Digital Amplifiers


 Russell Storey




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Hottest Articles
New Form Research The Dawn of the Direct Digital Chain
New Form Research Silicon Symphony Moore's Law Catches up with High Fidelity Audio
EDN Access EDN ears-on project: Listening to Class D
Press Release LG Electronics Intros DVD Player for Home Theater That Includes Pure Digital Amplifiers
Positive Feedback Magazine A great article about the Spectron digital audio amplifier. Todays chip based digital audio amplifiers all share the sonic advantages which are described in this article at a tiny fraction of the price of a hand built discrete digital amplifier.
January 2002
Press Release Apogee's DDX® Amplifiers Power Zenith DVD Surround Sound System
Press Release Apogee Technology Inc. Showcases New Products Incorporating its DDX® Amplifier Technology at the Consumer Electronics Show (CES)
Press Release Pulsus Technologies has introduced a full line-up of VLSI solutions for digital pulse modulation amplifiers helping to shape the future of Digital Audio
Press Release Tripath Provides Leading Audio Suppliers Solutions for CES Award Winning Designs
Press Release Tripath's Digital Audio Amplifiers Power Zandiant's Mobile Entertainment Systems
Press Release Tripath Expands Class-T Family with New High-efficiency Digital Audio Amplifier Chipset
Press Release Tripath Launches Two New Products
November 2001
Press Release Apogee Technology, Inc. Announces New DDX® Power IC 
Low Cost DDX-2100 Meets Market Need For 100 Watt Digital Audio Solution 
Press Release Tripath Provides Solution for Hitachi Plasma Televisions
Press Release Tripath Powers World's First 4 x 100w In-Dash Car Audio Head Unit
October 2001
Press Release Tripath Provides Digital Amplifier for New Hitachi Plasma Television
Press Release Sharp Selects Tripath's Digital Audio Amplifiers For World's Largest Flat-Panel Television System
Press Release Yamaha Adopts Tripath's Digital Power Processing Technology for CD-R/RW Receiver System
September 2001
ClassD org Tip Voigt of Class D dot org - Attempts to uncover some of the mis-conceptions and myths about PWM Digital Audio Amplifiers.
Press Release Microsemi Introduces Next-Generation Class-D Stereo Controllers For Multimedia, Portable and Automotive Applications
Press Release Tripath chosen by AIWA to provide digital audio for Home Entertainment System, begings volume shipment of products
Press Release Tripath's Digital Audio Amplifiers chosen by Plasma Television Manufacturers
August 2001
EDN Access EDN ears-on project: Listening to Class D
July 2001
EDN Access The Power of Class D in wireless applications
June 2001
Press Release Tripath to Power Motorola's First Consumer Integrated Home Entertainment System
May 2001
Press Release LG Electronics Intros DVD Player for Home Theater That Includes Pure Digital Amplifiers
Press Release Cirrus Logic’s New TrueDigital™ Class D Amplifier Chips Spark New Generation of Sleek, Energy-Saving Consumer Electronics
Stereophile Cirrus Logic announces two new high-efficiency class-D audio amplifier chips
April 2001
Commverge Magazine Apogee Releases Multi-Channel Digital Audio IC
ECN Magazine Mitsubishi Intros Digital Amplifier Processor Chip
Chip Center Mitsubishi Digital Amp Processor Boosts Audio Power Efficiency 
Chip Center Product Review - Mitsubishi Electric M65817FP Digital Audio Processor
AudioXpress Digital Class-D Subwoofer Amp part 2
Stereophile Texas Instruments Announces Ultimate Hi-Rez Audio Chip
Press Release Tripath Technology Delivers High-Quality Sound in the newest Sony Flat-Screen Television
March 2001
New Form Research Moore's Law Catches Up With High Fidelity Audio
Press Release Sanken Intros 80 Watt Digital Amplifier Chip
AudioXpress Digital Class-D Subwoofer Amp part 1
Electronic Products Audio chipset is all digital
Press Release Tripath Digital Audio Amplifier Brings High-Fidelity Sound to New Hitachi 32-inch Plasma Screen Televison
February 2001
Commverge Magazine 5th Dimension - Bits Delivered; The debut of all-digital audio
Electronic Products Amplifier Chip Eliminates D/A
ElectronicsWeb Apogee Technology Announces Exclusive License Agreement with STMicroelectronics for its All-Digital Amplifier Technology
Link2Semiconductor Apogee Technology Is Doing Its Part to Stimulate the Consumer Electronics Market
Mi2N Apogee Technology Announces Exclusive License Agreement with STMicroelectronics For Its All-Digital Amplifier Technology
Portable Design Partnership Gives Design Privileges for Amplification Technology
EETimes Class D amps turn down heat in portable audio systems
Press Release Microsemi Class D Audio Chosen to Drive Benwin Flat Panel Speakers
January 2001
ECN Magazine All Digital Amplifier Chipset
EDN Magazine Amplifiers Deliver a Digital Gain
EE Product News Digital Amp Chipset Eliminates Need for DACs
Electronic Design Direct Digital Amplification Improves Efficiency and Eliminates Heatsinks
Mi2N Apogee Announces Major Design Win - Direct Digital Amplification (DDX®) Technology Helps Altec Lansing Pack Superior Sound into Micro-Speaker Package
Press Release Motorola & B&K Components Unveil Symphony® Amplifier Technology as the Next Step to a Fully Digital System-On-Chip Implementation for Audio 
3D Sound Surge Motorola & B&K Symphony® Amplifier Technology Will Be Implemented Within Powerful 24-Bit Programmable DSP and Other Motorola Processors for a Variety of Audio Applications 
Press Release Digital-to-digital converter boosts audio performance
Press Release Tripath TA1101 Digital Amplifier Featured in Apple's New Power Mac G4
Press Release Tripath Class-T Digital Amplifier Drives Blaupunkt Car Audio Amplifier
Press Release Audiosource Adopts Tripath's Digital Power Processing Technology For Its Latest Amplifier
Press Release Tripath Launches New Class-T Digital Amplifiers
Press Release New Tripath Class-T 1 Bit Digital Amplifier Powers Marantz ER3000 Home Cinema System
December 2000
EETimes Digital stereo amp chip set eliminates the need for D/A
Stereophile Digital Audio Amplification Reaching Critical Mass?
October 2000
Stereophile Cirrus Logic Buys Pulse Width Modulation Patents from B&W
July 2000
Stereophile Sharp SM-SX100 digital integrated amplifier
March 2000
Stereophile Texas Instruments Acquires Danish Digital Amplifier Company
Feb 2000
Press Release Scientists develop technology to amplify digital audio signal
March 1999
Press Release Sharp Introduces New 1-Bit Amp and Super Audio CD Player World's First "Direct Bitstream Coupling" Between a 1-Bit Amp and a CD Player Thin Form-Factor in a Next-Generation Super Audio System
Nov 1998
Stereophile Class-T Amplifiers Announced
Date Unknown
Positive Feedback Magazine A great article about the Spectron digital audio amplifier. Todays chip based digital audio amplifiers all share the sonic advantages which are described in this article at a tiny fraction of the price of a hand built discrete digital amplifier.

First, you need some equipment and material

And now to the actual work.

Most SMT components are too small to hold and solder at the same time.

If you are just soldering a few components, here is a good method

  1. Melt a small amount of solder on one of the solder pads
  2. Hold the component in place with a tweezers
  3. Melt the pad with the solder. Push the component lightly down on the PCB so it mounts flat. Let the pad cool.
  4. Solder the second (and other) pads
  5. Melt the first pad again and let it cool down


For "large" components like SMA, SMB and SMC size diodes, I usually move the solder iron sideways relative to the component, soldering along the pad, from one corner to the other. This usually distributes the solder evenly. A similar method can be used for 0805 size components.

For small multi connector packages, like the main chip of the AMP3, or the chips of the AMP2 it is important to be careful, as it can be difficult to repair mistakes. I recommend the following procedure.


Alternative ways of soldering SMT components

If you are soldering a quantity of components, here is a rational way. Use epoxy glue to fix the components to the board before soldering. You should use SMT type epoxy like Loctite 3609. It is expensive but good. I usually apply the epoxy to the PCB with a small syringe. Only a small spot is needed for each component. The epoxies suited for this is are of a one component, heat-curing type. They do not harden until you heat them to around 100C for about one minute. Therefore, you have plenty of time. I use the following procedure:


  1. If there are components to be soldered in an oven, do this first. If not, you can skip to (B) below...
  2. Spread solder paste to all PCB pads that should be soldered in the oven
  3. Place the components on the PCB
  4. Pace the PCB in the oven
  5. Preheat to about 140C for two minutes
  6. Increase the temperature to get a peak temperature of about 220C. The time above 200C should be 30-40 seconds
  7. Let the PCB cool slowly. Don not force cooling.


  1. Bring out all the SMT components required for a board
  2. Place epoxy dots on the PCB
  3. With a small pincer, place the components on the board
  4. When all SMT
    components are in place, bake the board in an oven at 100 C for about two minutes
  5. Take the board out and place it on the table heater
  6. Solder the SMT components.

The procedure above may seem complicated, but once you get the hang of it you will probably work faster this way, than with traditional through-hole components. Further, down on this page you can find more about the details of how to solder SMT components.


Now finally add any through-hole components To the PCB

Soldering in an oven

Components that have connectors that are not accessible, like bottom side cooling pads, need to be soldered in an oven. For the 41hz audio amps this only applies to one of the chips of the AMP2. A small toaster oven or other domestic oven will do. Do NOT use the same oven for food unless you are prepared to do a thorough cleaning. You do not want lead in your food and you do not want grease in your PCBs. For repeated use, I recommend you get a separate little oven toaster for the PCBs. You could even make a simple oven by using an ordinary kitchen pot on your stove. Preferably, use a stainless steel pot with a lid and a good thermometer. Most solder melts at around 180 C. When soldering, you have to go a bit higher the melting point temperature, to get a good wetting and ensure proper melting. On the other hand, components can be damaged if heated to much.

Hot air soldering
Yet another possibility is to use a hot air gun. I have not tried this and would use it with precaution so that components are not damaged. Is there anyone out there who has tried this or has comments or ideas?


I usually solder the heat slug of the heat dissipating AMP2 chip in an oven, or skip the soldering and use heat transfer paste between chip and PCB and put a small heat sink on top. Of course the legs of the chip have to be soldered. The chip is rated to be soldered at 270C for 10s (typical solder specification for chips). Solder melts at 180C and is very fluid at 190-200C. I would say it is impossible to heat both PCB and chip in a controlled manner with an iron.



Well you can also solder the "normal, way" but then add heat transfer paste between chip and PCB for better cooling. Or add a heat sink on top of the chip.

If I would solder the chip, or have it done, I would like to test it before delivery but that would be difficult, without building the rest of the board.