High power diodes any good?

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Diodes Inc as stocked by farnell, digikey, mouser, probably RS etc, have anything you could want. People have said fast recovery diodes make more 120 hz noise than the regular ones. I use regular recovery diodes followed by a .01 uf across the electrolytic cap and I don't have 120 hz noise. But for my 6.5 a amp transformer, the diodes have to be 6 amp rated.
 
Back in the day they just used a 500 volt .01uF Z5U or similar disc right across the rectifier on the AC side. No need to put a separate resistor if the cap is lossy.

Faster rectifiers will reduce the amount of stored energy, but can push the offending harmonics up higher in frequency where they might actually be harder to remove.

And regular old 60 Hz diodes can withstand the whallop of charging a couple of 20000 uF soup cans thru a toroid. The power switch may not like it, but the rectifier will take it. Ultrafast diodes require a soft start, and a lot more attention paid to surge ratings. I’ve blown pieces of TO247 rectifiers across the room before. The only 35 amp conventional rectifier I’ve ever smoked was trying to start a car with it. It took 5 or 6 seconds of trying to crank to let the magic smoke out.
 
You want high power diodes.
You have 6 of them in your car alternator ( 3 negative and 3 positive) . They are perfectly good for audio in a power supply.
They are already broken in for audio. Their sonic signature depends of the roads the car was driven. In case you have the sound of the sea, they were from a boat.
 
Just because it is labeled “fast” doesn’t describe how the shot effect will be, that’s the recovery that determines that. Those parts shown have the same recovery time as regular diodes.

That’s very interesting about the exploding diodes from the surge, never imagined they would do that. Also good point about the lossy caps, but all the ones I have seen like that and replaced worked better with the extra components( I splurged). Maybe mine had different ceramic caps or something.
 
You want high power diodes.
You have 6 of them in your car alternator ( 3 negative and 3 positive) . They are perfectly good for audio in a power supply.
.

The diodes in a car alternator might only be a 50 or 100 volt rating. 100 amps maybe, but it is a 14.4 volt system and lower voltage rated diodes in any given series have lower forward voltage drop. At 14 volts every tenth counts, So there is some justification to use the lowest voltage possible in the alternator.

But perfect for running an LM3886 off a 1kVA toroid (which is what you need if you want 3% regulation).
 
Standard I'm using hfa25pb60 fast soft recovery diodes.

The diodes from datasheet below are mentioning the same. Would these be any good for class AB amp's? Any reason why not to use them?

https://www.promelec.ru/pdf/UFB200FA20P.pdf


That one is up to your standard. But my standard is higher :D. In general (tho it depends on brand and model), smaller diodes (current rating) have better specifications for audio than its bigger siblings (Some Japanese products used axial diodes with heatsink). And we can even increase the performance further by lowering the current going through them by using dual bridge with dual secondaries.
 
Benson has only described his application as class AB - that could be a 100mW headphone amplifier, or a huge stadium amplifier. I'd second guess its more likely a 100mW amp, as many people seem to think that 25A rated diodes must be better, especially if their 600V rating is similarly better for a 40V application, and if they cost orders of magnitude more than any mundane diode found in most amps.

I just hope they come with a sticker to apply to the front of the amp - so you don't forget you put something extra special in - that would be a reason to use them (as opposed to a reason not to use them, which I think was the original query).
 
That one is up to your standard. But my standard is higher :D. In general (tho it depends on brand and model), smaller diodes (current rating) have better specifications for audio than its bigger siblings (Some Japanese products used axial diodes with heatsink). And we can even increase the performance further by lowering the current going through them by using dual bridge with dual secondaries.

Thanks for the feedback.

The diodes are used in a dual bridge configuration with a dual secondaries 1kva 2x36Vac toroid. Load is 2x22000uf 63v low ESR vishay caps /rail, with screw connections for a class Ab power amp which can deliver 12Wrms into 8ohm classe A.
 
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