Since solder is such a poor conductor, why use it?

Silver solder isn't pure silver - it's a mixture of metals with silver in it. The other metals mixed with it for what is called a eutectic mixture - this lowers the temperature of the mix to a point where it all melts.

And the reason silver is touted as better is that it has the lowest resistance among the elements. Whether the hype is true, I don't know.

One reason not to 'weld' parts together is that that would make it harder to remove the parts in case a repair is needed. Plus, like Czarivey pointed out, high temps would destroy everything.

Timrhu, yes solder is awful now. It cracks.

Joeylawn36111, There are very localized welders that would not influence the circuits.

Almarg, I've learned that too often dismissing the impact of improvements is entirely wrong. Electrical Engineering doesn't know everything.

Why don't you make a preamp asap.

09-25-15: Tbg
Timrhu, yes solder is awful now. It cracks.

I don't doubt your word if you have experienced that, but it needn't be so. Consider the hundreds of thousands and in many cases millions of solder joints in the avionics systems of military aircraft, which are accomplished mostly by automated soldering processes. Those seem to do ok, despite being exposed to extremes of vibration, temperature, and other environmental factors.

Regards,
-- Al

Less talk, more action. Just do it! Prove the world wrong. Make it so! make it magnetic too while at it. The world will be a better place.