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To avoid massive build errors, make sure the BOM Revision you follow matches the Revision of the PCB you are building!! The VP25 No Input/Output (Stepped) is a kit comprised of every single part and component needed (sans opamp, input transformer and output transformer) to complete a VP25 microphone preamplifier. The VP25 is a single stage mic preamp for the 500 series format and is fully VPR compatible. The aluminum faceplate is wet painted and the aluminum L-bracket is yellow chromated. The idea behind this kit is for someone who has a vintage 312 card and wants to convert it to 500 series use. Besides the AP2622, AP2503 and 2520, there is really nothing worth salvaging. It should be noted that the original AP2622 is in an abnormally tall can. In fact it is too tall to be mounted standing up on the PCB. The best thing is to lay it down and secure it with a plastic wire tie. You will have to strategically place and drill holes for this but hey, it is DIY after all. This kit includes a Grayhill switch for stepped gain control. Kits using a Bourns potentiometer are also available for fully variable gain control. Complete VP25 kits with reproduction transformers can be found here