Troubleshooting Guide

This guide helps you troubleshoot your amp switcher rig if things are not working correctly. It also provides valuable insights for first-time users, helping them learn about the most common mistakes. To avoid the most common problems, read and study the following guides: ACS Safety Information and ACS Basic Setup Guide and ACS Cable Guide.

Table of Content:

  • Most Common Problems

  • ACS LED States

  • No Sound or Weak Sound

  • Squealing or Feedback (high-pitched noise)

  • Ground Loops - Hum, Buzzing & Squealing

  • Attenuator Troubleshooting

  • FX-Loop Troubleshooting

  • MIDI Troubleshooting

  • Linked Switchers Troubleshooting

  • KHE Customer Spport

Most Common Problems

Amplifier Does Not Switch On (3x blink)

The KHE will not enable an amp if no cabinet output is activated (safety reasons). The amp light will blink 3 times to show the error. Activate a speaker cab or load box on the KHE first, by pressing the CAB switch so the light is bright. Then press the AMP switch.

Cabinet Output does not Switch On (3x blink)

A cabinet output can only be activated if a cabinet is connected. The KHE monitors the red CAB jacks and enables the activation of a cabinet output only if a load is detected. The KHE cabinet lights have three states: dark (no cab connected), dimmed (cab present), bright (cab activated). Connect a load to the red CAB jack and press the corresponding CAB switch so the light is bright. If a cab or load is not detected by the ACS, check the cables and the jacks on the cab (use Craig DeoxIt to clean the contacts).

Attenuator not working

Make sure the attenuator loop is activated in the KHE System Menu. See more help below.

ACS LED States

 
 

AMP Lights State:

  • Off: Amp deactivated

  • Red On: Amp activated

  • Red Blinking 3x: Error - No Cabinet activated (activate cab before amp)

  • Red Blinking continuously with loud acoustic piezo buzzer: Resistor Overload

  • ASX blinking Amp Lights: No load connected. Connect load to enable operation.

CAB Lights State:

  • Off: Cab deactivated & not connected

  • Red Dimmed: Cab connected but deactivated

  • Red On: Cab activated

  • Red Blinking Cab 1-4 on Power-Up: Attenuator Insert Loop is activated but no attenuator was detected by the KHE.

  • CSX blinking Cab Lights: No load connected. Connect load to enable operation.

CTRL Light State:

  • Red On: Normal operation mode with a single switcher

  • Green On: Normal operation mode with linked switchers

  • Red Blinking Slow: System Menu

  • Red Blinking Fast: MIDI PC Preset changed

  • Green/Red Blinking: Error - Network CTRL Setup

  • Orange Blinking: Error - DC Input Voltage out of range. Make sure to use the KHE Power Adapter.

All Cab Lights Blinking - Attenuator Startup Check (Flashing Cab Lights)

When the KHE Attenuator Loop is activated, the KHE checks during power-up if an attenuator is connected. If not connected or in bypass, the KHE will not activate the Attenuator Loop for safety reasons. If no attenuator is detected, the KHE cabinet lights will start blinking to show the missing attenuator load (for ACS with serial nr. B6-x starting Feb’24). While the lights are blinking, you can either a) connect the attenuator to allow the KHE to detect it and activate the loop or b) clear the error by pressing any switch (the Attenuator Loop setting will be deactivated, and the loop will not be activated).

New: Piezo Buzzer for Safety Warnings

With the newest generation of KHE ACS switchers (Serial B6-x, starting Feb’24), the internal load resistors are now continuously monitored to sense overloading, which can occur due to incorrect use, cable defects, or amp malfunctions. In case of an overload, the KHE will enter an error state, accompanied by a loud acoustic buzzer as a warning signal. The corresponding amp light on the KHE will start blinking, indicating which amp has an issue. Immediately power off ALL amps, meticulously check the wiring and cables, and ensure correct usage of the KHE. Once the amp or wiring issue is resolved, clear the error by pressing any amp or cab switch.

No Sound or Weak Sound

  • Make sure an amp and cab is activated on the KHE. Both lights must be bright red on.

  • Double-check the wiring for each amp and cab.

  • Do not mix-up channels on the KHE. Make sure to use the correct jacks on the KHE.

  • Make sure the cable plugs are fully inserted into the jacks. Check the amp and the KHE.

  • Rotate and re-insert the plugs a few times to improve dirty jack contacts. Use contact spray such as Caig DeoxIt to clean the contacts (no WD40!).

  • Make sure the cables are fully working and functional. Bad cables or solder-less patch cables on your pedal board can cause all kinds of problems.

  • Try using the KHE front Guitar Input instead of the rear input.

  • If using pedals in front of the KHE, remove it for the moment and connect the guitar straight to the KHE guitar Input to see if it helps.

  • If using the KHE fx-loop, bypass the loop by pressing the FX button to see if the problem is caused by the effect pedals. See more tips later in this guide.

  • On some amps, unused fx-loop send/return jacks can cause problems over time (contact corrosion). Try shorting the amp’s fx-loop send and return jack by a short instrument patch cable to see if it helps.

  • If using an attenuator, make sure the KHE Attenuator Loop is activated in the System Menu. The attenuator won’t work correctly if not activated. See more tips later in this guide.

  • Make sure the amps are turned on and out of standby. Check the amp’s volume settings and fx-loop switch.

High-Pitched Squealing or Feedback

  • Is the wiring correct? Wrong connections or routing can cause feedback, oscillation and squealing. Check the wiring and everything above in detail.

  • Do you use an Attenuator? If yes, do you have the KHE Attenuator Loop activated in the System Menu? Make sure the Attenuator Loop is activated.

  • Do you stand too close to an Attenuator or Load Box? If you encounter high-pitched feedback noise, it may be due to proximity to an attenuator or load box with the guitar pickups (magnetic interference). Move around with the guitar, creating some distance, and observe if the noise changes. If the noise remains constant, it is caused by another factor.

If this doesn’t solve the issue, there’s maybe a ground loop or grounding problem somewhere in the rig. Usually ground loops create a low frequency humming noise, but sometimes they also can cause a high-pitched squealing noise. See the next section for more information.

Ground Loop - Hum, Buzzing & Squealing

Cables & Wiring

  • Don’t use cables with right-angle plugs on the back of the ACS. If the metal housings touch each other, it can disrupt the KHE’s ground isolation and cause a ground loop. Isolate the plugs with tape if needed.

  • Make sure the metal cable housings don’t touch each other. Sometimes XXL plugs or right-angle plugs may touch each other, causing a ground loop. Isolate the plugs with tape if needed.

  • Make sure all cables are in good condition. Faulty or old cables are often the cause of issues.

  • Verify that the wiring is correct.

AC Power

  • Make sure to use the KHE DC Power Adapter. Use the provided AC Mains cable with a 3-pin connector (PE / Earth).

  • Make sure all amps have a secure Earth / PE connection with a 3-pin mains connector. Avoid using amps with 2-Pin plugs or those lacking an earth connection. Do not modify or remove the earth connection. Do not alter the grounding of the power strip. Avoid using ground lift adapters or cables. All amps MUST have a stable earth ground connection.

  • It is recommended to power all amps and switchers from the same outlet. For optimal grounding, connect all amps and switchers to the same power source or outlet when possible. If multiple outlets are used, it may cause noise or hum, depending on factors such as house electric wiring. Ensure the appropriate power rating and reserve are utilized.

External Connections

  • Do you use the KHE Tuner Output? If yes, unplug the cable from the KHE Tuner Output temporarily and check if it reduces the noise. Some tuners may introduce extra noise or create a ground loop with certain amps. In some cases, using a passive transformer box to isolate the tuner may be necessary. Try experimenting with the tuner's power supply, opting for a linear one instead of SMPS. Hold off on reconnecting the tuner for now; save it for the final step.

  • Do you use a Reamping Box? If so, disconnect it temporarily and use a real guitar for the initial setup. Experiment with the Ground Lift switch of the reamping box. Make sure to use a reamping box with transformer signal isolation.

  • Do you use a Line Out or XLR Output? Some load boxes, attenuators, or multi-fx units have line outputs, which can lead to ground loops. Temporarily disconnect the cable and check if it improves the situation. If the output has a ground lift switch, experiment with its setting. In some situations, using an isolation box with a transformer may be necessary.

  • Do you use a USB connection? Some load boxes, attenuators, or multi-fx units come with a USB port, which may result in a ground loop or unusual digital noise. Disconnect the USB cable temporarily and check if it resolves the issue. In certain cases, you may need a USB Ground Isolator for a solution.

Pedalboard & Pedal Power

  • Do you use a Pedalboard? Sometimes using a pedal board can cause noise and hum (bad cables or contacts). Temporarily disconnect all pedals and connect the guitar directly to the KHE Guitar Input to troubleshoot the source of the problem.

  • Do you use Pre- and Post-FX? Sometimes a ground loop can happen between the pre and post pedal section, caused by the 9V pedal power. Use isolated DC power for each pedal section. Do not use daisy-chain adapter cables between the pre- and post section. Keep the grounds of each section isolated all the time. If using a single PSU with multiple DC outputs, make sure the outputs are 100% isolated. Use high-quality power supplies only (linear preferred). Many cheap PSUs are not isolated or have grouped outputs.

  • Do you use a Noise Gate, perhaps in 4-CM? Some noise gates can induce a ground loop if not used correctly. Temporarily disconnect the gate and check if the issue improves. When using a noise gate with a key input, like the Fortin Zuul, it's recommended to use a signal splitter with transformer isolation for the key input signal. Use a separate isolated 9V power output for the gate. Make the grounds of each section are consistently isolated to prevent potential ground loops resulting in hum and squealing noise. If the gate has a ground lift switch, experiment with the switch setting.

  • Do you use a Multi-FX, perhaps in 4-CM? Sometimes ground loops can occur with such devices. Remove the Multi-FX temporarily and check if the noise improves. Experiment with ground lift switches, or consider using an isolation box with a transformer at one of the outputs if necessary.

 
 

  • Do you use other Signal Switchers or Routers? If you have a complex routing system with other switchers or A/B boxes, they might introduce ground loops. Keep the cables short and be mindful of the signal isolation, signal routing and the 9V pedal power routing to avoid interference.

  • Do you use any other Special Devices or Setups? If you use any unique devices, setup types, or connections, they may contribute to the noise. Strategically downsize the system to isolate the problem.

Placement

  • Typically, the position of the KHE in the amp rack is not critical. It can be placed directly on top or below an amp. Ensure not to cover the sides of the KHE (vent holes) and maintain proper airflow. It is not necessary to have an empty rack space between the units.

  • When using load boxes and attenuators, refrain from placing them too close to the guitar. If positioned too closely, the magnetic field of the load box can interfere with the guitar pickup, resulting in squealing noise and hum.

Attenuator Troubleshooting

Attenuator not working correctly / No sound

  • Check if the Attenuator Loop is activated in the KHE System Menu. Maybe it got deactivated because it not connected during power-up (safety feature)? See the KHE Attenuator Loop Guide to learn more.

  • Make sure an amp + cab is activated on the KHE.

  • Make sure the attenuator input and output is not mixed up.

  • Make sure cables are fully inserted & functional.

  • Make sure the devices are being operated correctly.

  • Downsize system to only amps+cabs with no attenuator or pedals and strategically rebuild the setup.

Hum or High-Pitched Squealing Noise

  • Is the KHE Attenuator Loop activated? Double-check everything above.

  • Dynamic Noise: Does the noise change your position in the room? Does it get worse if you move closer to the attenuator or load box? If the noise disappears when turning the guitar volume down, then the noise is most-likely caused by magnetic interference with the (reactive) load device and the guitar pickups. You are standing too close to the device. Move your guitar around to learn how it reacts. Try moving the attenuator or load box a little further away or lower gain and volume as a last resort.

  • Static Noise: If the noise is still present, even with the guitar volume turned all the way down and not changing with your position in the room, the noise is most-likely caused by a ground loop somewhere. First, check the fx-loop and the pedals. Make sure to use isolated 9V power for the fx-loop to avoid ground loop. Don’t use daisy-chain power adapter cables. Temporary remove the pedals to isolate the problem. If using a noise gate with key input such as the Fortin Zuul, use a splitter with transformer isolation for the key input to avoid ground loop. Keep the pre- and post pedal section ground isolated all the time. Experiment with the Ground Lift Switch settings.

Attenuator Bypass not working

Did you try to bypass the attenuator by deactivating the KHE Attenuator Loop, and have the attenuator still connected to the KHE S-Line jacks? This ain’t gonna work. The KHE can not bypass the attenuator. It must be disconnected and the attenuator loop must be deactivated. Make sure to read the KHE Attenuator Guide.

Sound or noise coming from inside amp/attenuator/load box

  • Sound of broken speaker inside the amp: When an amp or load box is pushed hard, it can cause weird noise and sound which kinda sounds like a small broken speaker, coming from inside of the amp or transformers. Fear not! This is normal. The vibrations from the transformer laminations and inductors can create strange distorted sounds, but there's nothing to worry about.

  • High-pitched squeal coming from inside the amp: Immediately power everything off (PS, KHE, Amps) and verify the correct wiring of the amp. Make sure the cables are fully inserted and in good working shape.

FX-Loop Troubleshooting

No FX Sound (bypass ok)

  • Make sure the KHE master-fx-loop is activated. Press the small FX button so the FX light turn on.

  • Make sure the amp fx-loop is activated.

  • Make sure the pedals are turned on.

  • Make sure cables are fully inserted and functional.

  • Check the FX Send and Return wiring. Maybe the jacks are mixed up.

  • Check the FX Input and Output wiring. Maybe the jacks are mixed up.

No Sound At All

  • Bypass the KHE master-fx-loop by pressing the small FX button. If this works, there is a connection problem with the effect pedals.

  • Make sure to not mix-up the fx input and output.

  • Make sure to not mix-up the amp fx-loop send and returns.

  • Downsize system to only amps+cabs with no attenuator or pedals and rebuild the setup step-by-step.

Hum Noise or high-pitched Squealing Noise

  • Check everything above. Check the cables and wiring.

  • Remove the cables at the KHE FX Input and Output, and set the KHE fx-loop to bypass. Is the noise gone? This indicated a ground loop or other problem with the effect pedals.

  • Check for ground loops and experiment with the ground lift switches (line out, XLR, USB).

  • Some advanced setups, such as a setup with a multi-fx in 4-cm or noise gates in 4-cm, may require a ground isolation box at some outputs.

  • Make sure to use quality isolated 9V pedal power for the pre- and post-pedal section. Do not use daisy-chain adapter cables to share the power between the pre- and post section.

  • Downsize system to only amps+cabs with no attenuator or pedals and rebuild the setup step-by-step.

Distorted Delay Trails or Noise when switching Amps

When using Delay or Reverb effects, it’s recommended to have a similar fx-send level on all amps. If the delay is active and the fx-send level change is too high, it can cause unpleasant noises during the switching: Large delay signals from the previous amp may overpower the fx return stage of the new amp if not set to the same sensitivity. Aim to set all amps to the same signal level at the fx-send jack, by adjusting channel volume, master volume, and fx-send level for each amp (it’s a bit trial and error). Set all amp fx-loop to serial or 100% wet.

Treble- or Signal Loss with some Amps

Some amps have a bad fx-loop design with high output impedance. This can cause a slight treble roll-off or signal loss when the fx-loop is activated, depending on the total fx-loop cable length. The KHE can not compensate for this bad amp design. Place these amps close to the KHE and use the shortest possible cables.

AFX 8 Troubleshooting

  • Make sure to pair the AFX with the amp switcher. Learn more: AFX 8 Linking & Pairing Procedure

  • Make sure to activate the AFX fx-loop. This is sometimes missed because of the dimmed red light. Press the FX/CTRL button to activate the fx-loop, so the light is bright red.

  • If the AFX isn’t responding to MIDI CC commands, try connecting the MIDI controller directly to the AFX MIDI Input. Make sure the midi channel number in the controller matches the AFX channel number.

MIDI Troubleshooting

The KHE does not respond or react to the MIDI commands at all.

  • Verify MIDI Input: Ensure the KHE MIDI IN jack is used. Don’t use the CTRL IN or CTRL OUT jack.

  • Verify MIDI Output: Ensure to use the MIDI OUT port on the controller.

  • Check MIDI Channel Settings: Confirm the KHE and the controller are set to the same MIDI channel.

  • Power-On Sequence: Try to turn-on the KHE last, after the controller or other MIDI devices.

  • Test a Different MIDI Cable: Sometimes even new MIDI cables can cause troubles (they are usually cheap).

  • Simplify the Setup: If daisy-chained, reduce the MIDI rig to only include the KHE and the controller for the initial setup.

The KHE doesn’t respond with daisy-chained MIDI devices.

Some MIDI devices have a combined MIDI OUT/THRU port, typically set to OUT by default. This may prevents the device from passing through incoming data. Try setting it to THRU. Refer to the controller's user manual for additional information.

The KHE doesn’t work right with CC commands.

Check the programmed CC parameters in the controller (amp/cab number + 127). If on/off parameters are available, set both to 127. Ensure it is set to Toggle Mode. Confirm that your controller supports Toggle Mode or repeated sending of commands

My MIDI Controller cannot send CC#126 or CC#127.

Some MIDI controllers have an limited and incomplete CC data range (120 instead of 127). Refer to the controller user manual for information on the data range. A workaround is to use a 'MIDI event processor' in front of the KHE to modify the data. For instance, remap incoming CC#120 to CC#127. See Little Helpers (coming soon)

I added a new KHE switcher to my old ones, and now if I am loading MIDI PC presets, the KHE reboots.

This can be caused by a preset data collision (safety precaution to avoid loading any invalid combination. Execute a System Reset with all KHE switchers and start with a clean setup again.

Learn more: KHE MIDI Guide

Linked KHE Switchers Troubleshooting

coming soon

KHE Customer Support

If you can’t get things to work, worry not, we are here to help! Send us a message and describe your problem. Let us know all involved gear (amps, cabs, effects, attenuators, load boxes and such) and how you use it. Make sure to include all relevant details. Sometimes it’s helpful to send a short video recording of the issue to diagnose the problem.

Return Home: KHE ACS Help Center