SPL Iron V2 Two-Channel Tube Mastering Compressor (Black/Silver) - Manual (Page 8)

8
Technical Aspects
Innovating Compression
The IRON Mastering Compressor is a variable-bias limiter/compressor from the basic
concept. Through the integration of new technologies, this concept gets significantly
improved.
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-cutoff
tube, a medium-variable Mu Triode, in its circuit design. This tube is connected in paral-
lel to the remote cutoff 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. To receive
mastering grade sound and performance it is necessary to use the best tubes available.
It is not only crucial to use perfectly matched tubes – they also need to stay true to their
specs as long as possible. Therefore IRON is equipped with matched 12AU7 tubes, which
get paired with preselected matched pairs of Wathen CryoTone™12AX7- WCM Long Plate
tubes at SPL. Wathen Audiophile’s CryoTone™ tubes are cryogenically treated tubes.
Cryogenics is the study of how to get to low temperatures and of how materials behave
when they get there. Cryogenic treatment modifies the molecular structure in electronic
components by reducing or eliminating voids and imperfections in the material. Wathen
utilizes a cryogenic treatment process that is specifically designed to maximize all
aspects of the sonic performance in audio tubes. Wathen CryoTone™ Long Plate versions
of the 12AX7-WCM have unequaled soundstage, depth and frequency balance. Silky,
clear and large from top to bottom with the quietest noise floor and an extended life-
span. IRON combines the best of modern technology and vintage magic. The tubes are
integrated into the IRON’s signal flow via special Lundahl manufactured balanced high-
level double core mu-metal-iron transformers.
An independent feed-forward resistive vactrol-opto-isolator in the control path of the
variable-bias tube circuit intercepts extreme signal peaks, ensuring that the tube cir-
cuitry achieves its full sonic potential.
A complex rectifier circuit is the basis for the 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 combina-
tion of germanium, silicon and LED diodes produces different behaviors and characteris-
tics for the Attack and Release times. Hence, compared to most compressors, the appli-
cation scope of the IRON is clearly enlarged, resulting in new possibilities regarding the
processing of music material.
A comprehensive logical relay circuit perfectly links both channels of IRON together, mak-
ing the right channel the Master regarding the parameters Release, Attack, Threshold,
Rectifier, Tube-Bias and Side Chain EQ.