Power-Supply

After several false starts, and a couple of minor reshufflings, The power supply side of the new amp is complete. Now it’s time to finish up the actual amp stages and get the top plate on the chassis.

I carved out some more time to work on the amp today. I managed to get the entire power supply section wired in.

Having performed the investigations I wanted on the gain stage on which I was working, I then moved on to another part of the project. And the chaos from a couple of days ago was nothing compared to yesterday.

Have you ever made a mistake? Not a typical everyday little mistake like forgetting to run an errand, but a blunder of such proportions that you’re shocked by your foolishness? One that leaves you thinking you couldn’t have been that naive, that foolish? Well I did. And it left me with significant embarrassment, as well as some smoke coming out of an amplifier.

Please read the post “That Didn’t Go Well!” before following the power supply change detailed in the later half of this post.

Sometimes a design which seems fine at first can later exhibit some marginal behavior. This exact issue recently reared its head with the design of the 6L6 “Spalted Alder” amplifier.

There is truly nothing like the smell of a freshly wound transformer.

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.

I’ve finished modifications to my test jig to allow the testing of the 6BQ5/EL84. It’s really a shame that so few other 9-pin power pentodes use the 9CV pinout. The 6CW5/EL86 is the only other really common one.

So as I said in my post The Next Amp, I kind of settled on the triode strapped KT88 based on the power supply. Now I’m not so sure.

So I’ve been thinking about my next amplifier project. And I thought I had made up my mind. Then things changed… again.

I made some progress today on the Source Selector Unit. The twelve twisted pairs are all soldered to the selector switch and I managed some chassis wiring as well.

Today I took some time to install the signal ground bus and wire the transformers. But I also wanted to discuss a specific aspect of transformer wiring for the B+. I often get questions on this topic from people looking at the 6336 SET Amplifier. Let’s take a look.