The SSA features a color touchscreen that provides real-time views of your audio signal. This article explains what each screen shows and how to navigate between them.
Oscilloscope View
The oscilloscope screen shows a 2x2 grid with a live waveform for each connected channel. This is the same type of display you would see on a bench oscilloscope: it shows the shape of your audio signal over time.
What you see on each channel panel:
- Waveform: The audio signal drawn as a continuous line. A clean sine wave appears as a smooth curve. Clipping shows up as flat tops and bottoms where the signal is being cut off.
- Peak voltage: The highest instantaneous voltage the signal reaches. This shows you the maximum level your source is delivering.
When to use it: Use the oscilloscope view to visually confirm your signal is clean, check for clipping at the source output, or compare signal shape before and after a processor.
FFT Spectrum View
The FFT (Fast Fourier Transform) screen shows a 2x2 grid of frequency spectrum graphs, one per channel. Instead of showing the signal over time (like the oscilloscope), it shows which frequencies are present in the signal and how strong each one is.
What you see on each channel panel:
- Frequency spectrum: A graph with frequency on the horizontal axis and level on the vertical axis. Peaks in the graph correspond to the dominant frequencies in your signal.
- Peak frequency: The frequency with the highest energy. Useful for confirming a test tone is at the expected frequency, or identifying the dominant note in music.
- Peak hold: The highest level reached at each frequency stays visible briefly before fading, making it easier to catch transient peaks.
When to use it: Use the FFT view to verify crossover frequencies, check that your EQ adjustments are doing what you expect, identify noise or interference frequencies, or confirm that a test tone is the correct frequency.
THD Analyzer View
The THD (Total Harmonic Distortion) analyzer provides detailed distortion measurements for a single channel at a time. This screen shows a frequency spectrum with markers highlighting the fundamental frequency and its harmonics, plus numeric readouts of key measurements.
Measurements displayed:
| Measurement | What It Means |
|---|---|
| THD% | Total harmonic distortion as a percentage. Lower is better. A clean signal from a quality source is typically below 0.01%. |
| THD (dB) | The same distortion measurement expressed in decibels. More negative numbers mean less distortion. |
| THD+N | Total harmonic distortion plus noise. Includes both harmonic distortion and background noise in one number. |
| SNR | Signal-to-noise ratio. How much louder the signal is compared to the noise floor. Higher is better. |
What you see on the graph:
- Fundamental marker: Highlights the main frequency of your signal (for example, 1 kHz during a test tone)
- Harmonic markers: Shows where the 2nd, 3rd, 4th (and higher) harmonics appear. These are the frequencies that make up the distortion.
Display modes: The THD screen offers four viewing modes that you can cycle between. The order is Spectrum to Oscilloscope to FFT Bars to 3D Waterfall, then back to Spectrum:
- Spectrum - Detailed frequency response curve showing the full spectrum
- Oscilloscope - Time-domain view of the signal being analyzed
- FFT Bars - Multi-band frequency bar display for a simplified overview
- 3D Waterfall - Spectrum history scrolled over time so you can see how the frequency content evolves
When to use it: Use the THD analyzer when you want precise distortion numbers, for example comparing signal quality before and after a component, verifying that a DSP or processor is not adding distortion, or measuring the noise floor of your signal chain.
Tools Page
The Tools page hosts a set of sweep-based measurements. Each one builds a response curve in real time as you play a sweeping test tone into the SSA, so you can see how a channel behaves across the whole frequency range rather than at a single tone. It is one of the main pages on the SSA touchscreen and opens as a launcher with three tools:
- Frequency Response: Shows how evenly the signal level holds across the frequency range, so you can spot rolloff or peaks. The curve is plotted from 5 Hz to 20 kHz with signal level on the vertical axis.
- Distortion vs Frequency: Shows how harmonic distortion changes across the frequency range, with distortion percentage on the vertical axis. Useful for confirming that distortion stays low at every frequency, not just at one test tone.
- Crossover Detector: Captures a frequency response curve and then marks the rolloff points on either side of the main peak (the -3 dB points). Use it to confirm where a crossover is rolling off a channel when checking high-pass and low-pass settings on a connected source or DSP.
Running a Measurement
Each tool has a channel selector, a Start/Stop button, and labeled frequency and level axes.
- Open the tool and use the channel selector at the top to choose which channel to measure.
- Press Start. This clears any previous curve, so each run is a fresh measurement.
- Play a sweeping tone into that channel's input, for example a sine sweep from the AuralSync app Tone Generator or any external signal generator.
- The curve fills in as the swept tone moves across the frequency range.
- Press Stop to freeze the result for review. On the Crossover Detector, the rolloff markers appear once you stop.
Each channel keeps its own captured curve, so you can switch channels with the selector without losing a measurement. The first time you open a tool, an on-screen guide explains these steps; tap the ? icon to bring it back at any time. Use the Back button to return to the screen you came from.
Settings
The settings screen is organized into four tabs that you can tap to switch between: Display, System, Custom, and WiFi.
Display tab
- Screen brightness: Slider that adjusts the backlight level.
- Screen timeout: Checkbox to enable the timeout, plus a slider to set how long the display stays on before dimming after no touch input.
- UI Sounds: Checkbox to enable or disable touch feedback sounds.
- Touch Debug: Checkbox that overlays touch input debug info on the screen.
- Calibrate Touch: Button that launches the touchscreen calibration routine. Use this if taps are landing in the wrong place.
System tab
The System tab (also called System Info) shows read-only device information and provides a couple of system buttons:
- Firmware versions for both the mainboard and the daughtercard display, plus the hardware version of each board.
- Bluetooth pairing PIN that you read off the screen when pairing a phone or app to the SSA.
- Start OTA Update button to manually trigger a firmware update check over WiFi.
- Reset button that reboots the device.
The SSA has two independent firmware versions, one for the mainboard and one for the daughtercard display. Both versions appear on the System tab. This is normal and expected, and both are kept in sync by the over-the-air update process.
Custom tab
- Custom channel names: One text field per channel where you can enter a label such as "Front L", "Sub", or "Rear R" so you can identify each channel at a glance on the analysis screens. The names persist across reboots.
WiFi tab
- Manual entry: Type in the SSID and password of your WiFi network directly.
- Scan: Pick from a list of nearby networks discovered by the device, then enter the password.
The SSA connects to your WiFi network to check for and download new firmware versions over the air.
Navigating Between Screens
Each main screen (Oscilloscope, FFT, THD) has its own dedicated channel panels. To switch between the three main views, use the gear/menu icon at the corner of the screen. Inside the FFT and Oscilloscope screens, tapping a channel's panel zooms into that channel's THD detail view. The Settings screen is reached from the gear icon on any main screen. On the THD detail view, use the navigation controls to cycle through the four display modes.
The Tools page is available alongside the Oscilloscope, FFT, and THD views. Open a measurement tool from the Tools launcher, and use its Back button to return to the page you came from.
Get the SSA
Shop the Smart Signal Analyzer at lf-audio.com.