Instruction Manual

Controls

The front-mounted Gain controls have 11 detents for easy matching of levels. The

Gain scale showsdB of attenuation from full gain, with positions for 0 (full), -2, -4,

-6, -8, -10, -12, -14, 18, -24, and ∞(full off). Attenuation is accurate within 1dB

(down to -14dB).

Gain Control Lockout

Provided with each ampliﬁer are two lockout knob caps. Carefully remove the Gain

control knob (A), as shown in Figure 9. Cover the opening by snapping in the lock-

out knob cap (B). The Gain control can no longer be adjusted.

Displays

The LED displays for each channel operate as follows:

LED Label Color Behavior

Power Green Main power supply active on this channel.

Signal Present Green Triggers at -36 dB below full output.

-20 dB Green Triggers at -23 dB.

-10 dB Yellow Triggers at -11 dB.

Clip Red Shows activity of Limiting circuit, which responds to

both clipping and to thermal overload.

Protect Red Flashes as ampliﬁer approaches maximum tempera-

ture. Illuminated steadily plus ﬂashing during thermal

muting. Illuminated steadily during non-thermal

muting.

Typical Power Up, Operation, Power Down Behavior

When the ampliﬁer is ﬁrst turned on, the green POWER displays will light up for

both channels, and there will be a 3 second turn-on delay, during which all red LEDs

will be bright (PROTECT and CLIP). If a channel will not come out of muting, it may

be responding to an excessive high frequency level at the input (see page 12,

“ProtectionCircuits”). Turning down the Gain controls (before you power up the amp

is best) allows the muting to release, and is always a good idea to prevent an unex-

pected input signal from overdriving the load.

Signal Level will be shown as the green Signal Present, -20dB and the yellow

-10dB display illuminate with increasing signal level (see Figure 10 on next page).

When the ampliﬁer is turned off, muting should be virtually instantaneous, with

all red LEDs illuminated until the power supply discharges.

Table 3. LED Display Operation

Operation

Figure 13. Gain

Control Lockout

Installation