Max plate voltage and plate dissipation

[playloud]

TAD and Ruby are two different companies and spec out different STR's. The Ruby is 450v.

Both TAD and Ruby "STR"s are just rebadged Shuguang EL34Bs. Where did you get the 450V figure from?

Fwiw, the real problem with EL34s in Marshall amps tends to be screen voltage handling. Note that there is often only a few volts between plate and screen voltages (although this gap should widen under load), yet the rated screen voltage is only 500V (v. 800V for the anodes). Moreover, some contemporary manufacturers have a poor track record of actually living up to their specs (which they've copied from the original Philips datasheets anyway - less so the construction!)

 

[Kutt]

Both TAD and Ruby "STR"s are just rebadged Shuguang EL34Bs. Where did you get the 450V figure from?

When the tube was still being produced it was listed on each web site that sold the product. I think it's still listed on Doug's Tubes. Ruby released the EL34BHT variant to handle higher voltages.

There are pllllenty of rebranded tubes out there. But where the various STR's are concerned lots of people state they too are rebranded but provide absolutely zero evidence of it. Until someone surgically takes multiple different STR's apart and analyzes each component I remain skeptical. Better yet until someone who worked/works in the old Shuguang, Psvane, Linlai, Reflektor, or JJ plants come forward to tell their tale then I call bullshit.

 

[Pete Farrington]

What’s BS is labelling a valve ‘EL34’ if it can’t meet the basic requirements of the EL34 type standard.
From https://dougstubes.com/collections/el34-kt77-6ca7/products/ruby-el34bstr

For use in applications where the plate voltage is less than 450 vdc. For higher voltages, use the Ruby EL34BHT's.

The fact Ruby don’t list it anymore indicates that its substandard limits might be causing excessive claims on Ruby’s industry leading 6 month warranty.

As Ruby seem to have given up on this valve (or any EL34 at the moment), I suspect Doug’s Tubes might only provide a 30 day warranty?

The Design-Center rating seems to be the "best" one to use since it accounts for actual real-world use & variations in a circuit

Exactly!
To convert a design maximum dissipation limit to its design centre equivalent, multiply it by 0.86.
Or just use 60% rather than 70% in the calculation.
Either of the above methods ends up with the same idle wattage, eg 18W for 6L6GC.

Remember that’s just an upper limit, check whether idling any cooler sounds worse. If you’re still happy, then enjoy longer valve life!
30mA idle on 6L6 family / EL34 is almost invariably plenty high enough to eliminate crossover distortion.

I’ve added some links to post 13, in case you want to research the topic a bit further

Note that there is often only a few volts between plate and screen voltages (although this gap should widen under load), yet the rated screen voltage is only 500V (v. 800V for the anodes)

The type standard for EL34 is a Vao of 2kV, Vg2o of 800V!
When dissipating 25W and 8W respectively, the Va and Vg2 limits are 800V and 500V

https://frank.pocnet.net/sheets/010/e/EL34.pdf

Yikes!

 

[Kutt]

What’s BS is labelling a valve ‘EL34’ if it can’t meet the basic requirements of the EL34 type standard.
From https://dougstubes.com/collections/el34-kt77-6ca7/products/ruby-el34bstr


The fact Ruby don’t list it anymore indicates that its substandard limits might be causing excessive claims on Ruby’s industry leading 6 month warranty.

As Ruby seem to have given up on this valve (or any EL34 at the moment), I suspect Doug’s Tubes might only provide a 30 day warranty?

It was a Shuguang-built tube and somewhat quickly disappeared off the market after the alleged fire at the factory. Will they restart production with another manufacturer? Who knows. But I can tell you that the timeframes align. To boot, their entire product line nearly vaporized after the fire. Scraps and slim pickings. I think they had most of their eggs in the Shuguang basket.

 

[Pete Farrington]

There are pllllenty of rebranded tubes out there. But where the various STR's are concerned lots of people state they too are rebranded but provide absolutely zero evidence of it

STR means special tube request.
It was usually used by large customers to order an uprated / ruggedised / otherwise amended version of a regular valve type.
Most famously it was used for the STR387 and STR415 versions of the 6L6GC, commissioned from Sylvania by Fender etc. It seems to have been pretty much a ruggedised 7581A, which have a 35W design maximum anode limit, Fender’s late 70s uprated, high power range was designed around it, eg the 135W Twin Reverb.

Anyway, back on the topic, it doesn’t seem credible to me that all these rebranders eg Ruby TAD would have each made a special tube request to Shuguang to commission a woefully substandard EL34.
Rather it seems more likely that the STR designation came from Shuguang, eg to identify it from their’s and other manufacturers’ EL34 versions.

It was a Shuguang-built tube and somewhat quickly disappeared off the market after the alleged fire at the factory. Will they restart production with another manufacturer?

As Shuguang were the manufacturer, who do you mean by ‘they’ above?

 

[Kutt]

As Shuguang were the manufacturer, who do you mean by ‘they’ above?

Ruby

 

[Kutt]

Anyway, back on the topic, it doesn’t seem credible to me that all these rebranders eg Ruby TAD would have each made a special tube request to Shuguang to commission a woefully substandard EL34.

This is part of my point. It's all just speculation from everyone, all the time. No one knows any facts because the rebranders/STR's and manufacturers are tight lipped. I've yet to see anyone tear numerous (current or recent production) STR's apart to debunk any of it.

 

[Kutt]

Rather it seems more likely that the STR designation came from Shuguang, eg to identify it from their’s and other manufacturers’ EL34 versions.

Assuming this data sheet is accurate, "theirs" (Shuguang's), own is already at 800v. So the argument that Ruby's STR is actually Ruby's STR holds weight.

 

[Pete Farrington]

Ruby

Thanks for the clarification.

No one knows any facts because the rebranders/STR's and manufacturers are tight lipped.

Human nature seems to be to distance themselves from a turd they’ve just deposited. Why would someone admit they’d built, bought or missold thousands of substandard valves?

Assuming this data sheet is accurate, "theirs" (Shuguang's), own is already at 800v.

I suggest to take modern valve info as being notional rather than representative of the production norm.
They don’t even bother to state what rating system was used. So how did they come to devise the numbers they publish (which coincidentally match exactly the numbers on the Phillips info).

So the argument that Ruby's STR is actually Ruby's STR holds weight.

Again, why would Ruby knowingly order a valve they intended to label and advertise as EL34 that didn’t meet the requirements of the EL34 type standard?

My guess is that this valve highlighted their poor goods in QC / inadequate testing protocols. Having realised that, they sold off stock to resellers, such as Doug’s Tubes, thereby getting some financial return whilst minimising warranty claims.

In the old days of RETMA, substandard valves got crushed.

 

[Ivan H]

TAD and Ruby are two different companies and spec out different STR's. The Ruby is 450v.

Ok, here's the data sheet from the Acclaim Music site advertising the discontinued (Shuguang) Ruby EL34B STR. Again, it shows the max plate voltage as 800V.
The datasheet is the last image on the Acclaim Music page.

Ruby Tubes EL34BSTR-2 Duet Matched Power Amplifier Tubes

High-gain Ruby Tubes EL34BSTR-2 with dynamic tone. Extra-strong bottle. Loud and clear. Often reviewed as well-balanced. Ruby exclusive with large bottle, gold-plated grid, and extra internal anchoring. All Ruby output tubes are labeled on the base with the exact

www.acclaim-music.com

As has been said, both the Ruby & TAD EL34B STR were produced by Shuguang. Cheers

 

[Kutt]

Ok, here's the data sheet from the Acclaim Music site advertising the discontinued (Shuguang) Ruby EL34B STR. Again, it shows the max plate voltage as 800V.
The datasheet is the last image on the Acclaim Music page.

Ruby Tubes EL34BSTR-2 Duet Matched Power Amplifier Tubes

High-gain Ruby Tubes EL34BSTR-2 with dynamic tone. Extra-strong bottle. Loud and clear. Often reviewed as well-balanced. Ruby exclusive with large bottle, gold-plated grid, and extra internal anchoring. All Ruby output tubes are labeled on the base with the exact

www.acclaim-music.com

As has been said, both the Ruby & TAD EL34B STR were produced by Shuguang. Cheers

I suspect that may be the spec sheet for their EL34BHT. Too bad the tube name isn't actually printed on the sheet.

 

[Kutt]

Ruby Tubes EL34BSTR Power Tube - StewMac

High-gain EL34 with dynamic, well-balanced tone—loud and clear.

www.stewmac.com

 

[Kutt]

Human nature seems to be to distance themselves from a turd they’ve just deposited. Why would someone admit they’d built, bought or missold thousands of substandard valves?

The entire industry is generally tight lipped, which was my point. I guess by these standards every tube in your amps and mine are turds. hahahaha.

I can keep this flapjack on the griddle all month long...

 

[playloud]

Ruby Tubes EL34BSTR Power Tube - StewMac

High-gain EL34 with dynamic, well-balanced tone—loud and clear.

www.stewmac.com

View attachment 137605

If I recall correctly from my previous research, this notice started appearing after the EL34B was discovered to have a high infant mortality rate. The "450V limit" was simply proposed by vendors to sell off existing stock, and Shuguang introduced the "EL34BHT" (presumably the "HT" stands for "high tension").

The reasons why I suspect the TAD/Ruby "STRs" are the same are (a) they appear to have identical construction (b) you can literally order rebadged Chinese valves on Alibaba (so Occam's Razor). It's still possible they do some culling of bad valves on arrival (e.g. burn-in testing), so the rebadged valves may have a lower failure rate.

Like many other tube variant acronyms (e.g. the low noise versions of the 12AX7), "STR" is one of those things that meant something concrete during the "golden era" of tube production, but is now often simply a marketing term.

The entire industry is generally tight lipped, which was my point. I guess by these standards every tube in your amps and mine are turds. hahahaha.

I can't speak for Pete, but the oldest valves in any of my amps are Winged Cs

 

[Kutt]

I can't speak for Pete, but the oldest valves in any of my amps are Winged Cs

I've got an old quad of them hanging around. I really should spend some time with them. Never did and I only read good things about 'em.

 

[mickeydg5]

I've got an old quad of them hanging around. I really should spend some time with them. Never did and I only read good things about 'em.


View attachment 137611

I have RFT which were original in my first amplifier, 1987 Jubilee. They still sound good. Not that I play much anymore.
I really like the Winged C as I use to try them out once in a while. I like them better than those RFT because they have a little bit more.

 

[Gutch220]

What’s BS is labelling a valve ‘EL34’ if it can’t meet the basic requirements of the EL34 type standard.
From https://dougstubes.com/collections/el34-kt77-6ca7/products/ruby-el34bstr


The fact Ruby don’t list it anymore indicates that its substandard limits might be causing excessive claims on Ruby’s industry leading 6 month warranty.

As Ruby seem to have given up on this valve (or any EL34 at the moment), I suspect Doug’s Tubes might only provide a 30 day warranty?


Exactly!
To convert a design maximum dissipation limit to its design centre equivalent, multiply it by 0.86.
Or just use 60% rather than 70% in the calculation.
Either of the above methods ends up with the same idle wattage, eg 18W for 6L6GC.

Remember that’s just an upper limit, check whether idling any cooler sounds worse. If you’re still happy, then enjoy longer valve life!
30mA idle on 6L6 family / EL34 is almost invariably plenty high enough to eliminate crossover distortion.

I’ve added some links to post 13, in case you want to research the topic a bit further

The type standard for EL34 is a Vao of 2kV, Vg2o of 800V!
When dissipating 25W and 8W respectively, the Va and Vg2 limits are 800V and 500V

https://frank.pocnet.net/sheets/010/e/EL34.pdf

Yikes!

Where did you learn everything you know about this stuff? You must've had a career involving this.

 

[mickeydg5]

Ruby does not carry the EL34B-STR any more it seems. But when it was offered I would think it adhered to that standard and specification.
So look up the datasheet for that tube.

 

[Resident 217]

Here's a place where to find tube data for every tube known to man...almost.
For interests sake.

Much tube data

 

[mickeydg5]

Here's a place where to find tube data for every tube known to man...almost.
For interests sake.

Much tube data

Try this one. You will be much more impressed.

Frank's electron Tube Data sheets

electron Tube Data sheets - Type index

frank.pocnet.net