At some point @MJ2 will add some kind of uprated power supply for an extra 50V and blow the fucker to smithereens.
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Cos Kevin’s reading it in the manufacturers manual and both types are stenciled next to the valve base, and started my post with ‘Depending on the circuit …’
Should you decide to keep the Copland and are tempted to play around with output Valvage I would recommend staying away from the NOS ( unless from a reputable source) or used Vintage valve minefield where a potentially expensive mistake lurks…
A couple of safe suggestions for your consideration:
Original pre-2000 Svetlana Winged =C= 34’s
Manufactured by JSC Svetlana in their St Petersberg plant.
These valves were manufactured between 1999 and 2000 and have the original S logo with the production date on the valve.
A Very nice organic fully textured sound throughout the audio range, lovely mids…ever so slightly softening at the top end…
Slightly Left field:
New Sensor Corps re-issue of the Original Genalex Gold Lion KT77
Drop in EL34 replacement with no re- biasing req.
A different presentation to the classic EL34 sound…something of a hybrid EL34/6L6 which you may prefer.
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Those genelex KT77s are fantastic valves.
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Would they work in any el34 circuit? I’m pretty sure my amps have the original mullards so they are even older than me. I have a spare set of valves but they were gifted and I don’t know their provenance.
Yes electrically interchangeable…If as it sounds like your amp hasn’t been serviced for a while checking for bias resister drift would be recommended.
And not ridiculously spendy…
If I decide to keep the amp, I will probably go with these.
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I’ve had a few TAD tubes direct from the company - good company to deal with if you have any issues with the tubes 
These are actually rather good. Do bass better than any other EL-34 that I have heard.
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@MJ2
Not 100% identical but measure close anough to be regarded as a tested pair Mullard CV491’s = 12AU7/ECC82 15 mill ladder anodes mid 70’s Blackburn production
Thanks for that Roger but, tbh, I can’t even find a definitive answer for the amp’s signal valve complement, so I don’t want to buy valves without even knowing what I actually need.
Have you tried asking Copland?
Their UK distributor is Absolute Sounds: (0)20 89713909
They are quite well matched to one another, but they’re not brilliantly well matched internally. Whether that matters or not depends on the circuit. An ECC82 is the sort of valve you might deploy before the power valves if they’re a bit insensitive (EL34s aren’t insensitive though …). One of the 82’s triodes would drive one '34 and the other the other. If the two '34s had different transconductances then you might use the difference between the two halves of the '82 to compensate for that, and the asymmetry in the '82 would then be a useful feature. If your '34s are well matched though then you’d want your '82 to be well matched too. All this only applies if you don’t like distortion, of course. If you do like distortion then an unbalanced amp will suit you better.
VB
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I think David Coe, Jaucho/AD Audio on this and other forums has serviced a few of these. Might be worth dropping him a message I suspect he will know the answer/be very helpful.
Already tried, thanks Rob.
Cheers Paul, I’ll give him a try.
I had to read twice and wondered you were pisstaking and since there is also an orifice that is spelled with ‘tt’, I got confused.
A comma would have been helpful, but at least I could laugh at myself. 