Note 3)  Tube Curves:  The Sofia Curve tracer, that we used for the smaller tubes, is too small for this tube.  The plates curves are measured  point by point and entered in an Excel worksheet. 

Note 4) This is a heavy power tube, and using it safely means avoid risks. The maximum conditions are destructive limits, which should not be reached even for a short moment. A "maximum possible" working point exists, but we do not specify it, because it is generally not a good idea to try this with any power device,both vacuum state or solid state, when you expect long life and reliability at the same time. We found that if we specify a "maximum" operating point, that in the end some users will try this out. So what we publish here, is the recommended working point, which gives best reliability, optimized sound and safe use at the same time.

Note 5) We specify 2% tolerance of the filament voltage, to indicate here that you should take great care in achieving exactly 5Volts. With DHT vintage tubes, you will often see only the filament voltage, and tolerance unspecified. However this leads to a classical misunderstanding that in such a case one can choose 10% tolerance, which is not so. For this reason we specify 5Volts, and it is best to stay within 4.9 ...5.1 Volts. So that means 2%.

Note6) When using a slow-start circuit for the filament, you may not apply plate voltage during that time.

Note7) Gold Grids is a word generally used for gold plated grids, so not gold wire grids. The grids we use are made of specially purified hard metal, which is then thermally gold plated. The advantage of gold plated grids is better temperature stability, and lower grid current if the tube gets very hot, and (within limits) it protects the tube from overheating damage and gives some self repairing effect after accidental overheating.