@Compassionator - I've sort of ignored your last point in the above rambling; the hum is not even a mild irritation for me; the lowest-level details of all the music I've thrown at it is a much stronger signal than the steady-state noise. With the speed and microdynamic capability of the amp, I've never felt thirsty for more low-level information. I will definitely post in the coming months how I'm feeling after more extended ownership, but I haven't been tempted to switch my GS-X on once this week. For me, this one is definitely a keeper thus far.

Oh, and I may have misunderstood @smial1966 -- the RCA sockets do have colored rings (white and red) it just doesn't say which is input 1/2.

atubb - I have the furman power conditioner that you list above.
it, itself, emits a low level 60 Hz hum into any equipment I plug into it.
it's perfectly fine as a power conditioner for stereo equipment, but I don't think it cuts it for a headphone rig.  which is why I have other conditioners for that...
just saying, you may want to try without the Furman unit in there and see if the hum is any more or less present...

@TheWuss - that's a good point to consider; I tried it on a separate circuit with nothing on it as well as out of an APC S15 though I have not tried it with e.g. an isolation transformer. I haven't run into any hum from the Furman on my other equipment, but will keep an eye on that as well.

My Dragon IHA-1 does not exhibit any hum during operation. 

Well written and thoughtful review. Have had my eye on one of these for a while. I think the locking sockets spoil the look a little but perhaps I am being petty.

My IHA 1 has balanced inputs in addition to the RCAs. The noise goes away if you shift to the 6bx7s. With that tube it is dead quiet. I was reluctant to shift from the 6sn7s to the 6bx7s but the 6bx7 got a very strong recommendation from Dennis Had so I gave  it a try.  The amp sounds significantly better with the 6bx7s.  I would not have believed it if I had not heard it myself.  I use mine paired with a Gungnir Dac, SLP 05 and a Furman 2400 IT power conditioner. 40 years of listening to phones and I never heard anything like it. Now I just need to save up for the PS Audio Dac.

Using Tung Sol 6bx7s and EML 274b

Blake T -- Are you using 6BX7 or 6Sn7 tubes?

I feel all this wonderful useful information deserves its own thread outside of this review section and the Moon Audio thread. Don't you, fellas?

6BX7

Agree that Inspire IHA - 1 would benefit from its own thread.  I have no idea how to start one.

Going to try the 6BX7s again tomorrow (and quite possibly an EML 274b).

This thread would probably work (I'd started one but the linked thread predates mine).

Tried the 6BX7. The hum is present, but even quieter (have to really struggle to find it). Paying more attention now, I'm pretty confident it is only present in the right channel; the left channel is dead silent (at least with the 6BX7).

Could someone familiar with other SE OTL amps ( for example Woo WA2) discuss whether the holographic sound atubbs describes is a characteristic of this amp design or is unique to the DH amp?

@Bogart24 - just to be pedantic, this is not an OTL amplifier

Hardly pedantic.

With respect to the hum issue:  I have T1's and TH900's.  I had been using the T1's, and noted above that I could not hear any hum.
 
This weekend I decided to start listening with my TH900's.  Well, I also have a very slight hum in my right channel.  It is very subtle, but audible.  During music, I don't notice it at all.
Using the T1's, I can't hear the hum at all.  Dead silence, but switching to the TH900's, I can hear it (barely).  The hum is present with the single ended connector and the XLR connector (I have a custom adapter for my TH900's, which are reterminated XLR).  

To clarify- the hum I hear with my TH900's is definitely only in my right channel.  The left channel is totally silent.
 
With the T1's, both channels are dead silent.