Anyone using Silicon Carbide rectifiers?

[TUBEDUDE]

Silicon Carbide has extremely fast switching. With a short trr, these are supposedly faster and cleaner than even Hexfreds. If you use these rectifiers, do you use any added resistance, and have you noticed a change in the rectifier spikes amplitude?

[TUBEDUDE]

Buehler...

[Stevem]

Since we are dealing with only 50 to 60 cycles and not radio frequency there very quickly comes a point where how fast a diode can switch is of no benefit, only the resultant swtiching noise it produces should be concidered.

For non full frequency high end audio / recording / Hi Fi use where super low noise floors are needed a 58 series fast diode with a cheap .01 uf 1000 V disc across it is all that needed for a guitar amp!

[roberto]

We were talking about it on an italian forum and an user who switched to this technology is supposed to perform some measurements during winter vacations.
I've not tried yet, but his report is that you can avoid caps to dampen the switching noise of standard diodes, so it is a plus even on guitar amps.
I will report here any further technical data he will report.

[TUBEDUDE]

The short high current charging spikes are more problematic than 60 Hz sine waves. Lots of high frequency energy.

[R.G.]

My understanding is that it's not so much the turn off spikes, it's the ringing in the parasitic inductance/capacitance in the diode wiring that gets into your audio. This turns a spike that happens every 1/50 or 1/60 second into a squark of RF that is much easier to get into the audio path as it's longer duration and can more easily heterodyne with audio to an audio artifact.

Capacitors across diodes may help diode turnoff noise but they primarily lower the height and stretch out the time of the snap-off current transition of conventional diodes, which makes it somewhat harder to excite ringing in the wiring. Even better than just a cap is an RC snubber. The cap stretches the turn off impulse and the resistor eats the energy. A properly matched RC snubber can make a conventional diode very quiet. Sadly, the math for tuning the snubber is dependent on the ring frequency of the wiring, so there' s generally only an approximate fit and not much of a one-size-fits-all.

HEXFREDs and SiC diodes attack the problem by not generating such a spike on turning off. So they're light on calculation, but heavier on initial cost.