Iron v2 Red/Black
The IRON Mastering Compressor combines the sonic advantages of legendary vintage tube compressors with the benefits of SPL 120V technology in a single device. The result is a pleasant, melodious, musical compression behavior that is inspired by the classics of the early days of broadcasting, yet very flexible and perfectly adapted to the needs of modern mastering studios and productions.
IRON gives every signal power, size and depth - without being intrusive.
The concept
The basic concept of the IRON Mastering Compressor is a variable-bias limiter/compressor. However, the integration of new technologies has improved this concept in key respects. IRON works on the principle of the bias-controlled remote cutoff tube. A sharp cutoff tube with a steeper characteristic curve is connected in parallel.
Depending on the signal amplitude, one or the other tube is used for signal processing/limiting. This is positively reflected in a balanced sound and controllable settings of the control parameters. All four tubes in the IRON are a set specially matched to the overall system.
Components
The Wathen CryoTone™ 12AX7-WCM long plate tubes are not only a perfect match - they are also the perfect complement to the selected 12AU7 tubes.
The tubes are integrated into the IRON's signal flow via special Lundahl-manufactured, symmetrical high-level dual-core mu-metal-iron transformers.
An independent forward-regulated vactrol opto-resistor limiter circuit in the control path of the variable-bias tube circuit absorbs extreme signal peaks and thus ensures that the reverse-regulated tube circuit develops its full sonic potential.
Thanks to SPL 120V technology, tube compressor technology in the IRON sets new standards.
So many knobs
Input
The input level can be switched in a control range of +/- 12 dB in 2 dB steps. Increasing the input level leads to more intensive compression.
Tip: For highly compressed audio material with a lot of information in the lower frequency range, lowering the input signal with the input switch allows the compressor to work much more relaxed.
Output
The output level can also be adjusted in a control range of +/- 12 dB in 2 dB steps. This allows the audio level to be raised again after compression.
Attack
The attack time determines the response time of the compressor. The attack time parameter can be set in six stages from slow to fast.
Release
The release time is the counterpart to the attack time. The Release parameter determines how quickly the compressor completes a control process. The release time parameter can also be switched in six stages from slow to fast.
Threshold
The threshold determines the level at which the compressor starts to compress. Once the set threshold value has been exceeded, the compressor starts processing. Only signals whose level is above the set threshold are controlled. Signals with a lower level are not processed.
The threshold of the IRON can be set in 41 steps using a detented potentiometer.
Rectifier
The tube stage is controlled via a rectifier circuit. There are six diode control characteristics, which are generated by germanium, silicon and LED diodes or combinations thereof. The attack and release times vary depending on the selected rectifier
rectifier circuit selected.
Side-chain EQ presets
Side-chain filters can be used to influence the response of the compression to certain frequency ranges. This is also referred to as frequency-selective compression. The side-chain filters are only located in the control signal path - not in the audio path.
The IRON Mastering Compressor has a six-position switch that allows you to choose between the Off position, four side-chain filter presets or an external side-chain insert.
Side-chain insert
The external side-chain insert is activated in position 6 (Ext). An external stereo equalizer can be integrated into the side-chain signal via the rear insert send and insert return. Custom filter curves can be created to change the response of the compression to certain frequency ranges.
The side-chain equalizers in the IRON Mastering Compressor only process the control signal - not the audio signal! If no external equalizer is connected to the side-chain insert or if the send and return of the side-chain insert are not bridged with a cable, the audio signal in the IRON is interrupted when the switch position (Ext) is selected.
Tube bias
The tube bias can be set in three stages: Low, Mid and High. The tube bias is the voltage applied to the tube grid. The higher this voltage is, the less audio signal reaches the anode of the tube from the cathode - the stronger the compression.
The modulation of the bias voltage is the sum of the parameters Threshold, Rectifier, Side Chain EQ, Attack and Release.
Tubes
IRON uses four tubes in the circuit. One pair connected in parallel for each channel. To achieve mastering-quality sound and performance, it is necessary to use the best tubes available. But it is not only crucial to use perfectly matched tubes - they should also retain their technical values for as long as possible. That's why IRON is equipped with matched 12AU7 tubes, which are combined with pre-selected, perfect pairs of Wathen CryoTone™ 12AX7-WCM Long-Plate tubes at SPL.
The Wathen Audiophile CryoTone™ tubes are cryogenically treated tubes. Cryogenics deals with the question of how to reach low temperatures and how materials behave at these temperatures. Cryogenic treatment changes the molecular structure of electronic components by reducing or eliminating structural irregularities in the material. Wathen uses a cryogenic treatment process specifically designed to maximize all aspects of audio tube sonic performance. Wathen CryoTone™ 12AX7-WCM Long-Plate tubes offer unparalleled soundstage, depth and frequency spectrum. A consistently silky, clear and big sound image with the lowest noise floor and extended life.
IRON combines the best of modern technology and classic vintage magic.
Even more knobs
Link
By activating the Link function, the parameters Threshold, Bias, Attack, Release, Rectifier and Side-Chain-EQs are controlled from the right side (channel 2). In link mode, it is no longer necessary to make these settings on the left side (channel 1).
When the link is active, the IRON works with a summed side-chain control signal. The signal from the right channel then also influences the compression on the left channel - and vice versa. If the link mode is not active, the left and right channels of the IRON work completely independently of each other.
Auto Bypass
Channels 1 and 2 are activated using the large, illuminated, round switches. In Auto Bypass mode, the channels are automatically switched on and off, allowing a more objective assessment of the processing. The interval control is used to adjust the time window of the automatic auto-bypass.
AirBass & Tape Roll-Off
The compressor is followed by a passive filter network with two equalizer presets: AirBass and Tape Roll-Off.
The AirBass filter boosts low and high frequencies by approx. 1.5 dB, while the Tape Roll-Off filter emulates the typical frequency response of a tape machine.
VU switch
The toggle switch with three positions can be used to select whether the gain reduction or the output level (0 dB and + 10 dB) is displayed in the VU meter.
Recall
The threshold is set using a rasterized potentiometer. All other functions on the IRON are operated via switches and are therefore also recall-capable.
The 120V technology
120V technology is SPL's reference technology. It is unique in the world of audio because it works with a DC voltage of 120 volts. This corresponds to four times the operating voltage of IC-based semiconductor operational amplifiers.
The highest possible audio quality requires the highest possible audio operating voltage.
The 120V technology works with +/-60 V. In order to handle such a high voltage, SPL has developed special proprietary operational amplifiers that can operate with a DC voltage of +/-60 V - the SPL 120V SUPRA operational amplifiers. This high voltage would destroy conventional components and operational amplifiers.
The 120V technology achieves exceptional technical specifications and sonic advantages. Technically, in terms of dynamic range, signal-to-noise ratio and clipping resistance. In terms of sound, in terms of richness of detail and an absolutely relaxed listening experience.
Incidentally, the “120V” in the name of the technology has nothing to do with the local mains voltage from the socket. It refers to the operating voltage in the device with which the audio signals are processed.
The mains voltage from the socket is transformed to the required secondary voltage in the device's internal linear power supply unit with toroidal transformer. Rectifiers convert this AC voltage into the DC voltages required in the audio device.
Technical data
Analog inputs and outputs; XLR (balanced)
- Maximum input and output level: 32.5 dBu
- Input impedance: 20 kΩ
- Output impedance: 75 Ω
- Frequency response (-3dB): 10 Hz to 40 kHz
- Common mode rejection (0dBu, 1kHz): > 80 dBu
- Crosstalk (1 kHz): -108 dBu
- THD (+10 dBu): 0.002 %
- Noise (A-weighted): -98 dBu
Internal power supply; linear power supply with shielded toroidal transformer
- Operating voltage for analog audio electronics: +/- 60 V
- Operating voltage for relays and LEDs: + 12 V
Power supply unit
- Mains voltage (selectable, see fuse chamber): 230 V AC / 50; 115 V AC / 60 Hz
- Fuse for 230 V: T 1 A
- Fuse for 115 V: T 2 A
- Power consumption: max. 60 VA
Dimensions & weight
- W x H x D (width x height x depth): 482 x 177 x 300 mm
- Weight of the device: 11 kg
- Shipping weight (incl. packaging): 12.9 kg