We just try one unit yesterday and the only thing we can say this unit sounds amazing, very vintage, very NEVE sound like.
Smooth character, the top end is not so bright (for me that is one of the vintage sign you might expect) and off course a very strong character in the mid lows that give the 1073/500 that NEVE like sound.
We do not have 1073 vintage unit to compare with, but we have one NEVE 1073 LB, for us the LB es quite plastic and more artificial particularly in the top end, the mid lows are very similar in both units, in mid section the 1073/500 have an edge the we miss in the LB.
On the Eq side we have made the comparison with our Pultec EQP1 and Electrodyne 709, we know that those are shelving units but what we were looking for is the color instead of performance.
Having said that, we can assure that the worst thing we can say about Eq section in the 1073/500 is the high section is not so brilliant and maybe a little bit harsh if you push too much compared to the other vintage units, but in the mid and low section man this unit have a loooot of guts, we love the 3.2 K area it make a killer boost for guitars that I am eager to use in the coming future.
The 35 Hz freq boost man, that is beefy and we love it good for adding subtle bass to any source.
After finish our test we decide to sell our LB in order to get the money to buy one 1073/500, this guys had made such a great job here, we are looking forward to try the other stuff this guys builds.
btw sorry about my poor English, it is difficult to explain feelings, perception and opinions in a language that is not yours.
In short the Heritage Audio 1073/500 is a piece to be considered when you decide to get a new serious preamp.