HX3 Sweep Generator (english)
Preface
Starting with sound engine version #11122025 (FPGA) and firmware 7.060, a sine wave test generator is built into HX3, which is used to check threshold settings (range, loudness, AO28 frequency response), vibrato, phasing rotors, and external effects devices. This feature was initially intended for development purposes only, but we have now included it in the official Manager version. It is even possible to check the frequency response of a historical organ by switching the effects input to the measurement signal (see below). The internal sine wave generator with tunable frequency is fed internally before PHR and vibrato effects when the Sweep tab is active in the HX3 Manager, as shown in the adjacent image.
Attention: After selecting the “Swell Sweep” tab, a rather loud test tone will be heard. Leaving the tab will turn it off again.
Loading Measurements and Reference Curves
Click on “Sweep Load” and select one of the supplied “sweep_xxx.csv” files in the user directory. This fills the measurement table below and displays a dimmed set of curves.
Saving of Measurements
Click on “Sweep Save.” The table will be saved as a CSV file (text, importable into Excel).
Creating a new Measurement
For initial measurements, switch off Reverb, Vibrato, and Phasing Rotor and set the internal equalizer to Bypass.
A new measurement always uses the frequencies specified in the “Freq Hz” column, so you can also create your own frequency curves or use those from an existing measurement series. You can create a new table by clicking on Sweep New. The number of measurement points (table rows) depends on the adjacent drop-down menu. You can achieve particularly fast, rather rough measurements with the Short setting, while the Fine selection produces a significantly finer frequency resolution. The table is generated algorithmically, but you can change (and save) individual values in the frequency table as you wish.
Audio Levels
Levels indicated in Swell/Sweep analyzer are arbitrarily referenced to full 16 bit digital level with 0dB = clipping limit of 32767 counts. Indication will not align with external measurement of analog audio signals.
For the following checks, set Swell Test (or swell pedal) and Master Volume to full (127), Test Generator Level to -20.2dB (3192), TubeAmp and Speaker to Bypass ON. If available, connect an external millivoltmeter to audio output jack to be observed.
With Test Generator Frequency of 1024 Hz, Measure external FX Loop checked (will bypass preamp/swell simulation), observed analog output level on main outputs should be about 630mV RMS or -1.8dB. Observed output level on separate organ output is lower at 170 mV RMS or -13dB. Both will not vary sigificantly with frequency changes as there is no swell simulation.
With Test Generator Frequency of 225 Hz, Measure external FX Loop unchecked , observed output level on main outputs is about 750mV RMS or -0.5dB. It will vary with frequency due to preamp simulation.
Sweeps
Frequency sweeps determine the amplitude response of audio electronics at different frequencies. The frequency response is particularly important for the sound impression in preamp simulation. In most electromagnetic organs, a moderate drop toward higher frequencies can be observed from around 250 Hz; This is caused by both the preamp and the drawbar matching transformers and is entirely desirable.
A license is required for sweeps and auto sweeps, which you can order from us, see #Setting up the License.
Measuring the frequency response of the preamp simulation
Select the “Preamp out” input using the drop-down menu at the top left. The “Level Detect” bar should now display a level that depends on the threshold setting. You can change the level and frequency of the test signal (sine wave) using the “Test Generator Level” and “Test Generator Frequency” trackbars. With the threshold set to maximum, set the frequency to 225 Hz and adjust the “Test Generator Level” so that a “Level Detect” of approximately -10dB is displayed. The level will change slightly as you tune the test generator.
Single Sweep
Click on “Sweep Single.” The test generator generates a series of frequencies based on the table, lists the measured values in the table, and displays the resulting measurement curve in the graph. Each new click on “Sweep Single” generates another series of measurements (up to 8 “runs”), allowing you to immediately compare different preamp parameters or different threshold settings. In any case, the dimmed display of a previously ‘loaded’ dimmed measurement series in the graph is not overwritten (only when you click on “New”).
Auto Sweep
This function is used to check the frequency response at different threshold settings (0%, 5%, 10%, 15%, 25%, 50%, 75%, 100%), which is important for the loudness correction of the AO28 preamp. Eight “runs” are performed, each with a different threshold setting (parameter #1600). This results in a set of curves as shown in the image above. To do this, click on “Sweep Auto.” The process can be canceled at any time by clicking on “Stop.”
Saving Swell Settings in HX3
Unlike earlier firmware versions, a fixed swell loudness curve (editor parameter #1384, now obsolete) is no longer used. Instead, individual swell behavior can be set for each organ model using the new parameters #1091 to #1095 (found under “Volume Pots”), similar to the previous trim cap and minimal swell settings.
Once you have found a satisfactory setting, you can save it to the HX3 board using “Store to Organ”. The button and selection of organ models using the drop-down menu have the same function as the controls of the same name in the “Organs” tab and are only provided here again for convenience, so that organ models can be quickly compared.
Using EFX Input
Using the “EFX Input” effects loop input (HX3.7 only), it is also possible to measure external devices and the HX3 equalizer. If the “Measure External FX Loop” checkbox is active, the level detector is set to the HX3's effects loop input, and the test generator's unmodified signal appears at the organ output. The internal preamp simulation is ‘’'switched off'‘’, so the frequency response is completely linear.
Measuring External Devices
To test, connect the “Organ” output directly to “EFX Input” using a jack cable and set the effect level control to the right stop. A sweep should now produce a ‘’'linear frequency response'‘’.
With this configuration, you can measure the frequency response of an effects device that is looped between “Organ” and “EFX Input,” for example. Professionals can even measure the frequency response of their historic organ; to do this, the output signal at “Organ” is fed via a 1 kOhm resistor to one of the organ's middle preset bus bars and picked up again at ‘’'one'‘’ of the G-G outputs and ground. Note that the output level at the G connection is very high, so the EFX level control must be turned to the left.
HX3 Equalizer Measurement
The internal equalizer of the HX3 DSP can be difficult to adjust due to its parametric structure, especially with regard to quality (peak) and exact frequency. A sweep greatly simplifies critical settings.
Connect the “Organ” output directly to “EFX Input” using a jack cable and set the effect level control to the right stop. A sweep should now produce a linear frequency response. Now switch the equalizer bypass to “Off” and play around with the equalizer settings (on the device or via the HX3 Manager panel). This will produce curves that clearly show the equalizer settings.
Setting up the License
The test tone generator and level measurement function are always available. However, sweeps and auto sweeps require a license, which you can order from us (be sure to include the serial number of your HX3!). Entering the license number unlocks the sweep functions.
After connecting your device in the HX3 Manager start window, click on Manager License. Your device serial number and, if applicable, your name should now appear in the About dialog box as the “Customer Name.” Now enter the “Customer Name” and “Sweep Generator License Key” exactly as they appear in our confirmation email. Click on Activate. A check mark will now appear next to the license number. Close the window with OK.
The license data is stored in the file HX3_userinfo.txt in the editor_files directory. Keep a copy of this file in a safe place. The file can be transferred when selling the software or copied to the new HX3 Manager directory (again in editor_files) when installing an update (from a ZIP file) in order to transfer the license for the update.
Sweep Analyzer
The test generator and analysis functions are also available as a standalone program in the form of the application HX3_SweepAnalyzer.exe (contained in ZIP of firmmware update). The larger window allows for a clearer display, operation is the same as above. The HX3 Manager must not be connected when starting. You can install and use this program separately from the HX3 Manager; it only requires the user and editor_files directories and uses the same license code as for HX3 Manager.
