What's the best audio output valve?

[kalee20]

I agree quite a lot - cost being quite important (see my post early on in this thread).

Only down side is that modern-day cost isn't a technically viable quantity to reckon by - unlike original manufacturing costs which did depend quite a lot on production difficulties, exotic materials, etc.

The EL84 is not my favourite valve, but I agree it does have a lot going for it and I've never had a problem with one. It just runs stinking hot at its max ratings (which I agree, doesn't have to be done). The fact that it is still in production says much, too.

Now, if Mullard had raised it to 15W anode dissipation and put it in a B9D bottle...

[mole42uk]

Originally Posted by kalee20

The EL84 is not my favourite valve, but I agree it does have a lot going for it and I've never had a problem with one. It just runs stinking hot at its max ratings (which I agree, doesn't have to be done).

In the design I am developing, while owing a lot to Williamson, the Mullard 5/10 and the Leak Stereo 20, I am planning to reduce the operating temperature and stress of the EL84s by running them in parallel. There will be four valves per channel in UL push-pull, developing 20W rms and no more.

[PE9ZZ_JO22KI]

@bikerhifinut: I trust my ears as well but only in a blind A-B test. With carefully adjusted leveling (SPL meter). So I modded my Joepie China (Rik Stoet) quad EL34 to quad KT88 with new Amplimo (Vanderveen) toroids for output transformers. I then noticed two things. The KT88s have a different impedance than the EL34 (duh!). The toroids dramatically improved sonic quality and it now sounds almost the same (!) as my sand-based amp (my trusty Philips DFA888).

Tjerk, 9ZZ

[PE9ZZ_JO22KI]

Originally Posted by kalee20

Now, if Mullard had raised it to 15W anode dissipation and put it in a B9D bottle...

They (Philips) did and called it EL503. Lovely device only stinking rare.

Tjerk, 9ZZ

[barretter]

Originally Posted by kalee20

Now, if Mullard had raised it to 15W anode dissipation and put it in a B9D bottle...

Mullard didn't but Brimar did. The EL506 has an anode dissipation of 19W in a wider bottle on a B9D/Magnoval base and was specifically designed for audio. Indeed Brimar included a complete circuit diagram for an amplifier based on the EL506 in their Design Data manuals. Unfortunately the front end was an ECC807, which is very scarce, but the input sensitivity is 220mV which is far too high for today's signal sources, so it could be redesigned with more common ECC series valves if the EL506 were readily available, which it isn't. It's not as scarce as the EL503 apparently is (what a chunky valve!) but the world's entire supply of New Old Stock seems to have been bought up by a firm in Taiwan (!), if eBay is anything to go by.