Any JMP-1 users here that could help me out? (FX loop levels at serial setting tone suck)

maxdown

20 years back I used a rack containing a JMP-1 - an FX unit (Boss GP700 I think) and a Mesa 50/50 into 2  Marshall 1912 1x12s with stock Celestion speakers (G12B-150).

I gave up playing for about 15 years and recently in the last couple of years the old band has decided to get together and gig again (special prize will go to first one of us to have a coronary on stage).

I decided to try the modelling route and have all the stuff - AxeFX, Matrix SS amp, FRFR cabs etc etc ....... great stuff and all that except for the pokey gigs where my ass is parked next to my backline - just doesn't cut it with the drummer's cymbals practically touching my cabs - and turning up the volume just gives me tweeter squeal and all that crap. I think FRFR would be fine if we played more larger rooms with a decent stage monitoring system - but we are probably only going to be playing those venues 5 or 6 times a year ...... the rest will be smaller pub/club stuff.

So ...... I decided to pull out the old 'conventional' rack from storage and fire it up with view to perhaps incorporating the AxeFX into it as more an FX unit (with backup possibility to act as both preamp and FX) or just use another rack FX unit I have. I'd hoped to do nothing to it as it worked very well for me back in the day.

All was not good .... so cutting a long story short .... I had to replace the speakers in the cabs then the JMP-1 died

So - sent the JMP-1 off to Marshall for repair and got it back with apparently clean bill of health. The only problem being that they had wiped all my old presets and MIDI mappings etc.

I tried setting up a few new presets but my rig just sounded thin and quiet  ........ so I blamed the Mesa 50/50 and dropped the whole rack off to a local amp repair guy.  He called me a couple of weeks later and said the Mesa was actually fine (he also added a bias trim pot to it and warmed it up a bit because he reckoned the cold biasing that Mesa use is a load of pants .... not that I asked him to!).

He reckoned it was probably the old Boss FX unit - which I had wired into the JMP-1 loop that was thinning the sound. He bypassed it and sent the JMP-1 direct to the Mesa and rattled his windows.

No problem I suspected that 20 year old Boss unit was probably about to keel over so I already had a G Major 2 to replace it with ..... so basically my old rig has had everything more or less replaced or modified!

But with the G Major in the loop  it's still thin sounding ....... I've set up all levels ok etc.

I'm wondering now if there's something up with the FX loop in the JMP-1. I can't remember what my FX level settings were in my old patches - but as I used mod effects like chorus I'd assume I'd have set up each patch to have a effects level of '12' - which should be 'serial' operation - IE all signal goes out of the FX send - no dry signal in parallel.

I tried using just a patch cable between the send and return L on the JMP-1 loop and monitored the signal as I gradually swept through the Effects level dial ...... it was thin tone from 1 though 5 - good strong at 6 - then it thinned out again as I moved to 12 (but I'd have thought 12 should be 'fully serial' and therefore not thin).

Does anyone else's JMP-1 fx loop do this same thing? IE Tone/signal suck at '12' in Effects level? I'm wondering if Marshall missed a problem in there with it when they were servicing it.

I'd rather use the loop in the JMP-1 than sending main outs to the FX unit ..... although I suppose seeing I also have an AxeFX it would maybe serve well in a 4CM setup with the JMP-1 and act as a modeller backup direct to the power amp if required ... although using a quick 4CM set up test it sounded noisy/muffled listening just via the AF2's headphones - I wasn't using 'humbuster' cables though which might make a difference.

Sorry about long post .... but that's the whole history.

Danny1969

The easiest  way to get a serial loop is to put the effects unit between the output of the JMP1 and the input of the power amp and set the effects to line level 
Will that not work for you ?

stratman3142

I'm not sure if this is much help but I used to have a JMP1 with a G major in the loop. I set things up so the effects level of the JMP1 wasn't at maximum. I think I sent about half the signal to the G major. So, if the max is 12, I probably set the JMP1 to be around 6 in the Fx loop. The reason I did this was the minimise the effect that the G major had on the sound.

Having done that I made sure that the G major was set up to be 100% wet (i.e. no dry signal whatsoever). Otherwise, if any of the dry signal gets through the G major there's a (so called pipeline delay) that will mix with the dry signal of the JMP1 and give phase cancellation type effects (which thins the sound).

Unfortunately I no longer have the units so all I can do is try to remember what I did.

 

maxdown

Danny1969 said:

The easiest  way to get a serial loop is to put the effects unit between the output of the JMP1 and the input of the power amp and set the effects to line level 
Will that not work for you ?

Yes - it will work but it defeats the emulated outs on the JMP-1 (no FX just dry output). Not that the emulated outs are 'quality' but they did get me out of a hole quite a bit when there were no mics for my cabs and I needed to bleed a bit of guitar into FOH.

The other issue would be volume control on stage ..... with the FX in the loop the send levels are set per preset Vol/Gain settings - so I volume match all presets and make sure my loudest ones don't clip the FX unit. I then can alter my stage volume using the front level control on the JMP-1 (master out vol) without blasting additional signal at the FX unit and clipping it. (No matter how suitably loud I think I am at soundcheck - by the second set I'll have turned up louder on stage )

maxdown

stratman3142 said:

I'm not sure if this is much help but I used to have a JMP1 with a G major in the loop. I set things up so the effects level of the JMP1 wasn't at maximum. I think I sent about half the signal to the G major. So, if the max is 12, I probably set the JMP1 to be around 6 in the Fx loop. The reason I did this was the minimise the effect that the G major had on the sound.

Having done that I made sure that the G major was set up to be 100% wet (i.e. no dry signal whatsoever). Otherwise, if any of the dry signal gets through the G major there's a (so called pipeline delay) that will mix with the dry signal of the JMP1 and give phase cancellation type effects (which thins the sound).

Unfortunately I no longer have the units so all I can do is try to remember what I did.

 

Yes ... that would be my current findings ..... at '6' in the FX settings the tone in the loop seems unaltered.

I did try setting the G Major to 'Kill Dry' in the globals when the JMP-1 loop was at '6' .... but while delays and reverb do well in parallel it doesn't sound brilliant with modulated FX as there's still a strong uncontrollable dry signal passing to the main outs at JMP-1 level.

From hunting the net I see there's a mod that can be done on the JMP-1 to turn it's loop into a more conventional serial only one ... a couple of resistors need removed from the loop circuit ...... so seeing as thats reversible without too much hassle if it doesn't help it might be worth trying.

stratman3142

maxdown said:

stratman3142 said:

I'm not sure if this is much help but I used to have a JMP1 with a G major in the loop. I set things up so the effects level of the JMP1 wasn't at maximum. I think I sent about half the signal to the G major. So, if the max is 12, I probably set the JMP1 to be around 6 in the Fx loop. The reason I did this was the minimise the effect that the G major had on the sound.

Having done that I made sure that the G major was set up to be 100% wet (i.e. no dry signal whatsoever). Otherwise, if any of the dry signal gets through the G major there's a (so called pipeline delay) that will mix with the dry signal of the JMP1 and give phase cancellation type effects (which thins the sound).

Unfortunately I no longer have the units so all I can do is try to remember what I did.

 

Yes ... that would be my current findings ..... at '6' in the FX settings the tone in the loop seems unaltered.

I did try setting the G Major to 'Kill Dry' in the globals when the JMP-1 loop was at '6' .... but while delays and reverb do well in parallel it doesn't sound brilliant with modulated FX as there's still a strong uncontrollable dry signal passing to the main outs at JMP-1 level.

From hunting the net I see there's a mod that can be done on the JMP-1 to turn it's loop into a more conventional serial only one ... a couple of resistors need removed from the loop circuit ...... so seeing as thats reversible without too much hassle if it doesn't help it might be worth trying.

If I recall correctly, I did manage to kill the dry signal in the G major with the modulated sounds. I think part of how I achieved what I wanted involved setting up a parallel routing within the G major, where all the effects (i.e. Pitch, Cho/Fla, Delay and Reverb ) were in parallel with each other and run at 100% wet.

Because there's a dry signal path in the JMP 1 Fx loop (when it's not on maximum), the 100% wet modulation within the G major will mix with that dry signal to still give the modulation effect.

thecolourbox

Sorry to hijack, but I have a Marshall jmp1 that hums quite badly, would you be able to message me how you sent yours off to Marshall to be fixed and how much they charge? I don't like mine so want to flog it but can't do that if it's not working optimally. Thanks!

gibsongretschfan

Like others have said I wouldn't use the effects loops if I were you.... in fact I once was you and didn't use it. 

maxdown

thecolourbox said:

Sorry to hijack, but I have a Marshall jmp1 that hums quite badly, would you be able to message me how you sent yours off to Marshall to be fixed and how much they charge? I don't like mine so want to flog it but can't do that if it's not working optimally. Thanks!

Bear in mind that the JMP-1 is quite noisy by default - mine has a hum too - but only from inside the casing - not from the speakers when playing...... a fair amount of hiss though with gainer presets. Likely the Power Transformer is the hummer.

If you want Marshall to inspect and service the unit you call them at their Bletchley HQ - 01908 375411 and they'll give you a Repair Reference Number - you then send the unit to them with the Ref No clearly visible and they then will get the tech to inspect and they'll contact you with a quote to repair - or to return if you think its too expensive.

Mine had a couple of ICs blown and they also replaced the 2 front input sockets (Instrument in and Headphones) and checked everything else - it was a while ago now - but I think it was around £70 all in.

The Power Transformer is probably the single most expensive part in the JMP-1 - I see them at £223 online http://www.mercurymagnetics.com/pages/catalog/manufacturers/MM_marshall.htm - so if it needs replaced and labour costs added ..... I'd be 'humming' myself on whether to proceed unless it was going to be a keeper. If I wanted shot of it I'd maybe sell it as in need of some repair 

maxdown

They are not quiet by nature and do hum a bit listening to the actual unit operating without playing - the power transformer I suspect - but you shouldn't hear any significant hum through the speakers when playing. It's recommended you try and keep the 'Vol' of the gainy OD1 and OD2 based presets no higher than 12 to keep the noise as low as possible - I don't and it works fine though .... once it's in a band mix on stage you'd never notice the hiss.

The much lauded higher end 'Voodoo' mod replaces the PT with a 'quieter/better' one (but they also build in a noise suppression circuit too because its just a fairly noisy amp by default).

If you think yours is definitely in need of repair and you want to get a quote from Marshall then you just call Marshall (Bletchley Head Office - 01908 375411)  and they'll take your details and give you a repair ref number - then you sent the unit to them with the repair ref clearly visible and they'll contact you with a quote for repair or quote for return postage if you decide they are too expensive.

If it is the power transformer then that would probably be the most expensive element to replace in the JMP-1 - I see they are around 225 quid online http://www.mercurymagnetics.com/pages/catalog/manufacturers/MM_marshall.htm ..... so seeing the entire JMP-1 is probably only worth around that used these days it might be only worth paying if it's going to be a keeper for you - otherwise personally I'd probably flog it with the issue clearly stated and let someone else in the know restore it.

Mine had some blown ICs and they charged me £70 all in I think ..... but they did replace the 2 front input sockets (In and Headphones) as well because the washer nut was missing off one of them.

maxdown

umm ... no idea why one of those posts didn't appear first time I submitted it ... so I re-did it .... now both appear .... oops

siraxeman

Danny1969 said:

The easiest  way to get a serial loop is to put the effects unit between the output of the JMP1 and the input of the power amp and set the effects to line level 
Will that not work for you ?

That's how mines set up....sounds fine to me.

maxdown

yep ... I'm not contesting the fact that it works that way but I'm just trying to nail down the best way to use the loop and get the advantage of being able to control stage volume from the JMP-1 front level knob without adding any signal gain to the FX unit. I prefer to set and forget the power amp input attenuators and let the preamp be the volume controller.

stratman3142

Did you try setting up the G major in a parallel routing configuration (all effects 100% wet) and killing the dry signal, as I described earlier, with the JMP1 Fx loop mix setting at about 06 (i.e. ~50%). That's the way I used mine live for years.

You can then tweak the level controls on the G major to vary the amount of effect on the fly. Sometimes, in a very live room, I'd back off the reverb and delay in that way (although the compromise was that it also reduced the level of modulation when I used that effect).

maxdown

Yes .... that seems to be the best way to do it ....... I assume it's that '6' level that I used previously with the old Boss unit too before Marshall wiped my settings. I'd not even turned the rig on in about 15 years so I really couldn't remember 

Just seemed odd that at level '12' the JMP-1 signal from the FX loop send sounded so crap even just using a patch cable between send and return L in the loop. Def some phase issues going on there it seems

firepaulmusic

I used a JMP-1 for years and always had to set the FX loop level to 12 to get it to work properly. The unit sounds fab with the FX loop at 0 and nasal at most settings between. At 12 it always seemed to work how a normal FX loop would but, yes, the level drops but that can be compensated at the amp or desk.

maxdown

Hmmm..... mine sounds really weak at 12 in both level and tone ...... could be a fault that Marshall missed when it was being serviced.

I might get the amp repair guy I use to do the 'serial loop' mod by removing and bridging the R167/R169 resistors to see if it does anything interesting. Within the G Major I could still internally configure the parallel route for delays but keep serial for other stuff before returning to the JMP-1 loop and main outs if I wanted.

I'm not sure I'm loving the G Major 2 much ...... I like the look of a Digitech GSP1101 as a 1U replacement option if I can track one down somewhere.

Using the AxeFX would mean upsizing to a bigger rack - a GSP1101 would give me some preamp backup options too if the JMP-1 decided to die at a gig.

FX_Munkee

Can't help with your loop issue (My old Pre-Amp was a Hafler T2, that's going back a bit...)
But I can recommend the GSP1101, it's really surprisingly good. Especially hooked up in 4CM.
Keep an eye on ebay and weirdly Amazon just sold some off at £130 so maybe keep checking them as well.

thecolourbox

FX_Munkee said:

Can't help with your loop issue (My old Pre-Amp was a Hafler T2, that's going back a bit...)
But I can recommend the GSP1101, it's really surprisingly good. Especially hooked up in 4CM.
Keep an eye on ebay and weirdly Amazon just sold some off at £130 so maybe keep checking them as well.

I bought one at £130 from amazon warehouse, seems alright

Danny1969

I use a GT10 in the loop with mine, as stratman3142 said set your wet \ dry to 100% wet, then you won't get the hollow sound caused by the slight latency in the AD \ DA convertors round trip  in the effects unit

I've replaced the volume pot on my and redone some joints, along with the valves. It's actually pretty easy to work on despite the complexity 

gibsongretschfan

You could always get a Tc Nova System. It has a cab sim built in and you could use it as a floor board for switching your JMP-1 via midi too