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Low Hy? How about no Hy?

In a very comprehensive and detailed article, published in Japan in 1999 and reproduced in Glass Audio the following year, Satoru Kobayahi described a 300B SE stereo amp that uses Plitron toroidal OP and power transformers.

I was interested to see that he used a power MOSFET series regulator in place of the smoothing choke in what would have been a conventional CLC pi-filter.

Essentially, his PS consisted of: toroidal power transformer - SS bridge - 100uF smoothing cap - MOSFET series regulator - 100uF reservoir cap.

For regulation, he had well-bypassed stacked zeners (3 x 150 v) from the MOSFET gate to ground. According to the test voltages written on his schematic, he dropped 33 v across the MOSFET.

His initial objective, in replacing a choke with a MOSFET, was to save money and reduce weight. However, he also reported that the ripple was much less than he could have achieved with a 10H choke. In view of Satoru-san's reputation as a designer and builder, I'm inclined to think that if it's good enough for him then it's good enough for me!




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Topic - Low Hy? How about no Hy? - Ray Moth 16:16:00 05/05/07 (45)

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