Think of it as if the two out-of-phase signals are input to a transformer with two primary windings. Say the primaries have pins 1-2 and pins 1a-2a, such that a pos signal at pin 1 or 1a causes a positive signal at the secondary.
Start with the '0-degree' signal, connect it to pin 1 and ground pin 2, that causes a pos signal at the secondary.
Now we connect the '180-degree' signal to the other primary but this time we connect it in the opposite way: we connect the '180-degree' signal to pin 2a and we ground pin 1a. This again causes a pos signal at the secondary! Connect both signals and you get a nice clean signal on the secondary.
That's what actually happens in the amp, except that there's some tube between the signal from the splitter and the xformer to provide some extra muscle, but the principle stays the same.
Does that help?
jd
As you say, one side handles the -ve going waveform. But to create that -ve going waveform you need to switch on a tube, which requires a +ve going waveform. Hence you need a phase splitter.
The output transformer winding for this tube dedicated to -ve going waveforms is then wired out of phase, so the tube's +ve going output is once again phase inverted to a proper -ve going output.
I.e. the phase inverter + transformer connection on the -ve going tube allow the tube to operate in a +ve going way to create the -ve going signal.
Positive: 1:Buffer, 2:amplifiy, 3
utputNegative: 1:Invert, 2:amplify, 3:invert
in the 1:splitter, 2:tube and 3:transformer sections
I'm not an expert but have picked this stuff up over about 30 years, you should read the books pointed out at the thread as you need to gain that knowledge in a short amount of time - it will make a huge difference in how you explain stuff.
In addition 'crossover' in this context means the handing over of signal from the +ve side to the -ve side - the transition and subsequent crossover distortion. This also relates to class A, class AB, class B operation.
Why don't you come clean and tell us what you are attempting to do? People often pop up with obscure questions and then a dozen posts later it emerges what they are really trying to do - often they were asking the wrong question so we were giving them correct but unhelpful answers. Sometimes the most helpful answer is "don't do it!".
You are obviously puzzled by quite elementary electronics so you need to do an awful lot of reading (and building and debugging) before you should even think about writing something for others. Or has someone dropped this task on you despite your protests and you are trying to do your best? Please tell us!
You are obviously puzzled by quite elementary electronics so you need to do an awful lot of reading (and building and debugging) before you should even think about writing something for others. Or has someone dropped this task on you despite your protests and you are trying to do your best? Please tell us!
I am editor of Secrets of Home Theater and High Fidelity. I have a great love of tubes, and am very happy that tube products have re-emerged in a big way. I have reviewed several tube preamps and power amps recently, such as the Lamm LL1, which is a single-ended pure Class A triode preamp with only one gain stage, but each channel has four 6H30 dual triodes.
Lamm LL1 Signature Stereo Tube Preamplifier - An Audiophile's Dream
Explaining single-ended is easy, but I am having a tough time with the balanced and push-pull, because I can't find an explanation of where the phase inversion occurs at the output to make the negative half of the waveform in the proper phase as it was at the input before phase splitting/inversion. It sounds from the latest posts that this is something that occurs in the output transformer. I have attached another diagram. I know it's hard to put into writing an explanation that would best be served by something like a webinar where we could draw things on top of the diagram as the explanation occurs, but take a look at the diagram and state where the taps might be from top to bottom on the primary winding and which parts of the waveform come out on the secondary winding.
Lamm LL1 Signature Stereo Tube Preamplifier - An Audiophile's Dream
Explaining single-ended is easy, but I am having a tough time with the balanced and push-pull, because I can't find an explanation of where the phase inversion occurs at the output to make the negative half of the waveform in the proper phase as it was at the input before phase splitting/inversion. It sounds from the latest posts that this is something that occurs in the output transformer. I have attached another diagram. I know it's hard to put into writing an explanation that would best be served by something like a webinar where we could draw things on top of the diagram as the explanation occurs, but take a look at the diagram and state where the taps might be from top to bottom on the primary winding and which parts of the waveform come out on the secondary winding.
Attachments
Just as an fyi, every tube preamp I've ever seen/touched/designed/built/listened to is single ended class A, including the cheapest ones. So don't get buffaloed by marketing spin. It's like claiming that THIS preamp uses only metal wires.
There's no "phase inversion" of the negative signal- the transformer is a stupid device and only knows that one end is going more positive than the other, and the secondary reflects that.
edit: there ARE some balanced tube preamps out there (as opposed to push pull), but they represent a very small minority. And they (as well as the much-more-common single ended) are also all Class A.
You are missing the center tap for the B+ i n your transformer primary.
The phase inversion is necessary because the transformer primary is wound such that the steady state bias current from the two tubes cancel each other. The windings are out of phase to accomplish this. Since they are out of phase, the driving signals from the output tubes MUST be out of phase with respect to each other to add (double negative) to produce a useful output.
The phase inversion is necessary because the transformer primary is wound such that the steady state bias current from the two tubes cancel each other. The windings are out of phase to accomplish this. Since they are out of phase, the driving signals from the output tubes MUST be out of phase with respect to each other to add (double negative) to produce a useful output.
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As SY says above, this is marketing hype, I challenge you to find a class B or AB preamp, and I challenge you to find a push-pull one.
Class AB/B and push-pull are created purely to save cost and add efficiency to power amplifiers, in preamps either technique would be pointless and costly (and sound worse).
As for the 'phase inversion' I see you have not read my post above very carefully at all. Every word counts, you can't miss any out or skim read it, but it does tell you exactly and concisely how a push-pull works.
I have no idea why you'd need 4 triodes in a single gain stage, the most a gain stage I can think of needs 2 or perhaps 3. The 'best' stage IMO has a single triode and a current source..
In general, as you are a reviewer:
You also need to learn that there is nothing magical about tubes, merely the application of very few linear devices carefully to a problem. The transistor equivalent is a lot of transistors assembled carelessly and then straightened up with a huge dose of negative feedback, smearing the distortion over the music. Distortion is a fixed thing, you can move it, sometimes hide it, but never cancel it after the event. This simple philosophy is why a good tube amp sounds dynamic and effortless when a cheaply made class B transistor like Naim etc. sounds screechy and flat. A well designed tube amp also takes advantage of the natural linearity of operating small signals with high voltages, another trick that most transistor designers miss.
Also bear in mind speakers sound miles better with tube amps, so any you thought were too screechy need to be re-reviewed with a tube amp. A pre-amp will have little effect - you need to change the power amp to tube: that's the critical interface IMO.
At DiyAudio you find real hi-fi, free of hype and price tags and a concentration of the best minds in hi-fi so be prepared for some pre-conceptions to be shattered
In case original poster is still baffled, in my last post I completely forgot to suggest you look at those phase splitter drawings in reverse (since there really isn't any "directionality" in a tranformer).
Imagine plates of a pair of push-pull tubes driving the phase splitter output, as an input.
It seems what you're really missing is how a transformer works. In that case you may as well forget about the tubes for a while until you recognize how the voltages appear on various transformer windings. The tubes don't have anything to do with that and are probably just serving to throw you at this point.
Imagine plates of a pair of push-pull tubes driving the phase splitter output, as an input.
It seems what you're really missing is how a transformer works. In that case you may as well forget about the tubes for a while until you recognize how the voltages appear on various transformer windings. The tubes don't have anything to do with that and are probably just serving to throw you at this point.
Thanks for answering my question. It might have made things simpler if you had said at the beginning what you are actually trying to do. I think your best bet is to stick to editing for now, and leave the techy stuff to techies. Otherwise there is a risk you may inadvertently mislead your readers. Those with knowledge will lose confidence in you; those without may learn something which is not actually true.
In the long run you can get up to speed, just as we have, but it doesn't happen overnight. Electronics is a fascinating subject, and combines science and art in a way which engages the creativity of some very clever people.
In the long run you can get up to speed, just as we have, but it doesn't happen overnight. Electronics is a fascinating subject, and combines science and art in a way which engages the creativity of some very clever people.
As SY says above, this is marketing hype, I challenge you to find a class B or AB preamp, and I challenge you to find a push-pull one.
Class AB/B and push-pull are created purely to save cost and add efficiency to power amplifiers, in preamps either technique would be pointless and costly (and sound worse).
Here is a tube preamp that uses Series Regulated Push Pull, but I guess that is not what you are referring to?
Mystère - ca21
Balanced Audio Technology preamps are all fully balanced.
http://www.balanced.com
About the transformer and phase inversion, how do solid state amplifiers accomplish the same result with no output transformers?
1/ Go to www.vacuumstate.com
2/ Find the schematics section
3/ Open the RTP3D schematic
4/ Tell me that it's not a P-P design.
I prefer to call it a differential design, as P-P gets such bad press. But it's (of course) running in Class A1.
But it's not the only one. Atma-sphere make two differential (P-P) preamps, and I have seen some famous older profession preamps from Siemens that are all transformer coupled push-pull. There may even be more.
We also make a single ended preamp with similar circuit topology - but the differential one sounds better.
Regards, Allen
I've been at it a long time. Built my first radio transmitter from scratch when I was 12, got my radio license KN7MQK at that point. Been building stuff from scratch ever since, tube and solid state. I just want to understand more of the how and why rather than just the what. My problem is that I never took courses in electrical engineering. Got two bachelors degrees, one masters degree, and my doctorate in Neuroscience. That didn't do me any good when it came to understanding electrical circuits, although I have worked with ultra-high resolution microscopes that use 200,000 volts to accelerate the electrons down the microscope column.
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I have no idea why you'd need 4 triodes in a single gain stage, the most a gain stage I can think of needs 2 or perhaps 3. The 'best' stage IMO has a single triode and a current source..
At DiyAudio you find real hi-fi, free of hype and price tags and a concentration of the best minds in hi-fi so be prepared for some pre-conceptions to be shattered
I think Lamm uses the four triodes to insure the lowest output impedance possible, and also it will drive any type and length of cable.
My pre-conceptions about hype and price tags have not been shattered by anything I have learned so far, except perhaps for some audio cables that the manufacturers want $30,000 for (and they are selling apparently). My rig consists of a VPI-HRX turntable, Manley Steelhead phono preamp (tubed), McIntosh MCD500 SACD player, OPPO BDP-83/NuForce universal Blu-ray player, Balanced Audio Technology (BAT) VK-5i preamplifier (balanced, Class A triodes), Lamm LL1 preamplifier (single-ended Class A triodes), Anthem D2 SSP, BAT VK-500 stereo power amplifier (all solid state), BAT VK-75SE Class A triode stereo power amplifier, Lamm M2.2 monoblock power amplifiers (hybrid - tube second stage, solid state output stage), McIntosh MC1201 monoblock power amplifiers (all solid state), McIntosh MC600 stereo power amplifier (all solid state), Classe CA-5200 multi-channel power amplifier, Audiostat full range electrostatic speakers, Magneplanar M1.6 planar speakers, Carver Mark IV ribbon speakers, six Velodyne 18" subwoofers, and various and sundry accessories.
A photo of my main listening room is attached. I have my drums in there as well, and use them to play along with my classic jazz LPs. When I do critical listening, I loosen three clamps that attach all the drums together via four chrome tubes, and move it all against the rear wall.
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Or to put it another way... If you are reviewing $30k cables, and want to write up something about tube amps, buy Morgan Jones book Valve Amplifiers for $40. Spend a little quality time with the book, then come back here with questions.
In the process, you will learn something (hopefully a lot), and gain more respect (surely a lot) from the folks here. And probably be 10000x more qualified to share your opinion with your readers about anything with a tube in it.
Otherwise, there is likely be more commentary about your circuits than tube circuits, regardless of pictures of your listening room.
Good luck!
In the process, you will learn something (hopefully a lot), and gain more respect (surely a lot) from the folks here. And probably be 10000x more qualified to share your opinion with your readers about anything with a tube in it.
Otherwise, there is likely be more commentary about your circuits than tube circuits, regardless of pictures of your listening room.
Good luck!
Ah yes - SRPP (like this) - sorry I meant one involving a separate phase splitter and transformer, the SRPP is a type of intrinsic push-pull I guess
You can buy an SRPP preamp sans PSU and case ready made now for peanuts - all the sound, none of the cost. Stiff enough to drive headphones too.
Ahh, now you've gotten into the question about balanced versus push-pull, which are NOT synonyms.
I think the questions you have are good ones, and they can be cleared up with some study- it's unlikely that you'll glean enough information from hit and run postings on Internet forums to get a solid grounding (bad pun, sorry) in the fundamentals of amplifier design. For the purposes of a short-term need for an article, you might want to get an actual technical person to write it.
For the purpose of longer term knowledge and the ability to write (and edit) technically-oriented pieces, as well as being able to vett the writing of others, the suggestion of Morgan Jones's books on tube amplifiers is an excellent one. Not only will several weeks of study make you a whole lot smarter about this stuff, Morgan sets the bar (IMO) for clear technical exposition and excellent writing.
I am always puzzled when I hear of people building gear without really understanding how it works. But that is just me; I find the understanding is more interesting than the building and using! My education as a physicist is probably to blame.
There are two books you should read: Morgan Jones on valve amplifiers, and Scroggie/Amos "Foundations of Wireless and Electronics". MJ is a bit opinionated, so don't believe every single word but he writes very clearly. Scroggie starts from basic science and builds a knowledge of electronics on a solid foundation. I studied that book when I was a teenager.
There are two books you should read: Morgan Jones on valve amplifiers, and Scroggie/Amos "Foundations of Wireless and Electronics". MJ is a bit opinionated, so don't believe every single word but he writes very clearly. Scroggie starts from basic science and builds a knowledge of electronics on a solid foundation. I studied that book when I was a teenager.
sdinfo (John?),
If you are asking questions here so that you may pass on knowledge to a wider audience then that is theoretically a good thing in general terms.
However, please note that audiences of sites such as yours expect comentators and advisors to be at the very least 'quite knowledgeable and experienced' in the subject upon which they write. If a reader of your site were to casually pass through this site they might say "hey, that guy doesn't really know tubes at all, and is just sucking information from DiyAudio to post on HomeTheatreHiFi". That may portray you as quite shallow, and may do you no favours.
So, with that in mind, my recommendations are as follows...
1. Stop commentating on subjects you do not yet understand in depth
2. Buy the Morgan Jones books
3. Buy the Art of Electronics book
4. Build a couple of starter projects (...consider starting with an op-amp headphone amp, commonly known as a C-moy)
5. Build a tube amp kit (...consider a TubeCad Akido preamplifier)
6. Use the resources of the net (...some links given earlier in this thread by others)
7. Read, learn, do... read, learn, do... etc. until you know the subject competently
8. Then, and only then, open up a Vacuum Tube section on HomeTheatreHiFi whereby you can start to give real, knowledgeable, experienced, and useful advice to your readers
9. Enjoy the intellectual satisfaction of your enhanced tube-based achievements...
[Edit, I see you have some electronics building experience; well, just integrate it into the above...]
.......................
On your site, I see that you reviewed the $42,690 Lamm preamplifier, which you describe as " I will use a noun: Magic. I have never heard anything like it before, and I suspect I won't encounter it again". Well, if you can get past reviewer bias, elitist image, and marketing hype, I offer to build you a perfectly presented clone for just $20,000. In a double blind test I guarantee you will not be able to separate them, and you'll save $22,690 !!!
Now that must surely be the bargain of the year...
...any takers???
If you are asking questions here so that you may pass on knowledge to a wider audience then that is theoretically a good thing in general terms.
However, please note that audiences of sites such as yours expect comentators and advisors to be at the very least 'quite knowledgeable and experienced' in the subject upon which they write. If a reader of your site were to casually pass through this site they might say "hey, that guy doesn't really know tubes at all, and is just sucking information from DiyAudio to post on HomeTheatreHiFi". That may portray you as quite shallow, and may do you no favours.
So, with that in mind, my recommendations are as follows...
1. Stop commentating on subjects you do not yet understand in depth
2. Buy the Morgan Jones books
3. Buy the Art of Electronics book
4. Build a couple of starter projects (...consider starting with an op-amp headphone amp, commonly known as a C-moy)
5. Build a tube amp kit (...consider a TubeCad Akido preamplifier)
6. Use the resources of the net (...some links given earlier in this thread by others)
7. Read, learn, do... read, learn, do... etc. until you know the subject competently
8. Then, and only then, open up a Vacuum Tube section on HomeTheatreHiFi whereby you can start to give real, knowledgeable, experienced, and useful advice to your readers
9. Enjoy the intellectual satisfaction of your enhanced tube-based achievements...
[Edit, I see you have some electronics building experience; well, just integrate it into the above...]
.......................
On your site, I see that you reviewed the $42,690 Lamm preamplifier, which you describe as " I will use a noun: Magic. I have never heard anything like it before, and I suspect I won't encounter it again". Well, if you can get past reviewer bias, elitist image, and marketing hype, I offer to build you a perfectly presented clone for just $20,000. In a double blind test I guarantee you will not be able to separate them, and you'll save $22,690 !!!
Now that must surely be the bargain of the year...
...any takers???
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