Schottky vs ultrafast recovery diodes in DHT power supply - diyAudio
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Old 3rd December 2014, 10:30 AM   #1
hugenh is offline hugenh  Norway
diyAudio Member
Join Date: Apr 2012
Location: Oslo, Norway
Default Schottky vs ultrafast recovery diodes in DHT power supply


i am to design a powersuply for a small DHT headphone amp (details to be posted soon). All things considered i find both suitable Schottky and ultrafast rec. diodes (10-15ns) meeting my specs. Price is not too different too.

So which to choose for HV / heating? I don't mind loosing up to 2V in Vf, it`s audio quality i am interrested in.

Please, forumites can you supply some facts on which type would bw superiour? Facts please if you have, well argued opinion is ok to. But please no ranting, yawn, yawn.... seen that so many times before ;-)

Greetings, Harry
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Old 3rd December 2014, 10:50 AM   #2
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Join Date: Mar 2002
Location: Glasgow
I would use Schottky diodes for the heater supply and ultrafast ones for the HV.

Schottkys have lower forward voltage drop than regular diodes, so they are great for efficiently rectifying high currents at low voltages. They also have practically no reverse recovery issues, the recovery time is theoretically zero. So if you believe (as many do) that recovery transients from diodes spoil the sound quality, you might prefer the Schottkys.

The downside is that they are only available in low PIV ratings, you won't find any suitable for a tube amp HV supply. Except maybe for the new silicon carbide Schottkys.
"Sadly, audio is like that. It is about the only branch of electronic engineering where lack of knowledge is regarded as a more advanced form of wisdom."
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Old 3rd December 2014, 11:28 AM   #3
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Join Date: Feb 2005
Location: Melbourne
As usual, it depends on ...!

As Steve mentioned above, the Schottky's have limited voltage capability so you don't really have a lot of choice here and the Cree ones have their own signature too (Sil Carb)

For a DHT headphone amp, I would be looking for just the opposite to the Ultrafast diodes and be looking at the specific Soft Recovery ones, or probably even consider valve rectifiers - are you using the Coleman regulator circuits?

I went thru the Ultrafast diode routine a couple years ago and ended up with the older diodes that have the Soft Recovery characteristic with trr > 60nSec, or longer - don't confuse this with basic noisy diodes that do have similar trr figures that were developed in the early days of 'switching' power supplies

It does get a bit confusing and there's plenty of contradictory advice passed around too -

I have, unfortunately, ended up with a huge collection of all sorts of diodes, mostly unusable in audio power supply circuits.
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Old 3rd December 2014, 11:36 AM   #4
diyAudio Member
Join Date: Feb 2005
Location: Melbourne
Sorry, should have added some numbers

I generally start with the MSR860 (8Amp) diodes, or their bigger brother the MSR1560s and also the BYV29s, all TO-220 package size - there's a number of other diodes in the family of the BYVs designed for soft recovery for lower current use.

No doubt, there's a lot of others.

Hope this info is of some use .....
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Old 3rd December 2014, 01:04 PM   #5
diyAudio Member
Join Date: Oct 2009
Hi, Harry

in my not DHT headphone amplifier i've gone through 4007 , then FREDs, then Schottky SiC and the Shottkys sonically are the winners, no doubt. Maybe you already know this.
What now for me is by far more important is the presence of a well calculated snubber, and Quasimodo is the easy way. Snubbers make a sonic difference( not so small) even with the Schottkys SiC.
Hope this helps.

Ciao, Trini
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