USB audible differences

I know, I’m getting into polemic and darkness but I’d really like to hear from your experience on using USB to send signal to a DAC.

Have you really heard any difference when using different usb sources?

For example, any audible and notorious difference between an Allo usbridge and simply using USB from a computer?

I’m driving a Topping D90 dac direct from a Raspberry Pi4/4GB. With the Pi4 there are no streaming issues I could find. I spent some time trying to discover any USB noise which is what a cleaner USB source might be expected to reduce. I put the 2V rated output of the DAC direct into a 200mV line input of my amplifier. I selected a 96k/24bit track with just studio background noise and set the volume on the amplifier to maximum. Nothing other than the background noise heard even with my ear close to the loudspeakers. So I concluded that an add-on like the USBBridge would not improve my setup.

The website Audio Science Review (ASR) has done a substantial number of tests with various mechanisms to clean up USB with different DACs. Summarising their work and probably over-simplifying: a good DAC gets no advantage from cleaning up the USB signal. The Allo USBBridge does reduce USB noise (unlike some other products) but really good DACs are substantially immune to modest quantities of USB noise. I believe that all of ASR’s DAC reviews are done using a standard windows laptop, without any USB cleanup, and you can see all the measurements on the DACs and choose the best performing inside your budget.

Similarly another website Archimago’s musings has made measurements and found that a raw USB output from a Raspberry Pi causes no measurable USB noise issues with good DACs.

It must be said that both websites were looking for USB noise issues with measurement methods able to resolve well below the threshold of hearing.

Set against this you will see websites like Darko Audio, Hans Beekhuyzen that praise USB noise reducing devices based on their assertion that they (the reviewers) have very good hearing and can discern differences. To the best of my knowledge these tests aren’t done blind and they know which product they are reviewing before they hear them. So there is an expectation before the listening test is done.

Look at it another way: a RPi4/4GB, power brick, SD card and FLIRC case will save approx 200 Euro compared to the USBBridge signature setup which can be put towards a better DAC

Just my take on it!