Lumin U2 mini vs Mac laptop sound test

@johnah5 

I was thinking about this a little more after reading your latest posts and I’m wondering if a change in how these “streams” are attenuated might help in discerning any differences between the devices you’re using.

You mentioned before that you were controlling volume from within the Tidal app. This seems counterintuitive to me as I’ve always adjusted volume within software to its maximum and used my preamp to attenuate the final output.

In reading through the manual of your dac/pre I also noticed there are dip switches that allow you to set the “Director” to Unity Gain. I would suggest trying this setting if you find it more convenient to use the volume control within Tidal. The problem with this is that you’re completely relying on the software/circuits of your Mac Air for processing the volume into the Director (via USB). In the case of the Lumin you’ll be balancing the output between its internal LEEDH processing and the values dictated within the Tidal app.

For me- I would prefer using the Director as it was designed to be used allowing the AKM chip and the preamp to control all. That should take away any variables seen between software/hardware. I would recommend trying the following setups for your listening tests (hopefully I understand the signal chain enough to not introduce other problems).

SPL Director- Leave the dip switches on RCA/XLR in the OFF position so that the Director controls the volume output.

Mac Air- within the Tidal app set the volume to 100%. In system settings select your USB output to see the Director as the device and set the volume to 0.0 dB (100%). Connect via USB to the Director.

Lumin U2 Mini- Connect the Lumin to the Director via AES. Within the Lumin configuration settings adjust the volume control to 100% and within the LEEDH tab select OFF. Adjust all of your upsampling modes to the native rates supported by the AKM chip within the Director (see manual). 
With these settings the volume of Tidal may vary when switching inputs from AES to USB- this is a “tell” that demonstrates the attenuation differences between devices. You should be able to level match each fairly well with a dB meter app. If your Director holds the volume level from each input while switching you can quickly match the levels and get back to comparing each device/signal path on its own merit.

@johnah5  Is the Lumin broken in? It should take 400-500 hours to settle in. For reals.

@designsfx 

I never said I was using Tidal for volume control. There was a volume diff that I was able to fix but turning on a setting in Tidal that allows it to control but volume has been and always is controlled by the Director preamp.  Leedh is also off on the Lumin and again the director adjusts the volume

I verified sound levels with a DB meter. 

JH

@yage 

Yes I agree but I listened to the owner of Antipodes interviewed on Darko podcast and he explained that the packets are always sent complete and any incomplete/corruption is erased as the system re-sends the packets.  He said the crucial part of data is the timing information for playback.  He said noise from a computer etc will cause timing issues and smearing of the square wave which I think is from jitter. Anyway he makes a very good argument on why a streamer would matter so I was shocked to not hear an absolute night and day difference!

JH

Whoever you listened to on the Darko podcast was mistaken. Audio over USB is an isochronous transfer. This means that if bit errors are detected, the packet is dropped and not retransmitted. In this case you will hear dropouts, stuttering or pops during playback, not unlike this example - https://archimago.blogspot.com/2014/01/demo-measurements-what-does-bad-usb-or.html. Perhaps the person was conflating transferring audio over a network with a protocol like TCP/IP. In that case, TCP will guarantee reliable data transmission and resend lost or mangled packets.

There is virtually no jitter on an asynchronous USB connection (which is what most DACs use nowadays). The data is buffered and clocked back out by the receiver. Note that in the previous link, although you can hear the errors, the jitter plots appear very similar. 

So what does jitter actually sound like? Here is a great website that has audio clips with varying amounts of induced jitter. Have a listen with you and your friend. See if what you hear matches what the audiophile conventional wisdom attributes to 'timing issues' - https://www.sereneaudio.com/blog/what-does-jitter-sound-like