impedance makes it possible to connect multiple devices, like the SHA2, with high impedance to the output without having any significant effect on the quality of the signal. This is called bridging the output.
Wondering what impedance is? If you know about resistance you know, or I’ll tell you, resistance is a measurement, in ohms, of the amount of resistance to current flow in a DC circuit. Like a garden hose that is crimped. There is less water (current)) flowing in the hose because of the crimp (resistance)).
Impedance is the same thing but is used to describe resistance to an AC current flow. Why the difference? The resistance (impedance)) of an AC circuit is affected by the frequency of the AC signal but there is no frequency involved with a DC signal. The impedance of an amplifier input will be different for every signal frequency applied to it but a circuit which has only DC current will always be the same. When an impedance is specified it is usually for a frequency at the center of the range expected.
What about H1 and H2?
Notice that the input to the looping buffers have a set of jumpers, H1(H2), feeding them. These jumpers allow you to choose between the direct input feed to the SHA2 or the output of the LM1036 processor. By connecting a jumper between pins 1 and 2 of the headers the buffered output is simply whatever the input is. If the jumper is placed between pins 2 and 3 the buffered output becomes the processed signal provided to the headphone amplifiers.
Let’s say that you want to use your SHA2 to listen to the record level output of your amplifier because it does not have a headphone jack but you also want to be able to record the program you are listening to. Yes you could simply connect a ‘Y’ adaptor to the output and plug in the recorder. But what would happen if the cables to the recorder became shorted to ground. Now you loose the signal to everything connected to the recorder output. The looping buffer in the SHA2 will prevent the recorder form affecting your headphones if the recorder is defective.
Now let’s consider a situation where you have several power amplifiers that are connected to speakers in different areas. You want to control all the levels from one central location. By connecting pins 2 and 3 on the headers you can feed all the amplifiers from the SHA2 and have your monitor headphones too.
How about feeding one signal to a string of monitors for your band. Simply daisy chain the SHA2’s using the looping buffers. The possibilities are nearly endless. The choice is yours.
SHA2 • 6