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| 0 dB/-15 dB Switch | Use this switch to set the optimal input level. Typically, you’ll want to use the -15 dB setting with instruments that include high-output pickups or active electronics, or if you frequently see the Peak LED [13] light up. | |
| Input | Connect a passive or active instrument to this 1/4" jack. | |
| Super Grit Technology (SGT) Section | Adds classic Ampeg overdrive. | |
| On/Off: | Enables or disables the SGT circuit. The SGT circuit may also be toggled on and off using an optional footswitch connected to the Switch jack on the rear panel. (Note that connecting a footswitch disables the front panel switch.) |
| SVT/B15: | This switch toggles between two “flavors” of overdrive, based on the character of either the SVT or Portaflex B15 tube amplifiers. |
| Grit/Level: | This dual-concentric knob adjusts the amount of grit (the inner control) and the overall output level of the circuit (the outer control). |
| Power/Mute Indicator | This LED bar lights up blue when the amplifier is powered on and red when the Mute switch [14] is engaged. | |
| Gain | Adjusts the signal level driving the preamplifier. | |
| Bass | Provides up to 13dB of boost or -21dB of cut at 40Hz (flat at center position) | |
| Mid/Freq | This dual-concentric knob selects the midrange frequency to be boosted (the outer control), and the amount of boost or cut up to 16dB (the inner control). | |
| Treble | Provides up to 12dB of boost or -16dB of cut at 4kHz (flat at center position) | |
| Volume | Adjusts the overall output level of the Speaker, Phones, and Preamp outputs. | |
| Ultra Lo | This 3-way switch selects a -20dB cut at 40Hz (left) or a 2dB boost at 40Hz combined with a -10dB cut at 500Hz (right). The center position bypasses the Ultra Lo circuit. | |
| Ultra Hi | This 2-way switch engages a 9dB boost at 8kHz. | |
| Peak | This LED lights when your input signal is too high. | |
| Mute | Engaging this switch mutes the Speaker outputs, the FX Loop Send, the DI output, and Preamp output. The Aux In signal at the Phones output is not muted. Mute may also be toggled on and off using an optional footswitch connected to the Switch jack on the rear panel. The Power/Mute Indicator LED [5] illuminates red when Mute is engaged. | |
| Power | Toggles the amplifier’s power on (I) and off (O). | |
| AC In | The included IEC power cable is connected here. | |
| Speaker Out | The Neutrik speakON combo jack accepts either speakON or 1/4" TS speaker cables. | |
| Phones | Connect headphones to this 1/4" TRS stereo output to monitor a mix of the signals coming from the Aux In and the front panel 1/4" Input. | |
| Aux In | Connect the audio output from any line-level source (an MP3 player, a CD player, etc.) to this 1/8" TRS stereo input to play along with your favorite audio when listening through headphones. | |
| FX Loop | The 1/4" unbalanced FX Loop Send and Return jacks operate at line level. | |
| Send: | This output is affected by all controls except the Volume control. |
| Return: | This input may also be used to connect an outboard device directly to the power amp independently of the FX Loop. |
| Mix: | Adjusts the blend of direct (Dry) and effected (Wet) signals. The fully clockwise position is equivalent to a serial effects loop. |
| DI Bal. Out | This balanced XLR output may be used to route line-level audio to the input of an external mixer or recorder, or to an external power amplifier or powered loudspeaker. It is not affected by the Volume control. | |
| Pre/Post: | When set to Pre the DI signal bypasses the -15dB input pad, Compressor, tone controls, SGT circuit, and FX Loop. When set to Post it includes them. |
| -20dB: | Reduces the DI output level by 20dB. |
| Lift/Gnd: | Engages the ground lift to help eliminate hum if necessary. |
| Switch (TRS) | Connect a 1/4" TRS dual footswitch to remotely toggle the SGT circuit (tip) and Mute (ring) on and off. Connecting a TS single footswitch will toggle the SGT circuit on and off. | |