I just finished building a 70s JMP 2204 circuit that can switch (via a pull switch on the gain pot) into an 80s JCM800 2204 circuit. Contrary to popular internet misinformation, not all 2204s are the same circuit (the early JMP 2204s [but not 2203s] don’t cascade gainstages on V1 and run V2 hotter than normal [330k shared plate resistor], whereas the JCM cascades a gainstage on V1 and uses the typical 100k shared plate resistor on V2). All in a TINY generic aluminum chassis. I couldn’t believe how quiet it runs, given the messy wiring, the high gain, and cramped space. V2 is JMP circuit, which makes for insane gain in JCM800 mode. In either mode it has a kind of “chewy” kind of late compressing overdrive (if I had to explain it slightly exaggeratedly... if that makes sense). I suspect because of this stage. The (less) Presence/Negative Feedback control is also JMP. Which, in my opinion, makes the Bass pot more useful than the JCM800 (more) Presence/Negative Feedback allows. It still has plenty of tightly controlled bass, but not as insane of an amount as some JCM800s have (depending on speakers). Its less NFB make it a little more dynamic than JCM800s. One “mod”: I used a 47k slope resistor in the tonestack. I’m sure some plexis and JMPs went out with this value (a common subbed value at the factory due to supply), but it’s not stock/standard on the schematics. I like the slightly different midrange character of the 47k instead of the “stock” 33k (or JTM45’s 56k). Finally, the output transformer is a 35 watter. I purposely got an under-powered OT for tonal reasons: transformer core saturation at slightly lower volumes.