In Reply to: Re: What's going on in Pi world, eh? posted by replay on December 07, 2002 at 21:19:00:
I've based my work on that of Steve Bench because he has extensive hands-on experience with tubes and tube designs. I am designing the filters that precede the 6DJ8 and that's really all there is to the circuit. It's two sections of a 6DJ8 tube, so two tubes are needed for stereo, and then the filter and that's basically it. There's a coupling cap on both sides, which is then really an additional VLF high-pass filter, and then there's the crossover filter and compensation circuit. It's so simple, it almost has the same low parts count of the passive crossover.The slope for each section can be made first, second or third order and the crossover point is selectable. But that's done by picking components, not by placing jumpers, or setting switches or potentiometers. One of the things that prompted the choice to use an existing design is that there is a circuit board already available which has plate-through holes for additional parts - Hopefully enough for the components needed for the π compensation circuit. I've discussed this matter with Steve, and he believes that this can be accomplished without "hacking" the circuit board.
I've always hated etch cuts, jumpers and "floating" components, but it's attractive to be able to use an existing board as long as a lot of etch modifications aren't required. If extensive cuts are required and I then I may decide to have board etched instead. We'll see how much response there is.
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