I am onto learning and building electronics, and as a start I decided to build audio amplifiers. But of late the search for a good IC is becoming tough as there is an overwhelming amount of options.

So what is the general rule of thumb a pro follows when they do the search?

I also came across some resources, RaneNote - Audio Specifications and Understanding Amplifier Power Specifications from rayfes.com, that highlighted what needs to be the correct value any datasheet should show. If true, how to find out their values from the datasheet itself?

For eg, this IC MAX9709 does not specify the measured bandwidth of THD+N (if I am looking correctly). So how can I find out?

PS: i was searching for
- Class d
- Input power - 12V
- Bluetooth, USB
- Output power(RMS) - 80W
- Efficiency > 90%
- Total Harmonic Distortion(THD) <1%
- Signal to Noise Ratio(SNR) > 90dB - Frequency Response - 3dB from 20Hz to 20kHz

So even after such considerations, there is surely some other factors a designers look for apart from cost. How do they make it easy for themselves.

  • \$\begingroup\$ link to ic MAX9709 \$\endgroup\$
    – arjun
    Apr 25, 2014 at 12:10
  • 2
    \$\begingroup\$ First, you have to establish some overall requirements for the amplifier you want to build, such as power level, performance criteria, cost, size, etc. Then, you look for parts (or combinations of parts) that will meet those requirements. \$\endgroup\$
    – Dave Tweed
    Apr 25, 2014 at 12:19
  • \$\begingroup\$ Those resources you linked are great sources of info on amplifiers. +1 \$\endgroup\$
    – Ricardo
    Apr 25, 2014 at 12:24
  • \$\begingroup\$ @DaveTweed yep that is correct. i have updated the question. \$\endgroup\$
    – arjun
    Apr 26, 2014 at 10:26

1 Answer 1


For the very specific question there is a line in the datasheet with these values, specifying the bandwidth over which the measurement was made:

Total Harmonic Distortion Plus Noise THD+N f = 1kHz, BW = 22Hz to 22kHz, POUT = 22W 0.09 %

Dave Tweed is also correct that you need to at least specify input, output and portability before you can even start looking in the right category.

  • \$\begingroup\$ Thanks for pointing that out. As for deciding the specs, which i failed to mention, i was particularly referring to the next step. So if i further clarify, after i have decided the specs, what all does an experienced designer look for and how do they finally make the decision. \$\endgroup\$
    – arjun
    Apr 26, 2014 at 10:33

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