Hey All,

Long time fan of the YouTube channel, first time poster. Anyway, I started this project a while ago. I finally have it up and running. It's a headphone amp version of the 6SQ7/EL34 amp. I worked with thermionic labs to get some custom output transformers to work with the original design. For the most part I stayed true to the original design but added/changed a few things.

-Lowered the bias of the power tubes to 50mA from 60 mA. The transformers could only be gaped for a max of 60mA, so I changed the cathode resistor from 500 ohm to 600 ohm to avoid running the output transformers at their max.

-The output transformers have the ability to run a couple different output impedance's on the secondary. I used a gold point switch to have the ability to select between a 32 0hm and 150 ohm tap. This makes it great for both low and high impedance headphones.

-Added a triode/UL switch.

-Added a switch to turn the plate to plate feedback on/off. I found triode sounds great with no feedback, while UL sounds better with it engaged.

Thermionic labs actually has the output transformers I used as a stock option now in case anyone has any interested in building a similar amp.

Big thanks to Steph for making all this info/projects available!