Introduction
This was one of my first DHT preamps. I found a quartet of NOS CX-112a Cunningham (globe) back in Buenos Aires many years ago and built one of my first DHT preamps. I loved it. I played with it before I moved into the 26 and then started the long exploratory journey with DHTs.
The CX-112a can be easily fit in an existing 01a preamp. Take a look at what Thomas Mayer recently blogged about this valve, worth reading it.
Well, you can get more current drive than 01a (nearly double) but no thoriated tungsten filaments. Anyhow, the gain is slightly higher but is very easy to adapt to my gyrator-based circuit, that I couldn’t resist to take the quartet out of my valve stash and make them sing again after so many years.