What are the oldest affordable valves you can still buy?

[Thermionic Idler]

... for audio, that is. As per the question really. I'm pondering the mono rig I want to build specifically for playing Meredith's 78's. It occurred to me that it really ought to use period-correct valves wherever possible. They don't have to be the best in the world - this thing is going to be pretty bandwidth limited because of the source.

[Nick]

Ignoring the fact that affordable is a number that only you can pick, and by "still buy" I guess that requires 1. they still exist, and 2. you can afford them.

But what do you mean by oldest? Do you mean older as in they were made a long time ago, or made more recently but were made to copy an old design.

[simon]

Yes, a lot of variables as Nick suggests. You can't go far wrong with a 45, introduced in 1929, if it has enough power? Even copies aren't particularly cheap though.

[Thermionic Idler]

Ignoring the fact that affordable is a number that only you can pick, and by "still buy" I guess that requires 1. they still exist, and 2. you can afford them.

But what do you mean by oldest? Do you mean older as in they were made a long time ago, or made more recently but were made to copy an old design.

Yes it would probably have helped if I'd defined 'old' and 'affordable' really...

In terms of the former, I'd say manufactured before 1940 ideally, as a lot of our source material is from that period. For the latter, if we expressed it using RAG indicators, the green zone goes up to about £60 per valve, amber between £60 and £90, red over £90. As it's going to be mono, we can probably allow a reasonable amount. And this is not going to be hi-fi - in fact I'm thinking it probably needs to be specifically engineered to be bandwidth-limited 'pleasing lo-fi'.

[steve s]

Mono was pre 60s and 78s just before, so just about any valve will do, most of the 40s and 50s mono radiograms I've owned have nothing special in them.
The supposedly better ones where push pull.

But 6l6, pen 45, 6v6, where the standard outputs you see usually with rather comprimised by everything else in the amp.

Mono can be brilliant, better than stereo from a technical point of view as there is only one set of info in the groove, and I've read good 78 recordings can be very good?
If you want to go back to the late 20s and 30s it's got to be SE, and an efficient corner speaker at the least !
I remember seeing a classy 1920s radiogram a few years ago, it used an energised speaker to get the efficiency and not more than a couple of watts output from the amp.

Look up mazda ac/pen, they're for nothing considering the sound quality.
And something like an mh4 or a cheaper equivalent (but equal sound quality) to drive it, then a suitable phono valve to match the pick up.

I've skipped quite a few mono corner speakers over the years... maybe I've just got carried away too, about what's possible?

[Nick]

as a lot of our source material is from that period

Just to point out that the electrons that travel through the valve are not the ones that were in the valve when you bought it after a few hours of use.

[steve s]

https://charm.rhul.ac.uk/history/p20_4_6.html

There is loads of info on the net, but this is sense too

[IslandPink]

Do you need to look into different equalisation curves ?

[Thermionic Idler]

Do you need to look into different equalisation curves ?

Yes, that’s part of it.

[RhythMick]

I use old globe DHT triodes for my builds and I have quite a boxes of Cunningham, RCA, and many others dating from 1920s, 30s. My opinion they sound great, I like the 26 for input with 71A driver and 45 output. 01A are similar to 26 with half the anode current and there are absolutely tons of them dirt cheap on fleabay, though import duties from US can be a problem. 27s are also plentiful, though IDHT. Lots of pentodes from the period around too. Cunningham Tube Manual available on t'web as PDF.

Might be heresy but maybe use SS input before the valves.

[Mike H]

as a lot of our source material is from that period

Just to point out that the electrons that travel through the valve are not the ones that were in the valve when you bought it after a few hours of use.

Chortle!

[Mike H]

But 6l6, pen 45, 6v6, where the standard outputs you see usually with rather comprimised by everything else in the amp.

I found a Mazda PEN 45 on eBay.

Vintage Mazda PEN45 Rare Grey Valve Tube Made In England Used Untested

[steve s]

I would guess the starting point would be usa or English valves, as pre 40s there where not so many American valves in this country and we in the uk had probably better audio valves before the war when you compare them( and I suppose some worse ones too ?)

Even the kt66 was made to be better than the american 6l6, without the latter's kink.

[steve s]

But 6l6, pen 45, 6v6, where the standard outputs you see usually with rather comprimised by everything else in the amp.

I found a Mazda PEN 45 on eBay.

Vintage Mazda PEN45 Rare Grey Valve Tube Made In England Used Untested

I have a few of those for the cost of the postage.