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kevin gilmore

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kevin gilmore last won the day on April 26 2017

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About kevin gilmore

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    Staximus Maximus, Stax Mafia's Chief Cook and Bottle Washer

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  1. you can do up to 3 amps of class A bias with big enough heatsinks. The one feedback resistor, you can make into a resistor that is in series with a resistor that is in parallel with a cap. pick the numbers you want for appropriate bass boost. once in a while you get a bad transistor or low hfe etc, so always buy more than you need.
  2. so its a balanced amp with only unbalanced inputs. only 2 gain stages so its already low on voltage gain, and then if you put in 12bh7 as output tubes it has even less voltage gain. stax jacks with what looks like heatshrink on the pins? no 5.1k safety resistors, relying instead on the current source to limit output stage current. electrolytics not secured to anything. nice chassis.
  3. 4 x 5.1k resistors in series with all 4 outputs L+,L-.R+,R- changing the bias voltage to negative means that any dust that gets inside the headphones will accumulate on the diaphram. Definitely not what you want.
  4. if that is really MINUS 645 volts as the bias, bad things going to happen to the diaphrams. Flip directions of D3 and D6, change R10 to 5M
  5. no 5.1k series resistors on the outputs is a super bad idea. definitely bad for the headphones and a safety issue if the mosfets ever short.
  6. current version, front end at +/-35v power supplies, output section +/-24v from switcher, twice as many output transistors still need bass filter on the front end poweramp3a - CADCAM.ZIP poweramp3a.PDF
  7. the jumper was supposed to be .1 newest software loves to keep switching to metric (fixed) forgot about the size of the caps, can always put them on the bottom. i had thought that 18awg was enough. size increased to 60th not going to be able to move the caddock resistors much. only 25th. then runs into the output wire
  8. no it should not act like this. maybe it is oscillating in one mode. one person had a problem similar to this and fixed by adding 500pf B to C on the output transistor pair. Maybe the output transistors have changed over the years as i still have 100's of older ones.
  9. The feedback is crossed for SS on all but the very latest board which was posted somewhere in here and is not in the archive.
  10. r274x version of file but really you should find a manufacturer that does gerber x2 raalopamp - CADCAM.ZIP
  11. if they are just making boards from the gerbers, i'm fine with that. But the people taking the gerbers and then re-editing the hell out of them causing all sorts of issues (like taking all the values off the resistors) or making clone boards like the one above that require obsolete parts are just causing people trouble. find the gerber you want and have boards made.
  12. wired in series for +/-24v and then connected to each channel
  13. Gertrude sounds like a great name.
  14. I would think that a minimum of 50 watts of heat per channel seems reasonable. a dissipante 3U seems like it would work. probably 1 size down would also work if there is enough room for the switchers.
  15. Takes out the 6db bass boost filter.
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