Allegedly, the best valves to use in my Aqua DAC are early 1950’s (not late 1950’s) Mullard ECC81.
Being a valve novice, I wouldn’t have a clue hw to determine what is genuine etc. on eBay or other. Could someone advice on a reliable source?
Appreciate that these probably aren’t cheap, but are said to be a worthwhile investment for the Aqua DAC, so I’ll give it a go.
For the exotic stuff I have used these
Brendan is a decent guy to deal with, I had an issue with an expensive valve from them and he got it sorted for me, that is a big plus in my book!
Being an American site they probably have ECC81 listed as 12AT7
Also check equivalants CV10662, CV455, CV8154, CV9859
I’ve found this site quite useful:
Just been chatting to a helpful guy at Watford Valves, they have some from 1980’s for a decent price. His view was the 1950’s would be hard to come by and likely noisy.
They probably are hard to come by, but why would they be noisy?
A NOS valve in a perfect vacuum is the same as it was made, they don’t really deteriorate and the 50s was probably the height of valve manufacturing knowledge and quality control as they were making and testing so many.
What he probably meant was that he hasn’t got any to sell you.
There are sometimes issues with NOS vintage valves in that the reason they weren’t sold/used at the time was because they were a bit noisy. They could go back in their boxes then and end up for sale at a premium price some 60-70 years later. It’s not always the case but it has happened.
Those mullards will be nice but go crazy 
did you buy them?
No but some other ducker beat me to it!
A lot of the NOS stuff that shows-up in the hands of the usual vendors (e.g. Langrex) was likely put aside after testing when it was new for just those reasons - certainly been my experience of NOS mil-spec stuff. I’d guess military stores just bought bulk and individual valves wouldn’t be tested until they were needed for servicing. Good chance that working-but-time-expired valves removed from equipment also found their way back into the food chain back in the day.
I’ve bought a fair bit from Langrex over the years, and usually buy at least twice as many valves as I need, test them, keep the best/working examples and send the rest back for refund. They’re pretty easy to deal with.
[sorry Guy, this was mostly for OP]
I read that the Mullard cv4024 is cheap because the MOD placed orders for 10’s of thousands in the late 70’s to help keep Mullard afloat and producing valves for them.
You probably know already that there are now masses of brand-new “Mullard” branded tubes on the market - all made in Russia, all not meaningfully different from all the other brands coming from the same factory. If circumstances force you to buy Russian, the gold-pin Electro-Harmonix are reliable and sound OK. I’ve found ‘Tube Amp Doctor’ in Germany to be extremely reliable and helpful suppliers of modern valves.
I also recall using Mullard M8162s in my old power amp - they’re a ruggedised ECC81, and 15 years ago were a fair bit cheaper than vintage Mullard ECC81.
Obviously Telefunken’s various offerings are also at least as good as Mullard, but they are also even more expensive, and prone to being faked or misrepresented…
That sounds right. I did try them in the distant past, and they were underwhelming - but that said they’re still likely better than most of the modern stuff!
Another thought for OP - modern production tubes often seem to have undersized/skinny pins: can be a bastard to get good contacts on the cheap nasty-ass Chinese valve bases so many manufacturers use. Best thing I did to my pre was fitting some decent valve bases!
Of the modern production miniature triodes I like the JJ ECC803, ECC802, ECC801 and E88CC Gold Pin versions. These seem pretty consistent & sound ok.
Where do you go for these, Paul?
I think I’ve probably got a few to change in the AI gear, some bolted and some PCB mounted.
I’ve got a couple of the JJ ecc802s and they sound really good, excellent bass and sound a bit cleaner than other ecc82
Hotrox in the UK are quicker deliveries and less risk of getting screwed on VAT, they also sell the TAD badged ones (the TAD EL84 is a stonker)
All true, but I had a couple of properly cunty encounters with them - never again. Never been caught for duties from TAD so far.
CMC are little works of art, but no good for PCBs - for those, Belton are really nice. I think Hifi Collective have both.
Back up and cheaper
Had a dim’n’distant recollection (I have no other kind, TBH) that the Beard P35 I had used a pair of ECC81s, so just had a rummage through my drawers (wahey!), and found two pairs of 1960s (at a guess) Mullard ECC81s and two pairs of Mullard M8162s (electrically identical, ruggedised), as well as a pair of Bentley ECC81 (it was implied at the time these came from one of the Mullard factories, but this is not just untrue, it seems Mullard actually took out a court order in 1960 to stop Bentley’s trademark infringements! Some things never change!).
I’ve got a couple of other singletons, but I’m assuming you need a pair?
You’d be welcome to give this lot a no-obligations whirl if we can get them to you without resorting to the tender mercies of our overpriced postal system.
As a general point, it pays to try various valves in any critical application as what others rate as “best” is pure subjectivity, and you may well prefer a quite different sound.