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Aug 18, 2016, 12:19 PM
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Death of the Yamaha


Over the years, the plan varied from reworking the Yamaha's parts into a discrete 2 channel amplifier to nihilistic plans for tubes. In the end, the future was the most economical bog standard IC amplifier. A quick test of the broken DM-01 revealed it probably failed from broken solder joints. 20 years of hindsight would have saved a lot of money, because what was succeeded by 3 amplifiers which failed in their own ways & a lot of heartache would again become the standard.

Unfortunately, the DM-01 electronics were discarded long ago & the speaker driver failed for an unknown reason. Perhaps someone put 12V directly through it. Whoever discarded the electronics strangely left behind the heart of the DM-01: manely the LA4461. The LA4461 is a long discontinued single channel IC with a lot more external components than a modern part, but the nastiest bits of the LA4461 were all preserved on its carrier board. Datasheets 30 years ago were a lot harder to read.

The mane piece not on the carrier board was an oscillation suppression circuit. The test seemed to work fine without the oscillation suppression circuit. The LA4461 produced plenty of loudness from the phone with no additional gain. The only other piece in the discarded section was the tone control. This seemed to be a standard op-amp circuit which combined volume with bass boost. It could be reverse engineered, but the mane requirement in old age is treble boost. The rest was all power supply.

The future would keep the LA4461's on their original heat sinks. A perf board would contain the DAC, volume control, & maybe tone control. The mane unknown is the volume range of the DAC. There hasn't been a need for analog input in years. For the power supply, true believers use toroid transformers, but it would be another laptop power supply with LM317.
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