Hissing with HeadRoom Micro Amp

[mkozlows]

So I just bought a pair of Shure E500 phones, and when I plugged them into my iRiver, it was Hiss City. This was a bit surprising to me, as I'd never noticed hiss with the Etymotic ER-4p (or, less surprisingly, the HD650s).

Well, okay, I figure that I need an amp. But just to make sure, I go over to the computer, and plug the iRiver's line-out into the Micro Amp's line-in. A lot less hiss, but still very audible. So I figure I'll take the iRiver out of the picture, and plug the Micro DAC back into the Micro Amp, and listen to music from the computer. The hissing remains at the same level.

The gain settings on the Micro Amp make no difference to the hissing, and it's volume-insensitive.

This is very surprising to me, as the Micro Amp is dead silent with the other headphones I've used. Have other people noticed this? Are there other amps that won't hiss with the E500s (like that Tomahawk, maybe)?

 

[kelvinz]

I got very irritated with the E500 hiss as well

I ended up replacing my ipod's with a Microsoft zune as there is no hiss whatsoever with the E500's

 

[M0T0XGUY]

My guess is the impedance of your phones is just too low for the amp, even if you have it set on low gain. IEM's are notorious for this hiss, and its audible on my iPod at all volumes using the ER6i's. Its curious that your ER4p's don't exhibit this white noise, however, because they were designed for portable use and had a lower impedance; if I recall correctly.

 

[GAD]

My ER4ps are dead silent with my micro amp. I don't notice any hiss with my ipod either, but I could just be constantly distracted by the icky non-amped sound.

GAD

 

[mkozlows]

Quote:

Originally Posted by M0T0XGUY /img/forum/go_quote.gif My guess is the impedance of your phones is just too low for the amp, even if you have it set on low gain. IEM's are notorious for this hiss, and its audible on my iPod at all volumes using the ER6i's. Its curious that your ER4p's don't exhibit this white noise, however, because they were designed for portable use and had a lower impedance; if I recall correctly.

Allegedly, the ER-4p is 27 ohms and the E500 is 36 ohms. So if the numbers aren't lying, that shouldn't be an issue.

What I guess I don't understand is, what's causing the hissing? I understand that it happens on lower-impedance headphones, but what's the real explanation for why it happens? And how can I get rid of it (as I really love these headphones, except for the hissing)?

 

[jjcha]

I raised this point with Tyll when they introduced the HeadRoom Coda, which is the predecessor to the MicroAmp. I was using Shure E5c (the most hiss sensitive IEM I've ever owned, even worse than E500) and the Sensaphonics at the time. When I replied that some other amps (SR-71) was black as night, he replied that it's because they've got a lot going on there (crossfeed) and it wasn't a simple "pure" design. He mentioned that it was a trade-off, and I can see his point. I certainly thought the crossfeed was quite good and that it was a trade-off perhaps worth making.

If you want to get rid of the hiss, you'll have to add an attenuator to the rig. I tried a impedance adapter (the one for Ety's ER4P) but it didn't get rid of the hiss completely and changed the sound too much.

Best,

-Jason

 

[mkozlows]

Quote:

Originally Posted by jjcha /img/forum/go_quote.gif If you want to get rid of the hiss, you'll have to add an attenuator to the rig.

A volume control comes with the headphones, and I attached that up and turned that down so the hiss was inaudible, and it seems to solve the problem, in the sense that there's enough juice in the player to get the desired volume out despite the volume control in the headphones.

So that's a cheap and easy solution. Now, what's an expensive and better one? I was thinking (before I tried hooking up to the Micro Amp) that I could just get a BitHead and be done with it, but it doesn't look like that would really solve the problem now. Will the Tomahawk take care of the hiss from a portable player, or is it intrinsic to the portable and no amp can get rid of it?

 

[jjcha]

It's not intrinsic to portable amps. I was using an iPod + SR-71 out of the lineout, and there was zero hiss with the Shure E5c. I haven't tried a Tomahawk but I imagine it would do quite well as well.

I haven't tried the iRiver's lineout in such a scenario though. Dunno if the iRiver outputs as clean a signal as the iPod's lineout.

Of course the MicroDAC has a very clean output as well. I never used the E5c out of it, but with the Sensaphonics (which are less hiss prone than the E5c), the Overture (MicroDAC predecessor) + SR-71 was absolutely hiss free (and a real impressive treat acoustically, I might add.)

Best,

-Jason