . Once you submit your review, please check your email and verify your address to have it posted.
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