12BY7 as a low watt output tube

[RiverRatt]

I built a little amp a while back. I got it working and put it aside. I got it out this weekend and got it dialed in.

It’s a tweed type SE circuit, and I used a 12BY7 pentode. The 12BY7 is used as a driver tube in ham radio gear. It makes a pretty sweet output tube. I guess it sounds more like an EL34 than anything else. The tone stack is called Ray Bone. It has a Treble and a Warp control.

I used transformers that I had pulled from audio gear, and the PT was pretty low voltage. I had 157VDC on the plate, and 132 on the screen. The cathode resistor was 50R with a 50uf bypass cap. I played around and came up with a 470K grid leak resistor.

I would really like to hear a pair of them in push pull. The SE amp I built is fairly loud for what it is. I’ll definitely keep this one around but I want to build something with a 1987 preamp and two output tubes.

 

[mickeydg5]

Interesting.
That tube can handle 250V+ and has a multiplication factor of like 28.
Expensive little tubes to mention.

 

[Chappy]

6AK6, El91/6AM5 are other options for low power pentode tubes. A 5W JCM 800 style build using these tubes is next in line on my project list. 6V6s output tubes with an attenuator will be my backup plan.

 

[RiverRatt]

There are countless choices. I have so many sweep tubes to try that I’ll never get around to trying them all. One that really worked well was a 6CM6. It sounds like a big bottle tube. I think Guitar-Rocker is working on a push-pull 6CM6 amp. I also have some RCA black plate 6DQ6 that I want to use in a Blackface build. They are really nice looking and that top plate cap is just too cool.