The importance of quality constructed headshell-to-cartridge wires cannot be overstated. The precise but delicate signals coming from the phono cartridge make a critical transition to the tonearm wires via the small set of wires which connect the two. Too many times these wires are corroded, suffering from electrical oxidation, and weak inferior joints.
Most stock headshell/cartridge wires are mass produced in the factory. The easy (and least expensive) way is to merely crimp the cartridge connectors to the ends of the wire. The crimp pierces the insulation on the wire and hopefully makes contact with the wire strands in the center. This was and continues to be a common practice for mass produced cartridge leads. Recently another form of this mass production has come out whereby the wire ends are stripped and the connector is slipped onto the wire then crimped. In this design the crimp doesn't actually pierce the insulation. Instead the bare end of the wire is loose but positioned to make contact with the cartridge connector. The trouble with this method is that most of the wire strands don't actually touch the connector! At most a strand or two make the only contact. What's worse is with these types of cartridge leads the shoddy connection is covered up with shrink tube insulation. These are easily identified by insulation that runs 'to the tips'. (Which is also a needles feature).
Attached are some photos of this new type of faulty cartridge lead construction.
The older style of crimped on connectors - the type where the connector pierces the insulation - is also prone to fault over time as the strength of the crimp weakens and separates just enough to break the metal-to-metal connection. Here's a picture of this type of early crimped on construction. These rarely have any insulation covering the joint.
So what you should be looking for in a quality cartridge lead is a clean soldered joint between the wire and the connector. This type of construction won't separate, pull apart or weaken over time. And it ensures 100% of the wire strands are making permanent contact with the metal connector. Of course, using high quality wire, strong round barrel connectors, and premium silver based solder contributes to the signal quality. Here's an example of hand assembled cartridge wires with these features.
All of the cartridge wires used in our products are constructed this way: high quality multi strand wire joined to the cartridge connector via premium silver based solder and then protected with insulation. We never use mass produced cartridge leads and certainly not ones with inferior crimped connections.