In the previous tutorial I looked at effects pedals to broaden the sound. Here you’ll think much bigger by delving into dual amps.
Dual Amps
The thinking here is very simple. If there are two guitarists, there’d be two amps. Consider, for a moment, doing the same thing on your own.
Two amps gives you the ability to expand the sound, mix different amp types and use stereo effects such as delay or chorus. One guitarist can create a truly massive, rich and detailed sound using this method.
Here’s two common configurations:
Stereo
Like any audio system, stereo means having two or more outputs instead of one. However, simply having two speakers—for example, a 2×12 speaker cabinet—isn’t the same.
A truly stereo set-up means spreading the sound beyond that of a single speaker, or sending different sounds to separate speakers.
Wet/Dry
This is similar to stereo, but separates the sound by having the wet amp handling effects, and the dry producing the straight guitar sound.
The advantage of this is getting all of the lush sounds from the effects but maintaining the clarity of the straight guitar sound. Adjusting the wet/dry balance means turning the wet amp’s volume up or down.
Practicalities
Before committing to dual amps, consider these factors:
Cost
Not everything has to be expensive, but there are inherently more parts to a dual rig. Accordingly, the cost’ll be higher.
Storage
All this equipment’s got to go somewhere, so make sure you have the room before you commit.
Transport
Whether it’s gigs or rehearsals, you’ve got to get everything to and from home. Consider whether you have space to transport the extra kit. It’ll come down to what sort of vehicle you have available.
Suitability
More gear means occupying a bigger footprint. If you’re playing pub gigs in cramped conditions, the rig occupying the entire stage won’t make you popular.
Sound Issues
There are two main problems to overcome when using two or more amps.
- Polarity
- Ground Loop
Polarity
Greater distance between amps means a broader sound. Both amps, however, produce the same signal, and if either arrives at the listener’s ears at different times, phase cancellation can occur. In other words, frequencies cancel each other out, creating a thin sound. In this instance, phase reversal is required.
Ground Loop
A whole series of tutorials could be written on this subject, so I’ll try to keep it brief.
Both Amp A and Amp B are mains-powered and are therefore connected to ground in the circuit through their respective power cables.
Once the amps are connected via audio cables, there’s more than one path to ground, creating a closed loop. Stray magnetic fields—usually oscillating at 50 or 60Hz—can induce a current in this loop, creating a consistent humming noise. The solution is to electronically isolate one device from the other.
Under no circumstances should you remove the ground connection from one of the amps. Doing so could have lethal consequences.
Assuming you still want to do this, let’s look at what you’ll need.
The Basics
Obviously, you’ll need two amps.
However, they don’t necessarily have to be the same make and model. Indeed, one of the attractions of this set-up is to create a new sound by blending different amps. For many years Joe Bonamassa used FOUR different amps since no single amp does everything.
This idea makes sense. Some dual, or multi-channel, amps have a great clean sound but a disappointing dirty sound or vice-versa. So choose your preferred clean amp then use a completely separate amp for dirt.
Hooking It Up
For the sake of simplicity, let’s ignore pedals for one moment and simply plug straight into both amps.
One to the Other
Assuming you intend to run both amps simultaneously, one way to connect both amps is to use the effects loop on Amp A.
Running a guitar cable from the SEND of Amp A’s FX loop gives you an output. Where you connect it on Amp B depends on what you want to do with your second amp.
You could connect it to the main input of Amp B. This gives you full control over the sound of Amp B because you can still use its preamp, EQ and so on.
The alternative is to connect Amp A’s SEND to Amp B’s RETURN. Amp B is now aslave to Amp A, as you’ve bypassed Amp B’s preamp.
Either option means that Amp B is receiving the amplified signal from Amp A, and not the original un-amplified signal from your guitar. You also run the risk of the aforementioned ground loop.
Stereo Effects
Some pedals, such as delay and modulation, are stereo in that they have two inputs and two outputs.
As per the previous example, you can route the signal of Amp A through the stereo pedal in order to send a signal to Amp B.
If you do this, you’re no longer getting just the dry signal, and are entering the realms of wet/dry, which I’ll come to shortly.
Amp Switching
Although slaving one amp to another is the simplest way to go, if you want to switch between amps you’ll need a switch. These are known as line selectors or A/B pedals.
Put simply, they split the guitar signal and send it to either Amp A or Amp B. If you have an ABY switch, you can select either amp or both.
Some switches come with phase reversal options, solving the polarity issue described earlier. Switches with isolated transformers will also be helpful should you encounter a ground loop and, whilst more expensive, are the preferred option.
Wet/Dry
As mentioned before, this nominates one amp for your clean or dirty signal, and one amp purely for effects.
Here’s how it works with an ABY pedal.
- The guitar plugs into the ABY pedal
- The ABY pedal is set for Y so that both amps work simultaneously
- Output A goes to Amp A
- Output B goes to Amp B via your effects pedals
You can choose between Output B plugging into the main input of Amp B, or into its FX loop RETURN. The difference is whether or not you want your effects to pass through the amp’s preamp.
There are of course many other ways to set up either stereo or wet/dry rigs, but the ones I’ve presented here are the simplest.
Conclusion
A lot more complicated and expensive method, but one that produce huge results. Bear in mind:
- Polarity and ground loops
- Try different amps in combination
- Experiment with how you connect the amps
- Factor in cost, transportation, and so on
- Have fun, be experimental!
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