Measuring noise floor of 4 volt DAC vs 5 volt on the same amplifier

[dunring]

Has anyone seen a test or done one using the 4 volt output of a DAC compared to 5 volt mode on the same amplifier to see if it has a measurable effect on noise floor? On ASR they do the 50mv test to simulate really sensitive IEMs to measure how quiet the amplifier is, but it's always done at 2/4 volts to keep a level playing field. Was wondering if anyone with test equipment has done a 4/5 volt comparison to see if/how much this affects it. I've been searching, but all tests were either done with just one setting.
I currently use for a daily driver an SMSL DL200 and just got in a Sabaj A20h which had a A20D 5 volt 9038Pro matching DAC, but those haven't been available for years. ASR did measurements, but just in 4 volt on everything. Using the 5 volt output of the DL200 I think this combination sounds great using an optical USB cable. I've had amps like the SMSL SP200 which measures about the same in the 50mv test for how quiet it is, about the same as the A20H measured for it. I just think this is more quiet than any SP200 I've had, even with 18ohm IEMs it sounds fantastic. Has anyone measured 4 vs 5 volts to see how it effects noise floor?

 

[castleofargh]

No, you're welcome. ^_^

Most of my DACs have better specs than my now old and then cheap ADC, so even adjusting the input gain as best as possible, I tend to basically end up measuring my ADC.
But just as an uneducated guess, I always assumed that beside some possible clipping horror, the best results were at full scale signal because for modern DACs(delta sigma) SNR and dynamic tend to be the same thing.
Thinking about it differently, if you make a DAC go to 5V but 2volt has clearly better specs, wouldn't you sell the now capped at 2volt DAC? ^_^ I don't see the rationale for a louder DAC if not to increase the SNR. Perhaps I'm missing something obvious here?

 

[gregorio]

On ASR they do the 50mv test to simulate really sensitive IEMs to measure how quiet the amplifier is, but it's always done at 2/4 volts to keep a level playing field.

Sure, it’s to keep a level playing field but that’s because there’s no consumer standard, so from one component to the next there could be obvious audible differences simply based on the fact that that one could be louder than another. This was never much of an issue in the pro-audio world because we do have a standard, +4dBu = 0dBVU (line level), while consumer line level is supposed to be -10dBv but unlike in the pro-audio world relatively few stick to it. Presumably because consumers don’t measure and calibrate their systems as pro’s need to and so never realise that something might sound better than something else purely because of a different/higher output level. I assume ASR picked 2 and 4 volts as a very rough equivalent to consumer and pro line levels respectively. It therefore wouldn’t make much sense to compare with a voltage (5v) that doesn’t relate to either consumer or pro line levels and AFAIK, no one has.

G