Lots of work has been going on the last couple of days working on an alternate buffer design for the 12AU7 “Color” preamp. As readers should know, I was not particularly pleased with the performance of the previous buffer circuit. It was bottoming out at too low a voltage. Now however, I have a simple change which yields much better results.
Continue readingThis afternoon I completed the “color” preamp and tried it out. I am very happy with the results.
Continue readingThe “Color” preamp has been checked out on the test bench and everything is working per design. Bias points are good and the gain stage is operating exactly as designed. However, the buffer design I used was from a different project, and it operates differently in this project than the last one.
Continue readingI had thought that the coupling capacitors I ordered on Tuesday would not arrive until this Saturday. However, the gods of DIY decided to smile down upon me and the capacitors showed up in today’s mail delivery. In my opinion, two days from order to delivery is exceptional. I spent some time this afternoon with a soldering iron in hand and the Color Preamp is now fully assembled.
Continue readingAs you may know I’ve been waiting on components to finish my “Color Preamp”. I thought that I’d have my output coupling capacitors by now, but I was mistaken. It seems that my parts supplier, after promising to get the parts right out to me, spent three days trying to find the parts in their warehouse, then sent me a refund. But I thought I’d outsmarted them.
Continue readingSince I’ve been at a standstill waiting for parts, I’ve been going over my parts supply and getting things organized again. It seems we’re all constantly working against entropy. While doing this, my bagged and sorted capacitors reminded me of a short article I wrote back in 2013 about component tolerances. I’ve decided to reprint it here for reference.
Continue readingI made significant progress today. Most of the signal stage wiring is done. I could finish it up in about half an hour, but there are two little blockages in my path; one due to a supplier problem, one due to me.
Continue readingI’ve been working on the color preamp over the last few days as I’ve had time. My volume control and output capacitors are supposed to arrive today so it shouldn’t take too much longer to finish it up. However working inside the small chassis is a challenge.
Continue readingSince I’m still waiting for appropriate weather to finish the 6AS7 SET chassis, I’ve been making progress on a small project for the aluminum chassis from the last post. I decided to put together the “Color” preamp from the post a few days ago. This project will make use of one of the Hammond discount power transformers about which I posted a couple of weeks ago. It’s coming along well, but VERY slowly.
Continue readingWhile waiting for appropriate temperatures to paint and apply oil finishes, I’ve been working on a simple preamp project. It’s only a handful of parts and to avoid complications with finishing a handmade chassis, I decided to use a preformed aluminum project box I had sitting on my shelf. I quickly regretted that decision.
Continue readingFor a while now, ever since the “Universal Preamp” was posted on the site, I’ve been getting steady requests for a good tube preamp to provide some color to solid state amplifiers. My initial answer to this problem was to design a good quality cathode follower for the Universal Preamp. There was one problem, the volume control.
Continue readingIgnoring the wood chassis for the time being, I made significant progress on the triode test jig today. I just thought I’d post a quick update. Parts are now mounted and some wiring is underway.
Continue readingI’m working on two projects simultaneously right now; the 6AS7 SET and the Triode Test Jig. In the last couple of days I’ve made progress on both. However now I appear to be at an impasse.
Continue readingIt’s been a tense couple of days waiting for the patina to set on the 6AS7 SET top plate. But I just placed the copper on the chassis and it looks great!
Continue readingRegardless of how much planning you do and how many test runs you accomplish, sometimes things simply don’t go as planned.
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