I have been trying different Inputs and gauging the sound quality.
a) APPLE Port (USB Type A)
I connected my IPAD 3 to this port using the lightning cable and found the sound to be quite pleasing .Please note that IPAD doesnt support FLAC natively .You need to either download the free FLAC player apps or the paid version which I heard is better sounding than the free versions floating around in app store . Sound stage was not great but clarity and bass were fine if not loose.
ITunes Radio through IPAD acted a bit finicky when connected through this port, I found that it stutters quite a bit sometimes when connected and other times it played perfectly fine. But it plays perfectly fine on Bluetooth.
Normal music playback was perfect though with no issues.
Verdict: Over all its perfectly fine for casual listening
b) Bluetooth
QUAD Vena supports the supposedly better Bluetooth format called APTX. I have a one plus one Phone which unfortunately doesn't support Bluetooth APTX. Any ways, I connected the quad Vena to my Bluetooth which is an extremely simple affair and once paired, it automatically pairs with my phone almost every time as long as I had the Vena on Bluetooth source mode and my phones Bluetooth is ON. Almost every time. Other times I had to manual connect the Paired amp through my phones Bluetooth menu. Not a deal breaker for me.
I found the sound quality to be almost the same as that of apple Dock port. Whatever minimal loss there was in sound quality when compared to the apple port was negated by the fact that I can control the playback lying down in my bed wirelessly.
Again I would rate the sound quality through Bluetooth to be quite good for casual listening or party times. In fact it may surpass most peoples expectation for sound through Bluetooth. I will update this when I get my hands on an APTX enabled Phone.
Verdict: Over all its perfectly fine for casual listening
c) Optical Input: Toslink
I am using an extremely basic Bandridge Optical cable 1.5 feet Bought on Amazon for 150 bucks. I connected My PS3 with my Quad Vena through the same. Playing Indian Audio CDs I found that the sound quality is definitely better when compared to Apple dock port or Bluetooth (obviously). The bass is much more defined and the sound stage improved immensely. Voices sound very sweet and overall theres a big improvement to sound definition .Playing games with good background score like Crisis series sounded amazing though the optical Input. Gunshots sounded really good and so did my grenades: P
Unfortunately I couldn't find an easy way to connect my PS3 to my Vena through line level inputs. For those who are not aware, PS3 doesnt have line level outputs. It only has a HDMI port and an optical Output. Now thinking, I find this incredibly stupid on Sonys Part.
Verdict: Over sound quality is much better than Bluetooth and apple dock port
d)Coaxial Input:
I am waiting for coaxial cable from Amazon at the time of writing this. I am planning to connect my Airtel HD DTH to the quad. Will update soon
e)USB Type B:
I had no great expectations when it came to this input type. But it surprised me, in fact shocked me. I connected my oneplus one to an OTG cable and that in turn was connected to a USB Type A to Type B cable to the Vena and I installed the USB audio Player Pro version on my Smartphone which sells for around 550 Bucks on Play store. The sound in one word is mind blowing. Mind you I am no seasoned audiophile but I found the playback to have gained immense depth, sound staging, separation and what not. My only extremely minor complaint was that the bass extension was less in this mode but it compensated by making the bass lines very tight. Over all I was blown away by the sound quality through this input and it made me listen to entire albums of chesky records binaural recordings which usually I dont do. Stereo imaging improved vastly compared to all other inputs I tried and I truly felt that this was Hi-Fi sound and not just good sound which was through the other inputs I tried
My research suggests that the USB audio Player Pro app on android app store had a major part in this over all sound improvement so I would whole heartedly recommend that app even though its a paid one
Verdict: Simply put if you have this Amp and dont have a CD player, this is the input to get your moneys worth