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SL414 Vintage power amplifier IC

SL414 is combined audio preamplifier and power amplifier IC manufactured by National semiconductors in early days. This amplifier is designed to operate in 10V to a 20V range and deliver 3W (R.M.S) audio output power into the 7.5Ω load. The frequency bandwidth of this IC is between 30Hz to 18kHz and with the 8Ω load, it produces 0.5% T.H.D on 3W.

The most uncommon feature of this IC is its EP-10 package. This EP-10 package is common to most of the SL4xx series amplifiers and thanks to its inbuilt screw it is really easy to attach heat-sinks to these ICs.

EP-10 package of SL414 audio amplifier IC.

During our prototyping, we try several SL414 amplifiers and most of them give quite satisfactory results to us. Link to most stable SL414 design is available at the bottom of this article. As per our experiments, to archive best results it is mandatory to build this amplifier on PCB with screened wires. Also to get the good results to make sure to drive this amplifier with a regulated DC power supply. In our tests, we use an LM317 base PSU to drive this amplifier.

SL414 Amplifier prototype.

SL414 is quite hard to find and no longer manufactured by National (now TI). For those who having SL414’s can try our design/ PCB which is available at google drive.

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