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Post by philietes on Dec 20, 2016 16:31:14 GMT
Hi,
When connecting a mobile device (e.g. iPhone and Macbook Pro) to RCA inputs on an amp, will there be any difference in sound quality between: 1. Headphone out: (1.0 - 2.25 vrms) 2. iPhone dock line-out: (2.25 vrms)
Both cables are 3.5mm to RCA. I can imagine there is some sort of impedance mismatching because the amp is expecting line-out input? Of course the maximum volume will be compromised which is inevitable.
Thanks a lot! Regards, Philietes
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Post by arnyk on Dec 20, 2016 18:51:50 GMT
The headphone outputs on most quality digital music players (such as the Apples) generally are audibly identical to a good line output. They can obviously handle lower impedance loads, but they generally have even lower distortion when driving higher impedance loads.
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Post by Ethan Winer on Dec 20, 2016 20:28:34 GMT
Besides Arny's correct answer, I wouldn't be surprised if some devices use the same output for headphone and line outputs.
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Post by philietes on Dec 20, 2016 22:11:07 GMT
Thank you for the answers. Much appreciated. But I am not sure if I explained my question clearly; the 'iPhone lightning dock' is a separate little device of $50 connected to the 30-pin connector on the iPhone. This dock has a line-level out 3.5mm jack. So it is a different output from the 3.5mm headphone out on the iPhone itself. Probably, the impedance is not the same. Also, the signal path is not the same. When connected to the dock the volume controle on the iPhone is greyed out: so the line-level out is constant, the headphone out is variable. (line-out constant at 2.25 rvms, the headphone out variable up to a maximum of 1.0 rvms I read online)
So will there be any difference theoretically in the fidelity when connected to the RCA inputs on an amp? Would be interesting if not because it would render all iPhones dock useless!
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Post by arnyk on Dec 21, 2016 2:40:27 GMT
Thank you for the answers. Much appreciated. But I am not sure if I explained my question clearly; the 'iPhone lightning dock' is a separate little device of $50 connected to the 30-pin connector on the iPhone. This dock has a line-level out 3.5mm jack. So it is a different output from the 3.5mm headphone out on the iPhone itself. Probably, the impedance is not the same. Also, the signal path is not the same. When connected to the dock the volume controle on the iPhone is greyed out: so the line-level out is constant, the headphone out is variable. (line-out constant at 2.25 rvms, the headphone out variable up to a maximum of 1.0 rvms I read online) So will there be any difference theoretically in the fidelity when connected to the RCA inputs on an amp? Would be interesting if not because it would render all iPhones dock useless! I am and was 100% familiar with the the dock and its 30 pin connector. I'll stick to my story, including the part you apparently didn't read where I already mentioned the impedance difference. One of the lesser-known lessons of audio is that there are approximately an infinite number of ways to get the same perceived sound quality, so the fact that there is a volume control in one path, that the voltage is different, that the impedances are different and that the circuitry is different need not matter to sound quality if both are well-engineered, which they are. If you need the higher voltage, or if there is a problem with continuing to use the volume control on the iPhone even if you just set it to max, then of course get the dock. But the use of the dock would be your preference, not because it improves potential sound quality. Evertyhing doesn't matter, just the important stuff.
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Post by philietes on Dec 21, 2016 15:09:58 GMT
It seems so unreal to me to learn all these stuff: sometimes when reading forums there is easily 100 different comments about how the quality improved subjectively with e.g. this DAC. Not even one of them mentions the difference is marginal or not audible at all. This is immensely misleading for customers. I am estimating the money involved in HIFI to be about 2% it is now, if the placebo effect was non-existent. Thanks for your answer. It seems logical that the voltage of the signal should not make a difference, but just the quality of the signal.
By the way I actually read the part about impedance a few times, but I was not quite sure I understood fully. It means that because of the very impedance headphone out, the line-level input on the amp, which is therefore very high impedance, is loaded with even less distortion theoretically because of this?
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Post by arnyk on Dec 21, 2016 15:51:48 GMT
It seems so unreal to me to learn all these stuff: sometimes when reading forums there is easily 100 different comments about how the quality improved subjectively with e.g. this DAC. One day I ran into a market survey of current DACs, and it ran to over 400 distinct makes and models. What's ironic is that I've measured over 100 of them, and done DBTs on a few dozen of the ones that looked marginal enough to be interesting. Interesting factoid - one of the first DACs to reach the consumer market (in 1983), the DAC that centerpieced one of the first CD players sold the Sony CDP 101, can with the right program material be coaxed into having a discernible audible signature. Of course, with more typical program material, its random guessing for everybody listening. This DAC (like the Dyna Stereo 120 power amp before it) has a reputation among audiophiles that claim to have listened to it of being utterly horrible sounding. The bad sound has even been ascribed to jitter, which is a performance area where it is actually close to being SOTA. These "audio eggspurts" are just guessing, not actually listening. A general rule is that the distortion of a power amp goes up as the load impedance goes down. In the case of a portable digital player, the actual in-use headphone jack's load runs from something like 15 ohms (some headphones) to 10,000 ohms (a standard high line level input) to 100,000 ohms or more (tubed gear and some SS gear designed to be more compatible with tubed gear). In every case I know of, the distortion with the headphone loads (which run up to a couple of 100 ohms) are always measurably higher than what one measures with the loads that are appreciably greater. Usually, things are as good as they get around 10,000 ohms and up. One of the hallmarks of a good headphone jack on a portable digital player is that it can drive low efficiency and low impedance headphones to the European legal limit SPL with inaudible distortion. iPhones can do this since the first model, and have only gotten better or stayed the same since then. [/quote]
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Post by philietes on Dec 21, 2016 16:55:44 GMT
It is kinda amazing to read about Ethan Winer on the internet; particularly the thread he was banned on thewombforums.com hahaha (the one with BIG NEWS!! in the title). Very amusing to read about all those stubborn people. I really appreciate that you actually take the time to bother responding to them. Anyways all this new information makes me want to walk into any audio store and make fun of the people working there who are practically thieves.
About the impedance matching. I think it is proven that a smaller ratio than 8 *might* be audible. So with IEM of 16 ohms (pretty common), the output impedance should be 2 or less. Which the latest iPhone have, but a lot of expensive gear does not.
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Post by arnyk on Dec 22, 2016 3:27:32 GMT
It is kinda amazing to read about Ethan Winer on the internet; particularly the thread he was banned on thewombforums.com hahaha (the one with BIG NEWS!! in the title). Very amusing to read about all those stubborn people. I was banned from the Womb, both posting and reading, after making one (1) innocent technical post. hese guys like to talk about being open minded,but don't look at what they do themselves. The de facto standard for power amps is 20 or greater, given that the response variation is at the frequency response extremes The practical limit for a cheap headphone amp is about 0.1 ohm. There is a school of thought that some expensive gear is internationally built to have these unecessary frequency response errrors to create the mystique of a characteristic sound. Surely true of your typical SET or NOS DAC.
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Post by philietes on Dec 29, 2016 17:45:40 GMT
arnyk Really? It makes you wonder why those people are on forums anyway. Do you happen to know if in-ear phones produce true 20Hz frequencies, or just overtones of those low frequencies? It seems impossible for a 7mm driver to produce such long wavelengths. But then maybe, it uses the small airlocked space in your ear to fake you into believing it is actually bass that low somehow. I was thinking about this, interesting to know what are the trade-offs using in-ears vs headphones vs speakers. One advantage of not using full size speakers, Ethan will be quick to point out probably, is that lack of room treatment will ruin the sound quality. So what are the disadvantages?
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Post by arnyk on Dec 29, 2016 18:22:50 GMT
arnyk Really? It makes you wonder why those people are on forums anyway. (1) Help with technical problems. (2) Reinforcement One of the well-known forums dealing with headphones even has called itself the "I'm OK, you're OK" forum. IEMs can go either way, but done right they are the least difficult way to obtain true deep bass. Any such limitation in the bass is an audiophile myth. Wavelengths are far more important at high frequencies. However, a large diameter driver can and often will be a pretty good high frequency reproducer, except that it will be as directional as all get out. Because of the small, sealed space that has to be presurized to make real bass. there is very little need to fake anything. One of the problems with earphones and headphones is that the air volume they have to work with with while favorably small, strongly tends to be significantly acoustically different for everybody. A person who knows what they are doing, custom fitting them to each individual, can do well. There is a big difficulty that lies in the fact that everybody's ears are different and highly personalized, especially from the standpoint of earphones and headphones. Some of that gets factored out of the equation by the fact that our brains naturally adapt what we hear to be somewhat similar.
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Post by Hexspa on Dec 30, 2016 6:20:32 GMT
I got some skull candy sealed ear buds which are great for hearing things in the low end.
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Post by rock on Dec 30, 2016 13:06:17 GMT
Hi philietes,
You wrote "It seems impossible for a 7mm driver to produce such long wavelengths". arnyk answered this this a myth. I'm sure the reason for this is the misunderstanding of "wavelength".
Very simply, wavelength = velocity / frequency. Think of the wavelength in linear terms, emerging from the driver front surface. The wavefront will move away from the driver at the velocity of sound through air (1130 f/s). It does not matter how small the driver diameter is, what maters is how slow or fast the driver can move back and forth. So a 7mm driver can reproduce a low frequency easily as long as it can vibrate slowly enough. The basic principle has nothing to do with the size of the driver.
Cheers, Rock
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Post by Ethan Winer on Dec 31, 2016 15:51:51 GMT
Good discussion guys!
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Post by philietes on Jan 1, 2017 11:55:58 GMT
Why is it then that when you remove in-ears from your ears, and hold them in mid-air, only some sqrueeking of high frequencies is heard? This would be different with a 15inch driver, right? Also I notice that over-ear headphones produce seemingly deeper bass than my Sennheiser IE-800?
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