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How Much Difference Do Headphone Amps Make?

During touring I discovered that my in-ears do not always have the same sound (which would be very nice, so I have always the same reference). Sometimes the in-ears sounded very muddy and far away.

Because of this I started to do a number of measurements and tests.

My in-ears sound good and give the same frequency response on a Schiit audio hi-fi phone amp, AudioQuest DragonFly Black/Red and FisherAmp in-ear amp2. Because of this I used the FisherAmp as a reference for all measurements.

First I measured a FisherAmp in-ear Amp 2, PSM300, PSM900 and PSM1000 as a line-out (without the load of an earpiece):


Green: FisherAmp

Yellow: PSM300

Red: PSM900

Blue: PSM1000

As you can see, all four are almost flat. However, the PSM900 and PSM1000 have a serious low-cut and high-cut and around these areas there is also a bump (probably because of the used crossover filter)

The next measurement is with the load of the in-ear:


As you can see, the high response is different. The PSM300 and PSM900 give less highs, around 10 kHz a db or 3-4 less (a quarter of the volume!)

The following measurement is the same earpiece on two mixing desks:


Green: reference (previous measurement on the FisherAmp)

Pink: Midas Pro serie

Yellow: Midas M32

As you can see there is a serious difference in the highs. This is exactly the problem I experienced live. This makes the earpiece sound muddy and far away.

Because of this shocking discovery, I have decided to test all-in-ear type’s on a good and bad phone-amp at the dealer of a large worldwide in-ear brand, here the results:

3-way – 4 driver 18 ohms:


Orange: FisherAmp (reference)

3 way – 8 driver 16 ohms:


Orange: FisherAmp (reference)

3 way – 12 driver 15ohms:


Orange: FisherAmp (reference)

3 way – 8 driver 28ohms:


Orange: FisherAmp (reference)

As you can see, the earphones at the two phone-amp’s give a completely different frequency response.

The conclusion: a good earpiece does not always sound good, it is the combination of earpiece and phone-amp. Even the phone-amps in beltpacks give different results, but especially the phone-amps in mixing desks are shocking!

The surprising thing is that the 8 driver 28 ohm earpiece is not bothered by anything. Probably because of the higher impedance, It looks like some phone-amps are not made for a mega low impedance, this is probably the cause of the problems.

Another thing is, the impedance in the specification of an earpiece is the impedance at 1khz, but what happens at other frequencies?!?

Many good/widely used in-ears have a low impedance:

UltimateEars UE6Pro: 12,5 Ohms

UltimateEars UE Live: 10 Ohms

Westone ES50: 20 Ohms

Jerry Harvey JH10x3Pro: 18 Ohms

Jerry Harvey JH16v2Pro: 18 Ohms

So be aware of the phone-amp you use in combination with your in-ears!

Chiel Streutjes – CS-Audio –

2 thoughts on “How Much Difference Do Headphone Amps Make?

  1. Hi, I’m Roger Chen from Taiwan. I’d like to ask how do you measure “with the load of the in-ear” ? Is it electronic link or go through a ref mic in some special setup?

    1. Hi Roger,
      Chiel used an Isemcon measurement mic and a 7mm MiEMi™ to do this. You can read more about MiEMi™ here

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