Lindell Audio Vintage OPA The “VINTAGE OPA” is our take on the classical vintage opamp Melcor 1731 – the predecessor to the 2520 The sound character can be described as smooth and punchy The “VINTAGE OPA” is pin compatible, plug & play ready for the 6X-500, 7X-500 and PEX-500 Rev.2 and 18Xs MKII