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I just bought a new Denon 2808ci. It replaced a Denon 3805. While I like a lot of the new features of the 2808 the sound seems to be lacking. I've seen elsewhere mention of break-in periods for electronics. Do receivers have a break in time?

I could see how one could theoretically "break-in" since the heat from the system will expand and shrink capacitors and whatnot. I think the same process is what utterly kills the receiver eventually.

I also know that comparing the 3805 to the 2808 is like comparing apples to oranges in a way. I thought the Burr Brown PCM-1796 (2808ci) was supposed to be better than the older PCM-1791 (3805). Although the 2808 has one per channel and the 3805 has two. I'm sure there are other factors in the amplification stage too.

Chime in if you think I've got it all wrong.
 

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I have heard of so called break in periods for some equipment, not particular receivers, but amps. However, I personally think it is a myth.

I owned a 2807, 3805 and 3806. The only one I was not pleased with was the 2807, but I'm not sure what to contribute it to.
 

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Discussion Starter · #4 ·
I posted in error that the 2808ci uses the Burr Brown PCM1796. I actually uses the Texas Instruments Burr Brown DSD-1608.

I've managed to tweak the 2808ci so that it sounds close to how I had my old 3805 setup. The Audissey MultEQ XT did not do a very good job of setting the subwoofer and center channel levels. I think the surround processing is a little better on the 2808 and my favorite movie/scene of choice, LOTR: Bridge of Khazad-dûm, the arrows seemed to come alive. That may be the Audissey MultEQ earning it's room and board.

I still miss my 3805 and will probably look at ditching the 2808ci and grabbing a 3808ci if I can get a good price selling/buying each.
 

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The answer actually is yes, but it's so slight that the best instruments would likely not measure it and your ears certainly wouldn't. Maybe that makes it a No.

I expect the Audyssey probably did an excellent job of setting your sub and center levels, but it's not unusual for a user to want more center channel volume and more sub volume. What Audyssey typically does is knock down some room modes and flatten out "room gain" below about 100 Hz. The result seems to be weak bass but in fact it's just down level with the mains where it belongs, at least as a base line. If you like more bass, by all means crank it up. Some receivers have decent tone controls that do a better job of matching the ear's nonlinearities than you will get from pushing the sub volume up. The ears interpret low frequencies at typical home listening levels (85 db peak) as being 6 db lower than the same frequencies when played at theater levels (105 db peak). To offset that you want a low-end boost that adds 6 db at 20 Hz and less at higher frequencies, tapering to zero at about 150 Hz. Bass tone controls that center at about 30Hz do that fairly well. This applies to movies that are intended for the theater but end up on DVD and played 20 db lower than intended. For music you probably don't want quite that much bass boost.

As you get older (50's and above) you lose the ability to pick voices out of background noise (sound). That's when you REALLY want that center cranked up.

Harrison
 

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The post above is an example of the kind of comment that does not add to the discussion in a meaningful way and could inflame the kind of arguments that get started on other forums with regard to such matters. While many will agree, including myself, that there is little or nothing to be gained by "burn-in" in receivers, the point can be made in a more productive manner that is conducive to civil discussion.

There are indeed many components that do chnage with time. I have yet to see any documentation that recievers are subject to significant changes over time that affect sound output. It would be great to see some measurements that document what some people claim to hear but to my knowledge, no one has done any testing of this sort.

Capacitors and semiconductors do change performance with time and temperature in many cases. This is likely to be the case more with electrolytic capacitors than any other component type, but the kinds of changes that might occur with a burn-in period are unlikely to affect sound quality. Over time, changes may actually detract from performance. There is more likely to be a warm-up period in amplifiers or receivers over which time the performance may improve, but this is likely to be limited to units with very large power suply caps and mosfet output devices. The latter have an optimal operating temperature and will often perform better when warmed up.

As with most matters of debate in our industry, the idea of burn-in starts with some truth and facts that get spun out of context or to extremes based on assumptions, anectdotes, and expectation effects. Putting them in the right context requires more than simply crying "snake oil." I am sure you have more useful contributions to make, Capt. Kaboom, and I encourage you to do so. Please understand, however, that while your opinions are welcome, we are very careful not to allow carping to start the kind of infantile arguments you might see in other forums. If you want to state your opinion, make a case for your ideas rather than hit and run posting.
 

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My personal feeling on this is simply everything has some sort of break in period the issue is more, can you hear a difference after the break in time has come and gone? Electronics are always heating up and cooling down to say that this wont cause any change is just plane ignorant but the changes are usually not audible.

As Leonard stated above "Capacitors and semiconductors do change performance with time and temperature in many cases. This is likely to be the case more with electrolytic capacitors than any other component type, but the kinds of changes that might occur with a burn-in period are unlikely to affect sound quality." This is still break in but it just wont affect the over all performance of the AV equipment.
 

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In my earlier thought on the matter of break-in, I was neglecting warmup and aging. I agree both could change performance far more than break-in. Especially warm-up. Maybe not meaningfully to my ears, but maybe to some.

Hence I would think one concerned with break-in would be more likely to detect the warm-up period in large amplifiers. Amp service manuals say to make the bias and dc offset adjustments only after some period of operation, maybe 30 or 60 minutes (I don't recall). I think the biggest reason is the uncompensated bias and load balancing resistors in the power transistor circuits that probably change resistance measurably from room temperature to operating temperature. If there's a reason to wait for them to warm up before making adjustments, there must be an audible effect. I've never measured bias or dc offset on a cold amp, so can't guess at the change.

Aren't electrolytics almost lossless? I would think if they change it would be from the heat thrown off by the nearby transformer and rectifiers. If they measure more or less capacitance after warming, one would experience more or less regulation in the power supply. That might come through at low frequencies when an amp is driven hard. The inductance of an electrolytic (affects high frequency performance) probably isn't affected by temperature (?) and so is probably not an issue. The question is whether capacitance increases or decreases with temperature in an electrolytic.

Heh, more questions than answers. :) But, I do think I'll warm up my system before showing it off the next time.
 

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Hey, I sure don't have all the answers, but as we discuss the questions, we usually learn something.

I am not sure what you mean by lossless, but I have never heard electrolytics described that way. There are four (or more) major characteristics that are typically attributed to capacitor behavior, most are affected by time and temperature. First is capacitance. This can vary somewhat with temperature and there is a "forming" period necessary to achieve rated capacitance, but this is usually done at the factory. After long shelving, it can be required. Then there is ESR (effective series resistance). This is the resistance to passing signals, usually measured at frequencies in the tens or hundreds of kHz. This varies with temperature, frequency, and age. This is a factor in switching power supplies and for passing high frequency signals and noise. Then there is d.c leakage, which is the amount of constant current that passes or leaks through, which should be very small. If it is rather high, temperatures rise quickly, affecting other parameters, and probably eventually causing failure. Finally, I will mention dielectric absorbtion, aka battery effect. This is the tendency of energy to be held in the dielectric for an extended time. When a cap is discharged and the voltage across its terminals rises again with time, this is DA. All aluminum electrolitics do this to some degree, but most will have levels well under 10% of the charged voltage. This is a rather messy parameter, as it seems to be somewhat higher in some of the better caps on the market (in terms of impedance and life specs) but can cause some strange behavior in some circuits. It can also be affected by time and temp and the effects can be rather unusual when it gets too high. A classic issue with DA is in poorly designed DACs, where settling times are an issue.

The bottom line here is that, as usual, there is more to the story than a naive understanding would suggest. The question is whether any of this makes an audible difference. My experience in receivers is that it is highly unlikely. My experience also tells me that it would be foolish to assume that it is not possible for it to make a difference, as well. Once again, some measurements of what happens over time would be required to know. Concensus is mostly that it doesn't make any meaningful difference in most cases.
 

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You bring back some memories of my ham radio days when things like the intra workings of electrolytics were of interest. My career is 100% 60 Hz stuff so I can't speak with authority on electrolytics. In the power industry we consider capacitors lossless (big ones ... the size of your computer ... and, of course, not polarized). I'm sure there are some losses for instance in the aluminum foil and such, but I don't ever recall an electrolytic becoming noticeably warm to the touch when working. Do they? That's why I suggested most of the temperature rise comes from other sources.

Only those circuits that aren't served by voltage regulators would be influenced by variations in power supply electrolytic cap performance, right? Doesn't that leave pretty much just the amp final stages at the mercy of the power supply electrolytics; though I guess there are some electrolytics downstream of even the voltage regulators serving the preamp analog circuits (digital circuits wouldn't be affected, right).

Seems there's very little opportunity for the power supply electrolytics to influence sound short of the power hungry lowest frequencies. That's why we buy amps with 80,000 Mfd per channel instead of 40,000 Mfd, right?

So, I think you might know ... does the capacitance of an electrolytic increase when it warms up? Or maybe it forms some each time it's energized after sitting for a while. Maybe that's the bigger effect.
 

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I think your last statement is more correct...it forms some each time it is charged.

Most of my experience comes from the repair perspective, and mostly, none of this seems to have much effect with respect to burn-in periods. The effect of temperature on capacitance is so minimal that it is likely irelevant, but over time, of course, does affect reliability. There are lots of caps used at various points that could be affected by changes in ESR that could be audible, or by DA. Again, this is more a matter of performance overall or reliability than a concern for burn-in. The fact is, no one has cared enough to do any testing. Likely with good reason.
 

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Agreed.

Now, speaker break-in I believe. I used brand new drivers in my latest sub project. I would guess the rubber surround and the cone change little during break-in, but that accordion like material that centers the cone near the voice coil was very stiff. It was clearly going to take a while before it would free up and let me get anywhere near Xmax.
 

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Yes, but what about changes over time that continue. Why would you expect that it is an enhancement to the sound and not degradation, or at least drifting from the expected parameters? Why would one assume a break-in period until it gets to where it is supposed to be as opposed to "break-down" over time?
 

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From recent experience, I have to vote YES.

Surprised me too, considering I'm running this new 4308 as a preamp only (with existing amps). I did a bit of research, and some folks think the circuitry undergoes a "warming" (literally) during break-in that settles the electronics.

Sounds like hokum, but I don't have any other explanation as to why it should sound so nasty the first few days, then settle down. Two weeks into ownership, it's now as warm as the old preamp.
 

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Could be. But, I think that if one can't find much reason for break-in during the first 100 hours, there shouldn't be much change over the next 1000 hours ... or much more either. I.e., assuming there are some components that settle-in over the first 100 hours, one would hope they would hold for a few thousand hours .. or much more thereafter. Certainly at some point as components (mostly capacitors and resistors) approach end-of-life component values will start changing and that may degrade performance. I think some things like bias settings are self-correcting as components age. That would involve resistors. With capacitors that might not be the case. However, I think most of our equipment is now direct-coupled so maybe capacitors aren't much of an issue. They kill parasitics and such and as such their values aren't very critical.

Psycho acoustics is an interesting field. There are more questions than answers about how the ears and brain work. Empirical tests involving subjective observations by the listener give us most of what we know about the ear-brain hearing system but that knowledge is being used to improve our equipment (e.g., the Audyssey DynamicEQ in the 4308). What I'm getting at is that maybe our brains adapt somewhat to new and different presentation of the material we listen to and that probably has more to do with changes in the first 100 hours than does equipment break-in. We do know that our ear/brain setup does adapt to environments, for instance, to extract one voice out of a crowd (at least until you get into your 50's). Maybe we also adapt to new speakers or changes in room acoustics or a different preamp or amp over time.

As an aside, communication between the ear and the brain is part analog and part digital. Some of the information is sent via pulses and some is sent more like electrical waves that look like speaker movement. The brain has to interpret that and learn what it means. Makes you wonder if your brain and mine are "hearing" the same thing when we are both listening to and enjoying the same track.
 

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Actually, all communication in the brain, beyond the point that sound is translated into nerve activity, is in the form of neurons that either fire or are inhibited. Some consider this to be digital, but I think this is a naive view. To try to simplify perception to classificaitons such as analog and digital is not very useful. While the basics of signal transmission are synapses that either pass the signal or do not, the levels of activation and inhibition, the complexity of interconnection, and the vast numbers of involved neurons make the activity for even the simplest "transmission" of the most simple stimuli far more complex than most realize.

Perception is highly adaptive, no doubt, and I agree that there is likely far more accomodation in perception than break-in affecting the sound we perceive in a receiver.
 
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