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In Reply to: Re: Mo' tweaks for PP45 Man ... posted by Kurt Strain on May 14, 2002 at 07:59:13:
Actually, most any of the 6C*3 series work fine ... I picked the mojo 6CJ3's since the Amity is a pretty big amplifier in terms of overall current demand, and I was plenty annoyed at the sudden failures and buzzing noises from the 5R4-GY tubes. What an improvement!!! Much better dynamics, and astonishingly silent backgrounds. It wasn't until later that Matt Kamna discovered the damper-diodes have very low switch noise compared to other rectifiers. Reducing switch-noise from diodes is the probably the single most effective power-supply tweak ... much better than filtering after the fact, since 120Hz harmonics from switch-noise are also radiated into the air and back into the power-cord.Just some minor things to keep in mind ... these are single diodes, so you need a pair, they do consume a fair amount of current at 6.3V AC, it's wise to connect the cathodes to the heater windings to avoid any problems with H/K breakdown, and the sockets are a little weird, coming in Magnoval and Novar sizes (which are NOT cross-compatible with each other). However, in return, you get much larger peak currents than conventional tube rectifiers, and very low switch-noise, especially compared to solid-state. Plus, 30~60 second warmup as a free bonus. Yes, they *do* sound better, much more dynamic without the fizz and subtle hash of solid-state.
Having worked in Tektronix Spectrum Analyzers as a lowly tech writer for five years, I can tell you it's always preferable to reduce noise at the source rather than filter it afterward. Filters are not as effective as generally thought, when you consider ground-borne noise and direct emission into the air (which is NOT considered by the usual filter calculations).
Since the ratings in the GE Handbook (where you'll find most of damper diodes) are peak ratings, I typically derate by one-third or one-half, and still end up with lots of PIV and peak current capability ... and have had no failures to date, nor buzzing tubes, either. These things are silent.
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Follow Ups
- Re: Mo' tweaks for PP45 Man ... - Lynn Olson 05/14/0215:59:21 05/14/02 (0)
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