I managed to make good progress on the assembly of the 6AS7 SET today. In addition to getting all the hardware and iron mounted in the chassis and on the top plate, I’ve actually started wiring.
Continue readingI managed to eke out a little time to work on the 6AS7 SET top plate this afternoon. I didn’t get a lot done but at least I’ve finally started.
Continue readingAfter many delays and distractions I have finally finished the 6AS7 SET chassis and have begun assembly.
Continue readingI currently have a couple of major projects on the workbench and a few other minor tube circuit investigations underway. When this happens I find myself pulling things off of shelves, moving other things around, and generally creating quite the mess until I’m having problems finding just about anything. When this happens I generally step back and take some time to get everything organized again. But this time, I wasn’t quite prepared for what I found.
Continue readingIt’s been a productive few days. Two different amp projects are coming along nicely and today I’ve reached a milestone.
Continue readingThese last few days I’ve been working on the driver stage and overall schematic for the new 6L6 SE-UL amplifier. While drawing up the schematic yesterday, I inserted a 250kΩ volume control at the input without much thought. While performing some preliminary analysis, I realized my mistake.
Continue readingFor the last few days I’ve been applying oil to the SET chassis. It now has four coats of oil, cured and buffed out. There’s only one decision left for the chassis.
Continue readingToday I was once again reminded of the perilous state of human fallibility and the risks of personal hubris. The cost of today’s lesson? One ruined KT-88. And a little smoke in the office.
Continue readingThis morning as I sat down in my office to check email and the like, I looked over at the amp in the corner of the room and made a snap decision. It was time to perform a SET swap.
Continue readingThis afternoon I’ve been working on another amplifier project. This particular one is the 6L6 SE-UL for which some readers have been looking since I published my Optimization of the 6L6 SE-UL page back in March of 2019. I recently realized that it had been three years since I published that data set and that it was probably time for me to get the project started. So this afternoon I’ve been investigating driver stages for the amp.
Continue readingIt looks like the weather has finally broken here at CascadeTubes and spring has arrived. Yesterday, the 6AS7 SET chassis got its first coat of oil. The purple heart used for this chassis is definitely much deeper in tone than that used on the The 6DJ8 Headphone Amp.
Continue readingAbout a year ago my television display died and I was forced to buy a new TV. I had been using the Lacewood V2.0 amplifier for the sound system and, when I plugged in this new TV, it formed a bad ground loop with the amplifier, introducing a nasty hum. This was not an insurmountable problem. I simply dug through my parts closet until I found a little line isolator I had built about a decade previous for some project I was working at the time. I installed this isolator and the problem went away. But that’s not the end of this story.
Continue readingI took some time this week to get several coats of oil on the chassis for the Dual Triode Test Station. Even though I’ve already used it for the mystery tube investigation and to compare some 12AU7s, it’s good to have it finally complete.
Continue readingI spend a lot of time experimenting with various vacuum tubes circuits. It is a past time which I really enjoy. It also gives me an outlet for my creative tendencies when the workshop is too cold to make custom furniture (and amplifier chassis). As a consequence I have amassed a fair amount of test equipment and miscellaneous cables, adaptors, probes, and other odds and ends over the last decade or so. And regardless of the fact that I want to concentrate my attention on my vacuum tubes, sometimes it’s the other things that demand my attention.
Continue readingBack in November, in my post concerning Tubes and Tube Testers, I talked about how I was not really a fan of generic tube testers. In that post I sited a statement from the RCA “Receiving Tube Manual”, RC-30, about testing tubes.
The tube tester cannot be looked upon as a final authority in determining whether or not a tube is satisfactory. An actual operating test in the application will give the best possible indication of a tube’s worth.
So I thought that as a simple demonstration I would collect some data from a couple of tubes; one new and one rather ‘used’. The results are really kind of surprising.
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