Tips for using amplifier cabinet switchers

The devices for switching between a couple of amplifiers and cabinets have become increasingly popular recently. They are very useful for a quick A/B comparison or playing in studios. Also, if you have several amplifiers, rewiring the cables takes some time and comparing them by routing the cables is almost impossible because it takes time. Many musicians with more than one amplifier prefer to build a complete routing system for their entire rig at home or on stage. Based on my experience and speaking with many musicians through the years, I decided to summarize some of the most common issues. These tips will be helpful to you if you have an amplifier cabinet switcher. They are universally applicable to all brands.


Ground loops issues:
Usually, the devices that are used to switch between two or more amplifiers are based on relays. Most of them isolate the sensitive input ground among the amplifiers in order to prevent hum, keeping the speaker output ground common. Based on my experience, some of those devices still have ground loop hum, and also those switching systems are not suitable for bridged mono amplifiers where the “ground” and signal wires are live. The N-audio amplifier switching systems, completely isolate the inputs and the outputs of all amplifiers. This is the correct method for the best performance!
It looks perfect, but in reality, you can see some of the problems even here. The devices on the market that switch between amplifiers and cabinets have a lot of 1/4” sockets on the back placed close to each other. If you use right-angled jacks, they could touch one other, connecting different grounds together. This will create ground loops, adding hum or high frequency noise. So, my advice to you is to use only straight guitar jacks that are not touching one other! Also, grounding the output of bridged mono amplifiers can destroy them! Bridged mono amplifiers that I know of are some Kemper amplifiers, Orange Micro terror series amplifiers, and most of the modern Class D amplifiers based on off-the-shelf amplifier modules.



The mains power source:
I highly recommend using one source for powering the whole rig. Use one power strip for your rig. Avoid powering air conditioners, motors, heaters, etc. from the same power strip!

Using the right cables:
There are two types of cables for wiring the the whole setup. One that goes to the input of the amplifier where usually you plug the guitar, and one from the output of the amplifier that is connected to the cabinet. Both cables are different. The input cables must be quality-shielded guitar cable, while the cables from the outputs of the amplifiers and the cabinets must be speaker cable. Typically, the speaker cables are not shielded and have two thick wires. Recommended wire thickness are 2×1.5mm2 or 2×2.5mm2. If you need to run long speaker cables, use thicker ones!

The first power on:
I know, I know... Everyone who gets a new toy wants to use it right now without reading manuals, doing quick wiring using some cables with the idea to check how it works as quickly as possible. Same as me! Keep in mind that amplifier switching systems that use a lot of cables MUST be done properly, with attention and patience. Double-check where each cable goes and what type of cables are used! If you are completely sure that everything is connected correctly to the switching system, then comes the first power-on test. Here is how I would do that:

1. Reduce all master volume controls of all amplifiers slightly above zero with levels where you can still hear the guitar but not loud.
2. Power on your switcher.
3. Power on all amplifiers.
4. Select the clean channels for all amplifiers with gain and tone controls as you prefer, or start with all preamp controls at 12 O’clock.
5. Enable a cabinet.
6. Enable the first amplifier.
Now play some clean chords with your guitar. If you can’t hear your guitar through the speaker cabinet, there is something wrong. Do not increase the master level! Keep in mind that the reduced master level is still enough to hear the guitar. Turn off everything and investigate the problem.
If you hear the guitar through the first amplifier, switch to the second and play some chords with it.
When you test all amplifiers with reduced master level and everything works fine, it’s time to rock on!

Power off:
I believe that all amplifier switchers on the market should mute the amplifier input signals when they are turned on, but to prevent some accidental pops, I recommend that you first turn off all the amplifiers and then turn off the switching system.

Plugging or unplugging cables when the whole system is on:
When you have the complete set of amplifiers, cabinets and switcher working, I highly recommend avoiding plugging or unplugging cables on the back. You can do that when all amplifiers are off and routing is safe.

I hope those tips will help you use your amplifier rig smoothly.