Quote:
Originally Posted by
H20Fidelity 
If you have time could you explain a little more about the output 2's P -> B circuit? I am rather interested in what it's purpose is and you mentioned binaural recordings, also I would like to correct the OP with a better explanation of what it does please. I did read on a Chinese site that output 2 widens the stage also which I could certainly hear.
As the story about IEM began, it was back in around the mid 80’s that a few rock stars began to invest into the development of IEMS (in-ear-monitor system) for their own hearing sake (with a few more advantages on the stage of course). Marty Garcia, founder and CEO of Future Sonics, is probably the first to complete the system and started the movement of high quality custom molded earphone for stage monitoring. A few years later in 1991, Etymotic answered the call of a more convenient, more universal and accurate monitor that is designed toward off-stage and general music listening, thus born the original ER4 – better known now as ER4B. B is for ‘binaural’, as ER4B is tuned toward binaural recording playback. As good as it is, ER4B is found to be a little too bright for the general, non-binaural recording. So Etymotic retuned the 4B and came out with the ER4S. S is for ‘stereo’, as in your typical 2 channels a.k.a. stereo recording in cassette and CD. Years later when portable audio became mainstream, Etymotic further tuned the 4S to 4P (as in ‘portable’) by reducing the impedance from 100ohm to 27ohm. Though 4P is easier to drive directly from a portable source such as portable CD player or DAP (digital audio player, or ‘mp3 player’ if you like), it doesn’t sound quite as accurate (a discussion later on). That being said, the only difference between 4S and 4P is on the ‘pod’ of the cable where the resistors are housed inside. By simply adding a 75ohm resistor adapter (which Etymotic does sell), you can essentially change the 4P to 4S. Unfortunately you can’t do the same to 4B since it has an extra pair of capacitors in the pod. The earpieces (where the balanced armature drivers housed) are essentially identical between the three models.
First of all, I am no expert, so if somebody more knowledgeable wants to correct me, please do so - you won't hurt my feelings 
. My understanding is that back in the day when the Ety ER4 ruled the IEM scene, lots of people bought the ER4P because it was easier to drive from their portable players (Walkman, Discman, early iPods etc - there were no DX100's back then). Those same people purchased portable amplifiers to use with their ER4P's, but many wanted the more analytical sound of the ER4S since the standalone amps provided them with enough juice. To up the impedance of their ER4P to that of an ER4S, they could either insert a separate 75 Ohm adapter between the amp and the ER4P, OR they could buy an amp with a built in impedance switch/jack. And looking back, a lot of amps from this era did have "P to S" circuits built into them. This circuit was in reality just a couple of 75 Ohm resistors, so it probably wasn't too difficult to implement.
The P to B circuit in the BH would just be a couple of resistors and a couple of capacitors. It's stated purpose is to turn an ER4P into an ER4B. So Output 2 is essentially useless to anyone who doesn't own a pair of ER4Ps.
I just find it odd that the BH, being a modern entry-level portable amp, would have a P to B circuit. P to B was not common even back in the day. Hell, you seldom see P to S anymore in today's new top end amps. I don't know, maybe the C&C designers are die-hard Ety fans (like me lol)?
I forgot about the amp last night, leaving it on for eight hours, yet still it continued soldiering on for my three hour listening session, then this morning for another hour, so I think we can safely say I'm up around 40 hours now, there's no sign of any power drop, the power light still shines bright, sound quality is the same. I find it quite amazing actually because this device sounds rather powerful, yet so efficient, from only the first charge.
I am quite surprised by the 80 hour battery claim too. From the pictures of the internals, the Li-Po battery in the BH doesn't seem any larger than those found in other portable amps.
I've discovered another C&C Model C&C F1, this amp is a little more expensive but is designed especially for IEM's and low impedance gear. It's rated at 100 hours for battery time
but only puts out 120mW, I suspect this would be perfect for IEM's. Does the store near you have this model in stock BustyBloke? It would be great if you could test it and give a quick comparison.
http://www.ebay.com.au/itm/250713550229?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649
If anything I may try the C&C F1 linked above
