Head-Fi.org › Forums › Equipment Forums › Headphone Amps (full-size) › are High Watts Output Amps really necessary?
New Posts  All Forums:Forum Nav:

are High Watts Output Amps really necessary?

post #1 of 17
Thread Starter 

Amps Comparison

Burson Soloist 4W output

Burson HA-160 0.25W output

 

as far as i know the highest impedance on a headphone is 600ohm

 

both the Burson amp could drive the 600ohm headphone perfectly loud, isnt the Burson Soloist (4W) bit of an overkill?

 

with another example, the LCD-2 Impedance of 60ohm, wouldnt  any amp able to drive that? what is the difference when using the Soloist and HA-160 on the LCD-2? (lets just leave the DAC out of this)

 

(btw my laptop runs HD650 300ohm perfectly loud without an amp,i dont see the point of buying an amp if i purchase the LCD-2 60ohm)

post #2 of 17

The output of an amp is dependent on the impedance of the load.

So for example, an OTL (output transformer-les) tube amp will typically put out less voltage at low impedance and higher voltage at higher impedance's.

and an output transformer coupled tube amp is generally the opposite.

 

Tube amps in general(most but not all?) have a hard time achieving an output impedance of really low.  Solid state does a better job of this.

 

So now were heading towards damping factor.  which is the impedance of the load(headphones) divided by the output impedance of the amp.

in general you want this number to be as high as possible.  (however there reaches a point where it can be to high, or so i've read)

However, with non dynamic driver headphones this is less important.

So the LCD2 isn't as dependent on the damping factor.

 

kinda got lost there in my thoughts.  sorry

 

but my HD 650's will get fairly loud on my iPad, but sound nowhere near as good as they do out of my vintage Kenwood receiver or my WA2.

that's not to say they sound bad out of the iPad, but there's a very noticeable difference in the sound. dynamics, fine details, sound stage and so on.

 

this is all of course just my experience and some of what i've gathered (and remember) from researching similar issues.

YMMV

 

Hopefully some one with more expertise than I will chime in to help

 

 

oh yeah,

and with the Planar magnetics and other Orthos the impedance can be misleading.  They can require much more voltage than the impedance implies.  and really, impedance in general can be misleading.  Most of the times the lower the z the easier to drive but this isn't always true.  its a good idea to look at the sensitivity as well.  and if you can find measurments by Tyll at Innerfidelity he has a nice section at the bottom of his measurments sheat that shows a helpful spl and voltage


Edited by Rawrbington - 11/11/12 at 6:19pm
post #3 of 17

Some headphones have higher than 600 ohms.

 

Loudness is determined by output level, headphone impedance, and headphone sensitivity—usually given as a figure like 95 dB SPL / 1 mW power input.  For sensitivity, some headphones go below 90 dB SPL / 1 mW, while some IEMs are more like 120 dB SPL / 1 mW.  This is a huge span, so focusing on impedance alone is ignoring a very important factor.  Some 600 ohms headphones are less sensitive than the Beyerdynamics or whatever you may be thinking about.  Because of the low sensitivity, the ~50 ohms HE-6 needs a higher voltage than 600 ohms Beyerdynamics to reach equivalent loudness.  Because of the low impedance and P = V^2 / Z (power equals voltage squared divided by impedance), that means the HE-6 needs a whole lot more power than those Beyerdynamics, for example.  Higher-impedance headphones are easier to drive in general , except that they need a higher voltage equivalent power levels (again, see P = V^2 / Z).  Amplifiers will usually have more problems with lower-impedance headphones, because more current is required and because of potential output impedance issues.

 

Non-idealities in amplifiers (intended by the designer or not) mean that there is some difference in signal produced between different amplifiers, particularly at different operating conditions, so sound quality can be affected.  Most people will point to different amps sounding different, and this is the big draw behind having different amplifiers—though maybe in reality, differences are less than people think.  In controlled listening environments, fair comparisons, comparisons with different amps under bedsheets, the ability for people to correctly identify different amps is diminished (though not to zero of course, for certain combinations)...

 

Some amps look nice; some people like having volume knobs to turn.  There are reasons other than sound quality to get an amp, though most people try to talk about sound quality.

 

 

A common situation these days is to have people using but a fraction of the output power of an amplifier (e.g. 10 mW out of a possible 500 mW @ 50 ohms), and they say they don't like the sound they get from their headphones.  Particularly for planar magnetics, the common response seems to be to get a different, even more powerful amplifier (e.g. capable of 2000 mW @ 50 ohms), with the claim that you need more power.  That's bullocks.  You can try something different, but unless you're running your current amp out of its comfort zone, the sound is not a result of lack of power.  It's more likely that someone just doesn't like a certain headphone's sound, which is a-ok.  There are other headphones out in the world.

 

So to answer the question in the title, higher output power is needed if you want to listen louder.  Headphone sensitivity and impedance determine how loud they will play for a given setting on an amplifier.  If you max an amp out and want more volume, or if the amp is distorting at higher levels, you want more power.  Otherwise, no.

 

In my opinion, the race for high output power headphone amps is mostly a marketing sham.  People generally are not using the extra power.  It is very convenient for amp manufacturers that there is a lack of understanding among consumers about what electric power means.  An amp capable of higher output power may or may not sound subjectively more "powerful", with more "authority", and so on with the buzzwords.


Edited by mikeaj - 11/11/12 at 6:33pm
post #4 of 17
Thread Starter 

yes thanks for replying.

 

so let me simplify what u are saying, please correct me if im wrong

 

the output of the amp is dependent on the impedance of the load, that means the amp will automatically adjust how much "volt / current" will go into different headphone with different impedance

tube amps has trouble adjusting volt/current into low impedance headphones <32ohm and solid state does a better job all rounder 0-600ohm

 

with dynamic headphones we calculate damping factors, the outcome of the calculation needs to be as high as possible so its better, ipod drives hd650 loud but the damping factor calculation is low which results in low SQ

 

but with planar magnetics and orthos headphone it is a whole different calculation, they still require good amp to drive regardless of how small the impedance is <100ohm.

post #5 of 17

i kind of picture damping factor as grip and control on the driver

the higher the damping the tighter the grip and the better the control of the driver.

Theoretically you can have too tight a grip, however i have not run into this issue yet.

a low damping factor usually results in looser boomy bass.  and sometimes, distortion across the spectrum.  but it doesn't always sound bad.

post #6 of 17

Most amps are voltage sources, or more or less ideal voltage sources (up to the clipping point, though with some nonlinearities) with some source output impedance.

 

1000

 

The volume knob, gain setting, DAC output level, sound data (music file) determine V_s.  You can see that for low-impedance headphones (lower Z_L), particularly if the impedance is different at different frequencies, the source output impedance matters more.  Damping factor for headphones is generally not really a big deal except when impedance vs. frequency is wild, because then the voltage the headphones sees is a function of frequency.  Past 10 or so is already a lot, negligible benefits after that.  In theory, you might want slightly more for some IEMs with those crossovers.  For most headphones, much less may be okay.

post #7 of 17
Quote:
Originally Posted by mikeaj View Post

 

So to answer the question in the title, higher output power is needed if you want to listen louder.  Headphone sensitivity and impedance determine how loud they will play for a given setting on an amplifier.  If you max an amp out and want more volume, or if the amp is distorting at higher levels, you want more power.  Otherwise, no.

 

In my opinion, the race for high output power headphone amps is mostly a marketing sham.  People generally are not using the extra power.  It is very convenient for amp manufacturers that there is a lack of understanding among consumers about what electric power means.  An amp capable of higher output power may or may not sound subjectively more "powerful", with more "authority", and so on with the buzzwords.

 

Exactly.  Simply put, the amp supplies voltage, the headphone draws the current it needs from the amp at this voltage, the function of voltage and current is the power being supplied to the headphone. The sensitivity of the headphone determines how much of this power gets converted to sound.

 

The important thing is that the amp should not be limited by the voltage or current needed by the headphone to run at usable volume.

Hence, power alone is no good as a figure, you need to know power @ what impedance.

For instance, if an amp cannot supply enough amps for my headphone with 10 Ohm impedance, its no use what little amps it can supply at a higher voltage for a higher impedance headphone. Its' no good for my use.


Edited by proton007 - 11/11/12 at 6:55pm
post #8 of 17
Thread Starter 
Quote:
Originally Posted by mikeaj View Post

 

1000

 

burson's soloist specification page http://bursonaudio.com/Burson_Soloist.html

Burson Soloist: Output impedance: <1 Ohm @ 30 Ohm, 1W

therefore 300/30= 10 ??(not sure if im right)

 

lets say hd650 with 300 impedance when using

 

 

Damping factor = 300/10

=30 ?? 

 

please correct me

post #9 of 17
Quote:
Originally Posted by Couch Potato View Post

 

burson's soloist specification page http://bursonaudio.com/Burson_Soloist.html

Burson Soloist: Output impedance: <1 Ohm @ 30 Ohm, 1W

therefore 300/30= 10 ??(not sure if im right)

 

lets say hd650 with 300 impedance when using

 

 

Damping factor = 300/10

=30 ?? 

 

please correct me


I think the output impedance as measured by Burson is at 30 ohms load, 1W power.  So I guess the damping factor should be > 30 at any rate.


Edited by proton007 - 11/11/12 at 7:28pm
post #10 of 17
Quote:
Originally Posted by Couch Potato View Post

 

burson's soloist specification page http://bursonaudio.com/Burson_Soloist.html

Burson Soloist: Output impedance: <1 Ohm @ 30 Ohm, 1W

therefore 300/30= 10 ??(not sure if im right)

 

lets say hd650 with 300 impedance when using

 

 

Damping factor = 300/10

=30 ?? 

 

please correct me

 

NP. The output impedance IS <1 Ohm regardless (It may change with frequency but let's keep it simple). With 300 Ohm cans the damping factor is >300.

 

The speaker amp I use has an output impedance of 0.005 Ohm and that gives it a damping factor of 1200 with my 6 Ohm speakers. It has an iron grip on the bass. wink.gif

post #11 of 17
Most headphones only need approx. 1-10 mWatts to produce a reasonable volume.
so for most headphones, 1 Watt or 4 Watts is overkill.

BTW, I have a pair of 2,000 Ohm 'phones, they work fine out of any headphone amp I have that can put out a few Volts, so my little portables like my iBasso do not output enough voltage for the 2,000 Ohm 'phones.
post #12 of 17
Quote:
Originally Posted by Hooster View Post

NP. The output impedance IS <1 Ohm regardless (It may change with frequency but let's keep it simple). With 300 Ohm cans the damping factor is >300.

The speaker amp I use has an output impedance of 0.005 Ohm and that gives it a damping factor of 1200 with my 6 Ohm speakers. It has an iron grip on the bass. wink.gif

Don't forget the impedance of your speaker cables, the impedance of any inductors in the crossover and the contact resistance at any contacts you have between amp and speaker will add up to significantly reduce your damping factor.
post #13 of 17
Quote:
Originally Posted by Couch Potato View Post

burson's soloist specification page http://bursonaudio.com/Burson_Soloist.html
Burson Soloist: Output impedance: <1 Ohm @ 30 Ohm, 1W

therefore 300/30= 10 ??(not sure if im right)

lets say hd650 with 300 impedance when using


Damping factor = 300/10
=30 ?? 

please correct me

300/1 = 300
post #14 of 17
Quote:
Originally Posted by proton007 View Post

Exactly.  Simply put, the amp supplies voltage, the headphone draws the current it needs from the amp at this voltage, the function of voltage and current is the power being supplied to the headphone. The sensitivity of the headphone determines how much of this power gets converted to sound.

The important thing is that the amp should not be limited by the voltage or current needed by the headphone to run at usable volume.
Hence, power alone is no good as a figure, you need to know power @ what impedance.
For instance, if an amp cannot supply enough amps for my headphone with 10 Ohm impedance, its no use what little amps it can supply at a higher voltage for a higher impedance headphone. Its' no good for my use.

sensitivity refers to how much voltage is required to produce a specific sound pressure level.

i.e. 1 Volt = 105 dB SPL

efficiency is how conversion of electrical power into sound pressure level is specified, i.e. 1 mWatt = 96 dB SPL
post #15 of 17

Thx Chris. The impedance of any decent speaker cable is minimal compared to the impedance of a speaker

http://en.wikipedia.org/wiki/Speaker_wire

 

The impedance associated with the crossover is included in a speakers impedance rating and the contacts should not generate significant impedance. With most speakers, significant variations in impedance do however occur with frequency. A speakers impedance rating is nominal and does not account for that fact that the impedance can vary rather wildly with frequency. It can dip very low at low frequency and this may cause problems, typically bloated bass or clipping if you push harder, if your amp is not capable of producing enough current.

 

http://forum.blu-ray.com/showthread.php?t=71469

http://en.wikipedia.org/wiki/Electrical_characteristics_of_dynamic_loudspeakers

New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Headphone Amps (full-size)
Head-Fi.org › Forums › Equipment Forums › Headphone Amps (full-size) › are High Watts Output Amps really necessary?