Rectifier Tube
- Thread starter canton
- Start date
sKiZo
Hates received: 92644 43.20°N 85.50°W
Ah ... the version with delay must be a fairly new addition to the lineup ... probably due to us hifi nutz' incessant whining ... ;-}
Dude, I know that. The point is that adding a defect to a HiFi amplifier is not a good idea. Guitar, fer sure. But who wants sag in HiFi?
sKiZo
Hates received: 92644 43.20°N 85.50°W
Sag may be a good thing in hifi, acting as sort of a low tech protection system. Not really a factor for "normal" listening levels, but I'd think dropping the plate voltage on the power tubes at industrial style peaks when you're really cranking it would tend to reduce the severity of a clip ...
The sag does not magically kick in at clipping; instead, as current increases voltage decreases. It is a continual process of distortion. Different if you want the guitar amplifier to begin to distort during power chords...
It requires a significant re-design of the supply to maintain voltages but eliminate the impedance. There also gets into questions about the ability of the transformer to deal with the extra current load that not having that resistance implies. If you're designing new you can account for that, re-fitting an existing amp can be somewhat more complex and beyond the scope of a typical restoration to original operating condition.
A low-noise voltage regulator is doable, as other projects here have shown. But, yes, it does require a re-design of the supply. No more of the CLC or LC simplicity.
The current, however, should not increase without additional draw from the circuit; only the voltage rises because the tube no longer reduces voltage during rectification. Voltage drop is voltage drop, so it either occurs in the tube or in a resistor, but neither loads the transformer any more, and the electrons still make the same circuit path as before.
The current, however, should not increase without additional draw from the circuit; only the voltage rises because the tube no longer reduces voltage during rectification. Voltage drop is voltage drop, so it either occurs in the tube or in a resistor, but neither loads the transformer any more, and the electrons still make the same circuit path as before.
peak current demand on the transformer will increase since there won't be a chunk of impedance between the output of the rectifier and the first filter cap if there is no resistor or vacuum rectifier in the mix. I don't know how much it really matters but whats this place for if not to have endless discussions about what matters and how much? 
Sure, the capacitor charges at whatever maximum current it can draw, and that's a function of its size. (Conduction angle.)
But the dropping resistor acts as a limiter, and then the impedance remains constant. Rectifier tube or dropping resistor following a solid-state rectifier, doesn't matter where the impedance or current limiting comes from. Putting the resistor after the filtering means the capacitors must take increased voltage, which likely isn't an issue. Given the abuse meted out to power transformers, it likely wouldn't matter where the resistor is placed. (Although the Heathkit W5 family Williamsons tended to eat power transformers.)
You know the apocryphal story about what was being discussed the day Byzantium fell? Yeah, that.
Bill Ferris
Lunatic Member
Yes, who in deed Retrovert.
Been ripping out the FP style chassis mounted cap cooker rectumfryers for decades, and my Macs, and Mk III`s haven`t failed or complained yet, of course they had been recapped by me, and Thermistor upgraded, with chokes installed in the MC 30`s instead of the 150 ohm 7 watt B+ dropping resistors, and all exceed factory specs.
"Sound reproducing"Tube amps can have enough "sponge" without tube rectifiers in the path wastefully converting AC to pulsating DC.
All SS rectification converted amp`s power transformers are thermally happier too, without that unnecessary 5 volt filament multi ampere heating current draw on the power transformer..
Started SS rectification upgrading customers, and my Dynaco`s and Mac`s, ect. in the mid seventies, and haven`t looked back.
Too each their own, as you see fit..
Kind regards, Bill Ferris
All hail the choke-input supply, with its wide conduction angle and stellar performance.
