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Apogee Duet and ER-4S

post #1 of 27
Thread Starter 
While it isn't my goal to review the already well known Etymotic ER-4S, nor really to provide an in-depth look at the Apogee Duet, I thought it worth taking a few moments to post some impressions I've developed after using the Duet as a DAC/headphone amp combination, especially with the ER-4S.

First of all, a quick look at the Apogee Duet in use on my desk:



I have posted some very general impressions in various Duet-related threads concerning this device's performance with my HD580 and DT770/80 Pro, and I will shortly repeat here that I think the Duet does an excellent job as both a source and an amp for these headphones. It didn't take me long, however, to get around to finally listening to the Duet with my ER-4S. Until acquiring the Duet, I had only listened to my ER-4S via my 5G iPod and Hornet. Switching to the Duet in a desktop environment was quite a change for me after getting so used to the sound of my portable setup. To get right to the point, I was somehow bothered by the mind-blowing level of clarity and, especially, detail the Duet brought out of my ER-4S. I have made it a point to take some time to play around with this setup some more and try to figure out what, if anything, I could do to optimize the listening experience with these IEMs.

Today, I have done some simple testing (mostly just having a good time!) listening to Björk's Medúlla and Post albums, playing these albums from start to finish via iTunes with Apple Lossless files. I always enjoy the musical complexity of these albums, and this time around I found myself as involved as ever in the music and sounds (are these different?). Within minutes of starting this listening session, I remarked a stark blackness between notes, and a purity of sound the likes of which I have probably never heard before. The level of detail and sense of space around instruments was lovely, especially considering the fact that I was using IEMs. Still, something didn't quite satisfy me in the same way that my HD580 and DT770/80 Pro have with the Duet. For lack of a better way to explain what I mean, I will say that the music seemed to lack a very slight amount of realism and texture. And I don't mean any sort of veil, but rather something that sounds even better than reality, and therefore a bit on the synthetic side for my tastes.

Then I started considering the configuration of the Duet and of my Mac, and I decided to play with the settings that I'd initially made in Audio MIDI Setup. When I first starting using the Duet, I went right away to Audio MIDI Setup and made sure to set the audio output format to 96000.0 Hz. This setting indeed yields the best results for my other headphones, but after changing the setting to 44100.0 Hz as shown below...



and listening to the same to albums all the way through, I can say with confidence that, at least to my own ears, this brought about exactly the changes I was after. I don't want to say that the results were just like listening to the ER-4S with my Hornet, but the gap was certainly closed a bit. The detail is still there, but I can somehow grasp the edges around various sounds, including Björk's vocals. If I had an appropriate cable, I would love to use the Duet as a source to feed my Hornet for comparison, but that won't be possible unless I decide to invest in a custom cable (1/4" male TS-to-1/8" TRS). The clarity of the Duet's DAC is simply stunning, and with the texture and realism the lower sample rate brings about, there are parts of this music (especially from the Medúlla album) where it actually felt as though someone was physically whispering or blowing down my ears.

That's all I have to say for now, and I hope to hear from anyone else who gives the Duet a try with IEMs. Thanks for reading.

EDIT: Hmm, I really should have put this in the Computer Audio (Computers-as-Source Components) forum. Maybe a nice mod could move it there?
post #2 of 27
Quote:
Originally Posted by Jaska View Post
When I first starting using the Duet, I went right away to Audio MIDI Setup and made sure to set the audio output format to 96000.0 Hz.
The best quality is achieved by matching the output sampling rate to the source sampling rate.

Quote:
Originally Posted by Jaska View Post
If I had an appropriate cable, I would love to use the Duet as a source to feed my Hornet for comparison, but that won't be possible unless I decide to invest in a custom cable (1/4" male TS-to-1/8" TRS).
Using the breakout cable, you can connect a standard 1/8" TRS to L-R RCA cable.
post #3 of 27
There aren't rcas on the standard breakout cable. But you can get adapters for 1/4" to rca at radio shack.
post #4 of 27
Thread Starter 
Quote:
Originally Posted by koto-in View Post
Using the breakout cable, you can connect a standard 1/8" TRS to L-R RCA cable.
I tried to be clear in my post that I know I certainly can use my Hornet with the Duet, but that I'd have to invest in another special cable. I'm holding off on that, as much as I'd like to try it, because I'll most likely end up just adding a new home/desktop amp to the setup and using the brand new custom cable I already had made to use in this manner.
post #5 of 27
Thread Starter 
Quote:
Originally Posted by koto-in View Post
The best quality is achieved by matching the output sampling rate to the source sampling rate.
I won't argue with that, and will admit that I've configured my settings based on my actual preferences in various listening tests with my headphones and IEMs. But, just for further thought, this web page suggests the following:

For users of iTunes under Mac OS X with 96/24 output devices, we offer the following two different, recommended solutions:

1. The ‘Set It And Forget It’ solution for iTunes 7.x: Before opening iTunes, set the sample rate of CoreAudio (in AudioMIDI Setup) to 96 kHz. Do not change the sample rate of CoreAudio unless iTunes is restarted after the change is made. This solution will prevent CoreAudio from applying SRC, as the quality of CoreAudio’s SRC is horrible. Also, by having iTunes locked at 96 kHz, all audio with sample rates below 96 kHz will be up-sampled to 96 kHz. This will cause virtually no loss in sonic quality, as the quality of iTunes’ SRC is very good – virtually inaudible. Also, by avoiding down-sampling by iTunes, this setting will never result in a loss of bandwidth (except with sample rates greater then 96 kHz).

2. The ‘Bit-Transparency For Each Sample Rate’ solution: *CAUTION: This solution is rather cumbersome, offers virtually no quality improvement over the first solution, and can easily be mis-configured which can cause severe distortion. Before opening iTunes, set the sample rate of CoreAudio (in AudioMIDI Setup) to that of the audio you will be playing. Do not change the sample rate of CoreAudio unless iTunes is restarted after the change is made. This solution will prevent CoreAudio from applying SRC, and avoid SRC by iTunes for all audio with the same sample rate at which iTunes is fixed.
post #6 of 27
Quote:
Originally Posted by Jaska View Post
I won't argue with that, and will admit that I've configured my settings based on my actual preferences in various listening tests with my headphones and IEMs. But, just for further thought, this web page suggests the following:

For users of iTunes under Mac OS X with 96/24 output devices, we offer the following two different, recommended solutions:

1. The ‘Set It And Forget It’ solution for iTunes 7.x: Before opening iTunes, set the sample rate of CoreAudio (in AudioMIDI Setup) to 96 kHz. Do not change the sample rate of CoreAudio unless iTunes is restarted after the change is made. This solution will prevent CoreAudio from applying SRC, as the quality of CoreAudio’s SRC is horrible. Also, by having iTunes locked at 96 kHz, all audio with sample rates below 96 kHz will be up-sampled to 96 kHz. This will cause virtually no loss in sonic quality, as the quality of iTunes’ SRC is very good – virtually inaudible. Also, by avoiding down-sampling by iTunes, this setting will never result in a loss of bandwidth (except with sample rates greater then 96 kHz).

2. The ‘Bit-Transparency For Each Sample Rate’ solution: *CAUTION: This solution is rather cumbersome, offers virtually no quality improvement over the first solution, and can easily be mis-configured which can cause severe distortion. Before opening iTunes, set the sample rate of CoreAudio (in AudioMIDI Setup) to that of the audio you will be playing. Do not change the sample rate of CoreAudio unless iTunes is restarted after the change is made. This solution will prevent CoreAudio from applying SRC, and avoid SRC by iTunes for all audio with the same sample rate at which iTunes is fixed.
The point of this article to avoid unnecessary SRC and in particular SRC by Core Audio. If you are playing music in iTunes with a variety of sample rates, then Benchmark's recommendation 1 would be a comfortable setup that would obviate the possibility that high sample rate audio might be downsampled. It does however create a condition where low sample rate audio will always be upsampled. This will not improve sound quality and could in fact degrade it. Notice that they state, "this will cause virtually no loss in sonic quality." Matching Core Audio's output sample rate to the sample rate of the source, as stated in Benchmark's recommendation 2, will eliminate any SRC at all and will result in absolutely no loss in sonic quality. If you are playing 44.1 kHz audio, then setting Core Audio output at 44.1 kHz will avoid any SRC and therefore eliminate the possibility of unnecessary signal distortion. This should theoretically provide the best possible sound quality.
post #7 of 27
Thread Starter 
Quote:
Originally Posted by koto-in View Post
If you are playing 44.1 kHz audio, then setting Core Audio output at 44.1 kHz will avoid any SRC and therefore eliminate the possibility of unnecessary signal distortion. This should theoretically provide the best possible sound quality.
I understood this the same way. I have a lot of 48.000 kHz content, and don't want to downsample it. When using my HD580 and DT770/80 Pro, I notice absolutely no degradation of quality when playing back 44.1 kHz audio with iTunes and Audio MIDI Setup configured at an output rate of 96.000 kHz. My ER-4S are somehow sensitive to this, though, and that was really the point of my original post.

I suppose I could make a universal "set it and forget it" compromise and configure Audio MIDI Setup to output at 48.000 kHz. What are other Duet users doing about this??
post #8 of 27
why do you have lots of 48k content?
post #9 of 27
Quote:
Originally Posted by Jaska View Post
I understood this the same way. I have a lot of 48.000 kHz content, and don't want to downsample it. When using my HD580 and DT770/80 Pro, I notice absolutely no degradation of quality when playing back 44.1 kHz audio with iTunes and Audio MIDI Setup configured at an output rate of 96.000 kHz. My ER-4S are somehow sensitive to this, though, and that was really the point of my original post.

I suppose I could make a universal "set it and forget it" compromise and configure Audio MIDI Setup to output at 48.000 kHz. What are other Duet users doing about this??
With the ER-4S, I think your ears are telling you something. If you somehow have a lot of 48 kHz content, then it should be sufficient to set Core Audio output at 48 kHz. Are you listening to a lot of DVD soundtracks? Most audio is 44.1/16 or 96/24.
post #10 of 27
There is some additional information on the Benchmark site, and it appears that there were some significant changes (high quality SRC) made in iTunes 7.0 that have affected the recommended settings.

The first article, OS X Audio Playback - Setup Guide, states, "It is recommended that the word-length always be set to the highest possible value (preferably 24 bit). The sample-rate should be set to the sample-rate of the audio you are listening to."

In the subsequent article, ITunes-QuickTime for Mac - Setup Guide, it is stated, "For iTunes versions later then 7, we recommend setting the sample rate to the highest sample rate that your device is capable of."

Presumably, they mean iTunes 7 or later. This means that setting your output to 24 bit - 96 kHz, as you initially suggested, should yield the best results.

As always, trust your ears.
post #11 of 27
Quote:
Originally Posted by Jaska View Post
Also, make sure the output volume in the Audio MIDI setup is always set to 100% for the best S/N ratio.
post #12 of 27
unless you are listening with headphones via the duet, at which point 100% would make your brain jelly.
post #13 of 27
Quote:
Originally Posted by grawk View Post
unless you are listening with headphones via the duet, at which point 100% would make your brain jelly.
The output from the computer into the DAC should be set at 100%. The attenuation of the signal to the headphones can then be controlled with the volume control on the Duet.
post #14 of 27
Do you actually have a duet? The knob and the volume control in audio-midi setup controls the same thing. Turn the knob while it's open, and watch the number change.
post #15 of 27
Quote:
Originally Posted by grawk View Post
Do you actually have a duet? The knob and the volume control in audio-midi setup controls the same thing. Turn the knob while it's open, and watch the number change.
Interesting. This means that the Duet is attenuating the digital signal before it reaches the DAC. That's bad, but I guess they can get away with it because it's a 24-bit DAC.
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