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8
Operating The C valve
Setting a Good Level
One of the most important fundamentals of good audio engineering is setting proper levels. Even on a small typi-
cal mixer, or basic multi-track recorder, there are several controls that affect the level of a signal as it makes it’s
way from your sound source to your speakers and then, ultimately, the level of your headphone or monitor sys-
tem. These include pre-amp gain, EQ, aux sends and returns, channel fader level, bus or group levels, and final-
ly, the master fader. That’s not to mention the level of the 5:15 train on its way to Pennsylvania station who’s
thunderous crossing horn can be picked up from 5 miles away while miking a nylon string guitar, despite the use
of double moving blankets over the windows of your project studio. But that’s another story with another set of
disciplines. Start off by being aware that anytime you change any control in the audio path, you are probably
affecting gain somewhere. Then, be sure to carefully monitor the levels on your input and output meters to avoid
a clipped signal with too many peaks. Also, remember your ear is the most sophisticated and calibrated piece of
test gear you have. So, setting a good level should be approached from a technical point of view, and then con-
firmed, by a creative point of view.
INPUT GAIN – Control Knob
As the name implies, the INPUT GAIN is used to set the level of the input signal. The
rotary control knob provides a range of gain from +6 to +60 dB. The C valve can accept
levels from most microphones when the MIC/INST switch is set to the MIC position.
When the MIC/INST switch is set to instrument, the C valve can accept signals from
instruments or line level sources. Once you set the MIC/INST switch to the proper posi-
tion, you can use the INPUT GAIN control to adjust the level of your input signal. It is a
good idea to start with the level low and raise it up as you need. Be sure to monitor the
input LED VU METER and try to set the INPUT GAIN control so that the meter reads +0 to
+6dB. If you see the OL LED light you are “Over–Loading” and the sound may become distorted. If this happens,
simply back down on the INPUT GAIN control until the OL light stops flashing.
LED VU METER – Input Level
To monitor the signal being presented to the C valve’s input, there is a six-segment LED-bar VU
meter indicating –20, -10, -6, 0, +6 and OL (OVER-LOAD). The level displayed on the meter will be
affected by the MIC/INST switch so be sure that you have that set to the correct position for your
sound source. The LED VU METER features “VU” ballistics, which means it reacts to the signal
based on an average level. Use the VU METER when you are setting your initial input level with the
INPUT GAIN control. Try to set the INPUT GAIN control so that the meter reads +0 to +6dB. If you
see the OL LED light you are “Over–Loading” and the sound may become distorted. If this hap-
pens,simply back down on the INPUT GAIN control until the OL light stops flashing.
ANALOG VU METER - Output Level
To monitor the signal being sent from the C valve’s OUTPUT, there is an ANALOG
VU METER with a scale from infinity to +4dB. The level displayed on the meter will be
affected by the MIC/INST switch so be sure that you have that set to the correct posi-
tion for your sound source. The ANALOG VU METER features “VU” ballistics, which
means it reacts to the signal based on an average level. Use the ANALOG VU
METER when you are setting your output level using the VOLUME control. Try to set
the level so that the meter reads about 0dB. If you see the needle stay all the way to
the right, you are “Over–Loading” and the sound may become distorted. If this hap-
pens, simply back down on the VOLUME control until the meter reads about 0dB.
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