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Comparing two DAC/amps with inexplicable results


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I need help figuring this out. I have been comparing the O2/ODAC to the Apogee Duet 2. The Apogee is obviously the more expensive DAC that is also used by mobile professionals. Apogee converters (DAC and ADC) are legendary in the high pro end. So I expected a significant difference between the two. I did get this result. But there have been a couple of surprises.

 

The Apogee DAC has also a headphone amp section. The Apogee representative told me the sound would be close between the headphone out and the line out, the line out being the better SQ. So I played the same music through the headphone out of both DACs. I first discovered that the soundstage of the Duet has much more depth. There was more of an analog coloration to the sound. Some higher frequency sounds were clearer like that of a cymbal. The ODAC/O2 on the other hand seemed to be brighter. This does not make sense if when I looked at the FR graphs of both DACs. This examination showed the Duet to have the high frequencies boosted, not the ODAC/O2.

 

Also, there were sounds that would show up more clearly with this ODAC/O2 compared to the Duet. In one case, there was a sax playing the melody and a guitar playing counterpoint. On the O2/ODAC, the counterpoint showed up clearly. On the Duet, this guitar was much more subdued and at times was almost lost in the other background instruments being played. Also a specific example of the differences is with the song "Old Time Rock and Roll" by Bob Seger. There is allot of reverb used at the start of the song. With the O2, you can hear the definite echo, but on the Duet, the echo effect is noticeably more subdued. Now this is comparing the headphone out on both DAC/amps. The line outs may tell a different story which should be the case with the Duet.

 

So what is going on here? Is this due in part to the depth of the soundstage with the Duet? Is the reverb more obvious because the ODAC/O2 appears to have higher frequencies emphasis compared with the Duet? Even though this does not make sense? I personally like the sound of the Duet better for some sounds seem to be more natural and accurate. In the comparison I am using the same Mac mini, player, audio file, headphones, and cables.

 

Isn't this a little inexplicable?

 

Bob

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It sounds to me that the Duet is better. Echo is a complicated thing, but I can certainly imagine that it could be more prominent with a bright component, i.e. more distorted in HF. The sound of a cymbal is a *very* useful test. If one is but more resolving and natural sounding, it's likely to be a superior component, full stop. And sometimes a quiet instrument will blend into the background because the others are more engaging, i.e. accurate.

 

You said that the the Apogee had "the highs boosted." Did you mean that?? (It definitely shouldn't appear except in the ultrasonic range in DSD64 playback.) Or did you mean flat or less attenuated than the O2? And whose FR graphs were they?

 

Here's a useful test: describe the images using a recording you know well which has excellent images. Compare the components, blindly if possible, for which one has images that sound glassier, harder. If the other in comparison provides a natural-sounding texture and form (not glassy) for the images, the latter component wins.

 

Another good test is what I call "reach." Match the outputs of the devices if possible, and again test blindly if you can. The component that delivers a soundfield that reaches out close to you or even past you wins. This apparent soundfield is caused, I believe, by the spontaneous creation of apparent sources (sounds) well outside, in all axes, by virtue of accurate reproduction. You hear this in live unamplified music all the time: a great stream of sounds seems to exist all the way from the performers to your face and ears, as well as above you and way to the sides.

 

A final note: a really fine system, even at merely loud levels, will enable you to feel some transients strike the skin of your forehead.

Mac Mini 2012 with 2.3 GHz i5 CPU and 16GB RAM running newest OS10.9x and Signalyst HQ Player software (occasionally JRMC), ethernet to Cisco SG100-08 GigE switch, ethernet to SOtM SMS100 Miniserver in audio room, sending via short 1/2 meter AQ Cinnamon USB to Oppo 105D, feeding balanced outputs to 2x Bel Canto S300 amps which vertically biamp ATC SCM20SL speakers, 2x Velodyne DD12+ subs. Each side is mounted vertically on 3-tiered Sound Anchor ADJ2 stands: ATC (top), amp (middle), sub (bottom), Mogami, Koala, Nordost, Mosaic cables, split at the preamp outputs with splitters. All transducers are thoroughly and lovingly time aligned for the listening position.

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You gave me good advice! The O2 is the one with distorted HF. I also found that if I go up to a 600-ohm phone, most of the problem disappears with the Apogee. I think this is because of the higher damping ratio. IMO what remains is a problem with the O2.

 

Bob

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