Dual LM386 based amplifier

The LM386 is a low powered amplifier that is commonly used in portable music systems. The amplifier board is notable for two things: being tiny and being cheap. I purchased some of these several years ago and recently tested the amplifier by connecting them to a set of speakers.

Update July 25, 2021

Testing with the latest configuration was very satisfactory, with the amplifier playing very loudly and clearly from a CD converted from vinyl. The subscription based MP3 ( Hungama.com) files copied to disk, played through the DVD player was also acceptable, with some songs seeming to be better recordings than others.

The unit lacks structural integrity and finish, and a volume control is badly needed. Apart from that, the other features have worked well - crimped connectors, no soldering, and a dual AC DC input power supply arrangement.

Testing update 12 June 2021

The amplifier is all connected and hooked up to the Sony ES 333 speakers. Sound was just acceptable, with the EQ on the source device helping to tweak the sound. As of today, however, the sound quality has deteriorated considerably, running off 2 9V batteries. Sound levels are 80 db At 1 metre, however the batteries have since run down and read 6V each probably.

Testing

The LM 386 module (single module for the moment) was tested using speakers from a PC speaker mounted in open baffle format, and connected to a laptop computer. Within limits, sound was clear and detailed, with a hint of bass. Reducing the number of connections between the speakers and the module as well as making better power connections (using a 9V 330 mA AC/DC adapter) resulted in better sound all around. It is a good alternative to the in built PC speakers, and useful for listening.

Program material, or songs, are an important part of the system. I was able to download, legally, mp3 in 128 kb format from the Hungama streaming site, which offered 1 month free membership based on high past usage. The mp3 are of sufficient quality for my purposes, better than YouTube, and will always be available for use and to freely transfer to other systems, which is a huge advantage. I have dropped streaming listening for the moment, with its advertisements, expense and missing songs.

The module was supplied with a 9 V power input, and gain was turned down by a small amount as it was no doubt causing distortion. Power supply connections continued to be a problem, and I am not and will not be using any soldering at all in this project. Soldering is messy, results in the emission of toxic vapours, and also prevents many experimenters from doing good work. Mechanical connections and crimping (when it becomes available to me ) will be the way to go.

Testing with vintage Hi-Fi speakers

Testing with the large SONY ES-333 speaker surprised me, volume had to be turned up to 75% or more, but the sound was there: clear and with bass. The source material, compared to the tapes that I was used to for the songs I was listening to, was very good, and listening was an enjoyable experience. So much so that I am considering completing this amplifier as an alternative to the vintage amplifier already in existence (35 W per channel) and simply to enjoy the performance of an amplifier I put together myself. The vintage amplifier has some shortcomings due to its 30+ age and a definite crackle in its volume control, and some distortion at high levels, possibly due to the speaker cables, also very old.