Capture Types

Not all captures represent the same portion of an audio signal chain.

A model may represent a single pedal, an amplifier without a speaker cabinet, an amplifier together with a cabinet and microphone, or an entire chain of equipment.

Understanding what is contained in a capture is essential. It determines how the model should be used, what additional processing may be required, and whether two models can be meaningfully compared.

Terminology varies between capture platforms and communities, so the most useful description of a capture is often a clear statement of what equipment was included in the capture signal path.

Direct amplifier captures

A direct amplifier capture represents an amplifier without the acoustic contribution of a physical loudspeaker cabinet and microphone.

A typical signal path is:

Capture signal → amplifier → suitable load/direct capture device → capture system

The resulting model can then be used with:

A cabinet impulse response (IR)
A modeled cabinet
A physical guitar cabinet with an appropriate power-amplification system
Other compatible speaker/cabinet processing

Direct captures are useful because the amplifier and cabinet portions of the signal chain remain separate.

This allows the same amplifier capture to be paired with different cabinets, speakers, microphones, or IRs.

A speaker-level amplifier output must not be connected directly to a normal audio-interface input unless the equipment is specifically designed to accept that signal.

See Cabinets and IRs.

Amplifier and cabinet captures

A capture can include the amplifier and the response of a loudspeaker cabinet.

A common microphone-based signal path is:

Capture signal → amplifier → loudspeaker cabinet → microphone → microphone preamp/interface → capture system

In this case, the resulting model may represent the combined behavior of:

Amplifier
Loudspeaker
Cabinet
Microphone
Microphone position
Microphone preamp
Other equipment in the return path

Such a capture normally does not require an additional cabinet IR during playback unless another cabinet response is intentionally being added.

Adding a conventional cabinet simulation to a capture that already contains a cabinet and microphone response can produce an unintended "double cabinet" effect.

Pedal captures

Many nonlinear pedals can be captured.

Examples include:

Overdrive
Distortion
Fuzz
Boost
Preamp pedals
Some analog processors

A typical chain is:

Capture signal → pedal → capture system

or:

Capture signal → reamp/capture device → pedal → capture system

The resulting model represents the pedal at the settings used during capture.

A pedal capture can then be placed before an amplifier model or another compatible part of a virtual signal chain.

Pedal and amplifier captures

A pedal and amplifier can be captured together:

Capture signal → pedal → amplifier → direct return

or, when a physical cabinet and microphone are included:

Capture signal → pedal → amplifier → cabinet → microphone → capture system

This can reproduce a particular combination very effectively because the interaction between the devices is included in the measured system.

The tradeoff is flexibility.

If the pedal and amplifier are captured together, they cannot normally be separated afterward. Changing the virtual amplifier while retaining only the captured pedal is not equivalent to having captured the pedal separately.

Preamp captures

Preamps and preamp stages can also be capture targets.

Examples may include:

Guitar amplifier preamps
Rack preamps
Pedal-format preamps
Studio preamplifiers
Other nonlinear line-level equipment

Whether a particular device can be modeled accurately depends on the capabilities and limitations of the capture technology.

A preamp capture may require additional processing or amplification during playback depending on its intended use.

Complete signal-chain captures

Multiple devices can be captured as one system.

For example:

Pedal → preamp → amplifier → cabinet → microphone → microphone preamp

The resulting model represents the combined behavior of everything included in the measured path.

This approach can be useful when the objective is to reproduce a specific finished sound rather than provide maximum flexibility.

It can also preserve interactions between devices that might not be reproduced identically by combining independently captured models.

The disadvantage is that the individual components cannot normally be adjusted, removed, or rearranged after capture.

Captures with microphones

When a microphone is part of the return path, its characteristics become part of the resulting measurement.

This includes:

Microphone model
Polar pattern
Position
Distance
Angle
Proximity effect
Microphone preamp
Room contribution where significant

A small change in microphone position can produce a substantial change in the resulting sound.

Therefore, microphone information is valuable metadata for any capture containing a physical cabinet.

Captures without microphones

Direct captures avoid the microphone and acoustic cabinet path.

They can provide greater flexibility because cabinet and microphone characteristics can be selected later using an IR or cabinet-modeling system.

This can also make direct captures particularly useful for comparison and experimentation.

However, the playback chain must then supply whatever cabinet/speaker behavior is required for the intended sound.

Full-rig captures

The term full rig is sometimes used for a capture containing most or all of a finished guitar signal chain.

Depending on the platform and user, this might include:

Pedals
Amplifier
Cabinet
Microphone
Microphone preamp

Because terminology varies, a label such as "full rig" should not replace actual documentation of what the capture contains.

When sharing a capture, list the components explicitly whenever possible.

Static settings and multiple captures

Most capture technologies reproduce the behavior of equipment around the configuration used during capture.

For example, an amplifier captured with:

Gain at 4
Bass at 5
Middle at 6
Treble at 5
Presence at 4

does not automatically become a complete digital implementation of that amplifier's control circuitry.

Playback software may provide controls that modify the resulting model, but those controls are not necessarily equivalent to turning the corresponding controls on the original device.

For substantially different settings, multiple captures may be appropriate.

A collection might therefore include:

Clean
Edge of breakup
Crunch
High gain
Lead

or several captures made at documented control settings.

Linear and nonlinear elements

Capture systems are particularly useful for modeling nonlinear behavior such as distortion, saturation, compression, and level-dependent response.

Some portions of an audio chain, particularly loudspeaker cabinet and microphone responses, can also be represented using linear techniques such as impulse responses.

This creates several possible workflows.

For example:

Captured amplifier + separate cabinet IR

provides more flexibility than:

Captured amplifier + cabinet + microphone

while the latter may conveniently reproduce a specific complete sound.

Neither approach is inherently superior. They serve different purposes.

What a capture does not necessarily contain

Do not infer the contents of a capture solely from its filename.

For example, a model named after an amplifier might contain:

Amplifier only
Amplifier and cabinet
Amplifier, cabinet, and microphone
Pedal and amplifier
An entire signal chain

Likewise, the word "direct" may be used differently by different creators and platforms.

When the information is available, consult the capture's metadata or creator documentation.

Choosing a capture type

The appropriate capture type depends on the intended use.

Choose a direct amplifier capture when you want to experiment with different cabinets, IRs, or playback systems.

Choose an amplifier/cabinet capture when you want a particular miked cabinet sound already included.

Choose a pedal capture when you want to combine that pedal behavior with different amplifier models.

Choose a combined or full-chain capture when reproducing a particular complete signal chain is more important than independently changing its components.

There is no universally best capture type.

The important question is:

What part of the original signal chain do you want the model to reproduce?

Documenting capture type

When sharing captures, state clearly what they contain.

Useful information includes:

Capture type
Devices included
Devices deliberately excluded
Whether a cabinet is included
Whether a microphone is included
Cabinet and speaker
Microphone and position
Pedal settings
Amplifier settings
Capture method
Calibration information

Clear documentation prevents incorrect playback configurations and makes captures more useful to other people.