Ideas for old marshall?

[azatplayer]

I have this 71' JMP SL/A head that i got in trade a while back. I recapped it, and cleaned up a lot of the junkish work that had been done. Unmodded it all except the hard wired input jumper.
This thing sounds real good. Better for the new caps, and cleanup, seriously loud and clean, great tone. I had a JCM800 50 watter i wish i still had too, that was a toneful thing.
Thing is, i dont play stadiums, and its got that much punch, its unusable even at low volume, its just so damn allpowerful!
Now i have it setting on my bookshelf, i figure in time its gotta grow a little in value, who knows where early metal faces will end up, mine has a 69' date on the PT too, bit of history.
I have run it with 2 tubes pulled, 8ohm out into a 16ohm cab, not a lot less loud! And the same damn punch in the face!
I dont want to put a master in it, but was wondering about trying 6V6's in there instead? A quad of 6V6's could be a cool thing, certainly tame it somewhat. I guess other than maybe modding the bias, and running from a lower tap to offset the load, perhaps a set of JJ's would work out.
Would love to have some experienced input here, i dont want to damage the iron, but shame to not use her too.
Any thoughts?

[billyz]

What is the voltage on the plates? Some of those earlier Marshall's ran pretty high , maybe to much for 6v6's . Maybe the JJ's can handle it. What about an Air Brake.

I sold all my old Marshall's for just that reason, too much amp and lugging those 4x12's around.

[Andy Le Blanc]

Check out the VVR stuff, it would be a shame to frigg-up a rig like that.
The VVR would need one knob and a mounting screw inside, and I think is reversible.

[solderstain]

Ah! I love old SLs. My metal-panel is my second-fave amp (my '63 AC30 is first).

I had/have the same 'problem' and asked a lot of people a lot of questions and made some mods to mine that make it absolutely flexible from my living room to any gig I can imagine myself doing at my advanced age.

I know you said you don't want to do a MV, but I'm going to suggest one anyway - the right one WORKS. First, let me say that every single thing done to this amp is 100%, completely and invisibly reversible. If I ever went to sell this amp, and the new owner didn't want any or all of it, it could be put back completely original with no holes/marks/scars.

Here's what I did with mine:

1) I run with two output tubes as well. Rather than pull two tubes, I removed one of the output jacks (I'll NEVER run more than one cabinet), and installed a rotary snap switch which didn't require drilling or enlarging of the original hole. I can go back and forth between two and four output tubes in a millisecond.

2) Install the "Larry-mod" KF Type II PPMV. I did it exactly like the diagram originally posted on the Metro forum and I think I've seen it here too. I mounted mine on the front panel in one of the low-sensitivity inputs. See the picture below.

3) I installed a Vox-style Cut control as well. Since the SL is a NFB amp, you might (not will) get some extra high-end sizzle when turned WAY down, and the Cut control lets you dial that back out. I also find it useful even when it's not turned way down, as metal-panel SLs can be rather 'strident' on the top end anyway. Like the MV, I installed the Cut in a low-sensitivity input, right next to the MV. The nice thing about this is that Cut control wiring can be super-short, since it connects directly to the MV pot. No running extra wires back to the board.

Just as an OBTW, these two simple things won't help with the volume, but they do make the amp more useful (to me). You've probably already heard of them, but I'll list them anyway...

4) Disconnect the Bright cap on the Channel I volume control.

5) Add a 500pf cap across the mix resistor for Channel II. I never found Channel II to be of much use by itself before doing this mod, but with that mod, I play most of my leads in Channel II (I use an A/B/Y switcher).

Again, all of these mods are 100%, completely and invisibly reversible. And they make the amp livable and versatile.

[img:800:600]http://www.mofinco.com/amps/sl_front_mv.jpg[/img]

[John_P_WI]

I'm a guy who likes lots of gain stages, not necessarily high gain though. Simply adding a master won't do a lot with out cascading the first stages. Check out the "one wire mod" or Randy Rhodes mod. Very reversible.

Adding a master without additional gain stages will basically give you a 2203. If you are going to rewire, try a 2204 scheme.

OR, you could rewire the cathode follower to a gain stage. Yes, this will change the tone driving the tone stack from the plate. More moddern sounding.

4 tubes in the output section gives a different tone than the 2 tubes if you pull a couple. Without a great reduction in volume.

If you want to go the power scaling route KOC offers scaling kits that will handle the 100 watt power rating and virtually any voltage. I would suggest the more expensive one that controls the pre amp voltages too, providing more consistant tone as you dial down the output tubes. This kit will also let you set voltages, ie if you want to run 6v6 etc. Power scaling also has less stress than attenuators on the tubes and xformers.

John

[solderstain]

...Adding a master without additional gain stages will basically give you a 2203...

Hmm... you must be looking at a different "2203" than I look at. A 2203 is more than a Super Lead with a MV. The 2203 has V1A and V1B cascaded (as long as you're plugged into the high input).

The OP didn't say he was looking for more gain; he's looking to reduce the volume of his Super Lead and retain some of its original tonal integrity. At least, that's how I read his intentions. A well-designed PPIMV installation does wonders for an amp of the SL generation, and the revised Type II design certainly qualifies.

[azatplayer]

OK, looks like a PPIMV! The poor old thing has had some holes drilled in the back at some point, they were empty when i got it. It had a dicky rotary impedence selector that worked on the 8 ohm but not on the other 2, when i had a closer look, it looked like there was flux on the terminals, what looked like flux turned out to be wax...
Seems he liked to burn candles on top of his amp while he played.. the wax dribbled down thru the top vent on to the chassis, then down thru beside the caps..
I found an original selector for it when i was cleaning it up.
I really like what i hear from it, and i did do the bright cap snip, was the first thing to go! Makes the world of difference.
So, Solderstain, the 500pf cap on channel 2, that brightens it up?
Before i snipped the bright cap, i had to use the 2 channels bridged, it was just ear piercingly bright, nasty stuff. Dialing in the bass channel was necessary.
Well i have all the parts i need in my drawers for the MV, so what better way to spend a cold sunday arvo?
Cheers for the input guys. Let you know what my results are.

[John_P_WI]

Yeah I had a brain fart on the 2203.... My bad....

John

[azatplayer]

Well, PPIMV rocks! Wow!
Funny thing is i guided a mate thru fitting one to his JTM a few months ago, he raved about it, and here i am!
At some point it had a hole drilled in the back above the PI, so was pretty good positioning. I rerouted the original grid wires to the pot, removed the 220K's, and ran new wires to the tubes. My buddy had no shielded wire when he did his, and said it was no noisier after the mod, so i figured why not?
I ran nice solid 20awg and alls quiet and sweet.
Solderstain, i also did the 500pf on the mixers, great mod, thanks very much for the nudge in the right direction, sounds great.
I took the bright cap off when i first got it, alltho now that ive done that 500pf mod, both channels sound a lot more alike. The only difference being of course the 2 cathodes on V1, the 250uf elytic verses the .68uf mustard.
Im gonna try a larger bright cap on that channel, see how that sounds.
I dropped a new set of Ruby(shuguang) in there, just a pair, and a NOS GE in V1.
I like it as far as maybe 1 oclock, gets a bit gainy after that. Really does what i needed at about 4 oclock, just takes the whack off the top, i couldnt play this even gently before without perforating my eardrums, never played an amp with that instant hit like this b4. Its gonna be off the shelf for a while now, in fact its goin to the next gig! SWEET!
Thanks fr the input guys.
Don

[solderstain]

Yeah Don! Good for you. I'm grateful that I got the advice from the people that helped me settle on these mods, so I'm glad it worked for you too.

[bsmith]

you could have also tried slaving. or attenuation.