DAC A/B Test Procedure Question?

Hey, all.

I'm trying to set up an A/B test between a few DACs using my preamp and I wonder if there is anything wrong with my procedure.

Right now I have the DACs set up like this:

• DAC A (which IS a renderer) plays FLAC files off my NAS. DAC A has digital outs. DAC A is connected to input 1 of the preamp with a balanced connection.

• DAC B (which IS NOT a renderer) is connected to DAC A via coax to DAC A's digital outs. DAC B is connected to input 2 of the preamp with a balanced connection.

• The preamp is connected to an amp via its balanced outputs.

Assume for the sake of argument that both DAC A and DAC B output at the exact same volume.

Is this a valid way to A/B test these DACs?

Is there any reason to believe that using DAC A to play files and output a digital signal to DAC B will effect or color DAC B's performance?

 

Well, I'll have to borrow a second laptop then and connect both via USB and try and sync the tracks.

 

As I said above, assume volumes are perfectly matched for the sake of argument.

 

If this is Bifrost Multibit by chance, measure it, seriously up until 0.1dB both me and @paranoidroid were able to find the differences with long periods of listening. Out of the box it seems to be 0.8dB and that was clearly noticeable on my end of testing.
Sub 0.1dB was our aim at least which made the test significantly harder. On the plus side until 0.3dB counts as volume matched according to the pure objectivists... Don't ask me how to measure however, friend of mine did all that, I was just the guy with the equipment and mostly the listener haha.

Also not to discourage at all, I think it's a lot of fun, just a heads-up in what I've learned so far in my Bifrost Multibit experience.

 

He did indeed, we made sure after each session to do another measurement to verify or readjust. This test took two full days of switching around and playing around, including prolonged sighted/relaxed listening of course.

 

The exact volume matching will come. I'm try trying to make sure I have an apples-to-apples comparison with the DACs first.

Now that I have a preamp that can switch inputs nearly instantly I want to see if I can (poorly) recreate the experience blind-testing DACs as part of Tyll's big sound project.

Getting two DACs synced up perfectly on equal footing is step one. Matching volumes will be step two.

 

Ha!

It isn't passive. The active vs. passive pre is a discussion best had elsewhere.

I'm not really interested in universal truths about DACs here. More how they play in my particular setup.

The preamp (Pass XP-10) is going to be driving power amps. It is going to be the center of my setup whether it kills resolution or not.

 

Well, I've been listening to both DACs connected via USB (eliminating the problem of using one as a renderer) and... well... next time I see the bay area SBAF group I'm going to have to let you guys take the challenge.

I don't want to say anything more than I'm back in the "DACs sound mostly the same" camp until I hear otherwise.

Being able to instantly A/B really is incredible.

I also heard essentially zero difference driving the DACs via USB vs using one as a renderer to play files to the other though I wasn't able to do the same kind of instant A/B testing on this.