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Reference
Reference

Troubleshooting

Find your symptom, work down the causes in order. Every fix cites where it came from — and where Neural DSP has acknowledged a bug rather than a user error, that's said plainly.

As far as we could find, no dedicated troubleshooting reference for this device existed anywhere — every known issue lived in a separate forum thread. This is an attempt at the missing page.

Read before capturing

The four that destroy hardware

Everything else on this page is about sounding bad. These are about damage.

Can damage gear

Never connect a tube amp's speaker output directly to the Nano Cortex. Neural DSP states this can cause serious damage to both devices. Capturing an amp head requires a reactive load box — a Two Notes Torpedo Captor, Suhr Reactive Load IR, Fryette Power Station, Universal Audio OX or Radial Headload.

Creating Neural Captures on Nano Cortex
Can damage gear

If you capture through an amp's own DI output instead, keep a speaker cabinet connected to the amp. Running a tube amp with no load damages it.

Creating Neural Captures on Nano Cortex
Can damage gear

A ToneX Z-Tone is a DI box, not a load box. It will not protect your amp.

Forum: simulating an FX loop
Can damage gear

When capturing a preamp via an FX Send, do not also patch back into the FX Return — that creates a feedback loop.

Creating Neural Captures on Nano Cortex · Forum: simulating an FX loop
Tone

It sounds muffled, boxed-in or dark

Usually the very first complaint after downloading captures from the cloud.

  1. Check first

    Double cab. The capture already contains a mic'd cabinet, and the IR Loader is stacking a second speaker on top of it.

    Turn the IR Loader off — turn Footswitch II past the last slot until no indicators are lit. Amp-and-cab captures have the cabinet permanently baked in and it cannot be separated.

    Forum: amp + cab captures · Forum: turn off cab sim
  2. Also common

    The IR's high-cut is set very low, or the mic position is dark.

    Move the mic position further from the centre of the cone and raise the high-cut. Mic and position selection only works on the factory IRs, not on your own uploads.

    Nano Cortex User Manual 2.2.0 · Nano Cortex FAQ
Learn the cab sim rule

It sounds raspy, buzzy or fizzy

The exact inverse of the boxed-in problem.

  1. Check first

    No cab at all. The capture is amp-only and the IR Loader is bypassed, so you're hearing a raw amp with no speaker in the way.

    Turn the IR Loader on and pick a cab. The community's own diagnostic is worth memorising: if the IR is off and it sounds bad, the capture probably has no cab; if the IR is on and it sounds bad, the capture probably includes one.

    Forum: amp + cab captures
  2. Also common

    Digital fizz in the top end, common to all modelling.

    High-cut around 8–10 kHz on the IR, and low-cut 80–100 Hz to tighten the bottom. Also try less gain than feels right.

    Forum: lush clean presets
Learn the cab sim rule
Volume and levels

My presets are all at different volumes

Or: “the volume I set won't save”. One of the highest-recurrence complaints.

  1. Check first

    You're using the LEVEL knob, which is a global master rather than a per-preset level.

    Hold CAPTURE for two seconds to open the Capture Volume view, then use LEVEL there. Range is −24 dB to +12 dB, default 0.0. Save before moving on.

    Nano Cortex User Manual 2.2.0 · Forum: volume levels not saving between presets
  2. Also common

    Cloud captures are gain-staged inconsistently by whoever uploaded them, and perceived loudness tracks spectral density rather than dB — so a clean and a high-gain capture can measure the same and sound nothing alike.

    Level-match by ear at playing volume against a factory preset as your reference. The 25 factory captures are curated and consistent; the cloud is not.

    Forum: volume levels not saving between presets · MusicRadar review
  3. Less common

    IR level differs between presets.

    IR level is per-preset and doesn't affect other presets using the same IR, so it's a safe second lever.

    Forum: volume levels not saving between presets
Level-match all four presets

The quarter-inch outputs sound quieter and duller than headphones

  1. Check first

    You're using TS instrument cables on balanced TRS outputs, which costs about 6 dB and some clarity.

    Use TRS cables, or TRS-to-XLR. An entire forum thread about the device's audio quality resolved to exactly this.

    Forum: audio quality (balanced vs unbalanced) · Andertons spec sheet
  2. Also common

    Only one output is connected, so panned content is missing.

    Enable analog output auto-sum, added in NanOS 2.2.0, so a single cable receives a proper mono sum.

    NanOS 2.2.0 release notes
See the output specs
Noise and hum

There's hum, buzz or hiss

Especially when it's connected to anything else.

  1. Check first

    Powering over USB-C while running unbalanced cables to other gear, which creates a ground loop. This is the documented number-one cause.

    Power from the DC jack with a regulated supply, or switch to balanced TRS runs — ideally both.

    Nano Cortex power sources
  2. Also common

    Ground loop through the outputs.

    Engage the GND ground-lift switch. Full fix for some, partial for others.

    Nano Cortex User Manual 2.2.0 · Forum: background noise
  3. Also common

    An undersized power supply. The device needs 600 mA minimum, and 500 mA supplies are below spec.

    Use 9–12 V DC, 600 mA or more, centre-negative, 2.1/5.5 mm. The Quad Cortex supply works. Owners confirm the Truetone 1SPOT, Boss PSB-1U and Cioks DC7.

    Nano Cortex power sources · Forum: power supply for the Nano Cortex
  4. Less common

    The capture or IR itself is noisy — plenty of cloud content is.

    Use the Input Gate in the Capture Volume view, and try a different capture to confirm.

    Forum: background noise · MusicRadar review
Power and grounding in full
Controls not responding

The footswitches feel laggy

  1. Check first

    They fire on release rather than on press — deliberately, so that press-and-hold can address the tuner and tap tempo on the same two switches.

    There is no setting to change this and no workaround. Worth knowing it's by design, not a fault. It does genuinely hurt accuracy when starting a looper.

    Forum: the “delayed” footswitch
Every control behavior

It won't turn on

  1. Check first

    A bug in NanOS 2.2.0 could prevent booting when an expression or MIDI pedal is connected. NanOS 2.2.1 exists specifically to fix it.

    Unplug the expression or MIDI pedal to boot, then update to 2.2.1 or later.

    NanOS 2.2.1 release notes
  2. Also common

    Power. USB-A cannot run this device, and undersized supplies cause intermittent failures.

    Use 9–12 V DC at 600 mA or more, or a genuinely USB-C-compliant 5 V / 1.5 A source. Data works over USB-A but power does not.

    Nano Cortex power sources
Firmware timeline
Playing live

There's an audible gap when I change preset

  1. Check first

    Around 60 ms of silence, introduced deliberately in NanOS 2.0.0 to allow the flexible signal chain. Delay and reverb trails do continue across the change.

    Keep the modulation, delay and reverb identical across all four presets — several owners report this makes it inaudible. Better still, switch effects via expression pedal or MIDI CC, which isn't a preset change and so has no gap.

    Nano Cortex FAQ · Forum: sound cut when switching preset
Live switching strategies

I can only reach four presets with my feet

  1. Check first

    By design. There are 64 presets but only two footswitches, giving IA/IB and IIA/IIB. The BANK button moves through capture banks, not preset banks, and it's hand-operated.

    Add a MIDI foot controller over TRS MIDI Type A — presets map automatically to Program Change 0–63. Neural DSP staff have endorsed the Nektar Pacer, Morningstar MC6, Behringer FCB1010, Harley Benton MP-100 and Fortin Hydra. Otherwise, build a setlist around four combined sounds.

    Using MIDI on Nano Cortex · Forum: just 4 presets on a live show?
Reach all 64 with MIDI

The cab block keeps switching itself off mid-rehearsal

  1. Check first

    A confirmed bug with MIDI over the TRS port: the controller sends CCs that the cab and capture blocks mishandle. Neural DSP support has acknowledged it as a known issue with a fix planned and no date.

    Drive MIDI over USB-C instead, which costs you the audio-interface use of that port. There is no other workaround.

    Forum: CAB/IR block randomly switching off
The confirmed TRS MIDI bug
Capturing

The capture fails with a level error

“Detected level signal was too high”, even when calibration looked green.

  1. Check first

    There's a separate sanity check during the capture itself, stricter than the calibration meter. Green LEDs during calibration do not guarantee the capture will pass.

    Lower the source device's output rather than the Nano's gain, and drop capture gain significantly even if the meter then reads blue. One owner needed four attempts. Solid-state gear triggers this more readily than tube amps.

    Forum: capture error / level too high
  2. Also common

    BOOST engaged with GAIN already up.

    Set GAIN to minimum before engaging the +26 dB BOOST. Neural DSP repeats this warning in three separate documents.

    Creating Neural Captures on Nano Cortex
Capture craft, not just procedure

My capture doesn't sound like the real thing

  1. Check first

    The IR Loader was engaged while capturing, baking a second cab in.

    Turn the IR off before capturing, and A/B with Footswitch I as you go.

    Creating Neural Captures on Nano Cortex · Forum: amp + cab captures
  2. Also common

    Capture level was too low, which repeatedly shows up as captures with less gain than the source.

    Recalibrate for a solid green reading, and expect to take several attempts.

    Forum: capture error / level too high · Premier Guitar review
  3. Less common

    You're capturing a software amp sim. Multiple owners report captures of plugins missing distortion and sounding wrong, while pedal captures work fine for the same people.

    No resolution has been published for this. Treat plugin capturing as unreliable on this device.

    Forum: capture error / level too high
Capture craft, not just procedure
App and connectivity

I can't play backing tracks over Bluetooth

  1. Check first

    Bluetooth on this device is for pairing with the Cortex Cloud app only. There is no Bluetooth audio and no wireless headphone support.

    Send audio over USB-C from a phone, tablet or laptop — iOS works well, Android is reported to crackle and isn't supported. Alternatively use an FRFR with its own Bluetooth or aux, or a small mixer.

    Nano Cortex FAQ · Forum: backing tracks, how to
Backing tracks, properly

The app won't connect over Bluetooth

  1. Check first

    The unit isn't in pairing mode.

    Hold EXIT and CAPTURE together for one second. The GAIN ring sweeps clockwise and the Footswitch I LED blinks slowly. Then choose Add New in the app.

    Nano Cortex Quick Start Guide · Bluetooth pairing guide
  2. Also common

    On Android, the app lacks Location permission, which BLE scanning requires.

    Grant Location permission to the Cortex Cloud app.

    Forum: pairing problems
  3. Also common

    Stale Bluetooth state.

    Power-cycle the pedal and restart the phone. No firmware fix has been announced.

    Forum: pairing problems
The full app workflow

I want to put my own pedals in the loop

  1. Check first

    There is no effects loop on this device.

    Either capture the external preamp and load it into the capture slot, or save a preset with no capture active and run your real pedal in front, using the Nano only for cab, delay and reverb. Never route a speaker-level signal back into it.

    Nano Cortex FAQ · Forum: simulating an FX loop
The fixed signal chain

My Quad Cortex presets won't load

  1. Check first

    Presets are incompatible — the Nano's fixed chain can't represent Quad Cortex routing.

    Captures, however, are fully interchangeable and officially the same resolution. Since November 2025 over a thousand Quad Cortex factory captures are available to Nano owners, and NanOS 2.2.0 added a Capture V2 player. Note the Nano can play V2 captures but cannot create them.

    Nano Cortex FAQ · NanOS 2.2.0 release notes
Installing captures properly
Recording

My DI track is very quiet in the DAW

  1. Check first

    There is no input gain control on the device, and the operating system's input level for it defaults low.

    Raise the input volume in your OS sound settings for the Nano Cortex before opening your DAW. On macOS that's System Settings → Sound → Input.

    Forum: DI volume low in interface mode
Recording and reamping

Audio stutters or drops out over USB

  1. Check first

    Connected through a USB hub.

    Connect directly to a motherboard port. Neural DSP explicitly discourages hubs.

    Using Nano Cortex as an audio interface
  2. Also common

    Powered from USB and an external supply simultaneously.

    Use one power source. One owner's glitching vanished when they removed the second.

    Nano Cortex power sources
  3. Also common

    Session sample rate isn't 48 kHz.

    The device is fixed at 24-bit / 48 kHz. Set your session to match rather than resampling.

    Using Nano Cortex as an audio interface
Recording and reamping
How to read the labels
Official
From Neural DSP's manual, FAQ, guides or release notes.
Community
Reported by owners. Corroboration, not a primary spec.
Our reading
Our interpretation, not something Neural DSP states.
Unverified
We could not confirm this, or sources disagree.

20 symptoms documented. If you own one of these and something here is wrong or incomplete, it should be fixed — the point of this page is to stay true as firmware moves.