here’s the final face and schematic of the Shin EI that I’ve been working on :
so once again , nothing special ,it’s the classical shin ei “chainsaw” companion fuzz circuit with a variable twin-T filter (2K pot) and JFET gain boost. Jfet can be a pain in the *** to properly bias so I put a 5K trimpot (actually a 2K with tail resistor ) to get a nice 4V5 at the drain . The 10uF cap is here to maximise the gain.
I put low gain transistors (2N3904) in sockets because I didn’t know what was the gain of the original transistors and I’ve a lot of these 2N3904 in my stock . It turned out that they work good . I guess the gain is so high in this circuits that it doesn’t really matter what you put in.
The jfet gain stage is here to bring some volume , the original circuit is so compressed that there’s no volume gain . The volume pot is placed before to not overdrive (or not a lot) the jfet. That way the JFET deson’t give is own color . The oppositive idea could be done also . It’s not a massive output gain but enough to make it bigger .
I had some doubts about the tone knob but it seems to work pretty good after all.
here’s a cleaner version of the schematic : https://smokingtip.files.wordpress.com/2013/05/shin-ei-comp.pdf
after all , the circuit is kind of funny and the sound is interessting . Testing it this afternoon gives some ideas to make a circuit with this “chainsaw” sound . Not a clone but something in this direction with more controls and flexibility . A weird mixture of all these buzzy early fuzzes . I’ve a bunch of 100 GT308V low gain germanium transistor and they may work good with additional components to create an input gain stage and tone section . So I wrote down the idea and I see if it’d go back in my mind in the futur .