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Bronze Member Username: Mike3Lewisville, Tx USA Post Number: 34 Registered: May-06 | For what it is worth. I found this on a journey to understand Tube Amps, SE vs. PP, compared to transistor or hybrid designs. I am probably not the last person to know this, but in that I pride myself in my mathematical acuity, I do not know why I had to read this on the internet to consider it; http://usuarios.uninet.com.br/~edelima/REASONS.htm 'If there is more distortion in the system than in the speaker alone in most of the frequency range, just reverse the polarity of the connection between the amplifier and the speaker (This is the ONLY place to invert it) and you will have shifted 180Aº the amplifier. Now you have a good chance of getting less distortion than you started with and probably less distortion than the speaker alone! This is usually clearly audible.' It continues with more information but it moves away from speakers which is why I included the link should anyone want to investigate further. My apologies if I am reposting something that was previously dealt with in any detail as I lack the patience to search the 938 repsonses I received to an ecoustics serch for "180". However I did find the "Definitions and descriptions thread which I have bookmarked. |
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Gold Member Username: Jan_b_vigneDallas, TX Post Number: 8871 Registered: May-04 | . Alas, poor Yorick, I knew the definitions and descriptions thread well. |
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Gold Member Username: John_aLondonU.K. Post Number: 4419 Registered: Dec-03 | It was a thread of infinite jest. Michael, thanks. I have only just understood the need for absolute polarity, and as I understand it, it is only necessary to reverse polarity if the absolute phase is wrong (180 º out) on the recording. It seems to me that a consequence of switching the amp-speaker polarity on both channels will be to put an in-phase recording out of phase. One could bring it back in by switching polarity also between the source and the amp or between the pre-amp and power-amp. This would mean that one should try four different combinations of connections on each recording. What an absurdity. Don't amp manufacturers take some care to assign the + and - input and output terminals correctly in order to preserve polarity and also to minimize distortion? |
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Gold Member Username: NuckPost Number: 3447 Registered: Dec-04 | 'If there is more distortion in the system than in the speaker alone in most of the frequency range, just reverse the polarity of the connection between the amplifier and the speaker (This is the ONLY place to invert it) and you will have shifted 180º the amplifier. Now you have a good chance of getting less distortion than you started with and probably less distortion than the speaker alone! This is usually clearly audible. By switching the speaker leads, we affect the output portion of the amp, ok. But if the source is out of phase, how will I lower distortion in the preamp section of piece? This quote is stated for tubes it says,does this nullify the phase selection uselulness of my preamp? |
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Bronze Member Username: Mike3Lewisville, Tx USA Post Number: 35 Registered: May-06 | Believe it or not my Rogue Audio Magnum 99 Tube Pre-Amp Manual indicates it is of reverse polarity and that I should reverse the speaker connections from Amp to speaker. I did this at first, but then while using a David Chelsky speaker set-up CD I identified that I needed to unreverse (if that's a word) the speaker connections and run it normal. |
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Gold Member Username: Jan_b_vigneDallas, TX Post Number: 8875 Registered: May-04 | . MW - Then it's possible your amplifier also inverts phase 180°. Too many manufacturers do not indicate whether their equipment inverts phase. This is a total disservice to their buyers. However, my point is switching phase only at the pre amp doesn't affect what the amplifier then does to the signal. JA - No, John, you only have to switch absolute phase at one location. Absolute phase is absolute phase. In your case the manufacturer will have maintained the phase integrity throughout the integrated amplifier. That doesn't an integrated amplifier doesn't invert absolute phase (which I belive your amplifier does not), but that the absolute phase issue is not a matter of what the amplifier and pre amp do separately. But, what switching absolute phase really deals with is the recording itself. Many recordings are out of absolute phase due to the numerous stages of processing equipment which are used in production. And before you jump on the absolute fidelity to the original signal, John, it only requires one piece of equipment to invert phase. If the mixing board inverts the phase at its outputs, the simplest two channel recording done with minimal microphone techniques can be thrown out of absolute phase. Of course the more important problem would be the numerous recordings where no real "absolute" phase can be deterimined due to the recording techniques employed. Nuck - I think you too are either confusing the issue of absolute phase and should read my comments to John. Or, you are offering a McGuffin which does not, in and of itself, further the story line. Which is it, sir? Back to MW, you have apparently confused tubes, solid state, hybrids, single ended and push pull. And the article you've linked to doesn't do a very good job of explaining away the confusion. The author writes only about single ended amplifiers. While the current marketplace invites triode based tube amplifers to join the ranks of SE's, any output device can be run as a SE output. At the present time, it just so happens that triodes are in flavor. "At the present technology, moving coil drivers will have much higher THD than any other electronic device in a system. ... And in our state of the art digital based system with a very low distortion amplifier most of the total system THD we will measure will be the loudspeaker distortion." This is the important statement to be garnered from this portion of the article. What is not important would be, "If there is more distortion in the system than in the speaker alone in most of the frequency range, just reverse the polarity of the connection between the amplifier and the speaker." This last sentence simplifies the whole operation of the system far too much and doesn't seem to take into account the many dynamic problems which constantly bombard a system playing music. While the author is obviously a well read and learned man, his attempts to justify single ended operation on the basis of THD is really a worthless endeavour in my opinion. I say that for several reasons. The most obvious is his solution to system distortion. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> "If the two devices are just equal, with the same phase relation between the distortion and the fundamental, the result will be a total of 2.0% of 2nd harmonic distortion. - A 30° difference in the relation of the 2nd harmonic and the fundamental between the two devices will produce a total of 1.93% of 2nd harmonic distortion. - A 60° difference will produce a total of 1.73% of 2nd harmonic distortion. - A 90° difference will produce a total of 1.41% of 2nd harmonic distortion. - A 120° difference will produce a total of 1.0% (exactly the same distortion as any of the devices alone) - A 150° difference will produce a total around 0.52% (about half of the distortion of any of the devices alone) - If there is 180° difference in the relation of the 2nd harmonic and the fundamental between the two devices the sum will be zero 2nd harmonic (yes that is right, in this ideal situation there would be NO 2nd HARMONIC DISTORTION)." >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Without getting into the author's exceptions which might occur when DC is present to disrupt the coefficient of his thesis, this work, while in certain circumstances, technically applicable, in real world terms is bull hockey. The only way to shift phase in such small increments is through laboratory equipment. No consumer audio device I've ever seen allows the user to shift absolute phase by less than 180°/ Additionally, the circuits which would allow such operation would obivously impose far more comlicated electronics than the author professes to prefer by stating his preference for the simple circuitry of SE amplifiers. So what exactly is the author's point? Actually, the most important issues to take from the article come much later in the writings. And, for all the verbage and mathmatics presented, these issues boil down to a few cogent sentences. First, "Each loudspeaker, depending on its efficiency and distortion levels will mate better with single ended amplifiers of corresponding different power ratings and distortion characteristics." And, "The values of the primary inductance of the output transformers usually can be smaller than calculated for a fixed resistor values if you are driving real world loudspeakers." Beyond those two statements, I cannot find any great value in what has been presented since the author dwells upon static measurements of a system which deals in dyanamic contrasts. His solutions to those problems are out of reach for the average consumer and negate his own stated preferences for simple circuitry. And, I would ask you to realize, the suggestion for altering phase applies only to SE amplifiers. And, as I have stated above, the issue of absolute phase in real world recordings is often a moot point since it does not exist. Finally, "The high output impedance can have several ill effects on a system, but if the system is designed taking it in account it will actually benefit from it. And certainly there are the cases where it just happen to "fix" a bad design." While everyone gets to adjust their system according to their own preferences, this sentence is merely stupid in my opinion. Using two poor designs in any attempt to "fix" a system problem is hardly the approach I advocate when building upon the strengths of the sysetm to achieve a synergistic whole. . |
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Gold Member Username: John_aLondonU.K. Post Number: 4423 Registered: Dec-03 | Quick response to early point, there Jan (will read the rest later). If everything is right "phase-wise" and yet you switch polarity to minimize distortion, then you will, as a consequence, be losing the correct polarity as far as phase is concerned. No? Perhaps I should read the whole of that linked article. |
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Gold Member Username: John_aLondonU.K. Post Number: 4436 Registered: Dec-03 | I've read it all now. It is a good and robust response, Jan. I appreciated that the guy was talking only of SE amplifiers. Again, my response was assuming the author had found another, independent reason (with an SE amp) to try the effect of switching polarity. My point is that you can only switch polarity once through 180 º. Do it a second time, and you are back in phase. Therefore, if you have correct absolute phase and then discover you get lower distortion from your SE amp/speaker combo by switching the polarity of their connection, your lower distortion will come at the cost of losing absolute phase. You might then bring it back by switching somewhere else, for example between source and pre-amp. All this does not make for undistracted listening to music. |
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Gold Member Username: NuckPost Number: 3506 Registered: Dec-04 | Jan, I did muddy the waters a bit, being Tube Noob, so I will simply retract, if I may. Joun, it does get further and further from the truth, though I do not know how 'dirty' this inversion actually is. I have flipped a coin 30 times and still come out with 2 bits. The inversion seems simple enough, it must be more complex than that. |