Originally Posted by TimJo
A couple things I noticed reviewing the preliminary BOM and the schematic.
1.) CM2 appears to have been removed from the circuit, but it still shows up on the BOM.
2.) The labels for RB13 and RB14 appear to have been swapped on the MiniMax as compared to the regular Max, so the BOM should be updated to reflect this. (Or maybe you'll want to revise the schematic and the silk screen on the production run for consistency's sake?)
3.) CM3 now specifies a 470μf capacitor, which is a change from the 330μf on the Max. Is this correct?
Otherwise, things look good to me. I plan to put in an order with Mouser and Digi-Key tomorrow.
CM3 is correct. It's a bit more safety factor than is probably needed under normal circumstances - resulting in something like a 45 second delay (from memory w/o a stopwatch). However, there are various scenarios - testing, setup, kids with itchy trigger fingers - where turning the amp on and off within a minute or so will result in less than half the delay time. With the 330uf capacitor, cutting that delay time in half gets into the danger zone.
I hope this increased delay doesn't irritate some folks, but the tubes aren't at their best before several minutes/half-hour, anyway. BTW, I've used 470uf on every productoin MAX I've built. Note that this is also tied to RM2 at 1MegaOhm. If you adjust RM2, then CM3 must change as well to result in the same RC product. So, we're really recommending an RC product of RM2 and CM3 of 470ohms-farads.
CM2 is a good catch - we'll have to get an explanation from Colin on that one. He's probably decided that it's redundant.
Likewise, the RB13/RB14 swap - a good catch. My guess is that we'd need to correct the silkscreen on the production board. That would keep things consistent with the regular MAX. Again, we'll see what Colin suggests.