Flying around
Travelling around Europe on business is paying its toll. I’m away from home every week and pretty exhausted now. I don’t have much time free and whatever is available I spend with my family. Hence, the lack of posts recently. I hope this will change in the future.
Anyway, what’s up in the DHT world? I listened the Aa/Ba valves long time ago but never played with them. Mainly due to their higher anode resistance. With the gyrator load and the source follower output, things take a different dimension.
German precision
I have a nice stash of Aa from Valvo (globe) and Ba from Siemens. Interesting to see that curves are not easy to find, so I submit them both to the mercy of the uTracer. Nice to see the linear curves with high mu about 14 on the Ba to 30 in the Aa.
Here is an example of the Ba loadline:
With a maximum of 230V running it at about 200V/5mA and -3.4V seems reasonable to provide good headroom.
A simple but yet effective DHT stage
With such a high Ra and low anode current, the marriage with the gyrator load and the output source follower is ideal. I use this with great success on the UV-201a preamp which sounds amazing.
The circuit is dead simple as I have implemented this before again and again. If you need like 22dB of gain in your system, then look into this option. I have to implement to see how it sounds, and I guess it would be great. The Ba has a high reputation as well as its predecessor Aa.
Stay tuned
Hi, Ale Delving into new territory yet again eh? At least for most North Americans the Ba tube is new territory one would think. So, Bravo! Ale. And Thank You. -Edward