Well, as far as Christmas LED's, and the idea that they would use a single diode to chop the sine wave into a half or a sine wave with clipped corners at that..... kind of doubtful. The LEDs would not flicker, they would actually strobe and I do not thing anyone is actually doing that. Add to that the fact that a full bridge rectifier is burned into silicon so the price is about the same as a diode anyway.
But even that is not a fix or acceptable because there will still be a significant 'off' band on either side of the zero crossing where no current will flow and the LED's will go out. If we assume the sine wave is transformed to 3 volts, a reasonable expectation to drive LEDs with, the 'no current passing' band of a silicon diode (any kind- this is controlled by the physics of the material, not man or human design) is ~.7 volts and it is on BOTH sides of the zero crossing, so you can quickly see that merely transforming and rectifying 115 VAC down to ~3 rectified (pulsed DC is what it is) power is still very unacceptable. A capacitor will help, and a resistor- capacitor - inductor would correct it but the better way would be to chop the AC into a much higher, square wave and then transform it, filter it with very small components and Viola! Perfect. And we have a name for those: It is called a power supply.
I do not have any of those LED Christmas lights and so have not seen the flicker but I would suggest finding out what they require for power, (to the LED strip, output power, not input power), cut whatever garbage they have in there to make them flicker.... er, I mean light, and buy a wall- wart that powers them up. A few bucks and all should be well. Again, I say this without seeing them; I do have some puck style LEDs inside my glass door cabinets in the kitchen and they use 46 volt DC power supply (he slaps his forehead with his hand). Ain't nobody gonna' find one of those, anywhere.
See what happens when we (and I mean we- me included) make everything about the price? We get it, all the way until it either does not work or does not work right.
It is also possible there are other, better brands of LED Christmas lights that do not do this but again, capitalism (and I am a loyal and firm (Easy Boys) capitalist), I just think it can and will run amok without other restraints.... just like these cheap lights). So maybe even the pretty inexpensive but not the dead- cheapest lights are also gone from the market.
Brian
...Well, I didn't really expect the count..that would be automatic for 50 cycles at 25 on and offs, but I did want to know if they flickered like the ones we get do.
It doesn't seem like it would be that expensive to put a few diodes and a capaciter in there to make a rectifier so they didn't noticeably flicker, but I guess the competition to save a few dimes per string of lights is just too much.
I think DSL is dying out over here, and for that I'm glad. It was faster than dial up but not as reliable. Frequent outages for me on rainy days. Cable or fiber optics seem the way to go now.
I guess satellite is still viable if you are remotely off the grid, but I've never tried it.