It’s been really hectic for me over the last months. You will notice that I’ve not posted anything on this blog. Moving house and running a house renovation project whilst doing your day job is tough. Despite all this, I managed to set up a temporary lab in my new place. Yes. The system is running and I have also a workshop (or kind of).
I finally received my production pair of ELROG ER801a valves. The arrived safely and sound, however when I submitted them to the mercy of the valve curve tracer, I struggled to measure one of the valves as presented a suspicious short in grid and I suspected it has been damaged by the post service. I rarely had an issue like this, probably 2 or 3 times over more than 10 years. Anyhow, the valves were sent back for replacement. This shows the great service you get from Thomas, not many vendors will provide this insurance as part of the product cost.
Update: Thomas Mayer re-tested my valves and found that both were working fine so he just sent them back. I need to look at whether there was any socket-related issue on the e-Tracer. A bit strange as I’ve been using it for a while and only found the measurement issue consistently with this one valve. Therefore my conclusion was that it was damaged.
Either way one of the valves was in perfect condition, and it measured extremely well. I wanted to share with you the curves plotted using the eTracer, which with its latest software released has gotten better and better and is worth every single penny:
You can see on the image above, that it measures really well at about 102%. I will produce a Spice model from these curves when I get the chance.
Here are some interesting curves using the same data set:
Here are the transfer curves (anode current versus grid voltage) for a varied set of anode voltages:
These are useful in high-gm devices when used in a cascode topology but not for 300B. You can see the linearity of the valve at various operating points anyway with this set of curves, so they are useful anyway.
Here is an interpolation of the transcoductance (gm) for various anode voltages when varying the grid voltage:
You can see on the above the variance on gm for the transfer curves data.
Enjoy the summer. It’s pretty hot here in London so I don’t complain at all.
Cheers
Ale
Hi Ale, I think you have built a uTracer in addition to the eTracer haven’t you? Any thoughts on how these compare? I’ve been thinking about building a tester rig for my own projects.
Hi Tim, there is plenty of info on both tracers out there. The uTracer is cheaper but you need to build it yourself. The uTracer comes with a tested PCB so much less work. If you’re not experienced enough, this isn’t a project to get your hands into.
The eTracer has wider voltage and current capabilities and the software is constantly under development. A great asset in my opinion.
Hope this helps.
Ale
I updated the blog entry as it seems my valves were in good condition after all. Thomas has posted them back to me so I will report again as soon as I receive them. I’m keen to listen to these valves again on my line stage.