using twin 12au7, we can do like this.Origin schematics JF1OZL shows us . That is 1992 years , just 30years ago.Sure doing well as JF1OZL says. 1.5uV ssg signal, We can hear.
Great work. I have the exact same signal generator in my workshop too.... mine is branded as a Meguro, I think they were made by Leader electronics. A service manual would be handy, have never managed to find one.