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Recommendation for USB audio interface, Low output impedance, low absolute noise level
googlebot
post Mar 31 2012, 13:00
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I have a pair of excellent IEMs with 119 dB SPL/mW sensitivity, that aren't too easy to drive on conventional higher-impedance headphone outputs (2-way balanced armature, <27 ohms). I'm looking for a desktop USB interface with manual volume control, a headphone jack with low output impedance (~0 ohms), and a low absolute noise floor (due to the low sensitivity). Many manufacturers post their SNR figures, which do not help me decide, whether the latter requirement is really fulfilled. For example, with the IEMs plugged into an onboard Realtek ALC261 output, which has got a SNR close to 100dB, I can hear the SSD working.

I had a look at the E-MU 020x devices, which seem to be great, but their 22 ohm headphone output jack looks like a constraint for the intended usage.

Could you recommend anything else?

*** Edit: I just noticed: Sorry, wrong forum. Please move to 'Audio Hardware' if you find the time.

This post has been edited by googlebot: Mar 31 2012, 13:14
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Nessuno
post Mar 31 2012, 20:06
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QUOTE (googlebot @ Mar 31 2012, 14:00) *
For example, with the IEMs plugged into an onboard Realtek ALC261 output, which has got a SNR close to 100dB, I can hear the SSD working..


You mean the SSD (wired on the same board?) causes EMI to sound card output or what?


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googlebot
post Mar 31 2012, 21:30
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QUOTE (Nessuno @ Mar 31 2012, 21:06) *
You mean the SSD (wired on the same board?) causes EMI to sound card output or what?


Yes, but at 119 dB SPL/mW that's no curiosity or necessary flaw. With "regular" headphones the output is excellent.

After some further research I have ordered an Audinst HUD-mx1 today. Looks like a solid product for a reasonable price, and 5 ohm output impedance should be sufficient (I hope). Couldn't really find an affordable, 0~ ohm, integrated solution, so I went for it.
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xnor
post Mar 31 2012, 22:12
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Is the HUD-mx1 usb isolated? If not it might not get rid of the noise. Either way, please let us know what you think about it once you get it.


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googlebot
post Apr 1 2012, 09:52
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Unfortunately I had read about the HUD-mx1's actual output impedance of 5 ohms after I had placed my order and immediately tried to cancel it. Due to the weekend it should have been early enough, lets wait and see how good their customer service is.

A headphone amp with high input and low output impedance should be sufficient in my case. The amp's input could then be driven in a voltage range, where the onboard DAC can deliver its rated SNR. The amp's output could then deliver a low voltage signal (and actually work as an active attenuator) to the IEMs.

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probedb
post Apr 2 2012, 08:26
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I use a FiiO E7 with my Westone UM3x which are more sensitive than your IEMs although easier to drive. It's very clean and I get no noise on it.
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googlebot
post Apr 2 2012, 19:44
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Coincidentally, I have tried the smaller brother Fiio E6 just this morning and can confirm your experiences. Zero audible noise, and, on the first look, excellent output impedance.

This setup (USB charger Y-cable into E6, E6 into front line-out, IEM into E6) is still a little bit messy to look at in my office. For aesthetic and ergonomic reasons I thus went for a Yulong U100, which I have ordered today. It iis supposed to have ~0 ohm output impedance with >120 dB SNR and is going to rest nicely on my table, where the IEM plug can reach it without an extension cord.

These Asian enterprises are really catching up with lightning speed. First, good only prices, then good prices & good quality, now all that plus excellent customer service. Getting a refund from Audioinst was friendly and almost instant. And the Yulong is already shipping with an expected window of 5 days around the globe (an upgrade to expedited shipping has been offered to me after the order had been placed at a discount price).
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googlebot
post Apr 12 2012, 19:36
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After extensively testing the Yulong U100 I can report that I'm more than happy with it. Sound and both relative and absolute SNR are exceptional.

IEMs provide an opportunity to drive 16 bit to its limits without damaging your ears, since a good portion of the baseline noise, that you have to live with in an usual listening environment, is kept out and you're feeding sound directly into your ear canal. Even with the maximum, pain-free listening level, recordings (and sometimes their recorded noise) seem to ascend from a floor of absolute silence - or the sound of my blood circulation (but my brain usually takes care of filtering out the latter).

The Westone UM2 has got an impedance curve like a rollercoaster. The U100 doesn't seem care, great bass, no perceivable roll-off whatsoever.
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Arnold B. Kruege...
post Apr 13 2012, 01:33
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QUOTE (googlebot @ Mar 31 2012, 08:00) *
For example, with the IEMs plugged into an onboard Realtek ALC261 output, which has got a SNR close to 100dB, I can hear the SSD working.


Sometimes noise from the audio interface traces back to bus contention in the PC. Treating the problem as electrical noise has no benefits.
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googlebot
post Apr 13 2012, 07:57
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And how is this supposed to be related to the thread? Components are connected via multi-Gigabyte/s point-to-point links nowadays. A 500MB/s burst from a SSD is peanuts.

Treating electrical noise in an usage range from 0-1 mW as a PC problem of the 90's has no benefits.

PS

Just because one can measure a >90 SNR into a high ohm load at several volts with most modern on-board codecs, these findings cannot be extrapolated to the SNR with when used with sensitive headphones in the mW range. People often don't get this and insinuate anything from imagination to 90's PC problems (which would sound much different BTW). I'm getting tired of this.


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stephan_g
post Apr 18 2012, 21:03
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Implementation is king when it comes to analog and mixed-signal components, onboard sound included. Extraneous noises on the headphone out usually are a result of bad routing (typically ground, including a connection of audio ground to case ground at the front panel) or inadequate supply filtering, reflecting time and space constraints. When time to market is critical, manufacturers usually have bigger problems than getting audio right.

It is, however, definitely possible to make onboard sound with a headphone output that's dead quiet - I know because I have one here, using an ALC262 (Fujitsu-Siemens D2587 board). OK, output resistance is kinda high (somewhere in the 47..100 ohm territory or so, sadly I misplaced my Y-dapter), and the most sensitive IEMs I can offer are SE420s, but at least I can tell that there is nothing severely wrong. (Like, say, the annoying ticking noises my old ClipV2 showed in Rockbox.)
Sometimes muting all the inputs is sufficient to get things quiet.
QUOTE (googlebot @ Apr 12 2012, 19:36) *
IEMs provide an opportunity to drive 16 bit to its limits without damaging your ears, since a good portion of the baseline noise, that you have to live with in an usual listening environment, is kept out and you're feeding sound directly into your ear canal. Even with the maximum, pain-free listening level, recordings (and sometimes their recorded noise) seem to ascend from a floor of absolute silence - or the sound of my blood circulation (but my brain usually takes care of filtering out the latter).

Even if filtered out, it's still there and covering things up though. (Case in point: The E6 still isn't considered entirely noise-free with very sensitive IEMs, yet you didn't notice.) My blood noise sometimes bothers me even with conventional headphones, which is why I tend not to listen to that much music in the summer (when temperatures and consequently blood pressure are high, not to mention outside noises coming in through open windows). AFAIK it takes deep-sealing IEMs like ER-4Ps to get rid of most of that, including noises while eating (super annoying, too). (ER-4s have been around since 1991? I did know they were available in '96. So it took over 15 years for the technology to become anything near mainstream.) Too bad I only have one ear canal compatible with triflanges at best.

I prefer a quiet environment and open headphones any day of the week. Whenever it's noisy, IEMs obviously are the best thing since sliced bread, and I was awfully glad when I got my first ones (public transport finally got bearable even with a bunch of noisy kids).

This post has been edited by stephan_g: Apr 18 2012, 21:03
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Porcus
post Apr 18 2012, 21:13
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What about a resistor to lower the sensitivity?


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Nessuno
post Apr 18 2012, 22:00
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QUOTE (stephan_g @ Apr 18 2012, 22:03) *
Too bad I only have one ear canal compatible with triflanges at best.


Ever tried to reverse the inner, bigger flange? A little trick that works like charm for me. smile.gif


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googlebot
post Apr 19 2012, 10:11
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QUOTE (Porcus @ Apr 18 2012, 22:13) *
What about a resistor to lower the sensitivity?


It alters your output impedance and can thus mess up your frequency response with low impedance headphones.

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Porcus
post Apr 19 2012, 11:05
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QUOTE (googlebot @ Apr 19 2012, 11:11) *
QUOTE (Porcus @ Apr 18 2012, 22:13) *
What about a resistor to lower the sensitivity?


It alters your output impedance and can thus mess up your frequency response with low impedance headphones.


Sure, in theory. But headphone manufacturers would have to face headphone outputs that are working precisely this way, by coupling the amplifier to either a serial resistor, or a serial + a parallel. If you have access to various headphone outs, then I guess you would get a reasonable idea of how your phones react, by simply trying them and listening for frequency response differences?


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googlebot
post Apr 19 2012, 11:49
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Anything with more than ~3 ohms output impedance causes an audible bass roll-off with my UM2. The amplifiers Westone ships with promo packages all have ~0 ohm output impedance. That's an indication, what they are targeting. IMHO targeting any other output impedance for a target frequency response is a lottery game.
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