Ah ok I got ya. haha I didn't think of that. So no hissing then =) Hmmm that makes me rethink where I got the hissing though...I think its because I was thinking of pairing the CLAS R/MKIII. I think that the MKIII may be what may cause the background hiss. I don't currently have these but I am reading around looking for something to use with my CIEMs.

I have had the theorem 720 for a couple of days now and have listened for a few hours with many different types of music. I have compared the sound quality with my RSA intruder amp/dac using the same IEMs. My IEMs are the JH Audio 13 pros. I am using my galaxy S4 as the source. I am connecting my JH audio 13's to both amp/dacs using moon audio silver dragon balanced connector. I have both the theorem and the intruder set to the low output setting. I am using poweramp pro to play music when connecting to the intruder and USB audio recorder pro when connecting to the theorem. I only tested 16/44.1 files. The theorem 720 has a more neutral presentation than the intruder with more micro and macro detail with all types of music. The theorem fits the size of my galaxy s4 better especially for traveling. The intruder has a warmer fatter sound that covers up small details in the music. The theorem has a deeper soundstage that sounds more natural to me than the intruder. The theorem is much larger and heavier than the intruder. With my source and IEMs there is no question there is noticeable hiss when listening to the theorem. The hiss is easily heard when connecting the IEM cable to the theorem and turning it on while keeping the volume at the lowest setting. The hiss is not as noticeable while listening to rock/pop music. Unfortunately I can easily discern the hiss while listening to any music that has quiet passages. The XRCD2 version of Hell Freezes Over has great dynamics with very quiet passages. The hiss is heard in all of the quiet passages. The hiss is loud enough to obscure background detail and outer detail especially in classical music. The theorem pops and clicks when connecting my galaxy S4 to the USB port using the moon audio silver dragon USB cable. It has no problems using the same type of cable that comes in the box with the theorem. Overall I like the neutrality of the theorem better than intruder. However, the intruder is dead quiet with my IEMs. The better detail of the theorem is partially negated by the background hiss. The hiss covers over the very thing that makes the theorem so good - the greater detail. If I had to choose, Which I do have to choose. I have to choose the intruder because of the lack of background hiss.

My new Theorem 720 out the box pictures Source : iPhone 4 s Dac / Amp : Cyber labs Theorem 720 Cable : moon audio silver dragon v1 Iems : No hiss to low noise Earsonic Sm 64 v1. Unique Melody 3 DD universal Phonak Pfe 232 Hiss without music play Demo 1964 Fit Ear MH 335 DW Westone Um 3 x rc Headphone : LCD 2 rev 3 Zero Noise LCD 3 Zero Noise Fostex TH 900 can hear very low noise / hiss SQ out the box : I am under estimate from this dac amp Thorem 720 SQ excellent if without hiss to BA iems Power : the biggest power from portable dac / amp Is bigger than my Alo RX 3 B It is definitely more for Headphones than iems Is you like clarity ,very good detail , very good separation, very excellent bass impact and speed and wide and tall soundstage than Cyberlabs Thorem is your choice I love out the box SQ My IMO

My another pictures with 2 iems : Source : iPhone 4 s Dac / Amp : Cyberlabs Thouren 720 Iems : Unique Melody 3 DD Earsonic SM 64 v1 Ciem 1964 demo unit

My another pair set up with new Theorem 720 Source : iPhone 4 s Dac / Amp : Cyberlabs Theorem 720 Headphone : Fostex TH 900 Cable : cyberlabs stock cable mini USB to LOD

My another Therem 720 set up Source : iPhone 4S Dac / amp : Cyberlabs Theorem 720 Headphone : LCD 2 rev 3

It is plus point , Theorem has line output like my IBasso HDP R10 You can use your line out put as pure DAC from your Theorem . And connect to another external amp

Cyberlabs Theorem 720 as pure I Device DAC Source : IPhone 4 s Dac : Cyberlabs Theorem 720 as pure iDevice DAC Amp :Mass Ko Bo 385 Iem : Unique Melody 3 DD SQ : heavenly Sound Quality

My Cyberlabs Theorem driving balance headphones Source : iPhone 4s Dac / Amp : Cyberlabs Theorem 720 Headphones : LCD 2 rev 3 with Norse Audio balance RSA Sennheiser HD 800 with Whiplash customer made twag Twcu balance RSA Cable : mini USB to Lod stock cable from acyberlabs With balance cable you can get more balance in all frequencies I love my Theorem more and more

Ultrasone ED 8 Ruthenium best synergy with a Theorem 720 Source : IPhone 4 s Dac / Amp : Cyberlabs Theorem 720 DAC Headphone : Ultrasone ED 8 Ruthenium Cable : Whiplash Audio Twag / Twcu hybrid cable v2 balance RSA

You are right if pure portable what you prefer This Theorem can challenge one set of my 3 bricks with the same source my IPhone 4s That's why I am so happy now less 1 brick