[Aegruin]

Hi,
 
I know about basic technical stuff like mWs and Ohms that comes from amps, Volts that comes from DACs and their relationship with the Headphones and IEMs. The thing I don't understand is sometimes people speak about "Output Impedance of Amps".
I mean, yes I know about the output impedance. They are generally like 0.75-1Ohm but people speak of 10Ohm 20Ohm or 100Ohms. It should be a different thing. I couldn't find any resources about this subject. I would appreciate any help. Thank you! 

 

[MindsMirror]

Amps have an output impedance, measured in Ohms, which could be 0.75 Ohms, 100 Ohms, more, less, or anywhere in between. Low output impedance is better so you typically see values that are lower, like 0.75 to 1.0 Ohms as you said.
 
Amps also have a power output, measured in Watts.You might typically see an amp spec which says something like "250mW at 32 Ohms." The 32 Ohms is referring to the impedance of the load, meaning the headphone. If you plug a 32 Ohm headphone in, the amp will be able to deliver 250mW of power.
 
The amp's output impedance, and the load impedance are both measured in Ohms, but they are not the same thing and are not related to each other.

 

[Aegruin]

  Amps have an output impedance, measured in Ohms, which could be 0.75 Ohms, 100 Ohms, more, less, or anywhere in between. Low output impedance is better so you typically see values that are lower, like 0.75 to 1.0 Ohms as you said.
 
Amps also have a power output, measured in Watts.You might typically see an amp spec which says something like "250mW at 32 Ohms." The 32 Ohms is referring to the impedance of the load, meaning the headphone. If you plug a 32 Ohm headphone in, the amp will be able to deliver 250mW of power.
 
The amp's output impedance, and the load impedance are both measured in Ohms, but they are not the same thing and are not related to each other.

Thank you for the answer. 
 
The thing is, I realized that my iDSD Micro gives 250mW at 16Ohm on ECO Mode and 1.000mW at 16Ohms on Normal Mode. When I use JH Rosie, ECO Mode feels more congested and V-shaped. But, when I switch to the Normal mode its soundstage becomes huge, never gets congested and the tune feels more natural ...but isn't 1.000mW seems overkill? This is the thing I'm trying to understand. 

 

[MindsMirror]

Power alone should not change anything about the sound other than the maximum volume it can reach. Switching from eco to normal should make it louder, so you need to carefully adjust the volume so they are both the same in order to make a proper comparison. Your DAC/amp does have some EQ options, perhaps those are automatically changing when you switch modes.

 

[ProtegeManiac]

 
The thing is, I realized that my iDSD Micro gives 250mW at 16Ohm on ECO Mode and 1.000mW at 16Ohms on Normal Mode. When I use JH Rosie, ECO Mode feels more congested and V-shaped. But, when I switch to the Normal mode its soundstage becomes huge, never gets congested and the tune feels more natural ...but isn't 1.000mW seems overkill? This is the thing I'm trying to understand. 

 
Either the output impedance changes like how some amps have different output impedance depending on gain mode, or Eco Mode is a lot like Quiet Mode in other receivers, ie they deliberately boost the treble and bass so you can listen at lower levels but you can still hear either end rather than have the midrange dominating.

 

[Ancipital]

  Thank you for the answer. 
 
The thing is, I realized that my iDSD Micro gives 250mW at 16Ohm on ECO Mode and 1.000mW at 16Ohms on Normal Mode. When I use JH Rosie, ECO Mode feels more congested and V-shaped. But, when I switch to the Normal mode its soundstage becomes huge, never gets congested and the tune feels more natural ...but isn't 1.000mW seems overkill? This is the thing I'm trying to understand. 

A lot of headphones don't have a linear impedance- at different frequencies, they have "bumps". For example (I always use this darn example!), my HD650 have a nominal impedance of 300 Ohms, but a 530ish Ohm spike around 100Hz or so. If I underpower them, they sound insipid in the bass, even on an amp that can make a lot of volume (because the impedance is the issue, rather than the sensitivity). It's possible that you're hearing something similar.

 

[HiFiChris]

@Aegruin
 
The micro iDSD has about 0.2 Ohms without enabled iEMatch, ca. 4-5 Ohms in iEMatch "High Sensitivity" mode and about 1.4 Ohms output impedance when set to iEMatch "Ultra Sensitivity".
 
So you should either use no iEMatch or the stronger iEMatch mode in order to get the truest sound.
 
 
But in addition, the volume difference is of course also responsible for the perceived differences (-> see "equal-loudness contour").

 

[Aegruin]

Thank you for all the answers! 

 
 
 

  @Aegruin
 
The micro iDSD has about 0.2 Ohms without enabled iEMatch, ca. 4-5 Ohms in iEMatch "High Sensitivity" mode and about 1.4 Ohms output impedance when set to iEMatch "Ultra Sensitivity".
 
So you should either use no iEMatch or the stronger iEMatch mode in order to get the truest sound.
 
 
But in addition, the volume difference is of course also responsible for the perceived differences (-> see "equal-loudness contour").

 
I found "Normal Mode / High Sensitivity" the best among the combinations but I really don't know 1000mw does any harm or is it wrong in some kind of way. I'm looking at DAPs that gives 100mw at 16Ohm, amps that gives 250mw at 16Ohm and this thing seems overkill and wrong. (but it still sounds the best. very obviously.)
 
 

  A lot of headphones don't have a linear impedance- at different frequencies, they have "bumps". For example (I always use this darn example!), my HD650 have a nominal impedance of 300 Ohms, but a 530ish Ohm spike around 100Hz or so. If I underpower them, they sound insipid in the bass, even on an amp that can make a lot of volume (because the impedance is the issue, rather than the sensitivity). It's possible that you're hearing something similar.

 
Yes, I was aware of that situation. On innerfidelity, Tyll specially explains Multi-driver IEMs having very wavy impedance responses ...but like I said, 1000mw? Isn't that harmful or something to an IEM? 

 
 

   
Either the output impedance changes like how some amps have different output impedance depending on gain mode, or Eco Mode is a lot like Quiet Mode in other receivers, ie they deliberately boost the treble and bass so you can listen at lower levels but you can still hear either end rather than have the midrange dominating.

  Power alone should not change anything about the sound other than the maximum volume it can reach. Switching from eco to normal should make it louder, so you need to carefully adjust the volume so they are both the same in order to make a proper comparison. Your DAC/amp does have some EQ options, perhaps those are automatically changing when you switch modes.

 
I don't think this is the situation.

 I don't have multiple high-end headphones or IEMs to try this, but with KC06 or VSD3S I don't have this sound 'transformation' and I'm talking about the differences on the same volume, not louder.

 

[MindsMirror]

You won't harm your headphones at all by using a 1000mW amp as long as you restrict the volume to a reasonable level. A 1000mW amp and a 100mW amp will actually deliver the same amount of power as each other if you set them each to be the same loudness. The difference is that the 1000mW amp is capable of going louder, the 100mW would max out at a lower volume.

 

[Me x3]

  A lot of headphones don't have a linear impedance- at different frequencies, they have "bumps". For example (I always use this darn example!), my HD650 have a nominal impedance of 300 Ohms, but a 530ish Ohm spike around 100Hz or so. If I underpower them, they sound insipid in the bass, even on an amp that can make a lot of volume (because the impedance is the issue, rather than the sensitivity). It's possible that you're hearing something similar.

This is not correct.
You need to understand that the amplifier provides certain voltage (rms) at the headphone's plug.
Drive the headphone with a constant voltage (rms) across the audible spectrum and you'll get the headphone's frequency response.
The Sennheiser HD650 doesn't need more voltage at 100Hz it needs similar voltage as the rest of the spectrum.
What's important here is that as the impedance raises, the headphone, as a load, drains less current, and this means, the headphone is easier to drive in the mid-bass region where the impedance is higher. This point where the impedance is highest is known as the fundamental resonance of the driver, that's the point where the driver is most efficient (ie, easier to drive).
 
In simpler words, what you've wrote comes from the general misconception: higher impedance = harder to drive
In fact it's the other way around, as the impedance of the headphone raises, it needs less power to work properly.

 

[Monsterzero]

 
This is not correct.
You need to understand that the amplifier provides certain voltage (rms) at the headphone's plug.
Drive the headphone with a constant voltage (rms) across the audible spectrum and you'll get the headphone's frequency response.
The Sennheiser HD650 doesn't need more voltage at 100Hz it needs similar voltage as the rest of the spectrum.
What's important here is that as the impedance raises, the headphone, as a load, drains less current, and this means, the headphone is easier to drive in the mid-bass region where the impedance is higher. This point where the impedance is highest is known as the fundamental resonance of the driver, that's the point where the driver is most efficient (ie, easier to drive).
 
In simpler words, what you've wrote comes from the general misconception: higher impedance = harder to drive
In fact it's the other way around, as the impedance of the headphone raises, it needs less power to work properly.

Im not an expert on this topic and im not posting to argue,rather to learn,so bear with me....

If this is true than why do headphones,such as the AKG K340 @600 ohms is a b***h to drive?

 

[HiFiChris]

Sensitivity is what's mainly important.

 

[Monsterzero]

Sensitivity is what's mainly important.

So a 600 ohm headphone w/ a 98 sensitivity is easier to drive than a 32 ohm headphone with the same sensitivity?

 

[ProtegeManiac]

Quote:

Originally Posted by Aegruin /img/forum/go_quote.gif

I don't think this is the situation.

 I don't have multiple high-end headphones or IEMs to try this, but with KC06 or VSD3S I don't have this sound 'transformation' and I'm talking about the differences on the same volume, not louder.

 

If the Eco Mode applies an EQ like on HT receivers' Quiet Mode, then it doesn't matter if you're listening at the same effective output level - the DSP will apply that EQ as long as you have it on EcoMode (if that's what it does anyway) and not on normal mode, regardless of whether you have both playing with the IEM at the same effective output level in dB's. You don't crank it up either way either because you don't have to given the sensitivity.

 

[HiFiChris]

Sensitivity is what's mainly important.

So a 600 ohm headphone w/ a 98 sensitivity is easier to drive than a 32 ohm headphone with the same sensitivity?

The German Shure blog posted a really good article about that, however it is obviously in German. Unfortunately they didn't translate it for the English/international Shure blog. Here's the link anyway: https://shuredeutschland.wordpress.com/2012/08/16/kopfhoerer-impedanz/

I don't think this is the situation.  I don't have multiple high-end headphones or IEMs to try this, but with KC06 or VSD3S I don't have this sound 'transformation' and I'm talking about the differences on the same volume, not louder.

If the Eco Mode applies an EQ like on HT receivers' Quiet Mode, then it doesn't matter if you're listening at the same effective output level - the DSP will apply that EQ as long as you have it on EcoMode (if that's what it does anyway) and not on normal mode, regardless of whether you have both playing with the IEM at the same effective output level in dB's. You don't crank it up either way either because you don't have to given the sensitivity.

The micro iDSD doesn't apply any DSP/EQ in Eco Mode/iEMatch mode.