This paper has been recommended before by others, so this is just a reminder for those who missed it. It is highly recommended reading about soft recovery, snap factors and everything else regarding reverse characteristics of diodes.
www.microsemi.com/micnotes/302.pdf
Edit:
Some more reading:
http://personales.ya.com/lcardaba/files/High speed rectifier applications in high end.pdf
There are also a few pages about this in ON Semis "Rectifier Application Handbook" HB214, which unfortunately I couldn't find on their site right now (is it no longer available?).
www.microsemi.com/micnotes/302.pdf
Edit:
Some more reading:
http://personales.ya.com/lcardaba/files/High speed rectifier applications in high end.pdf
There are also a few pages about this in ON Semis "Rectifier Application Handbook" HB214, which unfortunately I couldn't find on their site right now (is it no longer available?).
Christer said:
The microsemi paper is very good. The only thing I would take issue with is the oscillation above zero for the snap.. The paper kinda implies the diode does that, whereas it is actually the circuit's reaction to the abrupt change of the diode conduction that does it.
For the circuit limited Irm, I still laugh at the slope from If through the zero current line..back in '82, I put a Trr circuit together that did that in 250 pSec..it allowed the diffusion guys to see what the 15 nSec product under development was really doing.
As for that Jon Schleisner guy...why would anybody believe what he has to say??? Geeze, his employer only shipped 11 million diodes per day back in '93..(fun guy, worked with him..)
I like his transient suppressor writeups also..
What suprises me though, is I don't see anything talking about the conduction across the xfmr winds during recovery time, with the resultant PC currents..and how snubs can make that worse..
Cheers, John
Anyone care to test diodes sonically? I know we all do, but, there is one aspect of diodes I'm particularly interested in. How about running a resistively loaded, DC signal, with AC signal overlay, and recover that signal? Analog throughout, of course. And put diodes in that output path. And keep switching them out for different ones. If you capacitively load your observation point*, it makes a great post to observe L, C, R and junction, separately or as a group. And check out your combinations, before you even build a circuit.
*(As in listen to, directly as possible: A headphone-centric circuit would be most valuble here)
*(As in listen to, directly as possible: A headphone-centric circuit would be most valuble here)
What I meant was, that in the end, we all do, when we use them in a circuit. But attempting to separate the sound of the given actions of the diode is interesting. When conducting, or how the transient behaviour revelas itself in terms how it turns off and what exactly it does, effect wise. Etc, etc.
I've done crazier things than that - and each one led to an understanding of each given component or component 'effect', and allowed me to surmise and deduct and head to places in 'audiophile design understandings' most folk haven't been to yet.
I've done crazier things than that - and each one led to an understanding of each given component or component 'effect', and allowed me to surmise and deduct and head to places in 'audiophile design understandings' most folk haven't been to yet.
janneman said:
No, I don't. I design my circuits in such a way as to prevent diode issues to make it to the speaker connectors.
Any amp that is showing sound differences with different diodes in a repeatable, blind test for me is an incompetent design...
Jan Didden
Perfect.
One very direct measurement which is rarely done is spectral analysis of supply voltage under differing load conditions. In the limited amount I've done, a circuit with the grounding done right just doesn't show a whole lot of difference between exotic and conventional rectifier technology in 50/60 Hz sine wave circuits.
KBK said:May I politely suggest, that you are missing the point...?
Entirely possible, it's known to have happened before.
.In that case could you explain then what the point is, I have enough self-confidence, to believe I could understand your explanation.
Until now I thought "sonically testing rectifiers" meant to evaluate rectifiers by the changes they make to the sound of a particular amplifier?
Jan Didden
KBK,
Diodes, balanced AC, PSU transformers, all of these things could make a difference. The fact remains that if they do make a difference, it indicates poor power supply design. Consider the perfect diode in a PSU. It will actually generate more energy (spectra) at higher frequencies that a regular recovery diode, despite how "nasty" it appears on a scope. Is this good or bad? It depends on the total design.
SY's remark about spectral testing under dynamic conditions is right on the money.
The push for faster, softer, smoother diodes has come about in response to the needs of SMPS design where operation is in kHz & MHz... snubbers and switching locus are a huge part of all that as well.
Diodes, balanced AC, PSU transformers, all of these things could make a difference. The fact remains that if they do make a difference, it indicates poor power supply design. Consider the perfect diode in a PSU. It will actually generate more energy (spectra) at higher frequencies that a regular recovery diode, despite how "nasty" it appears on a scope. Is this good or bad? It depends on the total design.
SY's remark about spectral testing under dynamic conditions is right on the money.
The push for faster, softer, smoother diodes has come about in response to the needs of SMPS design where operation is in kHz & MHz... snubbers and switching locus are a huge part of all that as well.
poobah said:KBK,
Diodes, balanced AC, PSU transformers, all of these things could make a difference. The fact remains that if they do make a difference, it indicates poor power supply design. Consider the perfect diode in a PSU. It will actually generate more energy (spectra) at higher frequencies that a regular recovery diode, despite how "nasty" it appears on a scope. Is this good or bad? It depends on the total design.
SY's remark about spectral testing under dynamic conditions is right on the money.
The push for faster, softer, smoother diodes has come about in response to the needs of SMPS design where operation is in kHz & MHz... snubbers and switching locus are a huge part of all that as well.
Yes, it all makes a difference in electrical terms. Yet, if I had designed an amp that sounded audibly different with a different diode, I'd hide in a corner and tell no one about it...
Jan Didden
I went to soft recovery rectifiers about 10 years ago, after we did an A-B test on a Vendetta power supply. It took me YEARS to actually believe that it could make a difference, but it did. I just upgraded Dave Wilson's Vendetta phono stage with soft recovery diodes. It is not easy to do in this case, as we did not assign much room in the power supply box, but the results are worth it. This is an example of how I continually attempt to update my older products, just to keep up with the latest efforts of others. I can now laugh at the reluctance of those who don't think that soft recovery diodes are necessary. Oh well, just more sonic wins for me.
rdf said:
Differences are less than the repeatability of the measurements. It may indeed not be measurable, at least not with the 24/192 soundcard I use. That's why I'm somewhat skeptical- DC really is DC.
I used high speed diodes in my preamp's supply, just for the hell of it, since they were pretty cheap. And, IIRC, I used the same ones in the RLD power amp. No direct sonic comparisons so I don't know if there's any voodoo effect.
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