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One of the first amps I built was a PCB-based "Superlite IIB" from GuitarAmplifier PCBs. I built it in a non-standard 17x8x2 chassis, and had a custom head cabinet made to accommodate the chassis. In hindsight I now see it would've been prudent for me to go with a standard chassis and head cab, but thats not changeable. This head cab has 14" wide front and rear panel cutouts, so I need to be very careful with control/input placement on the front panel and jacks/IEC etc on the rear panel.

I am toying with the idea of getting a blank chassis...17" x 8" x 2.5" (Watts Tube Audio) and repurposing the cabinet and building the Plexi MKII V6. I would drill my own chassis and get custom faceplates made, but I have several questions related to my limited available "real estate" on my front and rear panels:

1. Power and Standby switch....I could combine these into a progressive "Off/SB/On" switch in order to eliminate one switch from the front panel. Another option would be to replace the Power/Standby switches with a Trinity's VRM control.

2. Inputs...the 4 inputs takes up a decent amount of area on the panel, and I almost exclusively use the Hi Input anyways. I was thinking of having a single input and using a toggle switch to toggle between Normal channel only and normal + bright channels...i.e. jumpering the channels...is this doable? This would take away the option of bright only. Or maybe I could do a 3-position mini toggle to go between normal, bright, and both.

3. Rear panel...I'm considering an effects loop...I think I should have enough room on the back panel for this if I plan carefully.

I suppose the most difficult challenge would be the single input and "jumper" toggle switch. If someone could point me to some resources for how to go about setting this up (or if this is even possible), I sure would appreciate it! I'm not sure how tricky it will be to wire the input and grid stopper resistors in this sort of configuration. I found some info on doing this on a 5E3 but wasn't sure how this translates to the Plexi.

Thanks and happy holidays!

I've found a schematic and layout for internally jumping the normal and TMB channels, using a single "Hi" input. Should I use 33-34K grid stoppers on the inputs since I am using a single jack?..this would equal the parallel 68K resistors when using the "Hi" input of a dual Hi/Lo set up if I understand correctly.

Doing this brings me to my next point...what about the cascade option with this setup? Is there any reason the cascade switch wouldn't work with a single input as described above?

Finally, on the other end of the amp...I'm considering a LarMar PPiMV as has been discussed on this forum previously. http://www.trinityamps.com/phpbb/download/file.php?id=237&mode=view
I've used a version of this in another build and it seems to work great, and may be a good choice for controlling the overall output in an amp like the Plexi MkII where a lot of the overdrive, at least on the Plexi Brown channel, is from the preamp. Since I plan to use the V6 option in this build, would there need to be any special considerations for the placement of the MV with respect to R18/R18b and R19/R19b? I could also go with the master volume used in the TC15 if that is a better option, but would need help on that as well.

Thanks for the help! Just trying to get a game plan together.

Yes, using a 33K grid stopper on the input will be the equivalent of the High input on the TMB or Normal channel.

The cascading option could be done with a single input. If you google around you will probably find examples. Bancika used a switch with a single input to have the option of cascading in a Firefly .... see here:

http://diy-fever.com/amps/ax84-firefly/

Dave

I would try the PPIMV right after C8&C9

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Stephen
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