I am intrigued enough by the Berning ZOTL amp to actually try and build one. But before I do a working LTSpice model to understand the design was an necessity for me. So I created a model that matches his patent. I am sure there is many stuff left out of the patent that is important but discovering those in a simulation beats finding out on the bench. So this first attempt is an idealized model, switches instead of FETs, idealized transformers, but a real tube model (6NJ6 screen driven). So being totally new to ZOTL and screen drive this may be an interesting journey. The model does work (I think).
Next steps is to optimize ideal model then bit by bit put in real components....
Next steps is to optimize ideal model then bit by bit put in real components....
Update: I built out the model a little more with a 6N1P phase-splitter and mosfet drive for the 6AV5 screens. Still mostly idealized with a few real components sneaking in. Simulating decent performance so far, now trying to get more power out. Simming to 6W before distortion. Should be able to get at least 20W out of a PP 6AV5.
At the point where I have a useful (I think) functional ZOTL spice model. Added some feedback and can get a pretty nice sim of a 6AV5-like output screen driven. Operating points not optimized but trial and error picked some. Below is FFT of 1W out with an output bias current between 5 and 10ma.
Now I suspect not many have played with the ZOTL architecture. But I have some questions to those that may have experience. (@kamonjira).
1. What impedance ratio from primary to secondary rectifier chain is a good place to start. I have simulated with ~5-6K secondary impedance in this model assuming a 8ohm load?
2. With screen driving this tube in ZOTL achitecture how much plate voltage peaks can be tolerated. Below are the plots of the plate voltage at 1W out.
Now I suspect not many have played with the ZOTL architecture. But I have some questions to those that may have experience. (@kamonjira).
1. What impedance ratio from primary to secondary rectifier chain is a good place to start. I have simulated with ~5-6K secondary impedance in this model assuming a 8ohm load?
2. With screen driving this tube in ZOTL achitecture how much plate voltage peaks can be tolerated. Below are the plots of the plate voltage at 1W out.
Do you have a link for your article? I would enjoy reading it. I am initially curious about to learn (sim + hands on) the plusses and minus of the various impedance matching methods available.
1. Traditional ubiquitous large iron transformers (~75 years of continuous development)
2. ZOTL - switching tech. Not alot of DIY or open source development
3. Traditional OTL - Lots of DIY, is traditional OTL development at the end of its development arc?
1. Traditional ubiquitous large iron transformers (~75 years of continuous development)
2. ZOTL - switching tech. Not alot of DIY or open source development
3. Traditional OTL - Lots of DIY, is traditional OTL development at the end of its development arc?
