1) If there is no technical possibility to be hearable difference between GEN5 and Unison, this would be reasonable. (Or possibility of defective card - gen5 or even unison, because what i can hear with gen5 is more sharp sound (or harshness) in conparsion with clean sound with unison (or rounded edges or blur or bloom).
2) Not this kind (I know what you mean, that it is unconscious, but for example, if you buy new headphones, you just know the sound differs. ... Difference i hear with Unison is just too big as you can notice it in the first second and still lasts. It is quite a long time i buy stuff and most of the time i have no conscious expectance, often hear no difference or i am not much suprised. I am just suprised to hear such a difference because i did not expected it technically and I am really curious why would i be biased now so much with Usb card in dac and not some stuff where i can objectively expect more sound improvement (like headphones). I am looking forward to do basic listening tests to eliminate bias, i do that if i can with tubes and amps also. In this case i have only option to swap the cards fast because i have only 1 Bifrost, still doubt i have so big perception error in this case.
3) In this case volume really doesnt matter, its hearable at all levels (not subtle).
1. There is the possibility of a technical reason, if the GEN5 were defective for example. However, your description of the difference is not consistent with a defective USB interface and therefore this is extremely unlikely. Far more likely is a perception error ...
2. Human perception is complex and the vast majority of those who take audio seriously have BOTH a poor understanding of the actual facts, plus a bunch of misconceptions about it. For example, you seem to think that perception errors are only small, that if you perceive a big difference then it can't be a perception error. This is incorrect, perception errors can be anything from only just audible differences to huge differences, the difference between silence and loud hammering for example! Also:
A) Perception errors can last anything from a few moments to a lifetime and some/many perception errors are desirable or even vital, in some cases even huge ones!
B) There's typically several/numerous biases at play whenever we listen, both subconscious and conscious. The human brain factors all of these biases into it's "perception". For example, if the brain knows there's some physical difference (say a different USB interface) then subconsciously it expects to hear a difference. Having a conscious expectation of not hearing a difference may or may NOT override the brain's subconscious expectation/bias.
C) The human brain makes these decisions about biases (and therefore it's perception) on a case by case basis. For example, let's say there's a physical difference which results in no audible difference: You may have no conscious expectation of hearing a difference and on one/many occasions not perceive a difference, on other occasions, even virtually identical circumstances, you will (falsely) perceive a difference, potentially even a large difference.
3. Unfortunately, you have this backwards and therefore it could "really matter"! Volume difference perception errors can occur "at all levels", in fact there's only ONE level at which it can be ruled out, where the level of both are audibly identical (within 0.1dB). However, a USB interface cannot affect the volume level, unless it is doing something beyond being a USB interface.
A little bit old thread, but i want to add the information about my experience with upgrading my Bifrost 1 to Unison USB (from GEN5) for the people searching for some informations in this regard.
The above 3 points are why "experiences" are not valid "information" in this sub forum.
But this time it is obvious, I am not deaf.
Being deaf is irrelevant! Both the deaf and normally hearing people are subject to perception errors that result in apparently obvious differences.
G