Built my Metro Amps JTM 45 kit over the weekend and it worked great from the first switch flip. I do have a few questions, but I first want to congratulate the Metro Amps team for assembling the best amp kit I've yet encountered. From the high quality parts to the excellent instructions and support, everything is simply top notch. With some prior experience building other vendors kits I can say without question Metro Amps is the best in the business by a long shot.
Ok, here's my questions:
1) Does anyone have a good method to safely tighten the Marshall-style toggle switch nuts? I've used everything from a pair of long needle nose pliers to a pair of snap ring pliers and they're just clumsy as all get-out. Is there a special tool available anywhere?
2) I noted that the JTM 45 has the mains fuse on the neutral line. I've been taught that the fuse & switch should always be on the positive / mains line to prevent current from being present after a fuse blow. I went ahead and built the amp fused on the neutral / commons line per your instructions but wondered if George or someone could explain why you do the circuit this way.
3) My internal voltages seem to be proportionally close to the chart included with the kit, but run 10 - 20% higher. In particular, my phase inverter voltage readings are much higher than you indicate in the chart. For example, pins 1 & 6 are 20%+ higher, and pin 3 voltage runs 85.5v, vs your chart showing 48v. I've triple checked my resistance values and all seem to be ok. Is the increased PI voltage a result of using your PI cap mod (i.e., bridging both cap pole on the PI cap can)? FWIW, my line voltage runs from 122 - 126v.
4) What was the reason for using a 330uf cathode cap on V1, rather than the original's 220uf?
5) I noted that you have the bias circuit grounded on the pot bus, rather than with the PT center taps, etc. I'm mostly a Fender guy and have always been taught to ground the bias circuit at the same PT stud as the CTs and never with the preamp. Is your method preferable to what I've been doing?
6) Finally, do you have a Metro Amps logo available? I hate to just have the amp "logoless".
Thanks again for a great product, I'm sure I'll be enjoying it for quite some time!