Amp internals

[ICBM]

I know people like to see tidy wiring but in fact having every single wire cable tied every inch can make an amp a pain in the arse to work on, especially if you need to work on it while it's running.

+1

One of the nice things about many PCB amps is that if you're careful, it's possible to run the amp with the PCB out so you can troubleshoot both sides of it - although getting there can take a bit of time!

As Misty pointed out worse things are PCB mounted valve bases, PCB mounted pots, valves hanging upside down with no restraints, 1\4 sockets used for speakers, crap impendence selectors which are so bad they have an impedence of their own.

Actually inadequately-rated/supported PCB-mounted power resistors cause more problems than all those put together in my experience - with the exception of old impedance selectors which can be a blown transformer waiting to happen...

PCB-mounted preamp valve sockets are never an issue unless they're the junk white plastic ones used by Marshall, Trace Elliot and a few others in the 90s, which actually melted and shrank! The modern brown ones you find in anything from an Epiphone to a Mesa are fine. With PCB-mounted power valve sockets the usual cause of problems is arcing around the PCB traces, rather than a fault in the socket itself. Even this could be due to the board getting cooked by the heat and becoming conductive, so it's more an issue of board quality than the socket.

I know we use things like 1\4 jacks and kettle leads on amps for legacy reasons but any new decent design wouldn't.

What's wrong with kettle leads? Apart from the fact that there is no physical retention so they can get tugged out.

I agree 1/4" sockets shouldn't really be used for speakers, mainly because musicians will mix them up with guitar cables, but at up to 20W or so it barely matters, and as long as you use proper speaker cables, not at up to 100W (at least into 8 or 16 ohms). Beyond that the connector rating does come into it, which is why Speakons should be the standard for bass amps of greater power and often 4-ohm loads.