X-PRO's modification foundamentally altered the circuitry: with that addition of that resistor, the mosfet output stage goes to current coupled.
the JLH1969 is a transistorized version of the Williamson tube amplifier, the first hi-fi amplifier we have. Because of the use of output tubes (actually driver tubesbecause the output stage in the Williamson is ac-coupled on the input and transformer coupled on the output), the Williamson tube amplifier's output stage is voltage coupled.
voltage-controlled transistors were not available when JLH implemented the Williamson amp with transistors in 1969. so the original JLH1969 was current-coupled.
I can only speculate that had MOSFETs been available in 1969, JLH might very well have implemented the MOSFET version in stead, .
here is the Williamson amp, and it looks identical to the JLH1969B or JLH1969M: V1 is the input tube, V2 is the phase splitter, driving a bootstrap network (C2/R6/R7). the driver tubes (V3/V4) take the output from V2's "collector" and "emitter", respectively.
most DVD players made in China output audio in 1.5 - 2v Vp, or 3 - 4v Vpp.
I think they believe in "louder sounds better".
haha... yes,it's out of standard...I think,they always make some incredible things...
they show that the chinese people's great creativity.
If you buy this DVD player---perhaps you need preamp no more...haha...
发表于 2009-3-17 17:23
楼主
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