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.
When looking for the materials to get the new amp going, I quickly learned that I needed to get new output transformers and a main filter choke. So I made an Edcor order and they returned my new iron in record time. I talked about it in mid-April while discussing the SET. But what I didn’t order was a power transformer.
When initially doing the design, I was going through my parts closet and happened upon a power transformer which I purchased almost five years ago for another project. Since that project had not taken shape, and I had already used the power choke for that project in my new 6AS7 SET, I decided to use the old power transformer in the new 6L6 SE-UL. The only issue was that the secondary voltage was a little high; 800 VCT. But I figured that, since I wanted a 400V B+ for the 6l6 SE-UL, I could make it work.
Well, today I have thrown in the towel on using that transformer and have ordered an XPWR178 with a 660VCT secondary. This transformer, using a 5U4GB rectifier, should come fairly close to supplying the required B+. And the best part is I can safely build the power supply using standard 500V filter capacitors which are readily available. The other transformer was going to require some esoteric parts in the power supply.
I have a top layout almost complete for the amp (albeit with the wrong power transformer) but I am going to hold off doing any more physical layout work until I have the iron in hand. I can however start work on choosing chassis materials. I have some really nice spalted alder that could provide a really striking look for the amp. I’ll have to spend some more time on that aspect of the design.
As always, questions and comments are welcome.