[Magick Man]

HiFiMan EF2A, it's a nice little tube amp/DAC combo for $170. I hear the Bravo Ocean hybrid amp is very good for $130ish bucks, but it has no integrated DAC.

 

[yakapo]

 
Quote:

HiFiMan EF2A, it's a nice little tube amp/DAC combo for $170. I hear the Bravo Ocean hybrid amp is very good for $130ish bucks, but it has no integrated DAC.

 
 
The HiFiMan EF2A looks like a great deal!  Would you recommend it over the Objective 2?
 
Thanks!!!!

 

[Tilpo]

The O2 has a very good reputation, but it does not have a built in DAC.

Asuming you do not have a proper DAC, it is better to get a decent combo.

I do wonder though, does the EF2A have enough power to properly drive the AKG's?
Because the K701 does need quite a bit of power.

 

[Chris J]

Quote:

The O2 has a very good reputation, but it does not have a built in DAC.
Asuming you do not have a proper DAC, it is better to get a decent combo.
I do wonder though, does the EF2A have enough power to properly drive the AKG's?
Because the K701 does need quite a bit of power.

In theory it has enough power to drive the K701 but you may not like the high output impedance of the EF2A.
Which is probably what most people don't like about a lot of "low powered" amps.
 

 

[Magick Man]

The HiFiMan EF2A looks like a great deal!  Would you recommend it over the Objective 2?
 
Thanks!!!!

I've not heard the O2, many owners rave about it, but the EF2A is a nice sounding little amp and it properly drives just about everything I own. I don't use it with my Denons due to impedance issues, but it still sounds fine with them.

The O2 has a very good reputation, but it does not have a built in DAC.
Asuming you do not have a proper DAC, it is better to get a decent combo.
I do wonder though, does the EF2A have enough power to properly drive the AKG's?
Because the K701 does need quite a bit of power.

It drives my Q701s without issue, though without quite as much authority as my EF5. But then, that's a big difference in amps. The EF5 is a beast for its price.

 

[yakapo]

Can someone explain this to me..

OW IMPEDANCE: A low impedance headphone often will be louder out of a portable device. However, in many cases, it is still highly recommended to pair a low impedance headphone with a headphone amplifier. The reason for this is that typically a low impedance headphone will sound far better when fed more electrical current. A low impedance headphone’s frequency response can be dramatically altered and improved (especially in the bass region) when paired with a headphone amplifier offering sufficient current. In some rare cases, there are low impedance headphones such as the AKG Q701 which require high current not only to sound their best, but to reach satisfactory volume levels as well. This is an example of an instance where the headphone’s impedance rating is not very high, but its sensitivity is not very high either. This means that more power is required to drive the headphones.

Thanks in advance.

 

[Tilpo]

Can someone explain this to me..
OW IMPEDANCE: A low impedance headphone often will be louder out of a portable device. However, in many cases, it is still highly recommended to pair a low impedance headphone with a headphone amplifier. The reason for this is that typically a low impedance headphone will sound far better when fed more electrical current. A low impedance headphone’s frequency response can be dramatically altered and improved (especially in the bass region) when paired with a headphone amplifier offering sufficient current. In some rare cases, there are low impedance headphones such as the AKG Q701 which require high current not only to sound their best, but to reach satisfactory volume levels as well. This is an example of an instance where the headphone’s impedance rating is not very high, but its sensitivity is not very high either. This means that more power is required to drive the headphones.
Thanks in advance.

What is there to explain? Higher impedance means higher voltages to generate the same current, and in many cases amplifiers are what supply these higher voltages (higher than portable setups, at least).
However, when paired with low impedance cans that need a lot of current, they might become unstable and supply insufficient current. For obvious reasons portable sources tend to fail both in supplying a lot of current or voltage.

If a source is at its limit in supplying current, distortion goes up dramatically. But more importantly, distortion goes up more in some frequencies than it does in others. Additionally, in many cases the amplifier can't supply enough current in one frequency, but it can in another. This is why bass response might fall in volume and become distorted with some combinations of amplifiers and headphones.

Cans such as the AKG K701, but especially the Hifiman HE-6, need a lot of current while not being of very high impedance. This makes it very hard to drive for many amplifiers, and as a result getting the right amplifier is very important.


What I just said is based on what I've read from other people. I have no credible source to back this up, therefore I would like someone to either confirm or correct what I just said.

 

[Chris J]

Try reading this:
 
http://www.head-fi.org/a/headphone-impedance
 
I hope it helps!

 

[obobskivich]

Just gonna throw this out there; sure it will get ignored: you will not fundamentally change any headphone with the amplifier. Amplifiers are not tone control devices. And finally, amplifiers will not "widen the soundstage" - that's part of the headphone's design (and there's not a lot out there that gets "bigger" than the 70x). They're gonna sound like 70x's forever.
 
The 70x don't require anywhere near the same power inputs as many planars; 1-2 mW is not earth-shattering in most cases (that's mW, not W). The output impedance "thing" is unlikely to produce a "wonky" (i.e. non-uniform) FR variation with the 70x (contrasted to something like the HD 650 or T1), simply because their impedance FR is fairly flat. If a given amplifier can provide suitable output power, it can drive them; and the output power available from an amplifier does not correlate to it's output impedance (nor does its price - there are many inexpensive amplifiers/devices with low output impedance and low output power, and many expensive devices with relatively "high" output impedance). The receiver is probably suitable, but without any information about it, it may not be. There's plenty of good options in your $100-$200 range, like the HiFiMan, the Fiio E9, the O2, and probably more used devices than you can shake a stick at. 
 
 
Quote:

I'm sure this has been discussed a dozen times but just in case someone has an opinion - please suggest an amp under $150 that will help widen the soundstage and warm up the headphones.  I listen to mostly rock and jazz.  I primarily bought these for listening to jazz trios and quartets - piano, upright bass, drums.   
 
btw if anyone can recommend some piano led jazz with lots of walking bass lines I'd appreciate it.   

 

 

[Chris J]

Mr. Spock here, I like italics
 
 
Quote:

What is there to explain? Higher impedance means higher voltages to generate the same current, and in many cases amplifiers are what supply these higher voltages (higher than portable setups, at least).

My two cents worth:   assuming you have two cans with the same sensitivity, i.e. need the same amount of power to generate the same SPL, but the two cans have different impedances, then the lower impedance can will need a bit more current, a bit less voltage.    The higher impedance can will need a bit more voltage, a bit less current.

However, when paired with low impedance cans that need a lot of current, they might become unstable and supply insufficient current.

My two cents worth:   if the cans need more current than the amp can supply, the amp will then current limit, i.e. music will be clipped (distorted). Instability is something a bit different.

For obvious reasons portable sources tend to fail both in supplying a lot of current or voltage.
If a source is at its limit in supplying current, distortion goes up dramatically. But more importantly, distortion goes up more in some frequencies than it does in others. Additionally, in many cases the amplifier can't supply enough current in one frequency, but it can in another. This is why bass response might fall in volume and become distorted with some combinations of amplifiers and headphones.

I assume you mean "can't supply enough current in one frequency band".  Basically I agree, but this would be dependent on the characterisitcs of the amp, the headphones, the type of music, the recording, you have an excellent point, but kinda hard to pin this down to just the amp or 'phones. Like I said, basically I agree.

Cans such as the AKG K701, but especially the Hifiman HE-6, need a lot of current while not being of very high impedance. This makes it very hard to drive for many amplifiers, and as a result getting the right amplifier is very important.

I own AKG Q701s, you can plug them into an iPad, they sound just fine. They even sound "OK" when plugged into an iPod, just don't expect too much sound quality or volume.  But if you want them to really show you what they can do, use a better headphone amp.   K701 & Q701 guys love the Matrix M Stage.

What I just said is based on what I've read from other people. I have no credible source to back this up, therefore I would like someone to either confirm or correct what I just said.

And I hope I didn't give any offence, there was none intended.
 
 

 

[obobskivich]

Mr Scott will mostly have to agree Captain, but if you've got a device that specifies it's power into your load's impedance (or close enough), and your load has a fairly flat IFR, and your device's output power exceeds your demands, it shouldn't matter what voltage or current actually pans out to be. That, and we need more dilithium!
 
 
 
 
 

 

[Tilpo]

Just gonna throw this out there; sure it will get ignored: you will not fundamentally change any headphone with the amplifier. Amplifiers are not tone control devices. And finally, amplifiers will not "widen the soundstage" - that's part of the headphone's design (and there's not a lot out there that gets "bigger" than the 70x). They're gonna sound like 70x's forever.
 
The 70x don't require anywhere near the same power inputs as many planars; 1-2 mW is not earth-shattering in most cases (that's mW, not W). The output impedance "thing" is unlikely to produce a "wonky" (i.e. non-uniform) FR variation with the 70x (contrasted to something like the HD 650 or T1), simply because their impedance FR is fairly flat. If a given amplifier can provide suitable output power, it can drive them; and the output power available from an amplifier does not correlate to it's output impedance (nor does its price - there are many inexpensive amplifiers/devices with low output impedance and low output power, and many expensive devices with relatively "high" output impedance). The receiver is probably suitable, but without any information about it, it may not be. There's plenty of good options in your $100-$200 range, like the HiFiMan, the Fiio E9, the O2, and probably more used devices than you can shake a stick at. 
 
 


 

Well said.

But the impedance of the K701 does go up with frequency. If you would have an amp with an output impedance of about 60-70 ohms, then there could be quite dramatic effects on the frequency response.
Additionally there is the fact that lower impedance does increase the dampening factor. Although I don't know how much of an issue it is with headphones if you have a low dampening factor.

Impedance - frequency graph of the AKG K701

 

[obobskivich]

Electrical damping (damping factor) is largely marketing hype.
 
As you increase the output impedance of the amplifier, you will attenuate the signal unevenly wrt impedance and the load, but it's usually not "extreme" and it isn't "random" - it will be a uniform non-linearaity (it won't change wrt signal). Usually devices with high output impedances also have a lot of power "behind" them (and that output impedance is just a resistor network to bring power down to protect the headphones), so the attenuation is rarely a problem (you're unlikely to have something that clips at 1 mW and has an output impedance of 200 ohms, it's more likely to be 1000 or 5000 mW into 300-400 ohms, because the actual amplifier in these cases is usually 100-200W). That just leaves your FR output (and this does not mean the device itself is somehow not flat, it's linear; it's that the FR of the transducer will deviate from whatever "absolute" should be) - you won't ever know about this unless you're doing ABX comparisons to another amplifier (and it really has to be this quickly together, as your perceptual memory is nowhere near good enough to "listen to amp A last week and amp B today and tell us the differences"). I forget what the JND is stated as for FR variation and audibility (it has been figured out though!), I want to say 2 dB though. And none of that is saying that X is "bad" and Y is "good" - it's just saying that you can pick them apart with reasonable confidence in a proper test (which means there is an actual audible difference, which is when we can actually care about something - it really doesn't matter what goes on right up to the JND, at all). 
 
So basically, when you've got people (I should say, a few amplifier manufacturers who are trying to espouse the advantages of their extremely low output impedance amplifiers (which is something we've seen in home-theater/"big" systems for the last 30 years)) showing you graphs with a headphone's FR and going "look at this huge deviation" - the questions you should be asking are: Will this be audible? And if it will be audible, will it even matter? (This of course assumes you haven't gotten ahead of yourself and asked: What's the bias here, and is this credible?).
 
Obviously if it's something as dramatic as the Afro-Tech article (Which was similar to what you'd expect with an HPF), yeah that will matter. If it's a 1 dB bump or dip at 100hz, ignoring that you probably won't even notice it (I'll guarantee you won't if you aren't comparing to something else), it isn't the end of the world. This all assumes the device can actually drive the load without clipping (that's an entirely different thing, and a very bad thing at that). Trying to use an amplifier to adjust the sound of your headphones is a losing battle - if it can drive them to a suitable level without clipping it's done it's job, if you don't like how they sound then you'll probably be best served by getting different headphones. Just as an observation (now leaving the science portion of the program): it seems that many people purchase "reference" headphones, like the 70x, and expect to be "wowed" right out of the box. In many cases they aren't; which leads them to want to invest tons of money to "get the most out of" their new purchase ("help me widen the soundstage"; "help me bring out the bass"; "help me increase the clarity" - and I'm always asking: "relative to what?!"). Reality is, the headphones probably just aren't for them. I've read this observation quite a bit wrt the DT48, but I believe it can be more wide-ranged with other "reference" cans like the 70x. I know this is a very common trend with speaker/theater systems - someone buys whatever equipment and when it doesn't meet or exceed their image of how it should work, they will usually start dumping money into electronics, cables, tweaks, and nonsense. There's plenty of people out there willing to separate those people from their money.
 
Quote:

Well said.
But the impedance of the K701 does go up with frequency. If you would have an amp with an output impedance of about 60-70 ohms, then there could be quite dramatic effects on the frequency response.
Additionally there is the fact that lower impedance does increase the dampening factor. Although I don't know how much of an issue it is with headphones if you have a low dampening factor.
Impedance - frequency graph of the AKG K701

 

 

[Tilpo]

I find myself to be generally agreeing to what you just said, except for that I was convinced that output impedance and dampening factor did have an audible effect on the sound.

I'm aware that the damping factor is very much marketing hype, but I believe I have read an article or two that showed the importance of a good dampening factor. I'll try and see if I can find them.

I'm also aware of the fact that many changes claimed by manufacturers are simply not audible. I have read multiple books on acoustics and pscychoacoustics, and therefore I do have a basic understanding of what is audible and what is not.


I wish more people on this forum shared a more objective view towards this subject. It could help so many newbies avoid unnecessary spending.


Oh, and rather than saying 'it's simply not for them' when you are not wowed when listening to a hi-fi can for the first time, I think the best advice is to let someone listen to them for some time. I was personally very disappointed when I first got my HD 650's, since I simply expected a lot more performance for 550 euros (I paired it with a Little Dot MKIV). However as time went by you learn to recognize the difference, and when I now listen to even my HD 25 I can still say with great confidence that the HD 650's are worth the money I spent on them. I takes time to appreciate a headphone.

And I hope I didn't give any offence, there was none intended.
 
 

None taken. I'd rather like to thank you instead.

 

[obobskivich]

Here you go:
http://www.roger-russell.com/wire/dampaugs.htm
 
As far as your argument about time, I do agree with that (with some reservations). I'm not trying to make any sort of "unwashed masses" type argument, but essentially: there's a reason the "hi-fi smile" exists and that many mainstream products have the sound signature they do. It isn't to do with customers being "ignorant" - it's what people (tend to) want (and this is based on both lab and market research). We don't hear "flat" (or anything approaching it), and that influences our tastes. There's a reason that "bass sells" in many cases, and it isn't some sort of "scheme" to rip people off. 
 
 
Quote:

I find myself to be generally agreeing to what you just said, except for that I was convinced that output impedance and dampening factor did have an audible effect on the sound.
I'm aware that the damping factor is very much marketing hype, but I believe I have read an article or two that showed the importance of a good dampening factor. I'll try and see if I can find them.
I wish more people on this forum shared a more objective view towards this subject. It could help so many newbies avoid unnecessary spending.
Oh, and rather than saying 'it's simply not for them' when you are not wowed when listening to a hi-fi can for the first time, I think the best advice is to let someone listen to them for some time. I was personally very disappointed when I first got my HD 650's, since I simply expected a lot more performance for 550 euros (I paired it with a Little Dot MKIV). However as time went by you learn to recognize the difference, and when I now listen to even my HD 25 I can still say with great confidence that the HD 650's are worth the money I spent on them. I takes time to appreciate a headphone.