SHA2 • 6
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.