The AMT GR-4 is a programmable guitar switching system with four loops, made by AMT Electronics. AMT describes it as a multifunctional floor passive guitar switchboard with microcontroller-based control ability, and the unit is listed as available now1. Alongside the switching, it carries an analog preamp, a power amp section with nine types, IR cab simulation, a parametric EQ and a compressor, so it can act as more than a loop router2.
Loops and switching modes
The GR-4 offers two ways of working its four loops. In fully programmable mode, each of the four programs can be set to a separate combination of active loops, so one button press brings up a whole pedalboard arrangement. In independent mode, each loop is switched on and off by its own separate button, the way a plain loop box works1.
The switching itself is done by relays in a fully passive sound path, which AMT says keeps the audio wiring passive while the microcontroller handles the control1. The input buffer can be shut off, and AMT positions it as compensating for the impact of a long guitar cable1.
Other switching-era conveniences on board:
- External tuner output, keeping a tuner out of the main path1
- Noise gate as a global setting3
- Built-in power splitter, so one power adapter can feed a few more external pedals1
Preamp, power amp and cab sim
Beyond routing, the GR-4 includes tone-shaping stages that AMT lists as follows2:
| Feature | What it offers |
|---|---|
| Analog Preamp | Clean / Low gain / High gain modes2 |
| Power Amp | 9 types2 |
| IR cabsim | 1 IR for both L/R channels per preset2 |
| Parametric EQ | Pre/Post2 |
| Compressor | Listed as a feature2 |
The same feature set appears in AMT's own demo video for the GR-4, which names the analog preamp with its Clean, Low gain and High gain modes, the power amp with nine types, the IR cab sim with one IR for both left and right channels per preset, the parametric pre/post EQ and the global noise gate3. The preamp and power amp sections sit alongside the switching, so a player can use the GR-4 as the front end of a rig built around external pedals and a power amp, rather than adding separate preamp or speaker simulation pedals. For context on where it sits, see the site's pages on switching pedals, preamp pedals and speaker simulation pedals.
Power
The GR-4 runs on 12V, and AMT includes its noiseless 12V power supply with the unit, with EU or US plug. Power consumption is given as 0,15-0,25A, depends on modes1. The built-in power splitter means the same adapter can also feed a few more external pedals1.
The included supply is 12V, and the current draw of 0,15-0,25A, depends on modes1, is worth accounting for if you plan to share the adapter with other pedals through the splitter.
Using several AMT preamps with the GR-4
AMT gives a direct recipe for rigs built around its preamps. To switch between the P-2, R-1, M-1 and E-1 preamps in one touch, the maker says2:
"You just connect all of these 4 preamps output to GR-4 and then GR-4 to power amp and that's it2."
AMT Electronics product page2
In other words, the four preamp outputs connect to the GR-4, and the GR-4 then feeds the power amp, so switching happens in one touch2.
Videos
Eugene Odnoval
Questions
How many loops does the AMT GR-4 have?
The AMT GR-4 is a programmable guitar switching system with four loops. In fully programmable mode, each of the four programs can hold its own combination of active loops, while independent mode lets you switch each loop on and off separately with its own button.
Is the AMT GR-4 signal path passive?
Yes. AMT Electronics describes the GR-4 as a passive floor switchboard with a fully passive sound path, with the switching done by high-quality relays and control handled by a microcontroller. The unit also has a shut-off input buffer that compensates for the effect of a long guitar cable.
Does the AMT GR-4 have a tuner output?
Yes, the GR-4 has an external tuner output, so you can keep a tuner connected and out of the main signal path. The unit also offers a global noise gate setting and a built-in power splitter for feeding other pedals.
What power supply does the AMT GR-4 use?
The GR-4 runs on 12V, and AMT Electronics includes its noiseless 12V power supply with EU or US plug. Power consumption is 0.15 to 0.25A depending on modes, and the built-in power splitter lets one adapter feed additional external pedals.
Can the AMT GR-4 power other pedals?
Yes. The GR-4 has a built-in power splitter that allows one power adapter to feed a few more external pedals alongside the GR-4 itself, which AMT says draws 0.15 to 0.25A depending on modes.
How do I switch between several AMT preamps in one touch with the GR-4?
AMT says you connect the outputs of all four preamps, such as the P-2, R-1, M-1 and E-1, to the GR-4, then connect the GR-4 to the power amp. That setup lets you change between the preamps in one touch.
Sources (3)
- AMT GR-4, AMT Electronics, 2026
- AMT GR-4, AMT Electronics (media.amtelectronics.com), 2015-07-17
- AMT Electronics GR-4, Media center of AMT Electronics
