User guide
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FRONT PANEL CONTROLS - INDIVIDUAL CHANNEL CONTROLS
6) Line select / Mic Pad
This switch selects between the XLR and TRS connectors on the rear panel. When UP, the XLR connector is selected, when depressed the TRS jack is
selected. The two jacks are “normalled” together in that the XLR signal is available at the TRS jack if nothing is plugged into the TRS jack. This allows the
switch to do double-duty as a Line-select switch (if a plug is inserted into the TRS jack), or as a -20dB PAD switch for the XLR jack if nothing is plugged
into the TRS Line jack.
7) Polarity reverse
This switch reverses the balanced connections to the preamp circuit and therefore reverses the polarity of the input signal. This switch is sometimes called
“Phase”, or marked as “Ø” on other products, but the function is the same. It is used to change the overall polarity of the signal. This matters most when
the signal is being mixed with other signals. The overall sound of the mixed signals may change depending on the position of the switch. Try both positions
when mixing channels together (through the L/R mix controls)
8) Preamp Gain
This rotary control varies the circuit gain of the preamp. The minimum gain of the preamp is approximately 15dB, the maximum is 65dB. By using the
Line/PAD switch, a wide-range of input signals can be accommodated. This control should be used in conjunction with the Solo switch and Sig/Peak LED
to properly set the channel gain: adjust the Gain control so that the Sig LED is a strong Green intensity, occasional Red peaks are OK. By using the Solo
switch (#3), the channel can be monitored on the Level meters (#9) and heard in the headphones.
FRONT PANEL CONTROLS - MASTER & MONITORING CONTROLS
9) Level Meters
These meters allow the user to monitor the main L/R mix output, or individual channels by using the channel Solo switches. Normally, the meters are show-
ing the output level of the L/R mix (controlled by #11). When any channel Solo switch is pressed, that channel’s signal level is displayed on both meters
and the Pwr/Solo LED (#10) turns Red indicating that the meters are monitoring the Solo mix bus. The Solo mix is made up of all channels that have their
Solo switch pressed, so individual channels, or a mixture of channels can be monitored. The meters have a VU-response, and will show the average level
of the signal. The headphone system follows these meters, so anything that shows on the meters can be heard in the phones.
10) Power/Solo Indicator
This LED normally is Green, indicating that the unit is being supplied power (via the rear AC power jack). The LED will turn Red when any channel Solo
switch is pressed. This lets the user know that the meters are now showing the Solo mix level instead of the L/R mix output.
11) L/R Master Level
This rotary control sets the overall level of the L/R mix output to the rear-panel output jacks. The L/R mix is the sum of all of the channels, controlled by
their individual Mix and Pan controls (#1 and #2).
12) Headphone Level
This rotary control sets the overall level of the headphones. The headphones follow the Level Meters and normally monitor the L/R mix. If a Solo switch
is depressed, the phones then monitor the Solo mix bus.
13) Phone jack
This 1/4” TRS jack is used to connect headphones to the unit. The phones normally monitor the L/R mix, switching over to the Solo bus when a channel
Solo switch is pressed. Best results are obtained with studio-quality phones with an impedance of 30 to 75 ohms.
sp828 manual.indd 2/22/05, 11:06 AM6-7