Sony XF-5000 and XF-500 Transound Stereo

Sony's "Transound Stereo" series was sold in 1981. It was a very expensive portable component system featuring a rechargeable battery and heavy metal construction on both the amplifier as well as the optional speakers. There was also an optional handle that could join them all together via the metal studs on top.

What's confusing is, the "Transound" name was also used on several of Sony's cheap plastic boomboxes. But none of them had power like this: 40 watts per channel minimum, from 40 to 12,500 Hz into 4 Ohms, with no more than 2% total harmonic distortion. That's home hifi territory. In comparison, the vast majority of traditional 1-piece plastic boomboxes only had 1 to 15 watts per channel.

The amplifier uses a technology called "Pulse Width Modulation", which I don't really understand, but it supposedly makes it more efficient, thus increasing the battery life.

Available models:

• XF-5000 (the top of the line model with a digital tuner)
• XF-500 (a less-expensive model with a 9-band graphic EQ instead of a tuner)
• XS-50 speakers (12cm woofers, 5cm tweeters, 89dB/w/m)