That Depends on the input voltage and Current of your Suply.Originally Posted by gaz_the_chav
A super brite LED uses 3V @ 30MA so on a 12V line your max is 4 as Shown in this tut. There are other ways to wire up Leds to help get more in a given voltage, but then they'll draw more current.
Also you'll only get so so results if you hook a Cold Cathod tube up in place of the LEDs. So CC tube don't light instantly so you'll miss the short pulses from the music. Plus there are sevral sound responsive CC drivers out there for resonable costs. It's easier just to use one of them.
I also noticed that in the comments at the bottom of this tut Pasteler0 noted that during his testing his "Tip31" stoped working, and had to be replaced. I'm going to guess what caused this and explain how you ca avoid it. A stero Head phone plug has three rings on it one for righ channel, one for left, and one for Ground. The Jack has three springs that contact the rings to transfer the sounds as voltages. When you plug ito the jack, some or all of the rings short together, not a big deal for headphone speakers they just jump a bit, and the sound card is protected from this short. In this tut there is no protection for the "TIP31", so when the you plug it in while the power is on you "OverDrive" the transistor by shorting to +12V. So if your going to use this blinky curcuit, install and uninstall it with the power off unless you like replacing Transistors.
It's a neat, and nicely done Tut though!!!
CrazyBillyBob