Category Archives: BLOG
Welcome to BuildAudioAmps
Welcome to our website. We are glad you are here. If this is your first time visiting us, thank you! We suggest you check out Project 65 in the “Recently added” section on the right side of the homepage.
You can also explore other projects by going to the “PROJECTS” menu bar on top of this page for a quick overview of each project or perhaps the “More Projects” section found at the bottom of this page–if your time allows. There are over more than 90 pages of published projects in the website with detailed instructions and test results.
Another option is to visit the BuildAudioAmps YouTube channel, we just started posting presentation videos in that channel. It's where you will also find more audio power amplifier projects, videos and tips.
We are grateful to receive feedback and insights from the members who showed interest in a published project and completed their own versions of the project. We acknowledge the time and effort they have invested in providing valuable suggestions and constructive criticism.
And now more projects…
The previous series of audio power amplifier projects that I was working on was using the LME498xx series of high voltage input stage drivers. I have posted several of them starting with Proj8, Proj11~25 and finally in Proj39~42, but there’s really more than that and have not been posted in the website as shown in the Tinkerer’s Workshop. It all started with Proj8 when I had the PCB fabricated professionally to verify basically its layout quality. As a result of the first build the audio quality it reproduced and represented was very impressive!
At present I’m working on a new series of audio power amplifier projects that uses an op amp at the front-end input stage of the amplifier. Currently, there are 16 amplifiers so far that have been built and tested starting with Proj62.
Here’s a look at some of the completed projects:
This one is rated at 100 watts using Linear Technology LTC6090 that’s driving a pair of ThermalTrak transistors.
The next one is another 100-watt amplifier using an Analog Device ADA4700-1 connected to a complementary pair of Darlington transistors from Sanken.
This one is a 100-watt amplifier using Linear Technology LT1166, which controls the bias and effectively eliminates the matching of the QFET MOSFETs.
Project 65 is the fourth in the series of audio power amplifier projects that uses an op-amp in the front-end stage of the amplifier. The CFA-based op-amp input stage is connected to a full complementary hybrid compound feedback pair output stage. Applying a 1KHz 1.84Vpp input signal, the amplifier produces 35.82Vrms across an 8Ω load when connected to a ±56.6VDC power supply rails and a THD of 0.002% as measured by a QA400 audio analyzer. The amplifier sounded powerful enough even though it puts out less than 200watts into an 8Ω load. 
The TDA8950 is a high-efficiency Class D 2-channel audio power amplifier chip. The typical power output is 150Watts per channel with a speaker load impedance of 4Ω. The TDA8950 chip operates over a wide supply voltage range from ±12.5 V to ±40 V and features low quiescent current consumption. For this project the TDA8950 is configured as a mono Full Bridge Class D power amplifier. This configuration was chosen to effectively avoid a strange phenomenon of a typical Class D power amplifier called "pumping effect". The BTL power output is 300watts at 8Ω with ±37VDC PS rails. 
This is another audio power amplifier project in the series that uses an op-amp in the input stage. The prototype is populated with eight 800V/20A/200W NPN power transistors from Fairchild Semiconductor configured in a quasi-complementary output stage topology. These T0-264 packaged power transistors are typically intended in high-voltage color display horizontal deflection circuit applications but performed very well in this project. Initial test results shows that the amplifier is capable of producing a power output of more than 300 watts into an 8Ω load with ±72VDC power supply rails. 
This is another audio power amplifier project in the series that uses an op-amp in the input stage of the amplifier. The complementary 200V 16A 250W TO3-packaged output stage transistors from On Semiconductor are excessively biased about 500mA of current per transistor. The prototype when connected to a ±35VDC power supply rails was able to produce a power output of 50 watts into an 8Ω load with a THD of 0.00186% and a flat 20Hz to 20KHz frequency response as measured by a QA400 audio analyzer. The overly biased amplifier reproduces surprisingly pleasant listening experience.