First of all: thanks, Andy, for starting this thread. I have basically the same question(s).
My recommendation is to read all of Nelson Pass' articles, which can be found on the Pass Laboratories and First Watt sites. Read them chronologically, and they should be easier to follow than the hundreds of thousands of postings here. You'll still need to learn from the enhancements that have originated on diyAudio, but I suggest a strong foundation of the original articles before getting too deep here.
As to your question about IN+ and IN-, I believe it has already been answered that you probably don't want to bother unless you have balanced sources. However, if you read Papa's articles closely, a few of the balanced amplifiers have exceptional performance even with unbalanced inputs, although most suffer. At least that is what I recall.
Personally, I have several professional grade DACs with balanced XLR or balanced 1/4" TRS outputs, so I am seeking an amplifier with balanced inputs. If you were building your own DAC board with one of the balanced chips, then this would also be a good match.
Regarding preamps, my professional DACs have outputs calibrated to the professional +4 dBu level. They're actually capable of generating +26 dBu! In my case, I assume that I have no need for a separate preamp. One of these days, I'm going to compare the voltages. +26 dBu corresponds to 20 V peak-to-peak, or 15 Vrms. I should review the preamp articles, but I think this is more than most of the preamps put out. If so, I'm sure I don't need a preamp.
To those who suggest the F5, it only has single-ended RCA inputs, so it is not suitable for my needs. I think that is an important consideration, but it really depends upon what gear you already own.
One thing I am struggling with is the super symmetry output. Maybe I should read the article again. Is super symmetry only possible with voltage output amplifiers? After reading about Papa's current output amplifier design, I am curious whether it would be possible to have a current version of the X design. There is something about the current output amplifier that I really prefer, but I also want the super symmetry to maintain balanced signals all the way to the drivers. Sorry if I'm getting the terminology wrong in this paragraph.
I followed the links to the PCB Design pages, and I am wondering if anyone can clarify the origins of the Zen-X and Zen-XA designs. Are these from Papa's articles, or did they grow out of the diyAudio community? I need to read Papa's articles again and build a guide to the various technologies in each article so that I can find my own answers more quickly. Meanwhile, I'm here looking for pointers.
I assume that the Aleph-X is a commercial design from Pass Laboratories. Is that correct?
My recommendation is to read all of Nelson Pass' articles, which can be found on the Pass Laboratories and First Watt sites. Read them chronologically, and they should be easier to follow than the hundreds of thousands of postings here. You'll still need to learn from the enhancements that have originated on diyAudio, but I suggest a strong foundation of the original articles before getting too deep here.
As to your question about IN+ and IN-, I believe it has already been answered that you probably don't want to bother unless you have balanced sources. However, if you read Papa's articles closely, a few of the balanced amplifiers have exceptional performance even with unbalanced inputs, although most suffer. At least that is what I recall.
Personally, I have several professional grade DACs with balanced XLR or balanced 1/4" TRS outputs, so I am seeking an amplifier with balanced inputs. If you were building your own DAC board with one of the balanced chips, then this would also be a good match.
Regarding preamps, my professional DACs have outputs calibrated to the professional +4 dBu level. They're actually capable of generating +26 dBu! In my case, I assume that I have no need for a separate preamp. One of these days, I'm going to compare the voltages. +26 dBu corresponds to 20 V peak-to-peak, or 15 Vrms. I should review the preamp articles, but I think this is more than most of the preamps put out. If so, I'm sure I don't need a preamp.
To those who suggest the F5, it only has single-ended RCA inputs, so it is not suitable for my needs. I think that is an important consideration, but it really depends upon what gear you already own.
One thing I am struggling with is the super symmetry output. Maybe I should read the article again. Is super symmetry only possible with voltage output amplifiers? After reading about Papa's current output amplifier design, I am curious whether it would be possible to have a current version of the X design. There is something about the current output amplifier that I really prefer, but I also want the super symmetry to maintain balanced signals all the way to the drivers. Sorry if I'm getting the terminology wrong in this paragraph.
I followed the links to the PCB Design pages, and I am wondering if anyone can clarify the origins of the Zen-X and Zen-XA designs. Are these from Papa's articles, or did they grow out of the diyAudio community? I need to read Papa's articles again and build a guide to the various technologies in each article so that I can find my own answers more quickly. Meanwhile, I'm here looking for pointers.
I assume that the Aleph-X is a commercial design from Pass Laboratories. Is that correct?
Never mind this particular question. I did some more reading in this forum and discovered that the Zen-XA on that site is basically an untested design, or barely tested. I think I'll stick to circuits that have had a little more action.
On that note, is there a quick guide to circuits and schematics that have been popular among diyAudio members? I searched for the thread suggested earlier, titled "The Aleph X," and after a couple dozen pages and hundreds of postings, I couldn't find much in the way of concrete plans - just a lot of text and discussion. There was mention of an Aleph Wiki, but I couldn't find that, either.
^ Ahh! That's what I'm looking for! Link within Wiki also pretty much spot on:
Aleph-X 100w Amplifier Construction Notes
Cheers,
Andy
PS
Glad to see I'm not the only one attempting to unravel fact from thread!
Aleph-X 100w Amplifier Construction Notes
Cheers,
Andy
PS
Glad to see I'm not the only one attempting to unravel fact from thread!
no, its not one of his designs, it was designed primarily by Grollins with some pointers from the community and Nelson. cobbled together with existing pass aleph designs but with crosscoupled output and the XA series afaik use a different front end and not the aleph.
but yes underwurlde: i concur with these guys, the ax wiki is a great resource, but you will still find nothing conclusive, the conclusion is for you to decide. You will not find anyone posting a final AX design, it seems deliberately obtuse, so that those who succeed have done so because they have used their own smarts and are therefor less likely to blow something up in the process
because the load with the ax is tenuously centered, if let swing out of control it could easily destroy stuff . definitely read the pass articles and when you are done with that, read them again. i started trying to contribute an explanation of the aleph front end ccs variations to this thread earlier, but decided that it would simply be lip service, because i could not hope to explain it in the way that Papa does.if you are going to build it though, match everything and with the fets, preferably at the same operating conditions
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Thanks for that perspective.
Reading Papa's articles, I have the urge to mix and match ideas from multiple articles rather than build anything exactly as shown. Normally, that would seem like a risky choice, but it seems like you're saying that we're not really going to find any cookbook answers here anyway. In other words, it seems like I might as well piece together my own, unique amp, and see how it turns out. Papa certainly gives plenty of 'extra' information in each article and even hints at a lot of the 'ideas' that (I think) I had.
To summarize: If you want a sure thing, then build one of circuits from a Nelson Pass article. Otherwise, nobody has really quite done the same degree of hand-holding on any of the derivative designs.
If I have the wrong impression - entirely or partially - feel free to clarify.
True, no disrespect for Mr Rollins intended, but the AX has so many issues that it's not a design Nelson Pass would have unleashed.
More an amp for folks would want to build just one, and then spend their days consecutively enhancing it.
Of which several examples have passed by.
Interesting observation part is witnessing an easy to build and rock-solid design, fold it out and several afflictions pop up their head.
More an amp for folks would want to build just one, and then spend their days consecutively enhancing it.
Of which several examples have passed by.
Interesting observation part is witnessing an easy to build and rock-solid design, fold it out and several afflictions pop up their head.
Having just built a pair of AJ monoblocks, I agree with Jacco about how easy it is to screw up a tried and true design. If I had not had some help from a fellow forum member, I would probably spent a lot more money. I believe I have learned a lot, but it comes at a price. Considering that his designs are built with tons of safety and pratical protection built in, the idea of building something new or unofficial is both exciting and scary. Don't forget that he has been doing this stuff for a looooong time, and most of the other guys have education backgrounds that at least lessen the strain of the learning curve. That being said, have at it. Just a tip, buy triples o what you need. Just in case. Also, you do have a collection of brains here that can get you through just about anything other than the occasional electric shock.
nope, you got the gist of it just fine and i had the same urge as you, but with a cascoded semisouth circlotron mutant, or an X'd lme49830 chipamp fet hybrid. i'm building the AJX as well with Peter Daniel's boards, but if you feel you have a handle on it enough to mix and match, then go right ahead, all the building blocks are there in the articles. this is how many of these variations have come about in the first place anyway. there comes a point during the huge amount of research needed to do some of these projects that you start having your own ideas and Papa encourages this, thats what its all about. as you say, if you want a sure thing, there are several articles that present such a thing
i also feel i need to say that this doesnt reflect on Grey at all, he was the first to go out there and publicly release (at least on here) an interpretation of what was a pretty er.... grey area ...sorry 
at the time and not documented as it was still a patent issue.
that area was the X and power to him he worked through the issues and got it working and from all reports its a great amp, though a bit on the edge of stability, thats why i decided to build the JX, but there are sometimes issues that remain in the design that need to be figured out in situ on a build by build basis to balance the circuit; this is not for the faint of heart. his work on the circlotron is inspiring
at the time and not documented as it was still a patent issue. that area was the X and power to him he worked through the issues and got it working and from all reports its a great amp, though a bit on the edge of stability, thats why i decided to build the JX, but there are sometimes issues that remain in the design that need to be figured out in situ on a build by build basis to balance the circuit; this is not for the faint of heart. his work on the circlotron is inspiring
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Under,
go and download the articles from the Pass sites.
These give you a lot of simple and more complex background to the Pass style of amplification.
Then progress through B1 and F5, both very simple schematics.
Only then try to follow the complexities of aleph & X & AX etc.
Don't read F5x too early. It's a couple of learning stages beyond the F5.
go and download the articles from the Pass sites.
These give you a lot of simple and more complex background to the Pass style of amplification.
Then progress through B1 and F5, both very simple schematics.
Only then try to follow the complexities of aleph & X & AX etc.
Don't read F5x too early. It's a couple of learning stages beyond the F5.
Andy,
I finished reading all of the Nelson Pass articles, and then ran through them again taking notes on the various technologies.
I think my choice is to build the ZV7-T from Zen Variations 7: More Son of Zen and SuperSymmetry. It's more efficient than Son of Zen, because it doesn't use high power resistors for biasing. Instead, a constant current source is used. Most importantly, it has the matching cross connect of the X amplifiers.
There is also a ZV7-R variation earlier in the article, but the output current-to-voltage is handled by high power resistors. I like the idea of using the transformer as cross-coupled inductors instead.
The A-40 article explains why biasing resistors are the least efficient, and complementary push-pull transistors with a bias voltage source are the most efficient. Unfortunately, the push-pull design is not as simple, and thus less 'Zen.' In between these extremes is the constant DC current source, which keeps the circuit simple. ZV7-R and ZV7-T both hit this middle ground quite well, I think. You'll find designs here on diyAudio that seem to combine super symmetry and the doubly-efficient push-pull output stage, but I think I'd prefer to start with fewer parts.
All of my comments come from someone who has never built any of these amplifiers. I'm just sharing my summary of how I've selecting my preferring entry point into this world. Since you seem to share my affinity for super symmetry, perhaps my brief comments will be useful.
p.s. You should still read all of the articles. Maybe you'll prefer another variation.
Brian
I finished reading all of the Nelson Pass articles, and then ran through them again taking notes on the various technologies.
I think my choice is to build the ZV7-T from Zen Variations 7: More Son of Zen and SuperSymmetry. It's more efficient than Son of Zen, because it doesn't use high power resistors for biasing. Instead, a constant current source is used. Most importantly, it has the matching cross connect of the X amplifiers.
There is also a ZV7-R variation earlier in the article, but the output current-to-voltage is handled by high power resistors. I like the idea of using the transformer as cross-coupled inductors instead.
The A-40 article explains why biasing resistors are the least efficient, and complementary push-pull transistors with a bias voltage source are the most efficient. Unfortunately, the push-pull design is not as simple, and thus less 'Zen.' In between these extremes is the constant DC current source, which keeps the circuit simple. ZV7-R and ZV7-T both hit this middle ground quite well, I think. You'll find designs here on diyAudio that seem to combine super symmetry and the doubly-efficient push-pull output stage, but I think I'd prefer to start with fewer parts.
All of my comments come from someone who has never built any of these amplifiers. I'm just sharing my summary of how I've selecting my preferring entry point into this world. Since you seem to share my affinity for super symmetry, perhaps my brief comments will be useful.
p.s. You should still read all of the articles. Maybe you'll prefer another variation.
Brian
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