BYM26C soft recovery high speed diodes - diyAudio
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Old 13th September 2007, 09:19 PM   #1
hihopes is offline hihopes  South Africa
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Default BYM26C soft recovery high speed diodes

Anyone used Phillips BYM26C diodes before? Specs look really good to me (but what do I know?) At 30nS, they appear to be 40% faster than MUR860, AND they are soft recovery too! I know they are only rated @ 2.3 A, but I don't think that will be a problem for me, as I am thinking of using them for a bridge in an Aikido preamp PSU. The reason I am asking about this particular one is that it shows up in a local supplier's catalogue.
I see they (Phillips) call this a fast soft recovery controlled avalanche rectifier. Quite a mouthful! I don't understand exactly what that means, so I hope it doesn't mean they are unsuitable for my needs.
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Old 15th September 2007, 08:45 PM   #2
hihopes is offline hihopes  South Africa
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What? No comments? They aren't that expensive, so I guess I will try some out.
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Old 15th September 2007, 09:24 PM   #3
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Don't know about that one, but I use BYD73B sometimes because I have a lot of 'em. It's a 25nS part, which is probably absurd overkill and a waste of a high speed part. IMO, regardless of what you use, each diode needs to be bypassed to avoid genrating RF.
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Old 16th September 2007, 10:30 AM   #4
AndrewT is offline AndrewT  Scotland
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Hi Conrad,
bypassing with a C alone or an R+C across each diode?
What type of C? ceramic, polypropylene, polyanything, or does not matter?
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Old 16th September 2007, 10:56 AM   #5
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What's the difference between ultrafast diode (like MUR820) and ultrafast soft recovery (like FFPF06U20S)? Fairchild one is "soft recovery", what the difference with other ultrafast rectifiers.

Is schottky still better than "ultrafast soft-recovery"? I can get MUR820, FFPF06U20S and 90V schottky here (enough for +/-35V rectification, I guess), which one is better for audio gear rectifier?
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Old 16th September 2007, 02:27 PM   #6
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I want something self healing, so a small metallized film of no bigger than 0.1uF works fine. IMO, a full blown snubber circuit is overkill. Hint- find a small AM radio and tune it to between stations. Hold the antenna near your operating bridge. Don't short it out! If you hear an increase in noise near the bridge (or any other part of your audio equipment), it's time for some bypassing. There's probably a difference in the amount and frequency of junk generated by various types of diodes, but I don't know the specifics. I do find faster is better than slower, even on 60hz circuits.
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Old 16th September 2007, 08:58 PM   #7
hihopes is offline hihopes  South Africa
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A full blown snubber circuit? Just 1 resistor added to your film cap. I will always go that extra inch, no matter what diodes I am using.

Actually, I started out using good old 1n4007's, even in bridges for 15v PSU's. Then someone said try MUR 860 - everybody says they are so good , so fast etc. Well, my experience was that the when both were snubbed, the 1n4007's seemed to sound better (at least to my ears.) Maybe the fast switching creates a hectic spray of higher harmonics that are more difficult to get rid of? Anyone had similar experience?
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Old 16th September 2007, 09:01 PM   #8
hihopes is offline hihopes  South Africa
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BTW Conrad, have you listened to pure polyprop film vs metallized snubber caps? I am "allergic" to the sound of metallized caps to the point where I have been unwilling to try them, even for snubbing.
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Old 16th September 2007, 09:10 PM   #9
hihopes is offline hihopes  South Africa
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Hi Lumanauw,
I don't have enough experience to answer your question with certainty. From what I have read, soft recovery may be even more advantageous than high speed, but why not get both properties in one diode? As for comparisons to Schottky, I think there are probably a lot of people who would like to know the answer to that one! Wouldn't you like to be a "test pilot" and give us all a report back on that comparison?
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Old 17th September 2007, 12:39 AM   #10
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Do the radio trick. If the diodes are generating anything, it will probably be at a frequency where the radio can easily pick it up, and that's a lot more sensitive than a scope- microvolts instead of millivolts. Then, if you're like me, you'll run about the house checking for RF from everything else. My humidifier turned out to be a terrible generator until I added an LC filter to the motor speed control. A snubber can be more than a single resistor, but in this case I don't know if even a resistor is needed. You should probably just ignore the next part, but IMHO if you can hear the effect of this sort of ps mod, other than killing off RF, which I believe can be audible, there is something fundamentally wrong with either the circuitry or the grounding scheme. The type of cap used on the diodes, and even the type of diodes themselves, shouldn't be audible. Not even to bats or dogs, who hear way better than we do. I wouldn't be quite so negative, but I just did some tests of various supply changes and found their audibility is mostly self created illusion. Anyway, I'll go for the self healing metallized part, because it could save the rest of the power supply in the event of failure. Admittedly diodes fail too, but why add to the risk? If you were working on the input side of the fuse, say for a line filter, nothing else would be acceptable. In this case you have a bit more freedom.
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