I already had a V6, a V-type preamp and this week I bought a Hexavalve and a NOS V4. I got the V4 from www.britishaudioservice.com and I needed some replcement knobs for the V-Type preamp. The plastic ones broke. While I was on their website, I saw a CD of all the Trace Schematics and Service manuals etc. I figured if I'm gonna own this many Trace produccts, having the service manuals and board schematics isn't a bad idea so I got it. This thing has a ton of info on it. I highly reccommend it to anyone who works on their own amps.