I've always had hiss with my HA-2 with my IM02 and UERM. I tried another person's HA2 on the similar devices and had the same issue.

Weird, I'm not sure if it's an updated version, I bought it second hand.

Which version do you have? On my 2015 version, I switch the gain mode to "F" and the DAC/HP mode to "D". You should see the volume display show up as "--"

I usually just set it to the Fixed output mode when using it as a DAC.

I probably won't be able to make this, gotta help my family move that weekend. I'll update if plans change. Sorry about the late response.

I get some weird interference when using the HA-2 on my phone when the signal (like indoors). 

Thanks for having up there, guys. The DC scene is pretty darn active, have a feeling I'll be seeing some of you again.   Some impressions:   ZMF Omni prototype: definitely gave me a closed HD650 vibe with a slight hint of the T50RP treble spike. Pretty relaxing, I'd love to evaluate this for...

I may be able to attend.

Awesome meet! Thanks for having us up!

Why not just get a more powerful dedicated amp? 

Yep, way cheaper to experiment with.

I would usually prefer discrete components, but I got a good deal on the NFB28 on the used market. It turned out pretty well for me, all things considered, I even preferred the 28's DAC to the 1704 based Master 7.

I'd just invest into the headphones you know you like and the feature set on the DAC you want. Amps come and go.

For most purposes, I honestly think you're fine staying with single ended. I wanted the XLR outs from the preamp for my desk setup, so I personally splurged for the 28, but the 29 I think is going to sound just about as good.

Mahler's Symphony No 4 by the Budapest Festival Orchestra is quite good.