References

Documentation:

Rig pictures

Design and development

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[1] It's not a replacement for any of our current products.

[2] That's the target market. We have more products in the pipe for that market.

[3] Its primary application is live performance and the UI was designed with that in mind.

[4] It uses premium analog components and converters. The input stage is FET and the op-amps are all "iPolar". None of this cheap CMOS stuff that other products are using.

[5] Adding MIDI clock should be easy. The VP-4 code was frozen before it was implemented in the Axe-Fx III and the FM-3/9. The only development allowed after code is frozen is bug fixing. We're already talking about adding a Looper and an IR player block. The product focus was on three things: quality, simplicity and flexibility. Re. quality. It uses premium analog components and converters. The input stage is FET and the op-amps are all "iPolar". None of this cheap CMOS stuff that other products are using. No product will ever satisfy everyone. If low price is your primary concern then the product is not for you. If having lots of simultaneous effects is your primary concern the product is not for you. If having up to four, high-quality effects from the Axe-Fx III in a small, pedal board-friendly format is what you want then this product is a compelling choice.

[6] The Axe-Fx III and FM9 have essentially the same analog path as the FX8. The VP4 is similar and offers the same fidelity.

Dimensions and weight

Weight: 3 lbs 7 oz (1.56 kg).
Dimensions: 10.00" x 6.31" (254mm x 160.3mm).

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[7] I measured the protrusion of the jack with the greatest depth (SPDIF) and it's about 9mm. Cables would be extra.

[8] Using anything other than the factory-provided feet and screws will void your warranty. The approved screws are M3.5x8mm, with approximately 5mm protruding into the VP4 chassis. Internal components are aligned with the screw holes, so if third-party screws extend too far, they may cause damage to these components. Such damage will be identifiable and not covered by the warranty. For safe mounting, Velcro is the recommended solution.

Processing

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[9] The VP-4 uses the Axe-Fx III DSP's little brother. It's a single core version with the same instruction set so porting stuff from the Axe-Fx III is almost trivial.

[10] The VP4 uses a SoC. It has an ARM Cortex A15 core and a C66x core along with a bunch of peripherals. The DSP in the Axe-Fx III would be too power-hungry for this application.

[11] It's quite possible we could add more blocks in future firmware. I can envision, say, four switchable blocks and two fixed blocks per preset. The fixed blocks are always on. The switchable blocks can be bypassed/engaged. Or four fixed blocks and four switchable blocks. It's just software. It's a fairly powerful processor, more powerful than the FX8 had, but our algorithms have continued to increase in complexity and require more processing power than things did back in the FX8 days.

Latency

The latency of the unit is 1.2 ms. [12]

Read this: Latency.

Screen

480 x 272 high contrast color LCD.

No touch screen.

Power

Power connector: 2.1mm, negative center. Wall wart included (9V DC, 1.3A).

The unit has a power button.

No internal battery.

This user forum thread discusses power supplies.

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[13] The maximum current draw is 1.3A. Typical draw is less than 1A but we cannot guarantee proper operation if using a supply below the rated specification. It can run on 12V and the current draw will be lower in this case.

Firmware

The firmware is upgradeable, allowing the addition of new features and bug fixing.

Download the latest official release here.

PRE and POST position

The VP4 can be used before an amp (PRE) or in its effects loop (POST).

Sets of factory presets are configured specifically for Pre and for Post (series of parallel) operation. A list is included at the the end of its owners manual.

Analog I/O

Input

Mono/stereo input, 2x 1/4" TS jack, max +20dBu (instrument level / line level).

The VP4 defaults to mono input. Switchable in the Setup menu.

Input impedance: variable (adjustable per preset).

Adjustable Input pad in the Setup menu, with auto correction. The manual states that the VP4 comes set 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

If the input of the VP4 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 VP4, 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” and set the desired value. While "4CM Routing" is enabled, a common input pad setting is shared by both PRE and POST inputs. Excessive levels at either of these will cause the automatic pad setting to be applied to both.

Output

1/4" TS L/R (mono/stereo), max +16dBu, 600 Ohm. Unbalanced. No Humbuster.

Defaults to stereo output. Switchable in the Setup menu.

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[14] All of the outputs on the VP4 are unbalanced.

[15] 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.

Output is unity gain, unless programmed otherwise.

4CM

4CM (Four Cable Method) is supported (mono only).

To enable this, turn on 4CM Routing in the Setup menu. Only presets configured specifically for 4CM will work with this setup. Using a preset that IS NOT configured for 4CM will switch the VP4 to BYPASS and defeat all processing.

Global settings for Input Mode and Output Mode (except "MUTE") are IGNORED when 4CM Routing is enabled, and only the left channel of the last Pre- or Post effects is passed to the respective output. Mono effect types and settings are therefore recommended for a 4CM rig. Remember that many stereo effects have controls like Stereo Spread or Master Pan, which can be used to eliminate differences between right and left channels. The Input Gate is applied at the Pre input, which also feeds the tuner. The master Preset EQ, Main Levels, and Scene Levels are applied at the Post output. The Input Pad setting affects both the PRE and POST inputs. If your Amp's send level is particularly hot, this might require a higher pad setting than your guitar.

A set of factory presets is configured specifically for 4CM. See a list of VP4 factory presets at the end of its Owners manual.

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[16] In L = Guitar
Out L = Preamp In
In R = Preamp Out
Out R = Power amp In

[17] It has the analog path from the Axe-Fx III (which evolved from the FX-8). Beta testers report that it "plays nicely" with difficult fx loops.

[18] The Axe-Fx III and FM9 have essentially the same analog path as the FX8. The VP4 is similar and offers the same fidelity.

[19] SPDIF is not supported with 4CM. As you observed, the SPDIF is always stereo.

Insert

To use the VP4 as an analog insert, for example with the FM3, check the Owners Manual.

Headphones

In some scenarios the VP4 is the last device in the chain. It's an effects-only unit and therefore doesn't have a headphones port. If you want to listen to its output directly, without an amp or audio system, you need a headphones amp. A small device will do, such as a Rolls PM50se.

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. Download the driver here.

Read this: USB.

SPDIF

SPDIF can be used to digitally connect the VP4 to an 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 VP4 always mirrors the signal at the analog outputs.

Read this: Digital I/O and audio.

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[20] The analog input has to be buffered as well. In most (all?) processors you buffer data up in frames. A typical frame size is, say, 32 samples. You can't start processing that frame until it is full. When it is full you ping-pong and start filling the opposite buffer. The physical latency of SPDIF is usually no more than a sample or two. A typical A/D converter has a latency of 10-20 samples. The same thing happens at the output. You read from an output buffer and when it's empty you ping-pong to the opposite buffer. A typical D/A has a latency of, again, 10-20 samples. A SPDIF output has only a sample or two. So, in the case where you use a frame size of 32 you get a total buffer latency of 64 samples. If we assume the A/D and D/A are 16 samples each the total latency is 96 samples. If you use SPDIF you'd have about 30 samples less latency.

[21] SPDIF is not supported with 4CM. As you observed, the SPDIF is always stereo.

Analog bypass

The VP4 allows a buffered analog bypass mode. This passes the signal directly from input to output without digital conversion, latency, or processing.

This can be enabled through a switch or automatically. To have analog bypass activate automatically when all four effects are bypassed, set the option in the Setup menu to ON.

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[22] We considered analog dry-through early in the design phase but it just causes more problems than it's worth. If it were a dedicated delay or reverb device then it would make sense but once you add drives and wahs and EQs it makes things too confusing for the average user.

Onboard switches

The 4 foot switches have colored indicators, no scribble strips.

They support Tap and Hold functions (e.g. to switch channels). Watch the video at the bottom to se how to select channels.

Remote control

MIDI

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

The Boss BMIDI-5-35 cable has been tested and works with the VP4 to connect to 5-pin MIDI gear.

The VP4 supports:

Sending and receiving Program Changes (PC),
Receiving Control Changes (CC),
MIDI-over-USB,
MIDI clock (receive only, currently),
Software MIDI Thru,

A table in the manual translates MIDI Program Changes to VP4 presets.

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 therefore does not support connections to FC-6 and FC-12 foot controllers.

Amp switching

The VP4 itself does not provide relays to switch amp channels.

It can connect through MIDI to a relay switcher to perform that duty.

Suggestions:

User interface

Compared to the Axe-Fx III, FM3 and FM9, the UI is simplified and streamlined.

Press Home+Save together to enter the Mode Select menu. Select between: Preset, Scene, Effects, 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.

Press Enter+Exit together to enter the Setup menu.

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 arrow to get to other pages.

When editing parameters on the hardware, press Page Left+Right together to enter Expert Edit mode. Expert Mode includes advanced parameters.

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[26] 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.

Presets, scenes and channels

The unit has 104 presets, supports 4 |scenes per preset and 4 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. Presets can be configured for PRE, POST or 4CM. A list of factory presets is included at the the end of the Owners manual.

Switching between presets, scenes and channels is gapless.

VP4 presets and blocks are not compatible with Fractal Audio's other processors, nor vice versa.

Download the latest factory presets here.

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[27] There are enough dissimilarities between the VP4 and the other products, that preset compatibility is not practical.

[28] (are saved blocks (no entire presets) transferable?0
No, many of the effects have changes that facilitate the simplified BASIC mode interface.

[29] Block library entries are not cross compatible between VP4 and other products. Keeping the translator in sync across products/firmware versions is a can of worms, and b) the VP4 also has a few small differences in terms of how things are handled internally. You can copy settings by hand and things will sound the same, but see the note in the purple box on p. 26 of the manual.

Effects

Supported effects blocks:

There is a Noise gate at the input, before the 4 effects, and a 10-band EQ at the output of each preset, which are always "on".

The VP4 does not provide amp and cab modeling. Also, compared to the FM3, there's no Multiband Compressor, Ten-Tap Delay, Mixer, Looper, Send/Return and Multiplexer.

Compared to the Axe-Fx, FM3 and FM9, the unit has:

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.

Effects 2+3+4 can be routed in parallel with the previous effect.

The blocks support Fractal Audio's system of Controllers and modifiers.

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[30] (Can it run a Dual Detune, Reverb, Delay and a Plex Delay simultaneously, in a non-economy algo mode?)
Yes

[31] it is totally up to date with Axe-Fx III in all effects.

[32] We're already talking about adding a Looper and an IR player block.

[33] The VP4 uses the newest pitch detector from the Axe-Fx III.

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

[35] 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.

VP4-Edit editor

VP4-Edit is the editor for the VP4, with Fractal-Bot built-in.

Download the current version of VP4-Edit here.

For Windows computers, the editor requires a driver. Download the driver here.

Videos

VP4

Contents