The small details of design

[fossilshark]

Hello all! It is time for my annual noob post!

I am finalizing the design for what I will consider to be my "flagship" series amplifier. I am focusing in on the little details. These are the questions I have on my mind:

For the output tube sockets I want to mount them directly to the chassis for mechanical stability, and use the long pin sockets (20mm lead length I think) to have as much of a gap between the sockets and PCB as possible. Is an approach like this necessary for the preamp tubes? Would I be OK soldering the standard Belton style preamp tube sockets directly to the PCB or should I try to extend the leads? My concern is if I extend the leads by soldering on wire it will have the same thermal cycle issue as mounting it directly to the PCB.

Does anyone know anything about Faston connectors? The units I repair at work (and modern guitar amps) use them often to connect the xfrmers to PCBs. I am having a hard time finding a part number for the PCB mount spade, wire spade, and matching crimping tool. Any suggestions on what part numbers are readily available with matching crimping tool?

Lastly, and this is a shot in the dark, I am implementing a microcontroller to handle fault detection, FX loop switching, main power relay, and hours ON counter for when these amps inevitably come back for service. Does anyone have any suggestions for the best way to monitor faults on the B+ line? I am sure there is a better way of doing it than using a resistor divider to drop the voltage to microcontroller levels.

The goal is for an amplifier that will last at minimum 20 years of up time (the lifespan of electrolytic caps), and I am thinking the warranty will be "everything except the output transformer" type deal. I know a full warranty on a guitar amp is absolutely stupid from a business standpoint but hey, I want to be the Snap-On of guitar amps.

Any advice on this endeavor will be greatly appreciated. Thank you guys so much for all the knowledge over the years, I would not be where I am now without this forum.

[acheld]

I don't know the specs/details of Faston connectors, but I have used them successfully.  I'm probably not the crimp specialist here -- can barely tell you the difference between F crimping and 2D crimping.   Newark and Mouser have loads of them.  TE is the original manufacturer, and of the crimp terminals I've used, they seem to be best, especially compared to "Amazonia" type connectors.

This may not work for you, but I've largely abandoned large e-caps in the power supply for guitar amps, using film caps in their place.   I have not yet had one fail in the past decade.  They are bigger, for sure, but nothing a good size doghouse can't take care of.  Just an idea.  About the only place I use electrolytic caps in guitar amps is the cathode bypass cap for a triode. 

[shooter]

The goal is for an amplifier that will last at minimum 20 years of up time

implementing a microcontroller to handle fault detection, FX loop switching, main power relay, and hours ON counter for when these amps inevitably come back for service.

having worked on complex systems for a living, the more complex the circuit, the more points of failure a system has.
most of my service calls were failures in the fault detection circuits, not failures in the actual circuit.

preamp sockets directly to the PCB should be fine, most fails on sockets/pcbs happen when bad things happen, not under normal design operation

[Banjan73]

Think my basic point to point amps will almost "last forever".