I've been using these strings for 10-15 years, but the last 20 sets ordered from here have all had issues with the 0.026 D string. Within an hour of installation, the string is muffled. Within 2 hours, it's completely dead. It seems the windings collapse at the saddle.
It happens to all my guitars, it's not a technique thing as I've happily used these strings for years and it's only the one string that fails.
It may be a bad batch, but I had quality problems with the Pyramid Gold set too - it looks like Pyramid's manufacturing isn't what it used to be.
A shame, but I'll be spending my money elsewhere as it's not worth the risk.