What's the best audio output valve?

[neutronic]

At a local fair in our village I once saw a couple of output amplifiers with enormous valves.
They were labeled as Kronzilla KR T1610.

What struck me was the fact that the double triodes had their anodes/plates mounted on top of each other.
But most of all their absurd size was impressing.

A search at the the web gave this information:
With its large plate dissipation (150W), the T1610 is much bigger than the 845, the next largest triode made. The Kronzilla tube measures nearly 12" tall, over 3.5" in diameter, and weighs almost two pounds.

After hearing the price of the complete set I left the hall with some polite oh´s and ah´s.
It was somewhat over my budget.

Jard N.

[neutronic]

Originally Posted by Herald1360

Can you do UL with those things? I suppose they have some affinity with beam tetrodes in the sense that all their "grids" are beam focussing rods.

I´m sorry for this stupid question,but what is the meaning of ¨ UL ¨

Jard N.

[turretslug]

UL = Ultra-Linear. Our friend t'interweb will explain much better than I can.

[turretslug]

Originally Posted by neutronic

A search at the the web gave this information:
With its large plate dissipation (150W), the T1610 is much bigger than the 845, the next largest triode made. The Kronzilla tube measures nearly 12" tall, over 3.5" in diameter, and weighs almost two pounds.

It is most impressive- but I fear that both the cheesy moniker and the gold-plating place it outside the forum's remit

[Radio Wrangler]

Maybe those Freudian psychoanalysts do know a thing or two?

David

[cmjones01]

Originally Posted by turretslug

It is most impressive- but I fear that both the cheesy moniker and the gold-plating place it outside the forum's remit

I doubt the gold plating does anything for the performance! The T1610 looks like nothing more than a shiny version of the trusty 212E, which is the same size. Designed for audio amplification, as far as I know: we have a couple of old ones in the family which were spares for a 1kW valve amplifier. By some measure, maybe size, weight and power, they're definitely the 'best' output valves!

Chris

[barretter]

Originally Posted by GrimJosef

Assuming that that's the dominant distortion then with 26dB negative feedback (Harold Leak managed that back in the 1940's) you'd be down to 0.35% which isn't too bad. It's the same as the EL84-based Mullard 5-10 when that's operating at just 10W and it's three times better than the stock version of the much loved Mullard 3-3, for example. If you drop down to 25W then the distortion drops by another factor of two (see the graph on the 28th page of the Application Report) and I reckon you could make a decent case for that being hi-fi

Despite the apparent advantages of this valve none of the major manufacturers of the 1950s seem to have used it. I can only find a reference to Selmer guitar amplifiers and a single-ended military amplifier developing 2 watts.

[G6Tanuki]

Re: the 6BW6

Originally Posted by GrimJosef

Despite the apparent advantages of this valve none of the major manufacturers of the 1950s seem to have used it. I can only find a reference to Selmer guitar amplifiers and a single-ended military amplifier developing 2 watts.

I'm aware of a couple of public-address amps that used it, and have also seen it used to provide anode-and-screen modulation to a QQV06/40a.

Then there's always the Codar AT5 which uses a single-ended 6BW6 to drive a 6BW6 output valve.

[Diabolical Artificer]

Regarding the several QQV dual beam tetrodes, does anyone know of their use in audio amplification? They are usually VHF transmitter valves but the data sheets say they can be used as AF OP valves.

Not sure if this would be a drawback but I notice that the "screen grids" of each side is connected. Would this present a problem if used as a audio OP valve.

Andy.

[G6Tanuki]

I'm aware of at least one commercial marine transmitter that uses a 6-40A as a modulator.
The commoned screen-grids aren't a problem - just feed them from a potential-divider between the main anode HT supply and earth, and decouple sensibly.

But remember to include lots of "stopper" resistors and ferrite beads in the control-grid and anode circuits, just in case you find you've built an audio-amp that aspires to being a push-pull VHF oscillator.

[Herald1360]

Originally Posted by Dr Wobble

Not sure if this would be a drawback but I notice that the "screen grids" of each side is connected. Would this present a problem if used as a audio OP valve

It does rule out ultralinear connection for push pull.

[Radio Wrangler]

There's the YL1130 dual beam tetrode with a common screen. As said, it rules out ultra-linear use or even triode connection (unless you parallel both halves of the thing)

What it does have that will get the phools very excited is a directly heated cathode.

It was intended for PMR and aviation VHF and the direct heat was for very fast turn on so it didn't need to stay hot.

David

[mole42uk]

8 or 9 watts in Class C - what'll it do at audio frequencies in AB1?

[Diabolical Artificer]

The YL1130 is an odd looking valve David in that you can seen the grid windings. is the 8w power out per each side of the total of both sides?

I've accumulated a few of these lesser known dual beam tetrodes such as the QQV03/10 in the hope the one day my knowledge will catch up to the point where I can design an amp around them.

These QQV types can be had NOS for a sensible price at present.

Andy.

[Synchrodyne]

Originally Posted by Herald1360

It does rule out ultralinear connection for push pull.

But I think it should still be possible to attain distributed loading, with similar net effect to conventional UL, by using partial cathode loading.

Cheers,

[PE9ZZ_JO22KI]

I've seen Chinese designs using a push-pull VHF transmitter tetrode as well as amplifiers using a QQE03/12. Bit like ELL80.

Tjerk, 9ZZ

[Radio Wrangler]

I think the 'best' audio output valves are now priced out of the reach of many people who would like to either restore a piece of old equipment, or to learn a bit by building something.

Is current production done as diligently and to the same standards as when these devices were at their peak? It's difficult to judge because people's comments are strongly flavoured by beliefs.

What we're seeing now are aficionados looking for other devices because of the rarity and price of NOS preferred types. They're going to work their way through every NOS valve in existence that they can get gain out of.

Perhaps the title of the thread would have been better in the past tense... What WAS the best audio output valve? Then answers don't get flavoured by the currently distorted market for such things and can be related back to saner times when people listened to music.

David

[mole42uk]

Originally Posted by Radio Wrangler

Perhaps the title of the thread would have been better in the past tense... What WAS the best audio output valve? Then answers don't get flavoured by the currently distorted market for such things and can be related back to saner times when people listened to music

Well, I certainly didn't expect the amount of interest that this thread has generated. I agree that there's an incredible amount of silliness about in the audio world but what this discussion has done for me is to crystallize my ideas for a new valve amplifier. I will base the build on the Mullard 10W design, but using four EL84 valves per channel for the output. These are current production valves, they are made in sufficient quantities to ensure reasonable quality control and they are obtainable at sensible prices from many of the usual electronics component suppliers such as RS.

[Radio Wrangler]

That sounds good to me, Richard. I have this feeling that original parts would best be conserved for use in original equipment. If new valves are turning over in any quantity, then decent process control will be needed to get profitable yields, as you say.

The EL84 certainly has a reputation for sound quality and it certainly fits in with several Leaks I've repaired over the years. The only problem is that they discolour at a hell of a rate and look like they're about to fail any moment. They don't of course, but they worry me.

After you've done it, why not have a go at a somewhat more difficult task? try designing a good transistor amplifier. It's possible, but it's definitely harder than doing a reasonable valve amplifier.

David

[G6Tanuki]

Originally Posted by Synchrodyne

But I think it should still be possible to attain distributed loading, with similar net effect to conventional UL, by using partial cathode loading

All the competent designs for *RF* Linear use of the 6-40a specify you need to feed the screen from a regulated [250V] supply. These valves also like high HT+ voltages: 750-850V being typical in SSB service, where according to the specs you can get 87 watts PEP.

"Ultra-linear" wiring of push-pull output valves always seems intuitively a bit strange to me - since it means you're constrained to using an anode HT-voltage no greater than the valve's maximum screen-grid voltage.