Power Tubes Replacements & Plate Voltage Fears

[Misanthrope]

Hello Folks,

My eldest son and I both have the same relatively low-powered (18-20w) combo amp that uses 2x 6V6 power tubes, and the manufacturer strictly (but somewhat confoundingly) advises against ANY other brand of replacement than JJ's, claiming that they are the only power tube capable of safely handling the amp's high plate voltage of ~450v.

That said, JJ's are far from my favorite brand of preamp or power tube, and I think it's safe to say that many of the more budget conscious amp builders will use them wherever they can for cost and availability purposes, but does this seem like accurate information to you? In other words, aren't some of the other premium brands of 6V6 power tubes out there (e.g. NOS RCA, Mullard, TAD 6V6GT-STR, etc., etc.), perfectly or equally capable in this regard? It just seems kinda crazy to me, to produce an amp that can purportedly use only ONE, single, brand of tube safely? I mean, what if JJ suddenly went out of business altogether? Then what, right?

Perhaps most importantly, for someone like me who is just a musician and not an expert or highly trained amp tech, what's the worst that could happen with other premium (or NOS) tubes? Are the other brands so inferior or compromised or sub-standard in this regard, that it could it potentially damage the amp?

Thanks for listening, and thanks ahead-of-time to all who choose to respond.

[g1]

Not sure if it is still the case, but the JJ 6V6 was not a true 6V6, it was somewhere between 6V6 and 6L6 and could take a lot of plate voltage (500V) compared to normal 6V6's.
If your amp could handle the extra heater current, you could go with 6L6GC instead.

[Chuck H]

This^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

I think the EH tubes were also reported to handle high plate voltages (but wait for someone else to back this or see about it yourself on line). What g1 says is true. There was a time, and I don't know if it's still the case, when the JJ tubes (and I think EH as well) were being used in some older 6V6 amps that already had high plate voltages when the wall voltage was 110 / 117VAC. So today those amps would have about 430VDC +/- depending on bias and guys were using these tube brands because they would survive. Remember that we're also in an era when those amps are more likely to be cranked into clipping the power tubes at those higher voltages. Some brands held up and A LOT of old and even NOS tubes went kablooey. So that's where this comes from. IMHO building a modern (ish) amp that relies on a 6V6 capable of handling 450Vp is irresponsible. Especially in an era when specific tube models come and go like a fart in the wind. So...

Like g1 indicated, you can use 6L6's if your power transformers filament capacity is up to the extra current. The way tubes work you won't actually be making much, if any extra watts for using the bigger bottle (it's more about the actual voltage and current) and 6V6 and 6L6 tubes are generally happy with the same OT impedances so the 6L6 should work fine for that too. So I'll back g1's suggestion here.

[Misanthrope]

Well guys, thank you very much for your replies here, and although I'm grateful for your insights, I wish that I could say that I feel clearer or better about things.

For starters, I have to agree with @ChuckH when he says it's "irresponsible" for a manufacturer to produce such an amplifier, because it leaves me/us with no answer to my earlier question, which was . . . "What if JJ suddenly went outta business"? What then? Am I supposed to just throw this amp away because no one makes a comparably robust 6V6 tube? Something is just not right here!

I've contacted multiple vacuum tube vendors, all quite reputable, asking them this same basic question (i.e., can I use a standard 6V6 tube in this amp, or must I stick with JJ to be safe), and three out of four said that the whole premise was nothing but empty fear-mongering, that I could easily and safely use ANY mainstream (recognized) brand of 6V6 tube. But are those tube vendors gonna reimburse me if doing so ends-up toasting my amp? No, they're clearly not!

So color me LOST! I literally do not know how to proceed at this point. I guess it's to install some recommended but mediocre JJ's, return all others for (hopefully), a refund or exchange, and rebias the amp, because we all know full-well that even with JJ's, no two sets of matched tubes are gonna be the same.

Good Lord, I need a drink! And it's only 9:00 am!!!!

[Chuck H]

. . . "What if JJ suddenly went outta business"? What then? Am I supposed to just throw this amp away because no one makes a comparably robust 6V6 tube?

There's almost never NO answer to these problems. As mentioned, you can use 6L6 tubes. There are circuits that can reduce plate voltages as well. And chances are that there will always be a robust 6v6 tube available because there's still so many old and new Fenders that run 420+ volts on them. So it's not all dark. Just not quite as easy as plugging in the tubes you want.

I've contacted multiple vacuum tube vendors, all quite reputable, asking them this same basic question (i.e., can I use a standard 6V6 tube in this amp, or must I stick with JJ to be safe), and three out of four said that the whole premise was nothing but empty fear-mongering, that I could easily and safely use ANY mainstream (recognized) brand of 6V6 tube. But are those tube vendors gonna reimburse me if doing so ends-up toasting my amp? No, they're clearly not!

They can say such things because they know they'll never have to be accountable and they want you to spend your money with them. (<period) I've learned not to trust tube vendors at all.

So color me LOST! I literally do not know how to proceed at this point.

Oh sure you know what to do. You can still research on line to find out about other robust 6v6 alternatives. You can ask after the voltage reduction circuit I just mentioned. You can do a test or two and probably install 6L6 tubes OR... You can grump and moan and install the JJ's Which, admittedly, does afford you the opportunity to be disappointed and unhappy. Even though even THAT isn't really so bad. But you do you man.

[Helmholtz]

BTW, what amp is it and is there a schematic?

Also, what's wrong with JJ tubes? I'm not aware of a bad reputation.

[Misanthrope]

Again guys, my most sincere thanks and respect for your postings and opinions here. I value and appreciate any and all opinions, even when they're contrary to my own.

Needless to say, there are different camps when it comes to almost everything in life, and the effect of power tube brand and type on amplifier performance and tone, is no exception, so there's really no need in beating this horse much further.

Personally speaking, I have no issues with the quality, longevity or overall integrity of JJ tubes (none whatsoever!), but in my own 40+ years of experience, their power tubes (no matter how "robust"), tend to yield a tone that is excessively heavy in the mids and bass (regardless of circuitry), when compared to other brands, and anyone who has ever evaluated them relative to (say) NOS RCA blackplate's, JAN's or Sylvania's, knows this to be true.

In fact, a recent poll of 200+ participants on The Gear Page indicated that the majority of those polled believe that power tubes effect overall tone by as much as 10-25%, and NO-where, is this more true than in the brown face (6g3) circuit, which is the specific type of amplifier that we're talking about here.

Anyway, thank you both again for everything you've contributed here. We can now close this thread out, and in the meantime, I will be taking your recommendation to research the availability of other more "robust" but competitive brands of 6V6 tubes.

Cheers!

[g1]

We can now close this thread out, and in the meantime, I will be taking your recommendation to research the availability of other more "robust" but competitive brands of 6V6 tubes.

Cheers!

Not so quick!
Meanwhile, in another thread, the 65 Princeton Reverb came up, which is running the plates at 440VDC with no notes about preferred power tubes. Though they no longer state 'all voltages +/-20%' on their schematics, I'm sure your 450V would fall into tolerance.
Usually, statements like the one from your manufacturer are about warranty claim issues. They want to reduce them and believe the JJ's will help with that.
Worst case as far as damage to the amp from power tube failure is usually a burnt screen resistor (assuming no one puts tin-foil on a blown fuse).
If Fender isn't worried about those kind of voltages on 6V6's, I don't think you need to, just use a reputable 6V6.
Of course it is possible your amp is doing something very unconventional we are not taking into account, so we need to know make & model as Helmholtz mentioned above.

[Misanthrope]

Of course it is possible your amp is doing something very unconventional we are not taking into account, so we need to know make & model as Helmholtz mentioned above.

'62 Fender Deluxe . . .
Suhr Hombre . . .
Allen Brown Sugar . . .
Cutthroat Down Brownie . . .

Take your pick.

And I should probably add that I've got several other amps here that run at >420v including a '65 DRRI which has run just fine for 5-years with run-of-the-mill Tung-Sol 6V6's.

[g1]

'62 Fender Deluxe . . .
Suhr Hombre . . .
Allen Brown Sugar . . .
Cutthroat Down Brownie . . .

We were specifically asking about your amp.
If you don't want to disclose that, it's up to you. But a bit surprised you would want to protect them feeling the way you do about their power tube 'demands'.

[xtian]

Have used over 300 JJ s over past 13 years. One quick burn out, a couple mildly microphonic. Not bad, on par with others including NOS. They sound great, and I can source them reliably.

[Mick Bailey]

So long as screen voltage is controlled I've never run into problems with a regular 6V6 in a tube amp. Amps without screen resistors are more prone to failure, but that's easily fixed. If the voltage is too high, use a MOSFET reducer - these work very well and are easy and cheap to build and install. I do like the JJ 6V6. I've never encountered a tube being heavy in bass or mids - all I hear and see on the scope is different clipping characteristics. Where would such a tonal difference arise from?