6W6 vs 6V6

[Pdavis68]

From what I can tell, 6W6s are very similar to 6V6s. Slightly higher plate dissipation, lower screen voltage rating. But it seems like people have interchanged them with 6V6s without circuit modifications. And from what I have read so far, it seems like, tone-wise, they sound very similar.

So my question is, why aren't people using 6W6s instead of 6V6s? 6W6s are dirt cheap, generally running $2-$4 or so each. Is there any downside? And even though the screen voltage rating is lower, can you still run it at a higher screen voltage (as long as you keep the screen dissipation at or below 1.25W)? I know you can run plates at a higher voltage as long as the dissipation is kept within spec.

[km6xz]

They are not very similar, the 6W6(and 6Y6) have lower anode max voltage, a lot higher heater current requirement and 4 times the Gm of a 6V6. The plate resistance is not the same. They are capable of more plate current but at lower voltage so they were useful in things like servo amps, TV vertical amplifier amplifiers. With a suitable transformer that can be used as a power output, not a lot, but useful amounts. They are also known for higher Thd so actually might make a nice guitar amp since harmonic distortion is a friend to electric guitars. For audio applications they are usually used in triode configuration.

[Pdavis68]

Well, the max voltage is more of a recommendation than an actual maximum. Fender runs 6V6s above 315V and from what I've read, people have been running 6W6s in place of 6V6s without a problem. They may not last as long, but if you're only paying $2/tube, who cares? I was thinking more in terms of new builds, though, where the extra heater current wouldn't be a problem if you design for it. That is, if you're doing a new build, you just need to find a PT that can handle the necessary current. So it brings me back to why not use 6W6s in place of 6V6s? I'm inclined to design for 6W6s based on their price. Again, not from personal experience, but from what I've read, they sound comparable to 6V6s in 6V6 circuits.

[Enzo]

Used to be bacon was trash meat and it was cheap, now bacon is $5-8 a pound. Same with kale, it was a bitter vegetable mostly eaten by poor people because it was cheap, now it is the darling of the foodie world. Your cheap NOS tubes might be cheap now, but if some boutique 6W6 craze takes over, POOF, they become the darling of the booteek set and the price soars.

I can walk into a music store anywhere I go and grab a new 6V6 if I need one. if you are on tour, and find yourself in Idaho or Nebraska, and one of your 6W6s craps out, where you gonna get a new one for the night's gig? For new builds, if you mean basement projects, sure, why not. Use any power tube that strikes your fancy. But new builds as in anything remotely commercial, then the first matter is getting reliable production quantities of the tubes. And being sure your customers will have a ready supply of them as well. That is why we will use 12AX7 instead of something very similar but with a different base pinout.

The question isn't so much why wouldn't we use them, it is why SHOULD we use them. For YOU making an amp, there is no real reason not to, but for a commercial venture, I think it would be a poor choice.

[Pdavis68]

That makes sense.

Your mention of bacon was interesting because I was just noticing the other day the ridiculous price for flank steak which used to be cheap and considered the poor person's meat. I love flank steak, but at about $12+/lb forget it. Those are crazy prices...

[km6xz]

The plate resistance is different also, since it was intended as a higher current tube, but lower power so you will likely have to use custom wound transformers. That would wipe any price advantage of a cheap rare tube. After tube TVs went out of style, the last remaining use of the 6W6 meant that many were sent to landfills from the thousands of closing TV repair shops.
Unless the Svetlana plant is returned to service, the 3 factories now are never going to build more production lines. That means product type distribution will be concentrated on a few high volume tubes(12AX7, 6L6, EL34) and I don't see the economic advantage for one of those three to divert production to a tube that is not used by any gear makers. So the rare 6W6 will become even more rare if it becomes a new trendy tube roller type. Suddenly that price will not be $2 or even $12, or $20. All it would take is one of the gurus to mention "the 6W6 has the clarity in the presence area link a spring rise plus finely articulated sound stage in the mids...." and it is a $45 tube.