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Gold Member Username: DmitchellOttawa, Ontario Canada Post Number: 4631 Registered: Feb-07 | What it means when a tube goes "microphonic". Last night I started getting a weird hum out of one of speakers. At first I thought "oh sh!t, the new DAC is defective" but I turned the DAC off and the hum was still there, so then I thought it was the input, so I changed that, but hum was still there. The hum was a weird kind of hum... not like a ground loop hum, but more echo-y, if that makes any sense. So then I started gently tapping on each tube, and low and behold, one of them would make a really weird "ping! echo ehco ehco..." sound. Even tapping on the audio rack would be picked up by the tube. Turns out it was one of the ancient 6414 splitter tubes that Manley uses. Good thing I had a replacement - the joy of tube amps.... no comment from the peanut gallery, Nuck. |
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Platinum Member Username: Jan_b_vigneDallas, TX Post Number: 15815 Registered: May-04 | . "Even tapping on the audio rack would be picked up by the tube." Now that you've replaced the tube, what else should you be doing? . |
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Gold Member Username: DmitchellOttawa, Ontario Canada Post Number: 4633 Registered: Feb-07 | Listening to music? |
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Gold Member Username: DmitchellOttawa, Ontario Canada Post Number: 4634 Registered: Feb-07 | Just kidding. I guess isolating the amp from the rack would be a good call. Or are you suggesting upgrading the rack? |
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Gold Member Username: SuperjazzyjamesPost Number: 1312 Registered: Oct-10 | I had a pair of Scott® mono integrated tube amps, 35 watts each back in the 80s. Never had that happen. Many people I know have or have had tube amps and never mentioned such a thing. Any idea how that happened? It certainly is a weird phenomenon. |
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Platinum Member Username: Jan_b_vigneDallas, TX Post Number: 15819 Registered: May-04 | . You can safely assume all tubes to be microphonic to some degree. And you might as well assume all solid state compnents are subject to some level of microphonics also. If you heard the effects of the rack when it was quite obvious the tube was defective under those conditions, then you can also assume all the components are being affected by the microphonics within the rack; i.e, the rack is allowing information not present in the original signal to reach the components resting on the rack. This rack generated signal is out of phase with the original signal from the component and the more mass employed in the rack, the more out of phase the arrival times tend to be as mass holds information in a non-linear manner. This presents yet another common audio trade off in that you want some degree of mass to make the system stable and to act as a drain for any vibration which might enter the rack system yet you also want the rack to be extremely light and rigid in order to effectively release any information within the rack intact with what is present at the component. You can either address the entire rack as a system and begin by further isolating it as a whole from any energy which might be transmitted through mechanical or airborne vibration (don't forget the airborne) or you can address each component individually. Amplifiers - and tube amplifiers especially - are prone to requiring a fairly effective support system which drains away any mechanical vibration introduced by the power transformer by way of spikes, rollerballs or the like. This is, of course, experimentation and what works for your set up might not be spikes, rollerballs or the like. Suck it and see what comes out is the way to go here. This drain effect is typically accomplished by using the support shelf/stand as the drain and mass or physically coupling the two pieces together. Then you need to decouple the amp from the support shelf and/or the support shelf from its support in order to minimize any microphonics generated by the entire support system. Simple, eh? I'd start by removing the amp from the rack and placing it on something like a few thick telephone books on the floor. Or remove amp from the rack and put it on the floor supported by a couple of halved racquetballs. Make sure you have good ventilation and listen to the results. If there's an audible improvement in clarity, then you need to do something about the rack/amp situation. . |
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Gold Member Username: DmitchellOttawa, Ontario Canada Post Number: 4635 Registered: Feb-07 | "You can safely assume all tubes to be microphonic to some degree." Yes, I noticed that last night. Actually, everything you describe here makes perfect sense. I even have an amp stand here that's a thick slab of wood that sits on the floor courtesy of Nuck. I *could* try that, but the reality of it is that my kids (and worse - their friends) play in the same room. There's no way I'm sitting a tube amp on the floor. It doesn't take much imagination to picture how badly that can turn out. Once my music room is done, then I really start experimenting. |
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Gold Member Username: MagfanUSA Post Number: 2065 Registered: Oct-07 | SS microphonics? Can you explain a mechanism? Tubes, when any of the internal elements are shaken can modulate the signal, but SS? No moveable parts. And if so, to what degree? Maybe caps if you subject the piece to enough vibration? |
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Platinum Member Username: Jan_b_vigneDallas, TX Post Number: 15823 Registered: May-04 | . Let's start by getting ourself on the same page. In your opinion, why would caps be microphonic? What about resistors? Most caps have some resistive value and most resistors will have some capacitive value. A passive crossover in a speaker is just that, passive. If you remove it from the high pressure area inside the cabinet and place it external to the speaker enclosure, what would you expect as a result? . |
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Gold Member Username: MagfanUSA Post Number: 2066 Registered: Oct-07 | Jan, what page did you have in mind? No mention is made of this phenom in my Semiconductor Technology Handbook....what we called the 'sand to silicon' book. Caps are not homogenous. Layers of softer material interleaved with metallic layers. Variations in pressure, which even exist inside speakers may cause variations in capacitance value as the cap is alternately compressed and 'rarefied'. I am not saying WOULD, I am saying COULD. I don't know how current 'metal film' resistors are made. The 'old' carbon resistors were pretty uniform inside. I don't know how rapid and slight pressure changes effect resistivity. Off hand, I can't think of HOW a resistor could be microphonic. I also just don't see how SS.....basically SOLID materials..no matter how fabricated, could vibrate and have changes in values which would cause changes in sound. No 2 parts of either an integrated circuit or discrete device are in a similar relationship to that found in tubes, where various metal conductors are suspended in a vacuum and easily subject to vibration and therefore movement from external sources. Implants are diffused into the silicon. and the other layers...Polysilicon, Metalization and various LTO / Silicon nitride passivations and interlayers are all stuck down pretty good. In fact, flaking layers are heavily discouraged and parts exhibiting same are called SCRAP. I'm not saying SS is NOT microphonic, either. I just want a mechanism explained or postulated. |
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Platinum Member Username: Jan_b_vigneDallas, TX Post Number: 15825 Registered: May-04 | . I doubt looking in your Semiconductor Technology Handbook would provide many answers to a wide range of audiophile practices. This takes us back to a link I posted in the time and phase thread; http://www.stereophile.com/thinkpieces/165/index.html and the quote, "If only it were so simple. Jim was a classic example of what happens when Physics 101 goes to your head. Yes, Ohm's law, exotic theories in quantum mechanics, and other laws of physics go a long way toward explaining a circuit or a silicon chip. Last time I checked, however--and Jim never did--there is a huge gap between our theories of electrons, wires, and chips, and how equipment actually sounds. Audio involves physics, but also chemistry, biology, psychology, psychoacoustics, and even those misty heights of abstraction called aesthetics. Physics and other hard sciences are just one part of that big pie. Sorry, Jim, but physical principles do not tell us everything we need (or would like) to know about audio." Again, as I paraphrased Kloss in that same thread, ""Of course it's research. If we knew what we had found, it wouldn't be called research any longer." So, before I answer your question, leo, (and I will answer your question or at least let you know when we are in agreement or disagreement) how about we think for awhile longer? As a researcher would you consider yourself to be a theorist or an empiricist? http://www.stereophile.com/content/scientists-ivsi-audiophiles-1999-reisch-repli es From the above, "But there's not much camaraderie in the world of audio. Too often, audio engineers (who uphold theories about what things should sound like) and audiophiles (who care mostly about what things do sound like) don't even acknowledge the other's point of view ... Pro audio magazines should follow suit. Ethan Winer's "Dispelling Popular Audio Myths," in a recent issue of Audio Media (April 1999, p.95), ought to appear in the dictionary next to "myopic." He writes, "Myth: Using audiophile speaker cables improves the sound, compared to an equally heavy gauge of normal electrical wire." Never mind that "normal electrical wire" and "audiophile speaker cables" are never defined. Winer focuses on damping factors, impedance, and capacitance, but writes not one word about listening to or comparing cables. Hello? This alleged myth is about sound--an empirical phenomenon. Winer assumes he can refute it exclusively on the basis of electrical theory." (You might remember the name here. I mentioned it during the discusssion with Andre and why I didn't prefer to send him to the RealTraps webpage.) . |
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Gold Member Username: MagfanUSA Post Number: 2068 Registered: Oct-07 | Can everything heard be measured? no. not at this time. Can everything heard eventually be measured? probably. Are SS devices microphonic? probably not, but I'm open to even an unproven or currently unprovable theory. A theory should be capable of predicting currently unknown behavior and extrapolate from currently known and measurable phenom. A theory or good description of SS microphonics should be able to make some predictions as well. The investigation or discovery of something new always starts with a question. I enjoyed parts of the stereophile link. The letter from G.Emory Anderson was particularly lucid. |
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Gold Member Username: MagfanUSA Post Number: 2069 Registered: Oct-07 | http://www.madisound.com/pdf/claritycap/MRWhitePaper.pdf A white paper issued by Clarity....touting the virtues of the MR series of hi-end capacitors. The resistive and inductive nature of capacitors is noted and some 'cures' as well. The microphonic nature of film caps is also investigated. Since data was taken and is herein published, along with the methodology, I would have to believe that anyone with sufficient resources could duplicate this experiment and confirm the result. |
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Platinum Member Username: Jan_b_vigneDallas, TX Post Number: 15829 Registered: May-04 | . That's good information, leo. Caps in particular have over the last few decades received a good deal of research and subsequent re-evaluation of existing beliefs regarding their infuence on sound quality. Most often this type of research has been led first by the empirical concepts of observation first and asking, "Why?", next. Possibly you can see similarities between the construction of a cap and the construction of a cable. Cables easily exhibit microphonic responses similar in type to those described in the ClarityCap paper. Attach one end of a cable to a scope and bang sharply on the cable with a rubber mallet and you'll see the spike in signal which is created within the cable itself. "A theory should be capable of predicting currently unknown behavior and extrapolate from currently known and measurable phenom." IMO it's important to remember that many of the truths we prefer to believe are themself grounded in "theories". Gravity is still just a theory and physicists are working on the "what if" of anti-gravity. Research is still research and only if you begin the research by knowing what you're going to find is is not research. Of course, presenting a single equation representing the impedance of the cap's equivalent circuit doesn't necessarily make the equation a fact. But the empiricist oftentimes begins with the observation and proceeds from there to an probable solution. If we stick with the empirical methodology for awhile, let's explore what others observe or claim to observe when treatments of various types are applied to electronic components. We'll begin with Nordost, a high end manufacturer with quite a reputation. They are consistently amongst the most favored cables and products in the subjective review press but they are also the generic cable most referred to by cable/tweak naysayers who always pull out that mythical $15k cable that just can't be worth that sort of money. Keeping in mind we are back to presenting manufacturers' papers and manufacturers' papers are intended to promote those ideas the manufacturer wants you to believe and ultimately buy, here are a few of the things Nordost promotes and why; http://www.nordost.com/downloads/Sort%20Kone%20Instructions.pdf http://www.nordost.com/downloads/Foundation%20Theory.pdf http://www.nordost.com/downloads/New%20Approaches%20To%20Audio%20Measurement.pdf Notice Nordost not only feels the mechanical energy of the signal passing through components has a negative effect on the signal quality but more importantly they include the electro-magnetic influence of constantly expanding/collapsing magnetic fields of each component part plays an important role in the quality of the signal from input to output. It's long been understood the EMI generated by, say, coils and transformers needs attention paid to the negative effects on the other components and in each coil or transformer used in a circuit. Now that effect is being more clearly understood in the very small alterations to the signal in other components. Adding up the mechanical resonances of the caps and those of the internal cabling along with the interconenct cables running between each component and their attendant connectors alone could present a reasonably large degradation of the singal quality from the in to the out of a component. Add existing mechanical resonances created by the inclusion of a digital transport and the problem is growing like Topsy. Staying with the issue of EMI it's clear a component is not only subjected to the internal procreation of EM fields but also from those existing fields from outside the component. Taken together we find another favorite for the "snake oil" shouters, the Shakti Stone; http://www.shakti-innovations.com/audiovideo.htm The Stone is an intersting device IMO in that even when you point the naysayers to the tests performed in the "automotive/dyno tests" section of the webpage, where the stone showed an objectively measureable improvement in performance outside the subjective world of high end audio, they still prefer to ignore those facts and claim the Stone is pure snake oil inflicted on the idiot audiophools. Leo, have you ever had the experience of measuring the quiescent noise of an electronic component within an electronic lab? Have you ever tried to measure the noise within the lab and then outside of the lab where the combined EMI of all the equipment within the lab might influence your final result? At yet another level of theory is Geoff Kait's Machina Dynamica products, the Promethian base and the Nimbus system; http://machinadynamica.com/machina25.htm and http://machinadynamica.com/machina24.htm Geoff's an interesting fellow who has long been a favorite target of the naysayers and snake oil shouters. He has had a long running fued with The Amazing Randi as has M. Fremer. Any search engine can fill you in on the details. Kait offers out of the ordinary products - even for the subjective high end audio market - and explains the theory behind a few of them in his not altogether serious webpage. Before you make up your mind regarding Geoff's products you might want to try one of his products, they all come with a 30 day return policy. Lastly here, consider the mechanical connection points between each component part of a circuit board. Each cap and resistor, at a bare minimum, will have flexible leads which have oftentimes been soldered in place to the component and then to the board. As each component part is mechanically or electrically excited into movement/microphonics those leads tend to act as diodes as they flex not in sympathy with the cap or resistor but in their own flexible way as captured betwen the component and the board. This leads many observers to conclude each mechanical connection point in a circuit will have a noticebale effect on sound quality not due simply to the complexity of the circuit but also due to the influences of each "diode effect" on the signal transmission through each individual component part. How much of this is actually noticed by the listeners is a matter of subjective opinion in most cases. But observation can lead to experimentation and finally a theory of operation. It is the effort of the high end audio industry to continue towards greater and greater transparency to the source. Many of these observations noted above have been made with the SOTA systems and then brought down to the point where they no longer make any difference due to the inability of the components to uncover the very small distinctions is signal quality. In other words, your Pioneer HT receievr probably isn't going to be transformed into a giant killer just by the addition of a Shakti Stone or a Nordost cone. . |
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Gold Member Username: MagfanUSA Post Number: 2072 Registered: Oct-07 | Just a quick reply...than off to classwork. Next semester starts tomorrow and I've got some prelim work to do. I need to build something 'with a door and a drawer'. By this time next next I hope to be building something for my research. Anyway, All those effects and things going on reminds me of a methodology to fix problems in a factory. If you treat all the effects noted above in such a fashion, it may help to put them in order. You have 4 classes of manufacturing problems....and the attendant solutions. Big effect and Easy to solve:: You generally start here. This is called 'low hanging fruit' and yields good improvement for minimal effort. Basic housekeeping type things are in this category. Defective components, poor/noisy power and optimum physical setup are perhaps all in this class. Big effect....difficult to solve. this may take some time and require investment in facilities or training or both.....But the results are big and probably worthwhile. Someone with a square or cubic room may be in this class. Or maybe even someone who has put together a system and it is simply incompatible even if composed of 'best in class' pieces. Maybe 20 tube watts and Magnepan. Small effect....easy to solve. You implement these solutions because they ARE easy. and usually cheap. Return on investment is minimal but real. Toe the speakers in more or less. Move 'em in or out from the wall. Buy some artificial ficus trees as diffusion. And finally, the last category. Small effect and difficult to implement. These are the last, most difficult problems to solve. Minimal influence, but if you want the very highest yield (OR SQ), this is the what you need to do. A total acoustic design of a room falls in this category, maybe. Or perhaps the search for the 'perfect' cable or power cord. So, where are we in Audio? Have all or even much of the low hanging fruit been picked? Does anyone have a system so evolved that tiny improvements are either technically not feasible or simply too daunting financially....and this for some pretty deep pocket types? Off to drawing board. |
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Platinum Member Username: Jan_b_vigneDallas, TX Post Number: 15830 Registered: May-04 | . Four categories to tackle but you've not indentified the "finding the problem in the first place" phase. While cables are still a point of contention in some forums it wasn't until a few decades ago that anyone even thought of using more than heavy guage zip cord. |
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Gold Member Username: Stu_pittStamford, Connecticut USA Post Number: 4346 Registered: May-05 | David - Have you considered a wall shelf? The ones that are used most commonly for turntables. That'll keep it off the floor. Obviously replace the bad tube. |
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Gold Member Username: DmitchellOttawa, Ontario Canada Post Number: 4652 Registered: Feb-07 | Bad tube replaced. I guess a wall shelf is ok if it can be mounted on the wall studs. |
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Gold Member Username: MagfanUSA Post Number: 2074 Registered: Oct-07 | I'd say most urges to change or improve something starts as either an observation or question. The fuel? Curiosity and desire. For the time being I'll leave greed alone. This usually leads to 'the solution in search of a problem' and is perhaps the 3rd rail of you-name-it. |
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Gold Member Username: Stu_pittStamford, Connecticut USA Post Number: 4347 Registered: May-05 | Wall shelves are supposed to be mounted into wall studs, if I'm not mistaking. Now that you've replaced the bad tube (after it's been burned in), give the rack a little nudge and see what happens. If you've got a tuning fork, hit the fork, then hold the tip against the chassis of the Stingray and see what happens. Just thought of this stuff now. Seems logical to assess if vibrations are causing problems. I'm sure my rationale is flawed and Jan will intervene. I say that in a good way. |
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Platinum Member Username: Jan_b_vigneDallas, TX Post Number: 15843 Registered: May-04 | . Yeah, whenever possible wall brackets go into studs on load bearing walls. Hollow wall anchors are a second choice but do not provide the stability of wall studs. I'd say it's just good practice to assume vibration is getting to the amp but anyway that informs you is useful. Just for experimentation setting the amp on a few squishy balls like you squeeze for stress relief is fine but usually not a permanent solution. The basic Vibrapods are very cheap and are effective. . |
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Gold Member Username: DmitchellOttawa, Ontario Canada Post Number: 4655 Registered: Feb-07 | Had a near disaster last week with some hollow wall anchors. Center channel almost took a tumble onto my plasma. Nothing a little PL Bulldog grip wouldn't fix. |
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Gold Member Username: DmitchellOttawa, Ontario Canada Post Number: 4656 Registered: Feb-07 | New 6414s on the way too! |