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Listening test setup question: Comparing DACS

Hello;

I'm either failing at search (very possible) or this question hasn't been asked before (unlikely?) but:
What is the correct way to setup two DACs or two amplifiers for a listening test with one pair of headphones?

Is this possible? I can see some potential issues with it, but I feel like there has to be a way. Or, is it simply better to switch the headphones or have two of the same model of headphones?

I feel like the only way to get a proper comparison would be to have some way to be able to instantly switch between two DACs or amps without knowing which one was in use- I can see how to do that with a relatively simple RCA switcher for DAC into Amp, but switching between Amps doesn't seem so easy! (Hm, output from dac duplicated to both amps, then run the headphone outs into an RCA switcher, I suppose?)

That leaves me with- ok, so I've got A and B, how do I get X?

Re: Listening test setup question: Comparing DACS

Reply #1
Hello;

I'm either failing at search (very possible) or this question hasn't been asked before (unlikely?) but:
What is the correct way to setup two DACs or two amplifiers for a listening test with one pair of headphones?

(1) Drive the units under test with the same source so that they are in synch. Ensure that their latency performance is close enough to each other that the outputs are in synch within a millisecond or two.  Ensure that their analog outputs have the same voltage within +/- 0.1 dB.

There are a number of ways to compare DACs.  One approach requires a special ABX switcher such as this one:

http://avahifi.com/index.php?option=com_content&view=article&id=271&Itemid=259

The ABX switcher handles the problems of randomizing the switching and keeping its details from the listener.  If the DACs have volume controls use them to match the output of the DACs. If then don't,  there are external volume controls with good enough precision and resolution to get acceptable level matching.

(2) If you have a  high quality ADC you can avoid having any other special hardware. Use it to rerecord the output of the two DACs, one at a time. Use audio editing software such as Audacity (freeware) to match the levels and timing of the two recordings, and compare them using a software ABX switcher such as FOOBAR2000 with the ABX plugin.



Re: Listening test setup question: Comparing DACS

Reply #2
Thanks!

I didn't think about using an ADC. I have a Focusrite Scarlett 2i2, that should work well! I can level match in Audition and I suppose I can also use some of the plugins to do comparisons there as well.

Re: Listening test setup question: Comparing DACS

Reply #3
Thanks!

I didn't think about using an ADC. I have a Focusrite Scarlett 2i2, that should work well! I can level match in Audition and I suppose I can also use some of the plugins to do comparisons there as well.

I also have a Focusrite Scarlett 2i2 (among others) that I've tested in the past with the Audio Rightmark program.  My recollection is that it tested to be entirely suitable for what you are trying to do.

 Good luck, and keep us informed about your progress.

Re: Listening test setup question: Comparing DACS

Reply #4
Thanks!

I didn't think about using an ADC. I have a Focusrite Scarlett 2i2, that should work well! I can level match in Audition and I suppose I can also use some of the plugins to do comparisons there as well.

I also have a Focusrite Scarlett 2i2 (among others) that I've tested in the past with the Audio Rightmark program.  My recollection is that it tested to be entirely suitable for what you are trying to do.

 Good luck, and keep us informed about your progress.

Thanks! I actually compared 5 lower-cost 2-channel ADC's for my own use and found it to have the lowest noise floor, even though it doesn't record as high as some of the other options. Maybe I should write that up- I didn't take photos but I do still have the recordings of the tests.

Re: Listening test setup question: Comparing DACS

Reply #5
Quote
and found it to have the lowest noise floor, even though it doesn't record as high as some of the other options.
Remember to level-match after recording.     When you boost to match the other DACs, of course the noise floor will increase along with everything else.   It's possible that your current DAC has a superior signal-to-noise ratio, but you have to level-match if you want to compare.

Re: Listening test setup question: Comparing DACS

Reply #6
Quote
and found it to have the lowest noise floor, even though it doesn't record as high as some of the other options.
Remember to level-match after recording.     When you boost to match the other DACs, of course the noise floor will increase along with everything else.   It's possible that your current DAC has a superior signal-to-noise ratio, but you have to level-match if you want to compare.

An absolutely critical point that bears repeating. Without close level matching an alleged listening test is so much garbage.


 
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