As everyone who’s tried to buy one knows, power transformers for tube projects can be expensive. Even small transformers for small projects. But today I stumbled on a great deal for a small preamp power transformer made by Hammond.
Continue readingWith the return of some more normal weather here I got the chance to work on the SET chassis today. Specifically I got the bare copper plates chemically treated for the patina for which I was looking. They look good. Or, more accurately, they look just the way I imagined when I first thought of doing this. I’m very happy with the results.
Continue readingSince I first introduced the concept for the “Universal Preamp” over ten years ago on the DIYAudioProjects forum, there has been almost constant discussion of my decision to place the volume control on the output of the preamp. I have been asked questions about it numerous times over the years. I have also had some “spirited discussions” with some who vehemently disagree with that design decision. Well, I thought it was high time to explain that decision once and for all, and to discuss exactly what this configuration means for preamp performance and output impedance.
Continue readingAs I was going through some things today I stumbled upon an email discussion I had recently on the topic of toroids (i.e. toroidally wound transformers and inductors) and shorted turns. Given the popularity of toroids, and amount of misinformation floating around on the internet on the topic of shorted turns, I thought that a short discussion of the phenomenon was in order.
Continue readingThe weather has finally returned to normal here and I got to spend a little time in my shop today. I decided that I wanted to be able to finish the base of the SET and my new triode test jig at the same time. So I needed to get going on the test jig base.
Continue readingI have added a side bar widget on the Blog page labeled “ARTICLES OF NOTE”. I decided that rather than having links floating all over the posts and comments, when I found something of interest I’d post the link in this block.
The first item is a web page from the Lampizator site discussing Audio Heresy. I found it fairly humorous.
With my shop temperature hovering around 38°F (≈3°C) and with the outside temperature hovering around 20°F (≈-7°C) I though that today might be a good time for a little “inside” amplifier discussion. And today’s discussion is about SETs; BIG ONEs.
Continue readingOne more thing concerning Front Panel Express; with a tie in to the SET project. Just as an experiment, last night I opened Front Panel Designer and duplicated my 6AS7 SET top plate design. Now that I’m familiar with the software it took less than an hour to complete.
Continue readingWhen I talked about designing the Dual Triode Test Jig in the “More on Tube Testing” post I mentioned an indulgence. Well the results are in.
Continue readingWe’ve had a chilly rain/snow mix today at CascadeTubes so it’s a little too cold to work on the SET chassis in my unheated shop. Instead I’ve been thinking about my new triode test jig and have been going over the tube list that it covers. There are lots of tubes on the list with which I am not intimately familiar so I’ve been pulling data sheets and doing some investigations. And I’ve received some pleasant surprises!
Continue readingThe discussion on tube testers and their usefulness (or not) got me thinking about my own tube testing needs and how I go about it. I already have a solution for octal power tubes with the 7S base pinout which I’ve mentioned before. But what about those ubiquitous signal triodes I seem to use in almost every project? What should I do about them?
Continue readingSo I’ve been playing with the copper tarnish/patina process and I think I’ve got it figured out. After doing lots of small parts with various approaches I’ve learned enough to start the amp pieces. Among the things I’ve learned is that the washing process both before immersion in the chemical bath and after tarnishing while washing off the chemicals is very important. I’ve also learned that an even buff with a steel wool is better than taking the copper to a high gloss shine. And finally, the initial tarnish is very fragile. After doing the bath and letting the piece dry, it really should be left sitting in the open air for between three and five days. After this, the oxide layer toughens up and it can be handled and clear coated.
Continue readingAs I mentioned back in June, I have been looking at different finishes for the copper portions of my 6AS7 SET amp. At that time I had mentioned that I was interested in a “patina” type finish for the copper. I learned that to many people copper patina means green tones, blue corrosion, and wild colors. I was looking for something more like a tarnished penny look. Something that would make the unit look more like an older piece of equipment. Unfortunately this was to be more involved than I first imagined.
Continue readingI get a lot of questions from people looking at my website. Most questions are about the posted projects or requests for recommendations for test equipment. However a topic which comes up regularly is about vacuum tube testers. The questions range from simple a “Should I buy one?” to complex requests for information on types, operation, “accuracy” and the ever present question “Are they worth it?”. Unfortunately, the topic is actually much more complex that most people realize.
Continue readingI took some time yesterday to perform a performance check on the driver for the 6AS7 SET. As some may recall, this driver was developed and prototyped back in 2015, and brass boarded in 2016, as a driver for the 6336 SET Amplifier. In the 6336 design it uses a 300v B+ to produce a swing of 82V peak to fully drive the big triode. However, in the unique power supply topology of the 6AS7 SET, there are some additional considerations.
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