Blind-testing four DACs

[TheEman]

Hi everyone. Longtime reader, first-time poster, so don’t bite my head off (yet…I love a spirited scientific debate).

I want to blind-test at least 4 DACs: Schiit Modi 3+, Topping E70 Velvet, RME ADI-2 DAC fs, and an R2R DAC that measures well (open to suggestions). Given that the Schiit only has RCA out, I’ll be using RCA from every device. The WiiM will serve as the source for all DACs using USB. All 5 cables will be the same relatively inexpensive Amphenol. And from the switch to a HeadAmp CFA3 and using the Susvara as the only transducer.

Two questions:

Can the USB out from the WiiM be split four ways so that all DACs are playing at the same time? Given that audio memory is only around 7 seconds, I need to be able to switch quickly.

Is there a switcher that will allow 4 DACs to be plugged in with a single RCA out that normalizes/standardizes each input to output exactly 2.00 V? This last part, of course, is critical to a true test. I don’t know how to normalize each DAC to exactly 2.00 V, so it would be convenient if the switch did this. Would something like this work?:

https://a.co/d/ari8K2e

Apologies if this has been asked/discussed before. Also open to other ideas in how to achieve this. Really want to see if I can blindly identify these DACs.

Thanks, and happy holidays to all!

 

[Everett T]

Why would you want to test DACs after the signal has been converted to analog, seems defeated.

 

[TheEman]

Why would you want to test DACs after the signal has been converted to analog, seems defeated.

The USB out of the Wiim Ultra bypasses its internal DAC. As such, a digital, unadulterated signal is sent to each external DAC.

What I’m unsure of is how to split that digital USB out signal four ways.

Perhaps this can only be done using a desktop PC with Roon? Adjust the volume for each DAC in Roon with a steady tone so that a multimeter attached to each DAC reads 2.00 V? Not sure how to do this in Roon so that the four DACs play simultaneously…

 

[obsessive9119]

The USB out of the Wiim Ultra bypasses its internal DAC. As such, a digital, unadulterated signal is sent to each external DAC.

What I’m unsure of is how to split that digital USB out signal four ways.

Perhaps this can only be done using a desktop PC with Roon? Not sure how to do this…

One option that would make your life easier (I think) would be buying multiple WiiMs and using one per DAC. You can link them all to be playing the same thing, and you can volume control each one to level match. You’ve have to measure the DAC output manually to do this.

I’m not blind test expert, but wouldn’t you usually only test two devices at a time? All 4 at once would make tracking what’s happening pretty difficult along with making switching difficult.

 

[ahofer]

The USB out of the Wiim Ultra bypasses its internal DAC. As such, a digital, unadulterated signal is sent to each external DAC.

What I’m unsure of is how to split that digital USB out signal four ways.

Perhaps this can only be done using a desktop PC with Roon? Adjust the volume for each DAC in Roon so that a multimeter attached to each DAC reads 2.00 V? Not sure how to do this in Roon…

The easiest way would be an attenuator after the DACs or amplification, but it does add another box.

 

[TheEman]

One option that would make your life easier (I think) would be buying multiple WiiMs and using one per DAC. You can link them all to be playing the same thing, and you can volume control each one to level match. You’ve have to measure the DAC output manually to do this.

I’m not blind test expert, but wouldn’t you usually only test two devices at a time? All 4 at once would make tracking what’s happening pretty difficult along with making switching difficult.

Yeah, that’s certainly an option, but now you’ve got multiple sources, thereby adding another variable. Perhaps one WiiM Ultra sounds a bit different due to manufacturing tolerances, or something like that. Having a single source eliminates that variable.

Which is why I’m now leaning towards a single PC with four USB cables, one to each of the DACs. But I don’t know if Roon can send four simultaneous streams…

 

[obsessive9119]

Yeah, that’s certainly an option, but now you’ve got multiple sources, thereby adding another variable. Perhaps one WiiM Ultra sounds a bit different due to manufacturing tolerances, or something like that. Having a single source eliminates that variable.

Which is why I’m now leaning towards a single PC with four USB cables, one to each of the DACs. But I don’t know if Roon can send four simultaneous streams…

Do your DACs have optical in? You can buy optical splitters

 

[TheEman]

Do your DACs have optical in? You can buy optical splitters

Yes, they all have optical in.

Interesting…so WiiM optical out to the splitter then to each DAC…didn’t think of that. Would something like this work?

https://a.co/d/0COhbx7

Really like the idea, never seen optical splitters applied to audio gear. Thanks for the idea!

 

[Multicore]

I want to blind-test at least 4 DACs: Schiit Modi 3+, Topping E70 Velvet, RME ADI-2 DAC fs, and an R2R DAC

Why?

 

[TheEman]

Why?

For fun…? Yeah, I’m weird, but doesn’t everyone on this forum fit that to some extent?

To be clear, I don’t believe that competently-designed DACs will sound different, but having the blind testing is a good exercise to demonstrate this to myself.

 

[obsessive9119]

Yes, they all have optical in.

Interesting…so WiiM optical out to the splitter then to each DAC…didn’t think of that. Would something like this work?

https://a.co/d/0COhbx7

Really like the idea, never seen optical splitters applied to audio gear. Thanks for the idea!

I’ve never had a cause to use an optical splitter, so I have no idea how well they work, sorry.

 

[antcollinet]

Would something like this work?

https://a.co/d/0COhbx7

No, that is a switcher - three inputs to one ouput.

You need one input to 3 (or 4) outputs.

Something like this (though I have no idea of it's quality:

https://www.amazon.com/LiNKFOR-Splitter-1x3-Dolby-AC3-Compatible/dp/B08FX2CRR3/

EDIT : here is one with four outputs.

https://www.amazon.com/LiNKFOR-Digital-Splitter-Aluminum-Blue-Ray/dp/B07MJ4TLWQ/

 

[solderdude]

Hi everyone. Longtime reader, first-time poster, so don’t bite my head off (yet…I love a spirited scientific debate).

I want to blind-test at least 4 DACs: Schiit Modi 3+, Topping E70 Velvet, RME ADI-2 DAC fs, and an R2R DAC that measures well (open to suggestions). Given that the Schiit only has RCA out, I’ll be using RCA from every device. The WiiM will serve as the source for all DACs using USB. All 5 cables will be the same relatively inexpensive Amphenol. And from the switch to a HeadAmp CFA3 and using the Susvara as the only transducer.

Two questions:

Can the USB out from the WiiM be split four ways so that all DACs are playing at the same time? Given that audio memory is only around 7 seconds, I need to be able to switch quickly.

Is there a switcher that will allow 4 DACs to be plugged in with a single RCA out that normalizes/standardizes each input to output exactly 2.00 V? This last part, of course, is critical to a true test. I don’t know how to normalize each DAC to exactly 2.00 V, so it would be convenient if the switch did this. Would something like this work?:

https://a.co/d/ari8K2e

Apologies if this has been asked/discussed before. Also open to other ideas in how to achieve this. Really want to see if I can blindly identify these DACs.

Thanks, and happy holidays to all!

No need to split any signals nor adjust the level within 0.1dB either.

You just need to borrow one of Santa's little helpers.

Set it up like this.

Ensure all 4 DACs have the same output voltage (or very closely the same).
Have the helper connect 1 of the 4 DACs in a way you cannot see (or hear) which one he connects. Suggestion in another room.
You select the music and control the volume.

At some point you say 'switch'. The helper disconnects the DAC (after you turned down the volume).
He connects one of the 4 DACs at random, this can even be the same DAC again.
Helper makes a list (and checks it twice) of the order in which he connected the DACs.

Start playback and turn the volume up... listens, skips, adjusts volume etc and makes notes and can even guess which DAC it is.

Rinse and repeat 20 times.

Compare lists..

Come one .. make it easier for yourself and start of with 2 DACs.
Make sure the levels are (somewhat) comparable and DAC filters are comparable.
Take your time and have a relaxed listen (really important).
Span it over a few days if you must, preferably in the evening (you'll hear better).

Have fun !

 

[somebodyelse]

Can the USB out from the WiiM be split four ways so that all DACs are playing at the same time?

No. The protocol doesn't work like that. You could use linux (on a Pi or something) with an ALSA composite device sending data to all the DACs at the same time, and with a short test signal the clock differences won't be enough for them to drift appreciably.

 

[obsessive9119]

No need to split any signals.

You just need to borrow one of Santa's little helpers.

Set it up like this.

Ensure all 4 DACs have the same output voltage (or very closely the same).
Have the helper connect 1 of the 4 DACs in a way you cannot see which one he connects. Suggestion in another room.
You select the music and control the volume.

At some point you say 'switch'. The helper disconnects the DAC (after you turned down the volume).
He connects one of the 4 DACs at random, this can even be the same DAC again.
Helper makes a list (and checks it twice) of the order in which he connected the DACs.

starts playback and turns the volume up... listens and makes notes and can even guess which DAC it is.

Rinse and repeat 20 times.

Compare lists..

Come one .. make it easier for yourself and start of with w DACs.
Make sure the levels are comparable and DAC filters are comparable.

Have fun !

It’s useful to be able to switch instantly though, if possible. Plus, if the OP is anything like me they won’t have any friends stupid enough to volunteer

 

[solderdude]

While useful it is very problematic as DAC's may have different filter types and digital processing which will create small timing differences which can result in a 'tell'.

When doing direct switching both channels have to be with 0.1dB, must not have timing differences and you will at least have an ABX tester of sorts.
Also differences as small as can be expected are impossible to tell which is extremely exhausting because one is really stressing perception.

 

[Everett T]

The USB out of the Wiim Ultra bypasses its internal DAC. As such, a digital, unadulterated signal is sent to each external DAC.

What I’m unsure of is how to split that digital USB out signal four ways.

Perhaps this can only be done using a desktop PC with Roon? Adjust the volume for each DAC in Roon with a steady tone so that a multimeter attached to each DAC reads 2.00 V? Not sure how to do this in Roon so that the four DACs play simultaneously…

I misunderstood, I thought you were going analog out and then splitting.

 

[TheEman]

No need to split any signals nor adjust the level within 0.1dB either.

You just need to borrow one of Santa's little helpers.

Set it up like this.

Ensure all 4 DACs have the same output voltage (or very closely the same).
Have the helper connect 1 of the 4 DACs in a way you cannot see (or hear) which one he connects. Suggestion in another room.
You select the music and control the volume.

At some point you say 'switch'. The helper disconnects the DAC (after you turned down the volume).
He connects one of the 4 DACs at random, this can even be the same DAC again.
Helper makes a list (and checks it twice) of the order in which he connected the DACs.

Start playback and turn the volume up... listens, skips, adjusts volume etc and makes notes and can even guess which DAC it is.

Rinse and repeat 20 times.

Compare lists..

Come one .. make it easier for yourself and start of with 2 DACs.
Make sure the levels are (somewhat) comparable and DAC filters are comparable.
Take your time and have a relaxed listen (really important).
Span it over a few days if you must, preferably in the evening (you'll hear better).

Have fun !

Haha. Yeah, it’s a good idea. Actually did this with amps. But with DACs, I wanted the ability to switch instantly to potentially hear the small differences. If they are there.

Actually thinking of redesigning this test and having:
Schiit Modi 3+
RME ADI-2 DAC fs
Gustard R30
Chord DAVE

Two delta-sigma DACs, one R2R and an FPGA. I think this test would be even more interesting than four delta-sigma DACs…

 

[TheEman]

While useful it is very problematic as DAC's may have different filter types and digital processing which will create small timing differences which can result in a 'tell'.

When doing direct switching both channels have to be with 0.1dB, must not have timing differences and you will at least have an ABX tester of sorts.
Also differences as small as can be expected are impossible to tell which is extremely exhausting because one is really stressing perception.

I’m quickly realizing this is going to be a much more difficult setup than I previously imagined. And yes, I didn't think of the different filters. Which is probably why you don’t see many people doing this kind of test… And certainly not with a high level of rigor

 

[TheEman]

At this point, probably just going to try solderdude’s idea of having a helper. Go to another part of the house, wait a given time while the switching occurs, enter the room blindfolded, sit facing away from the equipment, listen, repeat.