Transformer

I was looking at the new power transformer from Edcor for the latest project today. This is the one I talked about in my posts Failings of Memory and Weirdness with Edcor Order. I noticed a change in the new transformer. However this change I consider an upgrade.

There was one thing about my Edcor delivery today which surprised me a bit.

Lately I’ve been looking at a revised amplifier design based on the Marblewood project. The intent of the redesign effort is threefold. First, a different and more widely available rectifier tube. Second, an improved, if slightly more complicated, power supply design. And third, some potential improvement in the low frequency response. As it turns out, you can’t always get what you want. But also, two out of three ain’t bad.

When testing an amplifier, the first thing I generally do is to check voltages. This is what I advise others to do as well. However, the real trick is in determining if the measured voltages are acceptable or not. And herein lies the difficulty.

I guess that some folks have been wondering what I’ve been up to the last month or so. Well, I’ve been trying to take it easy to let a shoulder injury heal. If physical therapy can be considered “taking it easy”. In the last month I’ve learned all about labrum tears. However, today something arrived in the mail and that means it’s time to get back to work.

As I said the other day, “It is my estimation that the EL84 would greatly benefit from a lower percentage UL tap transformer.” Whereas there is much to be learned from the current data set taken with the Edcor GXSE10-5K transformer, I have decided that a different configuration needs to be tested as well.

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

When looking at schematics and builds of vacuum tube amplifiers employing output transformers some people notice a curious inconsistency. On some amplifiers, the output (i.e. secondary) side of the transformer is grounded, on others, it is not. This can lead to a dilemma for amplifier builders: To ground, or not to ground? Luckily, there are some simple guidelines which will almost always yield the correct answer.

So I’ve had an experience recently that surprised me a little. And I’m wondering if this is what other people are experiencing.

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

So I’ve been reviewing EL34/6CA7 data sheets preparing for an EL34 SE-UL optimization study like the two I’ve done before for the 6V6 and 6L6. However, I’ve run into a little snag.

This morning the power transformer for the 6L6 SE-UL arrived from Edcor. And even more importantly, I’ve got the spalted alder converted to dimensional boards. Now I just need to select what goes where and I can begin milling the chassis.

The gear switching I’ve been doing on this rainy afternoon has been putting the 6AS7 “Purpleheart” SET in the “finished” column of the ledger and getting to work on the upcoming 6L6 SE-UL amp. And I’ve already run into a delay.

About 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.

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.