500 series modules

It had to happen.

One day, as one of the few manufacturers of consoles with 500 series support,
we simply had to design 500 modules. This day has come.

We’re proud to introduce the first of our 500 series modules.
More modules are in the works and will be released over the coming months.


4-band Hybrid Equaliser


Helium combines capacitor based EQ circuits and filters with inductor based EQ circuits.

Helium is the combination of our
Carbon and Iridium EQ, with extra filter circuits added.

Helium is a full Class-A, discrete design, and all components have been carefully chosen and matched to provide an extremely musical sound.
This is definitely not a “clone” or “copy” (we at Interphase Audio do not build clones or copies of anything).
Like all our products, Helium is unique and features great sound and straight forward functionality.

The four bands have large overlapping frequency controls, making it well-suited for minimising problematic frequencies, or giving an extra boost to others.
The HF and LF band can be used as either bell-curved EQ or as hi—cut / lo-cut filter.

Each band can be cut or boost with as much as 15dB per band.


• Input impedance: 30kohm
• Common mode rejection: 80dB
• Distortion: 0.001% (+4dBu output, 1kHz)
• Frequency response: 7Hz to 70kHz (-3dB)
• Boost / Cut range: +/-15dB (continuously variable)
• HF Frequency: 1.2 kHz - 22 kHz (continuously variable)
• HF Frequency switchable to sweepable Hi-Cut filter 1.2 kHz - 22 kHz
• HMF Frequency: 1.5, 3, 5 6, 7, 8 kHz (stepped)
• LMF Frequency: 125, 250, 500, 1k, 2k, 4 kHz (stepped)
• LF Frequency: 25 Hz - 440 Hz (continuously variable)
• LF Frequency switchable to sweepable Lo-Cut filter 25 Hz - 440 Hz
• Filter Q: 1.2 (just over 1 octave)
• Maximum input level (500 module): +28dBu
• Maximum input level (51x module): +32dBu
• Maximum output level (500 module): +28dBu (10k load)
• Maximum output level (51x module): +32dBu (10k load)
• Nominal input and output level: +4dBu (electronically balanced)
• Output impedance: 100 ohm
• Noise floor (typical, unweighted, EQ on): -80dBu
• Noise floor (unweighted, EQ off): -100dBu
• I/O connections (Rack XLRs): pin 2 +, pin 3 -, pin 1 ground
• Current requirement: 135mA (maximum) per rail
• Size and weight: Standard 500 Series, 0.4 kilos

is available as 500 series module or as 51x series module.
To find out more about the difference between 500 and 51x modules, check our
500 page


What are Inductors ?

Inductors are wires wound around a coil that provide a form of frequency-dependant resistance. When they saturate, they bring out beautifully musical harmonics that give your tracks the silky-smooth, polished sound that has made classic consoles and equipment so desirable for over sixty years. This is what makes them different from capacitor-based EQ designs, which do a great job at surgical equalisation. But it has always been up to Inductors to provide the tone.

While some of the inductors we use are off-the-shelf, we have choosen to also use custom inductors. This attention to detail in controlling variables such as the winding and core materials in relation to the surrounding circuitry allows our Inductive EQ’s to capture the classic sound, while at the same time be up to todays standards in sound-quality and noise level.

IP211 layout

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