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Headphone impedance and amp load

Macklin

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Hello everyone, I recently ran into a question I had in regards to headphone power and amp load. I purchased a Singxer SA-1 after I saw so many glowing reviews about this amplifier and based on what I gather in this forum the class A spec is as below:

SA-1's Class A model:
Balanced 16 ohm load: below 500mw
Balanced 32 ohm load: below 1000mw
Balanced load of 68 ohms: below 3000mw
Balance the load above 68 ohms: almost all power is Class A

So a couple of questions, if my headphone is say 50 ohms, would that cause the amp to run the balanced load of 68 ohm? That means I will have essentially 3000mw before this turns into class AB right? I used a headphone calculation website and even the notoriously hard to drive HE-6 which has an impedance load of 50 ohms and 83.5 db /mw, to drive it to even as loud as 115db would require 1414.56mw of power. So theoretically, if it is operating under the 68 ohm load, you still have a lot of room left before it is class AB?

Thanks for helping me out with this question.
 

wwenze

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It doesn't "switch between modes" but the power vs impedance rather follows a curve. So with 50 ohm a rough guesstimate would be around 2000mW. Probably slightly higher than 2000mW because the curve should be going exponentially up with higher impedance.
 
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Macklin

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I see, so basically I mean virtually all headphones will basically run in class A mode, even stuff like HE-6
 

JohnYang1997

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The power they give was actually incorrect. They used the point before distortion rises. But it was actually running in class AB mode already.

However in real world yes you would almost always at class A region.
 
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