Hey kids... here's another one for you that is well off the map. This a small globe beauty from England. It is a directly heated triode, and fairly high transconductance for a DHT. Mu is neither high nor low, at about 15. However, you can easily load it with iron as the plate resistance stays below 5k at typical currents.
With those specifications, it is also like the Sparton 485 in that it does not have an obvious place in a typical audio chain. It needs a bit more gain to be a driver tube. It needs a bit lower plate resistance to be a line stage tube. But it sounds so good that it can often find a home in either of those places. I loved it as position two in a phono stage. At the moment it is happily sending signal from my vintage strain gauge to my volume control. DHT strain gauge is quite nice!
Unfortunately, it is one of those that you have to by more than a few to get a matched pair. I do not believe it was made in even moderate quantity as they only show every other month or so on eBay.
so, here are some photos:
(If anyone has any they want to barter, I am open.. else build with them!)
Retro Hi-Fi Girl Friday - http://www.itishifi.com