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How to know if i am underamping?

post #1 of 8
Thread Starter 

Hi all.  I think this subject was brought up sometime but I can't exactly locate the specific thread.

anyway,what are the signes for underamping a certain headphone?  or in other words,how can i know that i am properly amping my headphones?

 

I got a new M50 which i really love,they are rated at 38ohm impedance and 99db sensitivity.  they sound great out of my headroom SS amp (ofcourse..) and today out of curiosity i am trying them with my earmax pro  which is OTL design and not ideal for low impedance headphones.  the earmax pro as you know supposed to be better than the regular earmax in driving low impedance (upgraded power supply), and although technically the minimum requirements are at least 30 ohm the recommended impedance (at least by TAD site) is 60+.

 

anyway,just listening to the M50 out of the earmax and it sounds fine to me,can't notice anything suspicious that points on underamping,    what exactly are the sings of underamped headphones?  is it distortion of some kind...maybe the need to turn the volume pot all the way up to reach a normal volume level?

post #2 of 8

some other folks may be able to help more.

but, my general impression of underamped phone (i tried my 600 ohm dt990 out of an ipod just to be able to say for sure what "it" is) is that the sound will be flat, boring, not loud enough, and may even distort when certain big transients hit.

post #3 of 8

Floppy bass. 

post #4 of 8

For me it hasn't been an issue of sheer volume.  I've heard headphones with a lot of volume and yet they aren't well amp'd.  The first thing to suffer is usually the bass.

 

The Ed8's for example have a boomy bass and perhaps even more voluminous, when unamp'd.  Once, amp'd, the bass tightens up and becomes more controlled and less intrusive.  This is an even more marked phenomenon with the D5000's.  

 

With the HD650/600's, there's a loss of dynamism and energy in the sound.

 

In the end, I don't think you can tell a can is underamp'd unless you've heard them well amp'd. 

post #5 of 8
Thread Starter 

thanks for all the comments. but for example,i may have underamped the HD650 until now without even knowing...thinking that they were amped properly 

the main problem of this is to distinguish where exactly the line between "underamped" and  just  a different sound signature (of an amp) lies.  some tube amps for example have a rather lush and quiet sound signature and it may sound like they not have enough power like other SS amps.

sloppy bass sounds logical...I also read that maybe over piercing highs can be a result of underamping.     but i would also add that certain headphones like D5000 have sloppy and boomy bass even when amped propely so there is no real way of knowing for sure with them.


Edited by plonter - 5/8/10 at 4:05pm
post #6 of 8


     Quote:

Originally Posted by plonter View Post

thanks for all the comments. but for example,i may have underamped the HD650 until now without even knowing...thinking that they were amped properly 

 


The amp salesmen would be sitting and reading your comments with much interest.   Get yourself a SPL Auditor or a Carey Exciter and see if you have enough amp'ing going with the ultra micro stack.

post #7 of 8
Quote:
Originally Posted by plonter View Post
anyway,just listening to the M50 out of the earmax and it sounds fine to me,can't notice anything suspicious that points on underamping,    what exactly are the sings of underamped headphones?  is it distortion of some kind...maybe the need to turn the volume pot all the way up to reach a normal volume level?

I don't think it's so easy to find out what exactly could be wrong without doing some measurements.

I'm sure the min. requirements were chosen with some headroom in mind. (it looks like that amp also has 35 ohm resistors in series with the hp jack, for protection)

 

Quote:
Originally Posted by TheWuss View Post

some other folks may be able to help more.

but, my general impression of underamped phone (i tried my 600 ohm dt990 out of an ipod just to be able to say for sure what "it" is) is that the sound will be flat, boring, not loud enough, and may even distort when certain big transients hit.

"flat, boring" is more likely a problem with mismatched output impedance. (see below)
Low gain and/or limited output can be the reason for "not loud enough".

However if you can really hear distortion with increasing volume, then it's pretty clear that the amp cannot handle the load.
 

 

Quote:
Originally Posted by aimlink View Post

For me it hasn't been an issue of sheer volume.  I've heard headphones with a lot of volume and yet they aren't well amp'd.  The first thing to suffer is usually the bass.

 

The Ed8's for example have a boomy bass and perhaps even more voluminous, when unamp'd.  Once, amp'd, the bass tightens up and becomes more controlled and less intrusive.  This is an even more marked phenomenon with the D5000's.  

 

With the HD650/600's, there's a loss of dynamism and energy in the sound.

 

In the end, I don't think you can tell a can is underamp'd unless you've heard them well amp'd. 

I have reason to believe that mismatched output impedance (Zout) commonly is misunderstood as "underamped" or "unamped" (stupid, misleading word imho).

 

Take the HD555 and plug it into the jack of a receiver with >120 ohm Zout and you'll be shocked by the amount and flabbiness of bass.

Plug the same 'phone into an amp with < 1 ohm and the huge amount of bass will disappear and mids will start to dominate.

 

The scale of such FR variations depends on the nominal impedance and impedance curve of the headphones, and can range from non-existent to huge.

 

This would also explain why the bass is "even more voluminous, when unamp'd".

"loss of dynamism and energy" is too vague for me to comment on.

 

 

If you wanted to do a listening test between the amp in question and another, probably more suitable, amp I'd suggest to match the output impedance just like volume.


Edited by xnor - 5/8/10 at 6:10pm
post #8 of 8

The fastest way to do it is listen on gear above your price range with the same output impedance, and see how your gear compares. If its comparable, chances are you're not doing too badly.

 

If its radically different, you're way off.

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