KHE Master-FX-Loop Switching
This guide explains how to use the KHE FX-Loop Switching function. Most modern guitar amps have an FX Loop with Send and Return jacks, allowing to insert effects pedals after the preamp/distortion circuit.
The KHE’s FX-Loop Switching enables to use a single pedal board in the fx-loop of all connected amps: The effect pedals and each amp’s fx-loop send/return jack are connected to the KHE. This enables the KHE to automatically switch the effect pedals to the activated amp fx-loop. It is a serial mono fx-loop and works with all types of effects: Delay, Reverb, Chorus, Noise Gates, EQ, Pedal Switching Systems and Multi-Effects, even in 4-Cable-Method. The output volume knob of effects units can also be used as a single master volume control for the entire rig. Pedals like Overdrives or Boosts are connected as usual in front of the KHE.
The KHE FX-Loop can be true-bypassed. The on/off state of the loop is saved for each amp individually and gets activated (or deactivated) automatically when switching amps. It can also be remotely controlled via MIDI.
The fx-loop switching feature is build-in with the ACS 4x4FX, or it can be added to the ACS 8x4 or ASX 8 with the AFX 8 FX-Loop Switcher.
The ACS 4x4FX with the built-In FX-Loop Switching
Wiring & Setup
Setup Tip: Before connecting the pedalboard, make sure the ACS and all amps and cabs work correctly. It’s crucial to be methodical during the setup. Start with the most basic KHE setup possible (amps+cabs, no pedalboard, fx-loop or attenuator) and add things step by step.
Amp FX-Loop
Each amp must be connected with its the fx-loop send/return to the related KHE fx-loop. Make sure to use the same channel as for the amp input and output (AMP 1 = FX-Loop 1).
Connect the Amp FX-Loop Send jack to the KHE FX-Loop Send (top jack).
Connect the Amp FX-Loop Return jack to the KHE FX-Loop Return (bottom jack).
Effects & Pedals
The effects, such as Delay, Chorus, Noise Gate, Multi-FX and such are all connected to the KHE Master-FX-Loop:
Connect the Pedal Input of the pedalboard to the KHE FX-Input (top jack).
Connect the Pedal Output of the pedalboard to the KHE FX-Output (bottom jack).
The stompboxes like Overdrives, Boosts and such are connected in front of the KHE and the amps as usual:
Connect the Guitar to the Input of the pedal or board.
Connect the Output of the pedal or board to the KHE Guitar Input (front or back).
Notes:
Use shielded 1/4” TS instrument cables for all connections. Do not use cables with right angle plugs. Learn more: ACS Cable Guide
Set all amp fx-loops to serial or 100% wet and make sure to active the fx-loop on the amp.
The KHE Master-FX-Loop is a serial mono fx-loop. Stereo effects can only be used in mono with one output connected.
The KHE can not add a post-amp fx-loop to an amp without a real fx-loop. The amps must have a real fx-loop to use this feature. See more on that later in this guide.
Wiring Diagram: ACS 8x4 + AFX
With the KHE AFX 8 FX-Loop Switcher, the wiring is identical to the ACS 4x4FX. The AFX must be paired with the amp switcher. Learn more here: AFX 8 Setup and Pairing Procedure
Master-FX-Loop Operation
Control
To activate the fx-loop, press the small FX button on the ACS 4x4FX or AFX8 front panel. The FX light indicates the fx-loop status: Red (On) = Loop active, Dark (Off) = Loop bypassed. The fx-loop can be true-bypassed for each amp individually.
Bypass Memory
The bypass state of the fx-loop can be set for each amp individually. When switching amps, the KHE remembers which amps had the loop turned on and activates (or deactivates) it automatically.
MIDI Control
The master-fx-loop can be turned on or off by MIDI. With CC commands, send CC#127 Value 127. With PC commands, the on/off state is saved for each preset individually. Learn more: KHE MIDI Guide
Things To Know
Pedal Board 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 or have grouped outputs. Otherwise a ground loop may happen (hum & squealing noise). Also experiment with the Ground Lift switches and check which setting gives the best results. See the section below for troubleshooting tips.
How it works
Inside the KHE, a relay switching matrix connects the effect pedals to the fx-loop send/return jack of the activated amp. When switching amps, the KHE will automatically connect the activated amp’s fx-loop to the master-fx-loop pedals and bypass the other amps.
Amps without an FX-Loop
Most modern amps have an fx-loop. But some (vintage) amps don’t. The KHE cannot add or create a post-amp fx-loop for an amp without an fx-loop. Only amps with a real fx-loop can take full advantage of this feature.
Alternatively, is is possible to route the input section for these amps differently, so the fx-loop is active in front of the amp, rather than in the post-amp fx-loop. Learn more: ACS Front-FX-Loop. Alternatively, consider using a power attenuator with a built-in fx-loop, such as the Fryette Power Station or Boss Waza TAE.
Amps with built-in Reverb or Effects
Some amps have built-in effect, such as a spring reverb or multi-fx processor. When using such amps with the KHE, special attention is necessary. When using high fx-settings, such as loud and long delay repeats or reverb, deactivate the effect first (or let it ring out) before switching amps on the KHE, especially at high volumes. This prevents the load resistors inside the KHE from overheating due to the ongoing effect signal. It using moderate effect settings or low volumes, this precaution may be unnecessary. No special attention is needed with effect pedals used with the KHE Master-FX-Loop, you can switch while you play.
Individual Amp Pedals
Do not connect pedals directly in front of an amp. The Amp Input must be directly connected to the KHE Amp Input jack. Also, don’t connect pedals directly to an fx-loop of an amp. The FX-Loop must be directly connected the the KHE FX-Loop Switching section. The reason for this is that the 9V pedal power for these individual amp pedals can easily create a dangerous (hidden) ground loop with the activated amp if not isolated 100% which could damage the switcher. Do not daisy-chain the power of such pedals from a single power supply. If you really want to use such a setup, use batteries for these pedals, or a individual power supply for each amp. Be very careful, this type of setup is not recommended for safety reasons.
Advanced Setups
How to use Multi-FX and Modelers in 4-CM
Master FX-Return (Power Amp In)
The KHE FX-Output jack can also serve as a global Power Amp Input. Connect the output of a preamp to the KHE FX-Output jack. The input of the preamp is directly connected to the guitar, the KHE can not switch the input automatically. Do not connect an input source directly to an amp fx-return. The amp fx-returns must be directly connected to the KHE jacks. Otherwise it would disrupt the KHE’s input muting system which is not safe to use.
Noise Gates in the FX-Loop
When using a noise gate with key input, you may have to use a quality signal splitter with transformer isolation for the key input source. Keep the grounds of each section isolated all the time. Otherwise a ground loop may happen (hum & squealing noise).
KHE Switcher Models & Linking
The ACS 4x4FX has the fx-loop switching function built-in. For the ACS 8x4 or the ASX 8, it can be added with the AFX 8 FX-Loop Switcher. The small ACS 4x2 does not have the fx-loop switching feature. The Master-FX-Loop section of the KHE can also be linked, to expand the total switching channel of the system. Lean more: KHE Linking Guide and KHE FX-Loop Switching Linking (coming soon).
FAQ
Can I use Multi-FX, Noise Gates or Modelers in 4-CM?
Yes, totally possible. See some examples above.
Can I connect the pedals to the white S-Line send/return jacks instead of the fx-loop?
No, the S-Line jacks have speaker level and would destroy any pedal immediately.
Can I use amps that have no fx-loop?
Only limited. The KHE cannot add or create a post-amp fx-loop for an amp without an fx-loop. Only amps with a real fx-loop can take full advantage of this feature. Alternatively, is is possible to route the input section for these amps differently, so the fx-loop is active in front of the amp, rather than in the post-amp fx-loop. Learn more: Amps with no FX-Loop
Can I use the pedals in Stereo?
No. The KHE has a mono serial fx-loop and can not be used in stereo. If a stereo pedal is used, only connect one output to the KHE, to use it as a mono effect.
Can I connect a pedal switching system to the Master-FX-Loop?
Yes, totally possible.
Can I use the KHE fx-loops 1-4 to switch pedals in and out, like a pedal bypass switcher?
No, the KHE fx-loop section is not a pedal bypass switcher. It is designed to switch the amp fx-loops to the master-fx-loop and follows the activated amp.
Can I use an amp’s built-in spring reverb with the other amps?
No, not possible.
Troubleshooting
No sound at all / FX-Loop isn’t working correctly
Double check wiring, make sure to not mix-up the sends, returns, inputs and outputs.
Make sure the KHE master-fx-loop is activated.
Make sure the amp fx-loop is activated.
Make sure the pedals are turned on.
Make sure cables are fully inserted and functional.
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.
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.
Check for ground loops and experiment with the ground lift switches (line out, XLR, USB).
If using an attenuator, make sure the KHE Attenuator Loop is activated.
If using a load box or attenuator, check if the noise is caused by magnetic interference with the device. If the noise reduces when you move away with the guitar or if you turn down the guitar volume, try physically separating them and avoid standing too close to the device with your guitar.
Downsize system to only amps+cabs with no attenuator or pedals and rebuild the setup step-by-step.
Distorted Delay Trails 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.
Learn more: ACS Troubleshooting Guide
Return Home: KHE ACS Help Center
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