Why do some amps provide more output power when using a balanced connection?

Al, you rock.  I've said it before and I'll say it again.  I think I will have to re-read your post a few times to properly digest it and understand it fully!  You have some serious knowledge.  Thank you!

- Mark

Apology accepted :-)

So the reason I wrote this post, besides sheer curiosity, is that it effects my configuration with my new headphone amp.  

A bit of background: I am using a Schiit Jotenheim to power a pair of Audeze LCD-2 headphones and connect to my main system with fancy DAC, turntable, and ARC preamp, etc. When the baby is asleep and I can’t listen to the speakers in the main system, I will be enjoying music with the headphones. I am connecting the Jotenheim with XLR cables to the tape out on my tube preamp. The entire system is balanced.

Since the Audeze LCD-2 is a bit on the power hungry side, and the Jotenheim is perfect for that, I will also be using the Jotenheim at my computer desk during the work day. That means moving the amp to my home office and connecting to my Chord Mojo running in DAC only mode. The output on the mojo is 3.5mm stereo jack. The amp section will be disabled and it will simply feed an analog line level signal to the Jotenheim.

Finally, I get to my question: Will the Jotenheim deliver the higher output that the specs suggest with the headphones connected to the balanced output, and the input on the Jotenheim using single ended? Or does the balanced input as well as the balanced output need to be used to get the higher watt output? I would like to be sure I am driving the LCD-2’s with the full power available.

I have yet to purchase a cable to connect the Chord Mojo to the Jotenheim. I can get a 3.5mm to XLR cable, if that is required to get the proper output. If not, I can get a simpler 3.5mm to RCA.

I posed this very question to Schiit, and they replied:

"The Jotunheim is balanced differential. Meaning it will not turn a single-ended connection to a "Fake" balanced connection. You may notice more power from using the balanced headphone output with a single-ended input but I cannot speculate on that."

One of the reasons I chose the Schiit Jotenheim was its output power using a balanced config, in my main system.  All good.  The computer desk use is secondary, though I will likely use it more frequently there.  If I can get the 3000mw output rather than 800mw at my computer desk, my headphones will be happier.  Apparently this is not going to work, according to the gent I heard from at Schiit.

Is there anything I am missing?

@almarg  

Hello Al,

so, I have read, re-read, researched, and digested. I found some other threads discussing balanced and unbalanced that you also posted on. I now feel that I have a reasonable working understanding of the concept.

I do have some more questions of course!

1. Is the design that Audio Research used in my LS-25 a reasonable way to deal with a balanced signal?  Or is it a “fake” balanced connection? I see they use the same method in their Ref 2 and Ref 3 line stages, Though my ability to accurately read a schematic  is questionable :-)

2. If balanced connections add more gain, why do you suppose Schiit is showing a difference in wattage output based on the balanced versus unbalanced operation in the Jotunheim?  

3.  Is there a way to test the difference in the driving Power into the headphone?  I mean, should I be able to detect an audible difference in wattage delivery If I compare fully balanced operation to fully single ended up operation?  

If I use RCA cables to connect my audio research preamplifier to the Jotunheim, and the standard single ended headphone cable, I should be getting 571mw of power. If I switch back to XLR from the ARC preamp to the Jotunheim, and use my balanced headphone cable, I should be back up to the 2143mw at 70 ohms that Schiit suggests in the specs (after applying your formula to adjust for the different load) But now after your explanation,  I am confused why the Jotunheim is outputting more wattage with the balanced connection at all.

In fact, I am less interested in the amount of gain that the Jotunheim delivers to my LCD-2 headphones, both settings, low gain or high gain deliver enough volume.  I am concerned about the wattage delivery.  I want the power and the control of the wattage to properly drive the headphones.  Audeze recommends 1-4 watts to drive them, and that is one of the reasons I chose the Jotunheim.