NAM Calibration Guide

The Basics

What Calibration Does

A NAM capture learns how a piece of gear reacts to the exact signal level it was fed during training. Your audio interface converts your guitar to digital at its own level, and every interface is different. Calibration tells the TONE3000 Plugin your interface's level so the capture gets hit the same way the creator hit the real gear.

This guide is for playing captures through your own audio interface, for example with the TONE3000 Plugin in your DAW. If you run NAM on partner hardware like the Darkglass Anagram or HeadRush units, the device's input level is already known and the manufacturer handles calibration for you. Nothing to set.

It's optional. Captures sound great without it, and the block's In knob is right there if you want more or less gain. It's music: use your ears and turn knobs to taste. If you want a capture to respond exactly the way the creator set it up, read on. It takes a couple of minutes.

Why Bother?

Interfaces differ by a lot. A Focusrite Scarlett's instrument input clips at +12 dBu, a MOTU M2 at +16 dBu, an Antelope Zen Go at +20 dBu. Same guitar, same gain knob at minimum, up to 8 dB difference in how hard the capture gets hit. Eight dB is roughly the gap between a vintage single coil and a hot humbucker, so without calibration the same capture can play noticeably cleaner or dirtier than the creator intended.

With Calibration on, the plugin reads the level stored in each capture, compares it to yours, and adjusts the input automatically. Set it once and every calibrated capture, from any creator, lands at the right level.

Quick Start

1. Plug into the instrument input (Hi-Z / Inst / Guitar) and set the Inst switch if there is one.
2. Turn the input gain all the way down. It's the only knob position the manufacturer's spec applies to.
3. Find your interface's number. Check Known Levels for Popular Interfaces or your manual: the instrument input's "Maximum Input Level (at minimum gain)".
4. Enter it in the plugin. Go to Settings → Plugin Settings, turn on Calibration, and type the dBu value.
5. Play. Captures with calibration data show a gauge icon on their block and are compensated automatically. Use the Calibrated filter in the tone browser to find them.

Tip: Calibration is remembered on this computer, so every new plugin instance starts calibrated.

Key Terms

Calibrate Your Interface

Find Your Interface's Input Level

In your interface's spec sheet, find the instrument (Hi-Z / DI / Guitar) input and look for "Maximum Input Level (at minimum gain)", "Max Input Level", or wording like "Lineup: 12 dBu = 0 dBFS". That number is your calibration value.

• Use the instrument input's figure, not the mic or line input's.
• If it's quoted in dBV, add 2.2 to get dBu. +9 dBV = +11.2 dBu.
• If the input has a pad, the figure changes with it. Use the number for the pad position you play with.

Known Levels for Popular Interfaces

Instrument input with the gain at minimum, from manufacturer spec sheets unless marked (community). Specs change between revisions, so check your own manual if in doubt.

Keep the Gain at Minimum

Calibration assumes the gain knob is at minimum. Every dB you add lowers your clipping level by a dB, and gain knobs aren't marked in dB, so the simplest accurate setup is to leave it at minimum. Modern instrument inputs have plenty of headroom and low noise there.

If you really need more gain, measure what you added: play any steady signal into the input at minimum gain and note the peak dBFS in your DAW. Turn the gain up to where you want it and note the new peak. The difference is the gain you added. Subtract it from your interface's number, enter that, and don't move the knob again.

Tip: If hot active pickups or a boost pedal clip the input even at minimum gain, engage the pad (and use the pad figure) or back off the guitar's volume.

No Spec? Measure It

If your interface doesn't publish a figure, you can measure it with a multimeter in about five minutes using the same method creators use. Follow Step 2 to measure one of your interface's outputs, then Step 3 with that output plugged into your instrument input. The result is your calibration value.

Set It in the TONE3000 Plugin

1. Open Settings → Plugin Settings.
2. Turn on Calibration and enter your interface's dBu value.
3. Load any capture with the gauge icon. The plugin compensates it automatically.

To find captures that include calibration data, open Filters in the tone browser (in the plugin or on TONE3000) and turn on Calibrated.

Reach for the block's In knob when you want more or less gain than the real thing. Calibration gives you the creator's starting point; the knob is still yours.

Stacking captures. When a creator also saved a return level, the plugin uses it to pass a true output level from that block to the next NAM block, so a pedal capture drives an amp capture as hard as the real pedal did. There's nothing to set up: it happens automatically with Calibration on, and Normalize may show as overridden on that block. That's intentional.

For Capture Creators

What You're Measuring

Two numbers, saved into the .nam file and shown on TONE3000 with the Calibrated tag:

• Send level (input_level_dbu): the analog level, in dBu, that your DAW's 0 dBFS produced at the gear's input. This is the one that matters. It lets every player hit your capture at the level you did.
• Return level (output_level_dbu): the analog level, in dBu, that produced 0 dBFS at the interface input recording the gear. Optional. It lets the plugin gain-stage your capture into the next block when players stack it.

Measure the return level only for gear with a line or instrument-level output that the plugin can hand to another block: pedals, preamps, amp heads through a load box or DI, rack and outboard gear. For a mic'd amp and cab it's rarely worth it: the level reflects your mic and preamp gain rather than the amp, and it only matters if a player stacks your capture into another NAM block.

Both numbers describe your rig at the moment you recorded, so measure with exactly the levels you record with. Before or after the capture doesn't matter, as long as nothing changes in between.

What You Need

• A multimeter that reads AC volts (see below)
• A test tone. Download the 1 kHz tone or the 100 Hz tone (both 0 dBFS, loop seamlessly), drop it on a track and loop it. Or use your DAW's tone generator at 0 dBFS.
• Your normal reamp chain: interface, reamp box, and the cables you use to hit the gear you're capturing

Choosing a multimeter

Any digital multimeter with an AC volts setting works. Audio levels are a few volts and safe to probe. The one spec that matters is AC frequency range: many budget meters are only accurate from 40 to 400 Hz and read low at 1 kHz. If your meter isn't rated to 1 kHz, measure with the 100 Hz tone instead. The voltage is identical; the meter just reads it correctly. "True RMS" isn't required for a sine wave.

Prices are approximate and vary by region.

Tip: Not sure about your meter? Measure the same output with both tones. If 1 kHz reads lower than 100 Hz, use the 100 Hz reading.

Step 1: Set Your Levels and Leave Them

Set up your reamp chain as usual: interface output → reamp box → gear → load box, DI, or mic → interface input.

Pro tip: hit the gear hot. A capture only learns the levels it's fed, and calibration tells the plugin how hot you went, so there's no downside. Passive reamp box: trim all the way up. Active reamp box: as hot as it goes without clipping the box; the gear itself is allowed to clip. Reference: a hot humbucker peaks around 2 V (+5 dBu), an EMG 81 about 4.5 V (+12 dBu). Aim there or higher.

Set the return gain so the recording peaks comfortably below 0 dBFS, and from here on don't touch any hardware level. If you do, re-measure.

Step 2: Measure the Send Level

1. Loop the 1 kHz tone at 0 dBFS on a track routed to the output you reamp from. Track and master faders at 0 dB, no limiter.
2. Unplug the cable from the gear's input (the end that goes into the amp or pedal, after the reamp box if you use one).
3. Set the meter to AC volts (V~, not mV). Touch the red probe to the tip of the plug and the black probe to the long sleeve, and let the reading settle. Alligator-clip leads make this easier.
4. Convert volts to dBu with the calculator below. That's your send level.

Note: Expect 1 to 10 V (+2 to +22 dBu). Millivolts means the tone isn't at 0 dBFS, the output is turned down, or the meter is on mV. Zero means you're not touching tip and sleeve.

Step 3: Measure the Return Level (Optional)

Only for DI captures: pedals, preamps, amp heads through a load box or DI, rack and outboard gear, where the gear's output goes straight into your interface. For a mic'd amp and cab it's rarely worth it: the level reflects your mic and preamp gain rather than the amp, and it only matters if a player stacks your capture into another NAM block, such as an outboard compressor capture.

1. Plug the output you just measured straight into the interface input that records the gear, bypassing the gear. Don't touch any gain knob.
2. Play the tone. It will probably clip the input. Lower the tone track's fader until the input peaks just under 0 dBFS. Note how far you lowered it and the input's peak reading.
3. Enter the three numbers below.

Shortcut: If the return input's gain is at minimum, use its maximum input level from the spec sheet instead of measuring: the line input figure if you record into a line input, or the instrument figure from the interface table if you record into an instrument input.

Step 4: Enter the Values on TONE3000

When you capture your gear, open Advanced under Training Settings.

Enter Send Level (dBu) and Return Level (dBu) under Calibration and save. TONE3000 writes them into the .nam file and tags your tone Calibrated.

Already uploaded? Open the tone, open the model's menu, expand Calibration, and enter the levels. TONE3000 updates the stored .nam file for you. Either way, the model shows a gauge icon and a cal. label on its tone page.

Creator Checklist

• Levels set, then hands off the hardware
• 1 kHz (or 100 Hz) tone at 0 dBFS, cable unplugged from the gear, meter on AC volts, tip to sleeve
• Volts to dBu = send level
• Loop send into return and calculate the return level (pedals, preamps, DI'd heads, outboard only)
• Enter both under Advanced → Calibration on TONE3000

Reference

Calculators

The three calculators from this guide in one place.

Volts to dBu Conversion

dBu = 20 × log10(V ÷ 0.775). Going the other way, V = 0.775 × 10^(dBu ÷ 20). If a spec is in dBV, add 2.2 to get dBu.

FAQ

Learn More

Related Guides

• TONE3000 Plugin, including the Calibration and Gain Staging settings
• Neural Amp Modeler, the basics of NAM captures
• Capture Your Gear: Sweep Method and Dry/Wet Method

Need Help?

Join the TONE3000 Discord, the Neural Amp Modeler Facebook Group, or the Neural Amp Modeler subreddit. Chances are someone has measured your exact interface.

For anything else, email support@tone3000.com.

Thanks for being a part of the TONE3000 community.