Esoteric Audio Research / E.A.R. 660 – Tube Compressor Limiter. Made in England since 1984 by designer Tim De Paravicini. The EAR 660 Fairchild-type valve limiter-compressor is designed to limit or compress the signal with the barest minimum of interference below threshold, and give the most subjectively satisfying operation on high-level signals. The unit has the standard range of attack and release times, making it easy to use.

There is a three-position switch for balancing each half of the tubes – one can check all is well by making sure the meter reads zero in all three positions. Like a Fairchild, compression adjustment is done with the Input Attenuation pot and the Threshold.

There are two different threshold knobs on the E.A.R. DC Threshold varies the slope: at full anticlockwise the unit will gently compress, and at the opposite end it will hard limit at a 10:1 ratio.

The EAR 660 has input and output transformers designed by Paravicini, for wide bandwidth, and PCC189 triodes which are true vari-mu tubes that are long lasting and more easily obtainable than those found in Fairchilds.