Hi everybody!
I have been following this forum for a while now and I am about to build Aleph 5 Monoblocks for the mid/treble range in a biamped system.
One of my main concerns is about PSU design. I just read Nelson Pass´es article about the XA series. It struck me that he uses high speed /soft recovery rectifiers here in contrast to what he says in the older articles about amp psu design, where he favours slow diodes aka standard bridges bypassed by caps.
There must be some sonic benefit otherwise Pass labs wouldn´ t spend the extra dollars for those components.
Does anybody have an idea why Mr. Pass changed his mind about this issue?
Anybody ever tried both and did a comparison?
Maybe the Maestro could himself give some comments.
Thanks for your replies
Franz
I have been following this forum for a while now and I am about to build Aleph 5 Monoblocks for the mid/treble range in a biamped system.
One of my main concerns is about PSU design. I just read Nelson Pass´es article about the XA series. It struck me that he uses high speed /soft recovery rectifiers here in contrast to what he says in the older articles about amp psu design, where he favours slow diodes aka standard bridges bypassed by caps.
There must be some sonic benefit otherwise Pass labs wouldn´ t spend the extra dollars for those components.
Does anybody have an idea why Mr. Pass changed his mind about this issue?
Anybody ever tried both and did a comparison?
Maybe the Maestro could himself give some comments.
Thanks for your replies
Franz
Somewhere, i think in the alephx thread is a statement of Nelson, they use the "fancy diodes" because Wayne wants them. If you search a little bit in the board, you will find also the comment, best choice would be schottky diodes.
And you will find comments, there are much much more important things than which kind of diode, capacitors, resistor you will use.
And you will find comments, there are much much more important things than which kind of diode, capacitors, resistor you will use.
My recent experience in replacing normal diodes for FREDs in my DAC psu was quite positive. I perceived a tighter bass and more dynamics. I haven't tried it yet on the Alephs but I am thinking about it after the Dac mod. I think Nelson has said he doesn't like fast recovery types but I am not sure if that includes soft recovery types.
till said:
Here is some more comments and Mr. Pass's comment on Wayne's choice.
http://diyaudio.com/forums/showthread.php?s=&threadid=8683&perpage=15&highlight=wayne&pagenumber=1
do it!
Hi,
step by step I replaced over the last years diodes in my consumer devices by soft-recovery ones. In DIY projects I used them right from the start on. In all devices the benefits were the same. I think they are not standard due to there higher price.
It is not the most importent thing - without a One and Only design no start could be made - but to achieve 100% performance this tricky tweaking stuff is absolutely necessary. As well as best Caps with bypasses, inductance-free power resistors and so on, and so on. When I e.g. compare my DIY-Aleph with a Pass-production one a clear difference can be heared. My budget for material was allowed to be higher, that´s the difference. Lucky DIY-guys...
Klaus
Hi,
step by step I replaced over the last years diodes in my consumer devices by soft-recovery ones. In DIY projects I used them right from the start on. In all devices the benefits were the same. I think they are not standard due to there higher price.
It is not the most importent thing - without a One and Only design no start could be made - but to achieve 100% performance this tricky tweaking stuff is absolutely necessary. As well as best Caps with bypasses, inductance-free power resistors and so on, and so on. When I e.g. compare my DIY-Aleph with a Pass-production one a clear difference can be heared. My budget for material was allowed to be higher, that´s the difference. Lucky DIY-guys...
Klaus
types
Hi Baz,
I used and tested various Diodes, e g
http://www.schuro.de/Daten/IR/31dq10.pdf
http://www.schuro.de/Daten/IR/hfa08tb60.pdf
http://www.schuro.de/Daten/IR/hfa25pb60.pdf
I think all simular diodes are pretty good. The inner resistance could be helpfull with small value = good damping. But the main thing is to my understanding the much lower reverse switch off charge energy. The best should be the Schottkies, see type 1 - but "just" 3,3A nom current. And this all has nothing to do with "ultra/hyper-FAST"... We rectify 50/60Hz - but with hard class A current peaks.
What´s better: to have a Schottky or to reduce inner resistance? I don´t know yet, with my Aleph P in Progress I´ll test and report.
Regards to the Summer-half
Klaus
Hi Baz,
I used and tested various Diodes, e g
http://www.schuro.de/Daten/IR/31dq10.pdf
http://www.schuro.de/Daten/IR/hfa08tb60.pdf
http://www.schuro.de/Daten/IR/hfa25pb60.pdf
I think all simular diodes are pretty good. The inner resistance could be helpfull with small value = good damping. But the main thing is to my understanding the much lower reverse switch off charge energy. The best should be the Schottkies, see type 1 - but "just" 3,3A nom current. And this all has nothing to do with "ultra/hyper-FAST"... We rectify 50/60Hz - but with hard class A current peaks.
What´s better: to have a Schottky or to reduce inner resistance? I don´t know yet, with my Aleph P in Progress I´ll test and report.
Regards to the Summer-half
Klaus
Have a peek at MBR3045WT and kin from IR. These are what I used for my prototype Aleph-X. Can't comment yet on how they compare sonically to anything else, but these Shottky's have two nice characteristics:
1. low price (for a high performace diode)
2. very low forward voltage drop (roughly 0.55 to 0.6V), which translates directly to greater efficiency and reduced heatsinking requirements. Quite possibly this also means greater reliability. You'll have a hard time finding another diode type with such a low forward voltage drop.
1. low price (for a high performace diode)
2. very low forward voltage drop (roughly 0.55 to 0.6V), which translates directly to greater efficiency and reduced heatsinking requirements. Quite possibly this also means greater reliability. You'll have a hard time finding another diode type with such a low forward voltage drop.
I have never heard of anyone using fets as synchronous rectifiers in a 50 / 60 Hz power supply. They are the ultimate in low forward voltage drop. The idea is to put the current in the reverse direction to normal through the fet, and turn the gate on (positive as normal) when you are doing this. When the voltage is in the "normal" direction (source negative, drain positive) you keep the gate off so the thing doesn't conduct. This makes an almost ideal diode. Watch out though - the body diode of the fet while quite ok for rectifying low frequency ac, can have a very sudden, hard turnoff so it would be quite noisy. When the gate is turned on, any current that would flow through the body diode flows instead through the normal drain to source path. Only if the voltage drop (amps x rds_on) is greater than ~0.6v will current then flow through the body diode as well.
We have switched to high speed soft recovery diodes for two reasons. They are quieter when used properly (CE EMI TESTING)
and they do sound better.
I ran extensive tests for CE approval with a CISPR 15 network feeding our spectrum analyzer. Diodes generate noise from 120 Hz up to MHz that is very hard to see on a scope but shows up on the spectrum via the AC line. Caps snubbers etc didn't help and often made it worse.
and they do sound better.
I ran extensive tests for CE approval with a CISPR 15 network feeding our spectrum analyzer. Diodes generate noise from 120 Hz up to MHz that is very hard to see on a scope but shows up on the spectrum via the AC line. Caps snubbers etc didn't help and often made it worse.
wayne said:
This is my first ever post, so please forgive me if I get anything wrong or offend against any board protocol, or whtaever, with which I am not familiar.
Some eight years ago I carried out many extended listening tests (I had no appropriate test equipment) on all of the diodes I could lay my hands on at that time. I used the diodes in 'discrete' bridge rectifier configurations in several different pieces of audio gear.
To my ears, there were quite obvious differences in the 'sound' of these diodes, and the best I tried were schottkys by a noticeable margin.
Interestingly, I also tried many combinations of snubber caps, using various makes and types of caps of differing values, and came to the conclusion that they all did something to the overall sound which I didn't care for.
Since then, I have used schottkys exclusively in all of my projects and have used them both in parallel and in series to cope with higher currents and voltages (without any balancing resistors) and have not experienced any problems due to unequal power sharing, to this date. Perhaps I have just been lucky with this, but schottky diodes taken from the same batch do appear to be sufficiently well matched in specs to be OK.
Initially, I did 'blow' a couple of somewhat underrated diodes, which puzzled me, but they were being fed into a huge bank of caps which I soon realised would seem almost like a direct short to ground at switch on, so their 'surge' ratings do need to be watched.
I was heartened to see Nelson's earlier recommendation in this thread in favour of schottkys, and in particular, Wayne's remarks in this post about the 'proper' objective tests they have carried out, especially regarding snubbers, which I continually see recommended in DIY articles, but which my ears told me were (universally) not a good move.
I would very much like to know if Wayne's tests showed any possible superiority with schottkys over fast/soft recovery diodes (these were not available when I did my listening tests) which gave rise to Nelson's overall recommendation, and if it is purely on grounds of cost and restricted power handling etc. that Pass Labs don't use schottkys rather than fast/soft diodes in their production.
If anyone else has made some direct comparisons between schottkys and the latest very fast, soft recovery diodes, I would be very grateful for their comments and opinions.
Finally, although I have only just joined the Forum as a member, I have been looking at the board off and on for some months, and I am simply amazed at the generous sharing of information which occurs, and the help shown by the more knowledgeable members to those who are less experienced.
In this day and age, it is simply wonderful to see so many like-minded people, who are not only out to do everyone else down, freely sharing their knowledge and experiences.
Long may it continue, and whilst it was very sad to see some animosity creeping in a while ago in a few areas, hopefully with a slightly more enlightened approach from the current Moderators, the Forum will go from strengtb to strength.
I almost hesitate to mention this in my virgin post (as subjective opinions seem to really excite and agitate some people to an extraordinary extent), but I have spent over 30 years patiently 'listening' to active and passive components in all manner of audio circuits, and during that time I have reached some quite positive conclusions.
I sincerely hope that I will be able to add something worthwhile to the discussions, where appropriate, at some times in the future, out of grattitude for what I have picked up as a guest onlooker during the past few months.
A very Happy New Year to you all.
Welcome to the forum, Bob!
If your first post is any indication, I know that I and other members will be looking forward to hearing more from you! Controversial or not, opinions are always welcome here, since not everyone has the time and means to do things like head-to-head rectifier comparisons... there are just so many variables in any audio design, one could spend a lifetime doing comparisons of this and that. That's what makes this forum so special - the sharing of information, experiences, and ideas!
As far as the negativity which creeps in every now and then, I've found that simply ignoring it altogether is a great way to deal with it! I've not felt offended or invaded in any way since I just started ignoring all the "noise" content, and i think, by ignoring it and removing myself from the pool of contributors, I'm doing the rest of the forum a favour too. I encourage everyone else to ignore the noise too, and soon enough, I think we'll find the content here improving further, while the loudmouths discover that there is no one left to preach to. Building on that, I think it will help if the moderators continue moving the noise posts to their own lonely little corner, where they can fester without affecting the rest of the forum. Anyway, I'm almost contributing to the noise myself now, so I'll leave it at that.
Once again, welcome to the forum, and thanks for sharing your experiences. I'm that much more confident that my choice of rectifiers was a good one, and I'll stick with that, since I really have no intention of swapping and comparing them myself.
Regards,
If your first post is any indication, I know that I and other members will be looking forward to hearing more from you! Controversial or not, opinions are always welcome here, since not everyone has the time and means to do things like head-to-head rectifier comparisons... there are just so many variables in any audio design, one could spend a lifetime doing comparisons of this and that. That's what makes this forum so special - the sharing of information, experiences, and ideas!
As far as the negativity which creeps in every now and then, I've found that simply ignoring it altogether is a great way to deal with it!
I've not felt offended or invaded in any way since I just started ignoring all the "noise" content, and i think, by ignoring it and removing myself from the pool of contributors, I'm doing the rest of the forum a favour too. I encourage everyone else to ignore the noise too, and soon enough, I think we'll find the content here improving further, while the loudmouths discover that there is no one left to preach to. Building on that, I think it will help if the moderators continue moving the noise posts to their own lonely little corner, where they can fester without affecting the rest of the forum. Anyway, I'm almost contributing to the noise myself now, so I'll leave it at that. Once again, welcome to the forum, and thanks for sharing your experiences. I'm that much more confident that my choice of rectifiers was a good one, and I'll stick with that, since I really have no intention of swapping and comparing them myself.
Regards,
Here in Japan, the sonic changes due to different rectifiers have been noted and utilized for more than 20 years. If anything, it was the manufacturers like Fidelix, Pioneer, Yamaha etc that led the way, with the DIY community following, in many cases by using parts that were developed for or first featured in commercial amplifiers. (This is a similar situation to what has happened with audio-grade capacitors and resistors.)
In my experience, sonic differences are caused not only by the category of rectifier diode, but the manufacturer as well. Undoubtedly, HERs, FRDs, Schottkys etc. sound different, but a Schottky from IRF will also sound different from one by GI, Fuji, et al. In fact, I find that an FRD and a Schottky by IRF may sound sonically closer to each other than a Schottky by IRF and another Schottky by Fuji will.
My personal opinion is that this has something to do with the individual semiconductor processes used.
regards, jonathan carr
In my experience, sonic differences are caused not only by the category of rectifier diode, but the manufacturer as well. Undoubtedly, HERs, FRDs, Schottkys etc. sound different, but a Schottky from IRF will also sound different from one by GI, Fuji, et al. In fact, I find that an FRD and a Schottky by IRF may sound sonically closer to each other than a Schottky by IRF and another Schottky by Fuji will.
My personal opinion is that this has something to do with the individual semiconductor processes used.
regards, jonathan carr
Hi Jonathan,
Thanks for your comments which don't surprise me at all.
It has become quite obvious to me that (similar type) passive components from the same manufacturer all seem to exhibit 'family' sonic resemblances, and with transistors I have noticed that some maker's products are definitely different sounding from others, despite their being nominally an identical part no.
Have you reached any conclusions that you are happy to share regarding any general preferences over diodes, and who makes the most desirable ones?
During the past few months when I have been looking at the Forum as a guest, I have picked up some very useful information and ideas from your posts.
It is the generosity exhibited by members like yourself which prompted me to join up on Xmas day, and I hope I may in turn be able to help a few others through sharing some of my own experiences where appropriate.
At the very least, it may encourage others to try out some of the listening tests which I have found rewarding, and I am always interested in hearing about other peoples' conclusions, provided, of course, they are not merely based on hearsay or guesswork, and even if their perceived results do not agree with my own.
Thanks for your comments which don't surprise me at all.
It has become quite obvious to me that (similar type) passive components from the same manufacturer all seem to exhibit 'family' sonic resemblances, and with transistors I have noticed that some maker's products are definitely different sounding from others, despite their being nominally an identical part no.
Have you reached any conclusions that you are happy to share regarding any general preferences over diodes, and who makes the most desirable ones?
During the past few months when I have been looking at the Forum as a guest, I have picked up some very useful information and ideas from your posts.
It is the generosity exhibited by members like yourself which prompted me to join up on Xmas day, and I hope I may in turn be able to help a few others through sharing some of my own experiences where appropriate.
At the very least, it may encourage others to try out some of the listening tests which I have found rewarding, and I am always interested in hearing about other peoples' conclusions, provided, of course, they are not merely based on hearsay or guesswork, and even if their perceived results do not agree with my own.
ultra fast soft recovery rectifiers
Hi, it is my first post in this forum, sorry if i am not following all the rules.
I tried two times to replace my old "fashion" diodes but my teacher
in university says when use this "new" (ultra fast soft recovery) diodes as a rectifier, he notice saturation.
Giannis
Hi, it is my first post in this forum, sorry if i am not following all the rules.
I tried two times to replace my old "fashion" diodes but my teacher
in university says when use this "new" (ultra fast soft recovery) diodes as a rectifier, he notice saturation.
Giannis
Re: ultra fast soft recovery rectifiers
Hi Giannis, I am also new to the forum, so you are in good company!
Whilst I don't consider myself to be the definitive expert on these matters, I don't fully understand your reference to the term "saturation" in connection with diodes. This suggests some kind of overload distortion to me, but I have not come accross this in relation to diodes used in bridge rectifiers.
Perhaps in translation to english the meaning has become distorted somehow, but if you could explain exactly what the problem is that you are concerned about, either I, or someone more knowledgeable than me, may be able to allay your concerns.
What is the practical or observed bad effect, or the result of this "saturation" that your teacher has mentioned to you?
Regards,
lll said:Hi, it is my first post in this forum, sorry if i am not following all the rules.
I tried two times to replace my old "fashion" diodes but my teacher
in university says when use this "new" (ultra fast soft recovery) diodes as a rectifier, he notice saturation.
Giannis
Hi Giannis, I am also new to the forum, so you are in good company!
Whilst I don't consider myself to be the definitive expert on these matters, I don't fully understand your reference to the term "saturation" in connection with diodes. This suggests some kind of overload distortion to me, but I have not come accross this in relation to diodes used in bridge rectifiers.
Perhaps in translation to english the meaning has become distorted somehow, but if you could explain exactly what the problem is that you are concerned about, either I, or someone more knowledgeable than me, may be able to allay your concerns.
What is the practical or observed bad effect, or the result of this "saturation" that your teacher has mentioned to you?
Regards,
Borc said:
Yes, you can use merely one half of a common cathode schottky, if you wish to.
Just don't connect the third (unwanted) lead.
Should that particular diode ever 'blow', you could still use the other half of the diode in its place.
It does seem to be a little wasteful though in cost, but it shouldn't normally be necessary to use all four (separate) dual diodes to make up a full wave bridge, if this is what you are trying to do.
It should be possible to arrange the layout so that you could use one dual diode for one 'side' of the bridge, and then use one half of each of two other dual diodes for the remaining 'side'.
This way, you will be using three (rather than four) dual diodes in total, and you will in effect have two 'spares' to cover for any mishaps.
Regards,
Bob:
Thank you for your comments. It is always nice to hear words of appreciation.
>I am always interested in hearing other peoples' conclusions, provided they are not merely based on hearsay or guesswork.<
In audio I believe that there is a place for theory and measurements as well as subjective experience. But I want to think for myself, do things for myself, and experience things for myself. And I prefer people who likewise have a willingness to think, act, and experience for themselves. Because without this, how is it possible to contribute anything unique?
I find that careful observation combined with a certain amount of educated guesswork can often be beneficial, but more frequently than not (especially on the Internet, it would seem), hearsay merely spreads mis-information around.
>And even if their perceived results do not agree with my own.<
Yes. And I don't think that agree vs. disagree is even all that different, as long as the reasons are based on direct personal experience. And in many cases, disagree is more important, because you are more likely to learn something new, as a result of receiving input that lies outside of your own experiences.
In my own audio work, I believe in combining theory, measurements and subjective listening in a mutually interactive feedback loop.
>Have you reached any conclusions that you are happy to share regarding any general preferences over diodes, and who makes the most desirable ones?<
Different types of topologies measure differently and have their distinct sound. Likewise with circuit and chassis constructions, and active and passive components. There are many variables that the individual audio designer is free to choose from, dictacted only by personal believe and preference. And the interactions arising from all of these variables can be complex, and at times, somewhat unpredictable.
Hence, questions like "who makes the most desirable parts" are not useful UNLESS you are building the same types of circuits that I do. And even among my own circuits, each circuit has a "sound of its own", and therefore has unique requirements for what should be done to it to bring it range of something that "sounds good" or is "sonically neutral" - both of which are again subjective judgements.
I think that a more useful question is not "what is best", but "what does this sound like", and "when and how is it appropriate to use this".
When we listen to different passive or active components that may happen to measure similarly, it isn't like we are trying to establish what the best-tasting flavor is. The feeling is closer to trying to establish whether what we have is tarragon, coriander, rosemary, dill, ginger, or wasabi. You would use ginger because you tasted a dish and felt that the use of ginger would benefit the flavor and make it taste good to you, but you wouldn't use ginger mindlessly on any and all dishes (at least I hope you wouldn't). On top of that, ginger may taste some differently depending on their place of origin. Ginger root from China tastes rather stronger than the stuff that is grown in Japan, and the smell is different, too.
Perhaps I will build a circuit with some types of rectifiers, listen to it, and establish if it lacks anything or has too much of something. Based on that experience, I may leave the original rectifier in place, or choose a completely different one. If I change the type, I will listen again and see if my analysis and guess were right. I am very rarely off when it comes to the basic direction that I want the sound to go in, but sometimes I may decide that I didn't go too far, or perhaps overshot my target. You get better with practice...
I suppose that I end up choosing Nippon Inter http://www.niec.co.jp/ diodes more frequently than other makes, but I also use IRF, GI, Fuji, Toshiba, Hitachi, Unison, Sanken Shinden, and others. And I may further choose Schottkys, FRDs, HERs, GaAs, and whatnot. As I indicated earlier, I may start out with something arbitrary, but I really don't know what I will end up until I go through a complete listening cycle.
Sorry that I cannot provide an answer that is succinct and neatly packaged, but that's life for you...
regards, jonathan carr
Thank you for your comments. It is always nice to hear words of appreciation
.>I am always interested in hearing other peoples' conclusions, provided they are not merely based on hearsay or guesswork.<
In audio I believe that there is a place for theory and measurements as well as subjective experience. But I want to think for myself, do things for myself, and experience things for myself. And I prefer people who likewise have a willingness to think, act, and experience for themselves. Because without this, how is it possible to contribute anything unique?
I find that careful observation combined with a certain amount of educated guesswork can often be beneficial, but more frequently than not (especially on the Internet, it would seem), hearsay merely spreads mis-information around.
>And even if their perceived results do not agree with my own.<
Yes. And I don't think that agree vs. disagree is even all that different, as long as the reasons are based on direct personal experience. And in many cases, disagree is more important, because you are more likely to learn something new, as a result of receiving input that lies outside of your own experiences.
In my own audio work, I believe in combining theory, measurements and subjective listening in a mutually interactive feedback loop.
>Have you reached any conclusions that you are happy to share regarding any general preferences over diodes, and who makes the most desirable ones?<
Different types of topologies measure differently and have their distinct sound. Likewise with circuit and chassis constructions, and active and passive components. There are many variables that the individual audio designer is free to choose from, dictacted only by personal believe and preference. And the interactions arising from all of these variables can be complex, and at times, somewhat unpredictable.
Hence, questions like "who makes the most desirable parts" are not useful UNLESS you are building the same types of circuits that I do. And even among my own circuits, each circuit has a "sound of its own", and therefore has unique requirements for what should be done to it to bring it range of something that "sounds good" or is "sonically neutral" - both of which are again subjective judgements.
I think that a more useful question is not "what is best", but "what does this sound like", and "when and how is it appropriate to use this".
When we listen to different passive or active components that may happen to measure similarly, it isn't like we are trying to establish what the best-tasting flavor is. The feeling is closer to trying to establish whether what we have is tarragon, coriander, rosemary, dill, ginger, or wasabi. You would use ginger because you tasted a dish and felt that the use of ginger would benefit the flavor and make it taste good to you, but you wouldn't use ginger mindlessly on any and all dishes (at least I hope you wouldn't). On top of that, ginger may taste some differently depending on their place of origin. Ginger root from China tastes rather stronger than the stuff that is grown in Japan, and the smell is different, too.
Perhaps I will build a circuit with some types of rectifiers, listen to it, and establish if it lacks anything or has too much of something. Based on that experience, I may leave the original rectifier in place, or choose a completely different one. If I change the type, I will listen again and see if my analysis and guess were right. I am very rarely off when it comes to the basic direction that I want the sound to go in, but sometimes I may decide that I didn't go too far, or perhaps overshot my target. You get better with practice...
I suppose that I end up choosing Nippon Inter http://www.niec.co.jp/ diodes more frequently than other makes, but I also use IRF, GI, Fuji, Toshiba, Hitachi, Unison, Sanken Shinden, and others. And I may further choose Schottkys, FRDs, HERs, GaAs, and whatnot. As I indicated earlier, I may start out with something arbitrary, but I really don't know what I will end up until I go through a complete listening cycle.
Sorry that I cannot provide an answer that is succinct and neatly packaged, but that's life for you...
regards, jonathan carr
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