Coming from Fostex/Denon biodyna's being my headphones of choice I went on a bit of an amp journey to find a great pairing for them and the Ember & Polaris is where I've ended and am fully satisfied with no need for searching out any other amps. Meier Corda JAZZ-ff and modded Gustard H10 were the previous amps. The Polaris is bit better all around than and less than half the size of an H10...absolutey lovely low end/subbase presence with little more forward mids/vocals. The JAZ-ff was not a good pairing at all for biodyna's...low end lacked presence and didn't sound lively, had a more flat & cold presentation.

Very much satisfied with the Garage 1217 amps - if you want a warm & lively sound from a biodyna driver they are a great way to go. The Ember II with either a Reflector 6H23P-EB or Sovtek 6H30P-EB tube is setup I like best overall for pairing with a biodyna, when I really want that ultimate subbass presentation and lively/punchy experience (at some expense of instrument separation, 3D spacial presence, and vocal presentation) I like running the Polaris. Both pair well with Sennheiser HD6XX series and the more lively sounding planar magnetics, like a Gold Planar GL2000 or certain HiFiMans, as well.

My tube amp setup has smoother, cleaner sound with bit better sounding vocals (more organic/live sounding) and a more expansive/3D sounding space and bit better separation for the music. The tube used really determines how it sounds... some tubes are extremely clean with maximum etheral 3D sounding space and maximum separation (like a Cifte 12AU7) while others are warmer more bassy focused with not much separation or 3D presentation and a bit of noise (like a Mullard 6201). Solid state is punchier, tighter with a more energetic sounding low end - but it sounds overall less separated/flatter in presentation. Prefer listening to tube amp without question... that certain special spacial sense & added separation along with that more 'live' vocal sound you get with right tube setup just doesn't exist with any SS amp I've heard... even a SR-L700/SR-L300 LE STAX with custom SS based amp setup (which has a pretty nice 3D separation & tracking/panning feel.)

Running RME ADI-2 DAC with Schiit Lokius EQ to a Garage 1217 Project Ember II amp w/ Sovtek 6H30P-EB preamp tube. Headphone is a modded Denon AH-D5200. Solid-state amp is a Garage 1217 Project Polaris.