Originally Posted by IceClass
Anyone used the 720 with the Sure SE846 IEMs?
Any noticeable hiss?
There is definitely a hiss when using it with the Sennheiser IE800. It's about the same level of hissing as the ALO Rx Mk3-B+ amp; although it might be just a tad bit quieter than the CLAS -dB -> ALO Rx Mk3-B+ combo with sensitive IEMs. Still, at least with the IE800, you get used to the hiss and it "melts" into the background after you get music playing for a little while to the point where you barely notice it at all. Even when watching YouTube videos and movies, the hiss is 100% tolerable but it does exist.
At first I tried to use impedance adapters to acquire a completely "black/quiet" background on my ALO Rx Mk3-B+ amp, but didn't like how it changed the sound, so I just got used to the (tolerable) hiss on the ALO amp where it doesn't bother me at all anymore. So far I'm really liking the sound of my Theorem 720 when connected to my laptop, as it sounds a little different than my CLAS -dB/ALO Rx Mk3-B+ stack (in a good way.) It seems to be a little more "fun" sounding than the combo, and I can keep the Theorem plugged into the charger when using it at my desk 24/7 without issues (because there are a bunch of issues w/ the stack, including some balanced interconnects being too long/big in the stack, thus preventing charging/access to the charge ports for the -dB/Mk3, and with the Mk3-B+, having some weird "ground hum" issue in the background in balanced back-end mode while charging the amp.)
With that said, I've been having some issues with my Theorem 720 so far, mostly having to do with my iPhone/portable use (since I was hoping to get the Theorem 720 to replace my Fostex HP-P1.) Sadly, when the Theorem 720 is connected to my iPhone 3GS, it picks up a ton of cellular network interference (buzzing/"grinding"/chirping/etc.) from my 3GS to an intolerable degree, to where the only way I'd be able to use my phone with the Theorem would be only in "Airplane Mode." This kind of makes the Theorem a bit "useless" for use with my 3GS, since I can't keep my phone in "Airplane Mode" when on-the-go. My 3GS doesn't have any interference issues whatsoever with my Fostex HP-P1, so I find this pretty odd honestly :(
I was thinking this issue might be specific to older iPhones (my 3GS), and that maybe an iPhone 4S would be "shielded" better and wouldn't have this cellular network/RF/etc interference issue w/ the Theorem 720? I've been considering maybe picking up a used 4S (64gb) from Amazon if this is the case, so that I can use the phone with the Theorem 720 (and other CLAS devices) without this major RF interference problem.... I did notice recently even before I purchased the Theorem 720 that whenever I placed my 3GS/HP-P1 stack close to my CLAS -dB/ALO Rx Mk3-B+ combo (while listening to my CLAS -dB from my laptop on my desk), I would get some mild buzzing/interference whenever the phone was communicating with the cellular network (such as push notifications), which I initially found very weird too (since CLAS -dB is supposed to be used w/ iPhones specifically), which is why I have to keep my 3GS further away from my CLAS gear on my desk now.
Edited by refault - 1/25/14 at 5:47am