Have a look at: [https://easyeda.com/hebert.luiz.hb/Ruby_Amplifier-eee2cd1d57534741af140a658ecdc3cc](https://easyeda.com/hebert.luiz.hb/Ruby_Amplifier-eee2cd1d57534741af140a658ecdc3cc) A simple change to the front end will convert it to the common drain stage that the so called "Fetzer" amp stage uses. You might also be interested in: [https://easyeda\.com/example/Tesseract\_Guitar\_Practice\_Amp\-MjP71jBni](https://easyeda.com/example/Tesseract_Guitar_Practice_Amp-MjP71jBni) Note that you can simulate the whole design in EasyEDA: see the simulation files for Tesseract and please read (3) in (2) in: [https://easyeda.com/forum/topic/How-to-ask-for-help-and-get-an-answer-71b17a40d15442349eaecbfae083e46a](https://easyeda.com/forum/topic/How-to-ask-for-help-and-get-an-answer-71b17a40d15442349eaecbfae083e46a) You might also like:  [https://www.rs-online.com/designspark/design-of-a-korg-nutube-amplifier-part-1-tube-basics](https://www.rs-online.com/designspark/design-of-a-korg-nutube-amplifier-part-1-tube-basics) There is a simulation model for this device but it does not run in ngspice. It does however run in LTspice so the simulatable parts will be revisited when we swap from using ngspice to LTspice. :)

More stuff to play with... [https://easyeda\.com/example/Origami\_a\_collection\_of\_guitar\_effects\_\-JFa4mEWe8](https://easyeda.com/example/Origami_a_collection_of_guitar_effects_-JFa4mEWe8)