I'll chime in with a more detailed perspective, so those with IEMs looking at the Ember wont be needlessly scared be away.
First, for clarity, the Ember is safe to use with IEMs. It is capable of significant output power, so for the sake of your ears you won't want to be reckless with the volume knob. On the other hand, the high gain setting is great for hungry full size cans.
Does the Ember hiss with IEMs (when properly configured)?
22 Ohms - No (64 Audio U6)
16 Ohms - No (64 Audio A12)
9 Ohms - Yes (64 Audio a18)
Does it hiss badly at 9 Ohms? To my ears the hiss is minor, but noticeable, in between song and during quiet passages. To be fair to Jearly410, when it come to hiss, one persons "minor" might be another's "badly".
More Details
I own two of the original Ember 1 amps that Jeremy at Garage1217 has modified specifically to deal with hiss when using my IEMs. These modifications are standard in the currently shipping Ember 2 (aka - rev 2.1).
EricR's Project Ember IEM Use Guidelines*:
*feedback & additions encouraged
1) Use the Ember's low gain setting
2) Use a low gain tube (I prefer the 6SN7 tubes, thankfully they are all low gain).
3) Use an Input Attenuation module (IIRC it plugs into a socket on the back of the Ember 2, Garage1217 sells these).
4) Rev 2.1 added a 4-way jumper on the Ember 2, one of the 4 possible settings resolves a hiss issue I was having (sorry I don't know the exact jumper placement). From the Blog at Garage1217.com:
Now, we have 4 total settings:
- Through cap + resistor = default setting / results in ultra low volpot scratch with certain tubes that are a little leaky
- Bypass only the input resistor = This can lower background hiss on certain tubes like the 12ax7 / 5751 or 12at7 with ultra high efficiency headphones or IEM's
- Bypass input capacitor = Some purists do not like an capacitor on the input side so we give this option to eliminate it. Usually results in volpot scratch with most tubes but does not hurt anything
- Bypass the input cap AND resistor = For the purist that wants to lower background hiss on certain tubes like the 12ax7 / 5751 or 12at7 and not have an input cap
Oh man that sounds so complicated, what do I do? HA! It is actually simple as it gets like most of our settings. Changes can be made in REAL time while listening to music or background levels. Literally move a pair of jumpers and listen to the change or lack of change. If you like it better, leave it. If you like it less, change it back. Yes, life can be that simple! As with ALL settings on our designs. There is virtually NO right or wrong. Just what sounds best to your ears and THAT is what matters.
Thanks to a great customer Eric for helping spot the combination of things that increased hiss with his IEM's
A few final thoughts:
- YMMV, as ears and hearing will vary. Though the Ember is excellent and seems worthy of a trial.
- I own a modified Ember 1 and haven't heard the Ember 2 yet (but this subject has me seriously considering upgrading)!
- I don't have the SE846 either, though the impedance of my A18 Tsar CIEM is listed as 9 Ohms on the 64 Audio website.
- An Input Attenuation module with higher value resistors (than those Jeremy soldered to my Ember 1) might resolve the 9 Ohm IEM hiss issue.