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MuFo MoFo

Working on something new for the diyAudio Store today. No, it isn’t a DEF. Close cousin-ish. 🙂

Aw, what the heck.  Here’s the SIT version.  M1 is a depletion part, or even an N-SIT.  The Sony parts are low mu, so negative gain here, but that can be handled on the front end much like a tube OTL.  🙂

Come See Four Amazing Presenters at Burning Amp 2017!


There are four talks throughout the day and will be held at the Firehouse. A link to the schedule is available at

Nelson Pass will be talking about his new amplifiers which diyAudio will sell as kits and should have them to demo along with tons of other cool stuff including the awesome SAL speakers in his audition rooms.

Siegfried Linkwitz will also give a presentation on audio perception, and demo his acclaimed LX series open baffle speakers in his audition room.

Damian Martin will demonstrate the only existing sample in the U.S. of a new precision measurement interface for computers which has unheard of performance per dollar, and a device designed by Jan Did den that automatically sets the input voltage to your computer interface to 1 volt to get the best measurements and not blow it up! He will have them on display at a table in the Firehouse and may do some tests of amps for people to demonstrate them.

Wayne Colburn from Pass Labs will be about his new headphone amp design and the PCB’s he can supply for them and how he approaches some common circuit design issues. He will also have a table in the Firehouse where you can listen to it. Bring your own headphones for the most meaningful experience!

Burning Amp 2017 Coming up!

San Francisco, CA November 12, 12017 — Burning Amp Festival 2017 is coming to the Fort Mason Center in San Francisco on Sunday, November 12th from 8:30 a.m. to 8:00 PM.

BAF’s hours have been extended due to the increased interest and popularity of DIY audio among music-loving enthusiasts of all ages.

Held in the fall since 2007, BAF has grown into a premier international event for do-it-yourself audio enthusiasts and professionals.  DIY audio is the original maker movement dating back to the 1940’s and 1950’s when Hi-Fi was in its infancy, and a lot of great-sounding equipment was assembled at home by enthusiastic amateurs.

BAF celebrates audio technology both new and old, tube and solid state, analog and digital. The festival has been held in the fall since October of 2007.  Come listen

to hand-built audio amplifiers, speakers, and more.  Bring your own gear: DIY amps, speakers, turntables, DACs, servers, etc. Share ideas and learn to design and build your own equipment.

By way of encouraging people to bring their own projects for show or demonstration, there will be free admission to anyone bringing a DIY project.

There will be displays, demos, auction and raffles items and freebies, plus well-attended lectures by prominent figures in audio engineering design like Nelson Pass, Siegfried Linkwitz, Damian Martin and Wayne Colburn. (Descriptions of their talks are in the Addendum, below.)

And, there are numerous DIY giveaways: Nelson Pass is, as always, generously contributing a big batch of Amp Camp amp circuit boards, parts and loudspeaker drivers.

For more information or questions, follow the Burning Amp 2017 thread at

A helpful map of the Fort Mason grounds can be found here:


When driving to the site, enter via the Gatehouse at Laguna Street and Marina Boulevard.

Don’t miss this very special event!


Achievement Unlocked: 75 Watt Class A Zero Feedback SIT Circlotron

Soft clipping at 75W

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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