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How do I know when an amplifier is too powerful for my headphones?

post #1 of 15
Thread Starter 

I've been told that getting a Schiit Ragnorak or an Audio-GD Master 9 might melt my headphones.  I was also told that it was more the current that would melt headphones and not the wattage.  Now my electrical knowledge is pretty rusty and to be honest it was never that great to begin with.  I remember lots of people pairing my same headphones with the Soloist which puts out 4000mW @16ohms, which is much higher than the maximum input of my headphones and none of them reported any problems yet the SE output of the Master 9 is 2500mW @40ohm.  This leads me to thinking that the gentleman who told me about worrying about the current is correct but again I'm not expert or anywhere close to that on this subject.  I figured some of you could pass along some wisdom/knowledge to me.  I'm also curious if there's a formula or a general rule of thumb that I can go by so that I can better calculate this?

 

Here are the specifications for my headphones and I only plan to connect them via singled-end connection (6.3mm jack), Fostex TH-900:

 

Impedance: 25 ohm
Sensitivity: 100dB / mW
Maximum Input: 1,800 mW

 

 

These are the amps I'm considering:

 

 

Schiit Ragnorak (These are Preliminary Specs):

Power Output: 100W into 4 ohms, 60W into 8 ohms, 15W into 32 ohms, 9.6W into 50 ohms, 1.6W into 300 ohms, 800mW into 600 ohms
Inputs: 2 balanced, 3 single-ended stereo inputs
Outputs: speaker terminals, 4-pin balanced XLR headphone, TRS unbalanced headphone, balanced and unbalanced preamp outs
Gain: selectable gain of 20, 7, or 1
Volume: (64) 1.25dB steps via relay-switched stepped attenuator
Topology: Fully discrete Crossfet™ circlotron-style stage with no caps in the signal path and no DC servos, all solid state
Management: microprocessor control of quiescent current and DC levels, with monitoring of all fault conditions
Power Supply: 400VA transformer with 4 separate circlotron output rails, over 100,000uF filter capacitance total
 
AURAlic Taurus mk2 (let me know if more info is needed for these):
Power Output: 4,500mW into 32 ohm loads (single ended mode)
 
Audio-GD Master 9:
S/N Ratio
 
>130DB (Input short, XLR mode)

THD
 
<0.002 %


Gain
 

Low Gain : +14 DB (XLR)
High Gain : +20DB (XLR)

Headphone amp Output Power
(Single-ended , Pure Class A )

40 ohm: 2500MW
100 ohm: 1050MW
300 ohm: 350MW
600 ohm: 175MW

Output impedance

1 ohm

 

*Updated*

Thank you in advance for any guidance you can give me and I greatly appreciate your time in this matter.

post #2 of 15

Chances are you'll never have a problem with an amp that is too powerful "melting" your headphones, since you would have to turn it up to deafeningly loud levels to do so (just because an amp can output 3000mW doesn't mean it is always outputting 3000mW). Instead, the problems you'll have with a too-powerful amp are likely that the noise floor will be audible with sensitive headphones, and if it uses an analogue volume pot, you may have channel imbalance issues at the extremely low volume setting needed for most headphones. Aside from that, there's no problem with it (though either of those is enormous overkill for your headphones - you could drive them perfectly well and extremely loudly for less than a tenth the cost of any of those devices you're looking at)

post #3 of 15
Thread Starter 
Quote:
Originally Posted by cjl View Post
 

Chances are you'll never have a problem with an amp that is too powerful "melting" your headphones, since you would have to turn it up to deafeningly loud levels to do so (just because an amp can output 3000mW doesn't mean it is always outputting 3000mW). Instead, the problems you'll have with a too-powerful amp are likely that the noise floor will be audible with sensitive headphones, and if it uses an analogue volume pot, you may have channel imbalance issues at the extremely low volume setting needed for most headphones. Aside from that, there's no problem with it (though either of those is enormous overkill for your headphones - you could drive them perfectly well and extremely loudly for less than a tenth the cost of any of those devices you're looking at)

Thank you for the input.  I am currently running my headphones with a Schiit Asgard 2 that has an output of 1000mW but I wanted something stronger because I plan on getting into Planars in the next year so I figured picking up an amp for all-around use might be the best way to go.  Will having a gain switch help the avoid hearing the noise floor?  I would assume so.

post #4 of 15

For a given headphone, if you tell me the voltage, current, or power (one of the three) then that specifies the other two. Saying it's the current vs. power is a false distinction if you're trying to figure out what is harmful from a user's perspective (and not an argument regarding semantics, underlying physics).

 

As stated above, these are all maximum output specs. The actual power delivered depends on the volume level set. When you're not listening at ear-melting levels, you're not getting anywhere close to what the headphones can handle.

 

I want to know who actually uses planar magnetics at the 1W level (aside from possibly HE-6 at a peak), never mind 2W, 10W. That's deafeningly loud for those too.

post #5 of 15

The gain switch should help with both problems, yes. As for planars, I would think the Asgard would be more than adequate for the vast majority of planars out there, with the possible exception of the HE-6 (and even that one should be driven pretty darn well by 1W/channel).

post #6 of 15
Thread Starter 
Quote:
Originally Posted by mikeaj View Post
 

For a given headphone, if you tell me the voltage, current, or power (one of the three) then that specifies the other two. Saying it's the current vs. power is a false distinction if you're trying to figure out what is harmful from a user's perspective (and not an argument regarding semantics, underlying physics).

 

As stated above, these are all maximum output specs. The actual power delivered depends on the volume level set. When you're not listening at ear-melting levels, you're not getting anywhere close to what the headphones can handle.

 

I want to know who actually uses planar magnetics at the 1W level (aside from possibly HE-6 at a peak), never mind 2W, 10W. That's deafeningly loud for those too.

I came to that same conclusion from some google searches prior to initially posting this thread.  I was more trying to figure out what would be harmful to the headphones in general so it appears I just need to worry about wattage.  Yea I listen to music at reasonable levels, I enjoy this hobby too much to roll the dice on messing up my ears.

 

@your actual poewr delivered post

That was my understanding from memory.

 

@your planar magnetics at 1W comment

I was gazing at the HE-6 from afar lol but still need to listen to it at the upcoming local meet before I do anything.

post #7 of 15
Thread Starter 
Quote:
Originally Posted by cjl View Post
 

The gain switch should help with both problems, yes. As for planars, I would think the Asgard would be more than adequate for the vast majority of planars out there, with the possible exception of the HE-6 (and even that one should be driven pretty darn well by 1W/channel).

Agreed and thank you again for confirming this as that was my opinion also.

post #8 of 15

apart from possible hiss and difficulties with volume control (possibly channel imbalance), too much power doesn't look like a real issue. as mentionned it's about what the amp can deliver, but it will provide what's asked of it and nothing more. be it by current limit (what the headphone wants being the limiting factor is actually a great thing) or voltage limit (how loud you want your phone).

post #9 of 15
Quote:
Originally Posted by Byrnie View Post
 

Thank you for the input.  I am currently running my headphones with a Schiit Asgard 2 that has an output of 1000mW but I wanted something stronger because I plan on getting into Planars in the next year so I figured picking up an amp for all-around use might be the best way to go.  Will having a gain switch help the avoid hearing the noise floor?  I would assume so.

 

I personally can't see a good enough reason for "upgrading" from the Schiit Asgard 2 amplifier, with the headphones you are currently using.

I would say to invest into a decent DAC and connect it to the Asgard 2 and then consider buy a new amplifier (or DAC/Amp) after you have bought your Planars.

Might be newer model amps and DAC/amps whenever you get around to buying new headphones.

post #10 of 15
Thread Starter 
Quote:
Originally Posted by PurpleAngel View Post

I personally can't see a good enough reason for "upgrading" from the Schiit Asgard 2 amplifier, with the headphones you are currently using.
I would say to invest into a decent DAC and connect it to the Asgard 2 and then consider buy a new amplifier (or DAC/Amp) after you have bought your Planars.
Might be newer model amps and DAC/amps whenever you get around to buying new headphones.
I am starting to come to the same conclusion.

*updated* i have a Bifrost Uber, do you not consider that a good DAC or were you just not aware of that?
Edited by Byrnie - 5/31/14 at 3:43am
post #11 of 15
Quote:
Originally Posted by Byrnie View Post


I am starting to come to the same conclusion.

*updated* i have a Bifrost Uber, do you not consider that a good DAC or were you just not aware of that?

 

Bifrost Uber, seems like your in no need of any DAC or Amp upgrades.

post #12 of 15
Quote:
Originally Posted by PurpleAngel View Post

 

...I would say to invest into a decent DAC...

And, of course, you have appropriate double blind studies showing the need for an external dac for optimal sound quality, right?

post #13 of 15
Quote:
Originally Posted by cjl View Post
 

And, of course, you have appropriate double blind studies showing the need for an external DAC for optimal sound quality, right?

Nope, no studies at all, just going by what my own ears tell me.

post #14 of 15
Quote:
Originally Posted by PurpleAngel View Post
 

Nope, no studies at all, just going by what my own ears tell me.

Double blinded and level matched? If not, it really doesn't mean much here in Sound Science...

 

(Regardless, I would think that a Bifrost would do just fine as a DAC, so you definitely shouldn't need an upgrade there)


Edited by cjl - 5/31/14 at 10:48am
post #15 of 15
Thread Starter 
Quote:
Originally Posted by PurpleAngel View Post
 

 

Bifrost Uber, seems like your in no need of any DAC or Amp upgrades.

Thank you again for your input and reassuring me about my current rig.  Purrin said the same thing to me.

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