Suggest Tubes for a New Project

[The New Steve H]

I got my 4-6bm8 Bassman-based Wingman amp running. It sounds great, but I am still tinkering. I'm going to put a bigger PT in it to see if the sound can get any better, but if it doesn't work, I'll have a PT I can use for a new project.

Can anyone suggest output tubes for a 5F6A-style amp, with a PT wound for 270-0-270 and 250 mA? Four tubes or two tubes; makes no difference to me. I like a warm, clear sound, like the 6L6s in the 5F6A.

[Jana]

It's too bad you don't like 6V6 tubes--that would be perfect for a quad.

[Phil_S]

I've been told that the Russian 6P3C tubes get a bad rap because people try to run them at impossible high voltages. I think what you've got in a PT is probably just about right for them and they are dirt cheap. This is a "cousin" of a 6L6. If you can get the voltage down into the right range, maybe use a real 5Y3 (should give you about 300V) you might hit the sweet spot for running a pair in PP class A.

[The New Steve H]

Weird Russian tubes? Might be fun.

[Phil_S]

No so weird. Same pin out at 6L6 and very similar. I got a box of a dozen a while back for $36 shipped, but haven't got anything to plug them into. Sooner or later I'll build a fixed bias amp that will allow me to at least test these tubes. I've also got an odd lot assortment of 5881 and real 6L6 tubes that I'd like to "evaluate" as well. Anyhow, I diverge. My point is, you can have some fun on the cheap. If you don't like the tubes, you lose very little and you can always get some real 6L6/EL34/KT88 or other pin compatible tubes as long as there is enough filament current available.

[tubeswell]

The 6P3S should only be run on low voltages. They quickly fizzle over 400V. But they make a great substitute for a 6V6 albeit with a halved load resistance (if they are run at around 340-350). The plate structure is similar/same to a JJ6V6S.

On the other hand the 6P3Se - with the wafer thin black base - (designed as a 20W tube but can be run as a 25W or even 30W tube) is an awesum toob and can run comfortably at 460V - made to go in soviet ICBMs. http://www.rutubes.com/index.php?productID=177

http://timelesson.blogspot.co.nz/2010/0 ... trode.html

http://www.tubes.ru/techinfo/HiFiAudio/6p3s.html

[Phil_S]

Fun with Russian tubes. There can be some confusion in translating the Cyrillic. I think there are two tubes under discussion here. Frankly, I'm not sure, so I'm asking. See the attachments.

The tubes I've got are labeled 6Π3C and I am reasonably sure it is the PDF I posted for 6P3C. However, the Cyrillic "C" is usually translated as the Roman "S". I think maybe these are the same thing.

[212Mavguy]

6bg6ga...depending on the maker, these are repinned 6l6's. Wonerful sounding. The sylvanias are same as their 7581a's in the guts, 35w rating. personal faves are GE blackplate, think but not positive those are 30w tubes. They are one of the most musical output tubes I have heard, and the Sylvania, bigger bottom and brighter top, also very musical. The Sylvania can rarely be found with black plates. Inexpensive. When was the last time a pair of Sylvania vintage 6l6gc's could be had for under a C-note? A pair of the 6bg6ga's can set you back 10-25 bucks a pair. Adapters can be found on eBay. I have had a lot of time running these tubes in D-clone amps and they are spectacular in that circuit type. Can't be beat IMHO for the vintage 6l6 sound.

[The New Steve H]

Won't it be impossible to get the required B+ from a 270-0-270 PT?

[gingertube]

I noted the above about you not liking 6V6.

Have you ever tried a quad of 6V6 - you still get a bit of that 6V6 grind but it is MUCH smoother than a pair. That would be my recommendation.

A couple of other tubes you could look at:
Electroharmonix is now producing 6973.

Other modern production "re-issues" that are now available include the 7868 which was used in early Ampegs and was apparently a great juke-box tube.


Cheers,
Ian

[212Mavguy]

Won't it be impossible to get the required B+ from a 270-0-270 PT?

At first blush, no. great question. In this tube type wattage ratings vary, basically depends on the guts inside, some have 6l6gb 22-25-ish watt guts, others' guts are gc/7581a 30-35 range, depending on manufacturor.

The "lower wattage" black plate tubes RCA made in that type have the getter flash close to the base instead of higher up on the sides or near the plate cap. The plates are mounted very high in the bottle compared to other designs. They have the godly, sweetly detailed RCA blackplate 6l6 family tone in a lower wattage package. They would be happy with that kind of PT voltage IMHO. You might be able to bias the higher wattage tubes up into class a-ish operating zones without frying them, either. Fender BF tones from these a-gogo.

[The New Steve H]

The amp I bought the PT for is fixed, and it sounds wonderful. I don't need the new PT, so I'm going to have to find a use for it. I'm thinking I might build the same amp again with a bigger PT, just to see if it has more punch.

[The New Steve H]

Now I'm leaning toward 6P3Cs or EL34s. The tubes with the big long name sound risky, since it looks like I would have to count on a perpetual supply of NOS RCA tubes.

[The New Steve H]

It's looking like EL84s. I can't look at one more obscure datasheet.