How much does tube brand REALLY affect sound in terms of rectifier tubes?

There are lots of things we can't understand , don't let the "facts"  trump 
 your ears .

There are a few companies now manufacturing tubes, that have tried to produce valves, copying the internal construction/design parameters of some of the most popular, from decades back. Mainly, what they’ve succeeded in duplicating(capitalizing on) is the marque only(ie: Telefunken/Mullard/Gold Lion/Tung Sol), as none genuinely perform like the originals. The time involved in hand construction, attention to detail and(in many cases) materials used, are no longer either profitable or(perhaps) available.Try some authentic, older, well reviewed valves(as mentioned above). Worst that can happen is you’ll have to turn them, should they not turn you on. It may cost a few bucks to experiment, but- what doesn’t, in the audio affliction/addiction? Our, "rewards" are SO subjective! Happy listening!

brf 5-2-2017
...if a rectifier is providing more than adequate DC current demand, how can a different brand of tube sound different if the DC electrical parameters are identical?

The short answer is that they are not identical.

Most tube characteristics are specified as nominal or typical values, without a +/- tolerance or max/min specification. (The main exception to that being what are referred to as "absolute maximum ratings," which define the maximum amounts of voltage, current, and power the tube is rated to handle without the likelihood of damage or a significant reduction in longevity). And even in cases where a +/- tolerance may be specified for a given parameter, it will rarely be a narrow one.

So significant variations in electrical parameters can be expected among tubes of the same type that have been produced by different manufacturers, and/or in different eras.

Regarding rectifiers specifically, my suspicion is that what is likely to be the main contributor to sonic differences in many applications is simply differences in the voltage drop across the tube, resulting in differences in the DC voltage that is applied to the circuits the rectifier is powering, especially the tubes that may be in those circuits, resulting in those tubes operating at different points on the curves which define their operating characteristics.

Regards,
-- Al
 

Seems someone could manufacture a low impedance/low voltage drop valve rectifier(now), that provided sonics at least as good, as those made over three decades ago. The cost of even the best, most desirable, NOS rectifiers would drop like a rock.

I use new production Gold Lion 12AU7s in my preamp sourced from Cryoset.  They sound great and last a long time.  I was looking to use Gold Lion GZ34 / U77 Genalex Cryo Rectifier tubes from Cryoset in my 9.0 Modwright power supply when the time comes. 

Any opinions on that choice?