@invalid You must have read my post wrong, I acknowledged that the nos mullard’s are not drop in replacements, but the shuguang CV 181’s are, as they are not the same as the Mullard cv181’s. I have no idea why shuguang labeled them this way.
OK, I’ll make bold the bit that seems to be invisible. 900mA is 50% more current draw than a 6SN7. This is known and accepted, and poses a risk to your amplifier. edit - of course, ask your amp manufacturer if CV181z are compatible with it. If so, all is well - this may very well be the situation.
So -
One - The Shung tubes are clearly marked as CV181z. This is not in doubt.
Two - Being a reviewer and something of a shill, I trust that he had access to the spec sheet. Evidence of this is that he rates the CV181z as 900mA, not 950mA which is the Mullard specs. He is not merely guessing.
Three - He also repeats words to this effect elsewhere and also in a follow up review some years later, so its no typo.
Four - that the CV181z does sound better (brighter, more lively etc) than any 6SN7 is corroborative evidence that it is rated higher. An EE may be able to confirm this.
So people, unless you have evidence to the contrary which I will happily bookmark, this stands as reference in the meantime.
Failing this, it is not a 6SN7 and it is negligent of the manufacturer to market this as a 6SN7.
This is why the CV181Z might not be a drop in replacement for the 6SN7. Typical 6SN7 heaters draw about 0.6A and the CV181z draws about 0.9A (900mA), the old Mullard CV181 drew 950mA. This 50% increase in heater current amounts to 0.6A for a pair of CV181 in a circuit, which as you can see represents the load of a whole extra double triode.