If I put my notes here, I might be able to find them again later!
Another package in the mail...
Posted 14th January 2012 at 11:30 AM by rjm
The 47 Labs "Treasure" stereo amplifier kit model 0367 has just arrived here at RJM Audio central command.
61,500 yen delivered, a tad more than the model 0247 headphone amplifier / DAC. Basically lose the volume control and DAC board, gain a bigger transformer and a thick aluminum bottom plate that serves as the heatsink... the amplifier circuit itself is almost identical, just with a slightly bulked-up output stage and the addition of certain safety considerations such as fine tune-able bias current and thermal protection for the output transistors.
Which makes an unusual circuit for a power amplifier: the output stage is a unity gain current buffer running open loop. For a headphone amp that's justafiable because the bias current is such that the amp will almost always be running in class A. For a power amp rated 40 W into 4 ohms, it's class AB.
Mr. Tsukahara seems pretty pleased with the result though, and I am anxious to try it out.
61,500 yen delivered, a tad more than the model 0247 headphone amplifier / DAC. Basically lose the volume control and DAC board, gain a bigger transformer and a thick aluminum bottom plate that serves as the heatsink... the amplifier circuit itself is almost identical, just with a slightly bulked-up output stage and the addition of certain safety considerations such as fine tune-able bias current and thermal protection for the output transistors.
Which makes an unusual circuit for a power amplifier: the output stage is a unity gain current buffer running open loop. For a headphone amp that's justafiable because the bias current is such that the amp will almost always be running in class A. For a power amp rated 40 W into 4 ohms, it's class AB.
Mr. Tsukahara seems pretty pleased with the result though, and I am anxious to try it out.
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