The IGS Audio ONE Levelling Amplifier is a photo-optical compressor, referring to the legendary solution of United Recording Electronics Industries. It is an input and output transformer balanced, full tube device. The input of the system is worked with a Sowter 4383 transformer, the output with Edcor 15k/600. Two 6N2P-EW 6N1P-EW dual-triodes are installed on the audio circuit, while the compression circuit is equipped with the 6N2P-EW triode and the 6AQ5 pentode, which control the work of the T4BX photocell. On the front panel you can adjust the input sensitivity (GAIN) and compression threshold (PEAK REDUCTION). Additionally, you can select the operating mode between Compress and Limit. You can also set the meter to VU or Gain Reduction.

Inside the device are 4 tubes with 245V anode voltage. The system is mounted on a PCB, which results in shortening of connections inside the device, improves the bandwidth and stability. On the rear panel XLR connectors have been installed. The whole device is designed to work with a symmetrical 4dBu signal.

It is known that in the case of ONE LA the nature of the device depends on the T4B photo-cell. The original solution used the TELETRONIX electroluminescent panel, which illuminated the photo resistors. The idea of photo compression originating then is still cultivated today. IGS Audio has developed its own photocell equivalent to T4B called T4BX. The use of carefully selected components in the production of the photocell, and their individual measurement and matching, result in completely repetitive sound qualities of each device.