It was a slow weekend, but I started on the metal for the monoblock pair of V-75’s.
Achievement Unlocked: 75 Watt Class A Zero Feedback SIT Circlotron
Because of the high input capacitance of the 2SK180’s and the gain of this circuit, we have to pull out all the stops to get our 75W beast to make audio bandwidth. Here you can see that each SIT is getting its own transformer and buffer.
Here’s the 75 Watt V-FET prototype on the bench. More wires than Keith Emerson’s Moog! Edit: Just a few days after I wrote that caption, Keith Emerson passed away. RIP Keith. Thanks for all the music.
Here’s the THD at 1W and 10W
Here’s the simplified schematic for V-FETRON. There’s a 20 Watt version and a 75 Watt version. I think I’ll give them clever names like: V-FETRON 20, and V-FETRON 75. The 20 Watt amp uses either 2SK82 or 2SJ28. The 75 Watt amp, created for our friend Tim, uses 2SK180. I have a few more transformer types on order to evaluate, then I’ll let you know how I addressed some of the various issues involved. Muhahahaha, more later.
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I’ve always wanted to check out Moogfest. I’d like to try to make it there this year. Sounds like fun. Maybe throw in a side trip to Kitty Hawk.
More info at: www.moogfest.com
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