Marshall 100w jmp super p.a. 1969 4 inputs

fastonebaz · May 2017

I have one of these heads in mint condition. I don't use it it just sits on my cupboard at home. I've owned it for 25 years now. It's pure clean sound and loud. I'm wondering if anyone knows anything about them. Eg who used to use them, what they used them for, are they of interest in today's market?

Cheers

ICBM · May 2017

It's essentially very similar to a Super Bass but with two extra input channels. (Slightly different from a Super Lead although still not far away.) Although they were intended for PA, and presumably some people did use them for that, you will also commonly see them being used for guitar or bass, if you look at photos of a lot of the bands of the day, eg Free.

They are definitely quite desirable, slightly less than a Super Bass but still valuable. Most players wouldn't buy one if they can afford a Super Lead or Super Bass, but they're seen as a good alternative on a budget. A lot get extra caps added to one or more input channels to brighten them up.

fastonebaz · May 2017

Oh that's really interesting thanks. are there any mods that people did to give them some overdrive back in the day?

fastonebaz · May 2017

I found a brief clip of it i made ages ago

Just threw a Fulltone plimsoul pedal in front of it.

ICBM · May 2017

fastonebaz said:

Oh that's really interesting thanks. are there any mods that people did to give them some overdrive back in the day?

Not really - just turn them up full

.

In the 80s you might have seen them used as a basis for distortion mods, since all old Marshalls were, and PAs had an extra valve stage already so were easier to get more gain out of.

Nowadays I think it's better to use them as you are, as a great clean amp which takes pedals really well. It is possible to do some simple mods which don't destroy the character of the amp though - since all four channels are the same, and all four models of the original amps (lead, bass, PA, organ) are also closely related, by adding a few caps you can get an approximation of the various models from each channel. Or alternatively, one I did recently - essentially to make channels 1 and 2 into a Super Lead, and 3 and 4 into a Super Bass. You can't easily get the Super Lead tone stack without more extensive work but many people prefer the warmer bass/PA version anyway.

However given the apparent condition of your amp I would think carefully before even doing very simple mods - as you already know, the simplest and most effective is just to put a good pedal in front of it!

Be careful if those speakers are Greenbacks - that's only a 50W cabinet and the amp will easily exceed 100W even clean, if the power valves are in good condition.

Ossyrocks · May 2017

I've had a few of those, including an early JTM100. They are great amps and a bargain in the vintage Marshall world, although less of a bargain these days. It's probably quite valuable now.

Kossoff liked 'em!

Rob

clarkefan · May 2017

Had one as well, July 69 so one of the first steel face models. Lovely smooth tone, sorry to say I never got to crank it, but even down low it had a clear reedy sort of lushness, very enjoyable just playing clean at home.

fastonebaz · May 2017

Thanks all i had no idea people actually used these as guitar amps. Mines literally been on my shelf for 25 years. I only played it briefly in that video to remind myself what it sounded like other than that i dont use it. My dad bought it from an auction on a whim and now i have it.

That cab contains 2 x 12" celestion greenback g12h speakers. Hopefully the picture link works. I have 2 of these cabs! They sound awesome although i only gig with one of them.

I've no plans to mod the amp or even use it. Probably just hang on to it for another 25 years!

fastonebaz · May 2017

http://i.imgur.com/AomrNmU.jpg

fastonebaz · May 2017

Pic
<a href='http://i.imgur.com/AomrNmU' title=''><img src='http://i.imgur.com/AomrNmU.jpg' alt='' title='Hosted by imgur.com' /></a>

ICBM · May 2017

Ha! That's why Celestion shouldn't call G12M-25's "Greenbacks"

. Most Celestion models of that era had green backs.

They're G12H-30s, obviously. Still, be careful about cranking that amp anywhere near up loud through only one of the cabinets, it will blow a 60W cab almost as easily as a 50W one.

jkirk170493 · May 2017

They're great. Americans go crazy for them! We've had a couple of them in the past and never struggled to sell them. In fact we were tempted to keep one as 'our' amplifier! You've got a beauty - don't let it go cheap if you do decide to sell it!

ESBlonde · May 2017

One word of caution. If it's sat unpowered for all that time and never had a cap job, it might be a wise investment. i have a 50w head from the year before and one of the big caps is starting to bulge at the end so it's off for a sort out. I'm going to use it as an excuse to tour Marshalls in MK while there's still something there.

Ossyrocks · May 2017

ESBlonde said:

One word of caution. If it's sat unpowered for all that time and never had a cap job, it might be a wise investment. i have a 50w head from the year before and one of the big caps is starting to bulge at the end so it's off for a sort out. I'm going to use it as an excuse to tour Marshalls in MK while there's still something there.

Be careful what you let Marshall do to your amp. Be clear you just want the caps or you may find a whole lot of stuff changed out when you get it back.

Rob.

jkirk170493 · May 2017

ESBlonde said:

One word of caution. If it's sat unpowered for all that time and never had a cap job, it might be a wise investment. i have a 50w head from the year before and one of the big caps is starting to bulge at the end so it's off for a sort out. I'm going to use it as an excuse to tour Marshalls in MK while there's still something there.

The Marshall factory tour is awesome! Their museum has some great stuff in it. I went a few weeks back. I would strongly recommend getting someone else to service it though... There's some great techs who know these like the back of their hand!

Image: https://scontent-lht6-1.xx.fbcdn.net/v/t1.0-9/18056969_789356944571945_58444021493280008_n.jpg?oh=1768add02b2cf3554095a9c16c3bd23d&oe=59AFBFF1

fastonebaz · May 2017

As far as I've owned it all I've had done is have the tubes changed (by a local non Marshall tech) and that's it. Think maybe i ought to take to take the back off yup see what it looks like in there.

fastonebaz · May 2017

jkirk170493 said:

They're great. Americans go crazy for them! We've had a couple of them in the past and never struggled to sell them. In fact we were tempted to keep one as 'our' amplifier! You've got a beauty - don't let it go cheap if you do decide to sell it!

What do you think it's value is for an excellent condition one? I will take some pics tmrw i think.

ICBM · May 2017

fastonebaz said:

As far as I've owned it all I've had done is have the tubes changed (by a local non Marshall tech) and that's it. Think maybe i ought to take to take the back off yup see what it looks like in there.

I hope they all needed changing and you didn't just let a tech replace a set of original Mullards with a load of modern crap for no good reason...

Sadly very common

.

Generally the old preamp valves in particular last decades, there's usually no need to change any of them. If anything, on an amp that's had fairly light use it's more likely that the filter caps will need changing than the valves.

DJH83004 · May 2017

I think you would agree IC it is good practice to always offer all of the components replaced back to the customer, for future provenance and to prove you have done the work, even if they stay in their little plastic bag

ICBM · May 2017

DJH83004 said:

I think you would agree IC it is good practice to always offer all of the components replaced back to the customer, for future provenance and to prove you have done the work, even if they stay in their little plastic bag

Hmmmm… not sure about that. Unless it's really necessary for proving a date - ie if you've removed *all* the components with date codes and there's no other conclusive proof - then I tend to think not. If components need to be replaced it's because they're scrap, and they belong in the bin.

Keeping the old parts panders to the idea that original parts are somehow more valuable than ones that are working properly, and also leaves open the possibility that some twit will put them back, or sell them to someone who wants to make his old amp 'original'.

Giving them back the old parts as 'proof' of what you've done is meaningless too - they could have come from anywhere. A car mechanic screwed me like that once… I was suspicious enough to take it somewhere else, who confirmed that the 'original' part had not come off my car because the actual original part was still place and had been bodged to 'fix' it...

So I never normally return old parts unless specifically asked to, and even then I'm grumpy about it

.

I am also well aware of other techs who keep valuable old valves from amps when 'replacing all the valves because they're old' too. If someone does ask for a full revalve and doesn't want the old ones I will offer a discount from the work for them.

DJH83004 · May 2017

Fair point IC, I am thinking more about the vintage gear, where collectors want the original caps, Bulgin sockets, valves etc. for provenance. When I am changing parts on modern amps e.g. output / mains transformers, I do offer them to customers, but more often than not they go in the bin. So I guess its customer driven,
I suppose the other issue is an amps intended purpose, a worn old set of Mullards maybe fine for a collector, but I wouldn't put my reputation on it for a gigging musician - worn valves are worn valves, choose how good they may have once been. The problem is we are only as good as our last job, and one post on a forum can trash your reputation, so I tend to err on the side of caution.

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Marshall 100w jmp super p.a. 1969 4 inputs

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