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quantran 5th May 2007 11:48 AM

Fast soft-recovery controlled avalanche rectifiers?
Is the above type of diodes good for audio equipment power supply?

I have some of these with part number BYD-33D made by Philips. I am thinking whether to use them for my DAC power supply.

continuous reverse voltage: 400V
average forward current: 1.3A
reverse current: 1uA
reverse recovery time: 250ns
diode capacitance: 20pF
maximum slope of reverse recovery current: 6A/ms

What are your opinions on these diodes?

AudioFreak 5th May 2007 01:52 PM

The current rating wouldn't be enough for most amplifiers. Maybe a preamp or something.

jan.didden 5th May 2007 02:47 PM

... but they would be OK for a DAC power supply.

Jan Didden

sandyK 5th May 2007 03:03 PM

Fast-soft recovery avalanche rectifiers
I think the ratings are probably more than adequate for the average DAC. The Musical Fidelity X-DAC V3 ,for example, uses a .5A "wallwart" How much current does your DAC draw ?

Personally , I would go for the UF4004 which has a 400V 1A rating and 50nS recovery time . This diode should be even quieter. They are less than AU$1 each. For most switchmode power supply bridge rectifier use (DVD players,Set Top Boxes etc.) the BYV26c is a great choice with it's 600V 1A rating and 30nS reverse recovery time. However the forward voltage drop is higher than the UF4004. The UF4007 is often used in these supplies because of it's 1,000V rating,but it is a little slower at 75nS.

AudioFreak 5th May 2007 04:01 PM


Originally posted by janneman
... but they would be OK for a DAC power supply.

Jan Didden

Thanks Jan. I guess I missed that part of the original post.

quantran 5th May 2007 04:31 PM

Thank all for your help.

I have very limited choices. I can't find UF400X at local shops.

BYV-95Cs may be available. I will try to look for these.

My DAC is still on paper. It's a bit complicated to calculate the current drawn. Briefly, it has three modules:

1. Digital consists of cs8414, one crystal oscillator a 4 glue logic ICs: powered by one LM317 and then one REG104-5
2. Main: 2xPCM63 powered by LM317, LM337 and then 4x TL431
3. Analog: Pass D1 clone powered by LM317 and LM337

Each module has separate transformer and rectifiers. I think 1A should be enough.

Beside those BYD-33D, I also have a bunch of RU1Ps diodes. These are rated 1000V/0.4A/100ns. I am afraid that 0.4A would not be enough These RU1P looks really hugh despite the 0.4A rating. They do not have soft recovery feature that the BYD-33Ds have.

It it safe to try these 0.4A diodes?

Conrad Hoffman 5th May 2007 05:16 PM

They should be fine (the first ones, not the .4A jobs). Put a small cap across each one, I usually use a small 0.1uF polyester, to kill any remaining RF. IMO, any power supply diode needs that. With any clocks off, sniff your power supply with an AM radio tuned between stations, to see if it's radiating anything.

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