Very cool 

Interesting, MJMP will no doubt know the answer, hope he comes back on board soon.

Ok, so I've checked some older photos and my other MP-1s and there seem to be two types of transformers. One with black insulation and one bobbin, second type is with 2 bobbins and blue insulation. The blue ones have STEED logo on it. I still have a suspicion that this is a factory made tranny.

So...had practice last night with the new cab. I had it kinda low, just sitting on a 4-wheel dolly, but I was 10-15 feet away, so it was hitting me.

How did it sound? Pretty dang close to the two 1x12s actually. I think a bit more sound is coming out the open back due to the tandem speakers moving around in there, but the tone itself is surprisingly similar. Go figure...of course, I used the exact same two speakers  (Eminence 1218 legend and WGS G12C/S), which are both v30 knockoffs with a smoother top end than the brittle top of real v30s.

Yamaha uses a combination of the Legend 1218 and a Tonker in their 2x12 cab. I may consider a Tonker later

The dang cab fits absolutely PERFECTLY in the back of my little Ford Fiesta, so I guess I gotta keep it I put the cab, my pedalboard, amp head and backpack full of mics/cords in the back and just used the entire back seat for 4 guitars. I'll get a pic of how nicely it all fits back there.

All in all, it's heavy, but not terrible...the H&K Grandmeister fits perfectly on top when you flip the cab vertically (gotta put some feet on that side...hence, the dolly). I'm happy I didn't have to tweak anything, I'd hate to have a bank of patches for each set of speakers. Here's a couple quick pix of the cab sitting on another cab and the back before I wired it up

Update - these Lorantz speakers are fu@@g awesome  . I just had a play through my new cut down rig with my oldest guitar (that I still have), Anson MIJ strat (heavily modified), has a late 70's SD hot staggered strat in the bridge, my old Navarra LP (the predecessor to Ibenez) bridge gold humbucker in the middle, and the original Anson SC in the neck. And just using my standard MP-2 patches, the sound is awesome. I love these speakers (and I've heard a few) and they just keep getting better.  If you are considering new speakers, give these go, you won't be disappointed.  So I went for the 12" 100w as they match up well with my various power amps.  The most popular apparently are the 75w 12".  They are about 1.5kg less weight and have a little more top end (according to the spec sheet).  Moreover Lorantz make a greenback version that allegedly matches the original freq curve. https://www.lorantz.com.au/product-category/loudspeakers/12-inch-guitar/

Hey ddt, no worries, others hear may know more  .  So according to the MDRT instructions, not changing the resistor on the tube board (R9) to 300k will mean the high voltage will stay at 190Vdc and not achieve the desired increase, in this case to 220Vdc and for the MDRT 240Vdc.  However, some may prefer it that way?  SC for example likes his MP-1 stock as he prefers the sound.  He even went so far as to source a very early original MP-1 transformer as ADA did change them a bit in later units, probably when they changed the rear jack to inst level and got rid of the inst/line level top switch and went to v2.x firmware.  The increase in high voltage provides for more dynamic range and opens up the sound.  SC preferred the original tone/sound and, in some ways, I agree with him.

Fantastic! Thank you so much for the info.
Looks like the R9 240k resistor remained in place in this MP-1, so basically it's unfinished business. 

Hey ddt, that looks like a custom transformer.  The stock tranny is one bobbin not 2 like the one in the pic.  Also those specs (12V heater, 220Vdc high voltage) are very similar to the MDRT (12.6V heater, 240Vdc high voltage).  The original trannys are 8-9V heater and 190Vdc high voltage (see MJMPs site https://www.marshalljmpmodshop.net/miscellaneous_parts_and_replacement_tubes.htm).  The MDRT is 2 bobbins but side by side. I'm sure there are other mods and custom transformers around, IIRC Rob Hell was getting some made quite a while ago (I think in China). 

As far as I know, ADA never made anything like it.  My guess is it's been modded with a custom transformer and should sound and perform much like the MDRT.  There should also be a 300k resistor on the tube board to accommodate the increase in high voltage (see attached for location).

Hey Harley, an option for using it in a loop would be combine it with your MP-2.  As the MP-2 stereo parallel loop is just before the cab sim outs, it's very similar (if not slightly better for recording) to a standard 4CM.  But then you have other rack FX you can use that way  . 

I saw some soft rack thingys a while ago and thought about a 2 RU with MP-2 plus rack FX unit.  Then you just need either a stereo amp set up for live or plug cab sim outs into a desk (or both).  A bit bigger and heavier than where you are going with the GP-10, MP-2s have a bit of weight to them, but with a shoulder strap it would be like a big laptop and be carry on on a plane.  Although you'd still need a lead bag or some such for the midi pedal etc.

The last session I did I just took my 4 RU MP-2 rack (MP-2, Midiverb 4 (in MP-2 loop) and B200s).  I didn't need the power amp and just went into the desk with the cab sim XLR outs.  I also have a small suit case thingy (like every one uses on planes) for my MXC, expression pedal and leads.  I even manage to fit one of those small folding guitar stands in it. 

It will be interesting to see how you go when you deep dive into the editing.  From the review I watched, his main apprehension for using The GP-10 live was it has no banks and you can only go up or down with the patch selection.

Hey Harley, well it would be great if you can tune it to do both, it's allot of sound(s) in a small and light box.

Richard, I can have it do both, I just need to use a real amp with the guitar part of the overall sound. There are still a few other cabling ideas I want to try though. I want to try this  in a 4CM set up, then there is the option of trying it in the loop for the effects only, (not including the synth portions of the sound). It's kind of a neat thing to mess around with at home, but I still need to take a deep dive into the editing and see what I can do with it.