[ReelDeal]

I am on the hunt for a new tube amp since I got ZMF phones. They are 32ohm. I have a Little Dot MKIII. It does not have enough power to drive them as loud as I want. (100mW into 32ohm).  My Schiit Magni 2 does a great job. It is 1.2mW into 32ohm. In my search for a new tube amp that can drive my ZMF's, is output wattage into 32ohms the only thing I should be concered with? Are there other specs that are relevant?

 

[12many]

I think efficiency is what you are after.

http://www.head-fi.org/t/168037/db-per-milliwhat-efficiency-vs-sensitivity-vs-how-loud-do-they-really-go

 

[ReelDeal]

Efficiency is a trait of my headphones, that definitely does play a part in how loud they get per given wattage compared to other headphones of a different efficiency. In my case, my headphones are a constant. They play sufficiently loud with my Magni 2, but not with my Little Dot MKIII. The obvious difference between those two amps is their wattage output. I am wondering if there is another factor I should consider in looking for a new amp. Something that would make one amp outputing say, 500mW into 32ohms drive my phones louder than another amp outputting the same wattage. Maybe current delivery or 

µF memory. I'm not familiar with technical details enough to know which factors affect their ability to drive a given pair of headphones louder.

 

[fjrabon]

You will also typically want a headphone amp thats output impedance is less than or equal to 4 ohms in order to avoid distortion. This isn't a hard and fast rule, but is a pretty good rule of thumb. The rule is you want amp output impedance to be 1/8 of headphone impedance or less. In general, the lower the amp's output impedance the more flexible it is with what it can power, as some headphones need more wattage and some need more current. The ultimate is a very low output impedance amp that also supplies a lot of power when needed.

 

[ReelDeal]

Thanks for the information fjrabon. I remember reading now about amp output impedance needing to be 1/8 of headphone impedance or less. That helps. 

 

[fjrabon]

Thanks for the information fjrabon. I remember reading now about amp output impedance needing to be 1/8 of headphone impedance or less. That helps. 

That being said my AudioEngine D1 is 10 Ohms and works great with my 32 ohm Grados, so there are certainly exceptions. I think the rule is primarily an issue for OTL tube amps. Of course when possible the best rule is the good old ear test.