Replacing 7199 with two octal tubes...

[knockbill]

Mine are metal,,, they aren't as pretty as GTs, but I like the ease of grounding the metal shield for noise suppression,,,

 

[Lavane]

I grounded the metal RCA 6J5's I used. After a little time running they can give you a little buzz without grounding. They were quiet in my first 300B though.

 

[Pio1980]

I used a 6N7 in the 6AS7PP amp I built, it really sounds good, uses a pair of Pioneer OPTs I salvaged,,, man those 6n7s get hot!

It should, with the 6N7 heaters drawing 0.8A, so be sure the power transformer can handle the current.

 

[battradio]

I used a 6N7 in the 6AS7PP amp I built, it really sounds good, uses a pair of Pioneer OPTs I salvaged,,, man those 6n7s get hot!

https://frank.pocnet.net/sheets/049/6/6AS7G.pdf

Not as hot as the 6AS7 they put out about 17 watts of heat from just the filaments .

 

[knockbill]

It should, with the 6N7 heaters drawing 0.8A, so be sure the power transformer can handle the current.

I have a separate FT for the output filaments... so the 6SL7s and 6N7s are on the PT...

 

[arts]

It should, with the 6N7 heaters drawing 0.8A, so be sure the power transformer can handle the current.

This is why I have always been on the lookout for a glass version of this type. I'm really curious about the innards.Pretty ballsy tube for it's size.

John-If you want a more ''vintage'' look,the 6J7 is identical in spec to the 6SJ7,but has the grid brought out to a top cap.

 

[knockbill]

I have found some GTs for certain metal cans,,, 6SJ7 for one I believe,,, however the innards are surrounded by a plate, so you can't really see in... The metal cans don't bother me,,, as long as they sound good, and are quiet!

 

[gadget73]

that was the idea initially. Do away with the metal shields clipped over the tube, each one comes with it's shield built in and easily connected to a solid electrical ground through a pin on the base.

 

[knockbill]

Yep... they don't show too much "light out" with the shield inside,,, and metal ones are a dime a dozen... fits my budget well!!!

 

[Pio1980]

I have found some GTs for certain metal cans,,, 6SJ7 for one I believe,,, however the innards are surrounded by a plate, so you can't really see in... The metal cans don't bother me,,, as long as they sound good, and are quiet!

These high gain small signal pentodes have a surrounding internal shield, usually connected to the cathode as assumed signal ground.

 

[arts]

that was the idea initially. Do away with the metal shields clipped over the tube, each one comes with it's shield built in and easily connected to a solid electrical ground through a pin on the base.

Not to mention speed of manufacture.Imagine how many of those envelopes you could stamp out per hour? In the end glass won out on cost and better cooling,until the Nuvistor came along. I have always wondered why the ''Octals'' never rapidly evolved into more sophisticated types using the 11-pin relay base,and why development took so long (relatively speaking) for the Compactron style tubes.

 

[gadget73]

possibly there just wasn't a need for more pins in a package until TV use really started to drive it. In the early days they used to sell radios on tube count so there was little incentive to have multiple in one bottle. By the time of the TV era nobody cared about count, and somewhere along the way space limitations drove the multi-element tube requirements. As for the octals, probably just more expensive to make vs pins directly in the glass.

 

[Pio1980]

Octals date to 1936 to replace the keyless prior fat pin tubes, 8 pins was enough for the complex single end pentagrid converter. I suspect the General Electric PortaColor TV project was a major driver for the Compactron multi-function tubes.
https://en.m.wikipedia.org/wiki/Porta-Color

 

[dewdude]

No need for adapters,,, this is an octal tube project,,, using what I got!!!

Well one could just rewire the socket to take a 6U8 without an adapter.

Just seems like a lot of headache to re-engineer a circuit and spend a lot of extra time when you could move some wires and not have to do chassis modification.

 

[gadget73]

The chassis he's using already has octal sockets.

 

[knockbill]

Re-read the 1st post, no 9pin tubes/sockets involved, except on the schematic I'm considering,,, its an octal chassis project...

 

[maxhifi]

Late to the game here.

I would use a 6J7, and a triode connected 6J7. A triode connected 6J7 is more or less a 6J5, RCA used to do this all the time in their designs. This way you can swap the tubes around to get the quietest front end.

Note: the 6J7 has better characteristics than the 6SJ7.