The most beautiful mass produced valve?

[Alan Stepney]

The "R" type in its many variants, or the French "TM" (basically the same thing), has much going for it.

Simple, symetrical, and functional, they worked well for many years.

[murphymad]

Well you can have beautiful in appearance or you could go for beautiful in design and function.

For appearance the pre-war valves made by the 362 Company with the vertical honeycombed anode structures are a joy to behold.
They are usually of larger construction than other manufacturers but are still domestic radio valves. We had a few in BVWS auctions recently, but I never obtained any for myself.

For sheer beauty of function it has to go to the very little known Hivac A15.

This valve was first reported in Wireless World in 1936 and then later seen in 1939.
It is a very special valve that has five separate grids as well as being indirectly heated.
It can be used in "any" stage of a receiver depending on the way it is configured.
Gambrell made a radio that contained the A15 in every stage except the rectifier.
A remarkable universal valve.

So why did it not catch on?

There will be an article in the BVWS Bulletin next year about this valve and the radio it was used in which is in the Dulwich Museum collection.

Has anyone else had experience of this valve. Do you have one ?

Mike...

[Herald1360]

Pretty ordinary pentodes like EF91 or 6K7 can be used in all stages of a receiver too, though you would need an extra one for the LO rather than having a pentagrid mixer. Ultimately I suspect better performance at lower cost would be the reason it never caught on commercially.

If minimum spares stock is important, though, that can change the balance- as in some of the German WW2 designs.

[G6Tanuki]

Were Hivac part of the BVA "Mafia" when they invented the A15? If not, then as an upstart producer I suspect the rest of the BVA would have lobbied radio-manufacturers hard against the widespread adoption of a Hivac valve.

Were there other disadvantages? The ads I can find for the A15 show the electrode-spacing to be rather large, which would have been a major disadvantage for short-wave/VHF use.

Also, from memory Hivac were always much more focussed on the specialist/niche-market rather than mass-production. Could they have handled an order for, say, 250,000 valves a month?

Further musings on Hivac's A15:

Seems that it had a rather odd heater: 15v at 300mA.

Making it entirely ineligible for car-radio applications, a significant pain-in-the-bum for series-heater AC/DC duty irrespective of whether you wanted to feed it from 115 or 230V supplies, and needing a non-standard LT transformer if you were a dyed-in-the-wool parallel-heater AC-only designer.

Why design round this oddball from a 'boutique' manufacturer ??

[G6Tanuki]

If confining ourselves to 'mass-produced' valves I really want to nominate the 6AL5 [EB91] double-diode.

Why?

Well, it's a wonderfully-unobtrusive workhorse: AM detector-and-AGC in plenty of 1950s/1960s communications-receivers, symmetric noise-limiter in thousands of first-generation AM two-way VHF mobile radios, detector/clamp/gate in millions of immediately-post-WWII UK TV sets with "automatic brightness control".

Small, unobtrusive, but essential. To me that's 'beautiful'.

[Michael.N.]

I'm more of a simple, understated type myself. I always liked the straight glass GZ34 and the ubiquitous ECC81/82/83 - nice amount of light for their diminutive size.
For some reason I've never been too fond of valves with top caps but the vast majority of valves have a nice aesthetic.

[Heatercathodeshort]

I promised to post pictures of the Cossor SU2150A [mains derived] EHT rectifier. Cossor designed and produced their own valves. It would have been too easy to just place a simple anode tube suitably spaced from the heater/cathode assembly such as can be seen in the very reliable but somewhat crude Mullard HVR2.
Cossor designed this work of art that was employed in early scopes and first generation television receivers. It is known as the 'saddle anode' rectifier.
It has a 2v heater that is designed to heat the cathode slowly so as to allow the timebase valves to be fully heated before EHT is applied. This was to prevent screen burns that would have occurred had the EHT been present before the timebases came into operation.
Early versions were balloon shaped with the classic Cossor screw bakelite top cap. I have one somewhere....
The final version was the Octal based SU25, the Cossor EHT rectifier that will be found in receivers just before the flyback era.
A lot of art for your 17/6d plus purchase tax.
Imagine the designs we may have enjoyed if Clarice Cliff had worked at Cossor!
Regards, John.

[mark pirate]

I have no personal favorite valve, But love the large 'coke bottle' shape valves from the 30's & 40's.
I am building a power amp using four 6L6 output bottles, and yes they will be on prominent display

Mark

[SaucepanRadio]

This is a response to Mike at Murphymad( 16 sept 2014) I really appreciate the note on the HIVAC A15 valve. I recently collected a large tombstone radio with round dial. It looked like a Ferguson. Could not find any labels and removed the chassis and the dial read Phillips Denbigh PTY Ltd, Wynberg Cape Province. It is employes 5 x A15 valves across the set and a UU120/500 rectifier. The 5 x A15 valves in one circuit was a new discovery for me. The chassis is amazing. It has different boxed compartments. What a lovely valve with a top cap. I further discovered in talking to some of the older radio collectors in Cape Town that Phillips Denbigh was one of the local manufactures who produced quite a bit of transmitters for the War effort, they also built amplifiers, radios and services the military in South Africa. I'm keen to know more about the A15 valve and the circuit and radio referred to by Mike.