[ChicagoPhil]

So I've had the UE-10s and Supermacro 3 for a number of months now, and only just discovered something... when I flip up the impedance switch on the amp, the background noise, or hiss, almost completely dissapears. Of course I have to turn the volume knob up higher, but hiss doesn't follow. Great news, right?

Well, I'm reminded of Dolby Noise Reduction on a cassette deck... along with the hiss, some of the upper treble seems to have gone with it. What I haven't settled on yet is which sounds more natural.

Why is this happening? Can someone explain what adding the extra resistance is actually doing?

Thanks,
Phil

 

[crypt@]

Check out the explaination from one of the sponsors' link above: http://www.meier-audio.homepage.t-online.de/tipstricks.htm.

It is interesting that you are getting hissing and other background noise. Do you hear them with just the SM3 on but the source powered off? With only the SM3 on, it should be absolutely black without any noise whatsoever. Then try again with the source on but paused the track. Again, it should be black void of noise/hiss.

If you are hearing noise with your source on at pause, it may be introduced by your IC. If you hear noise while your source is playing, then chances are the tracks are at fault.

 

[ChicagoPhil]

Quote:

Originally Posted by crypt@ Check out the explaination from one of the sponsors' link above: http://www.meier-audio.homepage.t-online.de/tipstricks.htm. It is interesting that you are getting hissing and other background noise. Do you hear them with just the SM3 on but the source powered off? With only the SM3 on, it should be absolutely black without any noise whatsoever. Then try again with the source on but paused the track. Again, it should be black void of noise/hiss. If you are hearing noise with your source on at pause, it may be introduced by your IC. If you hear noise while your source is playing, then chances are the tracks are at fault.

When the impedance switch is in the down position, with the UEs plugged in but no source connected, I get a faint hiss/noise. It gets slightly louder as the volume control is increased. When I switch the impedance switch to the up position, it goes black.

When my ipod is connected and on pause, with the impedance switch up, it's pretty much black througout the volume range. When the switch is down, it seems to get more noisy as the volume is increased. And engaging the gain switch magnifies these issues when the source is connected on pause.

Thus, I am left to think the gain on the SM3 at the normal impedance setting is a bit too high for the UE-10s 119db sensitivity and 13ohm impedance. This is also evidenced by the inability to turn the music "off" with the volume control. Even at the bottom of the rotation, music is very clearly audible at the normal impedance setting on the SM3.

Thoughts?

Thanks,
Phil

 

[jeffc]

Quote:

Originally Posted by ChicagoPhil When the impedance switch is in the down position, with the UEs plugged in but no source connected, I get a faint hiss/noise. It gets slightly louder as the volume control is increased. When I switch the impedance switch to the up position, it goes black. When my ipod is connected and on pause, with the impedance switch up, it's pretty much black througout the volume range. When the switch is down, it seems to get more noisy as the volume is increased. And engaging the gain switch magnifies these issues when the source is connected on pause. Thus, I am left to think the gain on the SM3 at the normal impedance setting is a bit too high for the UE-10s 119db sensitivity and 13ohm impedance. This is also evidenced by the inability to turn the music "off" with the volume control. Even at the bottom of the rotation, music is very clearly audible at the normal impedance setting on the SM3. Thoughts? Thanks, Phil

When the impedance switch is activated, a resistor is added inline with the headphones. In particular, output impedance of the amplifier is increased and the signal is attenuated. Actually, the UE10's are probably designed to be too sensitive. The transducers in the UE10 have a maximum loudness of over 140 db. As such, they can pick up all sorts of noises.

Since adding impedance changes the output impedance of the amplifier, and the UE10's AC-impedance is not flat, the change in the output impedance will color the sound.

 

[mrarroyo]

You can send the amp back and change the gain. If I recall it is 5 or 10 with the switch engaged. Or you could sell it and try another portable amp.

 

[Sugano-san]

It has always been my theory (and I have posted this before on head-fi) that the impedance switch does not work well at all with the crossovers in 2 or 3 way iems. i tried the switch with my um2s and the resulting decrease in sound quality was considerable. The etys, otoh, respond in an excellent way to the impedance switch. I figured the main difference between etys and um2s lies in the crossover, which is probably negatively affected by the addition of a 75ohm impedance.

as to the hiss, your iems are probably hyper sensitive, and no amp is entirely silent. you can always measure a little background noise even in the most expensive high end products. when hooking these up to extrremely sensitive speakers (or headphones) you can hear the hiss in the background.l that's a common problem with setups that combine 3 wpc triode amps (or the like) with 102 dB sensitivity room speakers. high efficiency speakers let you hear all kinds of things youre not interested in.

i wouldnt worry about it and just leave the impedance switch off.

 

[crypt@]

Quote:

Originally Posted by jeffc ... Actually, the UE10's are probably designed to be too sensitive. The transducers in the UE10 have a maximum loudness of over 140 db. As such, they can pick up all sorts of noises...

I second that. UE10 does seem to have a rather high sensitivity rating, ER-4 is only:

1 kHz sensitivity (ER•4B/ER•4S): 108 dB SPL for a 0.79 V input (90 dB @ 0.1 V; 100 dB @ 1mW).

The fact that they picked up noise with only SM3 connected, can only suggest that the gain level is too high for the UE10. I too feel the only way around it is to reduce the gain if you wish to use the amp. Adding 75ohms may not necessary work well for UE10. That impedance is really intended for ER-4P and as such may adversely coloured the UE10 instead of enhancing them.

However, don't forget the most importanct part - your own hearing and don't put up with hisses.