Mike
Very interesting concept. I always wondered about two complete amps (800 and Plexi) in one chassis where you could use either or both at the same time like my old Sunn Beta Lead but that was a SS amp. I think LC built an amp with 2 complete amps in one chassis switchable to one the other or both at the same time. I remember getting him the switch for it a few years back. Maybe he will see this and comment but I have not seen him post here much anymore.
I am still working on my Dual 50 I got side tracked a month. I got all my parts and will build my dalator in the next week or so to test out and make my final decisions on how I will proceed. I just installed a PPIMV on a 100w plexi and was not overly impressed so I am hoping the dalator will do the trick for the global volume control and keep the marshall style MV as Sluckey has in his layout.
Anyway I am going to keep tabs on this progression I really like your ideas. I am not seasoned enough to make a lot of comments but one thing I will say is everyone is telling you in a very nonchalant way trying to be polite, to use the larger chassis. I went against the grain and recommendations of some very knowledgeable folks on this board on 2 builds in the past and created lots of headaches for myself. One I had to dismantle and put into a larger chassis to correct the ability of being able to tune in Tokyo from Florida. With as much as you want going on and the costs you are going to incur use a normal size large Marshall box 29"L, put yourself a 27"L X 2.5 to 3" H chassis in it you will be much happier with the results and it will be a much more enjoyable build form a construction stand point. Just my $.02 Good luck and post lots of pics.
Shortfuse
I am pretty confident you will like the Dumbleator. It may also make the PPIMV work better as you will be able to reduce a little signal pre PI and then some post PI. I read somewhere that Marshall's get a lot of their tone from overdriving the PI. I don't know if that is true or not but with both controls in place I am pretty sure you will like what you hear after you tweak it the way you want it.
I am having two chassis made this week. One will be 25-1/2"ID X 8-1/2"ID X 2-1/2" deep and the other will be 3" deep. I used the Inkscape program to layout the faceplate, tube placement and circuit board spacing using the dual tone stack concept. Utilizing mini pots (16mm) everything fits perfectly and lines up well with the seven preamp tubes spaced correctly.
Thank you so much to everyone that contributed their suggestions and comments to this project. I appreciate sluckey's support and original efforts that inspired me to take on this project and tubenit's kind words, redirection where needed and effort in getting the schematic drawn.
My last stumbling block is how to ceate a mixer circuit for the two preamps. The signal for the Plexi will exit through the wiper of the treble pot and the 800 through the wiper of the master volume pot. The junction of the two will be sent to the relay for the OD circuit, I will need a mixer circuit to blend the two. Can this be just two 470K resistors?
I will follow up after the amp is completed. Health permitting it shouldn't take more than four to six weeks. I still have to order a few parts, design the backplate, have the backplate and front plate made, etc.
Thanks
Mike
