6V6 Max Plate Voltage

[Ambugaton]

Hi Everyone,

I am a little concerned after reading that the max plate voltage is 450V according to the 6V6EH specs. The deluxe Lite I have finished has about 466V plate voltage. Should I be concerned about this?

I've read a couple threads that state between 350V - 400V is preferred for the 6V6... and I know that this is highly subjective to the listener/player, but can anyone shed any light on how plate voltage affects the tubes performance? Other than output power and break up, I don't know what else is affected.

[sluckey]

I was wondering when this would come up. 

JJ claims their 6V6s are good for 500 volts.

[PRR]

Traditionally 315 boogey, 350V if you actually measure it.

_I_ think this number was just in case, in the 6V6 heyday, they had a bunch of 300V plate stuff to use up. I think most were made with sturdier stuff. Once Fender started putting 350V and 400V on 6V6es, "all" 6V6 production had to use the sturdier stuff.

I would not fret about 466 on a 450V rating. EH could deny warranty failure on this ground but nobody can prove what voltage was used.

Why do you think you want 466V on 6V6?

As electrolytic caps go to 450V (or higher cost), I'd be thinking to stay well under 450V just for the caps.

What is the screen voltage, applied and rated?

[Ambugaton]

I don't necessarily want plate voltage at 466V. I would be curious as to why it is so high. SS rectifier? Cap can is 500V and besides input and bias circuit, they are 630V on the board.

I will measure screen voltage. I don't know what you mean by applied and rated?

[sluckey]

It's that high because you used ss rectifier on a 330-0-330 PT. You can lower that by using a tube rectifier. That stout chassis is already punched for one. I recommend doing so. BTW, I'm using JJ 6V6s in my stuff and like them.

[mresistor]

I've been using EH and JJ 6V6s for years in champs, princetons and deluxe reverb amps with high plate voltages such as yours with no problems at all. I do also favor the JJ for it's tone and ability to take high plate voltages, but some say it is not a true 6V6. They say it is more like a little 6L6. But I like them. The EH will also handle more than the data sheet specifies. And Fenders have been running 6V6's for 50 years with higher than spec plate voltages. I too, a few years ago expressed concern about this and the guys here said "don't worry about it".   So I quit worrying about it..  The worst it will do is knock a little life of your tubes. 


Using a tube rectifier is a good idea as well.   If you have the slot for it , then by all means install one.  They are only 15-16 bucks plus a tube socket .  I didn't read all of your other post, but hopefully you have the 5 volt winding for one.

[Ambugaton]

Thanks for the info. I won't sweat it. I chose the SS rectifier for a tighter low end/punchier sound. If they fail early I will try the JJs.

[sluckey]

For maximum flexibility... Install the socket and wire it up. Then get a SS plugin rectifier and some tube rectifiers. Now you are plug ' play. Swap'em around some.

[kagliostro]

If you have no 5V winding there is the Weber WZ34 option (or you can clone it)



Franco

[Ambugaton]

Is it normal that the screen voltage is identical to plate voltage? That's what I am getting

[sluckey]

yes

[Ambugaton]

Any benefit to having a lower screen vs plate? I did read that it might help with natural compression... I have no idea though.

[Willabe]

I chose the SS rectifier for a tighter low end/punchier sound.

There's more to it.

There's only so much 'tighter low end/punchier sound' you can get from a pair of 6V6's using SS vs a tube rectifier, well depending on which tube rectifier. There might be some but probably not very much. You would probably get more of a 'tighter low end/punchier sound' with a different speaker than using a SS rectifier set up.     

This is because of the power tubes current draw and how much current the rectifier tube can give.

A pair of 6V6's in class AB will draw way less current compared to larger power tubes like 6L6GB/GC or EL34's.

If the rectifier tube can keep up with the power tubes current draw demand, then the tube rectifier won't sag and it will stay/keep that  'tighter low end/punchier sound'.

Also if the PT can't supply the power tubes current demands this will cause sag and a SS rectifier set up won't help stop that.

If you do like Sluckey suggested then you can hear this for your self. 

[Ambugaton]

I have a 5YG, would that be compatible in this circuit?

[Willabe]

I have a 5YG, would that be compatible in this circuit?

I think you mean a 5Y3?

[Ambugaton]

I have a 5YG, would that be compatible in this circuit?

I think you mean a 5Y3?

Yes. 😂

[HotBluePlates]

Any benefit to having a lower screen vs plate? I did read that it might help with natural compression... I have no idea though.

A lower screen voltage yields a lower possible peak plate current. Whether or not this is even relevant is individual-build-dependent (meaning it depends on the balance of several factors in an individual amp).

I believe you're thinking of using a large-value screen resistor, which does have a side-effect of lowering the screen voltage. But that large resistor increases compression because it dynamically lowers screen voltage as you push towards maximum output power.

However, if you are using a solid-state rectifier for max low end tightness, why would you want to undermine that by using large screen resistors? You could just as well use a tube rectifier for some of the same effect, unless you were simply wanting to avoid having another tube & socket...

I chose the SS rectifier for a tighter low end/punchier sound.

There's more to it.

There's only so much 'tighter low end/punchier sound' you can get from a pair of 6V6's using SS vs a tube rectifier, well depending on which tube rectifier. There might be some but probably not very much. You would probably get more of a 'tighter low end/punchier sound' with a different speaker than using a SS rectifier set up. ...

And coupling caps could be shaved somewhat to clear up low end. As well, tone stack capacitors could be changed for a slightly clearer bass, or cathode bypass caps could be reduced.

So there's really multiple places this "issue" could be attacked, and it's a bit of empirical alchemy to decide where is the best place to do what.

... _I_ think this number was just in case, in the 6V6 heyday, they had a bunch of 300V plate stuff to use up. I think most were made with sturdier stuff. Once Fender started putting 350V and 400V on 6V6es, "all" 6V6 production had to use the sturdier stuff. ...

Could you expand on this some?

I had always wondered if the plate voltage rating was mostly due to pin spacing & sockets, as I notice the 807 has a higher plate voltage rating than the otherwise-similar 6L6GB when the plate pin is moved to the top cap.

However, I also notice the higher plate dissipation tubes seem to carry a higher plate voltage rating, and it makes sense that there is thicker plate material in the bigger tubes (and that thicker material may have been later used in lower-rated tubes).

[PRR]

This is all arm-chair hand-waving.

> voltage rating was mostly due to pin spacing & sockets, as I notice the 807 has a higher plate voltage rating than the otherwise-similar 6L6GB when the plate pin is moved to the top cap.

We know RCA first released the 6L6 as 400V, then quickly re-rated for 360V. I have heard the Micanol(?) base was not long-term stable with higher voltage.

The 807 does not put plate voltage across the base.

Much later (newer materials) 6L6GC rated 500V, Philips rated EL34 at 800V. This is debatably wise, but there it is.

I don't know if there is "300V plate stuff". As 6L6 shows, it may be the limit is the base material. That said, if Ken-Rad got a batch of base-stuff RCA was rejecting because it would not stand even 360V, they could use it in the lower rated 6V6.

> higher plate dissipation tubes seem to carry a higher plate voltage rating

Well, if you are going for More Power, you either need more current or more voltage (or both). More current means a bigger cathode and more heater power. More voltage is often a better path. Obviously there are limits both ways, both in materials and their costs. Oxide-coated cathodes don't do well with >1KV plate voltage (back-scatter rips the soft oxide). E-caps go to 450V so even a 2-stack is only 800V before cap-costs really soar. The 600V conditions for 6550 and 8417 are a practical goal for receiving tube technology.

[HotBluePlates]

Gotcha.

My overall thought process was, "if there is such stuff as 300v plate material, and higher plate (but really screen) voltage equates to higher electron velocity (and bigger wham when they impact the plate), then higher-dissipation plates are probably also higher-voltage plates."

But then I was thinking about whether the plate voltage rating is about arc/leakage prevention, at either the base and/or mica spacers.

To some extent I guess it's "all of the above" and only the manufacturer knows where the limiting factors really lie.