Help me mod my tube amp

Thanks, nlitworld, for those additional suggestions. I will check out the binding posts and wire you mentioned.

Mike B-- Thanks for your observation about the different directions this thread has taken. Both kinds of input are valuable to me. I've used Mullards (can't remember which ones) for signal tubes in the past with this amp and liked them. I think when it came time to replace them, I cheaped out. But I've been taking more of an interest in this secondary system lately, as I spend a lot of time in that room. So I will rethink my former frugality. To my knowledge, I have never heard Winged C 6550's. Do you have the same positive opinion about other 6550's?

Thanks also, Mike B, for the suggestions regarding resistors and capacitors. I have been internet researching potential replacements. Although I have modified preamps and speakers myself in the past, I am going to hire someone to do these modifications.

Mullard Vs Telefunken is kinda like Chocolate Vs Vanilla. It’s personal preference within a particular system. I tend to put 6550’s and KT - 88’s in the same group. I compared the Winged C’s to NOS Tung Sol 3 hole 6550’s and the Svetlana’s were considerably better. I’ve used the Winged C’s in EL 34, 6L6 and 6550, they ALL absolutely rock. I really hate to see them go away. I have KT 66, KT 77, 6550, KT 88, KT 90, KT 120, and KT 150. NOS tubes are GEC KT 66, KT 88, and Tungsol 6550. The GEC’s are a little light In bottom end, but the mids and uppers are fabulous. The best way I can describe the Winged C 6550’s is that they have bottom like Tung Sol KT 120’s and mid/high better than new GL KT 88, but not quite GEC KT 88. Out of ALL my power tubes the Winged C’s are my favorite. They are pretty much unobtainable and the ones at the end were factory seconds. In the beginning they were consistent, graded and reliable. At todays prices Primo 6650’s are worth $200 each. This week I’m breaking in an octet of Psvane KT 88’s, but will probably need to buy an octet of better quality Tung Sol KT 120’s for my project. Unfortunately the cost delivered from Upscale is $1100. I’ve seen a few Winged C EL 34’s for sale and maybe 6L6, but the 6550’s are flipping rare. I’m down to a shoe box of loose, test 80% 6550’s. Disclaimer, I’ve never tried Sovtek power tubes. Happy Hunting , Mike B.

I would add output transformers to try.. Luxman/Tango/other good-ones.. 

I would be careful on trying to find genuine-matched NOS tubes. number of NOS offered these days exceeds former production!