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Headphone Amp "Minimum Load Impedance" Spec Clarification

carat

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Dec 25, 2021
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Sorry if this is a stupid question, but I've been googling it for 40 min and still not really any the wiser.

I was looking at at the headphone amp specs on a Behringer line mixer, and they included "Minimum Load Impedance: 100Ω".
  1. Does this simply mean that you must not connect headphones with an impedance rating of less than 100Ω? (seems obvious but I'm learning that impedance-related things aren't always intuitive).
  2. What would the consequences be of connecting, say, 50Ω headphones to an amp with a Minimum Load Impedance of 100Ω?
  3. I also read through the specs of several other Behringer devices with headphone amps on them, and none listed a Minimum Load Impedance spec. The manual for the Motu Audio Interface I just purchased doesn't mention it either. In fact, this is the first time I can remember ever seeing Minimum Load Impedance defined for a headphone amp. If it's important, why is it rarely included?
Thanks.
 

staticV3

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Does this simply mean that you must not connect headphones with an impedance rating of less than 100Ω? (seems obvious but I'm learning that impedance-related things aren't always intuitive).
Per Behringer's recommendation, that's what it means. Probably due to the Amp having very high output impedance.
<100Ω headphones may still work, but results could be suboptimal.
What would the consequences be of connecting, say, 50Ω headphones to an amp with a Minimum Load Impedance of 100Ω?
Low volume, change in frequency response
If it's important, why is it rarely included?
It's rarely needed nowadays because most Amps have almost 0Ω output impedance and so will work with basically any headphone you can throw at 'em. Some MFRs may still specify a load impedance of >8Ω for thermal or stability reasons.
If you see load impedance: >100Ω it most likely means the headphone amp is trash.

Edit: if you don't see load impedance: >100Ω and also don't see an output impedance spec, that doesn't mean that the Amp is good to go.
Many MFRs are lazy and won't bother (or don't want) to tell you how bad the products are that they're selling.

If you can't find basic performance metrics on the manufacturer's website, assume the worst.
 
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carat

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Per Behringer's recommendation, that's what it means. Probably due to the Amp having very high output impedance.
<100Ω headphones may still work, but results could be suboptimal.

Low volume, change in frequency response

It's rarely needed nowadays because most Amps have almost 0Ω output impedance and so will work with basically any headphone you can throw at 'em. Some MFRs may still specify a load impedance of >8Ω for thermal or stability reasons.
If you see load impedance: >100Ω it most likely means the headphone amp is trash.

Edit: if you don't see load impedance: >100Ω and also don't see an output impedance spec, that doesn't mean that the Amp is good to go.
Many MFRs are lazy and won't bother (or don't want) to tell you how bad the products are that they're selling.

If you can't find basic performance metrics on the manufacturer's website, assume the worst.
Thank you, this is useful info that I won't forget.
 
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