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Powerful amp for low impedance headphones

  1. Krellefdenmark

    So I am currently using the Ultrasone Pro 2900 driven by an Aune X1s.

    Yesterday, I noticed that the 2900's sounded somewhat veiled when being used below a certain volume - though not to the point that the volume was too low for that to be the issue.

    I asked the guy I bought them from, if he knew what was going on, and indeed, he did.

    He told me, that even though the headphones aren't that powerhungry, they do sound a bit veiled or muffled if being by an amp that is not powerful enough.

    Could one say that these headphones need an engine (the amp) which provides a lot of torque, and not only horsepower? Because the Aune can drive the 2900's to unlistenable levels (horsepower), but if it does not provide enough power (torque) at low volumes, it's no good.

    Is the analogy above somewhat accurate?

    If so, what amp would you choose or recommend me on a 100-150$ budget?
  2. MindsMirror
    I'd guess it's the output impedance which may affect the sound of the headphones. The headphones are 40 Ohm and the amp is 10 Ohm, which is above the 1/8th rule of thumb. The horsepower and torque analogy doesn't fits well here. I don't think there's a 1:1 car analogy for it, maybe drive train losses, or torque converter vs locking clutch? The Schiit Magni has plenty of power and low output impedance for $100, it works fine for all of my headphones so that would be my recommendation.
  3. PurpleAngel Contributor
    It's recommended to have the headphone to have an impedance (Ohm) that is 8 to 10 times the impedance out of the source (Head amp), for best detailed
    As the Aune Xi headphone amplifier has a 10-Ohm output impedance and the headphones are 40-Ohm, guessing the headphones will have a slightly bloated (louder, less detailed bass) and I guess a somewhat veiled(?) sound.
    The Aune X1 will provide more then enough voltage to drive the Pro 2900, so power is not an issue.
    The Schiit Magni or JDS Atom headphone amplifier have a very low output impedance (around 1-Ohm).

    Usually the lower the impedance of the headphone, requiring less Voltage, the more Current is needed.
    But my best guess(?) that is not an issue with your situation.
    Last edited: Dec 29, 2018
  4. ProtegeManiac Contributor
    Your most likely problem is the output impedance on the amp, and cranking it up just has the other frequencies catching up same way others crank it up to hear more of the low end. There's no way to tell without test equipment or trying something else though.

    That said, going for something with much lower output impedance but also much lower power output isn't likely to solve the problem. Best try to maintain comparable power if not more, with lower distortion, as well as lower output impedance just to be sure.

    Schiit Magni3 or stretch your budget to get the Meier Corda Rock from Germany.
  5. Krellefdenmark
    Thank you for your replies.

    I had thought that getting an Aune X7s to compliment the X1s would help, but that seems to have an output impedance of ~ 11 ohms, whereas I need one with 4 - 6 ohm (correct)?
  6. PurpleAngel Contributor
    The Aune X1S appears to have a line-output (RCA?) on the back, which you could hook a headphone amplifier to.
  7. Krellefdenmark
    Oh sorry, I meant that the X7s had an output impedance of ~11 ohms, and not the X1s
  8. ProtegeManiac Contributor
    Or even less - most amps have 3ohms or lower save for OTLs and a few others like the X1S, all the Beyer and Sennheiser amplifiers, etc.

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