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"Not-enough-to-drive the heaphones", how is it defined?

Budgeter

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In this thread, I want to focus mainly on the aspect of power output. I'm not certain if other aspects like frequency, distortion, etc. affects the power output. To be clear, I'm not an expert in electrical/audio engineering by any means.

When looking a new amplifier, it is easy to find people asking this question: "Does this amplifier have enough power to drive [name of the headphones]?" However, I wonder in what scenarios can we definitely say an amplifier is not enough for XXX headphones. Many people just go to other options when an amplifier is said to be "not-enough power" for their headphones.

Currently, I'm owning JDS Labs Atom (no-plus, driven by Topping D10) and Fiio E10k. Atom amp maximum output is 250mW @300 ohms (https://www.audiosciencereview.com/...ents-of-new-jds-labs-atom-headphone-amp.5262/), while E10k is 200mW @ 32 ohms (Fiio spec, this model was not fully measured on our forum). Undoubtedly, unlike E10k, the Atom amp is a power house here. Fiio also recommends E10k for only 16~150 ohms.

My use case is 99% YouTube, 1% Spotify (all free-tier). One of my headphones is DT990 Edition 600 ohms, definitely not very sensitive though as it is certainly more demanding than a 250 ohms Pro variants (https://www.audiosciencereview.com/...eyerdynamic-dt990-pro-review-headphone.19975/).

I don't apply any EQ, and both volume are @100 in Windows/Linux (Analog/SPDIF out), low gain for both, no bass boost on E10k. Use the video below as a reference, on Atom amp, around 10'o clock is enough for me, while Fiio E10k is around level 1 to 2 (out of 8). Beyond that, they're ear bleeding. In fact, I use the same volume configuration for all of my tasks (video conference, music, game, etc.) With that said, It seems like "Not-enough-to drive" is not applicable in my use case. Unfortunately, I don't have a reliable SPL meter to measure the output.

So, when can we say a specific amplifier is not enough for the headphones? If we're going to extend the discussion, will this also apply to speakers? Is the power output irrelevant after a certain threshold?

 

JWAmerica

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It really depends on your preferred listening volume level, how much EQ you apply, etc to determine how much power you need. According to some reviews you'll want at least 1 Vrms, though that's cutting it pretty close on 600ohm headphones. I'd be looking for 2 Vrms into high impedance headphones.

But if they get loud enough for you with the E10k and you're not close to max output on the amp, what's the problem?
 
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It really depends on your preferred listening volume level, how much EQ you apply, etc to determine how much power you need. According to some reviews you'll want at least 1 Vrms, though that's cutting it pretty close on 600ohm headphones. I'd be looking for 2 Vrms into high impedance headphones.

But if they get loud enough for you with the E10k and you're not close to max output on the amp, what's the problem?
There is no problem. They're surely enough for me. I'm just curious why people make such claims that an amplifier is not enough for the headphones.
 
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The answer is easy.
When the sound quality deteriorates when playing louder.
I thought about that too. I did not clearly show it in my post but you can somewhat see it via my question.
Is the power output irrelevant after a certain threshold?

The thing is, do we even need to play that loud? I assume there are low-volume mastered recordings out there, but it's hard to imagine there is one that requires me to use all power of the Atom amp.
If most of the content can be loud enough (average 60-70 dB) at 10mW of output (10% of the amp), then 100mW (100%) is irrelevant, is it? There can be a peak volume in a track (90 dB for 1 ms), but it's minimal and irrelevant (at least to me). Note, these are just imaginary figures to elaborate my points.
 

solderdude

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Powerful amps can be used on inefficient and efficient headphones.
A very inefficient one may well have to deliver 0.5W or even more yet other folks may not need more than a few mW.

So... when sound turns nasty (and you want to go louder) there isn't enough power. It may not be your situation.
 

3125b

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(Fiio spec, this model was not fully measured on our forum)
The 200mW @32Ohm spec is accurate. I have measured the FiiO E10K ... unfortunately I haven't really documented my results all that well.
Output impedance is 1 Ohm, maximum output voltage is 2.55Vrms. 50mV SINAD is 84dB ... the rest I forgot. But it's not a bad little device.

As a general rule of thumb: Twice the subjective volume requires ten times the power.
When looking at buying a new amp, my target would be that it can achieve 120dBSPL with any of my current of future headphones (if possible save a few outliers). That should ensure enough headroom even when using EQ and listening to quiet content.
 

tomtoo

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I thought about that too. I did not clearly show it in my post but you can somewhat see it via my question.


The thing is, do we even need to play that loud? I assume there are low-volume mastered recordings out there, but it's hard to imagine there is one that requires me to use all power of the Atom amp.
If most of the content can be loud enough (average 60-70 dB) at 10mW of output (10% of the amp), then 100mW (100%) is irrelevant, is it? There can be a peak volume in a track (90 dB for 1 ms), but it's minimal and irrelevant (at least to me). Note, these are just imaginary figures to elaborate my points.

Do you need it? Is a good question.
Some need, some not. Some enjoy for short durations going loud other not.
 

DVDdoug

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...then 100mW (100%) is irrelevant, is it?
"mW" are tricky with headphones because headphone impedance varies so much.

The headphone amp puts-out a voltage and Wattage is Voltage squared/Impedance. So, you're getting 10 times the power with 60-Ohms as as compared to a 600-Ohm headphone. That holds until you have a low-impedance headphone and the amplifier can't put-out enough current, and then the voltage drops. (Power can also be calculated as Voltage x Current.)

With speakers it's less of an issue because most speakers are 4 or 8-Ohms and there is often an amplifier rating for both.
 
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Powerful amps can be used on inefficient and efficient headphones.
A very inefficient one may well have to deliver 0.5W or even more yet other folks may not need more than a few mW.

So... when sound turns nasty (and you want to go louder) there isn't enough power. It may not be your situation.
Based on your measurement on the DTxx0 line, I think you had quite a few experience with it. Can you suggest me a specific scenario where DT 990 Edition 600 ohms needs to be driven at its limit (100mW input) in order to have a good listening experience?
I've heard people saying there are headphones out there which requires wattage of input, but in which scenarios though?


The 200mW @32Ohm spec is accurate. I have measured the FiiO E10K ... unfortunately I haven't really documented my results all that well.
Output impedance is 1 Ohm, maximum output voltage is 2.55Vrms. 50mV SINAD is 84dB ... the rest I forgot. But it's not a bad little device.

As a general rule of thumb: Twice the subjective volume requires ten times the power.
When looking at buying a new amp, my target would be that it can achieve 120dBSPL with any of my current of future headphones (if possible save a few outliers). That should ensure enough headroom even when using EQ and listening to quiet content.
May I ask the reasons you demand 120dBSPL? I mean, that's the level of instant hearing loss even with insensitive-to-ear frequency like sub-bass IIRC, not to mention upper frequency range.
Definitely, one can says it gives more headroom, but does that amount of headroom really matters? Or is it like SINAD, where we're simply chasing better measurement gears with any hear-able effects?
 

solderdude

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Can you suggest me a specific scenario where DT 990 Edition 600 ohms needs to be driven at its limit (100mW input) in order to have a good listening experience?

High dynamic music in studio monitoring situations. That may very well be not your case.

Then there is the issue of owning several headphones of varying impedance (requires higher voltage, lower current) and low impedance headphones which requires higher currents but lower voltage.
When you want an amp that can drive both to loud levels without distortion you need an amp that can provide:
A: enough gain (high imp. headphones)
B: have low noise (higher SINAD and low gain)
C: can provide a high voltage and a high current = high power

Now here comes the kicker... this doesn't have to cost much.
Well... maybe with some very rare headphones you need something VERY beefy.
So.... what would be the reason NOT to have such an amp other than owning only some high efficiency IEMs and a phone ?

May I ask the reasons you demand 120dBSPL?

Nobody demands anything. Situations may demand it.
120dB SPL in low bass is NOT inducing instant hearing loss. Amir did a video about it.
When one wants to cover ALL situations and wants to be insured the amp never clips (so have some headroom left) then reaching 120dB SPL peak is what one needs.
When one only wants to listen to compressed popular recordings at sensible levels 90dB SPL peak is probably enough.
 
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charleski

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on Atom amp, around 10'o clock is enough for me, while Fiio E10k is around level 1 to 2 (out of 8)
Just a note: the position of the volume knob only tells you how far the amp is from its maximum voltage gain, it’s not a direct indicator of power output. If you have an unbalanced (RCA) source that outputs 2Vrms it’s almost certain the amp will go into clipping well before the volume is at max, this is so there’s extra gain available for low-output sources. The only way to test if the amp is clipping is to measure the distortion.
 

JanesJr1

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The answer is easy.
When the sound quality deteriorates when playing louder.
Solderdude's answer may seem flippant, but it's kind of true. I came back to audio after more than 2 decades away from it, and mobile music and digital were all new to me. I started with Dragonfly portable DAC/AMP's (dongles) and found they utterly crumpled, sometimes into what sounded like outright clipping with HD6XX phones (like the HD650's), although it varied by recording. Nothing marginal about it. Then I moved up to a Hidisz S8 which worked great with Etymotic IEM's, and I thought they were ok with my HD6XX's ... until I also had JDS Atom Amp + DAC on my desktop, where the much greater power made the HD6XX bottom end a lot more powerful on the test tracks I knew the best. So I use the S8 where it is perfect for the Ety's and mobile listening, but stick to the JDS for my 300-ohm headphones on my desktop. And I ditched the Dragonfly dongles. There's a lot of mythology in audio, but the need for power is not one of them (at least when there's not quite enough).

You may never have a problem. My mistake was naively matching very low power Dragonfly dongles to high-impedence headphones, a bad marriage of extremes. My only point is that the effect of power can be very audible, and you can learn to hear it. If I had joined this forum sooner, I could've avoided the problem with all the info that's here.
 
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