The KBPC will work fine, and is by far the easiest to install.
The Universal PSU diodes will be faster.
HEXFRED diodes will be faster and softer.
If you have a Quasimodo and calculated the snubber values for the Universal PSU and installed them, then that's probably as good as using HEXFREDs.
For me personally, the middle ground doesn't make much sense. If nothing more than a CRC or CLC follows the rectifier I'll often go full-boat with HEXFREDs and snubbers. If I'm using a c-multiplier or regulator then the simple approach has the upper hand.
Can you hear the differences? I haven't the foggiest.
The Universal PSU diodes will be faster.
HEXFRED diodes will be faster and softer.
If you have a Quasimodo and calculated the snubber values for the Universal PSU and installed them, then that's probably as good as using HEXFREDs.
For me personally, the middle ground doesn't make much sense. If nothing more than a CRC or CLC follows the rectifier I'll often go full-boat with HEXFREDs and snubbers. If I'm using a c-multiplier or regulator then the simple approach has the upper hand.
Can you hear the differences? I haven't the foggiest.
The way a rectifier works is that the diodes turn on and off alternately so that each caries 1/2 the AC waveform to either the positive or negative rail. They don't do this instantly, so they leave ripple.
Diodes overshoot when they turn off. "Fast" means the overshoot lasts for a shorter time; "soft" means the overshoot is more rounded. For pictures and more words, see: Fast, Ultrafast, Standard, Soft, Schottky: What’s the Right Rectifier for Your Power Circuitry?.
The overshoot makes your transformer ring. It's like striking a bell. Quasimodo (the bell striker in The Hunchback of Notre-Dame) is a circuit one of our fellow contributors designed which allows you to measure the frequency of the ringing and select snubbers to dampen it out. The less overshoot (and the rounder the overshoot) the less ringing you have and the less need for the snubbers.
Ringing also introduces ripple on to your rails, although at a much higher frequency and for a much shorter time.
A CRC filter is a capacitor followed by a resistor followed by a capacitor. The Universal PSU uses a CRC filter. The function is to decrease the ripple.
A CLC filter is similar, but uses an inductor in the middle instead of a resistor. It's also used to decrease ripple.
A regulated PSU has active circuitry to stabilise the voltage to a particular level. Since ripple is a minor fluctuation in the voltage, it also reduces ripple (usually dramatically).
I don't know the M2, but it sounds like it has what's called a high PSRR. That stands for Power Supply Rejection Ratio, and what it describes is the circuit's degree of immunity to ripple.
So a KBPC and a CRC filter is probably all you need. But as long as you already have the diode portion of the Universal PSU boards stuffed, go ahead and use those. They will perform slightly better than a KBPC.
Cheers,
Jeff.
Diodes overshoot when they turn off. "Fast" means the overshoot lasts for a shorter time; "soft" means the overshoot is more rounded. For pictures and more words, see: Fast, Ultrafast, Standard, Soft, Schottky: What’s the Right Rectifier for Your Power Circuitry?.
The overshoot makes your transformer ring. It's like striking a bell. Quasimodo (the bell striker in The Hunchback of Notre-Dame) is a circuit one of our fellow contributors designed which allows you to measure the frequency of the ringing and select snubbers to dampen it out. The less overshoot (and the rounder the overshoot) the less ringing you have and the less need for the snubbers.
Ringing also introduces ripple on to your rails, although at a much higher frequency and for a much shorter time.
A CRC filter is a capacitor followed by a resistor followed by a capacitor. The Universal PSU uses a CRC filter. The function is to decrease the ripple.
A CLC filter is similar, but uses an inductor in the middle instead of a resistor. It's also used to decrease ripple.
A regulated PSU has active circuitry to stabilise the voltage to a particular level. Since ripple is a minor fluctuation in the voltage, it also reduces ripple (usually dramatically).
I don't know the M2, but it sounds like it has what's called a high PSRR. That stands for Power Supply Rejection Ratio, and what it describes is the circuit's degree of immunity to ripple.
So a KBPC and a CRC filter is probably all you need. But as long as you already have the diode portion of the Universal PSU boards stuffed, go ahead and use those. They will perform slightly better than a KBPC.
Cheers,
Jeff.
WOW! Thank you for those detailed descriptions. It almost feels like I understand. 
Really - are you an electronics instructor? If not, maybe a career change is in order.
For right now, I will try the unit as is with the PSU diodes and no snubber/optional additions. If there is room in the chassis, I will install the KBPC5010 50A 1000V monolithic Bridge Rectifier Diodes and listen to both. Once I have convinced myself that my old ears can hear a difference, I will ask someone else to give their opinion and post that!
Really - are you an electronics instructor? If not, maybe a career change is in order.For right now, I will try the unit as is with the PSU diodes and no snubber/optional additions. If there is room in the chassis, I will install the KBPC5010 50A 1000V monolithic Bridge Rectifier Diodes and listen to both. Once I have convinced myself that my old ears can hear a difference, I will ask someone else to give their opinion and post that!
Thanks for the response.
The question is about resistor wattage rather than the value of the resistor.
With 22V transformer secondaries, I though the rectified voltage rail under load will be close to 28V.
Even if the rails were 22V, with a 2.2K resistor, the power is ~ 0.43V
So why is 3W recommended ? Is this for transients ?
I think this is from the BOM, I did not know what are "low and high" voltage ranges for this resistor range.
R9
Bleeder Resistor
4.7K - 22K
3W
Flame-proof resistor recommended
Use higher resistance values for high voltage outputs
The question is about resistor wattage rather than the value of the resistor.
With 22V transformer secondaries, I though the rectified voltage rail under load will be close to 28V.
Even if the rails were 22V, with a 2.2K resistor, the power is ~ 0.43V
So why is 3W recommended ? Is this for transients ?
I think this is from the BOM, I did not know what are "low and high" voltage ranges for this resistor range.
R9
Bleeder Resistor
4.7K - 22K
3W
Flame-proof resistor recommended
Use higher resistance values for high voltage outputs
@bajjisw, a lot of this comes from the fact that Nelson buys in bulk and uses what he has. So his designs by and large only use 1/4 watt and 3 watt resistors. (As your calculation shows, a 1/4 watt won't work here. Not also that when he needs more than 3 watts, he tends to parallel multiple 3 watters.)
Hello,
Working on the chassis wiring for an M2X using the PSU v3. Running into some uncertainties.... trying to decipher all the info and correlate w/ pics..
Starting with The diyAudio First Watt M2x post #1162. I see a brown cube connecting toroidal to extension? wires leading to terminal block. What is that brown cube[called]? just a safe way to connect the group of wires?
The terminal block setup is unclear to me after reading the nice article at Building a Gainclone chip amp power supply.. On the 115/120V side of the toroidal, I have four wires (2xblack, 2xred) and understood those should be paired by color (R+R and B+B) and wired to the same colors coming from the power entry module. The picture from 6L6 looks like it shows Red & Black coming in to terminal block and jumpered over to another pair of terminal posts using CL-60 capacitors? Then on the opposite side the transformer wires enter. I am not clear if that is correct and if I should follow? Also, very confused by the little blue capacitor? on the transformer side of the terminal block. It looks like it is wired to span the two center posts spanning the hot and neutral?
Lastly (for now) the toroidal I have shows a purple 'shield' wire and I am not sure how that is to be wired. It is not described anywhere I can find. Is that simply a ground I should wire to the chassis baseplate?
Thanks
Working on the chassis wiring for an M2X using the PSU v3. Running into some uncertainties.... trying to decipher all the info and correlate w/ pics..
Starting with The diyAudio First Watt M2x post #1162. I see a brown cube connecting toroidal to extension? wires leading to terminal block. What is that brown cube[called]? just a safe way to connect the group of wires?
The terminal block setup is unclear to me after reading the nice article at Building a Gainclone chip amp power supply.. On the 115/120V side of the toroidal, I have four wires (2xblack, 2xred) and understood those should be paired by color (R+R and B+B) and wired to the same colors coming from the power entry module. The picture from 6L6 looks like it shows Red & Black coming in to terminal block and jumpered over to another pair of terminal posts using CL-60 capacitors? Then on the opposite side the transformer wires enter. I am not clear if that is correct and if I should follow? Also, very confused by the little blue capacitor? on the transformer side of the terminal block. It looks like it is wired to span the two center posts spanning the hot and neutral?
Lastly (for now) the toroidal I have shows a purple 'shield' wire and I am not sure how that is to be wired. It is not described anywhere I can find. Is that simply a ground I should wire to the chassis baseplate?
Thanks
The purple shield wire goes to the chassis.
For the wiring with the blue capacitor and the CL60 thermistors, it follows
the 120V wiring for the standard FW poser supply. (For example p.16 here
http://www.firstwatt.com/pdf/prod_f4_man.pdf )
Please see also posts #1062 :
https://www.diyaudio.com/forums/pass-labs/188691-illustrated-guide-building-f5-107.html#post5581469
For the wiring with the blue capacitor and the CL60 thermistors, it follows
the 120V wiring for the standard FW poser supply. (For example p.16 here
http://www.firstwatt.com/pdf/prod_f4_man.pdf )
Please see also posts #1062 :
https://www.diyaudio.com/forums/pass-labs/188691-illustrated-guide-building-f5-107.html#post5581469
That's just a clip on ferrite clamp that I had. Filters a bit of RF noise, not much else. Don't worry about it.
Thermistors
This is the image Dennis linked to in the post above -
The important thing to understand in this photo is Red 1 and Black 2 is the first primary winding (They will have continuity to each other if you use your meter's beep mode) and Red 3 Black 4 is the second primary winding, they will also have continuity to each other.
Yes. 3300pF, X1/Y1 rated for across the (mains) line use
Yes. Attach to chassis
Super thanks for the help everyone - your support is appreciated.
I noticed on the PSU schematic that R9 & R10 show 2.2 Kohms/3W while on BOM they are listed as R9/R10 Bleeder Resistor 4.7K-22K 3W Flame-proof resistor recommended Use higher resistance values for high voltage outputs with recommended part# = P22KW-3BK-ND which is 22Kohm - not 2.2K. Am I missing something here or is this a discrepancy?
I noticed on the PSU schematic that R9 & R10 show 2.2 Kohms/3W while on BOM they are listed as R9/R10 Bleeder Resistor 4.7K-22K 3W Flame-proof resistor recommended Use higher resistance values for high voltage outputs with recommended part# = P22KW-3BK-ND which is 22Kohm - not 2.2K. Am I missing something here or is this a discrepancy?