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Comparing DACs with inexplicable results

post #1 of 2
Thread Starter 

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

 

PS: The emphasis on the ODAC/O2 was enough to motivate me into finding a complimentary amp. Perhaps a tube amp.


Edited by r010159 - 5/28/14 at 9:39pm
post #2 of 2

With all due respect mate the problem with answering queries such as yours is that we might not hear the same effect as you report.

 

If you are serious about this what I suggest you do is re-record the output from both DACs using your best available tools. Time and level match the files and then post them up so we can download and listen on a suitable blind comparator such as foobar AB/X component. Keep a careful note of which is which but don't tell us immediately.

 

I find it hard to credit that those 2 very highly regarded interfaces differ in their output to such a degree if they are both in good working order.

 

Should there be an audible difference the first place to look would be at the differing output impedance figures for the headphone amp sections. The O2 famously has a very low output impedance, close to zero in fact. This will drive virtually anything.  The duet, designed for professional use with studio grade headphones of 250 Ohms and above, has an output impedance of 30 Ohms or greater.

 

So depending on your headphones, which you do not specify, it's possible you are getting a frequency response error.

 

This is of course all wild speculation until you provide more evidence.

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