SS rectifier bypass higher frequency caps???

[GERPUD]

I'm back again with my Ramparte.
I'd like to know what is the purpose of C10, C11, C12, C13?

The voltage is 420V, it takes about 80W, the equivalent resistance is 2210R. These cap seems to make a high pass filter of the PT output letting higher fequency bypass the rectifier.
From:http://sim.okawa-denshi.jp/en/CRtool.php
Cut-off frequency fc = 9704.56970073[Hz]

So, why letting higher frequency from secondary PT pass directly through the B+, avoiding the rectifier?

If it doesn't help the tone, it's bad bad for the tone, and I'll remove them.

[R.G.]

They're not high frequency bypass caps. They're there to suppress possible RF ringing caused by the diodes' sudden turn-off characteristics. It's a simplistic kind of snubber.

This has been identified as a cause for a kind of buzzy hum in some circumstances.

[GERPUD]

They're there to suppress possible RF ringing caused by the diodes' sudden turn-off characteristics. It's a simplistic kind of snubber. .

Ok thanks, I'll try to read more on snubber...

[John_P_WI]

Just us FREDs, ultra fast recovery diodes, UF4007. You won't need the caps.

[GERPUD]

Correct me if I'm wrong:
From my reading and from your replys, theses caps are not exactly snubber because snubber would need resistors in parallel to the caps.
In the bridge, the diode turn-off creates high frequency that may get into resonance. The cap don't eliminate the frequency, but lower it so it won't be into resonance.
I guess that this lower frequency may be audible and may add some noise.
Since I've added a choke, I guess it is taking care of those high frequency so I won't have any benefit of using FRED or removing theses caps.
Correct?

[pdf64]

Since I've added a choke, I guess it is taking care of those high frequency so I won't have any benefit of using FRED or removing theses caps.
Correct?

Not really, rather the issue with the switching resonance is that it creates EMI buzz throughout the amp.
It's not thought to be transmitted via the B+ string.

[R.G.]

PDF is correct. The RF resonance is in the inductance and capacitance of the wires attached to the diodes, and is thought to be transmitted by those same "antennas" into the electronics right next to them.

And you are correct to a first order in that parallel caps do not so much suppress the RF as to lower the energy put into the resonances by slowing down the rate of change of the current that makes them ring, and that a true snubber would incorporate a resistor, although in this case it would be a series R and C.

There are two ways to attack this issue by current (i.e. today's) thinking. These are to lower the energy in the turn off pulses by using fast and soft-turn-off diodes, of which the Fast Recovery Epitaxial Diode type is the prototype, or by using R-C snubbers on normal diodes.

Both ways work, although the FRED is easier for the beginner, as the RC snubber networks tend to need tuning to the specific wires and arrangement attached to each diode lead to get the best snubbing. The FREDs work by putting less energy into the resonances to start with, the snubbers by eating up the energy in a resistor to keep it out of the resonances.

[GERPUD]

Theses caps are pretty technical...
How you guy know all theses things!!
How can I know if I have RF problem?
If I don't have any problem, replacing the diodes with FRED would be like giving clear eyes drop to a fish...