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Why am I hearing a difference in amps?

post #1 of 25
Thread Starter 

OK, so normally this would go in a different part of the forums, but I'm looking for an objectivist view on the subject, so here I am. I call myself an objectivist and therefore do not really believe in differences in amps (unless one is underpowered for the application or just a very bad amp that doesn't have a flat frequency response). We obviously know about the tests done proving the point that you can make one amp sound exactly like another.

 

The difference I'm hearing is between my iPod 5.5 and the Fiio E11

 

So, the weird thing is that I recently bought a fiio E11 to power my HE-500s in my portable setup and heard a difference! I actually had some IEM's plugged in and wouldn't have bothered using the fiio, but it was rubberbanded to my iPod so I tried both and heard a stark difference. The other weird thing was that it wasn't just frequency response that seemed different (E11 had better bass and treble extension), but the sound stage seemed way bigger while using the E11. Now this can't be all in my head since I wasn't expecting to hear any difference. Trying the HE-500 produced the same results, but that was to be expected since the iPod was at about 95% volume. I don't have an A/B rig or SPL meter yet, so this wasn't super scientific, but the differences weren't subtle.

 

I thought the iPod 5.5 was a pretty good product, and it seems to measure flat according to stereophile (see below). It's also interesting that I'd be seeing positive results by switching to a budget, portable amp.

PODFIG01.jpg

 

So, any ideas about why I hear a difference even when I run within the ipod's power capabilities?


Edited by mnarwold - 10/31/13 at 6:05am
post #2 of 25

Did you match levels (preferably measuring the voltage on the HE-500 with a splitter and a multimeter, and playing a test tone) when comparing the iPod to the E11 ? It is quite possible that the E11 was simply louder (this is actually not easy to judge by ear when the difference is not large), and that has psycho-acoustical effects like what you described. It is also not unlikely that the iPod cannot output enough power without clipping to drive the HE-500 at the loudness you prefer, as the HE-500 is rather inefficient.

 

With the IEMs, the output impedance of the iPod can make an audible difference if it is too high, and at least for some models that is indeed the case.

 

By the way, you cannot be entirely sure if you expected to hear a difference or not, because this happens sub-consciously. That is why blind testing is needed to reliably exclude bias from the comparison.


Edited by stv014 - 10/31/13 at 6:14am
post #3 of 25
Thread Starter 

I stated I didn't have an SPL meter to indicate that I didn't volume match perfectly. After hearing the difference I did make sure the volume was just a little higher on the iPod so any error would be in it's favor. I am familiar with the effects of volume differences, and this wasn't that. The impedance issue is possible while using the IEM's, but it would surprise me since they are 24 ohm and not super low, but that is a possibility. I can't find the output impedance of the 5.5 although some of the other apple products are 5ohm or more, so that's a possibly the problem.

post #4 of 25

It's also possible that both devices just measure differently.

post #5 of 25
Quote:
Originally Posted by mnarwold View Post
 

I stated I didn't have an SPL meter to indicate that I didn't volume match perfectly. After hearing the difference I did make sure the volume was just a little higher on the iPod so any error would be in it's favor. I am familiar with the effects of volume differences, and this wasn't that.

 

You do not necessarily need an SPL meter, a DMM would also work, and could even be more reliable if used correctly. Even a splitter and a PC sound card (onboard could be sufficient, if there is nothing better) might be enough, and would also allow for verifying that the iPod is not driven into clipping. In any case, since you compared the devices sighted and without level matching, it is hard to tell if the perceived difference is a real sound quality issue, and exactly what is causing it.


Edited by stv014 - 10/31/13 at 6:54am
post #6 of 25

Could one or the other of them have had some sort of EQ setting turned on?

post #7 of 25

It could just be possible that the two sound differently.  


Edited by TMRaven - 10/31/13 at 5:57pm
post #8 of 25

Is the Filo colored?

post #9 of 25

Yes, two amps could sound different. It has nothing to do with price.(within reason)

IT has more to do with design. A good match of headphone with a particular design

can make a big difference. Headphones have such a wide range of impedance that

some match better. 32 ohm to 600 ohm, that's a pretty wide range to design for.

post #10 of 25
Quote:
Originally Posted by bigshot View Post
 

Is the Filo colored?

 

yes.

 

i don't have measurements or "proper" testing, so  it is what it is.  but the fiio sounds warm(er) than most of my other gear, with the exception of my vintage sony which also sounds very warm.  it's a subtle difference but quite a few random friends have noticed the difference immediately in casual "testing"

post #11 of 25

Junk the Filo and get something that performs to spec then.

post #12 of 25
Thread Starter 

According to nwavguy, who has all the measurements posted, the E11 is flat and not colored (20-20k at +/- 0.1db). It has pretty darn good measurements for THD and IMD. Nwavguy has some problems with the design, but for the price and size thought it was a good amp (although it didn't measure as powerful as listed). I couldn't tell a difference between the E11 and the O2, so that's good and means that it can't be E11 that's the colored one.

 

I did another test in which I used the E11 amp switching between the iPod's amp and iPod's LOD as the source and had the exact same change in sound. Using the LOD made it sound good with extended bass and highs and using the iPod's amp had the same issue of losing the lowest and highest frequencies and having almost a mono sound. So, this rules out the impedance issue since the amp has an input impedance of over 5k ohms. This should make it clear that the amp of the iPod is doing something detrimental to the sound.

 

I double checked the EQ of the amp and the ipod and both were in off positions, so it's not that. I'm beginning to wonder if there is just some issue with the ipod's amp, but I'm not sure what that would be.

post #13 of 25

Maybe your iPod is defective.

post #14 of 25

Or maybe the amps sound different.

IS the obvious too obvious?

post #15 of 25

If they both measure flat, they shouldn't sound different, unless one or the other of them isn't performing to spec. It's no great trick to get electronics to produce a flat response. There's no excuse for not doing that. If something sounds different, there is something wrong with it, whether a manufacturing error or a bad judgement in design.

 

Perhaps I'm not understanding what the OP means by amp. Are you talking about an external amp?


Edited by bigshot - 11/1/13 at 3:27pm
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