I'm also thinking since I'm going to have the amp open and replacing the power transistors, maybe I should also replace caps at the same time? 

Hey Harley, sounds prudent, the caps are old

Hey Robertkoa, so since that quote (2014) I bought a couple of MP-1s.  While trying to sort them out with my tech I swapped out the EVs in one MP-1 and put in a pair of Mullard long plates, it instantly sounded way better.  While theoretically short plate tubes should be less micro phonic, it's never been an issue for me, i.e. using the long plates.  As Harley says, try a few different combinations and your ears will tell you.

Sovtechs work well in Marshall circuits, as I discovered at a tube rolling night/workshop, originally IIRC Marshall used Winged Cs made in St Petersburg, but available no more .

From what you said in the other tube post, what I saw last weekend is closer to what you are chasing?  So a friend played me a youtube clip going through the development of the Paul Reid Smith Hendrix Marshall clone, where they got to check out his Marshall in a museum and then try to replicate it.  The results are pretty spectacular, albeit quite expensive heads (20w, 50w and 100w).

Hey Robertkoa, there is a mod some MP-1 users did that lowers the bottom end centre frequency, but like Harley said, when I was using a MP-1 it had plenty for me.  These days I use a MP-2 which has great cleans (and everything else).  All the voices in the MP-2 (10 of them) are tube, so no SS like the MP-1, and voices 1 (crystal clean) through 5 (Warm Vintage) only use one gain drive OD1 (i.e. no OD2 which is available for the higher gain settings 6 through 10).

For phase inverters, their job is basically to split the signal into +ve and -ve half of the signal to drive the push pull output tubes, which are typically 1 tube for +ve and 1 for -ve in a 50w head and 2 tubes each +ve/-ve for 100w heads (e.g. 6L6 or EL34s).  While PIs are often 12AX7s, PIs don't need that much gain so often it's better to use a 12AU7 or 12AT7 which are lower gain but higher current and push the output tubes harder (if you like a bit of output tube distortion).  I'd not thought about using a PI post preamp as by then I'm running stereo (well pseudo stereo) as channel A and B in either MP-1 or MP-2 are 180 deg out of phase (which happens at the stereo chorus).  To do what you are thinking, you could put a tube in the MP-1 FX loop which is after the gain and EQ but before the chorus and still mono.  So maybe a tube screamer but use a 12AT7 in it?

I've been using the Mullard long plates in my MP-2s.  I find them a bit more 3D and a bit more depth and nice smooth distortion.  My friend uses a Mullard short plate in V1 and a long plate in V2 in his MP-1.  Experimenting with V1 and V2 combinations (as Harley was saying) may get you closer to what you want?

For recording, I use the MP-2 cab sim outs.  Not quite as versatile as the dedicated ADA cab simulators e.g. my friend puts a ADA GCS-3 in his MP-1 FX loop.  The MP-2 cab sim outs gives you 2 x 12 or 4 x 12 selections but not mike placement options like the GCS.  However, it works great for me .

Hey Robertkoa,

   The MP-1 should have all the bottom end you'll ever need already. My stock MP-1 does and so does my MP-2. The only one that didn't have enough low-end warmth was the MP-1 Classic. It's more like the modern Marshall kind of preamp for lack of a better comparison, meaning it doesn't have that low-end like a Fender Twin. I did warm that up with a pair of long plate Mullards and it helped without cutting out any of the mids and highs.

  I have a pair of JJ 803s in it now, but I'll be experimenting with some different tubes and maybe trying some combination of long and short plate in it. I definitely has a lot of bottom in it now, but the mids and highs are not as articulate as they were before, so I may try a short plate in V2 that's not as hot. It squeals with very high gain settings.

  True there is not PI in these preamps. but with the Microtube power amps, I think it simulates that since those also use 12AX7 tubes for the "Presence" control. I always dial that back to around 9:00-10:00 to keep it warmer.

Hey Robertkoa,

 I have 803s in my MP-1 Classic right now, and TBH, I'm not that thrilled with them there. The classic doesn't have as much low-end response as the original MP-1, and I thought it might help, but it seems to lack the desirable midrange frequencies that I'd like to keep. So far, the Classic sounded it's best with long plate Mullards.

 You might want to go with a shorter plate in the MP-1 to keep the microphonic squeals down to a minimum, or mix it up and use a long plate in V1, and a short plate in V2.

Your ears will tell you what you like and what you don't.

That's pretty cool how you did that layout!

It looks like you photographed your gear and cut and pasted it to a clipboard, then connected all your lines somehow. Nice work!

Quote from: MarshallJMP on May 30, 2024, 01:42:24 PMThere are 2 ways to measure the current, masure the voltage over the white 0.1 ohm power resistor, ballpark is 40 to 50 mV (milli volts!!!) or take the fuse out and put an ampmeter bewteen the fuse lugs and there you should get between 40-50mA.

This is useful.

I'm also thinking since I'm going to have the amp open and replacing the power transistors, maybe I should also replace caps at the same time?

There are 2 ways to measure the current, masure the voltage over the white 0.1 ohm power resistor, ballpark is 40 to 50 mV (milli volts!!!) or take the fuse out and put an ampmeter bewteen the fuse lugs and there you should get between 40-50mA.

Pedalboard & Signal chain: It looks complicated, and I admit I had some extra time when I did this, but it's pretty straight forward. See the attached diagram below, here's an explanation;

The Boss MS-3 runs/controls everything. All FX (except a couple pedals) are in there, and all external stuff runs through it somehow...It has 3 loops

Loop 1: Outboard effects (Wah pedal, Octaver & Mojomojo OD)
Loop 2: Amp (via 4 Cable Method)
Loop 3: not used

Notice I have the stomp boxes before the amp, and I have another loop available if I want anything after the amp, but before my stereo delay pedal....

When the signal leaves the MS-3, each output runs into the Echolution 3 L/R. That signal runs out to the amps for each side;
Side A: to the FX RETURN of the main preamp I'm using
Side B: Into the FX RETURN of the amp I'm using as a slave (bypasses the preamp, just uses the power amp this way)

Quote from: rnolan on September 18, 2014, 08:13:20 AMHey El, as SC says my direct experience is with the long plates as the short plates are more recent than when SC and I embarked on our "tube" discovery. He went MP1, I went MP2 and we both loved the result so IMHO you can't go wrong with the long plates MP1 or 2.  For super high gain sounds, the short plates may be better as short plate = less microphonics (I've not had any problems with the long plates, but for 3TM makes sense), I've yet to hear them (SPs) though to compare the 3D and depth, from the patches you've been posting, go with the long plates, you won't be disappointed, they are great tubes 

I got much more bottom end and clearer gain in the H&K Tubeman  long ago ...smoother singing gain .

I have an MP1 in storage - when  I bring it out ...will the 803s  give more bottom end [ including the cleans ] and smoother gain [ Gilmour Carton EJ etc ]  ?

And also the Sovtek LPS ?
 What do you think ?