[ReadNLearn]

My apologies if this info is out there already, but I haven't found it.

I'm currently researching headphones, specifically considering the SennHeiser 595s. In quite a few places online there ends up being mini-debates where someone recommends getting a headphone amp for the 595s and then someone else says no it absolutely is not needed. Then someone else will say it isn't strictly required but it will sound much better. So then someone usually says, ok what do I buy and what should I expect it to do for me? Then someone says go ask at Head-fi.org, they know everything and are helpful and approachable. So... prove it.

I enjoy exceptional sound, but I don't understand any of the terms you guys use on this site. With all the brand names, acronyms, scientific terms, etc. rolling around in the threads it is quite difficult to figure out where to start. Really going from ground 0 here.

So, here are some questions (really for general consumption, so I've phrased them in a way that is not specific to my specific needs for future readers):

1. What is the benefit of an amp? Why will it make my headphones sound better than if they were plugged straight into an IPod, or my computer, or a CD player, etc.

2. What is the benefit of a DAC? Is this needed in all cases? For example, if someone is listening to music on a PC, isn't it already digital?

3. For headphones that are "easy to drive", I've read they don't need amps but can benefit from them. As I understand it this means they have low impedance (nope, don't know what that actually means) which is measured in Ohms. Looking at 50Ohm Sennheiser 555s, there seems to be a consensus that an amp won't provide much benefit. For the Sennheiser 595s though, there seems to be a much stronger contingent of people saying an amp is a very good idea to get the most out of them. Both are 50Ohm, so I don't get it.

4. For home use (as opposed to portable) is there any benefit to a "headphone amp" vs. a regular audio receiver?

Ok, getting specific to my situation here now. I have an old Yamaha RXV-1000 receiver collecting dust since I replaced it with a new Denon AVR-3808CI for my home theater setup. Can the Yamaha receiver be used for as good effect as a headphone-specific amp, such as the Headroom Micro Amp? For my particular situation I'd be attaching this to my home computer from which I play lossless music WAV files, as well as for gaming. I'm assuming for the receiver I'd run an optical audio cable from the optical out on the soundcard (yep, confirmed I have one) to the optical in on the receiver, plug in the headphones to the receiver and I'd be good to go. Is this a good or bad idea, and why? Aside from the monstrous size of the receiver since we'll pretend for the moment that it doesn't matter. Would setup for a headphone amp be basically the same? Does the receiver include a DAC, and does that even matter?

Thanks in advance for all the forthcoming friendly, helpful replies that I will no doubt be inundated with.

 

[imademymark]

Quote:

Originally Posted by ReadNLearn /img/forum/go_quote.gif My apologies if this info is out there already, but I haven't found it. So, here are some questions (really for general consumption, so I've phrased them in a way that is not specific to my specific needs for future readers): 1. What is the benefit of an amp? Why will it make my headphones sound better than if they were plugged straight into an IPod, or my computer, or a CD player, etc. 2. What is the benefit of a DAC? Is this needed in all cases? For example, if someone is listening to music on a PC, isn't it already digital? 3. For headphones that are "easy to drive", I've read they don't need amps but can benefit from them. As I understand it this means they have low impedance (nope, don't know what that actually means) which is measured in Ohms. Looking at 50Ohm Sennheiser 555s, there seems to be a consensus that an amp won't provide much benefit. For the Sennheiser 595s though, there seems to be a much stronger contingent of people saying an amp is a very good idea to get the most out of them. Both are 50Ohm, so I don't get it. 4. For home use (as opposed to portable) is there any benefit to a "headphone amp" vs. a regular audio receiver?

1. inshort, yes.

2. a DAC is a Digital to Anaglog converter, so you are right in saying that music from a PC is in a digital form, which cannot be heard. A DAC converts this into an analog signal, which can be amplified/ listend to

3. this is a rule of thumb, but not all 50ohm phones are made equal. for exmaple, the GS1000 is only rated at 32 ohms but require a very extensive system to drive properly. the high resistance only tells you that you'd need an amp to drive it to an audible volume, not whether an amp is more benefial.

4. yes. it has a cleaner sound as it is designed specifically for headphones

cheers!

 

[qusp]

Quote:

Originally Posted by ReadNLearn /img/forum/go_quote.gif My apologies if this info is out there already, but I haven't found it. I'm currently researching headphones, specifically considering the SennHeiser 595s. In quite a few places online there ends up being mini-debates where someone recommends getting a headphone amp for the 595s and then someone else says no it absolutely is not needed. Then someone else will say it isn't strictly required but it will sound much better. So then someone usually says, ok what do I buy and what should I expect it to do for me? Then someone says go ask at Head-fi.org, they know everything and are helpful and approachable. So... prove it.

OK then I guess we've been built up pretty high, but i'll try and help out the best I can. You will always find differing opinions on these type of questions. Audio is so subjective that we all have our own view. but in your case, driving those cans then yes!! absolutely you will benefit from a dedicated headphone amp. you will find very few people especially on here that have used a decent headphone amp and dont believe it makes a difference. many people in my experience that say these type of things either havent tried it or cant afford it so they convince themselves and try with others that a HP amp isnt really worth it anyway, so that way they arent missing out on something

Quote:

I enjoy exceptional sound, but I don't understand any of the terms you guys use on this site. With all the brand names, acronyms, scientific terms, etc. rolling around in the threads it is quite difficult to figure out where to start. Really going from ground 0 here.

yeah it takes a while to learn the language, but dont worry about it; you are not alone and we arent going to judge you for it. This place can be pretty overwhelming to the newcomer and there is a huge amount of info to take in. I learn something new every day around here and therefor I try and put back in when I can. there is a thread here that covers all the lingo we use (well most of it) i'll try and find it and report back for you. One thing though; research is a good thing; it helps you to make an educated decision on what gear to buy; but there is a point where the shear amount of different views can become very frustrating. some people will prefer product A for reason X and some people will not be able to stand product A for reason X;. It helps if you can use something as a reference too so we can tell you how product A compares to product B and finding someone on here that likes similar music to you, buys in the same pricerange as you and generally has the same use patterns as you that has good experience and then you may be able to seek an opinion from them on what you should get. So read up and narrow your choices down, get some opinions, ask lots of questions and then bite the bullet and buy something. the majority of this gear has pretty good resale value used and so sometimes the best thing is to just grab something, (or a few things) that meet your requirements. I would definitely recommend though, that if at all possible you should attempt to try before you buy. look for head-fi meets in your area if there is any coming up; there is a forum dedicated to meets, factory tours and get togethers, look for shops that will let you try stuff out; even some manufacturers will give you a 30 day return period so you can see if you like it or not (not so much with headphones though) you could also post in the members lounge that you would like to meet up with someone to try out some amps etc. you will find that we are a friendly bunch and some people are very generous with their time and equipment. The most important thing is to get your feet wet so to speak.

Quote:

So, here are some questions (really for general consumption, so I've phrased them in a way that is not specific to my specific needs for future readers): 1. What is the benefit of an amp? Why will it make my headphones sound better than if they were plugged straight into an IPod, or my computer, or a CD player, etc.

absolutely yes it will; depends on your CD player, but it is rare for much attention to be paid to the headphone out of an integrated amp. dedicated Headphone amps are just that, they are specifically designed to drive headphones. Headphones are much more sensitive than speakers, so they require a pretty clean amp to sound really good.

Quote:

2. What is the benefit of a DAC? Is this needed in all cases? For example, if someone is listening to music on a PC, isn't it already digital?

a DAC (Digital Analogue Convertor) converts the digital files (in your case WAV) into a waveform that you can hear. your computer will already have a dac as part of the circuitry in your soundcard; but it is unlikely to be any good. you only need a dac if you are using a digital source of course. the files on your computer may be digital, but the music is converted to analogue before it reaches the amp and therefor your headphones. buying a dedicated dac will mean that you get a far superior signal sent to the amp as the conversion will be much more accurate and dynamic.

Quote:

3. For headphones that are "easy to drive", I've read they don't need amps but can benefit from them. As I understand it this means they have low impedance (nope, don't know what that actually means) which is measured in Ohms. Looking at 50Ohm Sennheiser 555s, there seems to be a consensus that an amp won't provide much benefit. For the Sennheiser 595s though, there seems to be a much stronger contingent of people saying an amp is a very good idea to get the most out of them. Both are 50Ohm, so I don't get it.

sensitivity is only one aspect of the specs of a set of headphones and as the above poster said; it only really tells you how loud it will drive them, not how well. some amps will do a lot of buffering (mainly in portable amps) to bring the current up to a level that will provide enough current to drive harder to drive headphones to listen-able levels; but there is always a trade-off and in this case it would be that dynamics and often soundstage are reduced. the headphones will be loud, but they wont be reaching their potential as far as sound quality and detail goes. even easier to drive headphones do benefit from an amp IMO, especially in the bass detail/authority, extension at both ends of the spectrum and soundstage/separation. an amplifier takes the load off the source and therefor usually flattens out the frequency response and any bass-roll-off that may be inherant in the output stage of the source.

Quote:

4. For home use (as opposed to portable) is there any benefit to a "headphone amp" vs. a regular audio receiver?

yes; see above. most HP amps in integrated devices are an afterthought and usually not a great deal of thought has gone into the design. there are exceptions but as a rule you will get better performance out of a headphone amp. (as you would expect)

Quote:

Ok, getting specific to my situation here now. I have an old Yamaha RXV-1000 receiver collecting dust since I replaced it with a new Denon AVR-3808CI for my home theater setup. Can the Yamaha receiver be used for as good effect as a headphone-specific amp, such as the Headroom Micro Amp? For my particular situation I'd be attaching this to my home computer from which I play lossless music WAV files, as well as for gaming. I'm assuming for the receiver I'd run an optical audio cable from the optical out on the soundcard (yep, confirmed I have one) to the optical in on the receiver, plug in the headphones to the receiver and I'd be good to go. Is this a good or bad idea, and why? Aside from the monstrous size of the receiver since we'll pretend for the moment that it doesn't matter. Would setup for a headphone amp be basically the same? Does the receiver include a DAC, and does that even matter?

I dont have any specific experience with your receiver, but I can almost definitely say that if you buy a nice dac/amp you will get much better sound from your system. something like the DAC1 or one from beresford is good because it actually already has a pretty nice HP out on it. then if you feel you want more, you can buy a dedicated amp. the apogee duet is proving to be a really nice piece of kit too. its basically an external soundcard for your computer, but people are having great results using it with headphones and makes a really great source for an amp. But I wont go into any recommendations here because you need to go off and think a bit more about your needs, maybe try out a few things and then come back with a budget and goal in mind. also if you could tell us what sort of music you like that would help.

Quote:

Thanks in advance for all the forthcoming friendly, helpful replies that I will no doubt be inundated with.

there you go; I hope my response met your lofty expectations

good luck!!

oh I almost forgot the traditional welcome and salutation 'welcome to head-fi; sorry about your wallet!' and how true it is

 

[billybob_jcv]

There are 2 specs that you can look at to get an idea if a particular headphone is "easy to drive".

The first is the impedance - the higher the impedance of the headphone, the harder it is for the current to flow from the amp to the headphone. It's an over-simplification, but impedance basically represents how much power the source needs to deliver the signal to the load. (all the EEs can now jump to their feet in outrage)

The second is sensitivity, also sometimes called efficiency. For headphones, it's typically measured in dB/mW. This represents how much volume the headphone can generate from a 1 milliwatt input signal. The higher the sensitivity, the easier they will be to drive.

Usually, high impedance 'cans have low sensitivity and low impedance 'cans have high sensitivity, but there are exceptions.

There are similar concepts in speakers, but it isn't exactly the same. There's also lots more to it than just these oversimplifications - like available current & voltage draw, variability with frequency, etc - but that's a different lesson (and also a different professor).

Oh, and welcome to head-fi, sorry about your wallet!

 

[krmathis]

1. Depending on the amplifier, but in most cases yes.
2. You actually get to hear the audio. Cause unless you have an analog source (vinyl, tape) you need a DAC to convert from digital to analog.
3. And the question is?
4. Yes, is most cases. Since its specifically built for target of driving headphones.

 

[ReadNLearn]

Thanks a lot for the replies so far guys. Figuring out where to start with all this is pretty daunting.

Sounds like my idea of using my old Yamaha receiver in place of a dedicated headphone amp is probably not a good one. So now the true research will begin into what the amp options are. Plus I'll have to decide a budget. Convincing the wife I need to pay a few hundred dollars for one or two little boxes on my desk that don't look like much may not be the easiest thing.

Of course once I've got things figured out at home then I'm probably going to want an additional setup for my office. "Sorry about your wallet" indeed...

Any thought ever been given to a complete newbies guide? The more accessible this site is, and in turn the information, the more people that will stick. I spent several hours of reading different sites just to figure out some basic questions to even ask. I know a few people with enormous budgets who wouldn't hesitate to drop big money on this kind of equipment, but there is no way they would ever spend this kind of time to research it. Not everyone is looking for a whole new research hobby. They just want good sound.

Thanks again everyone!

 

[billybob_jcv]

I'm not so sure I would be so quick to dismiss the Yamaha receiver. I would definitely try it before dropping cash on a dedicated headphone amp. It's true that the headphone port on many receivers isn't great, but it's typically much better than your computer headphone jack. The good news is that most receivers can drive high impedance 'phones very well. I used 600 ohm Sennheiser HD420 'phones on a stereo amp for many years and I only found out they were "hard to drive" when I tried them on an ipod...

 

[rvikul]

My recommendation for friends who are noobs in this area is usually to start small. Most of my friends (and my wife) cannot tell the difference between a Sanyo boombox and a $2000 system. I tell them they are very lucky

to have saved a lot of money.

If you have a friend who has a decent audio rig, I would suggest you take some of your own CDs/MP3 player to his/her place and see if you hear a lot of difference. IMHO, thats a good first step before you go tumbling down the rabbit hole.

If you do find out that you have expensive ears, sorry about your wallet.

 

[ReadNLearn]

Unfortunately, I'm "that friend" that people go to. I just don't know very much about what to buy. But in general I seem to have a vastly lower tolerance for crummy sound than the people around me. I've got some Martin Logan speakers for my home theater setup, and a reasonable Denon receiver. I'm not looking to spend tons and tons of money at this point in time, so it's relatively simple.

What has led me here so far is that my current gaming headphones SteelSound 5H died due to a tramatic experience with my 5 year old daughter. The SteelSounds are definitely nothing special at all sound quality wise, but I bought them when the integrated volume control and retractable mic were important options. Now I'm listening to a lot more music at my computer rather than just gaming. So that got me looking at headphones, and the Sennhesier 595s seem like a reasonable price point with all-round good performance and a lot of positive feedback from people. That in turn led me to suggestions of headphone amps, and thus I am here.

For music, I listen to a pretty broad range. From heavy metal and J-Pop to U2 to Beethoven to Vanessa-Mae to opera. In particular I've been listening to a lot of violin and opera lately. But there are certainly times I want to break out the dance beats. But I REALLY appreciate when a solo aria can take me to the stratosphere.

Gotta run for now, but thanks for the comments.

 

[rvikul]

Quote:

Originally Posted by ReadNLearn /img/forum/go_quote.gif Unfortunately, I'm "that friend" that people go to.

LOL! I hear you. I am always stuck when friends and colleagues come to me and go "Hey I heard you are the audio expert. Can you suggest a good home theater system?". After a few basic questions, I have to turn them away with "Dont ask me. I am too expensive for you".

For people like us, we are a rare breed and head-fi is our temple.

What would I do without online forums??!

 

[scytheavatar]

Quote:

Originally Posted by ReadNLearn /img/forum/go_quote.gif 1. What is the benefit of an amp? Why will it make my headphones sound better than if they were plugged straight into an IPod, or my computer, or a CD player, etc.

Some headphones require a minimum amount of power supplied to them, if you don't give them enough power they are going to sound terrible, parts of the sound spectrum is going to disappear. For your imformation the HD595 isn't what I call an easy to drive headphone, so I will certainly recommend an amp for it.

Quote:

Originally Posted by ReadNLearn /img/forum/go_quote.gif 2. What is the benefit of a DAC? Is this needed in all cases? For example, if someone is listening to music on a PC, isn't it already digital?

The sound quality from most onboard sound cards can only be describe as being utter turd... the short answer is that a dedicated DAC will almost certainly outperform the onboard sound unless that DAC is useless. And for your information it'll outperform most portable players too, especially ipods.

Quote:

Originally Posted by ReadNLearn /img/forum/go_quote.gif 3. For headphones that are "easy to drive", I've read they don't need amps but can benefit from them. As I understand it this means they have low impedance (nope, don't know what that actually means) which is measured in Ohms. Looking at 50Ohm Sennheiser 555s, there seems to be a consensus that an amp won't provide much benefit. For the Sennheiser 595s though, there seems to be a much stronger contingent of people saying an amp is a very good idea to get the most out of them. Both are 50Ohm, so I don't get it.

Generally amps will improve your sound, but I will tell you a few things: firstly, your choice of amps certainly do have an effect on your sound, but your choice of headphones will have a bigger effect on your sound. You can get the HD555 and an amp, but no matter how good an amp you get the HD555 is just an entry level phone and sounds $100 at best. Upgrading your headphone is likely to give you a better sound than upgrading your amp. Secondly, there's a lot more snake oil and dubious value for money in the amplifier world than in the headphone world. For these reason I suggest that you don't worry too much about amps as a newbie and worry more about what headphone you are getting.

PS. For your information the HD595 sucks and I would recommend you not to get it, you can do much better at the price point.

 

[Uncle Erik]

1. Amps are more about control than they are about volume. There are technical reasons for this that I won't get into here, but the quality of sound depends on how well the amp makes the driver start and stop. The better it controls the starting and stopping, the better the sound will be on the other side. Now, everything with a headphone jack has an amp in it. An iPod has an amp and a soundcard has an amp. The problem is that amplification takes a bit of power. iPods are engineered to have a long battery life, so not much power goes to its amp and it'll struggle with difficult headphones. Similarly, battery run amplifiers also struggle with difficult headphones and you won't get much performance from them. The best are amps that plug into the wall - house current gives plenty of power to an amp.

Whether you need an external amp, and what kind, depends entirely on the headphones you're using. IEMs and very efficient headphones will run just fine from an iPod. Something like an AKG K-1000 needs a power amp for loudspeakers to perform at its best. Most of the full sized headphones from Sennheiser, AKG and Beyerdynamic need a quality amp that plugs into the wall.

My advice is to find the headphones you want first then match an amp to them.

2. The primary advantage of an outboard DAC is to get the processing out of the computer. When you use high-end headphones, you will begin to hear the immense amount of noise a computer produces inside. Computers use a switching power supply, which is efficient, lightweight and cost effective. Unfortunately, a switching power supply throws off a mess of radio frequency interference (RFI) which works exactly like a radio broadcast. The noise transmits then is picked up by your soundcard and you hear the RFI hash. You'll also get RFI from case fans, hard drives and anything with an electric motor inside the computer. The best way to deal with the noise is to move the audio processing outside the box.

3. Not many people understand impedance here. Low impedance does not mean easy to drive. If that were the case, something like a 1.2 Ohm pair of Apogee ribbons would be easily driven by an iPod. Problem is that Apogees will literally melt lesser amps - they'll actually make an amp overheat and kill itself. Impedance is only useful in context. You have to know the output impedance of the amp you're using, too. Once you know the headphone impedance and the amp's output impedance, you can use a formula to tell you how much power transfers from the amp to the headphones.

Once you know how much power transfers, then you use the sensitivity (measured in dB) of the headphones to tell you how loud they will get given the power that gets through.

There's one more important angle to this, which is the damping factor. Damping factor is the ratio of the amp's output impedance to the impedance of the headphones. The lower the output impedance is compared to the impedance of the headphones, the more control the amp has over the headphones. This gets back to the point in #1, where you want as much control over the drivers as possible. There's more to this (of course), but I hope you're beginning to see how this all ties together.

4. Sure, some receivers do a good job of powering headphones. The problem is that there are tens of thousands of different models, so you're not going to find much information on what works well with particular headphones. Still, I strongly recommend you jack your headphones in for a listen before you buy a dedicated headphone amp. If it sounds good, congrats, you don't need to buy anything else. There are some differences between receivers and headphone amps, though. For one, most receiver headphone jacks are run right off the power output with a few resistors in the way to drop the power down. That's not quite as good as using an amp specifically designed for headphones. Also, most receivers run in class AB, while most headphone amps run in class A. Class A is preferable to class AB. There are many lengthy technical reasons for this, but there's almost no controversy on the point. Another good reason is the vacuum tube. If you've never listened to one, you should some time. Some prefer solid state, but lots of us love tubes. Tubes give (in my opinion) a slightly magical, yet realistic, sound to music. You won't find a tubed receiver, but there are many tubed headphone amps. If you like the sound of tubes, then there's no better way to get it than with a tubed headphone amp.

 

[ReadNLearn]

Well, I spent about 15 hours over the weekend doing research on headphones, amps, DACs, and what it all means to me. Once I started to figure out what the questions were, I found that the answers are there, and almost always in these forums. So again, let me say thank you to all of you for your helpful posts.

Here are some decisions I've made, and why. Hopefully this will be helpful to anybody in the future who happens to come across this thread with some of the same thoughts and questions as me, and wonders what I decided.

Heaphones:
I live in a relatively small city and the only headphones carried by the 4 or so "high-end" audio stores were Sennheiser. So I demoed the 595s and 650s. I've decided on the Sennheiser HD-650, although I would have liked to have demoed the Beyerdynamic DT880s and the Denon AH-D2000/5000. I live in Canada and I'm not aware of any online places that have a really good return policy, and the stores all have restocking fees, or I'd buy everything I'm interested in and then return all but the one I choose. The HD650 decision was made easier by a really good deal I discovered at the last minute. More on that below.

Amp/DAC:
I'm new to all this, so I didn't want to go too nuts here. Obviously a LOT of money can be spent on components, but I was really looking for bang for the buck. I settled on the HeadRoom Micro Amp and Micro DAC. I read through a lot of reviews and forum posts. It was hard to find much negative but there was tons of positive comments. I particularly liked when people compared the Micro line to components priced considerably higher and found the Micro line to be better. So I feel like this is a pretty good starting point for me.

Why a DAC?
I now understand more clearly why I need a DAC and what it will do for me. Keeping in mind my main purpose for all this was listening to music from my computer, as well as gaming. The DAC built into regular sound cards is not very good, so all sound coming from the regular analog outputs at the back of the sound card will not have good sound. By using the optical out from the sound card to another component with a DAC, that one will be used instead. I tested this over the weekend by plugging in some not particularly good headphones to my old Yamaha receiver. I ran an optical audio cable from the soundcard to the receiver. The sound sound was noticeably better than straight from the sound card. The HeadRoom Micro DAC should be much much better from what I've read, and this should be vastly more noticeable with good headphones, such as the Sennheiser HD650s.

Living in Canada, I was unsure of the shipping costs, etc. So, I started adding things to the shopping cart on HeadRoom's website. Then I noticed a link on the shopping cart page for discount codes. Turns out they have one for the HD650s. Including that discount, plus their already reasonably low regular price compared to other sources, this made the 650s a very nice bargain. So that sealed the deal for me. Bam, I pulled the trigger late last night, and the Micro Amp, DAC, HD650s, and a couple of cables are a done deal.

Now I'm just hoping the cost of duty, brokerage, etc. isn't going to be too ridiculous at the border.

 

[qusp]

Quote:

Originally Posted by Uncle Erik /img/forum/go_quote.gif 1. Amps are more about control than they are about volume. There are technical reasons for this that I won't get into here, but the quality of sound depends on how well the amp makes the driver start and stop. The better it controls the starting and stopping, the better the sound will be on the other side. Now, everything with a headphone jack has an amp in it. An iPod has an amp and a soundcard has an amp. The problem is that amplification takes a bit of power. iPods are engineered to have a long battery life, so not much power goes to its amp and it'll struggle with difficult headphones. Similarly, battery run amplifiers also struggle with difficult headphones and you won't get much performance from them. The best are amps that plug into the wall - house current gives plenty of power to an amp. Whether you need an external amp, and what kind, depends entirely on the headphones you're using. IEMs and very efficient headphones will run just fine from an iPod. Something like an AKG K-1000 needs a power amp for loudspeakers to perform at its best. Most of the full sized headphones from Sennheiser, AKG and Beyerdynamic need a quality amp that plugs into the wall. My advice is to find the headphones you want first then match an amp to them. 2. The primary advantage of an outboard DAC is to get the processing out of the computer. When you use high-end headphones, you will begin to hear the immense amount of noise a computer produces inside. Computers use a switching power supply, which is efficient, lightweight and cost effective. Unfortunately, a switching power supply throws off a mess of radio frequency interference (RFI) which works exactly like a radio broadcast. The noise transmits then is picked up by your soundcard and you hear the RFI hash. You'll also get RFI from case fans, hard drives and anything with an electric motor inside the computer. The best way to deal with the noise is to move the audio processing outside the box. 3. Not many people understand impedance here. Low impedance does not mean easy to drive. If that were the case, something like a 1.2 Ohm pair of Apogee ribbons would be easily driven by an iPod. Problem is that Apogees will literally melt lesser amps - they'll actually make an amp overheat and kill itself. Impedance is only useful in context. You have to know the output impedance of the amp you're using, too. Once you know the headphone impedance and the amp's output impedance, you can use a formula to tell you how much power transfers from the amp to the headphones. Once you know how much power transfers, then you use the sensitivity (measured in dB) of the headphones to tell you how loud they will get given the power that gets through. There's one more important angle to this, which is the damping factor. Damping factor is the ratio of the amp's output impedance to the impedance of the headphones. The lower the output impedance is compared to the impedance of the headphones, the more control the amp has over the headphones. This gets back to the point in #1, where you want as much control over the drivers as possible. There's more to this (of course), but I hope you're beginning to see how this all ties together. 4. Sure, some receivers do a good job of powering headphones. The problem is that there are tens of thousands of different models, so you're not going to find much information on what works well with particular headphones. Still, I strongly recommend you jack your headphones in for a listen before you buy a dedicated headphone amp. If it sounds good, congrats, you don't need to buy anything else. There are some differences between receivers and headphone amps, though. For one, most receiver headphone jacks are run right off the power output with a few resistors in the way to drop the power down. That's not quite as good as using an amp specifically designed for headphones. Also, most receivers run in class AB, while most headphone amps run in class A. Class A is preferable to class AB. There are many lengthy technical reasons for this, but there's almost no controversy on the point. Another good reason is the vacuum tube. If you've never listened to one, you should some time. Some prefer solid state, but lots of us love tubes. Tubes give (in my opinion) a slightly magical, yet realistic, sound to music. You won't find a tubed receiver, but there are many tubed headphone amps. If you like the sound of tubes, then there's no better way to get it than with a tubed headphone amp.

well said erik

except for tubes vs. SS ... SS FTW