AM4 amp modeler

Information is being added to this page as it becomes available

References

Make sure to read the excellent owners manual!

• Product page
• Downloads
• User forum
• Introduction forum thread
• Wiki pages

Documentation:

• Owners Manual
• Quick Start Guide

Pictures

See “Owners show their AM4 boards” for a discussion how forum members are using their AM4 units.

Design and development

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[...] ...

Comparing the AM4 to the VP4 and the FM3

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Dimensions and weight

Weight 

3 lbs 9 oz (1.63 kg).

Dimensions 

10.00" x 6.31" (254mm x 160.3mm).

Processing and memory

Compared to other FAS devices, the overall CPU limit is a bit higher: 85%.

Be aware that CPU metering is dynamic; the amp modeling running on the core is actively metered during play.

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[1] The processor in the AM4 is faster than the VP4.

Latency

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[...] ...

See Latency for more information.

Screen

The display is a 480 x 272 high-contrast color LCD.

The AM4 does not have a touchscreen.

Power

The power connector is a 2.1mm barrel connector, with a negative center. The power-supply (9V DC, 1.5A) is included. The unit has a power button.

Do NOT use an AC supply. It WILL damage the unit.

The AM4 powers up in a few seconds. When the AM4 is powered on, DynaCabs begin to pre-load automatically in the background. You may experience brief slowdowns while cabs are loading. This is normal and ends once all cabs have finished loading.

Firmware

The firmware is upgradeable, allowing adding new features and bug fixes.

You can download the latest official release from the AM4 downloads page.

Analog I/O

Input

Single mono input, 1/4" TS jack, max +20dBu (instrument level).

Input impedance is variable and is adjustable per preset.

The Input pad in SETUP is adjustable, with auto correction. The manual states that the AM4 is pre-configured for a typical guitar with hot pickups. If input clipping occurs, an ”IN CLIP“ warning is displayed and the Input Pad setting is temporarily increased.

OWNERS MANUAL

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If the input of the AM4 clips persistently, the unit will automatically increase the Input Pad setting. When this occurs, the word “Auto” will appear next to the Input Pad value, for example: “12 dB (Auto)”, indicating that the pad was automatically increased to 12 dB. When you reboot the AM4, the automatic setting is cleared, and the last manually selected value is restored. If you want to make the automatic pad setting permanent, just turn the Input Pad knob one “click” to clear “Auto”.

Like the VP4, the input range of the AM4 is the same as an 18V pedal.

Output

1/4" TS L/R (mono/stereo), max +16dBu, 1 KOhm. Balanced. Line level. No Humbuster.

The output can be switched between mono and stereo in SETUP.

See Mono vs stereo

The AM4 has a dedicated SPLIT output mode, which sends the signal with cab modeling to Left (for FOH), and a "no cabinet" signal to Right. Each output operates in summed mono. Note that this will affect playback through headphones.

Similar to the VP4:

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[2] Humbuster is not necessary because it's DC powered and the chassis is floating. Hum occurs due to ground loops. If equipment is AC powered the chassis must be grounded by law. This introduces ground loops when using unbalanced connections. The correct solution is for everything to be balanced but the industry seems reluctant to embrace that.

No 4CM

4CM (Four Cable Method) is not supported.

Insert

The AM4 does not provide a effects loop.

But it has a fixed insert point between the internal effects and the balanced outputs. Use these to connect outboard gear while preserving the clean, low-noise performance of the balanced outputs for FOH without needing a direct box.

The insert is fixed in hardware and cannot be repositioned or switched on/off.

It applies only to the main outs and is not heard on USB or SPDIF.

For mono, use a standard patch cable. For stereo, use a TRS-to-dual-mono insert cable (tip = left, ring = right).

Insert Send: 1/4" jack TRS (tip=Left, ring=Right), 1 KOhm, 16dBu.

Insert Return: 1/4" jack TRS (tip=Left, ring=Right), 1 MOhm.

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[3] The idea is you put your pre effects before the unit and your post effects (should you need any) in the insert. The outputs of the AM4 are balanced and designed to be sent directly to FOH and/or monitors. If you just put your post effects after the unit you would then need a DI to go to FOH.

[4] A freely positionable loop would require another stereo A/D and D/A would would increase power consumption, latency when the loop is active, noise, etc. Its purpose is simply to get your post effects before the DI. A typical pedal board might be something like: Wah -> Fabled Unicorn Devices (FUD) Dry Hump III Overdrive -> AM4 -> Lunar Electronics Space Echo Plus. The Space Echo Plus is your typical pedal with unbalanced I/O. You put in the insert loop on the AM-4 and the outputs of the AM-4 are balanced for FOH/Monitors.

Headphones

The AM4 has a 3.5mm stereo headphones port.

Impedance is 35Ω. Recommended headphone impedance is less than 600Ω.

Digital I/O

Converters

24-bit, 48kHz (fixed).

Dynamic range is 114 dB, 20-20k frequency response.

USB

USB-C port for data and audio.

MIDI-over-USB is supported.

USB Audio 2.0 provides 4 channels (2x2) at 48kHz.

• OUT channels 1+2: processed output
• OUT channels 3+4 : unprocessed (copy of inputs)
• IN channels 1+2: send incoming USB Audio directly to outputs
• IN channels 3+4 : process incoming USB Audio and send to outputs

Windows computers require a software driver which is available on the AM4 Downloads page.

See USB for more information.

Note that an USB connection can create a a ground loop, resulting in noise or hum. Solutions:

• Laptop: switch between AC power and battery power.
• Use balanced cables.
• Insert a USB ground loop eliminator (Type-C > Type-C) between AM4 and computer.
• Try an audio isolation transformer between AM4 and device.

SPDIF

SPDIF can be used to digitally connect the AM4 to an VP4, FM3, FM9 or Axe-Fx, through RCA connectors, at 48kHz fixed sample rate.

A digital connection avoids the necessary A/D and D/A conversion and inherent latency that comes with analog-to-digital connections.

The SPDIF output of the AM4 always mirrors the signal at the analog outputs, except for the insert (see above).So, 'inserted' devices are not heard at the S/PDIF output.

IMPORTANT: When connecting the AM4 and VP4 via SPDIF, make sure to maximize the SPDIF In Level of the receiving device in SETUP to prevent loss of signal level.

Read Digital I/O and recording for more information.

Levels

The AM4 has two stages that affect the overall volume.

• Internal levels operate within presets. These include Input Level, Scene Levels and Preset Level.

• Analog output level is controlled by the top-panel knob. Set it to the preferred but avoid overdriving the output stage or connected device(s). The Analog Levels meter shows how close you are to clipping, and an OUT CLIP warning will appear in the title bar across all pages if clipping occurs.

The AM4 outputs operate at adjustable line level, not at fixed unity gain.

Onboard switches

The four foot switches have colored indicators, but no scribble strips.

They support Tap and Hold functions (e.g., to switch channels). Factory default is the so-called Gig Mode. You can customize the functions.

Remote control

MIDI

The unit has 3.5 mm (1/8”) MIDI IN and OUT ports. Adapters are available from Fractal Audio.

The Boss BMIDI-5-35 cable has been tested and works with the AM4 to connect to 5-pin MIDI gear.

The AM4 supports:

• Sending and receiving Program Changes (PC)
• Sending and receiving Control Changes (CC)
• MIDI-over-USB
• MIDI clock (receive only, currently)
• Software MIDI Thru
• Syncing scenes with the VP4

A table in the manual translates MIDI Program Changes to AM4 presets.

See MIDI for more information.

Expression pedals and external switches

The unit supports two expression pedal connections (TRS, 10–100 kΩ max), or two single TS external switches (momentary or latching).

The unit does not provide FASLINK connections and does not support connections to FC-6 and FC-12 foot controllers foot controllers.

Amp switching

The AM4 itself does not provide relays to switch amp channels, but it can connect through MIDI to a relay switcher to perform that duty.

Possible solutions include:

• MIDI Solutions Relay
• Suhr MicroMIDI Control
• Voodoo Lab Control Switcher
• Pirate MIDI CLiCK
• RJM Mini Amp Gizmo (no longer available from RJM but might be available used. The manual is currently available online.)
• EM

User interface

Compared to Fractal's modelers, the AM4 UI is simplified and streamlined, like the VP4.

Press HOME+SAVE together to enter the “Mode Select” menu which allows you to select between Preset, Scene, Effects, Amp and Tuner/Tempo. The mode determines what's displayed on the LCD, how the Select knob operates and what the switches do.

The factory default's “Gig Mode” configuration makes it easy to select presets, scenes, effects, channels, tuner and tap tempo. The startup mode can be set in Setup.

Press ENTER+EXIT together to enter Setup.

To edit parameters on the hardware, turn SELECT in Effect mode to highlight a block, press ENTER to edit the block, turn the corresponding A-D knob to adjust the value, PAGE LEFT or PAGE RIGHT to get to other pages.

When editing parameters on the hardware, press PAGE LEFT+PAGE RIGHT together to enter “Expert Edit” mode. Expert Edit includes advanced parameters. Press EXIT to quit Expert Edit.

On the home page in FX Mode, select the desired block, hold the ENTER button, and turn SELECT to move.

Similar to the VP4:

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[5] Behind the scenes it's the architecture from the Axe-Fx III. There's still a grid and scenes and channels, etc. It's just that it's mostly hidden from the user and simplified.

Tip: If you don't need scene names, use the available space to indicate the specific effect types instead. Insert spaces to visually align them.

Presets, scenes and channels

The unit has 104 presets, supports four scenes per preset and four channels per effect block.

The presets are organized into 26 banks, each identified by a letter from A to Z. Within each bank, there are four presets, numbered 1 through 4. A list of factory presets is included at the the end of the Owners manual.

Each block has 4 channels.

Switching between presets, scenes and channels is gapless.

AM4 presets and blocks are not compatible with Fractal Audio's other amp modelers, nor vice versa.

The latest factory presets are available on the AM4 downloads page. Here's the list from the manual:

Amp and cab modeling

The Amp block and Cab block are now integrated into a single block.

Only when selecting the SPLIT output mode, the Cab is repositioned at the end of the chain.

Some models of a specific amplifier are now consolidated.

Amp Mode lets you quickly access amp parameters and switch amp/cab channels, and also provides a boost.

Some amp models have been deprecated:

• Brit Pre model
• old Vibrato Verb
• Legend 1 model
• Chieftain 2 model
• Dizzy V4 Blue models
• Thordendal models

Loading an amp model automatically selects an appropriate cab: <q?Amp>DynaCab linking. This can be disabled in SETUP.

To selectively keep Cab settings when changing the amp type, hold ENTER while turning SELECT, then release ENTER to apply the change. AM4-Edit, you can hold SHIFT while selecting a new amp from the list to achieve the same result.

DynaCabs are included. Legacy factory cabs are not included. IRs can also be imported (256 slots), supporting UltraRes. The Cab Blend parameter replaces individual Cab Level controls.

Regarding advanced Amp block parameters:

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[6] The list is trimmed down a bit but the essential stuff is in there.

Other effects

Available effects on the AM4:

• Chorus block
• Compressor block
• Delay block
• Drive block
• Enhancer block
• Filter block
• Flanger block
• Gate/Expander block
• GEQ block
• PEQ block
• Phaser block
• Reverb block
• Rotary block
• Tremolo/Panner block
• Volume/Panner block
• Wah block

Compared to the other Fractal Audio devices, the AM4 does NOT have: Formant, IR Capture, IR Player, Megatap Delay, Multitap Delay, Pitch, Plex Delay, Resonator, Ring Modulator, Synth, Tone Match, Vocoder.

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[7] The choice of effects was so that you couldn't overload the processor. Running a Reverb and a Plex plus the Amp block would exceed the processor's bandwidth. Engineering is all about tradeoffs. It's a constant juggle between price, size, features, power consumption and performance. As such, no product will be perfect for everybody. In an ideal world DSPs would use no power and have infinite clock speeds. Until then products will have to make compromises. At some point we can revisit the effects inventory.

There is a Noise gate at the input, before the four blocks, and a 10-band EQ at the output of each preset, which are always on.

Like the VP4, there are some differences with the larger modelers:

• Additional tweaked types, such as Vibrato and single voice Pitch types
• Tweaked MIX Law for time-based effects
• Mode switch in some Drive types instead of multiple types (e.g. Timothy)
• Some renamed types

3 of the 4 blocks can be routed in parallel instead of series.

The blocks support Fractal Audio's system of Modifiers and controllers.

Similar to the VP4:

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[8] The mix law in many blocks is different to suit the "all effects before the amp" crowd better.

[9] The sweetened mix law places a wider range of knob motion in the portion of the curve where the delay is quieter.

This replicates the way pedals that are designed for use in front of an amp work because the amp's compression reduces the difference between the quiet echoes and the louder dry signal.

AM4-Edit software editor

AM4-Edit is the editor for the AM4, with Fractal-Bot built-in.

You can download AM4-Edit, along with the Windows driver, firmware and factory presets updates, from the AM4 downloads page.