The Iron Age V2 is a go-to tracking, mixing, or mastering equalizer featuring two channels of versatile, musical EQ in a one rack unit space. It features a proportional Q, bridged-T circuit topology with fully symmetrical active boost and passive cut, true bypass, and an all-discrete signal path. The output amplifier drives a custom wound Cinemag transformer.
Each equalizer channel is a three-band, selectable frequency design using two hand-built discrete op amps for gain. There are 18 center frequencies divided into three bands (Low, Mid, and High) as shown below:
Each band features up to 12 dB of reciprocal boost or cut in stepped increments of 2, 4, 6, 8 and 12 dB using a bridged-T filter design. The same filter bank is switched between the feedback loop of the amplifier in boost and a passive circuit in cut, which ensures that the boost and cut points are completely identical.
Passive circuits are separated by discrete transistor buffers, which contribute a unique character to the tone of the unit.
The bridged-T circuit implementation also features a proportional Q: as the amount of boost or cut is increased, the bandwidth of the filter is adjusted by a switched resistor to become more narrow. This allows for a wide range of use from broad-brush shaping to careful tone carving, but ensures that the filtering is never harsh and always musical.
The Low and High bands can be switched between peaking and shelving behavior. In shelving mode, the frequency response hits the indicated boost or cut level at the selected frequency and stays elevated or reduced through the extent of the audible range. This allows for musical shaping of the high and low extremes of the audio spectrum.
In Master mode the maximum gain range is reduced to +/-3 dB on all bands and keeping the proportional Q behavior. This gives fine control for bus or mastering work.
Additionally, the EQ features a switchable band-pass filter with -3 dB points at 60 and 16k Hz.
The module has a balanced transformer-less input stage using a third discrete operational amplifier.
The V2 uses the original M2 discrete operational amplifier, designed and built by us.
User review video
EQ Frequency Response
Curves plotted with actual data from a production V2.
Response curves on Tracking Mode with high and low bands set to shelf: