[Audman71]

Pardon the newbie question, but can someone explain to me why a headphone amp is so significant an improvement that I should spend money on it?
 
I've heard music through a headphone amp at a local store while testing headphones I thought I might want to buy. I then played the same music on my iPod, and I couldn't really tell much of a difference.
 
What exactly is it doing? Is it lowering the noise floor or something? What does an amplifier do that is worth the money?
 
This is not a rant, I'm just curious, Sell me on the idea! 
 
In addition, if you have any specific products you feel are good to try, feel free to share them.

 

[Music Alchemist]

I was going to take a few minutes to explain in my own words...but this search link explains it all.

 

[fjrabon]

1) your source can't make your headphones loud enough without clipping
2) your source's output impedance is too high for your headphones, and thus doesn't provide enough electronic damping
3) You are using an offboard DAC (for the benefits they provide) and want a volume control
 
Those are by far the three most important.  There are other, more esoteric, much harder to explain benefits that will also vary from amp to amp.  Things like the benefits of having a class A amplifier, lower crosstalk figures, cleaner power, etc.  But those are all very subtle benefits.  
 
Further, the iPod has an amp, anything you play your headphones out of must have an amp or it would make literally no sound.  So, what you're asking about isn't why you would buy an amp, but why you would buy a different amp from the one built into your iPod.  Thought about that way, it makes more sense, as amps can obviously vary in quality and how well it matches a given pair of headphones.  I think on sites like this on board amps for things like an iPod or iPhone are vastly underrated.  Many players' amps are quite good, though a bit underpowered for some hard to drive headphones.  

 

[ProtegeManiac]

Quote:

Originally Posted by Audman71 /img/forum/go_quote.gif

Pardon the newbie question, but can someone explain to me why a headphone amp is so significant an improvement that I should spend money on it?

 

I've heard music through a headphone amp at a local store while testing headphones I thought I might want to buy. I then played the same music on my iPod, and I couldn't really tell much of a difference.

 

What exactly is it doing? Is it lowering the noise floor or something? What does an amplifier do that is worth the money?

 

This is not a rant, I'm just curious, Sell me on the idea! 

 

In addition, if you have any specific products you feel are good to try, feel free to share them.

 

Any amplifier, and that includes the small chip inside every device like an iPod or smartphone, will follow this rule: more power output, more distortion. Power delivery also depends on the design - some amplifiers deliver more power at high impedance load, most deliver more power into a low impedance load. Also, the curve for how much distortion rises in proportion to output level varies.

 

Headphones have varying nominal impedance, sensitivity, and efficiency.

 

Now, if you have a device that can push out 5mW at 32ohms with 0.1% distortion, with noise kicking in at 86dB, but you plug in a headphone that has a nominal impedance of around 52ohms but has a sensitivity of 92dB/1volt, you will likely have a lot of audible distortion just getting that up to 88dB listening levels, and you probably don't have enough clean power reserve in case the impedance on it swings far from the nominal impedance on some frequencies (ie, there are headphones that havea much lower or higher impedance when playing low frequencies for example). 

 

Drive that same headphone with an amp with a low output impedance, roughly 200mW at 40ohms with 0.001% THD and very, very, very black background (ie, very low noise levels), and there will be less distortion in the signal. Basically, you minimized the deviation from the recording down to what the headphone's response is (there is no speaker or headphone yet made with current tech that is as flat as an amp), so it will sound closer to what it's supposed to sound like. Also, along with less distortion from the amp, the blacker background helps making dynamics clearer.

 

If you did that test in an area with a high enough noise floor, like a Best Buy, the reality is that the iPod can still get it loud enough, but even if you brought an amp with you the noisefloor can mask the improvements.At the same time while you need the amp to get louder it shouldn't be a strategy for dealing with a high noise floor because that will just damage your hearing.

 

It's also likely that that particular headphone is efficient enough that the iPod doesn't get enough distortion audible to you, but of course it won't be the same with a low impedance, low sensitivity headphone or a high sensitivity headphone that will tax your iPod's audio chip with a very high nominal impedance. Even the very efficient Beyerdynamic T1 at 600ohms isn't going to sound all that good directly off an iPod.

 

[Audman71]

Hmm... From what I understand, having a good headphone\amp combination is a little like having Dolby NR on a tape deck? I use that with my cassettes and it reduces the noise floor and allows for higher volumes without distortion on the tapes I use it on.
 
Also, If I have a high quality PC sound card, like a PreSonus Firestudio Project, Why would I need to have a headphone amp in that particular circumstance?

 

[Music Alchemist]

Check out these links (in addition to what I shared earlier) to learn about headphone amplification:
 
http://www.apexhifi.com/specs.html
http://blog.jdslabs.com/?p=1285

 

[ProtegeManiac]

Quote:

Originally Posted by Audman71 /img/forum/go_quote.gif

Hmm... From what I understand, having a good headphone\amp combination is a little like having Dolby NR on a tape deck? I use that with my cassettes and it reduces the noise floor and allows for higher volumes without distortion on the tapes I use it on.

 

Dolby NR, noise reduction, reduces noise at the source. An amplifier is not a source, it amplifies the signal from the source, but in the process can develop distortion and noise. Even if you have a very low noise track at a reasonably loud enough level, if whatever you are using to amplify the signal - which again isn't necessarily a separate amplifier, but a headphone output on the same source device - develops noise and distortion too soon depending on the sensitivity of your headphone, then it's advisable to get a separate amplifier provided that same source can deliver a clean signal to it that will bypass the same noisy headphone amp circuit in it.

 

So for example you have a noise reduction software on your smartphone, but your headphones have a low enough sensitivity that your smartphone is distorting, then an external amp is beneficial; however, if you'll just hook it up to the same headphone output that will now be feeding an even higher impedance input on the amplifier, then might as well get one with a DAC and just check if your smartphone does USB audio.

 

If however you're using a 32ohm, 125dB/1mW sensitivity IEM on that smartphone, then as long as the software isn't screwing it up with noise or EQ effects, then a separate amp or even an amp with a DAC will not improve the sound by as much.

 

Quote:

Originally Posted by Audman71 /img/forum/go_quote.gif

 

Also, If I have a high quality PC sound card, like a PreSonus Firestudio Project, Why would I need to have a headphone amp in that particular circumstance?

 

It depends on the headphone and the specs on the headphone output on that one. I've seen a few audio interfaces that have headphone output specs that looked more like some kind of afterthought, with something like 40mW at 32ohms (no clue on how close that is to 1% distortion) and an output impedance of 10ohms (you need the amp output impedance to nominal headphone impedance ratio to be close to 1:8). The only spec I can see on the Presonus is that the power output is rated for 150mW at 60ohms (again, no clue how close that is to 1% THD), and nothing on the output impedance from their website. Designs like this can be tricky - apart from OTL tube designs I'm not aware of how any other kind of amplifier delivers more power at higher impedance, and besides, marketing-wise, you'd quote where it makes the most power, like how some HT receivers don't tell you only one channel was loaded in the test and distortion levels were high, but still say "bajillion watts X a dozen channels" or something. But then the output impedance can be a problem for low impedance headphones. Basically, you're going to choose between one kind of distortion with low impedance cans, and possibly a level of higher THD yet relatively lower output at high impedance.

 

I suggest you send Presonus and email and ask what the output impedance is, and then choose the headphone based on their response. Still, at 150mW at 60ohms, then if power halves as impedance doubles, a guesstimate would be that you still have around 37mW at 250ohms and mayb around 25mW at 300ohms, which should be enough for a sensitive enough Beyerdynamic or Sennheiser. In case the output impedance is low enough then go ahead with a lower impedance headphone, or better, a low impedance, high sensitivity, closed back (ie, more ambient noise blocked) headphone like the T70P or the T5P.

 

[Degenerator9000]

Honestly, if you compared amp vs no amp and saw no difference on your phones, I'm not gonna try and sell you on the idea lmao. You've already proven that it's subjectively not worth it to you. 

(Obviously this might change with different headphones)

 

[Audman71]

 

 

Dolby NR, noise reduction, reduces noise at the source. An amplifier is not a source, it amplifies the signal from the source, but in the process can develop distortion and noise. Even if you have a very low noise track at a reasonably loud enough level, if whatever you are using to amplify the signal - which again isn't necessarily a separate amplifier, but a headphone output on the same source device - develops noise and distortion too soon depending on the sensitivity of your headphone, then it's advisable to get a separate amplifier provided that same source can deliver a clean signal to it that will bypass the same noisy headphone amp circuit in it.

 

So for example you have a noise reduction software on your smartphone, but your headphones have a low enough sensitivity that your smartphone is distorting, then an external amp is beneficial; however, if you'll just hook it up to the same headphone output that will now be feeding an even higher impedance input on the amplifier, then might as well get one with a DAC and just check if your smartphone does USB audio.

 

If however you're using a 32ohm, 125dB/1mW sensitivity IEM on that smartphone, then as long as the software isn't screwing it up with noise or EQ effects, then a separate amp or even an amp with a DAC will not improve the sound by as much.

 

 

It depends on the headphone and the specs on the headphone output on that one. I've seen a few audio interfaces that have headphone output specs that looked more like some kind of afterthought, with something like 40mW at 32ohms (no clue on how close that is to 1% distortion) and an output impedance of 10ohms (you need the amp output impedance to nominal headphone impedance ratio to be close to 1:8). The only spec I can see on the Presonus is that the power output is rated for 150mW at 60ohms (again, no clue how close that is to 1% THD), and nothing on the output impedance from their website. Designs like this can be tricky - apart from OTL tube designs I'm not aware of how any other kind of amplifier delivers more power at higher impedance, and besides, marketing-wise, you'd quote where it makes the most power, like how some HT receivers don't tell you only one channel was loaded in the test and distortion levels were high, but still say "bajillion watts X a dozen channels" or something. But then the output impedance can be a problem for low impedance headphones. Basically, you're going to choose between one kind of distortion with low impedance cans, and possibly a level of higher THD yet relatively lower output at high impedance.

 

I suggest you send Presonus and email and ask what the output impedance is, and then choose the headphone based on their response. Still, at 150mW at 60ohms, then if power halves as impedance doubles, a guesstimate would be that you still have around 37mW at 250ohms and mayb around 25mW at 300ohms, which should be enough for a sensitive enough Beyerdynamic or Sennheiser. In case the output impedance is low enough then go ahead with a lower impedance headphone, or better, a low impedance, high sensitivity, closed back (ie, more ambient noise blocked) headphone like the T70P or the T5P.

 
Huh. You know, I think I'm starting to see what you mean. I recall having a kenwood amplifier that had a terrible noise problem in both speakers and headphones. It was just a bad design. The PreSonus I have has bad noise too, when turned up higher. I also remember that if you turn up a preamp too high it distorts. maybe I'll give headphone amplifiers a second chance.
 

  Honestly, if you compared amp vs no amp and saw no difference on your phones, I'm not gonna try and sell you on the idea lmao. You've already proven that it's subjectively not worth it to you. 

(Obviously this might change with different headphones)

 
That's not entirely true. I was simply wondering if I should get one because when I tested out the headphones at the shop I was in with the headphone amp, (1) I had no frame of reference because the headphones I don't own and listened to only came out of the amp (The headphones I brought with me there however I tried on both and I couldn't tell much of a difference), and (2), I was specifically listening for headphones and not the amplifier noise and distortion levels.
 
 
I've heard some amps are better quality than others, and that it also depends on the combination. As said in my opening post, what amp recommendations do you guys have?

 

[Music Alchemist]

  I've heard some amps are better quality than others, and that it also depends on the combination. As said in my opening post, what amp recommendations do you guys have?

 
If you list your headphones, I can show you their power requirements so you have a better idea of which amps to consider.

 

[ProtegeManiac]

Quote:

Originally Posted by Audman71 /img/forum/go_quote.gif

 

Huh. You know, I think I'm starting to see what you mean. I recall having a kenwood amplifier that had a terrible noise problem in both speakers and headphones. It was just a bad design. The PreSonus I have has bad noise too, when turned up higher. I also remember that if you turn up a preamp too high it distorts. maybe I'll give headphone amplifiers a second chance.

 

My Meier Cantate.2 can be turned all the way up with nothing running, and at high gain, and the noise coming through is barely audible.I don't even get past 12:00 on the dial, and that's with very low volume audiophile recordings.In any case, if the Presonus has fixed level line outputs, you can hook up the headphone amp there, in case you still need that instead of a stand-alone playback chain.
 

Quote:

Originally Posted by Audman71 /img/forum/go_quote.gif

 

That's not entirely true. I was simply wondering if I should get one because when I tested out the headphones at the shop I was in with the headphone amp, (1) I had no frame of reference because the headphones I don't own and listened to only came out of the amp (The headphones I brought with me there however I tried on both and I couldn't tell much of a difference),

 

What headphones did you take with you? 

 

Quote:

Originally Posted by Audman71 /img/forum/go_quote.gif

and (2), I was specifically listening for headphones and not the amplifier noise and distortion levels.

 

It's easier to hear differences in the bass and treble than the midrange, unless of course one amp is deliberately colored as in some tube implementations. One of my solid state amps has a nasty cymbals splash, while my other SS amp was smooth yet detailed on any headphone, and then I have a hybrid now that sounds closer to my reference SS amp (save for noise from the tube coming up at around 2:00 on the dial, which is too loud anyway). The reference SS amp leads in rendering solid bass thuds, followed closely by the hybrid, and then the other SS. If you're choosing between amplifiers, focus on the treble and bass to hear any issues more easily.
 
 

Originally Posted by Audman71 /img/forum/go_quote.gif
 
I've heard some amps are better quality than others, and that it also depends on the combination. As said in my opening post, what amp recommendations do you guys have?

 
That can depend on the headphones you plan on using, and for what purpose. If you'll use the amp and headphones with the Presonus interface, then accuracy is key, get something like the O2 or the Meier Jazz. Barring very high impedance (or very low sensitivity) these will drive pretty much any dynamic headphone and some planars as well. If you have high impedance headphones, OTL tube amps like the Valhalla2 are also an option as they are best for such headphones (they don't do well at lower impedance, or at least not as well as most SS amps).
 
If you want a generally neutral tone but want to make sure you get no harshness even on some rough recordings, look into getting a hybrid or tube amp (as long as it won't have impedance issues or output level deficiencies for your headphones) that has for the most part a very low THD rating. That means it will generally be neutral throughout the range, but there's enough tube distortion to soften up the rough edges; or you can look at that another way, in that there is a tendency for some solid state designs to distort in a way that makes the treble sharper (ie if THD was comparable, the tube/hybrid and SS amp can have a tendency to sound different once you get to that level of distortion that it's audible on both). 

 

[Degenerator9000]

Seconding the O2 recommendation

The Magni2 Uber has more power behind it at the same price, but I like the soundstage of the O2 slightly better (based on my relatively brief 3 day trial) and the fact that it's transportable/battery operable is pretty huge as a college student. It's incredibly capable, very neutral, and inexpensive.

Given the class A/B design though, there are some people who will prefer a class A amp over it with insensitive headphones (like planars, generally) as class As offer more power to immediately drive transients without the very slight lag inherent in A/B design.

The tradeoff is that you're never going to find a portable class A amp with the overall power of the O2, as they're incredibly inefficient.

(really hoping someone doesn't rig a stepped up car battery to their WA2 to prove me wrong here )

 

[fjrabon]

Seconding the O2 recommendation

The Magni2 Uber has more power behind it at the same price, but I like the soundstage of the O2 slightly better (based on my relatively brief 3 day trial) and the fact that it's transportable/battery operable is pretty huge as a college student. It's incredibly capable, very neutral, and inexpensive.

Given the class A/B design though, there are some people who will prefer a class A amp over it with insensitive headphones (like planars, generally) as class As offer more power to immediately drive transients without the very slight lag inherent in A/B design.

The tradeoff is that you're never going to find a portable class A amp with the overall power of the O2, as they're incredibly inefficient.

(really hoping someone doesn't rig a stepped up car battery to their WA2 to prove me wrong here )

Chord Mojo is class A.

 

[Degenerator9000]

Chord Mojo is class A.

Yeah, I actually checked the numbers before I made that comment to be sure the O2 slightly edged it out

It gets pretty close though

 

[fjrabon]

Yeah, I actually checked the numbers before I made that comment to be sure the O2 slightly edged it out

It gets pretty close though

The reason why you rarely see very powerful class a amps that are portable isn't that they require too much power, it's that they would run too hot at low volumes. How hot they run is inversely proportional to to the volume level on class A. They don't actually require much more power than A/B. Just that A/B doesn't run as hot at low and medium volumes.