ACS Safety Information
Initial Setup
Follow the Basic Setup Guide for the initial setup and read the safety information here. Learn about the ACS Amp and Load Types & Compatibility and check the ACS Cable Guide. Study all documentation in detail to avoid wrong use or wiring errors, which may damage the gear. Be methodical during the setup and troubleshooting. Slow is smooth and smooth is fast. Better be safe than sorry.
In case things are not working right, check the ACS Troubleshooting Guide. If you need support, contact us, we’re always happy to help.
ACS Switch Operation & Safety Logic
On the ACS, an amp can only be activated if a speaker output is activated, to prevent a no-load scenario for the amps. Speaker cabs can only be activated if a load is connected, to prevent switching amps to unused cab outputs (KHE “Load Sensing” technology). Only one amp can be active at time. Switch from one amp or cab to the next by the push of a switch. No need to stop playing or to deactivate the other amp first. The KHE takes care of the right switching order and keeps everything safe.
Amp Wiring & Cabling Rules
Always connect the amp head with both its Guitar Input and Speaker Output to the ACS. Connecting both the amp inputs and speaker outputs is crucial for a safe operation. Except for Combo Amplifiers, those can be used with their internal speakers instead.
Do not connect the guitar directly to an amp guitar input. Doing so would disrupt the KHE input muting and cause a safety critical situation. Always connect the guitar (or pedal board) to the KHE guitar input, and connect the amp input to the black KHE amp input jack.
Do not change the cabling while the amps are powered on. Always deactivate the amp on the KHE and turn off the AC power of the amps and attenuator when changing any cables or connections. Never unplug the amps guitar input or speaker output cable while powered on.
Do not mix-up any cables or connections. Incorrect wiring may damage the equipment. Double- and triple-check every single connection. Use labels or color coding for the cable pairs for easy identification. Learn more: ACS Cable Guide
Do not power on the amps while the KHE is powered off. Always power-on the KHE first.
All impedance questions are answered here: KHE Impedance Guide
The KHE is not a Load Box!
The internal load resistors designed to protect & load the amplifiers with its input muted, so all amps are in safe idle state when deactivated. However, the resistors are NOT designed to be a full power load replacement like a reactive load box for silent recording or similar. To use an amp, at least one speaker cabinet or load box must be used. Never try to use the KHE itself as a load box (yes, people did it).
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.
Do not use malfunctioning Amps with the KHE!
If an amplifier has an issue such as hum or squealing noise that cannot be resolved immediately, do not use it with the KHE. Turn off the AC power of the amp and inspect the wiring and cables. Make sure the amp is in good working condition (tubes, fx-loop jacks, input output jacks and such). Connecting a malfunctioning amp to the KHE may result in damage to the device. Refer to the Troubleshooting Guide for more help.
Never remove or modify the Earth Ground PE of an amp, cable or other gear!
Always use 3-pin AC mains connectors with a solid earth connection for all amps, gear and KHE switchers. Do not use any ground lift adapters or cables on the AC input side. In case of hum problems, do not mess with the earthing of a device as it is safety critical. In case of ground loops or hum, check the KHE Troubleshooting Guide. Do not use any signal isolation boxes between the ACS and the amp. Doing so can disrupt the KHE’s input muting circuit and cause a safety critical situation. Contact us if you need assistance.
Activate the Attenuator Insert Loop!
If using an attenuator at the KHE’s white S-Line Send & Return jack, activate the Attenuator Loop in the System Menu. If not activated, the attenuator won’t work correctly. The KHE can not bypass the attenuator. Learn more: ACS Attenuator Loop Guide
Do not connect pedals to the Attenuator Loop!
The ACS Attenuator Insert Loop (white S-Line Send and Return jacks) is designed for power attenuators with speaker level. It can not be used as an fx-loop for normal guitar pedals or such. Doing so would destroy the pedals immediately (yes, people did it).
Do not exceed 150W RMS of output power.
The KHE ACS is designed to switch a maximum of 150W RMS. Pay attention to the maximum power rating of your attenuators, load boxes and speaker cabs. Learn more: Maximum Amp Power Rating
Do not leave the Rig unattended!
If you leave the room for more than 5 minutes, set all amps to standby or power them off for safety reasons.
No Stereo Use with a single KHE Switcher!
The KHE is a mono amp cab switcher - Only one amp can be activated and played at the time. It is not possible to activate two or more amps simultaneously and play them in stereo. There are no workarounds or setup tricks to make this possible. Do not try to outsmart a single KHE’s routing to use it in stereo - it doesn’t end well (warranty void). More information about stereo gear and what’s possible with it: ACS Stereo Setups
Use quality Cables and Connectors.
Don’t use bad cables, or old cables with weak and worn-out connectors. Do not use cables with right angle plugs on the back of the KHE. The metal housings can touch each other, causing a ground-loop (hum&noise) which can be safety critical. Same for XXL connectors: The KHE jack spacing is 18.5mm. Make sure the housings aren’t touching as it would disrupt the ground isolation. Wrap the housings with isolation tape to be safe. Learn more: ACS Cable Guide
No pedals on individual amps or fx-loops!
Do not connect any pedals directly to an amp input or it’s fx-loop. Doing so would disrupt the KHE’s input muting circuit and the 9V power routing could cause a critical hidden ground loop which could damage the equipment. Always connect the pedals in front of the ACS, or in the master-fx-loop (ACS 4x4FX or ACS 8x4/ASX + AFX). If you really want to do it, make sure to use an individual power supply for each amp and make sure it is 100% isolated from the other devices. Using batteries would be recommended. Use it at your own risk.
Do not connect an input to an single amp fx-return!
Doing so would disrupt the KHE input muting circuit and cause a safety critical situation when the amp is deactivated. If you want to use the fx-return as a power amp input for a preamp or such, use the ACS4x4FX or AFX and connect it to the master fx-return, so all amps are safe. Learn more: Using the FX-Return as a Power Amp (coming soon)
The KHE CTRL Jacks are not MIDI!
Do not connect any MIDI gear to the CTRL jacks. The CTRL input and output are used to link KHE switchers and uses it’s own communication protocol (CAN Bus).
Sound from Inside the Amp
When an amp is played loud with a load box (silent recording), sometimes sound can be heard from the vibrating amp- and load box transformers. This type of noise is normal. However, if you ever notice any noise from a deactivated amplifier on the ACS, such das a high-pitched squeal from the inside of the amp, immediately power-off the amp and check for tube failures, bad cables or wrong connections and other amp malfunctions. Resolve the issue with the amp before using it with the KHE again.
Verify the compatibility of your gear!
Study all the product manuals of your gear and verify it can be used together. For example, some attenuators or load boxes do not work with solid-state amps. Make sure to use all the gear in the right way. See some specific help guides for the post popular gear here: KHE Gear Examples (coming soon) . If you are unsure, send us as message, we’re always happy to help!
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