Wow. I've never before read anyone claim that double or half VOLTAGE = a change of 3dB. Of course, double or half POWER equals a change of 3dB, and double or half Voltage equals a change of 6dB.
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Why 24/7 warm-up period on amps?
The 24/7 warm-up period on amps seems excessively unsupported. Yes, an amplifier (pre-amp or power amp) will change it's circuit factors as the init heats up since the resistive and capacitive values stabilize...but for months on end? Do we still have a "warm" heart for tubes, that do indeed need to get "hot" to work right?
A capacitor charges up based on it's RC time constant, which is in the SECONDS range, not days. OK, if you add the heat sink area so the heat going out is stabilized I can see maybe an hour or so. My DNA-225 gets HOT in thirty minutes, at which point it's steady state. That even assumes it doesn't have temperature correction circuits to make it more stable, and less subject to change over time.
Break-in periods are hard to judge what people think is happening. Circuit P/N junction temps get hot pretty fast. A mechanical device like a speaker or phono cartridge, sure, they will work-in just like a well used rubber band. But silicone? Factory burn-in is designed to find weak components that degrade outside of SOP ranges, not to "center" their attributes in a normal stable circuit. Did someone forget to add enough heat sink compound to a PNP or NPN transistor, for instance?
Assumming break-in is real, not to be confused with the warm-up period, once it's done it's done. After that it would be warm-up only time. And, warm-up is a simple thermodynamic process. It only takes so long to warm-up and it isn't "days" on end. Maybe hours...if even. Once things are to temp the circuit constants are set. What else is changing? A heat sink is designed to warm-up and hold a delta temperature where the measured performnace is flat. A small amp (pre-amp gain stage) has smaller heat sinks for this reason. Heat and resistance are related, so you have to pick a temp and hold it. You design to THAT attrubute on the component.
Wire conditioning in the amp? ( go here - http://www.angelfire.com/ab3/mjramp/golopid/grain.html) As well as several other sites and textbooks.
The DC path is just that, DC. The magic is the purity of the DC, not the wire moving it around. You either have the right voltage and current capability (wire size)or you don't. Once the amp is on, the wires capacitance hardly matters. PP, PE or Teflon dielectrics only ionizes-tree and fail at break down voltages around impurities, not below that. You do not want to ever ionize the insulation in normal practice.
AC is an interesting issue. The AC complex signal is ALTERNATING differently at each and every frequency point, so the magnetic and electric fileds keep switching with respect to frequency. So the dielectric can not have polarity, or current "direction". The dielectric will not "align" to anything.
Grain structure in copper does not change unless you melt it. It's set when the rod is made. Annealing just resets elongation by improving homogeneous grain alignment, not the grain boundary characteristics since wire is resitive annealed at well below the temp that would fully reform the grain boundary around impurities in the copper. Oh, all modern 9/16" rod copper is made in induction ovens and is essentially OFC grade. All wire is drawn from that rod. Modern copper is also "high conductivity". Again, these terms are throw backs to days gone by with coke furnaces and open air annealing to critical temps where impurities could be picked up, changing the grain boundaries around impurities.
I also notice the people seem to tout TEFLON over Polypropylene or polyethylene dielectrics. Teflon costs more, it is higher temperature capable to 150C-200C (like 80C on polyethylene isn't enough in electronics) but Teflon has a worse dissipation factor and loss tangent. Using Teflon has a more NEGATIVE influence on electricals than olefins. Teflon's velocity of propogation at RF frequencies way above 1MHz is 70% verses 66% for solid olefin dielectrics. But that is at RF. And, you can nitrogen foam either to negate that advantage of Teflon at RF, but NOT Teflon's high price, loss tangent or dissipation factor. Capacitance adjusted Teflon is a poor choice. So the important factors are capacitance, dissipation factor and loss tangent. We can easily fix the velocity of propagation. PE and PP is superior across the board and cheaper (that's probably the problem!).
Good circuits are good circuits. Could you even make a circuit that had electricals parameters that were undefined till it ran, "forever"? Nope, can't be done. Design would then be a game of chance. I don't think that it is. Stabilized junction temps are used to set electrical componenet attributes with respect to temperature. You can design heat sink characteristics to place "hot" components where thet need to be temp wise to meet a circuit requirement. A poorly designed amp that allows thermal run-away under load isn't appropriate and isn't made...for long. There is indeed a circuit junction temp that rather quickly defines the measurable performance of the circuit, and a STABLE delta attribute approximation(s) when a circuit is designed. You know going in what they will be in operation steady state.
So, I hear my speakers and phone stage "break-in. And they don't go backwards once thet are broken-in. They can, in fact, get worse and simply break-down! But my amp sounds fine in short order. The circuit reaches a thermodynamic steady state and we're off to the races. I just can't see a circuit that needs 24/7 "on" period to stabilize...unless it just isn't stable. To me that's a poor design, and one subject to possibly serious load induced instability when the circuit falls outside of the stable design region(s).
I'd sure like to see MEASURED attributes that support 24 /7 warm-ups on sound. I have yet to see any measured data to support this. Show me components used in amps that take MONTHS to reach stady values. I have read PLENTY to support first to third approximation(s) on amplifier circuits ambient thermal temperature stability points. Many circuits are designed to run "cold" and have inverse circuit systems to keep changes due to temp deltas away. This way, you have a more stable circuit at all times. The opposite designis technically UNSTABLE till it gets to temp. This also limits what you can do as it can't blow-up when it is cold BEFORE it gets hot and stable. So the circuit is a compromise.
So just what are the resistive, inductive and capacitive break-in periods on quality components used in a circuit? In God we trust, all else bring data.- unknown
A capacitor charges up based on it's RC time constant, which is in the SECONDS range, not days. OK, if you add the heat sink area so the heat going out is stabilized I can see maybe an hour or so. My DNA-225 gets HOT in thirty minutes, at which point it's steady state. That even assumes it doesn't have temperature correction circuits to make it more stable, and less subject to change over time.
Break-in periods are hard to judge what people think is happening. Circuit P/N junction temps get hot pretty fast. A mechanical device like a speaker or phono cartridge, sure, they will work-in just like a well used rubber band. But silicone? Factory burn-in is designed to find weak components that degrade outside of SOP ranges, not to "center" their attributes in a normal stable circuit. Did someone forget to add enough heat sink compound to a PNP or NPN transistor, for instance?
Assumming break-in is real, not to be confused with the warm-up period, once it's done it's done. After that it would be warm-up only time. And, warm-up is a simple thermodynamic process. It only takes so long to warm-up and it isn't "days" on end. Maybe hours...if even. Once things are to temp the circuit constants are set. What else is changing? A heat sink is designed to warm-up and hold a delta temperature where the measured performnace is flat. A small amp (pre-amp gain stage) has smaller heat sinks for this reason. Heat and resistance are related, so you have to pick a temp and hold it. You design to THAT attrubute on the component.
Wire conditioning in the amp? ( go here - http://www.angelfire.com/ab3/mjramp/golopid/grain.html) As well as several other sites and textbooks.
The DC path is just that, DC. The magic is the purity of the DC, not the wire moving it around. You either have the right voltage and current capability (wire size)or you don't. Once the amp is on, the wires capacitance hardly matters. PP, PE or Teflon dielectrics only ionizes-tree and fail at break down voltages around impurities, not below that. You do not want to ever ionize the insulation in normal practice.
AC is an interesting issue. The AC complex signal is ALTERNATING differently at each and every frequency point, so the magnetic and electric fileds keep switching with respect to frequency. So the dielectric can not have polarity, or current "direction". The dielectric will not "align" to anything.
Grain structure in copper does not change unless you melt it. It's set when the rod is made. Annealing just resets elongation by improving homogeneous grain alignment, not the grain boundary characteristics since wire is resitive annealed at well below the temp that would fully reform the grain boundary around impurities in the copper. Oh, all modern 9/16" rod copper is made in induction ovens and is essentially OFC grade. All wire is drawn from that rod. Modern copper is also "high conductivity". Again, these terms are throw backs to days gone by with coke furnaces and open air annealing to critical temps where impurities could be picked up, changing the grain boundaries around impurities.
I also notice the people seem to tout TEFLON over Polypropylene or polyethylene dielectrics. Teflon costs more, it is higher temperature capable to 150C-200C (like 80C on polyethylene isn't enough in electronics) but Teflon has a worse dissipation factor and loss tangent. Using Teflon has a more NEGATIVE influence on electricals than olefins. Teflon's velocity of propogation at RF frequencies way above 1MHz is 70% verses 66% for solid olefin dielectrics. But that is at RF. And, you can nitrogen foam either to negate that advantage of Teflon at RF, but NOT Teflon's high price, loss tangent or dissipation factor. Capacitance adjusted Teflon is a poor choice. So the important factors are capacitance, dissipation factor and loss tangent. We can easily fix the velocity of propagation. PE and PP is superior across the board and cheaper (that's probably the problem!).
Good circuits are good circuits. Could you even make a circuit that had electricals parameters that were undefined till it ran, "forever"? Nope, can't be done. Design would then be a game of chance. I don't think that it is. Stabilized junction temps are used to set electrical componenet attributes with respect to temperature. You can design heat sink characteristics to place "hot" components where thet need to be temp wise to meet a circuit requirement. A poorly designed amp that allows thermal run-away under load isn't appropriate and isn't made...for long. There is indeed a circuit junction temp that rather quickly defines the measurable performance of the circuit, and a STABLE delta attribute approximation(s) when a circuit is designed. You know going in what they will be in operation steady state.
So, I hear my speakers and phone stage "break-in. And they don't go backwards once thet are broken-in. They can, in fact, get worse and simply break-down! But my amp sounds fine in short order. The circuit reaches a thermodynamic steady state and we're off to the races. I just can't see a circuit that needs 24/7 "on" period to stabilize...unless it just isn't stable. To me that's a poor design, and one subject to possibly serious load induced instability when the circuit falls outside of the stable design region(s).
I'd sure like to see MEASURED attributes that support 24 /7 warm-ups on sound. I have yet to see any measured data to support this. Show me components used in amps that take MONTHS to reach stady values. I have read PLENTY to support first to third approximation(s) on amplifier circuits ambient thermal temperature stability points. Many circuits are designed to run "cold" and have inverse circuit systems to keep changes due to temp deltas away. This way, you have a more stable circuit at all times. The opposite designis technically UNSTABLE till it gets to temp. This also limits what you can do as it can't blow-up when it is cold BEFORE it gets hot and stable. So the circuit is a compromise.
So just what are the resistive, inductive and capacitive break-in periods on quality components used in a circuit? In God we trust, all else bring data.- unknown
91 responses Add your response
here's the way it works almarg: i don't know your background and you don't know mine. that's fine with me because i don't care what you did in school years ago. that means that the basis for the credibility of any statements made here is the *substance* of our respective comments. if your argument has degenerated to an assertion of "just trust me" then i respectfully decline to do so... |
Paperw8, I repeat. With all due respect your continued insistence that db = 10log(V1/V2) is completely wrong. Please do some further research. I could perhaps further support the credibility of my statements by describing my academic and professional background, but we've already diverted the topic of this thread far enough. BTW, in case it's not clear, my statement that db = 10log(P1/P2) = 20log(V1/V2) obviously assumes that the load impedance is the same for all of the measurements. Regards, -- Al |
you were wrong when we discussed this matter earlier and you are still wrong. one of the problems is that people cite equations that they saw somewhere by rote without understanding what the equations really mean. look at the equation that you cited for power_dB: 10log(P1/P2) = 20log(V1/V2) the left hand side is a ratio of *power* levels while the right hand side is a ratio of *voltage* levels. power and voltage are 2 different things. the right hand side expresses how power levels change in response to changes in voltage levels. however, the equation that you cite is only correct when you are referring to a configuration where a voltage is being delivered to a load; there are other circumstances in which the equation that you cite is *not* correct (i explained that earlier so i won't go through that explanation again). so to give some context as to how the equation that you cite above really works, take a given voltage, v1, delivered to a load, z. the current, i1, through z in that case is: i1=v1/z the power delivered to z, p1, in that case is: p1=v1*i1=v1*v1/z=v1^2/z now deliver a voltage, v2, to z be described as: v2=(1/2)*v1 now the current, i2, through z is: i2=v2/z=(1/2)*v1/z the power delivered to z in this case, p2, is: p2=v2*i2=[(1/2)*v1]*[(1/2)*v1/z] p2=(1/4)*v1^2/z since: p1=v1^2/z p2 can be expressed as: p2=(1/4)*p1 so what this all means is when the voltage delivered to a load is reduced to one-half it's original value, the power delivered to that load is reduced to one-quarter it's original value. so to use the equation for dB we have: v_dB=10*log(v2/v1)=10*log(1/2)=10*(-0.3)=-3dB p_dB=10*log(p2/p1)=10*log(1/4)=10*(-0.6)=-6dB that's how this stuff really works: there is no magic where somehow -3dB corresponds to a reduction to half its original value when talking about voltage but magically -6dB corresponds to a reduction to half its original value when talking about power. |
Now that's funny. for any electronics, there is an inherent design life based on on-time usage. So, being "on" all of the time will cause components to fail sooner. For Solid State electronics, heat is the factor. Full output class A, well, this is really not a good idea to leave them on. For equipment biased lower, then it is better. But if all you are concerned with is listening, then turn it on and leave it on. For Tube equipment, well, every manufacturer that I am aware of says that there is a tube life and they recommend a warm up period but say that tube life is dramatically lessened by leaving it on. My tubed equipment cost a lot to retube and I definitely will not leave them on unused. Of course equuipment will sound better if it is warmed up in a constant manner by leaving it on. Until it fails. The really question is how much warm up time is required to where sound quality is noticeable? I found that 20 minutes to an hour is good for me. But others say 24 hours. There really isn't a generic policy. If you are aware of the issues associated with leaving anything on all the time, and you accept those issues, then go for it. Power costs notwithstanding. I typically turn things off when I'm not using it. enjoy |
Interesting points raised by Frogman. In my opinion music isn't, nor could it ever be, in an electronic component. Music is not the vibrations of a stylus, the pits in a CD or the flopping back and forth of a speaker cone. Music is something that happens purely within the brains of the musician and the listener. The mechanical/electric devices that are used to transmit and store musically information are in the realm of standard college level physic/engineering. Most of the scientific advancements in this area were done by telephone/movie/military researchers. That doesn't mean that we understand everything nor that we have achieved optimal implementations of what we do know. I simply mean to state that there are no great scientific mysteries in this area. If my assertion about where music occurs is true, then the standard audiophile course of seeking better equipment may not be the best path. Is it possible that we should be training our brains to better understand and appreciate music? I'm not exactly sure how that is done, but it's worth exploring. Mood altering drugs would be another path. While your amp is warming up, a few hits on the vaporizer or a swig of single malt would definitely open you up to a more emotional listening session. |
@Fripp1: the fine print on the "all amps sound the same" claim is "with the same input and output impedance and producing the same volume within their rated specs (i.e. not clipping)". Can't say I can test that claim as all the amps I've owned have had dissimilar impedances and wattage ratings. It would be nice to find energy-efficient amps that sound as good as my Rogues. |
***I know this is a crazy question but is it possible that the length of dissimilar conductors with varying dielectrical properties can have varying effects, positive or negative, in terms of introducing, eliminating, or altering interference?**** - Fripp1 I don't have the slightest clue. But your comment suggests something that is overlooked by many on the "numbers" side of the isle. We crave answers and explanations. But why are we assuming that we are asking all the questions that need to be asked? In my estimation it is short-sided and arrogant to think that established electronic-design standards address ALL that is going on in an electrical circuit. Is the science community not regularly discovering new things, and debunking previously accepted notions? Why should audio/electronics be any different? Add to this the fact that we are not talking about race cars or wine. The affected "product" is being asked to deal with the reproduction of an ART form. Complicating matters is the fact that we are talking about an art form that is not static (some visual art). Music is not only a constantly moving target, it has as a core ingredient the expression of emotion, and often involves the sonic result of human interaction. To think that numbers as understood today can be a complete picture of what can be going on in the electronic record/playback realm, and how that might affect our perception of it is silly. |
thanks for the power usage formula Al. had no idea my gear sucked up that much juice doing nothing. gotta say this is one of the most interesting threads i've ever read here. very impressive considering i can only comprehend about 50% of what you guys are discussing. spent 10x more time google-ing definitions then actually reading the thread, but i should have the remaining 50% nailed down by the end of the year =) fascinating stuff guys...thanks. |
09-13-11: Paperw8Paperw8, we had discussed the definition of db for electrical signals in another thread a while back, and as I indicated then, with all due respect you are simply wrong. Please do some further research, and I think you will see that: db = 10log(P1/P2) = 20log(V1/V2) where P1/P2 is the ratio of two powers, and V1/V2 is the ratio of two voltages. 6db is 6db, regardless of whether it is derived on the basis of power (where it represents a factor of 4) or voltage (where it represents a factor of 2). I should qualify my statement about 6db/octave rolloff for a first order filter, though, by adding that at frequencies that are just a small amount higher than the 3db point (Fc) the rolloff will be somewhat less than 6db/octave. As frequency increases further the rate of rolloff will become progressively closer to 6db/octave. The actual equation is: Vout/Vin = 1/(square root(1 + (f/Fc)^2)) During the first octave above Fc, a rolloff of about 4db will occur. As f increases further, the "1" in the denominator becomes progressively less significant, bringing the rolloff rate progressively closer to 6db/octave. Regards, -- Al |
Rower30. Brilliant stuff and I salute you. The whole issue of AC is fascinating to me. Many of us have reported that our gear sounds considerably better late at night and I am not convinced it is just the alcohol as I quit drinking many months ago and have experienced several fabulous late-night sessions since. There's no question that power demands and atmospheric conditions change as night settles in and could thus effect the signal in some (positive) way. I acknowledge that I do NOT use a conditioner but if I follow your argument, the power is undergoing transformation to DC within in given unit anyway so it *should* not matter. I've even had a guy with a masters in physics (teaches at a local community college) tell me that one amplifier is as good as another but I'm sorry, when I replaced an Adcom 5802 with a McIntosh MC402 there was simply no comparison. I know this is a crazy question but is it possible that the length of dissimilar conductors with varying dielectrical properties can have varying effects, positive or negative, in terms of introducing, eliminating, or altering interference? Before you laugh, I think of the radio antennae which, getting longer, pulls in a progressively better signal. Does an unprotected stretch of conductor automatically serve as a lightning rod for intereference (the notion of capping all open RCA does seem a bit over-the-top to me but...) Lastly, not throwing gasoline on the fire (or not wanting to ;-) ) sound coming through my best interconnects still BLOWS AWAY the sound coming through my low-grade ICs, ditto speaker cable. I mean, it's not even close. Power cords are a bit less dramatic a change (maybe I haven't spent enough money ;-) ). I've had to listen hard to hear a difference with the JPS Digital AC-X I'm auditioning for my CDP but I believe there is a qualitative difference, if a subtle one. It might even be worth $400. Like in politics we have people sitting on two sides of an aisle, but not everyone can be, or must be, a stubborn fool. Isn't it possible that we have people who really are capable of being objective listeners and who don't talk themselves into hearing differences that do not exist in reality? And can't they be sitting on either side of the aisle at different times? As in life, nobody is right all of the time and nobody "knows" everything. I always like the discussion, as long as it stays civil, as it's alternately informative and amusing. |
My solid state gear stays on 24/7/52 , can't argue the reasons why , but I've found large SS power amps definitely sound better , smother when left on continuously . The tube gear I've owned sounded ok after one hour of use . The power bill didn't change much going from tubes that were on part time to SS that was on all the time . |
I thought I heard a dissipation of the "solid state fog" from my Bryston 3B-SST when I left it on for more than a day. But it may be that Elizabeth planted that suggestion in my head. In any case, no amount of warmup makes the Bryston sound as good as my tube amps, which don't seem to need much warm up at all. The tube amps go off at night to conserve tube life. Even though it doesn't get very warm, the Bryston uses up as much power at idle as two 60W bulbs, and would you leave two bright lamps on all day and night? What would our parents say about such profligacy? |
the equation for dB measurement is: q_dB=10*log(q1/q2) where q1 and q2 are measured quantities and q_dB is the dB measurement for those quantities. when q1=q2/2, q_dB is -3dB. if you read closely the reference that you cited, you can see that what the writer is saying is clearly wrong. 6dB/octave is the falloff for a *second* order filter; the filter shown in the cited reference is a first order filter. |
oh, i see. my initial reaction is that you would have to have a reasonably large output impedance, but i'll think about this some more. |
rower 30 is correct, 3dB/octave is the figure of merit. frequency response charts measure a quantity (typically voltage) as a function of frequency. 3dB represents the point at which the quantity is reduced by a factor of 1/2. 6dB would represent a 3/4 reduction in the quantity. people look at 6dB when referring to power but that applies only to the situation where a voltage (typically an output voltage) is being delivered to a load. in that case, when the voltage is reduced by 1/2, the current is also reduced by 1/2 which means that the power is reduced by 3/4. but that does not apply in the case of a balanced input. in that case, you have a voltage divider, so when there is a 3dB reduction in voltage at a node, there is also a 3dB reduction in power at that node. take a look at a bryston schematic and you will note that they label the balanced input as corresponding to a 3dB signal reduction. the explanation that i just gave is the reason why. |
Paperw8, what Rower30 is referring to is the fact that the capacitance of a line level interconnect will interact with the output impedance of the component which drives the cable, forming an RC low pass filter. The "R" corresponds to that output impedance, not to the resistance of the cable. The bandwidth of that low pass filter can certainly be low enough under some circumstances to have audible consequences, if cable length is long, cable capacitance per unit length is high, and the output impedance of the component driving the cable is high. For speaker cables, on the other hand, that effect will almost always be insignificant, because of the very low output impedance of the power amplifier. Inductance and resistance may be significant considerations in the case of speaker cables, though, because of their interaction with speaker impedance. Regards, -- Al |
i don't quite understand why capacitance is of significance. yes, it is true that under the transmission line model, the wire induces signal delays that vary with frequency (i.e. distorts the signal), &c. but the transmission line model generally applied to signals that operate at microwave frequencies, not audio frequencies. as an example, resistance of audio cords is measured in tens of ohms per kilometer. so let's say that you have a cord with a resistance of 50 ohms/km; for a 1 meter cord, that means that the RC time constant is well into the megahertz range. what i don't understand is why roll off would even be a consideration in the audio frequency range. |
Lev, your amp's power consumption is specified as 650W in "on" mode (presumably under no signal conditions), 130W in "standby," and 10W in "sleep" mode. If it is in "on" mode all the time, that computes to 0.65 kilowatts x 24 hours per day x 30 days per month (approx.) = 468 kilowatt-hours per 30 days (yikes!). Multiply that by your kilowatt-hour rate to get the approximate cost per month. For the other modes, use 0.13 and 0.01, respectively, in place of the 0.65 factor. Best regards, -- Al |
09-12-11: Rower30Some minor factual corrections to your post: "3db per octave" should be "6db per octave" (at frequencies above the 3db point). Balanced cables don't necessarily have half the capacitance of single-ended cables. Besides the capacitance between the two balanced conductors, each conductor will have a significant capacitance to ground, via the shield and/or separate return conductor. In conjunction with the source impedance, that capacitance will also result in a low pass filter effect, reducing the voltage differential between the two signal conductors at high frequencies. See for example this datasheet on Mogami 2534, which in the popular balanced quad configuration has a higher capacitance from conductor to shield than from conductor to conductor. And the two wires are certainly not necessarily "twice as far apart." The idea is that noise pickup should be common mode (equal between the two conductors) to the greatest extent possible. Moving the conductors apart would work in the opposite direction. Also, as you probably realize, the 8pf and 17pf figures you cited will vary very widely depending on the particular cable design. Regards, -- Al |
Well, I see I lot of, "I thinks..." and no real data past typical steady state warm-up (maybe an hour). SS circuits are pretty immune to on/off transients so paying more in electricity than an amp cost (A DNA-225 is over $250.00 to $300.00 a year to run at 135 watts at IDLE!) over it's life seems wasteful. It seems funny to me everything in audio is better "hot", and no one seems to like it "cold". Circuits like to be COLD! But, you can't keep them COLD! So designers work around that and design to "hot". Then we get to a PC and enthusiasts we want to cool the heck out of it! Well, an amp is designed to reach a known temp delta and be linear in that range. It shoudn't take "forever" to get there. New KRELL amps run at virtually no power draw at sleep, so they can't be "on" all the time. Not anywhere near RUNNING steady state, anyway. But we all know how good KRELL amps are, right? Or any amp made to sleep. So past "brreak-in" a concept that shouldn't take too long (find the stuff that won't stabilize at the operating delta when cycled) the forever-on situation seems dubious at best. Yes, I know, we can pretend this is religion and just "believe" it. I'd bet a bunch of bucks that you can't hear the difference in an amp that's reached steady state temps and one that's been there a year. I'd like to do a blind test on power cords, too. Power goes all over the county on high voltage lines, step it down at ana xformer, goes through the house in 12-14 AWG ROMEX, through a gazillion dollar power cord that magically realigns the power (how it ever "knows" what it "was" when it left the plant I'll never know) and THEN goes into a CRAPPY IEC outlet, and THEN into the simple wires from the IEC outlet inside the amp to the power DC supply circuit block. Any decent DC block will turn all the AC to pure ripple free DC. If it doesn't, no power cord is going to change that. DC is like "white", there isn't anything there but potential to do work. No phase, no time shift, no frequency variation, just potential energy. Your best lead-in is the ROMEX from the wall! Run that right into your amp. Why make the AC get screwed-up through yet another passive lead? Active leads? Your power supply is agnostic to active leads as it spits out pure DC. Speaker leads are different, the amp is trying to pump a signal down a load that is trying to force voltage BACK into the amp! Hook a VOM to a speaker and move it and see what you get, a voltage, one that is apposing what's going in the speaker! Speaker leads help, or hurt the amps ability to deal with that back EMF characteristic. It isn't magic, the complex sinusoidal addition of the back EMF can distort the forward EMF and cause cancellations. SHORT leads make this less a complex circuit. So yes, speaker leads are the the MOST "hearable" leads in your system. High impedance interconnect leads? A precision 25 AWG mini coaxial cable with low capacitance is what you need. Nothing fancy, just good quality. There is (should be) virtually no real current in these leads. The lead is a first order filter (resistor and cap to ground), so the longer it is, the worse the roll off at high frequencies. Keep them short. Special "powered" leads? These isn't enough of an E field to scare a house cat at audio let alone "ionize" the dielectric. And, you better darn not have much of a magnetic field (current induced) or you input impedance is too low and it will swamp out you output amps. Remember, what's on the opposite side of your RCA is UGLY. But we forget what's inside the "box" don't we. Pre amp to power amp leads need low cap. too. Big ass copper does ZERO at the lengths we're talking about. The attenuation is NOT the problem in leads with no current (E=IR). There is no real voltage drop across the leads. What there is, is an increase in capacitance as the leads get longer (say bye bye to higher frquencies at 3 dB per octave at the filter fo frequency which drops as the leads get longer). So all the gold and silver on earth won't do anthing except take your money. What WILL help, is short LENGTH and low capacitance. Balance leads have HALF the capacitance as single ended RCA leads. The two wires are about TWICE as far apart, leading to LOW capacitance (about 8 Pf ft verses 17 PF/ ft). So the roll off is half the single ended RCA's roll-off. And, you get NOISE rejection added in for a bonus. I want to believe all sorts of stuff. But I don't. I can't seem to think I know stuff when I don't. I can hear every thing I said and 'show' you. A steady state amp is a happy amp, be it hot or cold. It just as to be steady state and designed around that temperature. Do you guys and gals even know how sloppy a typical PNP or NPN "junction" is is inside a transistor? And our beloved SOUND goes through all kinds of these devices? We can't readilly see it, so we pretend all the pretty stuff matters. So send me data on transistors that explains their phase, amplitude and gain changes with forever-on after steady state and I'll "listen" to that. I won't even get into resistors, which are terribly temperature dependant. So all the, I just know people can just know. That doesn't help anyone. The one's who really know, and have data they can point to, chim in. |
a lot (in fact, i suspect the great majority) of high end audio is sold to people who know little about electronics. so in some regards, the most important feature of high end audio products is marketing: because it is through marketing that you make the suggestions that influence consumer perceptions about audio products. you can convince people to believe just about anything with enough suggestion (e.g., a surprisingly large percentage of people still believe that saddam heussein was involved in 9/11). to the extent that people believe that there are sonic benefits from keeping equipment on 24/7, then that's just what they believe. however, other than for the possibility of bad system design, i see no scientifically valid evidence to support such beliefs. first, while it is true that the electrical characteristics of semiconductor devices does exhibit some thermal dependence, it is also true that semiconductor devices are characterized over a temperature range that goes from well below zero to well above boiling point. so i question whether there really is that significant a difference in the sound of audio electronics over the operating ranges of these devices. second, even accepting that there might be some audible difference in audio electronics during the "warm up" period (and, btw, the testing methodologies to evaluate this are *highly* unreliable), what really counts is the junction temperatures of the devices, not the ambient temperature that you feel when you touch the heat sink. the junction temperature would rise much more quickly than the ambient temperature, so i would expect the devices to reach their "warm up" within 15 or 20 minutes at most - not over a period of hours. i would find a more persuasive argument that the sound character of the speaker changed (for largely mechanical reasons) during the course of operation. as to the concept of "break in": the term, as audiophiles use it, is really a psychological process, not an electrical process. it reflects the time that it takes for you to get used to the sound of a new component. when you install a component in an audio system, it will likely have it's own sonic signature. when you first hear it, you will likely be very sensitive to the differences in sound relative to that to which you may have become accustomed. however, over time you will get used to the sound and will become less sensitive to it. as an experiment, change the loading and/or gain on your phono stage. depending on how much of a change you make you should observe a noticeable difference in sound. if, for example, it sounds too bright at first, over the course of time, and as you get used to the sound, you may perceive that the sound is less bright. you've just done audiophile "break in" on an existing piece of audio equipment... |
Almarg, you beat me to the punch. That is exactly right. I was going to point out that I have owned a couple of amps over the years (Moscode 600, B&K something or other) that after being on for more than 24 hours, exhibited negative effects. The sound would become not just overly dark and thick, but strangely uninvolving (the Moscode in particularly). Nonetheless, others that I have owned really hit their stride when left on for long periods of time. |
I would just add to what has been said the thought that if there are in fact mechanisms by which warmup beyond the point of thermal stabilization can produce audibly significant changes, I see no reason to expect those changes to necessarily be for the better. And I would certainly expect both the magnitude and the character of the changes to be dependent on the specific design. Regards, -- Al |
I was always skeptical keeping an amp on 24/7. If I were listening over the weekend I would leave it on otherwise turn it off if not listening for a few days. I do however think an amp needs couple of hours warmup to sound better. I also think an amp sounds better after a 24 hr warmup. I noticed this on a couple of occasions with a BAT VK-200 I used to have. It just sounded better or more refined after being on for 24 hrs. |
I think the OPs question is whether there is reason to think 24/7 provides an audible improvement over a short (say 1-2 hr.) warmup. I suspect many of us, OP included, would say they hear large differences with a short warm up. But I think it be hard to do a reliable A/B on the 24/7 v. short question, given limitations of "acoustic memory," and barring having two identical amps on hand. So it might be suggestive to know if there were differences in measured attributes to support (or not) conclusions drawn from acoustic memory. There is, of course, a practical -- if not environmental! -- reason to go 24/7: your amp is always warmed up, so it's playing best whenever you listen, even if your listening sessions are unpredictable and/or short. John |
Here is except from the Aleph 2 users manual: This amplifier runs hot. The heat sinks will warm up in about an hour to a temperature which will not be comfortable to touch for more than a moment or two, which is 120 to 130 degrees Fahrenheit (50 to 55 degrees Celsius). This is normal, and there is a thermal shut off system which will shut down the amplifier at internal temperatures in excess of 160 deg. F. and 70 deg. C. It takes at least an hour of warm up time to get the best performance out of the amplifier. It will take that long to reach operating temperature and exhibit lowest distortion and noise. This is not a subjective judgement, but based on actual distortion and noise measurements. You may find somewhat greater residual noise coming through the loudspeaker when the amplifier is first turned on, but it will decrease as the amplifier warms up. The amplifier does not require any maintenance. While the design is conservative, this is a hard running amplifier, as single ended Class A operation is the least efficient operating mode. In fifteen years the electrolytic power supply capacitors will get old. Depending on usage, you will begin to have semiconductor and other failures between 10 and 50 years after date of manufacture. Later, the sun will cool to a white dwarf, and after that the universe will experience heat death. |
Rower30: very interesting read. wondering what everyones thoughts are regarding the "stand by" option some amps have available (like my ml432). the owners manual does recommend 24/7 but states "stand-by" is a few minutes warm up time away from 24/7. only tried full shut downs a couple of times and it didn't sound good for quit some time (approx 1 hour). it was an option i didn't look too closely at because i listen almost daily and 1 hour seemed way to long. stand by mode takes about 15 minutes to get there but in all honesty...i didn't spend that much time comparing (24/7 vs stand by vs full shut down). my pass x-1 is on 24/7 by design and specifically says to leave it that way. have never really thought about this topic before so hearing what you guys think would be great. |
****I think so many of these issues are a divide between folks who try it and find it works, and folks who just refuse to accept that it can work.**** - Elizabeth A rough count reveals about 90,000 threads on this forum. I think an average of 30 posts/thread is probably a conservative guess. That's upwards of 2,700,000 posts!!!! (Is that possible? Someone please correct my pre-coffee math). I can't even begin to fathom how many words that might add up to. Amazing how much can be said with few words when stripped to the basics. Bravo, Elizabeth. |
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Great post some valid points. But to be fully informed call 1-800-Nelson Pass. Or viisit www.passlabs.com he has many white papers with the info you seek, some going back several years. Of course it helps if you can communicate with him on his level. But nonetheless a worthwhile conversation to have if you can keep up. As far as the 24/7 information. Yes amps due tend to stabilize with 2 hours or so after initial power up. In solid state amp and in particular Class A amps the conatant cycling through on/off tends to shorten their service life. Many times in Pass designs the power switch is difficult to get to such as in the ALEPH series of amps. He doesn't want the end user to continually send these amps through needless cycling. Some weeks ago I responded to a similiar thread. I recalled that in high school many, many, many years ago, out science teacher was conduting a test involving a simple light bulb. At the time I was in his class the constant on bulb had burned without interuption for I think three years or so, while putting other bulbs through the on/off cycling of which at that time he had gone through 7 light bulbs. When I left high school some three years later the constant on bulb was still burning bright. While visiting the Thomas Edison winter home in Ft. Myers, FL., we were informed that many of the light bulbs in that home had some 60 years of service and still going strong. Although the actual light output of each bulb was about 25 watts and the fillament inside the bulb was indeed very heavy quality and I think someone said the fillament was made of bamboo? Hmmmm strange, I haven't followed up on that. Ever get a chance to visit I do recommend to see his home and across the street is his working laboratory preserved as he left it. |
