Taming a Marshall model 1987 gainy volume...

[Slobrain]

Well I wanted to ask opinions about changing the 1st gain stage 12AX7 in a Marshall model 1987 to a 12AY7 like the old Fender 59 Bassmans? Seems the Marshall gain is too hot to quick and I want to get it more down to normal volume levels so I can open up the volumes but not have my neighbors calling the police... I also want my Marshall to do a better louder clean tone before it breaks up.

Looking at the old Fender 1959 Bassman schematic the 1st gain stages for both volumes are using a 12AY7 and the hi treble cab is 100pf, not the 4n7 that Marshall uses. I'm also thinking about changing the feedback resistor from 100k to 47k and moving the feedback tap to the 4 ohm from the 8 ohm to get the power amp cleaner too.

I have never played thru a old 1959 Bassman so I do not know how the volumes react in those amps. Not sure how clean loud they go before breakup.

Anyone have any suggestions about this?

Cheers

[big_teee]

Well I wanted to ask opinions about changing the 1st gain stage 12AX7 in a Marshall model 1987 to a 12AY7 like the old Fender 59 Bassmans? Seems the Marshall gain is too hot to quick and I want to get it more down to normal volume levels so I can open up the volumes but not have my neighbors calling the police... I also want my Marshall to do a better louder clean tone before it breaks up.

Looking at the old Fender 1959 Bassman schematic the 1st gain stages for both volumes are using a 12AY7 and the hi treble cab is 100pf, not the 4n7 that Marshall uses. I'm also thinking about changing the feedback resistor from 100k to 47k and moving the feedback tap to the 4 ohm from the 8 ohm to get the power amp cleaner too.

I have never played thru a old 1959 Bassman so I do not know how the volumes react in those amps. Not sure how clean loud they go before breakup.

Anyone have any suggestions about this?

Cheers

I recommend the post master volume, if you don't have it.
The most popular for marshalls is the Lar-Mar PPIMV version.
It allows you to play the amp at Near Bedroom Levels.
Lar/Mar PPI-MV - MetroAmp Wiki
T

[Dave H]

Rather than converting it to a 59 Bassman why not convert it to a JTM45 (which was modelled on the 59 Bassman) then it would still be a Marshall but a well behaved one?

[big_teee]

They are all loud without the MV mod.
With the mod you can turn up the gain and get the crunch at low levels.
I just built a JCM800 2204 amp with 6L6s, got done with it this week.
I fired it up without the PPI-MV, It was loud, and hard to get enough drive at normal levels.
I wired in the Mod, and it was an entirely new amp. Sounds great, at all levels.
I wouldn't have a 50 watter or larger without the PPI-MV, but that is just me.
T

[Dave H]

They are all loud without the MV mod.T

True, but but he doesn't want low volume crunch from the amp. I suggested the lower gain JTM45 because he said this in his other thread.

"What I want to do with this amp is to get it loud but clean, I like to use pedals on a clean sounding Marshall, that has always worked best for me."

[Slobrain]

Hey guys,

Thanks for the good advice, The PPI-MV looks great and I bet its probably really a good mod. What I was shooting for was the Marshall to behave like a Fender amp. Most would say then play a fender. The Marshall tone stack gives the old non master amps such a great tone. I was playing thru a modified Fender bandmaster but the Marshall smokes it in tone.

I would bet back in the 70s some guys would crank their Marshalls for tone while some would just use pedals to get their dirty sound. I do like both methods but playing clean and using different pedals makes the Marshall more versatile instead of the (one trick pony) Besides my wife would have a fit if I were cranking Marshalls in the house...
I haven't tried a JTM45, I'll have to look into that more.

Thanks

Slo

[mhuss]

As you suggested, just putting a 12AY7, 5751, or other lower gain tube in V1 will do a lot to clean things up and give you more usable volume range before breakup.

--mark

[Heliotricity]

Have you considered converting your 87x to a 1986 50 watt bass head? That is what I did to mine and never looked back. I look at the 1986 like it is somewhere between the 1987x and the JTM45. It is closer to the 87x but with certain appealing JTM45 like characteristics. It has a thicker tone due to the shared cathode (like the JTM45), is less bright and gainy than the 87x and has better cleans. The JTM45 has even better cleans but less gain and a has quite a different vibe, part of that owing to the fact that it is tube rectified where the 87x and 86 are solid state rectified. All three are great but each a little different.

The mods to make the 87x an 86 are pretty easy. Just removing the bright cap and redoing the V1 cathodes so they are shared makes a suprisingly big difference. If you want to go further you can change the slope resistor to 56k and the tone range capacitor to 250pf, you can also change the post phase inverter coupling caps to 0.1mfd. You can remove the .68 cap on V2 as well or leave it if you want a little more gain on tap, I ended up removing it on mine. You might want to look into it and if it is still not working for you than maybe check out a JTM45. It will still be loud though, but thats how they sound best! You may find even with a JTM45 you'll need some type of attenuator for your situation. Good luck!

[big_teee]

If your going to all the trouble to rebuild it into another amp, I would just sell it!
Sell it as a vintage amp and start over.
Personally the JTM45, and 1986 are both way to bassey for me.
The 1987 circuit has that marshall crunch.
If the V1 .68uf is too bright, try a larger Bypass Cap in that spot.
Like Mark said, try some different tubes in V1, like the 12AY7.
I still stand by the Lar/Mar PPI-MV Mod. Best money spent.
BTW, you can make a 1986, out of a 87, but you can't Easily make a JTM45 out of a 1987.
The OT is wrong, and the tubes would need to be changed to KT66s, plus it would need the tube rectifier.
T

[Heliotricity]

Right, I wouldn't suggest trying to convert the 87x to a JTM45 unless you really knew what you were doing. The 87x and 86 are very close which is why I suggested the possibility of mods. But I agree, if you are thinking of the JTM45 I'd do like big_teee and just sell the 87x rather than go for some complicated conversion.

[Slobrain]

Thanks for the info guys, Right now I have a 12AT7 in V1 since I don't have any 12AY7 laying around and its got the gain down a bit, I may move that to V3 for the phase inverter and then try a 12AY7 for V1 as soon as I can order a 12AY7 from NS.

I will remove the bright cap and replace it with a 100pf as I did with my old Marshall 1987 that was built in 1976.

I probably want to keep it as a 1987X model as I always loved the tone these amps have but just too much gain on tap for my liking. I can't do the (crank the Marshall) stuff anymore as my hearing was damaged back in 1995 and caused me to stop playing out in clubs due to the damage, Doctors said If I was to continue to do the band thing I was looking at worse damage and maybe needing a hearing aid...
I prefer to use pedals for the distortion. Right now I'm thinking about maybe getting a Wampler Pinnacle as I like the sound clips I hear on YouTube, I just really need to try one on my amp to see if its good.
I was lucky enough to get a Marshall 4x12 1960AV with the vintage 30s in it from a buddy and man that cab sounds great with that head. What a BIG difference from using the G12M-70s that I was using. I wonder if this rig would sound better with greenbacks though?

Cheers