[Impulse]

How would the UHA-6S MKII handle low impedance orthos like the HE-500 or Mad Dogs (30-50 ohm, sub-90dB/mW sensitivity)? Particularly in comparison to a cheaper desk amp (like a Magni/O2)...

I'm looking for something semi-portable or at least transportable, the Leckerton would be more portable and I don't mind paying extra for the DAC and versatility (optical input in particular); but I've read lots of conflicting info regarding what I'd need amp-wise.

 

[Bill-P]

According to specs sheet, I'd guess the Leckerton UHA-6S Mk.II may be able to drive the Mad Dogs adequately, but it won't be able to do much with the HE-500, which requires quite a lot of power deliverance in order to deal with more dynamic music.
 
You may be able to reach listenable volume with the HE-500 for normal music, but then the amp would be strained to its absolute limits just to drive the headphone, and you'll quickly reach clipping point. For the HE-500, I think a desktop amp that can deliver more than 1W into low impedance is better.

 

[ardgedee]

Amplifier output impedance is irrelevant for orthodynamics.

 

[fzman]

Quote:

Amplifier output impedance is irrelevant for orthodynamics.

please elaborate.....

 

[Bill-P]

Amplifier output impedance is irrelevant for orthodynamics.

 
That may be true (especially since the UHA-6S has <1Ohm output impedance). But I was referring to power deliverance. This is from the specifications:

1. 30 mW into 16 ohms
2. 55 mW into 32 ohms
3. 110 mW into 100 ohms
4. 55 mW into 300 ohms

 
So it seems to me like the Leckerton UHA-6S Mk.II has a limit to how much current it can deliver to low-impedance loads.
 
This won't be a problem for IEMs that have low impedance and high sensitivity, but for orthodynamic headphones that have both low impedance and low sensitivity, it's a problem.

 

[ardgedee]

This is a good discussion of driving orthos, and so is this one.
 
The summary:
Dynamic driver impedance fluctuates with frequency.
Orthodynamic driver impedance does not, and there's nothing needing damping.
Amplifier output impedance isn't a big deal when driving orthos, and high current can do wonders for them.
 
This does not necessarily apply in the same way to other types of drivers: Dynamic, balanced armature, and so on. Each has their own idiosyncrasies, and some are far more likely to benefit from high damping factors.

 

[Questhate]

Don't think anyone was concerned about output impedence of the UHA-6S, but rather current output into low-impedence loads. 

 

[Bill-P]

Yeah. Please look at the specifications of the UHA-6S again. It's clear that they are limited in how much current they can deliver into low impedance loads (I'm guessing they're clipped to 40mA based on specifications). Orthos like the HE-500 would need a lot more current than that.
 
Here's an excellent list of how much power/current/voltage some headphones may need:
http://www.head-fi.org/t/476345/headphone-sensitivity-power-requirements-compared
 
The HE-5 stands right at the top of the list. 120dB may sound like overkill, but it may come in handy for quiet music/sources. Also having no headroom to drive the headphone can be bad.

 

[Tenormech]

FWIW, the HE-500/Leckerton pairing got a brief mention in the Innerfidelity review:
 
http://www.innerfidelity.com/content/leckerton-uha-6s-mkii-portable-headphone-amplifier-page-2
 

 

[ardgedee]

Quote:

That may be true (especially since the UHA-6S has <1Ohm output impedance). But I was referring to power deliverance.

 
Sorry, I misread your original question and then posted my longer response before I saw your second post.
 
 

Yeah. Please look at the specifications of the UHA-6S again. It's clear that they are limited in how much current they can deliver into low impedance loads (I'm guessing they're clipped to 40mA based on specifications). Orthos like the HE-500 would need a lot more current than that.

 
"Benefit from" is probably a better way to phrase it than "need". I think the demands of orthos tends to be overstated -- the best ones definitely benefit from top-quality sources, but it's rare that their sound deteriorates drastically out of lesser systems.
 
I ought to try the HE-6 on my UHA-6 and see how it sounds.

 

[Bill-P]

Quote:

"Benefit from" is probably a better way to phrase it than "need". I think the demands of orthos tends to be overstated -- the best ones definitely benefit from top-quality sources, but it's rare that their sound deteriorates drastically out of lesser systems.
 
I ought to try the HE-6 on my UHA-6 and see how it sounds.

 
Yeah, you're right. I overemphasized the "need" for more power.
 
It's true that when it reaches above 100dB, it shouldn't matter that much. And if my calculations are right, the UHA-6S can definitely deliver at least 100dB into the HE-500.
 
And the same thing seems to be true for the HE-6 as well.

 

[Bill-P]

By the way, here's how I'm feeding the optical input of the UHA-6S from my Galaxy S3.
 

 
 

 
And I'm still amazed at how much I am extracting out of Pandora's 128kbps music!
 
The amp is pretty brutal to low quality stuffs, but the DAC is equally good at masking those low quality stuffs away. It's okay out of USB, but I think optical (and maybe coaxial) is how this DAC should be used.
 
Also for those who are interested: I tried to replace the OPA209 with the OPA627 yesterday, and immediately put the OPA209 back in. The OPA627 sounded more laid back, and smoother, but it wasn't a match for the OPA209. To my ears (through the Audio Technica ES10), the OPA209 is just cleaner, clearer, and much more lively. It wasn't that the OPA627 lacked treble, or that the OPA209 boosted treble. It just seemed like the OPA209 removed bloat in frequencies that the OPA627 tried to accentuate for a fuller sound. Maybe the OPA627 is more suitable for thinner-sounding headphones, but I think the OPA209 suits me more.
 
What surprised me was how similar the two were. The OPA209 had inherited the bass control, the midrange body, and the smooth treble, along with the spacious soundstage of the OPA627. I thought the OPA627 was my favorite op-amp, but now I know better...

 

[Impulse]

FWIW, the HE-500/Leckerton pairing got a brief mention in the Innerfidelity review:

http://www.innerfidelity.com/content/leckerton-uha-6s-mkii-portable-headphone-amplifier-page-2

 

Yeah I'd seen that, and I generally find his reviews to be pretty objective... Tough he was also a bit vague and didn't really compare it to other amps either. I've also seen several posters that seem to be happy with the MD/UHA-6S pairing.

It's all rather confusing tbh, guess I need to do more reading about orthos... Not sure I understand their current requirements (or how to extrapolate that from the typical voltage specs).

 

[Tenormech]

That's a really intriguing setup, Bill-P. After your previous post about optical I went out and bought an optical cable to work with my iMac, and while I haven't plugged the USB back in yet for comparison, I think this is the best sound I've heard from my rig. It's definitely fuller bodied than using the line out from my iPhone, but it keeps the vocals and mids where I like them. I find with the USB I get more body in the sound, but sometimes I have to turn up the volume more than I like to get the vocal presence I want. I also feel so far that the optical feed gives more definition to the bass and low percussion.
 
Your setup suggests that a USB digital converted to optical is better than the USB implementation built into the Leckerton. Interesting, and it looks like a more affordable and portable rig than adding a CLAS to my collection. Why does everything I own have to be made by Apple?

 

[DigitalFreak]

Just so everyone knows, I'm currently listening to a vintage 600 ohm K240 Sextette using my CLAS-db and my Leckerton and although I have the gain on high and the volume knob at around 3 o clock the headphones are really sounding good. A little more headroom would be nice but the Leckerton does have enough power to drive power hungry cans.