6V6 (other than JJ) that can take high plate dissipations

[HaroldBrooks]

Maybe a Russian tube can be an option.
In general they made tubes at military factories and meeting military specs, so they tend to be overbuilt.

Many models are NOT exact clones of American types, and resellers try to get the most buck for the bang; AFAIK one Russian type , sold as a "weak 6L6" (which would be counterintuitive) is actually a very overbuilt 6V6 equivalent.

Search for it and compare specs, you might be surprised.

Thanks ! Good idea, I've seen those tubes and wondered. I will buy a couple and find out. This could be really good, as the amp already has a slightly bigger 20 watt output transformer and I've added a small DC fan for cooling.

Just ordered two good ( supposedly...) 6P6S tubes from Ebay. Not even sure it those are the ones you guys are talking about, LOL, but I felt the urge to buy something, and the price was cheap.

I will let you know how they work out.

[HaroldBrooks]

Ok, got the Russian 6n6c tubes today. All was looking good, 3 tubes for a small $23 delivered, and I do believe they are 100% new and never used, as they were in the original boxes sealed with thick staples that had rusted over time, and they each contained a datasheet wrapped around the tube. Nice !

--- First amp up for a test try was my Supro Model 50 and they worked perfectly in that amp installed and dimed for about 10 minutes. I did seem to notice a tiny bit more distortion and bass with these tubes over the RCAs (went back to the RCAs for just a moment to A/B compare), but I realize it's probably not the Russian tube itself, but how it's responding as part of the overall circuit. Nice sounding distortion in this amp none the less.

--- Second test amp was the one that started it all, my 1956 National, and unfortunately one of the power tubes went into an oscillation as I raised the volume on this amp. I swapped the tubes to different sockets, same thing. This is the amp that is biased a bit over 14 watts plate dissipation and around 350vdc for the plate voltage, so my guess is that the new Russian tubes can't take something about the setup either in Bias, voltage, or both. Nothing seemed damaged, just not able to raise the volume past half way or so.

--- Third test amp a 1955 Valco McKinney amp, and in this amp the Russian tubes again work superbly. No red plating after 15 minutes of playing, and the same basic change in sound, that is an addition to Bass and a bit more distortion than the RCAs that were in that amp (Your results may vary...)

All in all I am VERY HAPPY with these 'new' vintage Russian tubes ! I will go into the first amp with the tubes installed and measure the plates and the watts dissipation later tonight, so I can chart some of the differences.

Can't say anything else about long term durability, but so far so good.

I believe that USA made tubes of the same generation are probably going to be impossible to beat in many ways. We were building great stuff back then, and I have proof in that I have so many great running super old tubes in my vintage gear.

All Comments Welcome !

Here's the Factory specs / limits for the 6n6c / 6p6s :





Designed for power amplification of low frequency.

Durability at least 500 hours

filament Voltage ...... 6,3 ± 0,6 V

Filament current ...... 450 ± 40 mA

anode voltage nominal (DC) ...... 250 V

anode voltage limit (DC) ...... 350 V

anode current ...... 45 ± 12 mA

Voltage grid of the first (DC) ...... 12.5V

Reverse current grid first ...... no more than 2 µa

The second grid voltage nominal (DC) ...... 250 V

The second grid voltage limit (DC) ...... 310 V

Current of second grid ...... no more than 7.5 mA

power dissipated by the anode limit ...... 13.2 W

power dissipated by the second grid, the limit ...... 2.2 W

voltage between cathode and heater limit (DC) ...... 100 V

steepness of the characteristics ...... 4,1 ± 1,1 mA/V

Internal resistance ...... 52 kom

Output power ...... not less than 3.6 W

Total harmonic distortion ...... 8%

Capacity input ...... 9,5 ±1,6 pF

Capacity output ...... The 6.5 ± 2.7 pF

Capacity checkpoint ...... no more than 0.9 pF

[tubeswell]

Don´t remember the exact details.
Only remember reading (maybe in this very forum) that XXX brand 6L6(yyy letters behind it or even no letters at all) was actually ZZZ (insert Ciryllic code here) which was for all purposes a VERY GOOD 6V6 type, so good that it reached the lower limits of 6L6 some true specs and could get away with the impersonation.

I commented that here so maybe somebody would chime in and say "hey!! you are talking about xxx brand 6L6!!!!"

If you’re thinking about the 6P3S, which has a 900mA filament and is rated for 20W, they don’t handle plate voltage over 400 very well when run as a 6L6, but may do better with colder biasing, and higher load resistance (I.e, run more like a 6v6)

[Pedro Vecino]

It´s probably that. 6P3S as 6V6. Groove tubes distributed it 25 years ago as 6V6HD.
It was the first Russian "6L6" distributed in Western Europe through brands such as Edicron, Ultron and others before the arrival of Groove tubes.
I have not seen problems with the voltages. I recently equipped a Supertwin with them. 500V and 25mA per tube. Where I did find problems was then to equip a Princeton due to the excess consumption in the heaters. I never used them with 6V6´s amps.

[Leo_Gnardo]

If you’re thinking about the 6P3S, which has a 900mA filament and is rated for 20W, they don’t handle plate voltage over 400 very well when run as a 6L6, but may do better with colder biasing, and higher load resistance (I.e, run more like a 6v6)

Back in the 80's, Groove Tube sold their relabeled 6P3S as "special super duper 6V6" completely disregarding their need for double the filament current and a change of bias voltage. Had lots of trouble then with people buying the baloney, installing them in their amps and watching expensive smoke come out. When I warned the local store that was selling them to please STOP! they got a big attitude about it. Since I also did repairs for that store, the owner's answer was "so what, you should be glad you're getting extra work." Sometimes ya just can't win.

Similar problem but not as big early 90's when Sovtek/EH released their 7591XYZ, simply a repinned wafer base Sovtek 5881. Few amps need 7591 therefore less of a problem.

[HaroldBrooks]

You are 100% correct Leo_Gnardo, ignoring filament current a common mistake for newbie tube rollers.

You have to be concerned with Filament current. It's important to the life of your transformer, all else equal. With some amps (not many) you may have a transformer that was put in as a "one size fits all" and it can handle a little extra current, but I would never assume that is the case without researching it first. From what I've seen, a power transformer burning up is the most catastrophic thing that could happen in a tube amp, and you are playing with fire if you ignore it.