Review: Portable amp roundup! 37 portable amps reviewed and compared

[DDF]

Originally Posted by Skylab

Also, DDF, w/r/t level-matching, I'm not sure I understand your point. I used a pink-noise track to match the levels of the amps, using the same headphones, to within 1db. Why wouldn't this work? Genuinely curious here. It seems that if all the amps were delivering exactly 80db at the headphones on the same pink noise track, then they're pretty well level matched...

Hi Skylab,

Thanks for clarifying that your tests used the same headphone, which is very important. For the uninitiated: different headphones can give the same SPL in free space (i.e. not on a head) but very different perceived SPL when used. Headphones produce different SPLs into different acoustic loads (seals), and each headphone is often uniquely sensitive to differences in the seal. So, lets say the gain of one amp is adjusted to measure 80dB in free space on one headphone with an RS meter, then repeated with another set of headphones; the perceived levels will very likely be slightly (1 to 2dB) to moderately (3 to 4dB) different between the two headphones (even if the RS meter gave the same SPL). This isn't a "major" level of difference but its more than enough to change a quality perception: for a careful listener, even 1 dB louder will sound better, all else equal. What this means is that to begin to really get a fair assessment of the small differences in amps, all the comparisons need to occur on one set of headphones. If multiple headphones are used, a good break should be taken between cans.

When all amps are used on the same headphone (sounds like they were), then its more accurate a test if the voltage level into the phones is measured, than if SPL is measured (the voltage to SPL will always be the same on the same phones). Even quite small differences in SPL meter placement will result in notable (easily 1, maybe 2 or 3 dB) reading differences out of the headphones. So even if the meter reads the same in different measures, you could be a couple dB out due to even small differences in placement. With a voltmeter and a careful hand on the amp volume control, you can easily nail this down to 0.1 dB matching. In order to get around any differences caused by amp o/p impedance, I measure the voltage using the actual headphones as the load. Take a y-adapter, cut off one connector, and measure the voltage on the stripped cables.

Skylab, I hope you don’t take this as a nock on your results. Your tests are very valuable, and it sounds like you were pretty careful. It’s just that by using a voltmeter instead of an SPL meter, you can helpfully further lessen some of the uncertainty, which may make a difference when comparing amps that are close to each other in SQ.

The other benefit beyond accuracy is that it fast to use a voltmeter to adjust the amps. If you don’t have a voltmeter, a PC sound card will work well. The amp o/p is fed into the sound card i/p and monitored. A great deal of freeware exists that will give a fast level measure (e.g. RMAA).

Dave

PS for context: I used to work in audio and at one time spent months in the lab designing/measuring/specing headphones, on everything from head and torso simulators, to telecom pinna to measuring headphones with Etymotic probe mics in ears of real subjects (more like victims; they didn’t take kindly to all the scotch tape running up their neck ). Measuring headphones present some “unique and difficult” (i.e. total PITA) challenges.

[Skylab]

Originally Posted by kramer5150

IMHO it should be noted that the Practical Devices XM4 has socketable OPamps. Its a dual OP amp design with one chip buffering the other (I think someone please correct me). I think its the only one in the review with this feature. Would it be possible to update your review with some commentary, on which amps have socketed OPamps and which do not?

What that means is the chips can be rolled for a custom sound that synnergizes with many different cans.

I wouldn't be surprised if it could rank higher on your preference list with a little OP amp rolling.

Thanks again for an excellent review, Mods cast my vote for a sticky.

This is quite true, that it can have op-amps changed. I probably should have said - I'm not into op-amp rolling, so I did not factor that in. But you're right - for another person, this might change the rankings for them.

[Jahn]

i just have to laugh at the size of the larocco versus the other amps. that thing is a beast! didja have to put it right next to a tomahawk like that? hehe. i'd still love to lug it around if it fit my camera bag that i always use for my portable rig (but it doesn't) - and that bag is about as big as i want to go when walking the dog and such, hehe.

[Skylab]

Originally Posted by Jahn

i just have to laugh at the size of the larocco versus the other amps. that thing is a beast! didja have to put it right next to a tomahawk like that? hehe. .

As you guessed, I did that on purpose. I love the PRII, but it's a different beast compared to the Tomahawk to be sure.

[silverrain]

I'll chime in -- most excellent review -- a "must-read" primer for portable amp considerations. And another x vote for possible sticky status....

[jinp6301]

great great review, and i Xnd for a sticky status

skylab, have you thought have making a value/quality list?

[robm321]

Very well done - I appreciate the comparisons.

I also wish the Xin amps were included, but this will help me get a grasp of where the amps rate without having to sift through thread after thread of opposite opinions.... Thanks again!

(...considering building a portable rig)

[Skylab]

Originally Posted by jinp6301

great great review, and i Xnd for a sticky status

skylab, have you thought have making a value/quality list?

That's a very interesting idea, although a tricky one to be sure. Especially when feautres start to come into play, and how valuable they are to different people.

I know for ME, the Hornet has the best value, even though its the second most espensive, because of its performance versus price, size, features, etc. But in some ways the Headphonia should be the winner, based on its lower price versus its performance and in light of all of its features.

I think it's best for me to leave the value judgements to each person individually.

[patgod]

Skylab, your post is the perfect example of the outstanding thoughtfulness, care and passion that never ceases to amaze me about this site. Great, great job, immensely invaluable, and I also recommend for a sticky. A great post for newbies to get a better understanding of what portables are available.

One suggestion: Have you thought about linking to the various manufacturers? (if allowed...) I found myself thinking, "hey, I've never heard of THAT amp before, how much is it, where can I get more info?" Just a thought...

-pat

[Dregur]

Hornet & Tomahawk:

www.raysamuelsaudio.com/

Xenos:

http://www.aptecpro.com/

LDM+:

www.little-tube.com

Practical Devices XM-4:

www.practicaldevices.com

Go-Vibe:

www.go-vibe-headphoneamp.com

Headphonia:

www.headphonia.com

Larocco Audio Pocket Reference II:

http://laroccoaudio.net/pr2/pr2.html

Don't have a webpage for the Xtra X-1 though...

Feel free to copy and paste, Skylab, if you want to.

-The Grinman

[Packgrog]

Originally Posted by JLai

Great review.

I'm surprised TH fans aren't up in arms about the Hornet M being higher ranked.

Why? It's a different and more powerful beast. Did anyone expect the Tomahawk to have BETTER sound than the Hornet M? I know I didn't. I was just hoping it would be close (and still excellent and better than most other portable amps), which apparently it is. There's only so much that can be expected from something this TINY. I love it, but if Skylab had ranked it above the Hornet M, I would have written it off as new-purchase fanboy glee. Heh.

Definitely agreed on the review itself, though. Very nicely informative! Thanks, Skylab!

[rhymesgalore]

Btw, you have missed one VITAL point for the RSA amps, which might be of uttermost importance to the user:

They work under water

If this isn't the ultimate feature of all

[JLai]

Originally Posted by Packgrog

Why? It's a different and more powerful beast. Did anyone expect the Tomahawk to have BETTER sound than the Hornet M? I know I didn't. I was just hoping it would be close (and still excellent and better than most other portable amps), which apparently it is. There's only so much that can be expected from something this TINY. I love it, but if Skylab had ranked it above the Hornet M, I would have written it off as new-purchase fanboy glee. Heh.

Definitely agreed on the review itself, though. Very nicely informative! Thanks, Skylab!

Ahh yes. I think in general, people who have heard both have voiced the Hornet edges out the TH ever so slightly. Not just 1 month ago, I was seeing threads on why the TH is better and how someone could straight up trade a used TH for a Hornet M (even though the Hornet costs $100 more). Glad to see the fanboyism is calming down.

[3x331m]

Originally Posted by Skylab

That's a very interesting idea, although a tricky one to be sure. Especially when feautres start to come into play, and how valuable they are to different people.
...
I think it's best for me to leave the value judgements to each person individually.

I like this kind of thought..... We, Head-Fiers, are not bunch of air-heads...

[jorgillo]

Great job, excellent and very useful review!

Thanks for sharing, Skylab

Sorry for my wallet