Head-Fi.org › Forums › Equipment Forums › Portable Headphone Amps › Portable Amp Questions
New Posts  All Forums:Forum Nav:

Portable Amp Questions

post #1 of 6
2/6/12 at 1:56pm
Thread Starter 

I current use an iPhone 4S directly to my Sennheiser HD25-1 IIs without an amp.  I'm new to the whole hifi thing, and I'm only starting to develop my ear.  

 

I'd like to get some nicer headphones and know that I will need an amp to power them.  However, most other posts seem to be regarding budget amps, and I'm not really afraid of cost.  If I wanted to drive something like a pair of HD700s from an iPhone source, would this even be possible?  

 

I've looked at the Pico Slim, TTVJ, and ADL Stride/Cruise, but I don't really know enough yet to judge I think.

 

I'd like a portable amp over a desktop amp since my source is an iPhone/laptop audio port for the most part.  

Reply
post #2 of 6
2/6/12 at 3:00pm

Many of the upper tier Sennheiser headphones are hard to drive due to two main reasons.

 

1.)  The frequency dependent impedance curve

2.)  The current and thus power needed to properly control both the driver and voice coils

 

Take a look at this graph:

http://graphs.headphone.com/graphCompare.php?graphType=7&graphID[]=853

 

See how the impedance goes from a nominal 300 Ohms to a whopping 450 at the fundamental and then waves up again around 10 kHz?  This is a sign of a hard to drive headphone.  It is hard for a source to properly power such headphones because the output impedance from an amp is fixed.  When the impedance changes on the headphones the amp, assuming the amp was satisfied with the impedance match in the first place, the power to the driver and voice coil changes.

 

In addition to the impedance issue many of the upper tier Sennheiser headphones are really laid back.  They sound as if you are listening to your music through a pillow which can really drive you crazy over time.  Not only that they tend to need to be turned up to generate a full sound.  This is especially true with the HD-650 and HD-800 and I do not think the HD-700 will be any different.  I am not saying there is not a market or need for said headphones, but I did not like them and I tried for years to delude myself of this fact.

 

May I suggest something like the Denon AH-D2000.  The impedance curve is almost ruler flat making the driver and voice coil much easier to control.  They are a spectacular headphone and really fun to listen to.  They are not entirely neutral sounding, but I listen to enjoy my music most of the time rather than analyze it.

 

If you are looking at the $1000 mark you should really get your ears some LCD-2 Rev 2 headphones.  They are much more up-front sounding than the HD-650 and HD-800.  They are also much more neutral sounding.  I mean look at the frequency response below.  Ruler flat to 1 kHz.

http://www.innerfidelity.com/images/AudezeLCD2Rev2.pdf

 

They were a bit clunky and are in no way portable.  They also did not sound as amazing as my Denon AH-D2000 do with most of my music.  The LCD-2 is a little more selective as to what sounds really great with it.

http://graphs.headphone.com/graphCompare.php?graphType=7&graphID[]=2881

 

The Denon AH-D2000 is also nice because you do not need an amp to get decent sound out of them.  They have a relatively high sensitivity and low impedance making it easy for a portable device to power them.  I must admit that they really do not shine until you match them with a really nice amp that properly controls the current to the drivers and voice coils.  The AH-D2000 and Grace m903 is one of those combos that remains incredibly immersive with 90% of my music library.  Using something like the Bithead will work fine and improve the sound over a portable player like an iPod, but you really need something a bit more powerful to unleash their full glory.

 

I highly recommend the Bithead and Denon AH-D2000 combo.

http://www.headphone.com/packages/headroom-total-bithead--denon-d2000-package.php

 

or

 

Headamp Pico with USB Dac

$500 with DAC $400 with just the headphone amp.

 

I really do not feel that your portable device will properly power a headphone with a sensitivity below 99dB and with an impedance greater than 100 Ohms.  I am sure there may exist exceptions, but those are my general limits for portable use unamped.  Amped of course you will be fine, but be aware of what you are buying and how difficult it may be to drive the headphones you are listening to.

Reply
post #3 of 6
2/6/12 at 3:19pm
Thread Starter 
Quote:
Originally Posted by NA Blur View Post

Many of the upper tier Sennheiser headphones are hard to drive due to two main reasons.

 

1.)  The frequency dependent impedance curve

2.)  The current and thus power needed to properly control both the driver and voice coils

 

Take a look at this graph:

http://graphs.headphone.com/graphCompare.php?graphType=7&graphID[]=853

 

See how the impedance goes from a nominal 300 Ohms to a whopping 450 at the fundamental and then waves up again around 10 kHz?  This is a sign of a hard to drive headphone.  It is hard for a source to properly power such headphones because the output impedance from an amp is fixed.  When the impedance changes on the headphones the amp, assuming the amp was satisfied with the impedance match in the first place, the power to the driver and voice coil changes.

 

In addition to the impedance issue many of the upper tier Sennheiser headphones are really laid back.  They sound as if you are listening to your music through a pillow which can really drive you crazy over time.  Not only that they tend to need to be turned up to generate a full sound.  This is especially true with the HD-650 and HD-800 and I do not think the HD-700 will be any different.  I am not saying there is not a market or need for said headphones, but I did not like them and I tried for years to delude myself of this fact.

 

May I suggest something like the Denon AH-D2000.  The impedance curve is almost ruler flat making the driver and voice coil much easier to control.  They are a spectacular headphone and really fun to listen to.  They are not entirely neutral sounding, but I listen to enjoy my music most of the time rather than analyze it.

 

If you are looking at the $1000 mark you should really get your ears some LCD-2 Rev 2 headphones.  They are much more up-front sounding than the HD-650 and HD-800.  They are also much more neutral sounding.  I mean look at the frequency response below.  Ruler flat to 1 kHz.

http://www.innerfidelity.com/images/AudezeLCD2Rev2.pdf

 

They were a bit clunky and are in no way portable.  They also did not sound as amazing as my Denon AH-D2000 do with most of my music.  The LCD-2 is a little more selective as to what sounds really great with it.

http://graphs.headphone.com/graphCompare.php?graphType=7&graphID[]=2881

 

The Denon AH-D2000 is also nice because you do not need an amp to get decent sound out of them.  They have a relatively high sensitivity and low impedance making it easy for a portable device to power them.  I must admit that they really do not shine until you match them with a really nice amp that properly controls the current to the drivers and voice coils.  The AH-D2000 and Grace m903 is one of those combos that remains incredibly immersive with 90% of my music library.  Using something like the Bithead will work fine and improve the sound over a portable player like an iPod, but you really need something a bit more powerful to unleash their full glory.

 

I highly recommend the Bithead and Denon AH-D2000 combo.

http://www.headphone.com/packages/headroom-total-bithead--denon-d2000-package.php

 

or

 

Headamp Pico with USB Dac

$500 with DAC $400 with just the headphone amp.

 

I really do not feel that your portable device will properly power a headphone with a sensitivity below 99dB and with an impedance greater than 100 Ohms.  I am sure there may exist exceptions, but those are my general limits for portable use unamped.  Amped of course you will be fine, but be aware of what you are buying and how difficult it may be to drive the headphones you are listening to.



 

 

Thanks so much for the feedback. I'm trying to lurk and learn as much as possible, but felt like I had to make a post at some point.  The wiki has a good overview of impedance, but not really enough to tell me what to look for.  I'm definitely not sold on the HD700s, I just know that from my reading that they're an example of something hard to drive.  I know I'll need an amp, but I don't have an understanding of why I might need a DAC or an LOD or anything really.  I'll read the links you provided, really appreciate it.

 

 

Reply
post #4 of 6
2/6/12 at 4:07pm

You will need a LOD (line-out dock) to channel the analog audio signal from the USB port of your iPhone 4S to the amp. I've spend a fair amount on custom-made LODs and recently switched to a more flexible and seemingly more rugged $10 FiiO L3 LOD from Amazon vendor. Can't tell much of a audible difference, so I wouldn't recommend spending the $50-100 that some companies ask.

 

The DAC is for converting digital signal from a laptop or iPad into an analog sound for your amp to amplify. Short story: It doesn't have an application with your iPhone 4S unless you want to buy one of the 2 or 3 very expensive high-end amps that have the right USB input port.

 

But having a DAC (like I do with my Pico (not Slim)) is nice when I'm traveling and want to serve up the music from my MacBook. It's become more useful after I realized months ago that you can output the digital signal from an iPad using the Apple Camera Connector > USB > Pico DAC.

 

Hope this helps. There are a few nuances to what I've written, but it should be a good primer for your needs.

Reply
post #5 of 6
2/6/12 at 4:22pm
Thread Starter 
Quote:
Originally Posted by mchang View Post

You will need a LOD (line-out dock) to channel the analog audio signal from the USB port of your iPhone 4S to the amp. I've spend a fair amount on custom-made LODs and recently switched to a more flexible and seemingly more rugged $10 FiiO L3 LOD from Amazon vendor. Can't tell much of a audible difference, so I wouldn't recommend spending the $50-100 that some companies ask.

 

The DAC is for converting digital signal from a laptop or iPad into an analog sound for your amp to amplify. Short story: It doesn't have an application with your iPhone 4S unless you want to buy one of the 2 or 3 very expensive high-end amps that have the right USB input port.

 

But having a DAC (like I do with my Pico (not Slim)) is nice when I'm traveling and want to serve up the music from my MacBook. It's become more useful after I realized months ago that you can output the digital signal from an iPad using the Apple Camera Connector > USB > Pico DAC.

 

Hope this helps. There are a few nuances to what I've written, but it should be a good primer for your needs.


Thanks for the reply.  Which 2-3 high-end amps are you referring to?  Also, just to make sure I get this, the DAC when used with the MacBook is probably connected via USB and bypasses using the headphone port of the MacBook to get a digital straight through to the DAC before going into the amp?

 

Reply
post #6 of 6
2/7/12 at 7:22am

You are correct in regards to the MacBook and DAC.

 

As for the high-end amps, check out this post:

http://www.head-fi.org/t/593616/can-somebody-supply-a-list-of-all-portable-amp-manufacturers#post_8110482

 

I'm not experienced with the amps mentioned, but I think the one brand is Fostex, not Foster. Good luck.

Reply
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Portable Headphone Amps
Head-Fi.org › Forums › Equipment Forums › Portable Headphone Amps › Portable Amp Questions