Marshall lead and bass 50

billando

I bought a jmp 2100 50w lead and bass combo from i believe 1976 just waiting for it to arrive. Before it comes any experiences out there with this amp like settings you like or where on the volume pot it gets real loud or starts to break up? Its not going to be a house amp i will gig with it if i can tame it. One reason i went for one is i love paul wellers 90s tone on live performances around the time with sunflower or changing man and also it was a main gigging amp of oasis rythm guitarist bonehead mid 90s. 

ICBM

It’s essentially a JMP Bass 50 amp in a guitar combo cabinet. No master volume - you’ll need to attenuate it if you want to use its natural overdrive sound, unless you’re playing on the size of stages Weller and Oasis were back then. Although they do sound fantastic as a clean pedal amp, if you want.

They’re pretty hard on the speakers if you’re not attenuating it too, in fact if they’re original and working I would think about replacing them with more modern ones for gigging, rather than risk blowing the originals. You can take the pair out without unsoldering the wiring, if you’re careful - fit a whole new loom including a much longer cable to the plug, so you can connect them to the attenuator more easily.

These amps also have the dodgy pull-out voltage and impedance selectors, it’s worth having them hardwired to prevent issues. Check it has screen resistors fitted - they didn’t originally and are very hard on modern valves without them, particularly if overdriven. Most techs will fit them as part of an overhaul, but some don’t...

billando

Thanks for that yes i know they are non mastet i have attenuators i can use. They said the speakers had been changed out for g1265s

normula1

I've the head version and it had a captive mains cable and as @ICBM said they're not exactly quiet Mine has a sweet spot between 7 & 8. Above that it's a touch mushy, below the drive isn't there. It does have great cleans too whether turning the amp volume down or doing the same on your guitar.

Neilybob

Calling @Jonathangus ;

ICBM

billando said:

They said the speakers had been changed out for g1265s

That’s good - ideal for it. I would have suggested Creamback G12M-65s otherwise.

billando

Amp actually arrived and had 20 mins to muck around with it before i left....in high treble i got it up to 4 with very linear volume pot without being deafening....is this right? I heard these get really loud very quickly. Also, it sounds nothing like the 1987x i had previously which was much stiffer and really loud by 2 on volume. Id say stiffness is similar to my wem dominator....maybe between a dominator and 1987x....all this sound normal? I do like it though. Also it came with a box "original parts" which i havent opened yet.

billando

Might just take it to my tech to look over anyway

ICBM

That sounds normal - they’re nowhere near as abrupt and aggressive as the 1987, the lead models have a very large treble-pass cap which changes the taper of the pot. The L&B is really a bass amp with guitar speakers - softer and with more bass and less harsh upper-mid and treble.

It is worth having it looked over, even if it’s already been overhauled - some techs do a more thorough job than others. The selectors and screen resistors are important, don’t gig it until you know both are done.

billando

Magic thanks again. You played these much? As i said i just had the volume to 4 where it was warm with little bit of crunch....still mostly clean. Does it get much louder and crunchy above that?

ICBM

billando said:

Magic thanks again. You played these much? As i said i just had the volume to 4 where it was warm with little bit of crunch....still mostly clean. Does it get much louder and crunchy above that?

Not used one live myself, but worked on a few of them and played them in my workshop. They’re really nice amps, I think the best-sounding of the JMP non-MV amps. They are loud and with the classic Marshall crunch, but need to be turned up further than the Lead models to get there.

I modded one with a master volume (probably sacrelige - but he needed it, it was just too loud otherwise) for a fairly famous player who will remain unnamed . (And not Weller or Bonehead .) He’d already blown one of the original speakers unfortunately…

Jonathangus

Neilybob said:

Calling @Jonathangus ;

This is a bit earlier than mine.  Mine is a 2104 MV from 1979.  I don't know how they compare, circuit-wise.

ICBM

Jonathangus said:

This is a bit earlier than mine.  Mine is a 2104 MV from 1979.  I don't know how they compare, circuit-wise.

Same circuit board, most components identical, slightly different layout. 

billando

I have a 2104 too. Doesnt sound at all like the lead and bass. Great amp though.

Rusty-Strings

The 2104 has cascaded pre-amp and lead spec tonestack. The Lead and Bass is a 4 hole, 2 channel with a bass amp tonestack.

ICBM

ICBM said:

Same circuit board, most components identical, slightly different layout. 

billando said:

I have a 2104 too. Doesnt sound at all like the lead and bass. Great amp though.

Rusty-Strings said:

The 2104 has cascaded pre-amp and lead spec tonestack. The Lead and Bass is a 4 hole, 2 channel with a bass amp tonestack.

All these things are true at the same time .

It’s remarkable how effective Marshall’s simple altering the positions of a couple of parts of the circuit and about half a dozen component value changes is.

If I remember correctly the Lead & Bass has the NFB from the 8-ohm tap and the 2104 from the 4-ohm as well.

normula1

It's been a long time since I first modded it, but I've half a recollection that the volume pots in mine were 500k. I'd had a master volume fitted and it was pretty clean all the way up on the preamp vols. As per @ICBM's comment, it's pretty easy to covert to any number of variants of Marshall....  I may have gone over with my mods though rendering pretty unsaleable now due to drilling holes in the chassis... it was the late eighties, I couldn't afford to buy a new one and I had a hot soldering iron
When I rebuilt it almost back to stock a couple of years ago I ended up splitting the cathode on V1 as it sounded better and the PCB already has the holes for the components and left out the bright cap on vol1.

Littlejonny

YES! Love Weller’s cranked Marshall tone…post some clips when you’re ready. 

billando

Well i decided to give it to a tech for a good check over. Whilst its there....what of my 2 attenuators will be best with it?...marshall power brake or fryette? This is for unmiced pub gigs with loud drummer.

billando

Got it back from the tech and had around 20 mins to play about with it. Seems like at my band volume i can get the volume to around 1/4. This is still quite clean but its a real thick nice clean with touch of hair. Im going to try both options when i get a chance but do you think i will have better results getting the master higher and attenuating or putting my marshall guvnor pedal through it?

Emiel

billando said:

Well i decided to give it to a tech for a good check over. Whilst its there....what of my 2 attenuators will be best with it?...marshall power brake or fryette? This is for unmiced pub gigs with loud drummer.

Either one will be just fine. I love the Fryette, yes it is an expensive piece of kit but it does its job so well. I like to be able to raise or lower the volume just a bit instead of steps of say 3 dB. In case your amp breaks down (happened to me once), it works great as a power amp as well when combined with a decent preamp (I have a Tsakalis Room #40, a Plexi/JMP in a box).