Top Panel Controls
Input Channel:
These switches are for
Œ
selecting which input channels feed the
respective channel pair's pre-amp and
output stages. CH1/2 can be set to direct
(1/2) or sum (1+3/2+4), while CH3/4 can
be set to copy (1/2), direct (3/4) or sum
(1+3/2+4). For 2-channel sources, connect
the source to CH1/2's RCA or speaker
level inputs and set CH3/4's input select
to copy (1/2), or use y-adapters/jumper wires and set to direct (3/4) to allow CH3/4's gain to be
used separately. For 4-channel sources, set CH1/2 to direct (1/2) and CH3/4 to direct (3/4). For
summing factory 2-way signals, there are several options that will depend upon the connected
speaker configuration. Example: For a 3-channel system from a factory 2-way source, CH1/2
would be set to sum (1+3/2+4) for full-range output to the main speakers, while CH3/4 would
be set to direct (3/4) to pass only the factory woofer signal to drive the subwoofer:
Input Sensitivity Range:
Two input sensitivity ranges are provided for each channel pair to
optimize source volume range while minimizing the gain required to achieve full power output
for best signal-to-noise. Choose the input range that will accommodate the source's maximum
output signal voltage without excessive clipping, 5V or 10V for low level (RCA) inputs, and 20V
or 40V for speaker level inputs.
Gain Adjustment with Clip LED:
Each channel pair has a variable gain with corresponding
Ž
clipping indicator, where the clip LED will dimly illuminate just before the onset of clipping and
become fully bright when the amplifier has reached full power output at clipping. When
summing, these gain adjustments should be used for matching relative levels so that the
combined signals sum as close to flat as possible or to the desired frequency response. Note
that CH3/4's gain adjustment will be bypassed if its input select switch is set to copy (1/2).
Filter Mode:
This switch selects the filter mode as either a high-pass (HP) or low-pass (LP)
crossover, and is bypassed when set to OFF (default). For smaller full-range or component
speakers, select HP mode to filter out lower frequencies below the chosen cut-off frequency.
For midbass speakers or subwoofers, use the low-pass (LP) setting to filter out unwanted
higher frequencies above the chosen cut-off frequency.
Filter Frequency:
When either the HP or LP filter mode is activated, this variable adjustment
sets the filter's cut-off frequency ( ) from 50Hz to 500Hz with a slope of -12dB/oct. Use this
F
3
adjustment to optimize speaker or subwoofer frequency response to what they can effectively
reproduce while minimizing the chance of being over-driven at maximum volume.
Level Trim:
When summing, and after setting gains and crossovers for appropriate frequency
‘
response, these adjustments allow the power output of CH1/2 and CH3/4 to be increased or
decreased independently by up to +/-6dB for final volume balance between them while
preserving the summing ratio established by the gains. See the 3-channel system summing
example in above, where CH1/2's level trim would usually be reduced to achieve desired bass
Œ
overlap from CH3/4 at full volume. Note that increasing level trim of channels already at
maximum power output will require re-adjusting gains lower to avoid clipping.
3
Œ
Ž
‘
L
ev
el
Freq
CH3/4
IN
L
ev
el
CH1/2
IN
CH1+3/2+4
OUT
Direct
Sum
Freq
CH3/4
OUT
Factory 2-way
Input
link300.4mini
Output
1/2
1+3/
2+4
1/2
1+3/
2+4
CH1/2
INPUT CH
CH3/4
INPUT CH
Sum
Direct
1+3/
2+4
CH1/2
INPUT
CH
FIL
TER
LEVEL
TRIM
CLIP
INPUT
CH
GAIN
CLIP
1/2
1+3/
2+4
1/2
3/4
5V
/
20V
10V
/
40V
OFF
LP
HP
(Hz)
50
500
(dB)
-6
+6
CH3/4
MIN
MAX
FIL
TER
LEVEL
TRIM
OFF
LP
HP
(Hz)
50
500
(dB)
-6
+6
GAIN
MIN
MAX
5V
/
20V
10V
/
40V