Opinions on Russian 6P6S (6n6c) 6v6 Tubes

kleuck · Post by **kleuck** » Fri 09/03/10 8:18 am

Interesting, i was thinking that 6p6s have poor tolerance, it's a very common idea !
By the way, did someone use 6AY5 ?

tubeswell · Post by **tubeswell** » Fri 09/03/10 3:48 pm

Yep knew all that copyright infringement stuff and the KT tubes etc. What got me was the revelation about 6V6GT not being a pentode. I'm pretty sure I've got a worn out jj6V6S in my amp cupboard somewhere that I can dissect. I'll have a look into it and report back

Post by **zaphod_phil** » Fri 09/03/10 4:01 pm

Yep knew all that copyright infringement stuff and the KT tubes etc.

So then you will be able to appreciate why RCA had to design the 6V6 as a beam tetrode and not a pentode.

I've got a worn out jj6V6S in my amp cupboard somewhere that I can dissect. I'll have a look into it and report back

Just bear in mind what I said about the JJ 6V6S being something in between a 6V6 and a 6L6.

Merlinb · Post by **Merlinb** » Fri 09/03/10 5:06 pm

zaphod_phil wrote: So then you will be able to appreciate why RCA had to design the 6V6 as a beam tetrode and not a pentode.

The beam tetrode was invented in England by two guys at EMI. They simply shared the idea with RCA, who had the impetus to actually manufacture them.

Post by **zaphod_phil** » Fri 09/03/10 10:48 pm

Merlin, you may recall I had the pleasure of meeting Barry Vyse a few years ago, who used to work at Marconi-Osram Valve in R&D, and eventually become the head of that company until they closed down. In the book he co-authored with George Jessop (RIP), he says:

"Manufacture of the pentode, a Philips invention was fraught with serious patent issues for companies such as M-OV. Out of adversity, however, came triumph, because the work devoted to ways of avoiding the Philips pentode patent led directly to the invention of the beam tetrode by CS Bull, who was working for M-OV's parent EMI, see British Patent 432932. Valves made to this design were marketed under the type 'N40'. George recalls how difficult the assembly of these valves was to handle. This basic design was worked on by the engineers at RCA and M-OV and from the development emerged the classic output beam tetrodes, RCA 6L6 and the M-OV KT66 (1936)... The Americans described this new class of tubes as beam tetrodes, but M-OV, uniquely hung on to their own graphic terminology, Kinkless Tetrodes'."

So there we go.

Merlinb · Post by **Merlinb** » Sat 09/04/10 2:55 am

zaphod_phil wrote: by CS Bull

What happened to Sidney Rodda? Bet he was pi$$ed when Bull took all the credit...

Post by **zaphod_phil** » Sat 09/04/10 1:39 pm

George Jessop was actually there at the time and quite possibly may have even been personally acquainted with Cabot Bull and Sidney Roda. However, I think you would need to check the patent itself to really see who got the credit, whether genuinely deserved ornot, but in any case that's somewhat of a side issue. The main point I learnt from this is that RCA and M-OV actually shared the development of a more practically manufacturable form of the beam tetrode.

Elsewhere in the book it says, "This class of valve developed and perfected in cooperation with RCA in the period up to 1936, proved to have the ideal characteristics for the audio output role. In particular the KT66 (M-OV development of the RCA 6L6) and its later higher-powered offspring, the KT88...." So while there seems to have been joint work in this area, it appears that the 6L6 was indeed in existence slightly before the KT66.

RCA is mentioned numerous times in the book, and it's also explained how RCA was formed by GE and absorbed the American arm of Marconi, resulting in the long-standing relationship between RCA in the US and Marconi in the UK.

Post by **zaphod_phil** » Tue 09/07/10 8:55 am

FYI, back on the subject of the 6V6, according to the Wikipedia article on Beam Tetrodes (FWIW):

The widespread use of the 6V6, both internationally (where 6.3 volt heater supplies were more common) and in many types of military equipment, probably brings the 6V6 to the forefront as the most common beam tetrode in use over the lifetime of the beam tetrode design. It was miniaturised as the 7-pin 6AQ5 (with a derating to 70% output power in push-pull Class AB1), as the 9-pin 6BW6, and as the Loctal (self-locking 8-pin base) 7C5. Many amateur radio transmitters also used the 6V6, either as the final power amplifier, or in the driver stages.

They've missed out the 6CM6, which is another 9-pin version of the 6V6, and sometimes used in 18W amps.

StarGeezers · Post by **StarGeezers** » Tue 09/07/10 9:27 am

... lest we forget the Russian 6AQ5 equivalent (sorta') ...6P1P which sounds Great in an 18 watt (quad)

kleuck · Post by **kleuck** » Fri 09/10/10 5:16 pm

By the way, i wonder if the 6P1P can stand high voltages like 6V6 can do ?
It's not clear in datasheets.

StarGeezers · Post by **StarGeezers** » Sat 09/11/10 8:25 am

The ones I'm using are specd' at 250V .. maybe a little more , but not like how I torture my JJ 6V6s with around... 400v

kleuck · Post by **kleuck** » Sat 09/11/10 11:11 am

Thanks, i have 6P1P-EV, but the ratings are the same, no way to use it at 350 in place of a 6V6.

I tried a 6V6 JJ's in a Special 6 (ZP : don't read me

) and actually i didn't like it, i even prefer the crappy stock chinese one !

StarGeezers · Post by **StarGeezers** » Sat 09/11/10 11:31 am

Kleuck, I have the EV's too ... here's the voltages on my 6P1P quad Dog Sled... Voltages :
Antek donut PT
B+ 272V
B+1 260V
B+3 236V
B+4 230V

Power tubes 6P1P ev (4)
Plates 268V
SG 255V
Cath 15V

PI 6N2P
plate 172/171
cath 2.8v

6U8
pin 1 68V
pin 6 92V
cath 1.7v
pen cath 3.9v V

The amp sounds Super at those Vs ( a little high)... Hope that helps !!

kleuck · Post by **kleuck** » Sat 09/11/10 11:41 am

Thanks, i bought them to build a little PP inspired by the 18 watts, (except for the Pi) and my PT with an EZ81 will give me to these kind of voltages
Now, i know it's perfect, thanks.

StarGeezers · Post by **StarGeezers** » Sat 09/11/10 12:19 pm

The Best of Luck on that !!!! I know you'll like the sound...

kleuck · Post by **kleuck** » Sat 09/11/10 4:31 pm

Pt and OT are from an old Hi-Fi amp, built with 6AQ5A.

StarGeezers · Post by **StarGeezers** » Sun 09/12/10 7:43 am

Love to recycler old parts !!! So COOL !!!

Dustpuppy · Post by **Dustpuppy** » Tue 10/05/10 11:04 pm

I just modded an 18w TMB to use 6p1p. These things sound great!

tubeswell · Post by **tubeswell** » Wed 10/06/10 12:06 am

kleuck wrote:By the way, i wonder if the 6P1P can stand high voltages like 6V6 can do ?
It's not clear in datasheets.

Don't know about the 6P1P, but the 6P6S subs quite happily for a 6V6GT in most 300-400V situations AFAICT. I can run them in my reverb unit at 360V on the plates. (Note to Mods - Sorry I know its not an 18Wer - I have yet to build one - but its on my to-do list)

laterider · Post by **laterider** » Mon 10/25/10 9:47 pm

StarGeezers wrote:The ones I'm using are specd' at 250V .. maybe a little more , but not like how I torture my JJ 6V6s with around... 400v

Careful, I've taken out a few JJ's in SF champs, maybe it had to do with the 400v on plates + the 470ohm cathode resistor.

I don't have many of them(NOS), but I really like NOS 6V6 over any of the new production 6v6's. I think that 6V6s are the worst sounding type of the new production stuff....

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Opinions on Russian 6P6S (6n6c) 6v6 Tubes