• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Headphone Amplifier Testing and Measurements

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
44,368
Likes
234,381
Location
Seattle Area
Hello everyone. I like to expand my objective testing and measurements to headphone amplifiers. In that regard, I thought I start a thread on this and figure out what makes sense to do and test.

First, I need recommendations on headphones to use for testing. My Stax headphones unfortunately don't qualify since they have their own amps. The venerable Sony MDRv6 is good but it represents one data point for listening tests. What other headphones are common and don't cost a fortune? My limit is low hundreds of dollars.

On amps, what are the common choices? Are they popular or are people strictly opting for DACs with headphone amps?

On measurements I am thinking of distortion, maximum power, internal impedance, frequency ersponse and channel balance.

Appreciate any and all feedback. Those of you who are guests and have headphone experience, this is your chance to register and provide information that shapes the direction of what I will do! :)
 

watchnerd

Grand Contributor
Joined
Dec 8, 2016
Messages
12,449
Likes
10,408
Location
Seattle Area, USA
On headphones, I think you have to include the Sennheiser HD 600s in the test mix because they've been around for ages, are considered a classic benchmark, good value for money, and are a bit oddball these days with their 300 ohm impedance.

I'd also pick something from the AKG K7XX series (both the K7xX itself, but all the other number K7* models, like 702, 712, etc) because they're pretty common, come in multiple variants (colors, headbands, cords) of what is basically the same thing. 62 ohm impedance makes them a good 'middle tier' benchmark.

Add in a pair of mid-priced planars (HiFi Man 400 or 500 series) and some hard-to-drive IEMs and I think you'd have pretty good coverage across a wide variety of loads and sensitivities.

For amps, I would go to two extremes:

I would go with the JDS Labs Objective 2 as the epitome of the solid-state, reasonably price objective point of view.

And then I would go to the opposite end of the philosophical spectrum with something like Class A OTL SET triode like the Woo Audio WA3.

It also might be fun for you to measure my Schiit Mjolnir 2, which is a crazy tube or solid state (it has solid-state MOSFET "tubes" you can swap out with the actual tubes) fully balanced amp.

I would stay away from DAC/amp combos because a) you already review a bunch of DACs b) hardcore head-fi types often want to mix and match separates c) arguments about the sound of the DAC vs sound of the amp.

On measurements, I look for:

Output impedance
Power at 1% THD, 32 Ohms
Power at 1% THD, 50 Ohms
Power at 1% THD, 300 Ohms
 

tomelex

Addicted to Fun and Learning
Forum Donor
Joined
Feb 29, 2016
Messages
990
Likes
572
Location
So called Midwest, USA
Yep, measure all the standard stuff into 32, 50, 100, 300, and 600 ohms, 2 watt high quality resistors should do the trick for quick testing. Also, at these levels, noise measurements are critical IMO, and done first before the load heats up of course.
 
Last edited:

watchnerd

Grand Contributor
Joined
Dec 8, 2016
Messages
12,449
Likes
10,408
Location
Seattle Area, USA
And FWIW, I have the following headphones lying around:

AKG K271 Studio
AKG K701
AKG K7XX Massdrop Edition, black
HiFi Man HE 400i
 
OP
amirm

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
44,368
Likes
234,381
Location
Seattle Area
On headphones, I think you have to include the Sennheiser HD 600s in the test mix because they've been around for ages, are considered a classic benchmark, good value for money, and are a bit oddball these days with their 300 ohm impedance.
Indeed. I used to have one but gave it my kids years ago. I seem to recall paying 2X more for it than it sells for on Amazon now.

Record label post production houses almost all used the HD 600 back in early 2000s.
 

c1ferrari

Active Member
Forum Donor
Joined
Jul 11, 2016
Messages
276
Likes
43
Open-back and closed-back examples.
 

tomelex

Addicted to Fun and Learning
Forum Donor
Joined
Feb 29, 2016
Messages
990
Likes
572
Location
So called Midwest, USA
hd650 is also a reference among many audiophiles for Sennheiser stuff
 

oivavoi

Major Contributor
Forum Donor
Joined
Jan 12, 2017
Messages
1,721
Likes
1,934
Location
Oslo, Norway
I concur with the suggestions so far.

As for amps in the cheapo camp, here's what I'm using, based on recommendations from others: https://www.amazon.com/Superlux-HA3D-Headphone-Distribution-Amplifier/dp/B004ZFZI9Y

My headphones have a high enough sensitivity that I usually run them directly from my phone or computer. But when watching movies late at night together with my girlfriend, we use this amp in order to connect two pairs of headphones and control the volume for each separately.
 
Last edited:

watchnerd

Grand Contributor
Joined
Dec 8, 2016
Messages
12,449
Likes
10,408
Location
Seattle Area, USA
My headphones have a high enough sensitivity that I usually run them directly from my phone or computer. But when watching movies late at night together with my girlfriend, we use this amp in order to connect two pairs of clocks and control the volume for each separately.

Here's a weird scenario:

My Devialet 400 has no headphone jacks. So the suggestion , from the maker, is to run them from the pre-out jacks, using the ability to define the voltage output in software, and use an RCA->TRS adapter.
 

oivavoi

Major Contributor
Forum Donor
Joined
Jan 12, 2017
Messages
1,721
Likes
1,934
Location
Oslo, Norway
Here's a weird scenario:

My Devialet 400 has no headphone jacks. So the suggestion , from the maker, is to run them from the pre-out jacks, using the ability to define the voltage output in software, and use an RCA->TRS adapter.

Should work though, I guess?
 
OP
amirm

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
44,368
Likes
234,381
Location
Seattle Area
My Devialet 400 has no headphone jacks. So the suggestion , from the maker, is to run them from the pre-out jacks, using the ability to define the voltage output in software, and use an RCA->TRS adapter.
I am sure you get sound that way. Question is how high is its output impedance and how much power it delivers.
 

watchnerd

Grand Contributor
Joined
Dec 8, 2016
Messages
12,449
Likes
10,408
Location
Seattle Area, USA
I am sure you get sound that way. Question is how high is its output impedance and how much power it delivers.

It can output 4V per channel. I don't know the output impedance or amperage. Reported results seem to vary from good, to satisfactory, to meh, depending on the cans, which would imply (to me) it's not a high current choice.
 

Blumlein 88

Grand Contributor
Forum Donor
Joined
Feb 23, 2016
Messages
20,521
Likes
37,049
Don't get hung up on just circum-aural phones though such are often used by better heeled headphonophiles. Most people use earbuds. On ear or in ear or near ear clip on phones with cell phones for a source. So as well as testing some headphone amps, and dedicated music players, test the output of popular phones. Iphones, Galaxies etc. plus some tablets. Oh, and definitely get some of the Etymotics.

Maybe after trying a few representative headphone amps for a baseline, you'll have something like the budget DAC thread. Phones or cheap players that compete with expensive rigs. I also think some low priced prosumer recording gear will have surprisingly good headphone amps for surprisingly little money with lots of capability thrown in for nothing.

Much like some exotic speakers, headphones and headphone amps create something of a vicious circle. Exotic unreasonably hard to drive quality headphones create a need for super duty amps which fuel the market for energy guzzling exotic headphones. Your Stax needing something like a real power amp are an old niche example. Though Koss preceded them (those Koss ESP phones were sweeter sounding than the Stax though).
 

Blumlein 88

Grand Contributor
Forum Donor
Joined
Feb 23, 2016
Messages
20,521
Likes
37,049
Haven't had hands on with one of these. But it might have a good headphone amp.
https://emotiva.com/product/a-100/

Basic 50 watt integrated that uses a resistor to apply direct amp output to the headphone jack like old school stereo receivers of old. I have an old Sherwood receiver that has what would still be considered a brawny good headphone amp that works this way.
 

watchnerd

Grand Contributor
Joined
Dec 8, 2016
Messages
12,449
Likes
10,408
Location
Seattle Area, USA
Don't get hung up on just circum-aural phones though such are often used by better heeled headphonophiles. Most people use earbuds.

Are you sure about that? Aside from "freebie" earbuds, I think Beats are now the best selling brand:

u_10152165.jpg
 

Blumlein 88

Grand Contributor
Forum Donor
Joined
Feb 23, 2016
Messages
20,521
Likes
37,049
Audio Technica 40x and 50x models are excellent bang for the buck when you are ready to fill out that category. AKG 240s are another long standing standout in the below $100 price range.

Oppo PM3s are worth a look for more money. Or PSB headphones. Paul Barton has tried to do for headphones what Harman has for speaker development. NAD Viso HP50 is another Paul Barton design.

http://headphone.guru/meeting-the-legend-paul-barton/
 
Last edited:

Blumlein 88

Grand Contributor
Forum Donor
Joined
Feb 23, 2016
Messages
20,521
Likes
37,049
Are you sure about that? Aside from "freebie" earbuds, I think Beats are now the best selling brand:

u_10152165.jpg

I suggest a minimum a ban from further posting in this thread, and from posting images for one month. How offensive!!!!!

I rejoinder with the typical trope. McDonalds sells the most meals, it doesn't make them world leading gourmets.:p
 
Top Bottom