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curious about xener diodes to lower B+

Discussion in 'Amp Tech Center' started by texwest, Sep 24, 2020.

  1. elpico

    elpico Tele-Afflicted

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    That's quite normal variation. It's not something that should cause audible problems or need to be corrected if it's centered around the voltage your amp wants to be fed. The higher budget power conditioners do have voltage regulators built in, but their performance target is usually +/- 5V so you're already doing pretty good.
     
  2. trobbins

    trobbins TDPRI Member

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    I'd recommend some caution when deciding what type of zener part to use, if a zener was the chosen technique.

    Being a solid-state device, a zener is very susceptible to failure if its junction temperature approaches its max allowable rating. That type of failure is typically managed by derating, however there are a number of practical derating considerations that should be applied, so the selection process can get a bit complex. Reasonable power dissipation derating levels are about 65% to bring the max junction temp down below its rated max, and another 60% to operate the part in an elevated ambient (such as under a valve amp chassis). Another derating is recommended if the zener is in the CT link where it would experience relatively high peak current pulse levels (as compared to placing the zener in the B+ feed and after the main filter cap, where it would experience a more continuous current level). Even more derating should be considered if the maximum rms current that the zener will pass is not adequately known by way of an rms meter measurement when thrashing the amp.

    The indicated deratings could easily mean a 10V 5W rated zener should not be used where rms current exceeds say 160mA, and even that would rely on any zener part being soldered to metal tabs that have substantial area and mass to keep the tab cool (ie. a heatsinking capability, and not heated by other parts such as zener diodes), and the CT link rms current being measured or well defined.
     
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