Our customer IronLung reported hearing some background noise with sensitive IEMs. He tried JH-13, Shure 535 and other headphones with balanced armature design. These are very sensitive headphones with very low impedance, a rare breed.
Other customers did not report excessive noise, but IronLung did not like it — his lungs may be made of iron but his ears are not — they are are very sensitive (no offence, just praise).
While I didn’t have too many IEMs laying around (I’m mostly an over-head guy), CEntrance is located relatively close to Shure and I have some friends there from way back when. I used to run an engineering Dept. at Shure… Ah, the good old days…
Long story short, we obtained a couple of pairs of 535 headphones and confirmed that you could indeed hear some very faint background hiss if you listen very carefully and if no music is playing. Of course, if music IS playing, you better grab a hold of that volume knob, as those headphones are ULTRA sensitive and you could blow your ears out.
You see, HiFi-M8 is way overpowered for IEMs. To compensate for that, it does have a gain switch, which reduces the output signal level by a lot, to make sure it doesn’t rip the IEMs (or your ears) apart, but it’s probably not fair to use its output might to drive sensitive IEMs, which require tiny amounts of power.
It’s like taking your Aston Martin grocery shopping — you won’t get to see what the Bond car can do.
When I listened to the 535s, I didn’t find the level of background noise offensive, but with CEntrance, the customer comes first. We’ve decided to help the customer, tried several ways to lower the background noise and succeeded.
We now have a mod. We’ve modded the unit for the customer and will be sending to him shortly.
Please note — this mod only applies to users of balanced armature headphones with very little impedance of around 10 Ohm. Most IEMs are not like this, so very few people will be affected.
We could call the mod “IronLung mod”, but an even more appropriate name would be “The Balanced Armature IEM mod.”
Meantime, if you find yourself experiencing too much background noise, let us know. We have a mod for that.