General impressions of the Woo Fireflies Dac/amp as compared to the Resonessence Concero HP Dac/amp.
AKG 701s and AKG 551s.
Sennheiser HD 600s
Beyerdynamic DT 880s
Focal Spirit 1s
Focal Spirit Pros
The Fireflies sounds best with my PSB M4Us - and the Beyer Dynamics DT880s - and the Sennheiser HD600s.
Its a toss up.
So, as the Concero HP has no tube circuit to offer i will first compare for you the sound quality of the DACS found in the Concero HP as Compared to the Woo Fireflies and the Meridian Explorer and CEntrance DacPort.
The Dac in the Concero HP is a significant improvement in sound quality over the others listed.
The Fireflies by Woo sounds as good as the CEntrance Dacport or the Meridian Explorer.
The Concero HP Dac/Headphone amp offers more detail, more articulation, more dynamics, and a deeper and wider sound stage then presented by the Dacs found in the Fireflies, Meridian Explorer, or the Dacport.
The Meridian Explorer is a reasonably priced Dac and compares equally to the class A CEntrance Dacport, and both of these IMHO, are better then anything else in their price range.
Neither of the 3 can quite compare to the astounding fidelity found in the Concero HP Dac/Headphone amp .
I'd estimate as a percent, that the Meridian, Fireflies, and Dacport, can each achieve about 70% of the ResonEssence Concero HP sound regarding resolution, detail, articulation, and sound stage.
Also, it goes without saying that in this price range, and considering the companies that created these sound reproduction devices, you dont have to wonder about "EQ balance" regarding the Concero HP or the Fireflies.
Both have amazing frequency balance.
I find their individual sounds complimentary to each other when comparing the Fireflies as a Tube USB/Headphone amp with the Concerto as a Dac/Headphone amp.
Using all the headphones and music i listed, i would say that the Fireflie's Headphone amp is reasonably close to the tonality of the Concero HP but cannot touch the Conero HP regarding articulation, detail, dynamics, or depth of sound stage..
The Fireflies has a good Dac, while the Concero HP has a world class Dac.
As a USB Tube Headphone device the Woo Fireflies is incredible.
Attaching your favorite CD player to the Fireflies analog RCA imputs will give you a significant upgrade in sound through the headphones as compared to the output of your CD player's headphone jack.
I have a nice Marantz 24bit CD player and playing it through the Fireflies tube tube amp circuit is a decisive improvement over the headphone sound found in my Marantz.
Both the Concero HP and the Woo Fireflies deal with cymbals and reverb tails similarly, = lots of resolution and detail.
Both drive all the phones i listed with ease.
In my opinion, if you are using HD Sennheisers, and prefer this family's generally warmer tonality to the more clinical sounding Beyers or AKGs, then i would suggest you go with the Concero HP ..
I dont own Audeze headphones, so, i cant offer a true comparison for you of which would sound better regarding these 2 units.
The week of Feb 10th - 17th, 2014, i'll receive a set of custom ordered ZMF modified Fostex T-50RPs, and i'll post an update here regarding using those phones after examining them with both the Fireflies and the ResonEssence Concero HP.
If you can afford both the Fireflies and the Concero HP, then.....why not.
If you prefer the Tube sound in your headphones and view the USB Dac of the Fireflies as a insignificant "add on", then of course get the Woo Fireflies because it really is a Tubular wunderkind.
If a world class tube sound does not make your honey drip, then save your wallet $150-USD and get the ResonEssence Concerto HP as its a Killer DAC/Headphone amp.
And finally, 2 more for your consideration.:
The Woo Audio Fireflies looks like an Apple Device, and of course its aesthetic value is a step above the Concero HP.
I would say that if you mated the Fireflies with a Mac Mini you would have an amazing looking combo.
And also, the VOLUME knob on the Fireflies is miles ahead of the Concero HP regarding smooth feel and the way it more expertly integrates within the volume control circuit in your Laptop/PC.