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PurePath™ Smart Amp User Manual (TAS5766M/68M)
Jorge Arbona
PurePath™ Smart Amp provides powerful tools to make speaker characterization and tuning
easy.
Smart Amp replaces traditional continuous power design principles and hardware based
speaker protection methods with algorithms that allow significant increases in peak power
output, loudness and sound quality relative to conventional amplifiers.
Smart Amp tools allow developers to understand how speakers are performing in the
system and then make informed decisions to improve performance. The algorithms,
characterization and tuning tools allow developers to overcome a wide variety of audio
challenges.
Recipient agrees to not knowingly export or re-export, directly or indirectly, any product or
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including software, or any controlled product restricted by other applicable national
regulations, received from Disclosing party under this Agreement, or any direct product of such
technology, to any destination to which such export or re-export is restricted or prohibited by
U.S. or other applicable laws, without obtaining prior authorization from U.S. Department of
Commerce and other competent Government authorities to the extent required by those laws.
This provision shall survive termination or expiration of this Agreement.
According to our best knowledge of the state and end-use of this product or technology, and in
compliance with the export control regulations of dual-use goods in force in the origin and
exporting countries, this technology is classified as follows:
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EU ECCN: EAR99
And may require export or re-export license for shipping it in compliance with the applicable
regulations of certain countries.
TI Information – Selective Disclosure
ABSTRACT
WARNING: EXPORT NOTICE
Application Report
SLOU – August 2015
High Performance Analog / Audio
1
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Summary of Contents for Texas Instruments PurePath TAS5766M
- Page 1 TI Information – Selective Disclosure Application Report SLOU – August 2015 PurePath™ Smart Amp User Manual (TAS5766M/68M) Jorge Arbona High Performance Analog / Audio ABSTRACT PurePath™ Smart Amp provides powerful tools to make speaker characterization and tuning easy. Smart Amp replaces traditional continuous power design principles and hardware based speaker protection methods with algorithms that allow significant increases in peak power output, loudness and sound quality relative to conventional amplifiers.
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Page 2: Table Of Contents
SLOU TI Information – Selective Disclosure Contents General Overview ..........................4 1.1 Supported Smart Amp Devices ....................4 1.2 Migrating from Previous Versions of Smart Amp ............... 4 1.3 What is Smart Amp?........................5 1.4 Smart Amp Features ......................... 6 1.5 Smart Amp Development Overview .................. - Page 3 TI Information – Selective Disclosure SLOU A.2 Left and Right Drivers in the Same Box .................. 47 A.3 Parallel/Series Drivers in the Same Box (no analog crossover) ..........48 A.4 Parallel Drivers in the Same Box (analog crossover) .............. 49 Appendix B.
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Page 4: General Overview
SLOU TI Information – Selective Disclosure General Overview Chapter describes Smart Amp, its features and the hardware and software tools required for evaluation and development. Chapter describes how to install the PurePath™ Console 3 software. Chapter discusses how to perform a speaker characterization. Chapter explains how to tune loudspeakers with Smart Amp. -
Page 5: What Is Smart Amp
TI Information – Selective Disclosure SLOU What is Smart Amp? Conventional hardware-based speaker protection matches the continuous power output of the audio amplifier with the speaker output rating and sometimes incorporates high pass filtering to prevent over-excursion. PurePath™ Smart Amp replaces hardware based speaker protection methods with predictive algorithms, speaker characterization tools and real-time signal monitoring to increase the peak output of the speaker without damage. -
Page 6: Smart Amp Features
SLOU TI Information – Selective Disclosure Smart Amp Features Smart Bass Bass can easily be extended into any alignment automatically. As signal amplitude is increased in the bass region, Smart Bass automatically Automatic morphs the response to accommodate for larger Morphing Bass Compensation excursion. -
Page 7: Smart Amp Development Overview
TI Information – Selective Disclosure SLOU Smart Amp Development Overview The following steps summarize Smart Amp evaluation, planning, characterization, tuning and integration: Obtain Hardware and Software Plan for Development Obtain Speaker Parameters Tune Speaker End-system Integration Complete! Figure 2. Smart Amp Development Overview 1. -
Page 8: What's Needed
SLOU TI Information – Selective Disclosure What’s Needed The table below shows the hardware and software requirements organized by configuration type (e.g. 2.0, 2.1 or 4 channel). All the configurations require the Learning Board for characterization. The Target EVM is required to generate code to be implemented in the end- system. -
Page 9: 1.6.1 Obtaining Ti Hardware And Software
TI Information – Selective Disclosure SLOU 1.6.1 Obtaining TI Hardware and Software TI approval is required to order Smart Amp-related hardware and software. Click the button in the Target EVM web site to begin the approval process. Once approved, the user will receive an email confirming access to the mySecureSoftware web site and hardware ordering... -
Page 10: 1.6.2 Miscellaneous Equipment
SLOU TI Information – Selective Disclosure 1.6.2 Miscellaneous Equipment In order to perform a full characterization the following hardware is recommended. Some of these items are not needed if loudspeaker parameters are known. Table 2. Miscellaneous Equipment Equipment Description Weight Scale 20g in 1mg increments preferred. -
Page 11: Things To Consider During Development
TI Information – Selective Disclosure SLOU Things to Consider During Development Characterization and tuning speakers provide previously unavailable information on the loudspeaker performance and how to improve it. Most customers find this leads to changes in the system. These changes to improve performance can affect the timeline if this isn’t taken into account up front. -
Page 12: Software Installation
SLOU TI Information – Selective Disclosure Software Installation The following software is required to run Smart Amp. 1. PurePath™ Console 3 2. MATLAB Runtime Smart Amp-related Apps are downloaded directly from PurePath™ Console 3 using its App Center (refer to Section 2.3). PurePath™... -
Page 13: Getting Smart Amp Apps
TI Information – Selective Disclosure SLOU Getting Smart Amp Apps PurePath™ Console 3 Apps are downloaded using the App Center Follow these steps to download Smart Amp specific Apps: 1. Download the PurePath™ Console 3 software from the PUREPATHCONSOLE Software Product in mySecureSoftware. -
Page 14: Loudspeaker Characterization
SLOU TI Information – Selective Disclosure Loudspeaker Characterization The main objective of the loudspeaker characterization is to obtain the electro-mechanical and thermal parameters and establish the safe operating area (SOA) of the loudspeaker system. The electro-mechanical and thermal parameters are obtained using the Learning Board. -
Page 15: Characterization Summary Page
TI Information – Selective Disclosure SLOU Characterization Summary Page The Characterization Summary page shows the results of the loudspeaker characterization. To verify the loudspeaker plots, use the controls to the top of the graph: Selects between Modeled SPL and Excursion or Measured Impedance, Temperature and SPL plots. -
Page 16: Smart Amp Tuning
SLOU TI Information – Selective Disclosure Smart Amp Tuning Tuning is a process involving both subjective and methodical approaches. This section provides guidelines to help establish a baseline to achieve the best possible tuning. The main objectives of the (iterative) audio tuning process, also referred to as ‘voicing’, are: •... -
Page 17: Tuning Preparation
TI Information – Selective Disclosure SLOU Tuning Preparation Tuning is performed using the Learning Board or the Target EVM. 1. Connect the Learning Board or Target EVM to your PC using the USB cable. a. Provide a power supply (matching the one to be used in the final system). b. -
Page 18: Smart Bass Tuning
SLOU TI Information – Selective Disclosure Smart Bass Tuning During the characterization process, the low-frequency SPL model of the loudspeaker was obtained. Based on this model, the response is automatically optimized to match popular loudspeaker alignment types (e.g. Butterworth, Linkwitz-Riley, etc.). This allows the audio engineer to focus on choosing the desired sound with just a few clicks. -
Page 19: Bass Enhancement (Low Volume Tuning)
TI Information – Selective Disclosure SLOU 4.2.1 Bass Enhancement (Low Volume Tuning) Set CORNER The main objective is to maximize the bass response as much as FREQUENCY possible and tune the bass as desired. During this phase it is important to listen at low volume levels only – this is to ensure that Set alignment ORDER thermal and mechanical protection systems do not kick-in. - Page 20 SLOU TI Information – Selective Disclosure Alignment Order and Type The Order and Type determine the bass roll-off. In other words, it determines what occurs below the corner frequency. A high-order roll-off cuts bass faster saving power and limiting speaker excursion that won’t produce much SPL.
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Page 21: Morphing Control (Mid- To High- Volume Tuning)
TI Information – Selective Disclosure SLOU 4.2.2 Morphing Control (Mid- to High- Volume Tuning) Morphing determines the headroom dependent balance between Bass Enhancement and Harmonic Bass From Section 4.2.1 Alignment. As excursion and thermal headroom drops with increase in music loudness, the Morphing Set MORPHING to -15 dB feature gradually and dynamically reduces bass. -
Page 22: Harmonic Bass Alignment (Mid- To High- Volume Tuning)
SLOU TI Information – Selective Disclosure 4.2.3 Harmonic Bass Alignment (Mid- to High- Volume Tuning) The Harmonic Alignment control determines the aggressiveness of the To Section 4.2.1 From Section 4.2.2 excursion protection algorithm as speaker headroom is reduced. Some speakers sound Set MORPHING 5 to 15 dB great with an aggressive setting (high value) higher than in... -
Page 23: Smart Eq
TI Information – Selective Disclosure SLOU Smart EQ Smart EQ automatically tunes high frequencies to deliver a flat response or match a target curve. It is required measure SPL with a microphone during the characterization process in order to use the Smart EQ feature. To configure Smart EQ, go to the page and click the Expand symbol next to the Equalizer section, as shown below. - Page 24 SLOU TI Information – Selective Disclosure The SmartEQ section has two panels that can be swapped by clicking the button. The following controls are available: • Number of Biquads • Smoothing Factor • Dip Suppression • Spline Region • SPL Offset The Number of Biquads dropdown determines how many biquads are used to create the compensation curve.
- Page 25 TI Information – Selective Disclosure SLOU The Target Curve section allows the user to create their own signature sound by focusing on the final target response. The High Frequency Pass Through ignores the final dip of the Smart SPL response which would otherwise require a large amount of positive compensation that may not be audible and cause distortion.
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Page 26: Digital Gain Control
SLOU TI Information – Selective Disclosure Digital Gain Control For smaller loudspeakers it may be desired to use a Digital Gain setting lower than 0dB during playback at maximum volume. This is especially true when maximum SPL is achieved at much lower gain settings. -
Page 27: Hardware Design
TI Information – Selective Disclosure SLOU Hardware Design Smart Amp systems can operate at higher rail voltages than traditional systems while protecting loudspeakers. This is possible because Smart Amp understands the speaker characteristics. This allows control of excursion and temperature of the voice coil and the magnet while preserving the music peaks. -
Page 28: Power Supply Rail Voltage
SLOU TI Information – Selective Disclosure Power Supply Rail Voltage Traditionally, audio systems are designed to satisfy the power handling specification of a loudspeaker. There are several methods in which loudspeaker rated power is obtained, one of them discussed in the AES2 standard [1] [2]. Most tests involve a pink noise signal with a specified crest factor, bandwidth and roll-off over a period of time. -
Page 29: Power Supply Current At Audio Frequencies
TI Information – Selective Disclosure SLOU Power Supply Current at Audio Frequencies An ideal power supply can deliver infinite amounts of current without a reduction in its output voltage. In reality, a power supply maximum current output depends on its series impedance. In practical audio applications, where the decoupling techniques are limited by cost and size, audio frequencies are mostly driven by the supply itself and not by decoupling/bulk capacitors. -
Page 30: Figure 11. Power Supply Current Measurement
SLOU TI Information – Selective Disclosure A practical capacitor size will not help much with these peaks therefore it is recommended to design the power supply based on the expected peak currents. The peak current observed at the power supply can be approximated by calculating the maximum current into the load taking ��... -
Page 31: Power Supply Current At Higher Frequencies
TI Information – Selective Disclosure SLOU Power Supply Current at Higher Frequencies Power supply current is limited by its inductance at higher frequencies, which is due to a combination of the power supply itself, passives and PCB layout. The PWM output stage of a Class-D amplifier switches at a high frequency (>100 kHz) which may cause the power supply voltage to drop if not decoupled properly affecting the amplifier and other circuits as well. -
Page 32: Table 7. Tas5766M/68M Post-Processing Gain Controls
SLOU TI Information – Selective Disclosure The TAS5766M/68M has three post-processing gain controls, as shown in Table Table 7. TAS5766M/68M Post-processing Gain Controls Gain Type Control Type Gain Values �� Page 0 / Register 61 -103dB to 0dB DAC Fine Digital Gain Control (�� Page 0 / Register 62 ��... -
Page 33: Software Implementation And Verification
TI Information – Selective Disclosure SLOU Software Implementation and Verification Smart Amp first needs to understand the speaker and enclosure it will be connected to in the end product. TI provides a tool, called the Learning Board which extracts speaker parameters without the need of expensive equipment. -
Page 34: Importing The Speaker Parameters Into The Smart Amp Target Evm App
SLOU TI Information – Selective Disclosure Importing the Speaker Parameters into the Smart Amp Target EVM App To generate a header file, it is necessary to first import the speaker characterization and tuning data from a .ppc3 file into the Target EVM App (e.g. -
Page 35: Calibrating The System Gain In The End-System
TI Information – Selective Disclosure SLOU Calibrating the System Gain in the End-System Before integrating the Smart Amp code into the end-system, the System Gain must be determined and entered into the Smart Amp software. Vp,out The System Gain is a normalization factor that scales the voltage at the load to the digital level at the output of the DAC. - Page 36 SLOU TI Information – Selective Disclosure 4. Ensure the target End-System (i.e. customer’s board) is powered and the IO voltage of the I2C lines is 3.3V. 5. Ensure the target device hardware pins and external signals are configured correctly. For example, the TAS5766M requires the XSMT pin to be high and I2S signals to be present for the tone generator to work.
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Page 37: Smart Amp Register Dump Into A Header File
TI Information – Selective Disclosure SLOU Smart Amp Register Dump into a Header File Smart Amp devices have basic configuration registers as well as registers related its processing engine. By default, a Smart Amp device will boot in a simple, non-Smart Amp, predefined mode. The Smart Amp code would then need to be downloaded into Instruction RAM (I-RAM) and Coefficient RAM (C-RAM) of the processing engine. -
Page 38: Figure 14. Dump To Header File Page
SLOU TI Information – Selective Disclosure 2. Select the desired Snapshot. 3. In the End-System Integration page, select Dump Current State into a Header File. 4. Click the Dump to File button, as shown below. Figure 14. Dump to Header File Page PurePath™... -
Page 39: 6.3.1 Working With Non-Standard Configurations
DDFs can be found in the Appendix sections of the PurePath™ Console 3 User Manual [7]. The default DDF files can be found by searching *.ddf in the folder below: “C:\Program Files (x86)\Texas Instruments\PurePath Console 3\” PurePath™ Smart Amp User Manual (TAS5766M/68M) -
Page 40: Integrating The Output Header File Into The End-System
SLOU TI Information – Selective Disclosure Integrating the Output Header File into the End-System The PurePath™ Console 3 User Manual [7] provides detailed information an example code on how to parse a header file in the Appendix sections. The general concept is simple. The header file obtained from Section contains an array of two element structures in which the first member is the register address (or offset) and the second member is the data written to that register. - Page 41 TI Information – Selective Disclosure SLOU Once it is verified that audio is working, the Smart Amp System Gain calibration can be verified. System Gain Verification: 1. Calculate the expected thermal limit in volts RMS �� = � �� × �� using the following equation: ��ℎ_����������...
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Page 42: Changing Device Parameters On-The-Fly In The End-System
SLOU TI Information – Selective Disclosure Changing Device Parameters On-the-fly in the End-System If it is desired to change a parameter once the code is inside the end-system on-the-fly, its coefficient location must be determined. For example, if the designer wants to change the input (pre-processing) volume level, then he/she can generate two header files and use a compare tool to determine the coefficient location. -
Page 43: Support
TI Information – Selective Disclosure SLOU Support Smart Amp is supported through the Audio Amplifiers Support Forum. Please include the words Smart Amp and the part number in the subject line. Contact your local TI sales representative for additional details. PurePath™... -
Page 44: References
SLOU TI Information – Selective Disclosure References [1] AES2-1984: AES Recommended Practice Specification of Loudspeaker Components Used in Professional Audio and Sound Reinforcement. Audio Engineering Society, New York, NY., US [2] AES2-2012: AES standard for acoustics - Methods of measuring and specifying the performance of loudspeakers for professional applications - Drive units. -
Page 45: Appendix A. Supported Speaker Configuration Types
TI Information – Selective Disclosure SLOU Appendix A. Supported Speaker Configuration Types Supported speaker configurations types are described in this section. The speaker membrane area Sd of a circular speaker is obtained by measuring the diaphragm diameter with a metric ruler from center point to center point of the surround, as shown below. Diaphragm area for other speaker shapes, such as ‘racetrack’... -
Page 46: A.1 Free Field / Single Speaker In Box
SLOU TI Information – Selective Disclosure A.1 Free Field / Single Speaker in Box Electro-mechanical Characterization • Connections - Left Channel Speaker to the L+/L- (TEST) outputs of the Learning Board. • Bl - Enter the mass placed at the speaker when prompted. -
Page 47: A.2 Left And Right Drivers In The Same Box
TI Information – Selective Disclosure SLOU A.2 Left and Right Drivers in the Same Box Characterization • Connections Left Channel Speaker to the L+/L- (TEST) outputs of the Learning Board. Right Channel Speaker to R+/R- Bl - Add mass �� outputs of the Learning Board. -
Page 48: Parallel/Series Drivers In The Same Box (No Analog Crossover)
SLOU TI Information – Selective Disclosure A.3 Parallel/Series Drivers in the Same Box (no analog crossover) Electro-mechanical Characterization • Connections - Left Channel Speakers to the Bl – Add mass �� L+/L- (TEST) outputs of the Learning Board. �� • where ��... -
Page 49: Parallel Drivers In The Same Box (Analog Crossover)
TI Information – Selective Disclosure SLOU A.4 Parallel Drivers in the Same Box (analog crossover) A speaker cabinet with a bass driver and a tweeter is supported by employing excursion protection exclusively to the bass driver. The analog crossover frequency is assumed to be high enough such that the tweeter is not damaged by excursion. -
Page 50: Appendix B. Smart Amp End-System Implementation Checklist
SLOU TI Information – Selective Disclosure Appendix B. Smart Amp End-System Implementation Checklist Use this checklist to ensure all Smart Amp end-system implementation steps are followed and to keep a history of project tunings, versions and filenames. PROJECT NAME: ____________________________ TUNING VERSION: ____________ ☐... -
Page 51: Appendix C. Matlab Compiler Runtime Troubleshooting
TI Information – Selective Disclosure SLOU Appendix C. MATLAB Compiler Runtime Troubleshooting If an error message appears when launching the Smart Amp software: 1. Ensure MATLAB Compiler Runtime (MCR) is installed as described in Section 2.2. 2. Close PurePath™ Console 3. 3. -
Page 52: Revision History
SLOU TI Information – Selective Disclosure Revision History This revision history highlights the changes made to this application report. Revision History Version Date Author(s) Additions/Modifications/Deletions SLOU 20150820 J. Arbona Added additional details to the Smart SPL section. J. Arbona, H. Rajagopala, C. Neesgaard, S.
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