Electric guitar interface setup: Difference between revisions

Revision as of 06:55, 20 September 2026

This guide covers setting up an electric guitar with NixOS to achieve professional, low-latency audio processing. It targets live playing with round-trip latency (RTL) under 6 ms using the modern PipeWire and WirePlumber stack.

⚠︎

Warning: Always start testing new signal chains with the monitoring volume at minimum. A sudden, loud feedback loop can be generated during loopback testing. Increase the volume gradually only after the plugin is open and stable.

The digital signal chain for a guitar consists of:

Instrument-level signal from Hi-Z pickups.
Analog-to-digital conversion via an external audio interface.
Real-time processing on NixOS using a low-latency kernel and specialized software.

Note: Software-reported latency values are often inaccurate. Physical measurement via a loopback test is mandatory for verification.

Quick Start

If you want to get sound from your guitar within 15 minutes, follow these minimal steps. Ensure you have a compatible USB audio interface (see Hardware section).

Connect your interface directly to the motherboard (rear USB port).
Add the following minimal configuration to your /etc/nixos/configuration.nix:

  services.pipewire = {
    enable = true;
    alsa.enable = true;
    alsa.support32Bit = true;
    pulse.enable = true;
    jack.enable = true;
    wireplumber.enable = true;
    extraConfig.pipewire."92-low-latency" = {
      "context.properties" = {
        "default.clock.rate" = 48000;
        "default.clock.quantum" = 128;
        "default.clock.min-quantum" = 32;
        "default.clock.max-quantum" = 512;
      };
    };
  };
  security.rtkit.enable = true;
  environment.systemPackages = with pkgs; [ carla neural-amp-modeler-lv2 lsp-plugins pavucontrol ];

Rebuild and switch:

sudo nixos-rebuild switch
systemctl --user restart pipewire wireplumber

Open pavucontrol, go to the Configuration tab, and set your interface profile to Pro Audio.
Launch carla, add the Neural Amp Modeler plugin, and connect your interface's input to the plugin and the plugin's output to the interface.

Hardware

Standard PC line-ins are unsuitable for guitar due to impedance mismatch. You need a dedicated interface with a Hi-Z (Instrument) input.

Why special cards are needed

Linux supports USB Audio Class 2.0 (UAC2) compliant devices natively. However, Thunderbolt audio interfaces generally do not work on Linux due to proprietary, closed protocols. Even high-end interfaces from Focusrite (Clarett Thunderbolt), RME, and Universal Audio will not function properly. Always choose USB interfaces, unless you are willing to use an experimental, reverse-engineered driver that currently only supports basic control routing without PCM audio streaming.

The clipping problem

⚠︎

Warning: Input headroom and clipping: Many budget and mid-range interfaces have limited headroom on their Hi-Z inputs. Modern high-output passive or active pickups can cause digital clipping at the ADC stage before the signal reaches 0 dB in your DAW, even with the gain knob at minimum.

The input headroom capacity is measured in dBu. A higher value means the interface can handle louder input transients without clipping.

Device	Headroom (dBu)	Status
PreSonus Studio HD2 / 24c	21 dBu	✅ Excellent
MOTU M2 / M4	16 dBu	✅ Good
Focusrite Scarlett 2i2 3rd Gen	12.5 dBu	⚠️ Average
Audient iD14 MkII	9 dBu	❌ Clips easily
Steinberg UR44	8.5 dBu	❌ Clips easily

Recommendations

For NixOS, plug-and-play compatibility is critical. Choose interfaces with high dBu ratings to preserve the natural attack of your guitar.

Device	Notes
Focusrite Scarlett 4th Gen (Solo/2i2/4i4)	Plug-and-play. Requires disabling MSD Mode (hold 48V button while powering on). `alsa-scarlett-gui` v1.0 beta 9 works natively.
Focusrite Scarlett 4th Gen (16i16/18i16/18i20)	Requires kernel ≥ 6.12, `fcp-support`, and a firmware update via `alsa-scarlett-gui`.
MOTU M2 / M4	Native ALSA kernel support (requires kernel ≥ 6.1). Direct hardware mixer control via `alsamixer`. Exceptionally stable USB-C latency.
Audient iD4 / iD14 (All Generations)	Fully functional on NixOS. Note: iD14 MkII has limited Hi-Z headroom (9 dBu).

DI-box

If you already own a budget interface with low dBu and experience clipping, use a passive DI-box (e.g., Palmer PAN 01, ART DTI). A passive DI-box naturally attenuates the signal by ~20–23 dB, converting it to a balanced microphone level. Connect the DI-box between your guitar and the interface's XLR input.

System configuration

Add the following snippets to your /etc/nixos/configuration.nix. This configuration is optimized for high-performance CPUs.

PipeWire

Configure PipeWire with global low-latency defaults and disable node suspension to prevent audio pops on USB interfaces. Note that WirePlumber 0.5+ (standard in NixOS 26.05) supports SPA-JSON syntax, which is preferred over deprecated Lua scripts.

  services.pipewire = {
    enable = true;
    alsa.enable = true;
    alsa.support32Bit = true; # Required for yabridge/wine VST bridging
    pulse.enable = true;
    jack.enable = true;
    wireplumber.enable = true;
    
    # Global low-latency defaults
    extraConfig.pipewire."92-low-latency" = {
      "context.properties" = {
        "default.clock.rate" = 48000;       # Fixed rate avoids resampling latency
        "default.clock.quantum" = 128;      # ~5 ms latency at 48 kHz
        "default.clock.min-quantum" = 32;   # Allows top-tier interfaces to achieve ~1.5 ms
        "default.clock.max-quantum" = 512;
      };
    };

    # Disable node suspension and fix crackling on problematic USB interfaces
    wireplumber.extraConfig."99-disable-suspend" = {
      "monitor.alsa.rules" = [{
        matches = [
          { "node.name" = "~alsa_input.*"; }
          { "node.name" = "~alsa_output.*"; }
        ];
        actions = {
          update-props = {
            "session.suspend-timeout-seconds" = 0;
          };
        };
      }];
    };
  };

Kernel and performance

Modern mainline kernels include merged PREEMPT_RT patches. Dynamic preemption (preempt=full) provides best-effort low latency without the overhead of a dedicated RT kernel. CPU frequency scaling must be locked to prevent sleep-state latency spikes.

  boot.kernelPackages = pkgs.linuxPackages_latest;
  boot.kernelParams = [ 
    "preempt=full"              
    "usbcore.autosuspend=-1"    # Prevent USB audio interface sleep
  ];

  services.power-profiles-daemon.enable = false;
  powerManagement.cpuFreqGovernor = "performance";
  programs.gamemode.enable = true; # Can elevate priorities for real-time audio applications

Note: Always verify your bootloader configuration after changing kernel parameters to ensure they are applied correctly.

Real-time scheduling

RTKit handles real-time privileges via D-Bus/Polkit. Critical PAM limits must be set to allow unlimited memlock and high real-time priority for audio buffers.

  security.rtkit.enable = true;
  
  security.pam.loginLimits = [
    { domain = "@audio"; item = "memlock"; type = "-"; value = "unlimited"; }
    { domain = "@audio"; item = "rtprio"; type = "-"; value = "99"; }
    { domain = "@audio"; item = "nice"; type = "-"; value = "-19"; }
  ];
  
  users.users.yourname.extraGroups = [ "audio" ]; # Replace 'yourname' with your username

Plugin search paths

Crucial for NixOS DAWs to find plugins reliably in Wayland/X11 sessions.

  environment.variables = let
    makePluginPath = format:
      (pkgs.lib.makeSearchPath format [
        "$HOME/.nix-profile/lib"
        "/run/current-system/sw/lib"
        "/etc/profiles/per-user/$USER/lib"
      ]) + ":$HOME/.${format}";
  in {
    LV2_PATH = makePluginPath "lv2";
    VST3_PATH = makePluginPath "vst3";
    CLAP_PATH = makePluginPath "clap";
  };

Software installation

  nixpkgs.config.allowUnfree = true; # Required for REAPER, Bitwig Studio
  environment.systemPackages = with pkgs; [
    # --- Utilities & routing ---
    qpwgraph            # Visual patchbay for PipeWire (v1.0.4+)
    pwvucontrol         # Modern native PipeWire volume control (v0.5.3+)
    pavucontrol         # Fallback for Pro Audio profile selection
    pw-top              # Real-time CPU usage per audio node
    easyeffects         # System-wide real-time EQ and effects
    
    # --- DAWs ---
    ardour
    reaper
    bitwig-studio       # Native Linux commercial DAW, excellent CLAP support

    # --- Plugin hosts ---
    carla               # Modular plugin host, supports Windows VST via yabridge

    # --- Standalone guitar processors ---
    guitarix            # Includes native NAM and RTNeural module support

    # --- Plugins (LV2/CLAP) ---
    neural-amp-modeler-lv2  # NAM: AI captures of real tube amps (v0.2.3, supports A2)
    proteus               # Neural network modeling (LSTM) by GuitarML
    lsp-plugins           # Professional EQ, compression, IR loader (now available in CLAP)
    calf                  # Vintage-style effects
    dragonfly-reverb      # High-quality algorithmic reverb
    gxplugins-lv2         # Guitarix project pedals as standalone LV2
    kapitonov-plugins-pack # Profile-based traditional amp modeling (VST3/LV2)
    chow-centaur          # Klon Centaur emulation
    chow-phaser           # Phaser emulation
    ratatouille-lv2       # Dual neural modeler (loads .nam, .json, .aidax)

    # --- Practice & learning ---
    tuxguitar
    hydrogen

    # --- Windows VST compatibility ---
    yabridge
    (yabridgectl.override { wine = wineWow64Packages.stable; }) # Explicit 64-bit Wine path
    wineWow64Packages.stable  # Note: wineWowPackages is deprecated
  ];

Digital audio workstations

Software	Purpose	Notes
Ardour	Professional recording, mixing, editing	For absolute minimum RTL (< 5 ms), use the ALSA backend (bypasses PipeWire). Warning: ALSA locks the device exclusively — no other app can produce sound.
REAPER	Commercial DAW, lightweight, scriptable	Uses PipeWire-JACK natively. Excellent Linux support. Can be declaratively configured via Reaper HM Flake.
Bitwig Studio	Modern commercial DAW	Native Linux support. Superior CLAP format integration. PipeWire-JACK is often more stable out-of-the-box than Direct ALSA.

Amp simulators and neural modelers

Software	Purpose	Notes
Neural Amp Modeler (NAM)	LV2 plugin. Loads `.nam` files	AI captures of real tube amps. Architecture 2 (A2) released in June 2026 offers higher accuracy with 30–40% less CPU. Models: TONE3000.
Proteus	LV2 plugin. Neural network modeling (LSTM)	By GuitarML. Faster preset switching than NAM.
Kapitonov Plugins Pack (KPP)	Profile-based traditional amp modeling	Excellent for classic rock/metal. Available in LV2 and VST3.
Guitarix	All-in-one virtual amp + pedals	Standalone or LV2. Includes native modules for loading `.nam` and RTNeural models.

Note: CRITICAL for KPP: The input level at the beginning of the Kapitonov Plugins Pack chain must be strictly around -20 dB, otherwise the plugins will distort incorrectly. Use a meter plugin (e.g., LSP Meter) to verify.

⚠︎

Warning: Neural amps (NAM, Proteus, KPP) only model preamp/poweramp. You must load a Cabinet IR (via LSP IR Loader or similar) to get a usable guitar tone. Without an IR, the sound will be thin and unpleasant.

Modular hosts

Software	Purpose
Carla	Modular plugin host. Chain plugins visually: Input → Tuner → NAM → IR Loader → Reverb → Output. Hosts Windows VSTs via yabridge.
qpwgraph	Visual patchbay for PipeWire/JACK. Manually connect hardware inputs to software hosts (PipeWire does not auto-connect).

Configuration and first launch

Pro audio profile

To achieve minimal latency, you must bypass standard software mixing:

Open pavucontrol.
Go to the Configuration tab.
Set your interface profile to Pro Audio.

If the "Pro Audio" profile is missing, ensure pipewire-alsa is installed and restart PipeWire. This profile disables software mixing and enables hardware-exclusive mode, critical for the lowest latency.

Latency verification

Always perform a physical loopback test to measure the real Round-trip Latency (RTL).

Connect a cable from your interface Output back into the Input.
Launch LSP Latency Meter:

# Option A: Via Carla (recommended for beginners)
carla  # Add plugin "LSP Latency Meter Stereo", connect wires

# Option B: Via jalv (terminal)
jalv http://lsp-plug.in/plugins/lv2/latency_meter_stereo

Play a sharp transient (string scratch) and read the Round-trip Latency (RTL) value.

Target values:

< 5 ms: Excellent
5–10 ms: Acceptable for practice
> 12 ms: Noticeable "lag", difficult to play in time

Typical processing chain

For a standard metal/rock tone, route your signal in carla or your DAW as follows: Hardware Input → Noise Gate (e.g., LSP Gate) → NAM (Load A2-Full model) → LSP IR Loader (Load Cabinet Impulse Response) → Dragonfly Reverb → Hardware Output.

Windows VST via Wine

Yabridge

Yabridge (v5.1.1+) bridges Windows VST2/VST3/CLAP plugins to Linux via Wine. It is essential for commercial plugins (Neural DSP, STL Tones, Amplitube).

# After installing Windows plugins via Wine:
yabridgectl sync  # Required to register plugins with Linux hosts

JUCE 8 black screen fix

Note: A widespread issue in 2026 affects JUCE 8-based plugins (e.g., Serum 2, Nexus 5) running via Wine/yabridge: the plugin GUI is a black window. This is because stock Wine lacks the Direct2D/DirectComposition render path required by JUCE 8.

To fix this, you must use patched Wine builds. The giang17/wine-d2d1-dcomp project provides prebuilt binaries and a guide for Arch/CachyOS.

PipeASIO for Proton/Steam

For Windows DAWs (FL Studio, Ableton) or games (Rocksmith) running via Proton, PipeASIO (v1.7.0, Sept 2026) connects ASIO directly to PipeWire, bypassing the missing libjack.so.0 in the Steam Runtime container.

Note: If using FL Studio via Wine/Proton, you must turn off "Mix in buffer switch" in Audio settings to prevent constant xruns.

Rocksmith 2014

Rocksmith 2014 runs on NixOS via Proton. The recommended method uses the nixos-rocksmith flake, which patches Steam to preload libjack.so and use RS_ASIO with WineASIO. For visual patching, crosspipe is recommended as a modern alternative to helvum.

programs.steam = {
  enable = true;
  rocksmithPatch.enable = true;
};

Steam Launch Options:

LD_PRELOAD=/run/current-system/sw/lib/libjack.so PIPEWIRE_LATENCY=128/48000 %command%

Note: Rocksmith strictly requires a sample rate of 48000 Hz.

Troubleshooting

Symptom	Cause & Solution
Xruns (audio glitches)	Ensure `powerManagement.cpuFreqGovernor = "performance"` is active. Check `pw-top` for high-CPU nodes. Disable Wi-Fi: find driver name via `lspci -k` or `lshw -class network`, then run `rfkill block wifi` to prevent interrupt storms.
Extreme latency stutters	As a last resort, add `processor.max_cstate=1` to `boot.kernelParams`. Warning: This disables CPU sleep states, resulting in extreme power draw and heat. Use with caution.
Input clipping / digital distortion	High-output pickups are overloading the interface's Hi-Z preamp (low dBu). Use a passive DI-box, an inline pad, or lower your guitar's pickup height.
No sound	Check `qpwgraph` — PipeWire does not auto-connect hardware. Verify Pro Audio profile in `pavucontrol`. Run `sudo lsof /dev/snd/*` to find conflicting processes.
DAW cannot find plugins	Ensure `environment.variables` block is applied. Log out/in after rebuild. Verify paths: `echo $LV2_PATH`.
Audio pops a few seconds after playback stops	WirePlumber suspends the ALSA node after 5 seconds of inactivity. Ensure `session.suspend-timeout-seconds = 0` is set in `wireplumber.extraConfig`.
JUCE 8 VST shows black screen	Stock Wine lacks Direct2D support. Install `wine-d2d1-dcomp` patches by giang17 and route the specific plugin to this patched Wine version using yabridge's dispatcher trick.
PipeWire config not applying	Restart user services after rebuild: `systemctl --user restart pipewire wireplumber`. Check for WirePlumber overrides: `wpctl status`.