Overview Connections Calibration Settings Traces

Overview

Audiospex generates a test signal which is connected to the input of the device to be analysed. This could be a compressor, gate, or something more interesting like a speaker or microphone under load exhibiting non-linear behavior. The test signal is a sine wave that steadily increases in amplitude. Parameters of the test signal are discussed in the SETTINGS section.

The device output is then sent back to Audiospex which analyses and displays the results in real time. Repeated tests are overlayed on the same graph, allowing you to compare different settings and modes to your device. Completed traces can be printed, saved, restored or deleted.

Note that Audiospex requires a pure signal path to run so ensure no other audio applications are running or generating audio which could contaminate results.

Connections

Audiospex can use any audio interface connected to your machine capable of simultaneous input and output. Use the best quality device you have and ensure it is set to 24 bit mode if available. This can be done using the AMS (Audio MIDI Setup) utility. Sample rate can be set within Audiospex.

Once your connections have been made between your audio interface and the device to test click on the DEVICES icon. Here you can choose the relevant input and output device. If required the sample rate can be set - higher is always better!

The hardware gain setting is displayed for the selected device, which is set using the AMS utility. This should read 1.0, like in the example shown here. If not adjust it with AMS to full to obtain the best analysis resolution.

Currently Audiospex only operates in mono so only uses the first/left channel of your audio interface. If you wish to test a stereo device connect the left channel, run a test then connect to the right channel and run another test. The results will be overlayed together on the graph.

Calibration

The next step is to ensure that levels are correct between Audiospex and the device under test and allow you to set input/output level controls that may be on your device. You can of course skip this step if you want to get started quickly or have nothing in the signal path that requires calibration. The calibration facility can be performed at any time.

To start calibration click the CALIBRATE icon.

Audiospex does calibration by generating a steady test tone and provides a level meter to display the signal level at the current input. The amplitude level and frequency of the test tone can be set. The calibration can be carried out in three following ways:

Manual mode - calibrate the device under test

Set your test tone level and frequency then click the start button within the manual pane. Audiospex will then generate the test tone and show the level received back from your device. Adjust levels on your device until the input level matches the output level set. Note ideally the test level used should be in the linear region of the device under test - eg for compressors use a low test level below the compression threshold; for gates use a high level that is above the gate threshold.

Manual mode - calibrate Audiospex internally

Similar to above but use the output and input trim controls of the calibrate panel to adjust Audiospex internal gain. If the meter level is too high reduce the output trim; if the meter level is too low raise the input trim.

Automatic mode - calibrate Audiospex internally

Automatic mode performs the process above for you. Click on the AUTOMATIC tab then either TRIM OUTPUT/INPUT as appropriate.

Settings

Click on the SETTINGS button to alter the parameters of the test signal generated by Audiospex.

Audiospex works by generating a steady tone, testing the output of the device for a time period set by STEP TIME then increasing the amplitude of the test tone by the amount set in GAIN INCREMENTS. The settings are a trade between how long the trace takes to complete and the resolution of the final graph. The total time for a trace to complete is shown by TRACE TIME

Start/stop gain

Defines the amplitude levels the trace will start and stop at. These allow you to adjust the range to cover only levels of interest, which will result in a faster trace time.

Gain increments

Controls the level of detail of the final trace. Smaller increments provide more reading and more detail at the expense of longer trace times.

Step time

Controls the time Audiospex spends analysing the current amplitude level before moving to the next. Devices like compressors and gates have a finite attack time so for these devices the step time should be at least twice that of the attack time, to get a true representation of the device under static conditions. Longer step times reduce the influence of device attack times at the expense of longer trace times.

Frequency

Allows you to test your device with different frequncy test tones.

Traces

To start a trace click the START icon; to stop a running trace click the STOP icon. If the start icon is not available either a trace or calibration is already running or there is a problem with your device settings, which can be addressed in the DEVICES panel.

When started traces appear as a name and colour code in the Trace List Panel. Click a trace in the list to select, which highlights the trace in the list and the graph. Selected traces can be deleted if no longer required with the backspace key or by using the delete option within the TRACE menu. Double clicking a trace within the trace list allows you to name the trace.

The trace list is by default anchored to the main graph; moving the main window results in the trace list following. If this behavior is not required uncheck the TRACE LIST FOLLOWS MAIN WINDOW option in the WINDOW menu.

Traces can be saved, loaded and printed from the FILE menu.