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Headphone amp impedance
Old 19th October 2020
  #1
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Headphone amp impedance

I use Behringer HA400 for live, sometimes it drives only my earphones, sometimes one or two more.
This small amp has 80 ohms output while all of the headphones connected are from 16 to 32 ohm each.
The problem is I get distortion for any reasonably high amplification needed for in ear monitoring, the amp simply sounds bad.

Now I am trying to understand why, is this because it does not have enough power or the impedance of the headphones is too low?

I always believed that low impedance headphones are easier for the amplifier, however there is a rule that a headphone amp impedance should be at least 8 times less than the headphones impedance, so now I suspect that low impedance headphones draw more current from the amp that can not provide it thus the distortion.

Could someone please explain this to me?
Old 19th October 2020
  #2
Most headphone amps have an output impedance of less than 50 ohms. Why Behringer decided to have this a higher impedance is a mystery. The proper way for a headphone to work is to have a low output impedance at the output of the headphone amp and a "higher" impedance headphone connected to it. If you connect a lower impedance headphone (like 32 ohms) it will distort. Suggest getting a better quality headphone amp. This is what I use https://www.sweetwater.com/store/det...hone-amplifier and it has an output impedance of 51 ohms and I use it with some Beyer DT770 headphones that have an impedance of 250 0hms so it works well and I have no distortion. FWIW
Old 19th October 2020
  #3
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nosebleedaudio's Avatar
The specs show a max wattage of 40mW, or .04 watts with a 100 Ohm load..It does not show the distortion level, no doubt VERY high..Or they would listed it...
If you use a 16 ohm phones the level will no doubt drop and have very little driving the phones...
16 is VERY low..32 is very low IMHO..
Radio shack use to sell a 8 ohm phone, but that was to be used for power amps that had a direct phone output across the amp...Not a separate headphone amp circuit..If you know what I mean..

By the way, its not uncommon for headphone amps to add resistors to the output to reduce the current & protect the amp in case of a cable short OR too low Imp phones...
Old 19th October 2020
  #4
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Thanks. I need small, portable and not very expensive amp for 4 earphones when we play live, but all IEMs are at around 30 ohms and some of the more expensive amps are compatible with headphones from 32 ohms to 600 ohms, while very expensive ones go down to 16 ohms.

What I found is this:

https://www.ld-systems.com/en/soluti...ers/4095/hpa-4

Power output 4 x 100 mW
Minimum connected impedance 10 Ohm(s)


It should work well according to specs.

But there is something else I wanted to ask. Is there something like this but with integrated EQ? I am searching the internet for some headphones EQ but did not find anything. How this is possible?
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