Prototyping

It seems I’m nothing if not predictable. I’m just really getting going on the assembly of the Marblewood upgrade amplifier and I’m already doing design work for another project. This is in addition to the two other amplifiers which are already in the queue.

I have the initial set of data with the power supply prototype using the Edcor XPWR011 power transformer. It is enlightening and clearly shows which amplifier I need to build next.

Be sure to look carefully at the environment where you do your work. Failure to look too closely may result in you sacrificing time and effort to the gremlins in the machine. At least that’s what just happened to me.

One of the risks of becoming too familiar with vacuum tube electronics is that it’s easy to become a little careless when working around high voltages. And because of this learned carelessness, sometimes we don’t take as many precautions as we should. Especially when prototyping.

For those that are paying particular attention to my amp builds it will come as no surprise that I think the #44 and #47 (0.9 and 0.5 candela respectively) indicator lamps are a little bright to be used on tube amps. I just think that they tend to overpower the look of the amplifier when the room gets dim. However, as these lamps are ubiquitous, it pays to use them in our builds. So, on the 6DJ8 Headphone amp and the 6EM7 vertical amp I included a small adjustment potentiometer to tame these power indicators. And on the Marblewood amp, I chose a fixed 25Ω 1W resistor to dim the indicator.