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©2005 Diamond Audio Technology. All Rights Reserved
©2005 Diamond Audio Technology. All Rights Reserved
GAIN SETTING BRIEF (cont.)
Note:
If precision gain setting of individual crossover channels or sub woofer amplifiers
is needed, choose a sine wave frequency that is in the center of the frequency response of
that output or amplifier. Example: If setting the output level of a low pass crossover
output that has a bandwidth of 30 - 100 Hz, use a 60 Hz test tone to set this output level.
This procedure will give you a system with the maximum signal to noise ratio. It is based
on test tones which are constant, not actual music. Music is not a constant signal and
therefore doesn't clip constantly at certain levels. Because of this, a system that has the
maximum signal to noise ratio may not seem like it plays very loud.
In this case it may be necessary to add some gain overlap to compensate for the low
output of the system. Adding gain to the amplifier will lower the signal to noise ratio of
the system and raise audible distortion, but it will raise the overall output of the system
to a more acceptable level if done correctly.
If the overall output of the system is not satisfactory, retune the system using a -3, -5, or
-6 dB test tone. This will raise the systems signal voltage and gain 3 - 6 dB of output.
Either of these settings are an acceptable compromise. In some cases a -10 dB test tone
is applicable, but not recommended most of the time. When using these test tones to
tune the system, be aware that they may drive the speakers past their mechanical limits.
If this happens, they gains will need to be turned down to protect the speakers from
damage.
If sub output is not satisfactory, but the mids and highs is, adjust by lowering the mids
and highs output level. If the mid and highs output is low, turn the sub gains down. Do
not adjust any of the gains above the maximum undistorted output levels achieved by the
procedure.
GAIN SETTING BRIEF (cont.)
8. Turn the head unit volume down slowly until the clipping disappears. Make note of
the location of volume before clipping. This is the maximum undistorted output
level of the head unit.
Note:
Output voltage can be read with the DMM on the 20 V AC scale by
attaching the meter to the alligator clips on the custom adapter cable.
9. Remove the custom adapter cable from the head unit and connect the head unit to
the next component in the signal path. (EQ, line driver, crossover, amplifier,
etc.)
10. Repeat above step 1 - 8 for each component in the signal path in order from the
head unit to the amplifier/s. Be sure to leave the head units volume at the
maximum unclipped output level discovered above.
a. If the component has an input level control as well as an output level
control: Turn the output level to approximately one quarter up. Slowly increase
the components input level until the sine wave clips and the decrease it until
there is no clipping. This is the maximum signal level the inputs can handle.
Slowly increase the output level as high as possible without clipping and move
to the next component.
b. If a component with only output level controls does not clip, leave the level
control set to maximum.
c. If the component does not have any level controls, it should pass the signal
without clipping. Test to ensure there is no clipping on this component. If
clipping does occur, lower the output level of the component before this one
until clipping stops. If the head unit is before this component, consider
replacing this component rather than lowering the head units output.
11. Set the gains on the amplifier/s to the minimum. Connect the Oscilloscope probes
to one channel on the amplifier. Slowly increase the gains on the amplifier until
the signal clips and then back it off until the clipping stops.
a. If the amplifier clips with the gains all the way down, decrease the output
level of the component before the amp until clipping stops.
12. Repeat step 11 for each amplifier gain in the system.
